Electroslag Welding Facts for Structural Engineers

August 2015

Electroslag Welding Facts for Structural Engineers By Janice J. Chambers, PhD, SE Associate Professor Department of Civil and Environmental Engineering University of Utah And Ronald D. Medlock VP Technical Services High Steel Structures, LLC

____________________________________________________________________________ (A copy of this report can be downloaded for personal use from www.steeltips.org)

Electroslag Welding Facts for Structural Engineers By Janice J. Chambers and Ronald D. Medlock

Abstract A synopsis of the basic mechanics of the electroslag welding process of joining structural steel elements is presented. This is followed by the historical progression of electroslag welding (ESW), from 1888 to modern time. The US Federal Highway Administration's suspension of ESW in the late 1970s is highlighted. Results of research, sponsored by the US Federal Highway Administration, is discussed. The most significant result was the introduction of Narrowgap Improved Electroslag Welding (NGI-ESW, ESW-NG). Shop and field applications of electroslag welding are presented.

First Printing, August 2015. __________________________________________________________________________________ Janice J. Chambers Associate Professor Department of Civil & Environmental Engineering University of Utah 110 Central Campus Drive, Suite 2000 Salt Lake City, UT 84112 [email protected]

__________________________________________________________________________________ Ronald D. Medlock VP Technical Services High Steel Structures, LLC 1915 Old Philadelphia Pike Lancaster, PA 17602 [email protected]

Disclaimer: The information presented in this publication has been prepared in accordance with recognized engineering principles and is for general information only. While it is believed to be accurate, this information should not be used or relied upon for any specific application without competent professional examination and verification of its accuracy, suitability, and applicability by a licensed professional engineer, designer or architect. The publication of the material contained herein is not intended as a representation or warranty on the part of the Structural Steel Educational Council or of any other person named herein, that this information is suitable for any general or particular use or of freedom from infringement of any patent or patents. Anyone making use of this information assumes all liability arising from such use. Caution must be exercised when relying upon specifications and codes developed by others and incorporated by reference herein since such material may be modified or amended from time to time subsequent to the printing of this document. The Structural Steel Educational Council or the authors bear no responsibility for such material other than to refer to it and incorporate it by reference at the time of the initial publication of this document.

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ACKNOWLEDGMENTS The authors wish to thank the Structural Steel Education Council (SSEC) for accepting this topic for a Steel Tips and for their careful review and thoughtful comments. Review services were also provided by Heather Gilmer, Florida Structural Steel and David McQuaid, DLMcQuaid & Associates. William (Bill) Bong, President of Arcmatic® Welding Solutions is gratefully acknowledged for providing the authors with a wealth of documentation related to ESW-NG. Both Brett Manning, Director of the Structural Steel Education Council and VP of Northwest Sales, Schuff Steel and Bill Bong demonstrated patience, attention, and kindness when responding to the authors' numerous queries; and for their unflagging support. Much appreciation goes to Mark Sapp welding historian of New Bern, North Carolina, for gifting the first author with a hard copy of the out-of-print book on the O.E. Paton institute's research. Thanks also to Don Chambers for his editing and proofing assistance. Finally, the authors wish to acknowledge the structural engineers who have been amenable to reviewing and accepting ESW welding over the past three decades. Without them this welding process would not be available today.

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ELECTROSLAG WELDING FACTS FOR STRUCTURAL ENGINEERS By: JANICE J. CHAMBERS, PH.D., S.E. Associate Professor University of Utah

RONALD D. MEDLOCK VP Technical Sales High Steel Structures, LLC

______________________________________________ TABLE OF CONTENTS ABSTRACT / Page 1 ACKNOWLEDGMENTS / Page 2 CHAPTER 1. INTRODUCTION / Page 4 CHAPTER 2. ELECTROSLAG WELDING FUNDAMENTALS / Page 5 CHAPTER 3. HISTORICAL DEVELOPMENT OF ELECTROSLAG WELDING / Page 13 CHAPTER 4. NARROW-GAP IMPROVED ELECTROSLAG WELDING (NGI-ESW, ESW-NG) / Page 18 CHAPTER 5. ELECTROSLAG T-JOINT SHOP-WELDING / Page 27 CHAPTER 6. ELECTROSLAG WELDING IN THE FIELD / Page 32 CHAPTER 7. CONCLUSION / Page 39 REFERENCES / Page 40 ABOUT THE AUTHORS / Page 42 LIST OF PUBLISHED “STEEL TIPS” REPORTS / Page 43 ____________________________________________________________________________________ Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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1. Introduction Comparing all welding methods, electroslag welding (ESW) is the most economical to reliably weld thick joints [from about 1 in. (25 mm) to 6 in. (150 mm)]. It is therefore prudent that persons involved in the design, fabrication, or erection of steel structures possess general knowledge of electroslag welding. The objective of this Steel Tips is to provide this knowledge. In order to orient the reader, the first substantive chapter of this Steel Tips, Chapter 2, provides a description of the necessary ingredients, instrumentation, and process to manufacture an electroslag weld. After the basics are given, the historical development and use of ESW are presented in Chapter 3. Chapter 3 includes a discussion of a 1976 ESW fabrication error and the consequent moratorium on ESW for bridge construction in the United States. The moratorium precipitated a surge in ESW research that ultimately introduced electroslag welding - narrow gap (ESW-NG). The AASHTO/AWS D1.5M/D1.5 Bridge Welding Code permits the use of ESWNG to weld members or member components made from common types of bridge steels (American Association of State Highway and Transportation Officials 2010). A description of ESWNG, including the Bridge Welding Code's specifications and recommendations, are the subject of Chapter 4. The remaining substantive chapters describe shop (Chapter 5) and field (Chapter 6) applications of electroslag welding.

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2. Electroslag Welding Fundamentals 2.1 Electroslag Joints Electroslag welding (ESW) is a process used in the fabrication of steel structures. In particular, ESW provides an economical means to join steel of about 1 in. (25 mm) to 6 in. (150 mm) in thickness. The metal to be joined is often referred to as the base metal. The welding process utilizes the force of gravity and progresses from bottom to top. The process should be performed at an angle between zero (vertical) and about 45 degrees (Figure 1a).1 (Successful ESW welds have also been made at an angle of 50 degrees.) From Figure 1 it can be deduced that the preparation of a joint for ESW requires a sump at the bottom of the joint, run-off tabs at its top (Figure 1b), side containment (Figure 1c), and sealant. An electroslag weld cavity is the space created by a gap between the base metal and two welding shoes at each end of the gap. The sump and run-off tabs promote homogeneity over the entire length of the joint. Side containment components are commonly referred to as welding shoes. Figure 1 presents butt joints. Plates aligned at an angle (i.e., T and corner joints) and/or plates of different thickness can also be joined using electroslag welding, but the shape of the welding shoes must be such that they can fit snuggly against the sides of the parts joined. A common T-joint consists of the edge of a stiffener plate and the flange of a W-shape. (Stiffener plate welding shoes are also discussed in section 5.2 of this Steel Tips.) Welding shoes are constructed of copper, which has very high thermal conductivity. They are hollow to allow a coolant, typically water, to circulate through them. The cool welding shoes and the thin slag layer that forms between the shoes and molten steel during the welding process prevent the shoes from fusing to the base metal. < 45

Run-off tabs

o

Hose receptacles

Sump a. Base metal.

b. Sump and run-off tabs.

c. Side containment.

Figure 1: Plate Joint and Partial Electroslag Welding Instrumentation 1The

ESW welding process may be applied in the field. Moreover, an otherwise horizontal joint could be fabricated at 45 degrees from the vertical to accommodate an ESW field weld (refer to section 6.4 of this Steel Tips). Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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The electroslag welding process is aptly named since it employs an electrode immersed in a slag pool (Figures 2 and 3). The commencement of the electroslag welding process requires an arc applied through pre-deposited flux (Figures 2a and 2b). A slag pool is soon formed that extinguishes the arc (Figure 2c). Electroslag welding is unique from other welding methods in that after a brief initial electric arc is extinguished, heat generated from electric current, rather than an electric arc, is used to perform resistance welding. The electric current travels from an electrode ("wire," "filler metal") to the base metal. The slag pool's resistance to the electric current transforms the electric energy into thermal energy (heat). At a temperature of approximately 3500 degrees F, the slag pool is hot enough to sustain continuous melting of the base metal and wire. The force generated by wire feeding into the joint and the force of gravity transfers melted metal droplets downward through the lighter slag pool to the heavier weld pool. The solidified weld pool forms the weld. Figure 3 presents a cross-section of an electroslag weld during its fabrication. The wire must be guided into the weld cavity and not touch the base metal or welding shoes, causing an electric short-circuit. Therefore, it is encased in a guide. Consumable metal guides are much easier to use and quickly replaced non-consumable guides during the evolution of ESW. Early guides were round and were hence referred to as "guide tubes". Later, winged and webbed flat guides were introduced (Figure 4). However, the name "guide tube" is often used today for all types of wire guides. As the slag pool rises, it melts (consumes) the stationary consumable guide. Wire feed rate is synchronized with guide consumption such that wire is always submersed in the slag pool. Depending on the thickness of the base metal, single or multiple wires encased in a fixed or an oscillating guide have been used. Multi-pass electroslag welds can also be made. Each pass is vertical and extends the full height of the weld cavity (Bong 2012). Multi-pass ESW welds have been successfully used to join very thick (greater than 4 in.) plates. Wire is fed into a slag pool maintained at a uniform depth of about 1 inch (25 mm), which is a requirement for sustaining the slag pool's necessary temperature to melt the welding consumables and fuse the joint. If a slag pool is too deep, incomplete fusion, a "cold lap", will form in the joint. 2.2 Electroslag Weld Grain Structure, Electric Variables, and Weld Parameters Grain structures in solidified ESW welds are indicative of their toughness, which is commonly measured by Charpy V-notch tests ("Charpy tests"). Acceptable Charpy test values are usually established by applicable welding codes and depend on the structural components welded, and the geographical location and importance of the structure that contains ESW welds.

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Guide

Flux

Wire

Electric arc

a. Guide inserted into weld cavity.

Electric current

b. Wire inserted into guide and electric arc fired.

Molten slag pool

c. Electric arc melts flux and is extinguished by molten pool.

Figure 2: Commencement of Electroslag Welding Process

Wire Guide

Slag pool Weld droplets

Submerged guide and wire Unsubmerged/submerged wire Submerged wire

Weld pool Weld

Figure 3: Cross-section of Electroslag Welding Process Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Wire

a. Round

b. Winged

c. Webbed

Figure 4: Example Schematics of Cross-sections of Electroslag Welding Wire Guides

HAZ: f ine gra ins

grains HAZ: c oarse

Coarse Colum nar Grains (Z one D)

Equiaxed Grains (Zone EG)

Coarse Columnar Grains (Zone D)

HAZ: coarse grains

HAZ: fine grains

Along the cross-section of an ESW weld there are several grain structure zones (Figure 5). The outer extremity of the heat affected zone (HAZ) consists of fine grains, and its inner portion contains a coarse-grained structure that forms when temperatures well above those needed for austenite transformation exists for a relatively long time. Within the weld itself, two or three zones may exist. A coarse-columnar grain (CCG) structure exists in the outer zone of the weld, Zone D. As its name implies these grains are elongated. This type of grain structure is known to possess high toughness and strength. The inclusion of nickel and molybdenum alloys in the cored wire promotes an equiaxed grain structure (Zone EG) at the center of the weld. Large amounts of acicular ferrite, associated with high toughness and strength, are included in Zones D and EG. Between zones D and EG is a zone of fine-columnar grain structure (FCG) consisting of a proeutectoid ferrite of lower toughness than Zones D and EG, but exhibits good resistance to hot cracking (Federal Highway Administration 1996).

Weld

Figure 5: Cross-section of an Electroslag Weld Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Critical ESW parameters include cooling rate, amount of base metal dilution ("dilution"), and the weld pool form factor ("form factor"). The effects of an increase in electric voltage, electric current, and welding speed on these parameters are presented in Figure 6. The desired effect on a parameter, an increase or decrease, is shown using arrows. The actual effect of an increase in an variable is also shown. When the actual effect is opposite to the desired effect, a red arrow is shown, and when a green arrow is shown the actual effect is a desirable effect. Figure 6 is further explained in the remaining paragraphs of this section. Tough microstructures are developed when the cooling rate of an ESW weld is high. Heat transfer can be quantified by the Adams cooling rate equation, R:

R

2 k Tc To fH

(2.1)

where k=thermal conductivity of the metal; Tc=initial base metal temperature; To=temperature at which the cooling rate is calculated; f=heat transfer efficiency of the source; and H=heat input, the amount of energy generated per length (e.g., in.) of weld, is further defined as EI V

H

(2.2)

where E= electric potential (voltage), I= electric current (amperage), and V=welding velocity (i.e., rate of wire feed). 1

ESW Parameter Variable

Cooling Rate

Dilution

Form Factor

Effect Actual

Desired Actual

Desired

Actual

Desired

Voltage Current Speed Figure 6: Effect of Variables on ESW Parameters 1

Electric potential is also known as electrical potential or voltage because the unit of electric potential is volts. Electric potential is electric potential energy per unit of charge moved (coulomb). The unit of electric current is coulomb per second or ampere. Like electric potential, electric current is often referred to by its units, amperage or amps. Electric potential (voltage) times electric current (amperage) is electric power, which is measured in watts.

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Substituting (2.2) into (2.1):

R

2V k Tc To fEI

(2.3)

Thus, the cooling rate equation is directly proportional to the welding velocity and inversely proportional to voltage and current. Examination of (2.3) indicates that the higher the voltage (E), the slower the cooling rate, which is undesirable. However, fusion may be inadequate if the voltage is too low. The required voltage depends on the root opening (gap), thickness of the joint, diameter and number of welding wires, guide, and welding equipment. Conventional electroslag welding, which includes a 1.25 in. (32 mm) gap, requires about 41 volts. Welding narrower gaps of approximately 7/8 in. (22 mm) requires 28-37 volts. (Also refer to Chapter 4, Table 1.) Dilution, the percent of base metal in the weld metal, is also indicative of tough welds. Generally, the lower the dilution, the greater the weld toughness. On the other hand, insufficient dilution is associated with incomplete fusion. Dilution of sound conventional electroslag welds for 2inch (50 mm) plates is about 40%. As voltage is increased, the weld metal becomes more diluted with the base metal. Increasing the welding speed reduces base metal dilution. Figure 6 indicates that the effect of electric current on dilution is inconclusive. However, dilution increases with increasing current up to a maximum value and then decreases with further increases in current. The magnitude of the current where a reduction in dilution is realized is a function of the voltage and electrode (wire) guide geometry (Federal Highway Administration 1996). During electroslag welding, velocity (V) and electric current (I) are interdependent. As the electric current increases during the welding process, the wire feed rate accelerates. When the acceleration exceeds the rate of the increase in the electric current, the cooling rate increases. Therefore, the cooling rate of electroslag welding must be a differential (dynamic) equation and Adam's cooling rate equation can only be conceptually applied to electroslag welding. The geometry of the weld pool is quantified by its form factor ff (Figure 7): ff

W d

(2.4)

where W= average weld pool width, and d= depth of the weld pool. The form factor may indicate how likely the weld pool is susceptible to cracking during solidification. Wide, shallow weld pools have lower susceptibility to solidification cracking. High form factors of 2-3 have demonstrated good resistance to cracking. Form factors depend predominantly on current, welding velocity, and voltage. Increasing voltage increases the form factor. The electric current and welding velocity are inversely proportional to the form factor (Federal Highway Administration 1996, Paton 1962). The cooling rate is directly proportional to welding velocity and inversely proportional to voltage and current. Therefore, research is needed to derive an accurate mathematical formula to describe the relationship between electroslag welding's form factor and its cooling rate. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Weld pool

d

Figure 7: Electroslag Weld Form Factor Parameters

2.3 Electroslag Welding Wires Solid and alloy-cored wires have been used in electroslag welding. Solid wires take longer to transform from a solid to a liquid. This creates a hotter and deeper weld pool. Alloy-cored electrodes are well suited to electroslag welding. The inclusion of nickel and molybdenum in the core enhances the toughness of a weld. Flux-cored wires cannot be used during this process because the flux will create a deeper and deeper slag pool (i.e., smaller and smaller form factor) as the weld progresses. 2.4 Electroslag Welding Power Supplies While drooper1 power supplies have been traditionally used for arc welding applications, they proved very unsatisfactory for ESW welding. During arc welding, the arc load controls the electric potential (voltage) to maintain the power generation of a drooper power supply. The electric resistance is relatively constant, which facilitates maintenance of the supply of a constant electric current. This is not true of the electroslag welding process. The resistance to the flow of electricity is not constant. Moreover there are local and global electric resistance variations. As the weld rises locally, the slag pool consumes the bottom portion of the guide. This consumption increases the electric resistance and the power supply must raise its amperage (current) to satisfy the power demand. When the submerged portion of the guide has been consumed, a small gap is formed between the bottom of the guide and the top of the slag pool, which reduces the electric resistance. The power supply must react by decreasing its amperage. Similarly, as the wire feed accelerates, the power supply's current must increase. Thus, locally there are increases and decreases in resistance. In the global sense, there is a continual reduction in electric resistance. As the welding process progresses, the distance between the weld pool and the weld 1

The term "drooper" was adopted for these power supplies because they utilize downward-sloping amperage vs voltage output

curves. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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head decreases, which reduces the electric resistance. A gradual reduction in the voltage supplied usually accommodates this global reduction in electric resistance. Constant-potential (CP) power supplies with variable balance (VB) control that quickly restores the supply-demand balance of power are well suited to electroslag welding. These power supplies also mitigate the formation of a strong magnetic field that erratically pulls the molten weld puddle and/or guide during the welding process.1 Traditional sine wave power generation also proved unsuitable for electroslag welding. The initial arc needed to commence the electroslag welding process was often extinguished using AC power. The introduction of square wave power generation eliminated this problem while also contributing to the mitigation of a strong magnetic field during the welding process. Thus, VB/CP/AC square wave power supplies are ideal for electroslag welding applications. These include SCR (silicon-controlled rectifier) power supplies, IGBT (insulated-gate bipolar transistor) power supplies, and DC power supplies connected "Electrode Positive" (DCEP), also referred to as DC Reverse Polarity, and connected "Electrode Negative" (DCEN), also referred to as DC Straight Polarity (Bong 2014a).

1 In submerged arc welding (SAW) this is often referred to as "arc-wander" or "arc-blow".

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3. Historical Development of Electroslag Welding 3.1 Early Electroslag Joints Electroslag welding was a response to the unreliable and time-consuming application of conventional arc welding to join thick [from about 1 in. (25 mm) to 6 in. (150 mm)] metal machine/equipment (e.g., pressure vessels) parts and metal plates used to construct naval vessels. Defects typically associated with a weld pass, such as slag inclusion and porosity, are very atypical to electroslag welds. To this day, ESW manufactures thick vertical welds much more efficiently than traditional multi-pass arc welding processes such as flux-cored arc welding (FCAW) and gas metal arc welding (GMAW). The first US patent that resembles modern ESW, "Working Metals by Electricity," was issued late in the 19th century to a Russian inventor (Benardos 1888) (Figure 8). Scrap metal was used as the filler metal. Two adjustable "side dams" contained the molten weld. During the entire process, an electric arc melted the scrap metal and fused it to the parts. Thus, fusion was not achieved with electric current as it is with electroslag welding. Later, in 1940 a US Patent, "Method for Manufacturing Composite Metal Articles," was issued to Robert Hopkins of MW Kellogg Co., New York, NY, which bears a greater resemblance to contemporary electroslag welding (Hopkins 1940) (Figure 9). This patent claims the use of a water-cooled copper mold to form a cavity of 1.5 inch (38 mm) minimum width, where a coating (Figure 9, item 52) in its molten state is deposited beneath a blanket of flux (Figure 9, item 50) via electrode(s) and electric current. The mold claimed is solid (Figure 9, item 13) and cooled via water sprays (Figure 9, item 16). The foundation of modern electroslag welding was laid by Russia's Paton Institute. In 1934 the Ukrainian SSR Academy of Sciences Welding Institute was established in Kiev, Ukraine. In 1991 it was renamed the E.O. Paton Welding Institute after its founder Evgeny Paton. The institute was later directed by his son, Boris Paton1. The electroslag welding research conducted at the institute up to 1959 was published and translated into English in 1962 in the book Electroslag Welding (Paton 1962). Later, Electroslag Welding and Surfacing, was published by the institute (Paton 1983). Widespread application of electroslag welding in the US began in 1959 by the Electro-Motive Company (now Electro-Motive Diesel, a division of Caterpillar, Inc.). The Electro-Motive Company used ESW in the construction of locomotive traction motor parts.

1Born

in 1918, Boris Paton remains the long-term leader of the National Academy of Sciences of Ukraine at the time of this writing. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Figure 9: Early Electroslag Welding for Coating Applications (from Hopkins 1940)

Figure 8: Early Thick Plate Welding (from Benardos 1888)

3.2 Revolutionary Developments in Electroslag Welding The Linde Division of Union Carbide (Linde)1 and the Hobart Brothers Company (Hobart)2 introduced electroslag welding to the construction of large civil structures (bridges and high-rise buildings). Their issued patents focused on round guide ("guide tube") composition and their implementation in the electroslag welding process. Linde developed a fluxcoated consumable guide tube (Figure 10, items 10 and 17). The coating insulated the guide from the walls of the joint, which prevented an electric shortcircuit during the welding operation (Shrubsall 1959)3. However, using Linde's process, the guide tube's flux liquefaction was unpredictable. Therefore, the depth of the slag pool required diligent monitoring. Figure 10: Linde's Flux-coated Guide in Weld Cavity (from Shrubsall 1959)

1Linde Division of Union Carbide is currently owned by Dow Chemical. 2Hobart Brothers is currently owned by Illinois Toolworks, Inc. 3Linde's process was used to perform the first electroslag welds on a steel

building. Kaiser Steel Corporation used the process to deposit 24,000 shop welds in the Bank of America world headquarters building in San Francisco, completed in 1969 (Irving undated). Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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A single stationary wire within an ESW weld cavity could created a weld of reasonably uniform properties in joints of up to approximately 2 inches (50 mm) thick. To ensure an even deposition of weld material across thicker joints, Hobart developed a method of oscillating one or more consumable guides, which were used in their "Porta-slag Welding" (Hannahs 1970, Hobart Brothers 1970). Refer to Figure 11. The consumable guides were oscillated across the thickness of the base metal, using either a linear motion with pauses at the end of each stroke, or with a sinusoidal motion. When using more than one guide, the guides could be moved toward and away from each other in order to promote an even distribution of heat and weld material. Hobart's Porta-slag welding method also incorporated insulating rings, spaced at six inch intervals along the guide, which prevented electric short-circuiting (Figure 12). An experienced welding operator added flux according to the sounds emitted from the weld pool. Flux was added when the operator heard the weld arcing. If the weld became too quiet, too much flux had been added. In this way, the optimal depth of the slag pool was maintained. Hobart's oscillating guide also provided greater uniformity in the depth of the fusion and heat affected zones than Linde's method. Czech researchers also made interesting contributions toward controlling the depth of the slag pool in electroslag welding (Mosny and Pavelka 1961, Cabelka 1962). From the 1960s to mid 1970s, electroslag welding was rapidly gaining momentum for welding thick steel joints in buildings and bridges. These included shop-welding of stiffener plates to the flanges of girders and shop-welding plate splices.

Guide Insulator

Tack weld

Figure 11: Hobart's Oscillating Guide (from Hannahs 1970)

Figure 12: Hobart's Guide and Insulators (adapted from Hobart Brothers Technical Center 1970)

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3.3 Moratorium on Electroslag Welding in Bridge Construction Early in 1976 a tugboat captain noticed a long crack (Figure 13) propagating from an electroslagwelded flange splice (Allan 1977, Fisher et al. 1980). The fracture occurred in the I-79 bridge section that connected Neville Island, PA with the south shore at Grooveton, PA across the Ohio River, west of Pittsburgh, PA. The section was immediately closed to all traffic, and soon thereafter the entire bridge was shut down until the bridge could be inspected for further damage and repaired if necessary. An in-depth examination of the bridge conducted by Lehigh University researchers and sponsored by the Federal Highway Administration (FHWA) was published (Fisher et al. 1980). Prior to the weld fracture, thousands of electroslag welds had already been used to splice girder flanges and weld stiffener plates1, and only one sample core among five samples removed from other parts of the bridge section failed to meet absorbed energy requirements. Because of the severity of the crack and resulting public outcry, the FHWA imposed a moratorium on electroslag welding for welding tension elements in bridges until the cause of the fracture could be determined. Besides the Lehigh researchers, the American Welding Society (AWS) also commissioned a Blue Ribbon Committee to investigate the failure. The Blue Ribbon Committee concluded that a substandard weld repair was the cause of the fracture. The ESW weld had been stopped and restarted, which must occur if the wire coil is exhausted during the welding process. (Fabricators strive to avoid this.) An SMAW "stick pass" was welded over the visible imperfection and ground smooth. The cosmetic mask made the electroslag weld appear sound. After the flange was put into service, the discontinuity gave birth to a crack that propagated through the bottom (tension) flange of the girder and into the web (Fisher et al. 1980 and Hannahs 2003). The Blue Ribbon Commit3.5 in. tee studied the I-79 bridge failure and other (89 mm) bridges fabricated by the same fabricator. They also studied bridges that contained electroslag welds made by other fabricators. The committee found that no other bridge containing electroslag welds had failed or was in danger of failing. stiffener 0.5 in. x 7.5 in. However, the committee did find defects caused (1.27 cm x 19.05 cm) 11 ft. by fabricator errors. For example, a bridge in (3.35 m) Pittsburgh contained massive porosity in at least Web splice one ESW weld that was never repaired and/or tw =0.5 in. noticed. As a safety precaution, this bridge was (1.27 cm) retrofitted. Upon conclusion of their investigation, the Blue Ribbon Committee endorsed the electroslag welding process of that time (Hannahs 2003). The head of the Blue Ribbon 3.5 in. Committee retired and did not prepare a final flange Electroslag (89 mm) weld report. The final report would have shown that all defects found in the electroslag weld inspectFigure 13: Crack the Precipitated ed by the Blue Ribbon committee were caused Moratorium on Electroslag Welding by fabrication errors. (adapted from Fisher et al. 1980) 1These

welds have been in service, without incident, for the past 30-40 years.

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Unfortunately, the Blue Ribbon Committee's findings were never published, and most engineers, designers, and steel fabricators in the United States became apprehensive about using electroslag welding. After imposing the moratorium, the FHWA sponsored research to develop methods to improve electroslag welding at Northwestern University and the Oregon Graduate Institute (OGI)1. This research resulted in a new method of electroslag welding, referred to as Narrow-gap Improved Electroslag Welding (NGI-ESW) (Federal Highway Administration 1996). NGI-ESW narrowed the weld cavity, increased the speed, decreased the heat-affected zone (HAZ), eliminated the need for oscillating guides, and increased the notch toughness of ESW welds. ESW-NG is now the preferred acronym for the welding method that originated with the research conducted at OGI. ESW-NG has been accepted by the American Association of State Highway and Transportation Officials/American Welding Society's Bridge Welding Code (American Association of State Highway and Transportation Officials 2010)2. A summary of the Bridge Welding Code's ESW-NG requirements is presented within the next chapter of this Steel Tips. ESW-NG may also be used for Demand Critical Welds for steel frame construction. Demand Critical Welds are sometimes required to weld base plates to columns, splices, and connections. The American Institute of Steel Construction's (AISC) Seismic Provisions requires that Demand Critical Welds satisfy the American Welding Society's (AWS) Structural Welding Code and its seismic supplement (American Institute of Steel Construction 2014 and 2010, American Welding Society 2009 and 2010). Moreover, electroslag welding is specifically cited in the commentary to the specifications for the welding of the flanges of the Bolted Flange Plate Connection, a special and intermediate steel moment frame connection for seismic applications: "Since the welds are shop welds, considerable latitude is possible in the selection of the weld process as long as the finished weld meets the Demand Critical Weld requirements stipulated in the AISC Seismic Provisions. In the test specimens used to prequalify this connection, electroslag, gas shielded metal arc, and flux cored arc welding have been used." (American Institute of Steel Construction 2014, Sato et al. 2007).

1The Oregon Graduate Institute of Science & Technology (OGI) was part of the Oregon Health and Science University (OHSU). By 2010, its academic programs and research were disseminated to other OHSU units. 2 Refer to clauses 1.3.3 and Q1.1 of the Bridge Welding Code. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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4. Narrow-gap Improved Electroslag Welding (NGI-ESW, ESW-NG) 4.1 Introduction This chapter describes the components and procedures of modern electroslag welding, ESW-NG. Particular attention is given to the AASHTO/AWS D1.5M/D1.5 Bridge Welding Code - henceforth referred to as the Bridge Welding Code (American Association of State Highway and Transportation Officials 2010). The Bridge Welding Code generally approves ESW to weld members or member components made from common types of bridge steels. However, only ESW-NG is permitted, unless another ESW process is approved in accordance with Annex J of the Bridge Welding Code. Annex J is not discussed here. As with all welding procedures, a sound, non-porous ESW-NG weld requires that the base metal and all welding consumables and non-consumable materials be free of moisture, oil, rust, and dirt. Care should be taken in the storage and use of wire, guides, insulators, sealants, shoes, sumps, etc. 4.2 Conventional and Narrow-gap Electroslag Welding The researchers at the Oregon Graduate Research Institute found that by decreasing the root width (i.e., gap) of the weld, the speed of the electroslag welding process could be increased and the voltage could be decreased. Thus, the cooling rate was faster; enhancing the coarsecolumnar grain structure of the weld. They also found that the inclusion of nickel and molybdenum in the wire core improved the weld's toughness by promoting equiaxed grain structure growth at the weld axis. However, the researchers concluded that complete fusion could not be realized without generating more heat using a higher current than that needed for conventional ESW. Nevertheless, the manufacturing speed, toughness, and reliability of an ESW-NG weld proved to be far superior to that of a conventional ESW weld. Arcmatic® Welding Systems, Inc. (Arcmatic® ) fine-tuned and automated the ESW-NG welding method. Arcmatic® trademarked VertaSlag®, a modular, programmable, computer controlled ESW-NG welding process (Bong 2006, 2009a, 2011, 2012, and 2014a; Bong and Bock 2008; and Bong et al. 2001 and 2006). At the time of this writing, VertaSlag® is the only commercial turnkey ESW-NG system. A comparison of the conventional ESW welding method conducted prior to the development of ESW-NG and that specified in the Bridge Welding Code is presented in Table 1.

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Table 1: Conventional Electroslag Welding and ESW-NG Conventional ESW

Bridge Welding Code's ESWNG Specifications

Gap width (inches1)

1.25

3/4 + 1/8

Wire Type

Solid

3/32 in. or 1/16 in. metalpowder cored tube

Potential (volts) 3/32 in. single wire 3/32 in. two wires 1/16 in. single wire 1/16 in. two wires

41-42

Parameter

Current (amperes) 1 2

33-37 31-36 29-35 28-33 6002

600-1000

1 inch = 1 in. = 25.4 mm Approximate

4.3 ESW-NG Wire Guides Figure 14 generally describes wire guides. To accommodate a narrow gap and base metal fabrication tolerances, the guide, including its insulators, should not be over 1/2 in. (13 mm) in thickness. If a wire guide is not properly configured and aligned in the weld cavity, copper from the welding shoes can become part of the weld and cause hot cracking. Incomplete fusion and/or a non-uniform weld nugget of hourglass shape may also result. The consumable guides may be manufactured from low-carbon cold-rolled steel bar or tubing. For example, VertaSlag® guides are made from three ASTM 1006 carbon steel strips. One side of the guide is a flat strip of 12gauge (2.77 mm) thickness. The other side of the guide is of two 16-gauge (1.65 mm) strips, with cold-formed channels that provide the wire housing (Figure 14c). The Bridge Welding Code's specified clearances and maximum wire channel spacing and widths are given in Table 2. Annex Q, of the Bridge Welding Code, offers guide configuration options. These are presented in Table 3. The metal guide must be insulated to prevent its contact with the base metal and welding shoes, which would cause an electrical short-circuit. Figure 14a shows three insulators. Annex Q of the Bridge Welding Code recommends that the insulators be composed of vitreous aluminosilicate fiber refractory material1 spaced 6-8 inches (150-200 mm) apart. The insulators may be attached to the guide with alumina putty that is also commonly used as a sealant for welding shoes.

1

Vitreous aluminosilicate fiber refractory material is glass-like material composed of silicon and oxygen and countercations that are stable at high temperatures. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Reduced contact surface

Wire in channel Guide

Shoe Shoe relief

Channels

Base metal

Base metal

Shoe

Guide

Insulators

a. Cross-sectional view including a duel-wire guide.

b. Isometric of single-wire guide in joint.

c. Guide manufacturing.

Figure 14: VertaSlag® Joint Configuration and Guide Manufacturing

Table 2: Bridge Welding Code's Specifications for Guide Clearance and Spacing (inches1) Elements Minimum Maximum Between guide edge and inside surface of welding shoe 1/4 5/8 Between inside surface of welding shoe and center of channel 1/2 1-1/4 Center-to-center spacing of channels 2 Channel width for 3/32 in. diameter wire 1/8 Channel width for 1/16 in. diameter wire 3/32 1

1 inch = 1 in. = 25.4 mm

Table 3: Guide Configuration Examples Guide Width Plate Thickness (inches1) (inches1) 1 to 1-1/4 3/4 1-1/4 to 2-1/2 1 to 1-1/2 2 to 2-1/2 1-1/2 2 to 3 1-1/2 to 2-1/4 2-1/4 to 3-1/2 1-3/4 to 2-1/2 3 to 4-1/2 2-1/2 to 4 1

No. of wires 1 1 1 2 2 2

Wire separation (inches1) 1 1 2

1 inch = 1 in. = 25.4 mm

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4.4 Bridge Welding Codes' Specifications for Wire (Electrode) and Guide Chemistry Table 4 presents the Bridge Welding Code's maximum allowable quantities of alloying agents in ESW-NG weld wire and guides. These specifications are intended to reduce susceptibility to solidification cracking and ensure satisfactory toughness.1 The Bridge Welding Code specifies a maximum diffusible hydrogen of 4 mL/100 g for ESW-NG weld wire. The chemistry and diffusible hydrogen of each wire lot must be evaluated according to the procedures described in Annex I of the Bridge Welding Code. Table 4: Maximum Alloy Limits of ESW-NG Wire and Consumable Guide % by Weight Element Wire Consumable Guide Carbon (C) 0.03 0.06 Manganese (Mn) 1.0-1.4 1.0 Silicon (Si) 0.30-0.45 0.6 Chromium (Cr) 0.05 0.1 Nickel (Ni) 2.7-3.2 0.23 Molybdenum (Mo) 0.25-0.45 0.03 Aluminum (Al) 0.03 0.05 Copper (Cu) 0.06 0.05 Titanium (Ti) 0.01-0.04 0.05 Sulfur (S) 0.015 0.02 Phosphorus (P) 0.015 0.02 Vanadium (V) 0.01 0.01 Boron (B) 0.001 0.001 Niobium (Nb) 0.01 0.01

4.5 ESW-NG Welding shoes In addition to containing the molten weld, welding shoes also promote the formation of a thin slag layer between each shoe and the weld, which prevents the bonding of shoes to the joint. However, another important function of welding shoes is the withdrawal of heat during the welding process. Optimal cooling rate promotes a tough weld microstructure and a homogeneous weld and HAZ. Welding shoes of pure copper provide ideal heat dissipation.2 The fabrication of welding shoes includes drilling cooling channels, typically tubular of 3/8 in. (10 mm) diameter, and other details in solid 1 in. (25 mm) thick copper blocks. 1

High levels of carbon, nickel, sulfur, and phosphorous may cause cracking. Manganese, silicon, and titanium help reduce the probability of cracking. 2 The Bridge Welding Code also accepts copper variations such as tough pitch copper, OFHC copper, and phosphorus-deoxidized copper. Copper alloys, brasses, and bronzes are not appropriate for ESW-NG welding. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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ESW-NG welding shoes should be at least 4 in. (100 mm) wide and 12 in. - 18 in. (300 mm - 450 mm) long. These dimensions provide a good balance between heat dissipation and economics. The primary function of welding shoe reliefs (see Figure 14a) is to facilitate a reinforced weld. The Bridge Welding Code suggests a depth of relief of 0.075 in. to 0.083 in (1.9 mm - 2.1 mm) and a width between 15/16 in. (24 mm) and 1-1/16 in. (26 mm). Welding shoes have been developed that provide better control of heat dissipation than standard welding shoes and versatile fit-up. These two improvements are discussed below. While rapid heat transfer is desirable, if heat escapes through the welding shoes too rapidly, the weld cross-section will be of exaggerated barrel-shape, or worse, incomplete fusion at the weld corners can occur. Voltage may be increased to solve this problem, at the expense of an increase in heat input. Therefore, proper architecture of welding shoes can promote complete and uniform fusion of the weld and base metals. A tri-part welding shoe (Tri-part Shoe) has been developed that has three features that enable complete fusion at the weld's corners without the need to increase voltage. These are the shoe reliefs, discussed previously, and contact surface reduction adjacent to the base metal (see Fig. 14a), and two outer sections of the shoe that are water-cooled and a center section that is not (Fig. 15a). The outer sections of the Tri-part Shoe have a larger water channel, providing greater flow volume, than standard ESW welding shoes. Arcmatic® found that reliable ESW-NG welds made with Tri-part Shoes and an electric current of 1000 amps requires 8 volts or less than a weld constructed with standard welding shoes. This reduction in 8 volts for a 1000-amp weld reduces the electric power, which is directly proportional to heat input, by an impressive 8000 watts. The Tri-part Articulated (Flex) Shoe has also been developed (Figure 15b). The center section of this welding shoe consists of multiple 1/8 in. (3 mm) thick strips of copper. This flexible component allows the welding shoe to snugly fit against misaligned plates and plates with small differences in thickness. An unforeseen enhancement (beyond ease of shoe fit-up) to the ESW-NG process was discovered during the development of the Tri-part Flex Shoe. The grooves of the flexible part of the welding shoe retained more flux than a rigid welding shoe. This additional flux provides insulation that impedes the center of the welding shoe from chilling the weld pool, and fusion is enhanced at the corners of the weld cavity. Thus, a rigid tri-part serrated welding was developed (Figure 15c). There are also welding shoes for welding plates of different thickness (Figure 15d) and a welding shoe for welding T-joints, which is particularly useful for welding stiffener plates and base plates to the flanges of W-shapes and plate girders (Figure 15e). Welding shoes have also been designed for oblique-angled joints (refer to section 6.2 of this Steel Tips). The Bridge Welding Codes' welding shoe specifications are presented in Table 5.

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a. Tri-part Shoe

b. Tri-part Flex Shoes

c. Serrated Shoe

shoe transition shoe

shoe

d. Transition Shoes

e. T-joint Shoes

Figure 15: Welding Shoes 4.6 ESW-NG Flux Like conventional ESW welding, the ESW-NG welding process is started with an arc applied through pre-deposited flux (see Figure 2, a and b). About 1/3 of the required starting flux is added to the welding sump before the commencement of welding. The balance of the starting flux should be gradually added during the first minute of welding. The amount of starting flux required varies. For example, ASTM A 709 bridge girder steel requires 3 ounces (85 g) for 2 in. (50 mm) thick joints and 9 ounces (260 g) for 3 inch (75 mm) thick joints. During ESW-NG welding the slag pool is depleted via the formation of a slag layer between the welding shoe and the weld. The Bridge Welding Code requires the use of an automatic flux dispenser during the construction of an ESW-NG weld. Automatic flux dispensers monitor variations in electric current and potential to maintain a constant-depth slag pool. Flux addition is generally very small and constant. The required amount of flux addition is about 0.2 ounces (5.5 g) per minute. Neutral fused fluxes with maximum moisture contents of 0.1% are specified by the Bridge Welding Code for ESW-NG welding. Neutral flux promotes a constant slag pool depth and weld metal chemistry. Fused flux has a relatively high resistance to moisture absorption. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Table 5: The Bridge Welding Code Welding Shoe Specifications Parameter

Specification

Material

Copper

Material used to prevent slag leakage between shoe and base metal.

Dry refractory. Water-based sealants may only be used over dried refractory sealants along the outside edges of a shoe.

Shoe series plumbing

Plumb shoes on each side of the joint separately.

Coolant Type

Water

Coolant flow rate

Minimum of 4 gal. (15 L) per minute per side

Coolant temperature

Warm to the touch.

Coolant temperature rise

For each side of joint: 5-20 degrees F (3-11 degrees C) from inlet of the first shoe to outlet of the last shoe for each group (series) of shoes.

Minimum shoe removal time

2 minutes after slag pool advances to next shoe or upon completion of weld.

Shoe coolant - general

Water leaving shoes on one side of joint must be cooled before it enters shoes on the other side of joint. Prevent condensation caused by cooling shoes below the atmospheric dew point. Prevent blockage. Trapped water in cooling shoes can lead to dangerous steam pressure.

4.7 ESW-NG Electrical Parameters. Table 6 presents an example of ESW-NG electric current and welding speed necessary to produce sound, tough welds. This table was adapted from Annex Q of the Bridge Welding Code. As discussed in section 2.4 of this Steel Tips, the resistance to the flow of electricity is not constant during electroslag welding. A DC power supply with a 100% duty cycle1 rating and constant voltage is recommended in Annex Q of the Bridge Welding Code.

1Generally,

duty cycle is the percentage of one period a signal is active. In the context of welding in the United States, a duty cycle is the percent of time in a 10 minute interval that a welding power supply can operate at its rated output. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Table 6: ESW-NG Example of Number of Wires, Current, and Speed of Wire Feed and Welding for ASTM A 709 Bridge Steel Speed, in./min (mm/min)

Plate Thickness, in. (mm)

Number of Wires

Current, amperes

Wire

Welding

1 (25) 1-1/4 (32) 1-1/2 (38) 1-3/4 (45) 2 (50) 2 (50) 2-1/4 (57) 2-1/2 (65) 2-3/4 (70) 3 (75)

1 1 1 1 1 2 2 2 2 2

600-650 650-700 790-850 850-910 900-950 900-980 1050-1210 1170-1310 1270-1370 1340-1470

230 (580) 255 (650) 280 (710) 310 (785) 340 (860) 170 (430) 210 (540) 230 (590) 245 (630) 260 (665)

3 (75) 2-5/8 (67) 2-1/2 (65) 2-1/4 (55) 2 (50) 2 (50) 1-7/8 (48) 1-3/4 (43) 1-5/8 (41) 1-1/2 (38)

During ESW-NG welding, the wire feed rate sustains the required voltage (Table 1). The feeding mechanisms must deliver sufficient torque to push the weld wire over a distance defined by the wire spool and the weld pool. It must also support a power supply with a 100% duty cycle rating. The Bridge Welding Code also specifies at least two electrical leads ("work leads") to minimize magnetization -- one on either side of the sump. 4.8 The Bridge Welding Code's Specifications on ESW-NG Restarts, Interruptions, and Repairs An ESW-NG welding process should be continuous for the entire construct of a joint. Restarts are allowed if the point of restart is clearly marked. Further, the restart region plus a minimum of 3 inches (75 mm) above and below the restart area cannot be considered to be part of the final completed product. If the construct of an ESW-NG weld is interrupted (e.g., by depletion of welding wire) the entire weld must be removed to at least 1/8 in. (3mm) beyond the fused metal zone and rewelded.1 Removal is also required if weld defects, as defined by AASHTO, are within 1/4 in. (6 mm) of the weld centerline and their cumulative length is greater than 15% of the weld's length. The Bridge Welding Code specification details of the ESW-NG welding process that have not been previously discussed in this Chapter are presented in Table 7. 1

The Contractor also has the option of rewelding the joint with another process approved by the Bridge Welding Code. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Table 7: Additional Bridge Welding Code ESW-NG Specifications Parameter

Specification

Sump Depth

Greater of 3 in. (75 mm) and base metal thickness

Opening width

1 in. (25 mm)

Base thickness

1-3/8 in. to 2 in. (32 mm - 50 mm) Location Required Removal Within the joint. Consumed with weld. Removed along with a 1/8 On permanent base metal in. (3 mm) deep layer of outside the joint. base metal under the tack weld. On base metal that will be Discard along with disremoved and discarded. carded base metal. Formula for target travel speed 3.0 - (minus) 0.5 x base metal thickness (in./min) [75 - (minus) 0.5 x base metal thickness (mm/min)]

Removal of tack welds for mounting sump and run-off tabs.

Target travel speed (vertical rate of rise): production travel speed must be between 90% and 125% of target travel speed. Base metal temperature Wire oscillation Inspection type

Above atmospheric dew point. Not permitted. Radiographic and ultrasonic.

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5. Electroslag T-joint Shop-Welding 5.1 Introduction Electroslag welding is generally a very effective method to weld butt joints, T-joints, and joints with oblique angles. This chapter discusses the use of ESW to weld T-joints. 5.2 Electroslag Welding Applied to the Shop-Welding of Stiffener, Continuity, and Base Plates to the Flanges of Open Shapes The joint formed by a stiffener, continuity, or a base plate and a flange of an open shape is a Tjoint. Figures 15e and 16 present cross-sections of square-groove T-joints with welding shoes. Column or Beam Flange

Welding Shoes Weld Cavity

Column Flange

Welding Shoes Stiffener Plate

Base Plate

Figure 16: Flange-to-Base-Plate and Flange-to-Stiffener-Plate Joints There was a boom in high-rise building fabrication in California beginning in the late 1960s and extending through the 1980s. During that time an electroslag welding method was developed that increased the fabrication speed of shop-welding stiffener/continuity plates to the flanges of open shapes (e.g., W-shapes and plate girders). Traditionally, the plates of T-joints were beveled and joined to the open shape with flux-cored arc welding (FCAW). As a stiffener plate increases in thickness, the FCAW welding process increases in both labor and time because the welds must be made in multiple passes. With electroslag welding, the recommended configuration of the guide and its wires (Table 3) render the welding time and labor expenses practically independent of the thickness of the joint.

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Figures 17a and 17b present two stiffener plate joint configurations. One option, presented in Figure 17a, utilizes two plates1, the "double-sided-two-plates" option. The web dams the molten weld when a double-sided-two-plates configuration is used, making a sump unnecessary. However, back-gouging is required. Another option, developed between 2005 and 2010, incorporates only a single plate, the "double-sided-single-plate" option (Figure 17b). This option permits a doubly symmetric open shape to remain in one position during the ESW welding process, while the double-sided-two-plates option requires a 180 degree rotation of the girder after completion of the welding of the first stiffener plate to a girder flange. During fabrication of the double-sided-single-plate stiffener plate joint, a beveled slot must be cut entirely through the web of the girder. The slot is approximately 3/4 in. (19 mm) wider than the thickness of the stiffener plate and extends the length defined by the inside faces of the flanges. Unlike the double-sidedtwo-plates option, the welding instrumentation of the double-sided-single-plate stiffener plate must include a sump.

k

1.5 in. (40 mm)

k

k-area toe of fillet

a. Double-sided-two-plates: requires girder rotation during welding.

b. Double-sided-single-plate: requires web machining & welding sump.

c. k-Area

Figure 17: Double-Sided Stiffener Plate Options and k-Area

1Using

this option, the side of the plate next to the web must be beveled and welded to the web, or fillet welded to the web on either side of each plate. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Section 4 of AWS D1.8: 2009 addresses the general seismic provisions for stiffener plates. This specification includes reference to the “k-area” of a W-shape (Figure 17c)1. Residual stresses, a consequence of the hot-rolling process, reduces k-area toughness. Welding in the k-area can lead to cracking. The slot required for the double-sided-single-plate configuration relieves the k-area residual stresses. After the development of the double-sided-single-plate configuration, the "dual stiffener" plate option was developed, which leaves a portion of the web beneath the stiffener plate intact. Fabrication of a dual stiffener plate requires machining slots that extend from the face of the flange to a distance required to complete the welding process - about 1/2 inch longer than the width of the welding shoe. Like the double-sided-single-plate configuration, the dual stiffener plate option does not require rotation of the girder. This configuration also involves less machining than the double-sided-single-plate configuration. Prior to the FHWA moratorium on electroslag welding, the following major California structural steel fabricators, in addition to many others throughout the United States, were using electroslag welding: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Pittsburgh Des Moines Steel (Santa Clara, CA) Pittsburgh Des Moines Steel (Fresno, CA) Bethlehem Steel (Pinole Point, CA) US Steel - American Bridge Div (South San Francisco, CA) US Steel - American Bridge Div (Antioch, CA) US Steel - American Bridge Div (Los Angeles, CA) The Herrick Corporation - (Hayward, CA) Kaiser Steel - (Fontana, CA) Kaiser Steel - (Napa, CA)

Between the late 1960s and late 1980s these fabricators collectively welded over a hundred thousand stiffener plates with the ESW process in Northern and Southern California2. The October 17, 1989, Loma Prieta and January 17, 1994 Northridge earthquakes provided "real world" comparisons of all of the welding processes used to fabricate steel structures in California. Millions of dollars were spent to repair cracked gasless FCAW welds after the Northridge earthquake. According to the lead Los Angeles structural inspection firm assessing weld damage after the Northridge earthquake, not one failure or crack propagation was discovered in any of the electroslag welds inspected (Bong 2009b).

1The

American Welding Society defines the k-area as "...the region of the web that extends from the tangent point of the web and the flange-web fillet (AISC k dimension) a distance 1-1/2 in [40mm] into the web beyond the k detail..." (American Welding Society 2009). 2Two of the tallest buildings in California were welded using ESW - The Bank of American building in San Francisco, and the twin tower Security Pacific building in Los Angeles. Countless smaller buildings were also welded during this period of time in the greater San Francisco Bay area, the Los Angeles basin, and the San Diego area. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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5.3 Electroslag Welding Applied to Shop-Welding Continuity Plates of Built-up Box Columns Continuity plates are commonly incorporated in built-up box columns (box columns) at their beam-column joints. Prior to the advent of electroslag welding, fabricators welded three sides of a box column together, then inserted the continuity plates into the box column and welded three sides of each stiffener plate to the three inside walls of the box column via bevel welds (Figure 18a). The final wall of the box column consisted of three plates. These plates were welded to the continuity plates. As high-rise buildings got taller, the continuity and box column plates of the columns that supported the bottom floors of the buildings became very thick, some as thick as 6 inches (15 cm). Their continuity plate welds took several days to complete until ESW was introduced into the box column fabrication process (circa 1970). The process initially used only one electroslag weld per stiffener plate, which joined the final (fourth) side of the continuity plate to the final (fourth) monolithic (i.e., did not require cutting into three pieces) box column plate (Figure 18b). The continuity plate was fabricated such that a gap between the fourth continuity plate edge and the fourth box column plate existed, which formed an ESW weld cavity. Holes (“keyholes”) were then cut through two parallel box column plates in line with the centerline of the gap, where a sump and run-off tabs were installed, and finally, a wire guide was inserted to commence the ESW welding process (Figure 18b). The process was dubbed the "keyhole" welding procedure. The vertical rate of rise required to produce a sound keyhole weld is about 1/2 inch per minute (13 mm/minute). Figures 18c and 18d illustrate how ESW-NG can be used to achieve even greater economy when welding stiffener plates to the walls of box columns. Figure 19 presents cross-sections ESW-NG keyhole joint before and after welding. Note that welding shoes do not contain the weld during welding. Containment plates of 1/2 in. (13 mm) thickness and of the same steel as the stiffener plates contain the weld. A spacer of 1/8 in. (3 mm) thickness, also of the same steel as the stiffener plates, serves to widen the weld at the face of the box column. The outer containment plate provides an additional heat sink that retards shrinkage crack development. The use of only one pair of containment plates with no spacer caused a crack to initiate from the containment plate (Sarkisian et al. 2013).

Continuity plate

Keyholes

Location of ESW weld

Typical “keyhole” locations

Guide (typ.)

CJP, 3 sides Plan view Elevation view

a. Early configuration.

b. Configuration using one keyhole.

c. Configuration using two keyholes.

Figure 18: Box Column Continuity Plate ESW-NG Welding Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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d. ESW-NG welding instrumentation.

Figure 18 (cont'd): Box Column Continuity Plate ESW-NG Welding

Containment plate

1 in. = 25.4 mm a. Cross-section of set-up for Box Column continuity plate ESW-NG Welding.

b. Completed weld.

Figure 19: ESW-NG Box Column Continuity Plate Weld

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6. Electroslag Welding in the Field 6.1 Introduction This chapter focuses on contemporary applications of modern ESW-NG field-welding. While conventional electroslag welding has been used in the field for some notable construction projects1, only modern ESW-NG field-welding applications are presented here -- for the East Span of the San Francisco-Oakland Bay Bridge, completed in 2014, and for the Wilshire Grand Hotel in Los Angeles, California, completion date scheduled for 2017. The chapter concludes with a discussion of ESW-NG for general steel building field construction. 6.2 East Span, San Francisco – Oakland Bay Bridge Tower The first ESW-NG field-welding occurred during the construction of the single tower of the world's longest self-anchored suspension (SAS) bridge. The tower supports the main span of the East span of the San Francisco/Oakland Bay Bridge (completed on February 3, 2014) (Figure 20). The first 32.8 ft. (10 m) of the 524.8 ft. (160 m) tower consists of steel plates joined by twenty (20) ESW-NG welds, forming a monolithic steel structure. The structure supports the tower's four legs (Figure 21). The plates are between 1.75 and 4 inches (44-100 mm) thick. Each weld took about 4.5 hours to complete.

Figure 20: East Span, San Francisco – Oakland Bay Bridge Tower Under Construction

1

An example of a field application of conventional electroslag welding is the construction of the Mercedes-Benz Superdome in New Orleans, Louisiana, circa 1975. The tension ring of the dome consisted of 24 curved sections. The flanges were spliced together using Electroslag welding (Williams and Gibson 1976). Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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a. Locations of ESW-NG welds (indicated with arrows).

b. Photograph of tower base.

Figure 21: East Span, San Francisco–Oakland Bay Bridge SAS Tower Base (Turpin et al. 2012)

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Five unique joints, requiring custom welding shoes, exist in the tower base (Figure 22). During the ESW-NG welding, three shoes per side were leap-frogged in unison ahead of the molten slag and weld pools. Thirty-six feet (11 m) long consumable low-carbon guides channeled two 3⁄32in. (2.4 mm) diameter wires into the molten slag and weld pools. The ESW-NG welds were completed in 60 days. Less than 5% of the total length of the welds required repairs. Weld defects were generally due to variations (on the shallow side) in the optimal slag pool depth. Only one of the 20 welds was interrupted. This interruption was due to an unexplained loss of primary power. The above information was obtained from Turpin et al. 2012. Further details, including the special challenges and the ESW-NG approval process (including full-scale testing) for these welds, may be obtained from this AWS Journal article. The article includes the following testimony that suggests the use of ESW-NG welding will be increasingly common in field construction. ESW-NG has been shown to be the safest and most economical choice for welding thick joints in steel structures regardless of the seismic design category of the structure. "The narrow-gap improved electroslag welding... was used... because of its ability to produce single-pass vertical welds on heavy-section structural steel without a preheating requirement. Access within the tower base was limited and the preheating requirement with any other welding process would have been prohibitive from the standpoint of safety and economy. In addition, these welds had to be made in a very short amount of time and FCAW-G, SMAW, and FCAW-S do not offer the deposition rates necessary to meet the schedule requirements...The extraordinary length of the tower base welds presented several challenges. Alternatives such as FCAW-G, SMAW, and FCAW-S would have been more challenging for the welders, would have had higher repair rates and would have taken impossibly longer. The ESW process proved to be safe, reliable, and efficient." (Turpin et al. 2012)

Figure 22: East Span, San Francisco–Oakland Bay Bridge SAS Tower Base Joints (Turpin et al. 2012) Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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6.3 The Wilshire Grand Hotel, Los Angeles, California The tallest skyscraper in California, The Wilshire Grand1 Hotel and office building, is under construction in downtown Los Angeles at the time of this writing. Its lateral force resisting system consists of a concrete core, outrigger buckling-restrained braces (BRBs), and perimeter belt trusses located between the 28th and 31st floors, the 53rd and 59th floors2, and the 70th and 73rd floors (Figure 23). The BRB gusset plate connections are approximately 12 ft. high x 2.75 in. wide (3.6 m x 7 cm). ESW-NG welds will join the gusset plates for the BRB braces to steel plates embedded in the concrete core (Figure 24). ESW-NG welds will also connect the chord and diagonal members, up to 730 lbs./ft. (10.7 kN/m) in weight, of the belt trusses' flanges to the face of the box columns (Figure 25). These welds will be up to 49 inches (149 cm) long and up to 5 in. (15 cm) thick (Curwen 2014).

BRB Outrigger (typ.) Con cret

e Co re

Belt Tru ss

Figure 23: Erection Drawing Showing Concrete Core, Outrigger BRB Braces, and Belt Truss at the 28th-31st Stories of Wilshire Grand, Los Angeles, California

1

The Wilshire Grand, located at the corner of Wilshire Boulevard and Figueroa Street, will include 73 stories, and will be 934 ft. (285 m) high at the roof, 1100 ft. (335 m) at the spire. It was designed by AC Martin & Associates and engineered by Brandow and Johnston (engineer of record) and Thornton Tomasetti. The steel fabricator and erector is Schuff Steel. It is scheduled to be completed in 2017. 2 There will be no belt trusses between the 53rd and 59th floors. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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12 ft. (3.6 M) long ESW-NG weld

Figure 24: Wilshire Grand Hotel and BRB Outriggers

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Face of box column

ESW-NG weld cavity

Belt truss members

Figure 25: Wilshire Grand Hotel Box Column and Belt Truss Joint 6.4 ESW-NG for General Field-welding of Building Structures ESW-NG played a critical role in the splicing of the steel plates at the base of the San FranciscoOakland Bay Bridge's tower, and now it's being used for key components of the lateral force resisting system of the soon-to-be tallest building in California. This welding method has shown to be the most economical and reliable choice for field-welding steel components in heavy construction. Field application of ESW-NG is also poised for general building construction. Portable ESWNG welding systems have been developed for welding processes that would otherwise be done in a steel fabrication shop. Because joints oriented at up to 45-50 degrees from the vertical can be successfully welded with ESW-NG, it is well suited to the field-welding of column flange splices (Figure 26) (Bong 2014b). Portable welding equipment can be elevated to a recently constructed floor and rolled to a column splice location to complete the field-welding. It takes a day or more to splice a column flange using FCAW. In comparison, it takes about one minute to weld an inch of ESW-NG weld. That is, a 14-inch flange can be welded in about 14 minutes. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Figure 26: ESW-NG Welding Applied to Column Splicing Showing 45 Column Flange Splice, Weld Cavity, Sump, and Run-off Tabs

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7. Conclusion Electroslag welding is the most cost-effective choice for the production of thick welds in steel bridges and buildings. Not only is ESW much faster than multi-pass welding methods, it is also immune to the defects that can be caused by a weld pass. Modern ESW has been made possible by more than a century of research. An FHWA-funded research program, which was the serendipitous outcome of a 1976 ESW fabrication blunder, made ESW even more economical and reliable than before. Prior to this research, ESW weld cavities were about 1.25 inches (32 mm) wide. Modern ESW includes a much narrower joint, approximately 3/4 inch (19 mm) wide. It was therefore dubbed electroslag welding - narrow gap (ESW-NG). An ESW-NG weld consists of coalesced alloy-cored wire, base metal, and a stationary consumable wire guide. The manufacture of a sound weld requires about one inch of molten slag floating atop a molten weld pool, an automatic flux dispenser, a wire feeding machine, water (coolant), plumbing, and a power supply. A power supply with variable balance, constant potential, and AC square wave power generation is well suited to ESW-NG. Containment of the molten weld and slag pools is achieved via a sump, runoff tabs, copper welding shoes, and sealant. Welding shoes are detailed for optimal heat transfer and joint orientation. Shop-welding applications of ESW-NG include thick plate splices and T-joints formed by welding stiffener, continuity, or base plates with the flanges of open shapes. The "key hole" ESWNG welding method has also proved to be economical for shop-welding thick stiffener plates to the inside walls of box columns. Because ESW-NG does not require preheating and can be done in one pass, it has now recognized by prominent steel fabricators and erectors as the most reasonable choice for field-welding thick steel joints. The first field application of ESW-NG was the production of the 20 - 33 ft. (10 m) welds that joined the steel plates forming the major foundation at the bottom of the single tower in the self-anchored suspension (SAS) bridge of the East span of the San Francisco/Oakland Bay Bridge (completed on February 3, 2014). Major steel components of the lateral force-resisting system of the tallest building West of Chicago, the Wilshire Grand Hotel in Los Angeles, California, will include field-welded ESW-NG welds. Joints oriented up to 45 degrees can be efficiently welded using ESW-NG. Therefore, the steel construction industry will likely commonly use ESW-NG for the field-splicing of thick column flanges. ESW-NG is accepted by the AASHTO/AWS D1.5M/D1.5 Bridge Welding Code to weld common types of bridge steels and can also satisfy criteria for Demand Critical Welds in steel buildings, including those in special moment and braced frame connections, column splices, belt chord connections, and base plate joints.

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______________________________________________________________________

References ______________________________________________________________________ Allan, W. Jr. (1977). "Pittsburg Bridges Falling Down," The Pittsburg Press Roto, June 5, 1977, Pittsburg, PA. American Association of State Highway and Transportation Officials (2010). AASHTO/AWS D1.5M/D1.5:2010 Bridge Welding Code, 6th Edition, with 2011 and 2012 AASHTO Interim Revisions. American Institute of Steel Construction (2010). "Seismic Provisions for Structural Steel Buildings," Seismic Design Manual, ANSI/AISC 341-10. American Institute of Steel Construction (2014). "Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications, Including Supplement No. 1 and Supplement No. 2," ANSI/AISC 358-10, ANSI/AISC 358s1-11, ANSI/AISC 358s214. American Welding Society (2009). Structural Welding Code - Seismic Supplement, AWS D1.8/D1.8M. American Welding Society (2010). Structural Welding Code, AWS D1.1/D1.1M. Benardos, N. (1888). "Working Metals by Electricity," US Patent 379,453. Bong, W.L. (2006). "Consumable Guide Tube," US Patent 7,148,443 B2. Bong, W.L. (2009a). "Consumable Guide Tube," US Patent 7,550,692 B2. Bong, W.L. (2009b). "The History of Electroslag Welding for High Rise Buildings and Bridges," Arcmatic Welding Systems, Inc. Bong, W.L. (2011). "Assembly, System and Method for Automated Vertical Moment Connection," US Patent 7,148,443 B2. Bong, W.L. (2012). "System and Method for Multi-Pass Computer Controlled Narrow-gap Electroslag Welding Applications," US Patent 8,110,772. Bong, W.L. (2014a). "Electroslag Welding with Variable Balance, Constant Potential, Alternating Current, Square Wave Welding Power Supply," US Patent 8,816,238 B2.

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Bong, W.L. (2014b). "Improved W-Column for On-site Erection of Steel Framed High Rise Buildings, and Methods of Use Thereof," US Provisional Patent 62/093,011. Bong, W.L. and Bock, C.A. (2008). "Modular Welding System," US Patent 7,429,716 B2. Bong, W.L., Bock, C.A., and Glenn-Lewis, M.D. (2001). "Welding System and Method," US Patent 6,297,472,B1. Bong, W.L., Toy, S.E., Connor, J.R. (2006). "System and Method for Electroslag Welding an Expansion Joint Rail," US Patent 7,038,159 B2. Cabelka, J. (1962). "Process of Electrically Welding Under a Layer of Molten Slag," US Patent 3,046,383. Curwen, T. (2014). "Built to Defy Severe Quakes, the New Wi1shire Grand Hotel is Seismically Chic," The Los Angeles Times, November 2, 2014. Federal Highway Administration (1996). "Technical Information Guide for Narrow-gap Improved Electroslag Welding," Metallurgical Background for Narrow-gap Improved Electroslag Welding, Report No. FHWA-SA-96-053. Fisher, J.W., Pense, A., Wood, J.D., and Daniels, J.H. (1980). "Evaluation of the Fracture of the I-79 Back Channel Girder and the Electroslag Welds in the I-79 Complex," Fritz Laboratory Reports. Paper 496, October 1980. http://preserve.lehigh.edu/engr-civilenvironmental-fritz-lab-reports/496. Hannahs, J.R. (1970). "Apparatus for Electroslag Welding," US Patent 3,518,397. Hannahs, J.R. (2003). unpublished letter to William L. Bong, July 24, 2003. Hobart Brothers Technical Center (1970). "Hobart Welding Process Manual: the Portaslag welding process." Troy, Ohio. Hopkins, R.H. (1940). "Method for Manufacturing Composite Metal Articles," US Patent 2,191,481. Irving, B., "Welding's Vital Part in Major American Historical Events" http://www.aws.org/resources/detail/blockbuster-events-in-welding-history Kitani, Y., Ikeda, R., Ono, M., and Ikeuchi, K. (2009). "Improvement of the Weld Metal Toughness in High Input Electro-Slag Welding," Welding in the World, V. 53, No. 3/4. Mosny, M. and Pavelka, V. (1961). "Device for Controlling the Level of Molten Slag," US Patent 2,972,041.

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Paton, B.E., ed. (1962). Electroslag Welding. Translated from Russian by the American Welding Society, Inc., New York. Paton, B.E., ed. (1983). Electroslag Welding and Surfacing. Translated from the Russian by Boris V. Kuznetsov, Moscow, Mir Publishers. Sarkisian, M., Lee, P., Garai, R., Ozkula, G., and Uang, C-M (2013). "Effect of Built-up Box Column Electroslag Welding on Cyclic Performance of Welded Steel Moment Connections," SEAOC 2013 Convention Proceedings. Structural Engineers Association of California. Sato, A., Newell, J., and Uang C-M (2007). "Cyclic Testing of Bolted Flange Plate Steel Moment Connections for Special Moment Frames," Report No. SSRP-07/10, Department of Structural Engineering, University of California, San Diago, LaJolla, CA. Shrubsall, H.I. (1959). "Vertical Welding with Consumable Guide Tubes," US Patent 2,868,951. Turpin, B., Danks, D., Callaghan, J., and Wood, W. (2012). "Narrow-gap Electroslag Welding is Process of Choice for Welding San Francisco-Oakland Bay Bridge," Welding Journal, May 2012, 91(5). American Welding Society, pp. 24-31. Williams, M.C. and Gibson, W.R. (1976). "Louisiana Superdome," Modern Steel Construction, 16(1-2). American Institute of Steel Construction, pp. 3-7.

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About the Authors:

Janice Chambers has been a member of the structures faculty at the University of Utah in Salt Lake City since 1989. She has taught on the order of 100 structural mechanics and design courses, including 15 different topics ranging in level from sophomore to PhD. She has received two major teaching awards -a university-wide Student Choice Teaching Award, and Chi Epsilon's Excellence in Teaching Award for the Rocky Mountain District. Dr. Chambers focuses her research activities on steel structures, with emphasis on analysis and design. She was the PI on a grant to perform full-scale tests on the Slotted-Web connection. She executed the nonlinear finite element analysis of the prototype SidePlate® Connection, and also derived the closed-form stiffness matrix of the Reduced Beam Section. Dr. Chambers is from St. Louis, Missouri. She received her BS in civil engineering, summa cum laude, from the University of Missouri, Columbia. She received MS and PhD degrees in Civil Engineering from the University of Colorado, Boulder. She has five years full-time practical civil engineering experience with industrial employers Fluor Daniel, Irvine, CA; Boeing Aircraft, Long Beach, CA; and the City of Columbia, Missouri. She is a registered professional engineer in California and Utah, and a certified Structural Engineer in Utah.

Ronnie Medlock is Vice President, Technical Services, at High Steel Structures, LLC in Lancaster, Pennsylvania, where he is responsible for engineering and quality control and also plays a lead role in the implementation of innovative welding processes and techniques. His professional affiliations include the American Welding Society (AWS) Committee on Structural Welding (D1) and American Association of State Highway Transportation Officials (AASHTO) /AWS Bridge Welding Committee (D1.5); National Steel Bridge Alliance (NSBA) Technical Committee (chair); AASHTO/ NSBA Steel Bridge Collaboration (co-founder, main committee chair); and American Railway Engineering and Maintenance-of-Way Association (chair, Steel Structures Committee), and the Transportation Research Board (TRB). Prior to joining High Steel in 2006, he worked at Texas Department of Transportation (TxDOT), where he worked in steel bridge fabrication quality assurance and structural design. He can be reached at: High Steel Structures, Inc. 1915 Old Philadelphia Pike Lancaster, PA 17602 Phone: 717.823.6115 Email: [email protected]

She can be reached at: Department of Civil & Environmental Engineering 110 Central Campus Drive, Suite 2000 University of Utah Salt Lake City, UT 84112-0561 Phone: 801-581-3155/801-828-6333 Email: [email protected]

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List of Published Steel TIPS Reports ---------------------------------------------------------------------------------------------------------------------------------------July '13: The Manufacture and Supply of Structural Steel by Max D. Powell July '11: Steel Plate Shear Walls Performance Based Design by Nabih Youssef, Ryan Wilkerson and Daniel Tunick July '11: Welding of Seismically Resistant Steel Structures by Duane K. Miller April '11: Notes on Gusset Plates in Steel Trusses Evaluation, Repair and Retrofit by Abolhassan Astaneh Asi and Wahid Tadros March '11: The Design of Continuity Plate Welds in Special Moment Frames by Chia Ming Uang, Andy Tran and Patrick M. Hassett May’ 10: Notes on Blast Resistance of Steel and Composite Building Structures, by Abolhassan Astaneh Asl. April’ 10: Gusset Plates in Steel Bridges Design and Evaluation, by Abolhassan Astaneh Asl. April’ 10: Steel Plate Shear Walls: An Option for Lateral Resistance in High Rise Core Wall Buildings, by James O. Malley Dec.’09: Economy of Steel Framed Buildings for Seismic Loading, by Christopher Hewitt, Rafael Sabelli, and Jayson Bray. Oct.’08: A Comparison of Frame Stability Analysis Methods in AISC 360 05, by Charles J. Carter and Louis F. Gerschwinder. Sept.’08: Quality Assured Steel Bridge Fabrication and Erection, by Jay P. Murphy June ’08: Seismic Behavior and Design of Base Plates in Braced Frames, by Abolhassan Astaneh Asl. April ’08: Cost Effective Steel Bridge Fabrication and Erection, by Jay P. Murphy. June ’07: Early California Accelerated Steel Bridge Construction, by Jay P. Murphy. June ’07: Design of RBS Connections for Special Moment Frames, by Kevin S. Moore and Joyce Y. Feng. May ’07: Progressive Collapse Prevention of Steel Frames with Shear Connections, by Abolhassan Astaneh Asl. Jan.’07: Seismic Detailing of Special Concentrically Braced Frames, by Abolhassan Astaneh Asl, Michael Cochran, and Rafael Sabelli. Aug.’ 06: Alfred Zampa Memorial Steel Suspension Bridge, by Alfred Mangus, Sarah Picker July’ 06: Buckling & Fracture of Concentric Braces Under Inelastic Loading, by B. Fell, A. Kanvinde, G. Deierlein, A. Myers, and X. Fu. Aug.’ 05: Steel Angle & Tee Connections for Gravity and Seismic Loads, by Abolhassan Astaneh Asl. May’ 05: Design of Shear Tab Connections for Gravity and Seismic Loads, by Abolhassan Astaneh Asl. Jul.’ 04: Buckling Restrained Braced Frames, by Walterio A. Lopez and Rafael Sabelli. May’ 04: Special Concentric Braced Frames, by Michael Cochran and William Honeck. Dec.’ 03: Steel Construction in the New Millennium, by Patrick M. Hassett. Aug.’02: Cost Consideration for Steel Moment Frame Connections, by Patrick M. Hassett and James J. Putkey. June’ 02: Use of Deep Columns in Special Steel Moment Frames, by Jay Shen, Abolhassan Astaneh Asl and David McCallen. May’ 02: Seismic Behavior and Design of Composite Steel Plate Shear Walls, by Abolhassan Astaneh Asl. Sept.’ 01: Notes on Design of Steel Parking Structures Including Seismic Effects, by Lanny J. Flynn, and Abolhassan Astaneh Asl. Jun '01: Metal Roof Construction on Large Warehouses or Distribution Centers, by John L. Mayo. Mar.’ 01: Large Seismic Steel Beam to Column Connections, by Egor P. Popov and Shakhzod M.Takhirov. Jan ’01: Seismic Behavior and Design of Steel Shear Walls, by Abolhassan Astaneh Asl. Oct. '99: Welded Moment Frame Connections with Minimal Residual Stress, by Alvaro L. Collin and James J. Putkey. Aug. '99: Design of Reduced Beam Section (RBS) Moment Frame Connections, by Kevin S. Moore, James O. Malley and Michael D. Engelhardt. July '99: Practical Design and Detailing of Steel Column Base Plates, by William C. Honeck and Derek Westphal. Dec. '98: Seismic Behavior and Design of Gusset Plates, by Abolhassan Astaneh Asl. Mar. '98: Compatibility of Mixed Weld Metal, by Alvaro L. Collin and James J. Putkey. Aug. '97: Dynamic Tension Tests of Simulated Moment Resisting Frame Weld Joints, by Eric J. Kaufmann. Apr. '97: Seismic Design of Steel Column Tree Moment Resisting Frames, by Abolhassan Astaneh Asl. Jan. '97: Reference Guide for Structural Steel Welding Practices. Electroslag Welding Facts for Structural Engineers, Chambers & Medlock

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Dec. '96: Seismic Design Practice for Eccentrically Braced Frames (Based on the 1994 UBC), by Roy Becker and Mi chael Ishler. Nov. '95: Seismic Design of Special Concentrically Braced Steel Frames, by Roy Becker. Jul. '95: Seismic Design of Bolted Steel Moment Resisting Frames, by Abolhassan Astaneh Asl. Apr. '95: Structural Details to Increase Ductility of Connections, by Omer W. Blodgett. Dec. '94: Use of Steel in the Seismic Retrofit of Historic Oakland City Hall, by William Honeck & Mason Walters. Dec '93: Common Steel Erection Problems and Suggested Solutions, by James J. Putkey. Oct. '93: Heavy Structural Shapes in Tension Applications. Mar. '93: Structural Steel Construction in the '90s, by F. Robert Preece and Alvaro L. Collin. Aug. '92: Value Engineering and Steel Economy, by David T. Ricker. Oct. '92: Economical Use of Cambered Steel Beams. Jul. '92: Slotted Bolted Connection Energy Dissipaters, by Carl E. Grigorian, Tzong Shuoh Yang and Egor P. Popov. Jun. '92: What Design Engineers Can Do to Reduce Fabrication Costs, by Bill Dyker and John D. Smith. Apr. '92: Designing for Cost Efficient Fabrication, by W.A. Thornton. Jan. '92: Steel Deck Construction. Sep. '91: Design Practice to Prevent Floor Vibrations, by Farzad Naeim. Mar. '91: LRFD Composite Beam Design with Metal Deck, by Ron Vogel. Dec. '90: Design of Single Plate Shear Connections, by Abolhassan Astaneh Asl, Steven M. Call and Kurt M. McMullin. Nov. '90: Design of Small Base Plates for Wide Flange Columns, by W.A. Thornton. May '89: The Economies of LRFD in Composite Floor Beams, by Mark C. Zahn. Jan. '87: Composite Beam Design with Metal Deck. Feb. '86: UN Fire Protected Exposed Steel Parking Structures. Sep. '85: Fireproofing Open Web Joists & Girders. Nov. '76: Steel High Rise Building Fire.

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STRUCTURAL STEEL EDUCATIONAL COUNCIL 3650 Mt. Diablo Blvd. – Suite 201 Lafayette, CA 94549 Phone: (510) 835-5035 Fax: (510) 863-5015

Steel

SSEC Officers & Advisory Board ABOLHASSAN ASTANEH-ASL, Ph.D., P.E.; UNIV. OF CALIFORNIA, BERKELEY MICHAEL COCHRAN, S.E.; WIEDLINGER ASSOCIATES, INC. RICH DENIO, S.E.; RUTHERFORD & CHEKENE PATRICK M. HASSETT, S.E.; HASSETT ENGINEERING, INC. BRETT MANNING, S.E.; SCHUFF STEEL CO. KEVIN MOORE, S.E.; SIMPSON GUMPERTZ & HEGER JAY MURPHY; MURPHY PACIFIC CORPORATION RICHARD PERSONS; PERSONS & ASSOCIATE

SSEC Corporate Sponsors: Taylor Devices Intelligent Engineering Contego International

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