Design Standards for Railway Structures and Commentary(Concrete Structures) 2007-03(OCR)

CONTENTS I DESCRIPTION OF THE CONCRETE STANDARD .............................................................................. 1 II A BRIEF HISTORY OF REVISIONS OF THE DESIGN STANDARD .................................................. 1 III VERIFICATION PROCEDURE IN THE CONCRETE STANDARD ..................................................... 3 IV SUMMARY OF THE CONCRETE STANDARD .................................................................................... 3 1. General ................................................................................................................................................ 3 2. Basis of Design .................................................................................................................................... 4 3. Required Performance and Performance Verification of Structures .................................................... 4 4. Actions ................................................................................................................................................. 6 5. Materials .............................................................................................................................................. 9 6. Computation of Response Values ...................................................................................................... 11 7. Verification of Safety ......................................................................................................................... 12 8. Verification of Serviceability ............................................................................................................. 14 9. Verification of Restorability .............................................................................................................. 14 10. Assessment of Durability .................................................................................................................. 16 11. Prerequisite of Verification ................................................................................................................ 18 12. Construction and Maintenance .......................................................................................................... 18 13. Members ............................................................................................................................................ 18 14. Structures .................... :...................................................................................................................... 18 15. Structural Details ............................................................................................................................... 19 16. Bearings ............................................................................................................................................. 19 17. Appendices ........................................................................................................................................ 20 V VERIFICATION EXAMPLES, DESIGN GUIDEBOOKS, AND VERIFICATION SOFTWARE ........ 20 1. Verification Examples ....................................................................................................................... 20 2. Design Guidebook ............................................................................................................................. 20 3. Verification Software ......................................................................................................................... 21

OUTLINE OF DESIGN STANDARDS FOR RAILWAY STRUCTURES AND COMMENTARY (CONCRETE STRUCTURES) DESCRIPTION OF THE CONCRETE STANDARD The latest edition of the "Design Standards for Railway Structures (Concrete Structures)" was published in April 2004, hereinafter referred to as the "2004 edition standard." The previous standard was revised to the 2004 edition standard in order to follow the conversion to performance-based regulations of the code provisions of the national technical norm; "Ministerial ordinance that stipulates technical standards pertaining to railways." The 2004 edition standard has been used for the design of railway structures throughout Japan. The highlights of the revision to the 2004 edition standard are (1) the adoption of a performance-based design method, (2) the extension of the applicability of high-strength materials, and (3) the adoption of the latest durability improvement technologies. Some of the latest concrete technologies are also incorporated. The 2004 edition standard has 16 chapters. The standard also includes several appendices that summarize the results of the technical studies conducted for the revision. Table 1 shows the table of contents of the standard. Table 1 Contents of Design for Railway Structures (Concrete Structures) Chapter No. 1 2

3 4 5 6 7 8

II

Title General Basis of Design Required Performance and its Verification for Structures Actions Materials Computation of Response Values Verification of Safety Verification of Serviceability

I

Chapter No. 9 10

I

Title Verification of Restorability Assessment of Durability

11

Prerequisite of Verification

12 13 14 15 16

Construction and Maintenance Members Structures Structural Details Bearings Appendices

A BRIEF HISTORY OF REVISIONS OF THE DESIGN STANDARD

Before 1955, the Standard Specifications for Concrete Structures written by the Japan Society of Civil Engineers had been applied to the design of railway concrete structures. The Design Standards for Civil Engineering Structure (Plain and Reinforced Concrete) was issued in 1955 from the Japanese National Railways. The exclusive design standards for railway structures have been used ever since and they have been revised successively as shown in Table 2. Some special design standards have been issued and used for the design of the Tokaido Shinkansen's structures and the design of prestressed concrete bridges. A new Design Standard for Railway Structures was issued in 1970 incorporating these precursory standards. The design standards were revised several times by the Japanese National Railways on the basis of the allowable stress design method until 1983. After the privatization of the Japanese National Railways in 1987, the code provisions (code texts) of the design standard have been treated as ministerial notifications and published by the government (Railway Bureau of the Ministry of Transport, currently Ministry of Land, Infrastructure and Transport). Then, combining the code provisions, commentaries and appendices, the Design Standards for Railway Structures and Commentary have been published as a technical textbook within six months to one year after the notice. Under this new system, the first design standard to use the limit state design method was formulated. It was published as the "Design Standard for Railway Structures and Commentary (Concrete Structures)" in October 1992, hereinafter referred to as the" 1992 edition standard." This involved a major revision work - 1-

from the previous edition of the design standard which had been coded based on the allowable stress design method. The 1992 edition standard was revised to adopt SI units in 1999 with no other changes. The 1992 edition standard was applied to all the designs of railway concrete structures (reinforced and prestressed concrete) in Japan when they were designed based on the ultimate limit state design method. The 1992 edition standard covered and provided seismic design provisions. These provisions, however, were superseded by the corresponding provisions specified in the "Design Standards for Railway Structures and Commentary (Seismic Design)," hereinafter referred to as the "seismic standard," which incorporated experiences learned from the 1995 Hyogoken-Nanbu Earthquake. Table 2 History of Revisions of DeSign Standards for Railway Concrete Structures

Revision Year 1955 1961 1965 1970 1972 1974

Design Standards Design Standard for Civil Engineering Structures (Plain and Reinforced Concrete) Design Standard for Shinkansen Structures Design and Construction Standards for Prestressed Concrete Railway Bridges Design Standard for Reinforced and Plain Concrete Structures, Design Standard for Prestressed Concrete Railway Bridges Design Standard for Shinkansen Network Structures (Joetsu, Tohoku and Narita Shinkansens) Design Standard for Railway Structures (Revised)

Design Method/System

Allowable stress design method

_____ }J..~~ ______ R~~~g~ _~t_ap'~,!~~ f9!}3·~i!'Y~Y- ~~~~!t!~~~ {!\~,::i~~ftJ __________________________________________________________ _ 1991 1992 1999

Design Standard for Railway Structures (Concrete Structures), Notice issued from the Ministry of Transport Design Standard for Railway Structures and Commentary (Concrete Structures) SI Unit Edition, Design Standard for Railway Structures and Commentary (Concrete

Limit state design method (specification-based)

________________ ~t~9!~~~~1 _______________________________________________________________________________________________ _ 2004

Design Standards for Railway Structures (Concrete Structures), Ministry of Land, Infrastructure and Transport Notice Design Standards for Railway Structures and Commentary (Concrete Structures)

Performance-based design method

The following describes the background to the latest revisions in the 2004 edition standard. In December 2001, a national technical norm "Ministerial Ordinance that Stipulates Technical Standards Pertaining to Railways," was converted from the conventional specification-based format to the performance-based one. It had been almost a decade since the last revision, i.e. the 1992 edition standard. The Standard Specifications for Concrete Structures of the Japan Society of Civil Engineers, hereinafter referred to as the "JSCE Specifications," which is the model code of the railway design standard, was revised adopting the performance-based design method in 2002. The above-mentioned seismic standard, formulated in 1999, had already adopted the performance-based design scheme that demands to verify the required seismic performance when the structure is subj ected to the design seismic motion. Therefore, the' 2004 edition standard was expected to adopt the performance-based design scheme to ensure conformity with these associated ordinances and standards. On the other hand, the research on high-strength concrete and reinforcing bar has advanced and fundamental technical data has been sufficiently collected to be reflected in the provisions of the design standard. The necessity of practical prescriptions on the durability improvement technologies for concrete structures has also been deeply recognized. Therefore, the content of associated provisions of the standard had to be substantiated with these technical developments and other advanced technologies. In July 2000, the Ministry of Transport formed the "Committee on Design Standards for Railway Concrete Structures," appointing the Railway Technical Research Institute as the organizing secretariat. University professors and railway engineers, specialists in the design of concrete structures, were called together and three years were spent discussing how to determine the code provisions. Based on the deliberations of this committee, the Ministry of Land, Infrastructure and Transport noticed the "Design Standards for Railway Structures (Concrete Structures)" in March 2004. The "Design Standard for Railway Structures and Commentary (Concrete Structures)" was published in April of the same year - 2-

being added commentaries and appendices to the governmental notice.

III

VERIFICATION PROCEDURE IN THE CONCRETE STANDARD

Figure 1 shows the schematics of the verification procedure according to the performance-based design method. The left side of Figure 1 shows processes up to computation of the design response value I Rd • The target structure is subjected to structural analysis under the design load F d, that is obtained by multiplying the load factor Yf with the characteristic value of load Fb to obtain the response value IR of the structure or member. Then, the design response value I Rd can be obtained by multiplying the response value with structural analysis factor Ya. On the other hand, the right side of Figure 1 shows processes up to computation of the design limit value I Rd • The design strength of materialfd is obtained by the characteristic value of material strengthfk divided

by the material factor Ym, which is determined according to the material used. In the computation formula for the limit value, this design strength of material fd is used to obtain the limit value I L , and design limit value hd can be obtained by dividing the limit value by the member factor Yb. Verification of performance involves confirming that the result of multiplying this design response value I Rd with the structure factor Yi and then dividing the result by the design limit value hd is less than or equal

to 1.0. If this condition is satisfied, it is assumed that performance is ensured, and this completes design. Design response value Characteristic value of action Fk Action [ . -__Yf_a_c_tio_n_f_a_ct_o_r"--_ _ _ _ _----,.

Design limit value Characteristic value of material strength A .-"tJ_m_m_a_te_fl_·a_If_a_ct_o_r-.:..._ _ _ _ _ _---,

Material

Design strength of materials id=ik IYm

Design action Fd=yf • Fk r - - - - - - - - - - - - - - - -

J

Response analysis --- ------------------------, Response value IR (Fd)

Limit value h ifd)

Computation Ya structural analysis factor of response value Design response value hd=Ya • IR (Fd)

Yb member factor

J

Limit value

Design limit value ILd=hifd) IYb

Figure 1 Basic Performance Verification Procedure

IV SUMMARY OF THE CONCRETE STANDARD The following describes an overview of the code provisions and commentaries of each chapter in the 2004 edition standard. The following description makes no particular distinction between the code provisions of the standard and their commentaries.

1. General "General" specifies the scope of application, definitions of terms and notations. The scope of application is prescribed as "It shall be in accordance with these provisions when verifying the performance of reinforced concrete and prestressed concrete railway structures." "Definitions" describes approximately 130 terms that are associated with concrete and that are important in -3-

performance-based design such as the following examples. The series of activities up to creation of the form of a structure, that is Design: planned with the required performance borne in mind, verification of performance, and drafting of a design drawing. The determination of the actual shape and dimensions of a structure. Structural design: Required performance: The performance that is requited of a structure Verification: The act of evaluating whether or not a structure, members or materials satisfy the required performance 2. Basis of Design "Basis of Design" specifies the fundamental design philosophies. These include the purpose of the design, construction and maintenance conditions that are the prerequisites of design, and the design life. (1) The purpose of the design is prescribed as "The railway structure must comply with its purpose, and must be safe and economical." It is often difficult to repair, strengthen, and improve concrete structures. So the purpose of design states that sufficient surveys must be performed at the beginning of the design stages, and those events that may occur during the service period be reliably forecasted. This makes it possible to design a structure that is durable and easy to maintain. (2) Conditions of maintenance are prerequisites of design. Therefore, maintenance of structures must be made to be as easy as possible. In a normal environment, materials degradation must be examined in the design stage so as not to become conspicuous during the design life. Periodic inspections should be planned as mainly visual observations. (3) The design life of a structure is defined as "the specified life time in terms of the design in which the structure or members upon their use must sufficiently fulfill the target functions," and is prescribed as "it should be determined taking into consideration not only the service period (which often is not be prescribed in the design stage) that is required of a structure, but also maintenance methods, environmental conditions, life cycle costs, etc." Under normal environmental conditions, 100 years is considered a standard design life. This assumes that appropriate inspection and maintenance are performed. The design life can be set to 100 years or longer when materials have high durability. Also a period shorter than 100 years can be set for structures in corrosive environments, such as environments subject to chloride induced deterioration. 3. Required Performance and Performance Verification of Structures "Required performance and performance verification of structures" specifies the type of required performance, performance items and verification indices, principles and methods of performance verification, and safety factors. (1) Performance verification of a structure is prescribed as "to verify that required performance is satisfied by setting the required performance corresponding to the purpose of use, and by using appropriate verification indices." Performance must be expressed by indices that can be evaluated quantitatively. The design standard explains computation methods for indices that can be evaluated by current technology. The following are advantages of introducing performance-based design methods. a) Flexible adaptation to new technologies and individual circumstances: The designer has more freedom to introduce the latest technology and adapt to unique circumstances. b) Disclosure of performance associated information: The performance of the structure is clearly indicated, making it easier for the general public to understand whether or not required

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performance is satisfied. c) Evaluation of life cycle costs: Evaluation of life cycle costs can also be predicted by evaluating performance not only during but also after construction. (2) The three required performances of safety, serviceability and restorability of structures are defined as follows. a) Safety: Performance to prevent any threat to the lives of people using the structure and those surrounding it under all anticipated loads. Not only the structural safety but also the functional safety of structures is prescribed. b) Serviceability: Performance of the structure so that it may be used comfortably by the people, using the structure and those surrouding it under anticipated loads. Functional performance required of the structure is also included. c) Restorability: Performance to allow a structure to be easily restored under anticipated loads when the structure has been subjected to damage. "Safety" includes "ultimate limit states" and "fatigue limit states" in conventional limit state design methods. Likewise, "serviceability" corresponds to "serviceability limit states." "Restorability" is a required performance that has been incorporated from the seismic design. (3) Table 3 shows a summary of required performances, perfornlance items, examples of verification indices, and action to be considered. Table 3 Required Performances, Performance Items, Examples of Verification Indices, and Action to be Considered Required Performance

Performance Item Failure Fatigue failure

Safety

Running safety Public safety* 1

Serviceability

Riding comfort Aesthetic appearance* 1 Watertightness * \ N oise/vibration·\

Verification Indices Force, displacement!deformation Force, stress intensity, number of repeats Disp lacement!deformation Carbonation depth, chloride ion content Displacement!deformation Crack width, stress Crack width, stress intensity Nose level, vibration level

Actions to be Considered • All actions and their repetitions that occur during the design life*2 • Accidental actions having a low frequency of occurrence but a large influence *3

• Large actions that occur relatively frequently during the design life

• Actions that occur during the design life • Accidental actions having a low frequency of occurrence but a large influence *3 * 1: Performance items that are set up as necessary, *2: ActIons that are conSIdered III the venficatIOn of fatIgue failure are specified separately considering characteristics of variation, *3: Actions that are considered as necessary Restorability

Damage

Displacement!deformation, force, stress

(4) "Durability" is defined as the "resistance against variations in the performance of structures or members due to variations in material characteristics (material deterioration) that occur with the passage of time." This does not include fatigue caused by external forces, such as train loads. "Durability" is not, however, an independent required performance. It is an item that should be taken into consideration at all times when evaluating performance, factoring in materials deterioration. Therefore, it is a basis of verification of all required performances taking the durability into consideration. As it is described above, the material degradation must be taken into consideration in every verification of required performance. However, "methods of performing verification without taking materials deterioration into consideration in a positive manner" also is prescribed as a realistic method at the current technical level, presuming that the material deterioration will be kept within a certain range. In this case, it is assumed that the reinforcing steel will not corrode during the design life. (5) Five safety factors are used: load factor Yf, structural analysis factor Ya, material factor Ym, member

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factor Yb, and structure factor Yi. These safety factors are defined as follows. The safety factors shown in Table 4 are used as standard values. Action factor, Yf:

Safety factor considering unfavorable deviations from the characteristic value of, uncertainty in evaluation of action, changes in actions during the design life, influence of nature of actions on limit states, and variations of environmental actions.

Structural analysis factor, Ya: Safety factor considering uncertainty in structural analysis. Material factor, Ym: Safety factor considering unfavorable deviations of material strengths from the characteristic values, differences of material properties between test specimens and actual structures, influence of material properties on specific limit states, and time dependent variations of material properties. Member factor, Yb: Safety factor considering uncertainty in computation of limit values of member performance, effect of scatter of dimensional error of members, the importance of members which reflects the influence on the overall structure when the member reaches a certain limit state. Structure factor, Yi: Safety factor considering relative importance of the structure, as determined by the social impact when the structure reaches the limit state. Table 4 Standard Values for Safety Factors

~ Required Performance

Safety (failure, running safety) for other than seismic design Safety (failure, running safety) for seismic design

Action factor, Yf

Structural analysis factor, Ya

Material factor, Ym for for steel concrete Ys

Member factor, Yb

Structure factor, Yi

Yc

1.0'"'-' 1.2 (0.8'"'-' 1.0) *1

1.0

1.3

1.0 (1.05)*2

1.1 (1.2'"'-'1.3)*3

1.0*4'"'-'1.2

1.0

1.0

1.3

1.0

1.0 (1.1 '"'-'1.3)*5

1.0

Safety (fatigue failure)

1.0

1.0

1.3

1.05

1.0'"'-' 1.1 (1.3)*3

1.0'"'-' 1.1

Serviceability (aesthetic appearance, riding comfort)

1.0

1.0

1.0

1.0

1.0

1.0

Restorability (damage)

1.0

1.0

1.3

1.0

1.0 (1.1 '"'-'1.3)*5

1.0*4'"'-'1.2

*1 *2 *3 *4 *5

4.

Values III parentheses ( ) are applIed when the smaller is dIsadvantageous. Values in parentheses ( ) are applied to steel materials used for stoppers. Values in parentheses ( ) are applied to computation of the shear and torsion capacities depending on the concrete strength. In the case of a "permanent action + primary variable action + secondary variable action," it is generally recommended to set this value to 1.1 or lager. Values in parentheses ( ) are applied to computation ofthe shear capacity.

Actions

"Actions" specifies kinds of actions, characteristic values, action factors, the basic philosophy on the combinations of design actions, and practical design values of actions. Basically, action is the equivalent of "load" specified in the previous edition standard which adopted conventional limit state design methods. The characteristic values of actions are a) dead load, b) train load, c) impact load, d) centrifugal load, e) train lateral load and wheel lateral force, t) breaking force· and traction force, g) track-work vehicle load, h) sidewalk live load, i) continuous welded rail normal force, j) prestressing force, k) effect of shrinkage of concrete and creep, 1) effect of temperature changes, m) soil pressure, n) hydrostatic water pressure, fluid stream force and wave force, 0) wind load, p) snow load, q) effect of earthquakes, r) ground displacement and effect of support drift, s) construction stage loads, t) automobile collision loads, u) effect of environment, and v) other actions. The following describes the changed contents and characteristic points of "actions."

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(1) The term "action" has been commonly used in place of the term "load." This is for a number of reasons as follows. In dynamic analysis and non-linear analysis used in design, there is an increase in the number of cases where modeling to equivalent weight and force is skipped and instead their effect is directly computed in the analysis to obtain response values. In durability checks, it is necessary to place the effect of environment as one of the actions on a structure. The word "action" was adopted after the IS02394: 1998 (General principles on reliability for structures) and the "Basis of Design Associated with Civil Engineering Structures and Architectures" issued by the Ministry of Land, Infrastructure and Transport that were published to lead international standardization of associated technology. "Action" and "load" are defined in the 2004 edition standard as follows: Action: Overall operation to make the stress, the fluctuation of deformation, and aging associated with changes in material properties of structures and members. Load: Of the various actions, those that are modeled as weight or force in order to be taken into consideration in design Figure 2 shows the relationship between action and load. The term "load" is used in the "effects of gravity," such as "dead load" and "train load" that are usually modeled and substituted as weight and force, as well as the "effect of train running," such as "impact load" and "centrifugal load." Actions ___- - - Loads _ _--...... Actions that are turned into weight and force models: -Dead load -Train load -Impact load -Centrifugal load -Continuous welded rail normal force -Prestress force -Earth pressure

- Effect of concrete shrinkage - Effect of concrete creep - Effect of temperature changes - Effect of earthquakes - Effect of environment

Figure 2 Relationship between Action and Load

(2) In a combination of actions, there are two kinds of variable actions, "primary" and "secondary," that are used in combination with permanent action. The characteristic value of primary variable action is defined as the expected value of the maximum value. Appropriate value must be determined for the characteristic value of the secondary variable action depending on the combination with the primary variable action or the accidental action. An accidental action is an action that occurs rarely during the design life, but has serious consequences once it occurs. When the accidental action is combined with a variable action, the variable action should be, in general, taken as a secondary variable action. The performance item that the variable action needs not be distinguished between "primary" and "secondary" is simply treated and expressed as "variable action." Table 5 shows the basic combinations of design actions.

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Table 5 Basic Combinations of Design Actions Required Performance

Performance Item

Combinations of Actions Permanent action + primary variable action + secondary variable action Permanent action + primary variable action + secondary variable action Permanent action + variable action Permanent action + variable action Permanent action + primary variable action + secondary variable action

Failure Safety

Fatigue failure Running safety

Serviceability

Riding comfort Aesthetic appearance

Permanent action + variable action

Restorability

Damage

Permanent action + variable action Permanent action + primary variable action + secondary variable action

(3) The following describes a standard train load that was newly stipulated and an impact load that was revised in characteristic values of action. a) The H-load that conforms to the axial length and train length of an actual Shinkansen train was newly added as a standard train load (see Figure 3). The quantity of the wheel load used in the H-load, which alternates depending on the type of railway vehicle, is chosen taking also into consideration the passenger capacity and the passenger load factor that depend on the future transport demand, and characteristics of the line.

l-_ ~-~__---~-~:l--~~----___---~~-_J[--~_~. 14

Im4

15.0 25.0m

.!~4

5.0 Jl·5.14 .1 4

15.0 25.0m

.IJJJ~lm

.1

Figure 3 H-Ioad

b)

The running of a train induces dynamic response to structures. The ratio between dynamic response to the increase in static response of stress or deflection caused by dynamic response is called the "impact factor." In design, the design impact factor i configured as shown in equation (1) is multiplied by the train load. i=(1 +ia)(1 +ic) - 1 (Eq. 1) where, ia= impact factor of speed effect, ic= impact factor of vehicle motion In the 2004 edition standard, the impact factor of the speed effect ia is presented using numerical table, that was computed using the speed parameter a (=V/(7.2nLb)) and Lb/Lv (V= maximum velocity of train (km/h), n= fundamental natural frequency of members, Lb= span of members, and Lv= length of a vehicle), to deal with the higher speed of trains and the lower rigidity of structures (see Figure 4).

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.,li

.,li

i:i