Rc Design Ppt

MODULE 04 REINFORCED CONCRETE DESIGN & STAAD Pro Allan E. Botuyan, MSCE

OUTLINE 1. INTRODUCTION 2. BEAM DESIGN 2.1. FLEXURE 2.2. SHEAR & TORSION 2.3. DESIGN FOR ANCHORAGE 2.4. STAAD PRO INPUT PARAMETERS 2.5. STAD DESIGN OUTPUT FOR BEAMS 2.6. SEISMIC REQUIREMENTS FOR BEAMS

OUTLINE 3. COLUMN DESIGN 3.1. COLUMN INTERACTION DIAGRAM 3.2. STAAD DESIGN BRIEF FOR COLUMNS 3.3. STAAD DESIGN OUTPUT FOR COLUMNS 3.4 SEISMIC REQUIREMENTS FOR COLUMNS

4. DESIGN IN STAAD PRO

I. INTRODUCTION •

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Analysis part is always followed by the design part. The design of members is based on the critical member forces

I. INTRODUCTION •

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What are the critical member forces use for design? ANALYSIS RESULTS based on loads and load combinations • •

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Vertical loads = dead and live loads Seismic loads = static or dynamic loads • P-delta effects • Horizontal torsional moments • Orthogonal effects Load combinations

I. INTRODUCTION Seismic Loads • P-delta Effects

I. INTRODUCTION P

Δ

P

F

uy

L V=F SECONDARY MOMENT

M =(FL)+(PΔ) R=P

I. INTRODUCTION Δ

Pi = Pd+Pl Vi – story shear

Story height, hi

Vi –story shear

I. INTRODUCTION Seismic Loads P-delta Effects (NSCP 208.5.1.3) 1.

2.

PΔ need not be considered when the ratio of the secondary moment to primary moment is less than 10% PΔ need not be considered when the story drift ratio does not exceed 0.02/R

I. INTRODUCTION Seismic Loads Horizontal Torsional Moments (NSCP 208.5.7) The accidental torsion shall be determined by assuming the mass is displaced 5% of the building width.

I. INTRODUCTION Seismic Loads Horizontal Torsional Moments (NSCP 208.5.7) 0.05L

B

Fz L

I. INTRODUCTION Seismic Loads Horizontal Torsional Moments (NSCP 208.5.7)

Fx

0.05B

B

L

I. INTRODUCTION Seismic Loads Orthogonal Effects (NSCP208.8.1)

Fx B

0.3Fx L

I. INTRODUCTION Seismic Loads Orthogonal Effects (NSCP208.8.1)

0.3Fy B

Fy L

I. INTRODUCTION •

•

note that the initial proportioning of beam and column sizes is part of the design and may not be the final dimension. design is a series of iteration and resizing, then reanalysis, then redesign.

I. INTRODUCTION Design is an iteration process: 1. Initial sizing of beams and columns. 2. Analysis for stresses. 3. Design of steel reinforcements. if design is inadequate, repeat step 1, 2, and 3. 4. If design is adequate, adopt sizes and reinforcements. 5. Apply seismic detailing

I. INTRODUCTION •

•

•

•

All concrete design calculation is governed by the current ACI 318 code. Unified (strength) design method is adopted by the current code. The working stress design (WSD) is deleted from the ACI 318 code STAAD Pro does not employ the WSD for reinforced concrete design.

I. INTRODUCTION •

•

SPECIAL MOMENT RESISTING FRAMES (SMRF) are the type of frames, instead of ORDINARY MOMENT RESISTING FRAMES (OMRF), are required for high seismic risk areas, such as the Philippines. Therefore, the NSCP requires that all buildings in the Philippines must be designed to effectively resist high seismic forces.

I. INTRODUCTION •

At the moment, STAAD Pro has NO provision for automatic seismic detailing in reinforced concrete design.

•

What shall we do????

2. BEAM DESIGN • FLEXURE • SHEAR • TORSION

2. BEAM DESIGN 2.1. FLEXURE The main (longitudinal) reinforcement is calculated for midspan (sagging) and support (hogging) bending moments on the basis of the section profile in the design brief (ie. PRISMATIC ZD, YD).

2. BEAM DESIGN CRITICAL HOGGING MOMENT CRITICAL HOGGING MOMENT

ZONE 1

ZONE 2

CRITICAL SAGGING MOMENT

ZONE 3

2. BEAM DESIGN 2.1. FLEXURE The STAAD Pro does not have any limit of any bars in any one layer as long as the spacing requirements specified in the code are satisfied. The program can handle a maximum of four layers of reinforcement, two layers each at the top and bottom.

2. BEAM DESIGN 2.1. FLEXURE The actual amount of steel required as well as the maximum and minimum required for flexure is shown as ROW, ROWMX AND ROWMIN, respectively. It is important to note that the beams are designed for flexural MZ only. The moment My is not considered in the design.

2. BEAM DESIGN 2.1. FLEXURE MY

h

Top bars (max of 2 layers) MZ

x

bottom bars (max of 2 layers)

y b

2. BEAM DESIGN 2.2. SHEAR & TORSION COLUMN ELEMENT LINE STEEL REINFORCEMENTS

d BEAM ELEMENT LINE SFACE OR EFACE

2. BEAM DESIGN 2.2. SHEAR & TORSION When required, torsional reinforcement in the form of closed stirrups or hoop reinforcement must be provided.

2. BEAM DESIGN 2.2. SHEAR & TORSION

2. BEAM DESIGN 2.2. SHEAR & TORSION In addition to the stirrups, longitudinal steel bars are provided in corners of the stirrups and are well distributed around the section

2. BEAM DESIGN 2.2. SHEAR & TORSION

2. BEAM DESIGN 2.2. SHEAR & TORSION In the ACI Code, the design for torsion is based on space truss analogy. After torsional cracking occurs, the torque is resisted by closed stirrups, longitudinal bars, and concrete compression diagonals.

2. BEAM DESIGN 2.3. DESIGN FOR ANCHORAGE In STAAD output for flexural design, the anchorage requirement is shown with a YES or NO at the START and END of the beam. The designer must provide the details of anchorage.

2. BEAM DESIGN Hook if anchor is YES at START and/or END node Exterior Column face

D

db –bar diameter 4db or 2.5” min

4db 5db 6db

db –bar diameter 12db

Ldh- development length Critical section (eg. Interior column face)

10mm to 20mm (D=6db) 28mm, 32mm, 36mm (D=8db) 43mm, 57mm (D=10db)

2.4. STAAD PRO INPUT PARAMETERS Parameter

Default Value

Description

FYMAIN

* 60,000 psi (414 MPa)

Yield Stress for main reinforcing steel

FYSEC

* 60,000 psi (414 MPa)

Yield Stress for Secondary Steel

FC

* 4,000 psi (28 MPa)

Compressive Strength of Concrete

CLT

*1.5 inch (37.5 mm)

Clear cover for top reinforcement

CLB

*1.5 inch (37.5 mm)

Clear cover for bottom reinforcement

CLS

*1.5 inch (37.5 mm)

Clear cover for side reinforcement

MINMAIN**

#4 (12mm)

Min main reinforcement bar size

MINSEC **

#4 (12mm)

Min secondary reinforcement bar size

MAXMAIN **

#18 (57 mm)

Max main reinforcement bar size

2.4. STAAD PRO INPUT PARAMETERS NSECTION***

12

Number of equally-spaced sections to be considered in finding critical moments for beam design.

TRACK

0.0

BEAM DESIGN: With TRACK set to 0.0, critical moments will not be printed out with beam design report. A value of 1.0 will mean a print out. A value of 2.0 will print out required steel areas for al intermediate sections specified by NSECTION. COLUMN DESIGN: TRACK 0.0 prints out detailed design results. TRACK 1.0 prints out column interaction analysis results in addition to TRACK 0.0 output. TRACK 2.0 prints out schematic interaction diagram and intermediate interaction values in addition to all of the above.

RHOMN

0.01 (1%)

Minimum reinforcement required in a concrete column. ACI code allows 1% to 8%.

EXAMPLE DESIGN BRIEF FOR BEAMS UNIT KN METER START CONCRETE DESIGN CODE ACI 2002 FYMAIN 414 ALL MAXMAIN 20 ALL CLB 40MM DESIGN BEAM 17 10 END CONCRETE DESIGN

EXAMPLE : DESIGN BRIEF FOR BEAMS 



In STAAD Pro V8i (SELECT Series 1), three versions of the ACI Code are implemented: 1999, 2002, and 2005 To access any of the code editions, specify the commands START CONCRETE DESIGN CODE ACI 1999 (for 1999) or CODE ACI 2002 (for 2002) or CODE ACI (for 2005)

2.5. SAMPLE STAAD BEAM DESIGN OUTPUT BEAM NO. 97 DESIGN RESULTS - FLEXURE PER CODE ACI 318-05 LEN - 5000. MM FY - 275. FC - 21. MPA, SIZE - 300. X 400. MMS LEVEL HEIGHT BAR INFO FROM TO ANCHOR (MM) (MM) (MM) STA END _________________________________________________________ 1 54. 5 - 12MM 802. 3989. NO NO 2 342. 4 - 20MM 0. 1484. YES NO 3 342. 4 - 20MM 3308. 5000. NO YES __________________________________________________________ Override these values if longitudinal reinforcement for torsion is required.

Check the output if ACI318-05 to comply with NSCP 2010

2.5. OUTPUT OF BEAM DESIGN (SHEAR and TORSION)

This is not final. To be checked against seismic provisions

B E A M N O. 97 D E S I G N R E S U L T S - SHEAR AT START SUPPORT - Vu= 68.16 KNS Vc= 81.19 KNS Vs= 9.70 KNS Tu= 0.34 KN-MET Tc= 2.9 KN-MET Ts= 0.0 KN-MET LOAD 4 NO STIRRUPS ARE REQUIRED FOR TORSION. REINFORCEMENT IS REQUIRED FOR SHEAR. PROVIDE 10 MM 2-LEGGED STIRRUPS AT 178. MM C/C FOR 2158. MM ADDITIONAL LONGITUDINAL STEEL REQD. FOR TORSIONAL RESISTANCE = 0.00 SQ.CM.

AT END SUPPORT - Vu= 70.66 KNS Vc= 81.19 KNS Vs= 13.03 KNS Tu= 0.34 KN-MET Tc= 2.9 KN-MET Ts= 0.0 KN-MET LOAD 4 NO STIRRUPS ARE REQUIRED FOR TORSION. REINFORCEMENT IS REQUIRED FOR SHEAR. PROVIDE 10 MM 2-LEGGED STIRRUPS AT 178. MM C/C FOR 2158. MM ADDITIONAL LONGITUDINAL STEEL REQD. FOR TORSIONAL RESISTANCE = 0.00 SQ.CM.

2.6. SEISMIC REQUIREMENTS FOR BEAMS Since the Philippines is located in a high seismic risk region, adopting the SMRF (Special Moment Resisting Frame) is a must. Therefore, a special detailing for seismic requirement shall is required. Unfortunately, STAAD Pro at the moment does not have the facility for seismic detailing.

2.6. SEISMIC REQUIREMENTS FOR BEAMS

At this point the design output of STAAD Pro is compliant to ACI Code 318-08 or the NSCP 2010, EXCEPT FOR THE SEISMIC DETAILING requirements.

2.6. SEISMIC REQUIREMENTS FOR BEAMS Flexural Members shall satisfy the following: (ACI 318-08 Section 21.3.1 or NSCP 421.5.1) 1. Clear span shall not be less than four (4) times the effective depth. 2. The width-to-depth ratio , b/d, shall not be less 0.3. 3. The width shall not be less than 250mm 4. The width, bs, of the supporting member plus distances on each side of the supporting member not exceeding ¾ of the depth of the flexural member.

Longitudinal reinforcement requirements (ACI code Section 21.3.2 / NSCP 421.5.1) 1. Longitudinal reinforcement for both top and bottom steel (A) should be in the range defined as follows: 3 fc' bd fy 200 bd fy

A 0  025 bd

Longitudinal reinforcement requirements (ACI code Section 21.3.2 / NSCP 421.5.1) 2. The positive moment strength at joint face should be greater or equal ½ the negative moment strength at the face of the joint

ϕMnL-

ϕMnL+ ≥ 1/2 (ϕMnL- )

ϕMnR-

ϕMnR+ ≥ 1/2 (ϕMnR- )

Longitudinal reinforcement requirements (ACI code Section 21.3.2 / NSCP 421.5.1) 3. Neither the negative nor the positive moment strength in any section along the member should be less than ¼ the maximum strength provided at the face of either joint. ϕMnL- max

ϕMany section ≥ 1/4 (ϕMnL- max )

Longitudinal reinforcement requirements (ACI code Section 21.3.2 / NSCP 421.5.1) 4. Lap splices of flexural reinforcement are permitted only if hoop reinforcement is provided over the lap length. Maximum spacing of transverse reinforcement enclosing the lapped bars shall not exceed 100mm.

Longitudinal reinforcement requirements (ACI code Section 21.3.2 / NSCP 421.5.1) Lap splices shall not be used: a. Within the joint. b. With a distance of twice the member depth from the face of the joint; and c. At locations where analysis indicates flexural yielding (ie. Location of plastic hinges)

Transverse reinforcement requirements (ACI code Section 21.3.3 / NSCP 421.5.3) For SMRF, plastic hinges will form at the ends of flexural members. Those locations should be specially detailed to ensure sufficient ductility. Yield may occur

1.

h

2h

2h

2h

2h

Transverse reinforcement requirements (ACI code Section 21.3.3 / NSCP 421.5.3) 2.

Spacing of hoops should not exceed the following: a. d/4 b. 8 x diameter of the smallest longitudinal bars. c. 24 x diameter of hoop bars. c. 300 mm First hoop shall be located not more than 50mm from face of support.

Transverse reinforcement requirements (ACI code Section 21.3.3 / NSCP 421.5.3) 3. Where hoops are not required, stirrups with seismic hooks shall be spaced at a distance not more than d/2 throughout the length of the member.

SPECIAL DETAILING ON TRANSVERSE REINF. Hoop spacing is smallest of: d/4 ; 8db ; 24 hoop db ; 300mm ; STAAD Pro output

hoops

hoops

hoops

h

Spacing of stirrups ≤ d/2 50mm max 2h

50mm max 2h

50mm max 2h

Sample of design output from STAAD Pro 56J

5000 X 300 X 400

4No20 H 342. | 0 TO 1484 14*10c/c 178

58J

4No20 H 342. | 3308 TO 5000 14*10c/c178

5No12 H 54. | 802 TO 3989

Physical representation 1484

1692

342 4-20mm

4-20mm 14 hoops @10mm@ 178 o.c.

400 5-12mm

14 hoops of 10mm@ 178 o.c.

54 1102

802

5000

Beam Detail With Seismic Provision From STAAD 50mm max

800mm S=80mm 4-20mm 2-12mm

50mm max 2900 S=178mm

2-20 mm

800mm S=80mm 4-20mm

400 5-12mm

2-12mm

10mm hoops / stirrups

b

b 5000

Hoop spacing is smallest of : d/4 ; 8db ; 24 hoop db ; 300mm and STAAD Pro

Beam Detail With Seismic Provision From STAAD 50mm max 2900 S=178mm

800mm S=90mm 4-20mm 2-12mm 2-20mm

50mm max

2-20 mm

800mm S=90mm 4-20mm

400 5-12mm 2-20mm

2-12mm 2-20mm

10mm hoops / stirrups

b

b 5000

Bottom bars of 5-12mm < 2-20mm

Hoop spacing is smallest of : d/4 ; 8db ; 24 hoop db ; 300mm and STAAD Pro

3. COLUMN DESIGN Column design in STAAD per the ACI code is performed for axial force, uniaxial and biaxial moments. The loading which produces the largest amount of reinforcement is called the critical load.

3. COLUMN DESIGN

Column design is done for square, rectangular and circular sections. For rectangular and circular sections, reinforcement is always assumed to be equally distributed on all faces. This means that the total number of bars will always be a multiple of four (4).

Column design inside the STAAD program 1. The Bresler Load Contour method is adopted by STAAD Pro for columns under axial force, uniaxial and biaxial moments. 2. The program will iterate a steel ratio from 1% to a maximum of 8% for a given column dimension. 3. When the adequate steel ratio is arrived at, the iteration terminates and adopts the steel ratio and then a steel area is computed.

Column design inside the STAAD program 4. Otherwise, if the section is inadequate, the report prompts that the size needs to be increased. 5. Seismic provision is absent in STAAD Pro. Thus the output must be checked and adjusted accordingly.

3.1. COLUMN INTERACTION DIAGRAM

Axial capacity (kN)

Nominal Pn, Mn curve Factored Pu, Mu (ACI Capacity) SAFE ZONE for(Pu, Mu) pair

Moment Capacity (kN-m)

3.2. STAAD DESIGN BRIEF FOR COLUMNS UNIT KN METER START CONCRETE DESIGN CODE ACI FYMAIN 414 MAXMAIN 25 ALL DESIGN COLUMN 23 25 END CONCRETE DESIGN

3.2. STAAD DESIGN BRIEF FOR COLUMNS The following output is generated without any TRACK definition, thus using the default of TRACK 0.0 ========================================================== COLUMN NO. 1 DESIGN PER ACI 318-05 - AXIAL + BENDING FY - 415.0 FC - 25.0 MPA, RECT SIZE - 300 X 450 MMS, TIED AREA OF STEEL REQUIRED = 882.8 SQ. MM BAR CONFIGURATION REINF PCT. LOAD LOCATION PHI --------------------------------------------------------------------------------------------------------8 - 12 MM 1.097 4 END 0.650 (PROVIDE EQUAL NUMBER OF BARS ON EACH FACE) TIE BAR NUMBER 12 SPACING 192.00 MM

3.4. SEISMIC REQUIREMENTS FOR COLUMN 1. Longitudinal Reinforcements (NSCP 2010, 421.6.3.1) • The reinforcement ratio g shall not be less than 0.01 and shall not exceed 0.06. •

The STAAD allows up to a maximum of 8%. Therefore, should the design be adequate with a steel ratio more than 6%, the section size shall be increased in order to satisfy a steel ratio of less than or equal to 6%.

3.4. SEISMIC REQUIREMENTS FOR COLUMN Flexural Strength (NSCP2010 421.6.1) The flexural strength of the column should satisfy the following: ∑Mnc ≥ (6/5) ∑Mnb Where: ∑Mnc - the sum of nominal flexural strengths of columns framing into the joint, evaluated at the faces of the joint. ∑Mnb - the sum of nominal flexural strengths of the beams framing into the joint, evaluated at the faces of the joint.

3.4. SEISMIC REQUIREMENTS FOR COLUMN Mnctop

Mnbleft

Mnbright

Mncbot

(Mnctop + Mncbot) ≥ (6/5) (Mnbtop + Mnbbot) sum of column moment capacity must be 20% higher than the sum of the beam moment capacity

3.4. SEISMIC REQUIREMENTS FOR COLUMN 2. Limiting size of columns (NSCP2010 421.6.1) • The shortest cross-sectional dimension, measured on a straight line passing through the geometric centroid, shall not be less than 300mm. (Sec 421.6.1.1)

300mm

300mm

300mm

450mm

3.4. SEISMIC REQUIREMENTS FOR COLUMN 2. Limiting size of columns (NSCP2010 421.6.1) • The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall not be less than 0.4. (Sec 421.5.1.2) hx > 0.4bx

bx

3.4. SEISMIC REQUIREMENTS FOR COLUMN 3. Transverse reinforcement spacing (NSCP2010, 421.6.4.3) 1. ¼ of the minimum member dimension. 2. Six times the diameter of the longitudinal bar, and 3. as defined by the given equation. So = 100 + (350-hx) 3 where 100mm < So < 150mm hx = spacing of additional cross ties or overlapping hoops, which need not exceed 350mm on centers.

3.4. SEISMIC REQUIREMENTS FOR COLUMN 3. Transverse reinforcement spacing (NSCP2010, 421.6.4.3) h

b/4 hx b hx

s≤ 100+ (350- hx) 3 where 100mm < s