FRP-RC Design - Part 3b · 6 BFRP-RC Design - Part 3, (50 min.) This session continues with Basalt...

FRP-RC Design - Part 3b

Steve Nolan

2019

2Professor Brahim Benmokrane, University of Sherbrooke, Quebec, CANADA

Promoting & connecting the Australian Composites Industry – Brisbane, Qld

Composites Australia, December 5, 2018

Design of concrete structures internally reinforced with FRP bars

Canada Research Chair in Advanced Composite Materials for Civil Structures

NSERC/Industrial Research Chair in Innovative FRP Reinforcement for Concrete

Director, The University of Sherbrooke Research Centre on FRP Composites

Department of Civil Engineering

University of Sherbrooke, Sherbrooke, QC, Canada

E-mail:brahim.benmokrane@usherbrooke.ca

Adapted from…

3

Fiber-reinforced polymer (FRP) materials have emerged as analternative for producing reinforcing bars for concrete structures.Due to other differences in the physical and mechanical behaviorof FRP materials versus steel, unique guidance on theengineering and construction of concrete structures reinforcedwith FRP bars is necessary.

Course Description

1

4

• Understand the mechanical properties of FRP bars

• Describe the behavior of FRP bars

• Describe the design assumptions

• Describe the flexural/shear/compression design procedures of

concrete members internally reinforced with FRP bars

• Describe the use of internal FRP bars for serviceability &

durability design including long-term deflection

• Review the procedure for determining the development and

splice length of FRP bars.

Learning Objectives

5

FRP-RC Design - Part 1, (50 min.)

This session will introduce concepts for reinforced concrete design with FRP rebar. Topics will

address:

• Recent developments and applications

• Different bar and fiber types;

• Design and construction resources;

• Standards and policies;

FRP-RC Design - Part 2, (50 min.)

This session will introduce Basalt FRP rebar that is being standardized under FHWA funded project

STIC-0004-00A with extended FDOT research under BE694, and provide training on the flexural

design of beams, slabs, and columns for:

• Design Assumptions and Material Properties

• Ultimate capacity and rebar development length under strength limit states;

• Crack width, sustained load resistance, and deflection under service limit state;

Content of the Course

6

BFRP-RC Design - Part 3, (50 min.)

This session continues with Basalt FRP rebar from Part II, covering shear and axial design of

columns at the strength limit states for:

• Ultimate capacity – Flexural behavior (Session 3a);

• Shear resistance of beams and slabs (Session 3b);

• Fatigue resistance under the Fatigue limit state

• Axial Resistance of columns;

• Combined axial and flexure loading.

FRP-RC Design - Part IV (Not included at FTS - for future training):

This session continues with FRP rebar from Part III, covering detailing and plans preparation:

• Minimum Shrinkage and Temperature Reinforcing

• Bar Bends and Splicing

• Reinforcing Bar Lists

• General Notes & Specifications

Content of the Seminar

7

Session 4: (1:30 pm - 2:30 pm)

Shear behaviour

• - Design philosophy

• - Shear strength

• - Design examples

Session 3b: Shear Behavior

8

400

200

0

600

1200

1000

800

1400

1800

1600

0.0 0.5 1.0 2.0 2.5 3.01.5

Strain (%)

Str

es

s(M

Pa

)

Carbon FRP

Aramid FRP

Glass FRP

Steel

Stress-Strain Relationships for FRP Bars

Session 3b: Shear Behavior

9

Shear Strength of FRP Reinforced Members

• FRP has a relatively low modulus of elasticity

• FRP has a high tensile strength and no yielding point

• Tensile strength of a bent portion of an FRP bar is

significantly lower than a straight portion

• FRP has low dowel resistance

Session 3b: Shear Behavior

10

Shear Strength of FRP Reinforced Members

• Concrete reinforced with FRP has a lower shear strength than concrete with steel reinforcement

• Increased crack width

• Small compressive

zone depth

→ Less aggregate interlocking

→ Less concrete resistance in

the zone compressive

3

Session 3b: Shear Behavior

11

Most of the design codes and design guidelines recommend the following simplified approach for shear design:

Vn = Vcf + Vsf + Vp

where

Vn = nominal shear strength

Vcf = concrete contribution to shear strength

Vsf = shear reinforcement contribution to shear strength

Vp = prestressing resisting component

Session 3b: Shear Behavior

12

Shear transfer mechanism in a cracked

(1) Uncracked

concrete

Applied Load

(3) Arching

action(2) Aggregate

interlock

(4) Residual tensile

stresses

(6) Shear reinforcement

(5) Dowel action

Session 3b: Shear Behavior

13Diagonal tension failure mode

Beam CN-3 Beam GN-3

Shear Behaviour of FRP RC Beams

Session 3b: Shear Behavior

14Size Effect

Session 3b: Shear Behavior

15

Beam B1-1 Beam B1-2

Diagonal Tension Failure Mode

Session 3b: Shear Behavior

16Shear Failure of SC-9.5-2 (CFRP @ d/2)

Shear Behaviour of Concrete Bridge Girders Reinforced with FRP

Stirrups (T-Section) – MTQ Research Project (2007-2009)

17Reinforcing Cage and Concrete Casting

Shear Behaviour of Concrete Bridge Girders Reinforced with FRP

Stirrups (T-Section) – MTQ Research Project (2007-2009)

18Curing and transportation

Shear Behaviour of Concrete Bridge Girders Reinforced with FRP

Stirrups (T-Section) – MTQ Research Project (2007-2009)

19GFRP-Cages

Shear Behaviour of FRP RC Beams

Session 3b: Shear Behavior

20CFRP Stirrups

Shear Behaviour of FRP RC Beams; GFRP & CFRP

Stirrups

Session 3b: Shear Behavior

21Shear Failure of SC-9.5-3 (CFRP @ d/3)

Shear Behaviour of Concrete Bridge Girders Reinforced with FRP

Stirrups (T-Section) – MTQ Research Project (2007-2009)

22Shear Failure of SS-9.5-2 (Steel @ d/2)

Shear Behaviour of Concrete Bridge Girders Reinforced with FRP

Stirrups (T-Section) – MTQ Research Project (2007-2009)

23

416

536

440

376

272300

400

500

600

200

100

0

SS-9.5-2 SC-9.5-2 SC-9.5-3 SC-9.5-4 SG-9.5-2 SG-9.5-3 SG-9.5-4

Fail

ure

Sh

ea

r L

oa

d(k

N)

38%62%

97%

259

5%

24%

337 53%

Shear Capacity

Shear Behaviour of Concrete Bridge Girders Reinforced with FRP

Stirrups (T-Section) – MTQ Research Project (2007-2009)

24

Shear design is similar to the simplified method of CSA A23.3-14, i.e.

Vr ≥ Vc + Vs,F

Vc accounts for

• Shear resistance of uncracked concrete

• Aggregate interlock

• Dowel action of the longitudinal reinforcement

• Arching action

Vs,F = Shear carried by the FRP shear reinforcement

Session 3b: Shear Design (CSA-S806)

25

• However, Vr shall not exceed

' dc f

r ,max c c w v p

M V

M

V 0,22 f b d 0,5V

• For FRP Stirrups

Vr VcVs,F

• For Steel Stirrups

Vr VcVs,F

Session 3b: Shear Design (CSA-S806)

26

If the member effective depth does not exceed 300 mm and there is no axial load:

1/3

)1/3

c m r

'

c w v

f

m

f

f b dc

where

V d

M

k kV 0.05

k 1

kr 1 (EFFw

BUT

c c c w vf ' b dV 0.11

c w vf ' b dVc 0.22c

cf ' 60MPa

or if the member effective depth exceeds 300 mm and transverse

shear reinforcements are equal or greater to Av,min (Clause 8.4.4.8)

Session 3b: Shear Design (CSA-S806)

27

To account for size effect, for sections with an effective

depth greater than 300mm and with less transverse

reinforcement than Av,min

1/3

750

c m r s

'

c w v

s

f b dc

where

k k kV 0.05

k 1450 d

Session 3b: Shear Design (CSA-S806)

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• Shear Carried by Transverse Reinforcement

• For Members with FRP Transverse Reinforcement

• For Members with Steel Transverse Reinforcement

s,FV

s

0.4F AFv fFu dv cot

s,s s

V S Av f ydv cot

fFu shall not be greater than 0.005EF

Session 3b: Shear Design (CSA-S806)

29

• Minimum Shear Reinforcement

• A minimum area of shear reinforcement shall be provided in all regions of flexural members where

Vf > 0.5Vc+ ΦFVp, or Tf > 0.5Tcr.

This requirement may be waived for:•Slabs and footings

•Concrete joist construction

•Beams with total depth not greater than 250 mm

•Beams cast integrally with slabs where overall depth is not greater than

one-half the width of the web or 600 mm.

Session 3b: Shear Design (CSA-S806)

30

• Minimum Shear Reinforcement

• The minimum are of FRP shear reinforcement shall be such that

vF c

Fu

bwsf '

0.4 fA 0.07

fFu shall not be greater than 1200MPa or 0.005EF.

Session 3b: Shear Design (CSA-S806)

31

Session 3b: Shear Design (CSA-S806)

32

Session 3b: Shear Design (CSA-S806)

33

Session 3b: Shear Design (CSA-S806)

34

Session 3b: Shear Design (CSA-S806)

35

Session 3b: Shear Design (CSA-S806)

3629Professor Brahim Benmokrane, University of

Sherbrooke, Quebec, CANADACan ada

Session 3b: Shear Design Example (CSA-S806)

37

Session 3b: Shear Design Example (CSA-S806)

38

Session 3b: Shear Design Example (CSA-S806)

39

Session 3b: Shear Design Example (CSA-S806)

40

Session 3b: Shear Design Example (CSA-S806)

41

Session 3b: Shear Design Example (CSA-S806)

42

Session 3b: Shear Design Example (CSA-S806)

43

Session 3b: Shear Design Example (CSA-S806)

44

Session 3b: Shear Design Example (CSA-S806)

45

Session 3b: Shear Design Example (CSA-S806)

46

Additional Shear Design of Beam

Reinforced with GFRP Bars

According to CSA S806-12

Session 3b: Shear Design Example (CSA-S806)

47

Loads:• Dead load (D.L) = 85 kN/m

• Live load (L.L) = 40 kN/m

Service limit state (Ws.l.s) = 85 + 40 = 125 kN/m

Ultimate limit state (Wu.l.s) = 1.25 * 85 + 1.5 * 40 = 166.25 kN/m

S.L.S U.L.S

V = W L / 2 (kN) 437.50 581.88

M = W L2 / 8

(kN.m)

765.63 1018.28

Session 3b: Shear Design Example (CSA-S806)

48

Session 3b: Shear Design Example (CSA-S806)

49

Session 3b: Shear Design Example (CSA-S806)

50

Design Steps

• Design for shear force

❖ Calculate concrete contribution.

❖ Calculate GFRP stirrups contribution

Session 3b: Shear Design Example (CSA-S806)

51

Session 3b: Shear Design Example (CSA-S806)

52

Session 3b: Shear Design Example (CSA-S806)

53

Session 3b: Shear Design Example (CSA-S806)

54

Session 3b: Shear Design Example (CSA-S806)

55

Session 3b: Shear Design Example (CSA-S806)

56

End of Session

Session 1: Introduction

57

Questions

Raphael Kampmann PhDFAMU-FSU College of Engineering

Tallahassee, FL.

kampmann@eng.famu.fsu.edu

Chase Knight, Ph.D, P.E.

State Materials Office,

Gainesville, FL.

Chase.Knight@dot.state.fl.us

Steven Nolan, P.E.FDOT State Structures Design Office,

Tallahassee, FL.

Steven.Nolan@dot.state.fl.us

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Marco Rossini, PhD studentUniversity of Miami.

Coral Gables, FL.

mxr1465@mami.edu