Compressive Membrane Action in Concrete Decks

1 Titel van de presentatie

Compressive Membrane Action in Concrete Decks

9th fib International PhD Symposium in Civil Engineering

Karlsruhe Institute of Technology (KIT), Germany

Sana Amir 24-07-2012

Prof. Dr. ir. J. C. Walraven, Dr. ir. C. van der Veen

Structural Engineering / Concrete Structures


Contents

1: Introduction: Compressive Membrane Action

2: CMA in reinforced concrete decks - Flexural load carrying capacity - Punching Shear capacity 3: Application of CMA theories to experimental data 4. CMA in transversely prestressed concrete decks : Investigating Punching Shear capacity 5. Future Tests 6. Conclusions


Introduction

Compressive Membrane Action

CMA is a phenomenon that occurs in slabs whose edges are restrained against lateral movement by stiff boundary elements. This restraint induces compressive membrane forces in the plane of the slab (Park and Gamble, 1980).


• Bridges are traditionally designed to carry the wheel load entirely in

flexure.

ASSUMPTION: Adequate shear capacity.

• A bridge deck slab designed for bending tends to fail in the punching

shear mode at a load much higher than that based on flexure.

• Considerable research is done on reinforced decks. Prestressed decks

need to be investigated.

Introduction

Compressive Membrane Action

?

PhD Research


ka = 8/L and kb = 4/L

CMA in reinforced concrete decks

Flexural Capacity by Rankin and Long

acityArchingCapMarc

acityBendingCapMb

)( barcflx MMkP


Kirkpatrick, Rankin, Long, Taylor’s Approach

UK HIGHWAY AGENCY STANDARD BD 81/02

/ 0.251.52( ) (100 )p c eP d d f Q

Punching Shear Capacity

/ 2

2320 0.75

ce

kf hQ

d


• Modified form of Kinnunen – Nylander Model.

Limitation:

Analysis of symmetric punching of reinforced slabs without shear reinforcement – Open to further development.


Mikael Hallgren Model


where Fb = η Fb(max) and Mb = η Mb(max)

Modified Hallgren Model



Capacity predictions for reinforced concrete decks

Tests by Taylor et al (2001)

Application to Experimental Data

Test Panel Pt PBS PBD81

Ptaylor Pmh Pt / PBD81 Pt / Ptaylor

Pt / Pmh

[kN] [kN] [kN]

[kN] [kN]

D1 185 49.4 341.1 191.8 219.8 0.54 0.96 0.84

D2 200 49.3 317.6 181.3 206.8 0.63 1.10 0.97

D5 150 38 268 151.1 164.5 0.56 0.99 0.91

D6 182 38.1 276 173.3 184.12 0.66 1.05 0.99

D7 135 38.1 280.9 92.5 155.29 0.48 1.46 0.87

D8 157 38.7 274 148.9 167.45 0.57 1.05 0.94

Average 0.57 1.10 0.92

St. deviation 0.06 0.18 0.057



Tests by Kirkpatrick et al (1984)




Tests by Taylor et al (2007)


Test Panel

Deflection

[mm]

Pt

[kN]

PBD81 [kN]

Pmh [kN]

PBS

[kN]

PBD81/PBS

Pmh/PBS

Pt/Pmh

A1 2.5 333 570.1 401 128.3 4.44 6.75 0.83

A2 1.5 428 600.8 426.4 178.3 3.37 5.70 1.00

B1 2.15 344 563.6 381 66.5 8.48 11.07 0.90

B2 1.15 428 610.4 445.2 92.3 6.61 9.60 0.96

C1 2.6 333 588 406 66.6 8.83 11.58 0.82

C2 1.2 428 588 427.5 92.2 6.38 9.24 1.00

D1 1.85 368 553.5 365 127.9 4.33 5.51 1.01

D2 1.75 428 568.3 412 177.3 3.21 5.35 1.04

E1 1.95 392 632.8 484 202.1 3.13 3.89 0.81

E2 1.6 428 648.7 484.7 280 2.32 3.36 0.88

F1 1.9 371 566.5 415 199.5 2.84 3.56 0.89

F2 0.75 428 601.2 464.2 275.2 2.18 3.19 0.92

Average 0.92

St. deviation 0.08


Prestressed Concrete Decks

• Provisional of additional in-plane forces due to prestressing

• Improved punching shear capacity

• Improved serviceability


Engineering Method

ps pe

e s

y

f

f

Charts from OHBDC or NZ code may be used to estimate the ultimate capacity.

Analysis Methods

Modified Hallgren Model

where Fb = η Fb(max) and Mb = η Mb(max)

Punching Load

Boundary Lateral Restraint

Prestressing

Method of superposition


Test Panel

Ap

[mm2]

TPL

[MPa]

Pt

[kN]

Pmh [kN]

PNZ [kN]

Pt/Pmh

Pt/PNZ

SW-1A 0.0869 1.84 53.1 59.77 67.39 0.89 0.79

SE-1B 0.0869 1.84 53.04 59.77 67.39 0.89 0.79

CW-2B 0.105 2.15 54.82 64.16 70.45 0.85 0.78

CE-2B 0.105 2.15 57.26 64.16 70.45 0.89 0.81

NW-2A 0.1198 2.5 63.85 67.57 71.68 0.94 0.89

NW-2B 0.1198 2.5 48.7 67.57 71.68 0.72 0.68

CE-1B 0.14 2.91 74.43 72.08 74.74 1.03 1.00

CW-1A 0.14 2.91 65.82 72.08 74.74 0.91 0.88

SE-2B 0.1549 3.32 66.31 75.42 76.58 0.88 0.87

SW-2A 0.1549 3.32 72.97 75.42 76.58 0.97 0.95

NE-1B 0.176 3.88 80.54 80.15 79.65 1.00 1.01

NW-1A 0.176 3.88 77.52 80.15 79.65 0.97 0.97

CE-1A 0.19 4.37 94.12 83.42 80.87 1.13 1.16

NE-2A 0.19 4.37 92.28 83.42 80.87 1.11 1.14

NW-3B 0.19 4.37 80.11 83.42 80.87 0.96 0.99

CW-4B 0.19 4.37 82.66 83.42 80.87 0.99 1.02

SE-5B 0.19 4.37 87.3 83,42 80.87 1.05 1.08

SW-6A 0.19 4.37 92.23 83.42 80.87 1.11 1.14

Average

0.96 0.94

St. deviation

0.10 0.14

Tests in Queen’s University, Kingston, Canada


Savides (1989), He (1992)

Tests in Queen’s University, Kingston, Canada

• Prestressing postpones the commencement of lateral movements, delays cracking.

•Lesser the lateral movement possible, higher is the level of CMA leading to higher

punching loads.

40

50

60

70

80

90

100

0 1 2 3 4 5

Pu

nch

ing L

oad

(k

N)

TPL (MPa)

(TPL ~ Punching Load)

Pt

Pmh

PNZ

Linear (Pt)


FUTURE TESTS

Transverse Prestress Level

1.25 MPa 2.5 MPa

6400

• Variable TPL

• Joint skewness and roughness

• Variable position/locations of the load




•The UK Highway Agency BD81/02 gives good results for rigidly restraint deck slabs.

However, when the restraint is low, the results are unsafe. Also, this method does not

allow for the effect of varying reinforcement ratio.

•Taylor’s approach incorporates both flexural punching and shear punching failures.

•The New Zealand code gives better estimation when the TPL is high.

•Modified Hallgren model gives good results both for reinforced and transversely

prestressed deck slabs, therefore it will be used for future tests as well.

• Deck slabs exhibit high punching strength in the presence of CMA resulting from lateral

restraint and transverse prestressing.

•Future Study: Working on a 3D Nonlinear FEM Analysis.

Conclusions & Future Study


Thank you