Softened Strut-and-Tie Model for Shear and Flexural Strengths of Reinforced Concrete Pile Caps

abstract: Reinforced concrete pile caps may be designed trough plastic models (strut and tie model) or models based on bending theory. The formulae available for verifying the stress is based on caps supported on concrete piles, with few studies about the stress distribution on caps supported on steel piles. To analyze the structural behavior of caps supported on steel piles, as well as the stress on the superior and inferior nodal zones, four two-pile caps supported on steel piles were tested. The variables were the embedment length and in one of the specimens a steel plate was welded on top of both piles. It was observed that the embedment length has substantial influence on pile cap structural behavior. It was concluded that, to verify the stress on inferior nodal zone of the cap, aside from pile area, an area of concrete confined between the flaps of the pile must be considered.

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An evaluation of pile cap design methods in accordance with the Canadian design standard

Canadian Journal of Civil Engineering ◽

10.1139/l03-075 ◽

2004 ◽

Vol 31 (1) ◽

pp. 109-119 ◽

Cited By ~ 7

Author(s):

William Cavers ◽

Gordon A Fenton

Keyword(s):

Reinforced Concrete ◽

Structural Design ◽

Design Methods ◽

Building Codes ◽

Design Models ◽

Design Standard ◽

Strut And Tie ◽

Pile Cap ◽

Pile Caps ◽

Strut And Tie Model

There are a number of design methods that have been described for the design of pile caps, but there has been no consensus on which method provides the best approach for the working designer. This paper describes a study conducted to establish the performance of several pile cap design methods, particularly with respect to the Canadian standard, CSA A23.3-94. Previous research was examined to determine the basis of the design methods and the state of current research. The design methods identified were then applied to pile caps for which test data were available. The theoretical loads obtained using the various design methods were compared with the experimental loads. The results of this study indicate that two design models of the five examined are the most suitable. This study also indicates that the provisions of the Canadian design standard are adequate. A possible refinement of the strut-and-tie model incorporating a geometric limit is also outlined.Key words: building codes, footings, pile caps, reinforced concrete, structural design.

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Strength predictions of pile caps by a strut-and-tie model approach

Canadian Journal of Civil Engineering ◽

10.1139/l08-062 ◽

2008 ◽

Vol 35 (12) ◽

pp. 1399-1413 ◽

Cited By ~ 14

Author(s):

JungWoong Park ◽

Daniel Kuchma ◽

Rafael Souza

Keyword(s):

Reinforced Concrete ◽

American Concrete Institute ◽

Valuable Insight ◽

Strain Compatibility ◽

Strut And Tie ◽

Pile Cap ◽

Pile Caps ◽

Strut And Tie Model ◽

And Behavior ◽

Model Approach

In this paper, a strut-and-tie model approach is presented for calculating the strength of reinforced concrete pile caps. The proposed method employs constitutive laws for cracked reinforced concrete and considers strain compatibility. This method is used to calculate the load-carrying capacity of 116 pile caps that have been tested to failure in structural research laboratories. This method is illustrated to provide more accurate estimates of behavior and capacity than the special provisions for slabs and footings of the 1999 American Concrete Institute (ACI) code, the pile cap provisions in the 2002 CRSI design handbook, and the strut-and-tie model provisions in either the 2005 ACI code or the 2004 Canadian Standards Association (CSA) A23.3 standard. The comparison shows that the proposed method consistently well predicts the strengths of pile caps with shear span-to-depth ratios ranging from 0.49 to 1.8 and concrete strengths less than 41 MPa. The proposed approach provides valuable insight into the design and behavior of pile caps.

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Failure Probabilities of Reinforced Concrete Square Pile Caps

Journal of Mechanics ◽

10.1017/s1727719100001192 ◽

2007 ◽

Vol 23 (2) ◽

pp. 173-180

Author(s):

W.-Y. Lu

Keyword(s):

Shear Strength ◽

Reinforced Concrete ◽

Design Method ◽

Main Body ◽

Concrete Pile ◽

Diagonal Compression ◽

Pile Cap ◽

Pile Caps ◽

Strut And Tie Model ◽

Failure Probabilities

AbstractAn analytical model for determining the shear strength of concrete pile caps under the failure mode of diagonal-compression originally based on the softened strut-and-tie model is proposed. The failure probabilities of reinforced concrete pile caps are investigated by Monte Carlo method. The results indicate that the proposed model can accurately predict the shear strength of the pile caps. The distribution of the failure probabilities for pile caps designed to ACI 318-02 Appendix A and the proposed design method are more uniform than that designed to the ACI 318-99. The ACI 318-99 is very conservative and cannot provide a consistent safety for pile caps design. It is suggested that the procedures in the ACI 318-02 Appendix A should be moved to the main body of ACI 318-02 and the proposed design method should be incorporated into the current reinforced concrete pile cap design methods.

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