Numerical Modeling of Shear Behavior of Reinforced Concrete Pile Caps

Abstract

The application of bending theory based methods and strut-and-tie models for the design of pile caps to resist shear is still a subject of debate, with the latest Eurocodes permitting both methods but not giving much guidance as to their use. The former UK design standards for concrete buildings and bridges, recently withdrawn, gave more guidance and it is likely that these methods will continue to be used by designers.However, there is considerable discrepancy between these standards, particularly with regards to the width of cap over which shear enhancement at short spans may be applied, and how much longitudinal reinforcement to take as a tie in the strut-and-tie method. Both standards are also seen as conservative.To gain a better understanding of the problem and assess the available design methods, nonlinear finite element analysis has been performed to investigate the shear behaviour of four-pile reinforced concrete pile caps, under full-width wall loading.The models were validated against an experimental programme that included an optical photogrammetric method for measuring full-field displacements. An extensive parametric study was carried out, varying shear span, cap width and reinforcement ratio over a practical range.The conservatism of the UK design standards, and the real shear capacity of the pile caps, were found to be a function of shear enhancement factor and the width of the 2 cap over which shear enhancement is applied. Strut-and-tie behaviour was observed in the models, and a commonly used strut-and-tie method was found to give fairly good predictions. A modified strut-and-tie method is suggested for this particular configuration of a four-pile cap under full-width loading, which gives more accurate predictions. This is especially so for samples with large transverse pile spacing where a significant proportion of the longitudinal reinforcement over the width of the cap can be assumed to participate in the yielding ties.

Efficient Two-Way Shear Grillage Model Solution for Bridge RC Four-Pile Caps under Wall Loading

“…The authors developed a semi-empirical ST model (Bloodworth et al 2012;Cao 2009), verified against tests at UoS for caps over certain ranges of the geometric ratios n and μ (Table 1), which are respectively the LD and TD pile spacings (lx, ly) divided by pile diameter (hp). An empirically derived 90% of the LD reinforcement Ast was taken as the yielding tie, independent of μ.…”

Punching shear failure in three-pile caps: Influence of the shear span-depth ratio and secondary reinforcement

“…Notwithstanding, distributed reinforcement should be located along the bottom side of pile caps to control soffit crack width, which is a recommendation in most standards despite the contribution made to the strength design being ignored. In this regard, Bloodworth [21] after analyzing the failure of four-pile caps under full width load, proposed a modification factor on the STM to take this secondary reinforcement into consideration. Table 1 summarizes the reinforcement distribution by distinguishing: the main bunched reinforcement (A sB ), horizontal secondary reinforcement (A sH ) and vertical secondary reinforcement (A sV ).…”

Effect of pile arrangement on the bending performance of an existing bridge footing under lateral seismic loading

“…The validation of the proposed model was investigated using 110 RC footing test results and other strut-and-tie models, and the results showed that the proposed model could give better accuracy and consistency. Other previous studies related to the strut-and-tie model can be found in the references (e.g., Adebar and Zhou 1996;Park et al 2008;Bloodworth et al 2012). In addtion, Jensen and Hoang (2012) proposed an upper bound plasticity approach for the strength prediction of reinforced concrete footings, and this approach can be considered a seismic loading Yong Yang et al Solids and Structures, 2020, 17(2), e257 3/16 complement to the lower bound strut-and-tie model.…”