А practical method for strut-and-tie modelling of the bridge pile cap

Abstract

Pile cap is a typical example of a discontinuity region, where the classical beam theory does not apply. Therefore, strut-and-tie (STM) model is considered appropriate for the analysis of pile caps. Although, the strut-and-tie method is a powerful tool, one of its shortcomings is the need for guidelines for the standardized models. Otherwise, it is left to the designer to come up subjectively with the STM model, which is a sensitive task. In literature, usually simple loading (axial compression or compression with bending only in one direction) on a four-pile cap is discussed. In practice, for real bridge structure, usual loading is alternate biaxial bending, along with compression, on much larger number of piles, making the typical four-pile caps models useless. A practical methodology for creating pile cap model with large number of piles and with complex loading is presented step-by-step. It is further illustrated for the cases with six piles and eight piles from the actual bridge structures, where the method was applied in practice.