Development of strut-and-tie models for RC bridge pier caps subjected to asymmetric loading

Reinforced concrete (RC) bridge pier caps are subjected to concentrated loads from the superstructure. These are deep members where strain distribution is non-linear and traditional flexural theory cannot be used. Strut-and-tie method can be used to design and detail such regions which idealises the pier cap domain into struts and ties capable of transmitting the loads to the pier. The loads on pier caps can be asymmetric due the effect of live loads, unequal spans and possible curvature of the superstructure. This paper attempts to develop strut-and-tie models for symmetric pier caps subject to asymmetric loading. The possible strut and tie models (STM) for load cases with one side subjected to a heavier load with respect to the other are presented. The ratio between heavier and lighter load is considered as a parameter in this study. The optimised strut and tie model is chosen from the possible models for a particular load case based on minimum tension load path (sum of product of force and corresponding length of the tension members). A solution algorithm is presented for the development of strut and tie models.