Development of strut-and-tie models using topology optimization based on modified optimal criterion

Strut-and-tie models (STMs) have been widely used to design disturbed regions in structural concrete members. Recently, topology optimization methods, based on the principle of minimum strain energy directly and indirectly, have been adopted to generate STMs in reinforced concrete structures. Unfortunately, current topology optimization methods do not work in many typical disturbed regions. The optimization history of the rectangular anchorage zones shows that the principle of minimum strain energy is a necessary condition for STM, not a sufficient condition. Because, it fails to capture the load transfer path properly in structural concrete tensile regions. To address this issue, a modified optimality criterion is proposed to illustrate the load path in tensile regions. And the desired STM is the one with the maximum overall stiffness and minimum strain energy of the tie. The STM of the rectangular anchorage zones and dapped beams have been developed successfully, and verified by the current ACI 318-08 code recommendations and experimental evidence.

Automated summary

Strut-and-tie models are commonly used for designing disturbed regions in structural concrete members, and topology optimization methods are adopted for generating these models. However, current methods do not work in many typical disturbed regions, leading to the proposal of a modified optimality criterion.