Seismic performance assessment of post-tensioned ultra-high performance concrete prefabricated retaining blocks based on OpenSees

Abstract

The post-tensioned ultra-high performance concrete (UHPC) prefabricated retaining block (PRB) has been proven to be novelty in maintaining the restriction functionality as that of conventional normal concrete (NC) shear key (SK). However, developing a practical and effective mechanical model for the post-tensioned UHPC PRB remains challenging, especially in predicting its rotational response and failure modes under different level earthquake loads. These challenges limit its widespread application in bridge structures. Therefore, based on the OpenSees platform, this study developed a simplified mechanical model of the UHPC PRB and assessed its seismic performance while applying it to an example bridge. First, based on the design philosophy of the proposed UHPC PRB, as well as the observed phenomena and data in the model test, the detailed derivation process for the simplified theoretical model was presented. Then, the OpenSees models of the proposed UHPC PRB was developed to investigate its sensitivity to several significant design parameters. Meanwhile, the corresponding two-step seismic design methodology was suggested and verified based on the developed OpenSees model of the example bridge. The results show that, (i) the proposed theoretical model can effectively predicted the mechanical response of the UHPC PRB; (ii) initial tension forces (ITF) and number (N_PT) of prestressing tendons (PT), loading height (H_F), were critical factors affecting its mechanical properties, particularly the critical rotational load (CRL); (iii) prestress loss had a certain impact on the development of the simplified bilinear model for UHPC PRB, though this effect can be neglected in real highway bridge applications. This study established a comprehensive framework that includes the derivation of simplified mechanical models, OpenSees modeling to verify seismic performance and a two-step seismic design methodology. It advances the development of the proposed UHPC PRB structures and provides valuable insights for their innovation and application in bridge engineering.