Experimental study on seismic performance of precast UHPC circular hollow piers confined by different stirrup ratios

Abstract

The idea of precast ultra-high performance concrete (UHPC) circular hollow piers is conceived to minimize self-weight and expedite construction. However, compared with solid concrete piers, this new type of pier, characterized by high strength material and thin-walled section, will have different seismic performance. In the seismic design of the pier, the transverse confinement provided by the stirrups at the bottom of the UHPC hollow pier plays an important role. To investigate the effect of transverse confinement on the seismic performance of precast circular hollow piers, three precast UHPC circular hollow piers with different stirrup spacings and one normal concrete (NC) pier with the same dimensions were designed and fabricated for quasi-static tests. The experimental observation revealed that the failure mode of UHPC piers were dominated by flexural transverse cracks. As the number of stirrups decreased, vertical splitting cracks appeared at the bottom of the UHPC pier, but the pier shaft remained intact. The peak load, ductility, cumulative energy dissipation, and initial stiffness of benchmark UHPC specimen were 13.4%, 49.9%, 58.8%, and 111.1% higher than that of NC specimen. The reduction of stirrup numbers in UHPC pier will decline the ductility and ultimate displacement of the specimens, while the influence on other seismic responses was limited. Meanwhile, the methods of calculating peak stress and strain for confined UHPC and NC circular hollow columns were proposed. Finally, a finite element model was developed in OpenSees. The bond-slip and buckling effects of the longitudinal rebar, and the interfacial behavior of joint were considered. The numerical results showed that the hysteretic and skeleton curves can be well reproduced, and the error between numerical and experimental peak loads of the specimen was less than 5¿%. Based on the experimental and numerical results, the number of stirrups in the plastic hinge area was reduced by half, yet the seismic performance remains comparable to that of the NC hollow pier of the same size.

This research is supported by the National Key Research and Development Program of China (No. 2019YFE0119800). Shanghai Engineering Research Center of High-Performance Composite Bridges (19DZ2254200). The China Scholarship Council (CSC), during a research stay of the first author in the Universitat Politècnica de Catalunya. The second author acknowledges the support of research projects TED2021-130272B-C21 funded by MCIN/550 AEI/10.13039/501100011033 “European Union Next Generation EU/PRTR” and PID2021-123701OB-C21, funded by MCIN/ AEI/10.13039/501100011033 and European Regional Development Funds (ERDF) “A way to make Europe”.

Peer Reviewed

11 - Ciutats i Comunitats Sostenibles

13 - Acció per al Clima

13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els països

9 - Indústria, Innovació i Infraestructura

10 - Reducció de les Desigualtats

Postprint (author's final draft)