Experimental and numerical investigation on collapse behavior of precast reinforced concrete beam-column sub-assemblages with cast-in-place ECC joints

In order to investigate the effects of engineering cementitious composite (ECC) used as post-cast materials and anchorage length of beam longitudinal rebars in the ECC cast-in-place joints on collapse behavior of precast reinforced concrete (PRC) structures, static pushdown collapse tests on scaled PRC beam-column (BC) sub-assemblages were carried out. Three BC sub-assemblage specimens having a double-span beam and a middle column joint were designed and fabricated with the same geometric dimensions, including one monolithic specimen BC0 and two PRC specimens BC1 and BC2. The specimen BC0 was cast in site with normal concrete, while the double-span beams of specimens BC1 and BC2 were first cast with normal concrete and then the middle column joint was post cast with ECC. The anchorage length of beam longitudinal rebars embedded into the middle joint was 29d, 20d, and 10d (d is the diameter of beam rebar) respectively for specimens BC0, BC1, and BC2, which could produce different splice length in the middle joint. On the basis of tests, refined finite element (FE) models were established and reasonably verified by a detailed comparison between numerical and experimental results. Based on the validated FE models, a parametric analysis was performed to study the effects of horizontal constraint stiffness, anchorage length, and bond strength between beam longitudinal rebars and ECC on collapse resistance of PRC sub-assemblages. The results showed that the application of ECC as the post cast material in the joint of PRC sub-assemblages could achieve similar collapse behavior to the monolithic counterpart and reduce the anchorage length of beam longitudinal rebars with a suggested lower limit of 20d. The bond strength between rebar and ECC in the joint had obvious influence on the collapse resistance and deformation capacity at large deformation stage.