ECC后浇节点装配式混凝土梁-柱子结构倒塌试验

Collapse tests of precast concrete beam-column sub-assemblages with ECC post-cast joints

对纤维增强水泥基复合材料(ECC)后浇节点装配式混凝土梁-柱子结构开展了静力Pushdown倒塌试验。设计了3个梁-柱子结构试件,几何尺寸与配筋形式相同,但试件BC0采用普通混凝土整体现浇,试件BC1和BC2的双跨梁采用普通混凝土先浇、中柱节点采用ECC后浇。试件BC0梁下部纵筋在中柱节点的直线锚固长度l_(a)为29 d(d为纵筋直径),而ECC后浇试件BC1和BC2的l_(a)分别为20 d、10 d。研究表明:与普通混凝土整体现浇试件BC0相比,ECC后浇试件BC1的梁-压拱机制的承载力基本相当,而悬链线机制的承载力提高了约13%,变形能力提高了约21%;后浇试件BC2梁下部纵筋会因锚固长度l_(a)不足出现过早的粘结破坏,导致梁-压拱机制的承载力与变形能力下降。此外,利用塑性理论模型、周育泷等模型、YI等模型分别计算了各试件的梁机制、压拱机制及悬链线机制的承载力理论值,与试验值的吻合度较好。

Collapse tests were conducted on precast reinforced concrete frame(RC)beam-column sub-assemblages with engineered cementitious composite(ECC)post-cast joints.Three model specimens made of double-span beams and a middle column joint were constructed with identical geometries and reinforcements,one of which was a normal concrete cast-in-situ monolithic specimen BC0,while the double-span beams of the other two specimens BC1 and BC2 were first casted with normal concrete,and then the middle column joint was post poured with ECC.The anchorage length of longitudinal rebars at the beam bottom into the middle joint for three specimens was 29 d,20 d,and 10 d(d is the rebar diameter),respectively.Test results showed that compared with the monolithic specimen BC0,the ECC post-cast specimen BC1 with a 20 d anchorage length had an almost identical resistance of beam and compression arch mechanism,and an increase of the resistance of catenary mechanism by 13%and the corresponding deformation ability by 21%.While another ECC post-cast specimen BC2 with a shorter anchorage length of 10 d presented a lower resistance of beam and compression arch mechanism and deformation ability,due to the premature bonding failure of bottom longitudinal rebars of beams.Based on the theoretical model of plasticity,the model proposed by ZHOU et al.,and the model proposed by YI et al.,theoretical values of the resistance of beam mechanism,compression arch mechanism,and catenary mechanism for three specimens were respectively calculated,which agreed well with the experimental values.