装配整体式混凝土框架结构抗连续倒塌试验研究

节点连接的破坏和失效显著影响装配整体式混凝土框架结构在连续倒塌大变形下的抗力机理、破坏模式和变形能力。为研究装配整体式混凝土框架结构的抗连续倒塌性能，设计了3个1/3缩尺的两跨梁柱子结构试件，开展了拟均布加载下的静力连续倒塌试验和理论计算分析。包含1个现浇对比试件RC和2个采用不同梁柱纵筋连接方式的装配整体式试件PC，即梁钢筋通过机械套筒连接和锚固板锚固、柱钢筋通过半灌浆套筒连接的试件，梁钢筋通过90°弯折锚固、柱钢筋通过约束浆锚连接的试件。试验发现：由于后浇区混凝土强度的提高，装配整体式试件的压拱机制峰值荷载较现浇对比试件分别提高22.9%和20.2%；拟均布加载下，梁最终变形呈曲线，该变形模式下节点需要提供更高的转动能力才能保证梁整体变形满足T/CECS 392—2021《建筑结构抗倒塌设计标准》的挠度要求；在悬链线峰值荷载时相邻跨梁提供的水平约束能有效限制边柱的水平变形和装配式试件的坐浆层滑移。理论计算表明，装配整体式试件的压拱作用的倒塌抗力贡献率低于现浇对比试件，其原因是边柱坐浆层滑移削弱了梁端约束，进而降低了压拱机制承载力。采用能量原理评估了试件的动力倒塌抗力，由于压拱机制下的累积耗能能力较高，装配整体式试件的动力倒塌抗力分别比现浇试件提高了16.8%和18.8%。

Experimental study on precast concrete frames with monolithic joints to resist progressive collapse

Collapse resistance, failure modes and deformation capacity of precast concrete (PC) frames with monolithic joints under large deformation of progressive collapse are significantly influenced by the damage and failure of connections of joints. To investigate the progressive collapse resistant performance of PC frame structures, three 1/3 scaled beam-column specimens with two spans were designed, and tested statically with an equivalent uniformly distributed load (UDL). The specimens were composed of one reinforced concrete (RC) and two PC beam-column substructures with different reinforcement connections. In one PC specimen, mechanical sleeves and anchorage plates were used for reinforcement connections in beams while rebar splices by grout-filled coupling sleeves were used for column rebars. In the other PC specimen, beam rebars were anchored by 90° hooks and column rebars were connected by rebar lapping in grout-filled holes. Test results show that, the collapse resistances of the two PC specimens under compressive arch action (CAA) are 22.9% and 20.2% higher than that of the RC specimen, owing to the increase of the strength of post-cast concrete. The final deformation of the beams is curvilinear under UDL. Hence, under such a deformation mode, the higher rotation capacity at beam ends is required for improving the overall deformation of beams to satisfy the structural deflection demand specified by T/CECS 392—2021‘Code for anti-collapse design of building structures’. At the peak load under catenary action (CA), the horizontal restrains provided by the adjacent beams could effectively limit the horizontal deformation of columns and the shear-slip along with grouting layers. Analytical models were developed to calculate the collapse resistances at peak of CAA and CA. Because the slips at the grouting layers in PC specimens decrease the constraint to the beams, the collapse resistances contributed by the CAA of PC specimens are lower than that of the RC specimen. According to the energy conservation principle, the two PC specimens exhibit 16.8% and 18.8% higher dynamic collapse resistances than the RC specimen due to the larger energy dissipation under CAA, respectively.