高强轻骨料混凝土框架中节点抗震性能试验研究

完成了4个1/3缩尺比例的不同核心区配箍率的高强轻骨料混凝土框架中节点在不同轴压比下的低周反复荷载试验，系统研究了节点的破坏过程与破坏形态、滞回曲线与骨架曲线、刚度与强度退化、延性耗能、箍筋应变等，深入分析了该类构件破坏时的自身特性、承载力及与普通混凝土节点的区别。研究表明：与普通混凝土节点类似，试件破坏过程均经历了初裂、通裂、极限和破坏四个阶段，滞回曲线形态、节点区变形规律与普通混凝土无异；节点耗能和延性与普通混凝土接近；节点区混凝土的破坏在骨料和骨料与水泥浆界面处均有发生，破坏时混凝土剥落范围较大，部分保护层骨料被切掉，出现整体脱落；适当提高轴压比和配箍率能够改善节点区的抗剪强度，提高节点的延性和耗能，且因骨料强度的提高，节点区纵向钢筋与高强轻骨料混凝土的黏结性能较以往研究结果有所改善；节点区箍筋仅部分屈服，建议采用复合配箍或采用约束混凝土，增强约束效果。同时，通过计算表明：在未对轻骨料混凝土强度进行折减的情况下，各模型计算值与试验结果吻合较好，建议适当提高各个模型对轻骨料混凝土强度的折减系数。

Experimental study on seismic behavior of frame interior joints with high-strength lightweight aggregate reinforced concrete

Four 1/3-scale high-strength lightweight aggregate concrete (HSLAC) interior beam-column joints with respect to two levels of axial compressive forces and joint stirrup ratios were prepared and tested under the reversed quasi-static cyclic loading. The shear performance, including the failure modes and failure processes, hysteretic curves and skeleton curves, stiffness and strength degradations, displacement ductility, energy dissipation, and the stirrup strains, were systematically studied. The failure characteristics and the shear strengths of these specimens and the discrepancies with normal weight concrete (NWC) specimens were mainly analyzed. Test results indicate that, similar to NWC specimens, all HSLAC specimens may experience four phases, namely, initial cracking, running-through cracking, ultimate phase and failure phase during the entire failure process. In terms of the hysteretic curves and the displacement laws of joint, the specimens are almost the same as the NWC specimens. In terms of the energy dissipation and the ductility, the specimens are close to the NWC specimens. The failures of HSLAC specimens may occur at the aggregate boundary and across the aggregate, and during the failure concrete, peeling off in a large area, cutting off of some aggregates in the concrete cover and the entire spalling of concrete can be seen. Properly increasing the axial compression ratio and the transverse reinforcement ratio can effectively enhance the shear strength and improve the ductility and energy dissipation properties of joints. Due to the increased strength of lightweight aggregates, the bond property between HSLAC and longitudinal bars within joint core can also be improved to some extent. Only a few of stirrup may yield. Hence, it is recommended that the composite stirrup or confined concrete shall be used to enhance the confinement. Additionally, calculation results indicate that, under the condition without reducing the HSLAC strength, the predicted results from the shear models are in good agreement with the test results, and appropriate increase of the HSLAC strength reduction factors for various shear models is suggested.