快速荷载交替作用下传统风格建筑双枋–柱节点试验研究

Experimental Research on Chinese Traditional Style Architecture Dual-lintel-Column Joint Under Alternating Rapid Loads

传统风格建筑枋–柱节点因其构造特点难以满足现行结构抗震设防的要求。选取传统风格建筑典型双枋–柱节点,研究其力学性能,并将其与钢–混凝土组合结构及黏滞阻尼器相结合,共设计3个传统风格建筑双枋–柱节点试件,包括两个附设黏滞阻尼器的试件及1个未附设阻尼器的对比试件。通过对3个试件交替施加快速往复正弦波荷载及谐波荷载,分析加载全过程中试件的破坏特性及破坏机制,通过荷载–位移滞回曲线、骨架曲线、承载能力及变形性能、耗能能力及刚度退化等指标对其力学性能进行研究。试验结果表明:采用钢–混凝土组合结构及合理设置黏滞阻尼器可显著提升传统风格建筑双枋–柱节点的力学性能。各试件破坏时形成的梁铰机制,呈现弯剪型破坏形态,试件滞回环的形状呈反“S”形,符合抗震设计要求;附设黏滞阻尼器后,节点试件的滞回曲线更为饱满,承载能力提升32.8%~66.4%,延性系数提高13.7%~17.0%,耗能能力提高29.1%~31.1%,刚度退化呈先快后慢的趋势,且后期趋于稳定,并可在一定程度上降低试件刚度的退化速率。各试件经正弦波荷载循环作用后产生一定的损伤累积,附设阻尼器试件在正弦波及谐波荷载交替作用下的剩余刚度高于对比试件。研究结果可为传统风格建筑的进一步探究及工程设计提供有益参考。

Objective Chinese traditional-style architecture is an area of exploration and innovation with promising prospects for popularization and application.Although Chinese traditional-style structures resemble ancient Chinese structures in external appearance,the materials,force transmission mechanisms,and seismic behaviors differ considerably.Modern building materials and construction technologies have been adopted in traditional Chinese structures;however,their structural properties,mechanical properties,and analytical methods differ from those of modern structures.Research shows that,compared to contemporary reinforced concrete column-beam joints,the structural mechanical properties of Chinese traditionalstyle architecture are inferior.Methods Consequently,three specimens are designed to study the mechanical behavior of Chinese traditional-style architecture dual-lintelcolumn joints with a steel-concrete composite structure and viscous dampers.Two specimens with a viscous damper are classified as controlled structures,and one specimen without a viscous damper is classified as a non-controlled structure.Alternating reciprocating sine wave loading and reciprocating harmonic load tests are performed on all specimens under dynamic experimental conditions.The failure characteristics and mechanisms of the specimens are studied,and mechanical performances such as the load-displacement hysteretic curve,skeleton curve,bearing capacity,deformation performance,energy dissipation capacity,and stiffness degradation of the dual-lintel-column joints were analyzed.Results and Discussions The results show that the mechanical properties of Chinese traditional-style architecture dual-lintel-column joints can be considerably improved using a steel-concrete composite structure and properly setting viscous dampers.Based on the comparative analysis,the entire loading process for all specimens can be divided into three stages:the non-cracking stage,seam-working stage,and failure stage.For the ABS–1 specimen,in the first stage,the hysteresis curve was essentially linear with no considerable residual deformation when unloaded to zero.In the second stage,the cracks developed considerably at the connecting parts of the lintel-column,forming through cracks.The nonlinear characteristics of the hysteretic curve became obvious,with residual deformation and stiffness and strength attenuation when unloaded to zero.In the final stage,the concrete at the connecting part of the lintel column was crushed and spalled,exposing the rebar.The test was terminated because the specimen had reached a geometrically unstable state.For the ABS–2 and ABS–3 specimens,the failure modes were essentially the same.In the first stage,the loading and unloading curves of the hysteresis loop almost coincided,and the elastic characteristics of the components were notable,with no substantial residual deformation when unloaded to zero.In the second stage,some cracks appeared in the connecting parts of the lintel column,but no through cracks were observed.Residual deformation and stiffness and strength attenuation occurred when unloaded to zero.During the loading process, the specimen and the damper worked together. In the final stage, some through cracks appeared in the connecting parts of the lintel column, exposing the steel bars. The specimens remained geometrically stable when the test was terminated, as the viscous damper provided support. The results show that the failure modes were of the shear-flexural type, and the failure mechanism for all specimens was the beam hinge mechanism, which meets seismic fortification requirements. The results of the hysteresis curve analysis show that, with the in-crease in the controlled displacement, the area enclosed by the hysteresis loop gradually increases, and the horizontal resistance becomes nonlin-ear with the corresponding horizontal displacement. The strength and stiffness degradation of all specimens were notable, with small-scale con-crete crushing. The load decreased for all specimens, but the degradation in the load for the controlled structure was milder compared to that of the non-controlled structure, while the degradation in the load for the joint with a damper was slower than that of the joint without a damper. This phenomenon was caused, to some extent, by the installation of a viscous damper, which improved the load-carrying capacity and delayed damage development. During the loading process, the skeleton curves can be divided into three stages: elastic, elastoplastic, and plastic stages. There was no considerable yield point in the backbone curves, reflecting the gradual development of yield from the microcosm to the macrocosm. Based on the test results, the longitudinal steel rebar yield was considered the initiation of yield. Compared to the ABS-1 specimen, the joint with a damper had a more gradual load drop in the descending section after the skeleton curve reached its peak. The bearing capacity of the joint with a damper was considerably superior to that of the joint without a damper. The bearing capacity and ductility performance were significantly increased by the attached viscous damper. Consequently, the combination of a viscous damper and Chinese traditional-style architecture can be considered a super-ior method for improving seismic performance and protecting the main structure. Compared to the joint without a damper, the bearing capacity and deformation properties of the joint with a damper increased significantly. The peak load improved by 55.1% for ABS-2 and 32.8% for ABS-3 under sine wave load, and by 66.4% for ABS-2 and 34.4% for ABS-3 under harmonic load. The displacement ductility coefficient im-proved by 13.7% for ABS-2 and 15.8% for ABS-3 under sine wave load, and by 14.4% for ABS-2 and 17.0% for ABS-3 under harmonic load. The ductility coefficient of all specimens followed the order ABS-3, ABS-2, and ABS-1, from smallest to largest. Compared to the joint bearing capacity, ABS-2 had the largest. Therefore, in actual engineering, it is essential to focus not only on the improvement of single performance para-meters but also on the overall performance of the structure when selecting damper parameters. Compared to the joint without a damper under har-monic load, the equivalent damping coefficient and energy ratio for the joint with a damper increased significantly by approximately 23.0%~27.0% under the yield point, 29.1%~31.1% under the ultimate point, and 43.1%~43.8% under the failure point. Similarly, the increased range of the energy ratio was approximately 5.9%~22.1% at the failure point. Conclusions The results indicated that the viscous damper considerably improved the energy dissipation capacity, making it possible to achieve the performance objective of no damage under medium seismic events and reparability under severe earthquakes. The stiffness degradation showed an initial rapid decline, followed by a slower decline, and tended to stabilize in the later stages, which can inhibit the stiffness degradation rate of the specimens to some extent. After cyclic action under sine wave loading, the residual stiffness of the joint with a damper was higher than that of the joint without a damper. These results and proposals have reference value for the design, construction, and research of antique buildings.