高轴压比拉筋圆钢管混凝土柱界面滑移行为与抗震性能研究

Research on Interface Sliding Behavior and Seismic Performance of Stirrup-Confined Concrete Filled Circular Steel Tubular Columns Under High Axial Compression Ratio

高轴压比下普通钢管混凝土柱的抗震性能略差,与其他钢管内约束混凝土构造措施相比,横向拉筋构造可高效提升高轴压比下钢管混凝土柱的约束效率和抗震性能。在高轴压比圆形、方形拉筋钢管混凝土抗震性能试验成果的基础上,采用ABAQUS软件建立三维实体有限元精细化计算模型并进行试验验证,随后开展单调加载和滞回加载下拉筋钢管混凝土柱受力性能的参数分析,探讨拉筋对钢管与混凝土界面滑移、应力水平和抗震性能的影响规律。分析结果表明:1)压弯荷载下钢管和混凝土之间存在界面滑移行为,使得加载过程中钢管和混凝土中性轴高度变化不一致,当滞回加载时混凝土受拉面积大幅度减小,混凝土和钢管中性轴的差异愈发增大,相对滑移更大,最终混凝土全截面受压而钢管抗弯;2)当钢管用钢量保持不变而端部布置拉筋算例后,钢管和混凝土中性轴的差异减小,钢管和混凝土之间界面滑移减小使得抗弯刚度提升10%,拉筋由于直接约束混凝土,使得钢管纵向拉应力和混凝土纵向压应力水平都得以提升且应力水平更均匀,以及钢管受拉区面积增大而混凝土受压区面积减小,导致钢管截面受压区高度降低从而极限承载力提升20%~50%;3)滞回加载下拉筋有效提升钢管混凝土柱的抗震性能,当钢管混凝土柱整体用钢量保持不变时,高轴压比钢管混凝土柱的刚度可维持不变,承载力提升10%~20%,耗能能力提升2倍,钢管和拉筋约束混凝土而耗能提升约1倍,使得钢管受压区高度降低导致构件转动能力大幅度提升,钢管塑性耗能能力得以充分发挥,因此钢管耗能提升约3倍。

Normal concrete filled steel tube columns(CFST)exhibit poor potency under high axial compression ratio in seismic action.In contrast to other inner constraint measures of CFST,the transverse stirrups effectively prompt the constraint confinement efficiency and seismic performance of CFST columns under high axial compression ratio.Based on the test and the research of circular and square CFST columns’seismic performance under high axial compression ratio,the three-dimension solid finite element model was established and the test results were verified,The mechanical properties parameter analysis of stirrup-confined circular CFST columns under monotonic loading and hysteretic loading was carried out.The influence of stirrups on the interface sliding behaviour,stress level and seismic performance was probed.The research results elucidate:1)The interface sliding behaviour exists between steel tube and concrete under compression-bending loading,which leads to the inconsistent changes in the neutral axis height of steel tube and concrete during the loading progress.Under the hysteretic loading,the tensile area of concrete lessens conspicuously and the difference between the neutral axis of concrete and steel tube augments,resulting in greater interface sliding.Finally,the full section of concrete is compressed while the steel tube resists bending.2)When the steel tube consumption remains unchanged,the difference between the neutral axis of concrete and steel tube reduces after the stirrups were set to the end of the columns.The diminishing of the interface sliding gives rise 10%of the bending stiffness.The stirrups directly constrain the concrete and resist the buckling of the steel tube,which increased the tensile stress level of the steel tube and the compression stress level of the concrete and the stress level is more uniform.The tensile area of steel tube increases while the compressive area of concrete decreases,which leads to the 20%-50%increase of the ultimate capacity.3)Stirrups effectively improve the seismic performance of the CFST columns under hysteretic loading.When the steel consumption of CFST column remains unchanged,the stiffness of high axial compression ratio CFST columns remains unchanged.The bearing capacity increases by 10%-20%,and the energy dissipation of the CFST columns is increases by 2 times.The energy dissipation of the concrete increases by 1 time due to the confinement effect of the steel tube and the stirrups.The compression region height of the CFST column is reduced,which leads to the greater rotational capacity of the member.The plastic energy dissipation of the steel tube can be effectively elicited by a factor of 3.