120 MPa高强混凝土型钢组合构件受力性能试验研究

Experimental study on mechanical behavior of 120 MPa concrete encased steel composite members

进行了120 MPa高强混凝土型钢组合短柱、组合梁的受压及受弯性能试验,考察箍筋间距和钢纤维掺量对高强混凝土型钢组合短柱的破坏形态、承载力和延性的影响,得到荷载-位移曲线及轴力-应变曲线。研究表明:随着双肢箍筋间距加密,组合短柱虽然仍表现为脆性破坏,但箍筋加密增强了混凝土对型钢的约束效应;随着钢纤维掺量从0.3%增加到0.5%,试件表现为延性破坏。组合短柱在小偏压时发生截面承载力破坏,在大偏压时发生弯曲破坏;组合梁由于箍筋加密为50 mm,增强了混凝土对型钢的约束,并且0.5%钢纤维掺入提高了混凝土的抗拉强度,形成塑性铰时,型钢达到全截面屈服,端部未出现型钢推出现象。通过试验值与EC4计算值比较可得,现行EC4规范可准确估算120 MPa混凝土型钢组合短柱及组合梁在大偏心受压和纯弯状态下的承载力,但对轴心受压和小偏心受压短柱的承载力估算偏小,其N-M曲线不能直接扩展用于120 MPa混凝土型钢柱承载力验算。

The compression and bending tests of 120 MPa high strength concrete composite steel members were carried out. The influence of hoop spacing and steel fiber content on failure mode, cross-section resistance and ductility index of such members were investigated, and the load-displacement curve and the axial force-strain curve were obtained. The results indicate that with the hoop spacing decreased to 50 mm, despite brittle failure mode of the specimens, the decrease of hooping space cannot sufficiently enhance the confinement action on concrete and core steel and the bearing capacity of the specimens under axial compression tends to increase. With the content of steel fiber increased from 0.3% to 0.5%, the bearing capacity of the specimens under axial compression tends to increase and the specimens display ductile failure mode. When the ultimate load is reached, the specimen with small eccentricity are subjected to compressive failure, and the specimen with large eccentricity are subjected to tensile failure. The section steel does not slide out at the end and achieves full yield when plastic hinge is formed in pure bending specimen because the hoop spacing 50 mm enhances confinement action on concrete and core steel and 0.5% steel fiber content improves the tensile strength of concrete. Comparing to test results, the design method proposed by EC4 can precisely predict the load capacity for 120 MPa concrete encased steel composite members under eccentric load or bending moment, but somewhat underestimates those under axial load, and its N-M curve cannot be directly extended to check the bearing capacity of the 120 MPa concrete-encased stub columns.