Q690高强钢冷成型方钢管柱轴心受压整体稳定性能试验研究

Experimental Study on Overall Buckling Behavior of Q690 High Strength Steel Cold-Formed Square Tube Columns Under Axial Compression

建筑业去碳化的策略之一是提高工程设计效率以降低对建材用量的需求。近年来,得益于高强钢生产技术的进步,使得这一构想成为可能。高强钢在结构工程中的有效使用可以减少构件尺寸和用钢量以及随后的制造、运输和施工成本,这些将有助于节约资源和减少碳排放。与普通钢Q355相比,虽然Q690高强钢的屈强比高、断后伸长率低,但是其具有优异的比强度。Q690高强钢的这些特性会对结构性能产生较大影响。因此,量化这些特性对结构性能的影响,对于确认其在建筑结构中的适用性非常重要。目前主要的钢结构设计规范中的轴压构件整体稳定承载力计算方法主要是参照普通碳钢Q235和Q355的研究数据而开发的,对于Q690高强钢是否适用,还须进一步验证。因此非常有必要检查这些设计方法对于采用各种制造工艺制造的Q690高强钢轴心受压构件的适用性。为研究Q690高强钢冷成型方钢管柱轴心受压的整体稳定性能,共设计8个试件,包括4种截面尺寸和8种长细比,6 mm和10 mm两种板厚,并通过轴心受压试验对其整体稳定性能进行了研究。试验前对试件的几何初弯曲和荷载初偏心以及截面的纵向残余应力分布均进行了测量。残余应力测量结果显示冷成型方形截面焊缝处的内外表面均存在较大的残余拉伸应变,在截面转角区的外表面和内表面分别存在显著的残余拉伸和压缩应变。轴心受压下所有试件失稳模式均为整体弯曲失稳。将试验结果同中国设计规范GB 50017—2017《钢结构设计标准》和欧洲规范Eurocode 3计算结果进行了对比。结果表明:根据中国规范和欧洲规范建议的设计曲线计算结果均偏于保守,且中国规范建议设计曲线相比欧洲规范更为保守。根据试验结果和设计规范中各柱设计曲线的对比结果,建议采用中国规范和欧洲规范中的a类柱子曲线设计此类Q690高强钢冷成型方钢管柱。

One of the strategies for decarbonizing the construction industry is to enhance the efficiency of engineering design in order to minimize the demand for building materials.Recent advancements in the production of high-strength steel have enabled this possibility.The effective utilization of high strength steel in engineering structures can decrease the dimensions of components and the usage amount of steel,consequently leading to reduced manufacturing,transportation,and construction expenses,which aids in resource conservation and contributes to the reduction of carbon emissions.Compared to the ordinary carbon steel Q355,the Q690 high strength steel exhibits excellent strength to self-weight ratios despite its high yield-to-tensile strength ratio and low elongations at fracture.The properties of high strength steel Q690 can greatly influence structural performance.Therefore,it is crucial to quantify the impact of these properties on structural performance in order to determine their suitability for use in building structures.The calculation method for the overall buckling bearing capacity of axial compression members in the current main structural steel design codes is primarily based on research data for ordinary carbon steels Q235 and Q355,and their applicability to Q690 high strength steel needs to be further verified.So it is very necessary to check the applicability of these design methods for axial compression members made of Q690 high strength steel using various fabrication processes.To investigate the overall buckling of cold-formed square columns made of Q690 high strength steel under axial compression,a total of eight specimens were designed.These specimens included four different cross-sectional sizes and eight slenderness ratios.The plate thicknesses used were 6 mm and 10 mm.The overall buckling of these specimens was examined through axial compression tests.Prior to the tests,measurements were taken to determine the geometrical initial bending,load initial eccentricity,and longitudinal residual stress distribution of the sections.Residual stress measurements revealed large residual tensile strain on both the inner and outer surfaces at the welded seams of the cold-formed square section.Additionally,significant residual tensile and compressive strains were found at the outer and the inner surfaces respectively of the round corners of section.It was found that all specimens exhibited overall buckling as the primary mode of failure under axial compression.The test results were compared with the calculation results of Chinese code GB 50017—2017 and European code Eurocode 3.The results indicate that the calculation results based on the design curves suggested by the Chinese code and Eurocode are conservative,and the Chinese code being more conservative compared to the European code.Based on the comparison of test results and design curves in the design code,it is recommended to use the column curve a in GB 50017—2017 and Eurocode 3 for the design of Q690 high strength steel cold-formed square tube columns.