摘要:
PEC(Partially Encased Composite)构件是指在工字钢或H型钢构件翼缘间填入混凝土、在混凝土中设置钢筋或翼缘连杆的组合构件。含有PEC构件的结构称为PEC结构,其承载力、延性以及刚度都要优于纯钢结构和钢筋混凝土结构,并且具有良好的抗火性能。我国研究者对PEC结构也制订了专门的技术规程T/CECS 719—2020《部分包覆钢-混凝土组合结构技术规范》。但是对采用单一H形主钢件的PEC柱在弱轴方向与梁刚性连接的节点性能,目前的试验研究尚不充分。对此,设计了3个PEC柱在弱轴方向与梁连接的节点子结构试件,分别编号JM、JH、BH,并进行静力单调加载与滞回加载,考察节点的受力性能和试件的破坏模式。节点采用端板螺栓连接。在构造设计过程中,结合工程实际,满足节点的受力特点以及预制化、装配式的要求,重点考虑了隔板布置、扁钢连杆的设置等因素。在试验设计过程中,参考了欧洲、加拿大和中国的规范,考虑了加载模式、破坏模式、加载路径、钢材强度等级、混凝土强度等级等因素,对试验装置、加载制度、测试方案等进行设计。接着进行试验研究,采用梁端反对称加载,分别进行了1个单调试验和2个滞回试验。其中,JM和JH试件的柱翼缘和节点区翼缘被削弱,JM试件采用静力单调加载,JH试件采用滞回加载,二者均出现柱破坏模式,且JH试件的极限承载力低于JM试件;BH试件的梁翼缘及腹板被削弱,采用滞回加载,最终出现梁破坏模式。试验结果表明:1)试验的PEC弱轴节点连接形式可以满足刚接的要求。2)通过利用T/CECS 719—2020中关于梁、柱、弱轴连接节点承载力的计算方法,可以准确判断试件的破坏模式,对实际工程具有指导意义。3)PEC弱轴连接节点中被包覆的混凝土部分,因侧面有来自梁构件中混凝土的约束,可有效提高弱轴节点的抗剪承载力。4)混凝土在往复作用下的损伤累积会使PEC试件的极限承载力出现下降。
Abstract:
A PEC(Partially Encased Composite) member is the composite component with concrete filling between the flanges of I-beam or H-shaped steel, and reinforcement or flange connecting bars in the concrete. The structure using PEC members is called PEC structure, whose load bearing capacity, ductility and stiffness are better than pure steel and reinforced concrete structures, and has good fire resistance. A special technical specification CECS 719-2020 has already been developed for PEC structures by our national researchers, but the experimental research on the mechanical performance of rigid connection between PEC columns and beams in the weak axis direction is still insufficient. So in this paper, three sub-structural joint specimens between PEC columns and beams in the weak axis direction were designed, which were numbered JM, JH, BH. The monotonic static loading and hysteresis loading tests were carried out to investigate the mechanical performance and the failure modes. The joints were connected by the endplate and bolt. To meet the requirements of prefabrication and assembly in engineering projects, the divided plate and flat steel were used in the specimen design. Based on the technical specifications in Europe, Canada and China, many factors such as loading mode, failure mode, loading path, steel strength and concrete strength were taken into account for the design of the test apparatus, loading regime and testing scheme. And then, by using antisymmetric loading at the beam ends, one monotonic static loading test and two hysteresis loading tests were carried out. Among the 3 specimens, the column flange and plane zone of JM and JH specimens were weakened, JM specimen was loaded by static monotonic loading and JH specimen was loaded by hysteresis loading; both of them showed column failure mode, and the ultimate loading capacity of JH specimen was lower than that of JM specimen; the beam flange and web of BH specimen were weakened and loaded by hysteresis loading, and finally the beam failure mode appeared. The results show that: 1)The tested joint between PEC beam and column in its weak axis direction can meet the requirements of rigid joints. 2) By using the calculation method of bearing capacity of beam, column and weak axis connection joints specified in CECS specification, the failure mode of specimens can be predicted correctly, which guiding significance for the projects. 3) Due to the lateral restraint from the concrete in the beam member, the concrete portion of the PEC weak-axis joint can effectively increase the shear loading capacity of the joint. 4) The accumulation of damage to the concrete under hysteresis loading will cause a reduction in the ultimate loading capacity of the PEC specimens.
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