实际工程中运用的全部连接都处在完全刚性和理想铰接两种情况之间,端板连接更是典型的半刚性连接。但由于缺乏计算理论和方法,我国目前都是将端板连接按刚性节点进行设计,与实际情况相差很大,对结构抗震也非常不利。关于端板连接的静力特性,国外已有较多研究,关于其滞回特性和抗震性能,国外研究并不多,而且国外通常采用的具体节点形式和构造与国内也有一定差别;国内在这方面的研究还处于起步阶段。本文的主要研究内容包括: (1) 进行了8 个梁柱端板连接的单向加载静力试验,创新性地测量了螺栓受力特性,研究了节点类型、端板厚度、螺栓直径、端板加劲肋、柱腹板加劲肋等因素对端板连接受力性能的影响。(2) 运用ANSYS 对静力试验试件进行了有限元计算,验证了有限元方法分析端板连接的可靠性,获取了很多试验中难以测量得到的结果。(3) 进行了8 个试件的循环荷载试验,研究了各种因素对节点滞回特性、延性和抗震性能的影响。(4) 针对半刚性端板连接的全过程受力特性,提出了理论分析模型,能够很好地计算端板连接的整体和细部受力特性,包括节点承载力、初始转动刚度、弯矩-转角(M-φ)曲线、节点域受力全过程等。(5) 在总结静力试验和循环荷载试验研究结果、有限元和理论分析成果的基础上,并结合国内外相关研究成果及规范,针对半刚性端板连接提出了系统的静力设计和抗震设计方法,主要包括:标准构造、静力承载力设计方法、弯矩—转角(M-φ)曲线的简化形式及计算方法、抗震承载力验算、延性设计、M-φ滞回曲线模型及计算方法。为我国钢结构设计规范关于半刚性端板连接的具体设计计算方法提供了有益补充。(6) 结合试件的安装,对端板连接中高强度螺栓的施拧顺序和预拉应变松弛进行了研究。
逆变焊机
Multistory steel frames are more and more widely used in our country and bolted end-plate connections are often adopted. Conventional analysis and design of steel frames are usually carried out under the assumption that connections joining the beams and columns are either fully rigid or ideally pinned. In fact, as evident from experimental observations, all connections used in current practice possess stiffness which fall between the extreme cases of fully rigid and ideally pinned. And the end-plate connection is a typically kind of semirigid connection. Because of the absence of calculation theory and design method for the semirigid end-plate connection, it is still calculated and designed as rigid connections in our country, which leads to the significant difference between the calculation result and the real stressed state of the end-plate connection. Also this is adverse for the seismic design of the structure. There has been much research about the static behavior of the semirigid end-plate connection overseas, but the research on its seismic behavior is very limited. The study on the semirigid end-plate connection is still at the starting stage in our country, and the end-plate connection type usually used is different from that in foreign countries. In this dissertation, experimental research of monotonic and cyclic loading tests, finite element calculation and theoretical analysis have been carried out to study the loading capacity, joint stiffness, joint deformation, rotation capacity, ductility and seismic behavior of the semirigid end-plate connection systematically. A complete set of design method for semirigid end-plate connections has been presented. Experimental research on construction of high strength bolts in end-plate connections has also been performed. The main scope of this dissertation includes: (1) 8 specimens of beam-to-column bolted end-plate connections with various types and details are tested under monotonic loads. The loading capacity, initial rotational stiffness, moment-rotation(M-φ) curve, shear deformation of the panel zone, the gap between the end-plate and the column flange, the bolt tension force distribution and the stressed state of bolts have been measured. And the influences of connection type, end-plate thickness, bolt size, end-plate rib stiffener and column panel zone stiffener have been studied. Especially it is innovative to measure the real stressed state of bolts in these tests. (2) The general-purpose finite element package, ANSYS, is adopted to analyze the specimens of the monotonic loading experiments. With comparison to the tests results, it has been verified that finite element method can efficiently simulate and analyze all types of end-plate connections with different details and the detailed behavior of each component, which has provided a good foundation for the further finite element analysis (FEA) on a large number of end-plate connections. Moreover, FEA can cover the shortage of the available measuring technique and provide some characteristics of end-plate connections which is not easy to be measured by tests. This is helpful for us to obtain accurate and comprehensive cognition on the mechanical behavior of end-plate connections. (3) Another 8 specimens of end-plate connections same with the monotonic loading tests are tested under cyclic loads and the influences of various details on the hysteretic characteristic, ductility and seismic behavior have been analyzed. The tests results have shown that the ductility and energy dissipation capacity of extended end-plate connections is very good and it can be used in seismic multistory steel frames. (4) A theoretical analysis model has been presented for analyzing the complete loading process of the panel zone in end-plate connections. Compared with a calculation method overseas and the tests results, it can be concluded that this method can calculate the mechanical behavior of the panel zone in end-plate connections accurately, including the shearing rotation, initial shearing rotational stiffness and the moment-shearing rotation (M-φs)curve, etc. And this method is applicable to the steel structure connections which join I-section beams and columns, including full welded connections, flange welded-web bolted connections and extended end-plate connections. (5) A theoretical method has been presented for analyzing the complete loading process of end-plate connections. In this method, the end-plate connection is decomposed into several components and the complete loading process of each component is analyzed. Finally the loading process of the whole connection can be obtained by superimposing each component. Compared with the relevant tests results, it has been verified that this method can not only calculate the integral mechanical behavior of end-plate connections accurately, including the loading capacity, initial rotational stiffness and the moment-rotation (M-φ) curve, etc, but also analyze and calculate the detailed behavior of each component including loading capacity and deformation. And this method is easy to be applied to interior end-plate connections. (6) In combination with the current domestic and overseas design codes and relative research production, a systematic design method for the static behavior of semirigid end-plate connections has been proposed on the base of achievements of aforementioned static experimental research, finite element calculation and theoretical analysis. This design method includes standard details, the loading capacity calculation method, the simplified moment-rotation (M-φ) curve and its corresponding calculation method. These are beneficial supplements to the steel structure design code of our country. (7) A complete set of seismic design method for semirigid end-plate connections has been proposed on the base of achievements of aforementioned cylic loading tests research, the current domestic and overseas codes and relative research achievements. It includes seismic resistance calculation, ductility design, M-φhesteretic model and its corresponding calculation method. Also the general seismic design principles for structural steelsemirigid end-plate connections has been suggested, which is “strong connector, weak plate”. These are all beneficial supplements to the steel structure seismic design code of our country. (8) During the construction of all the end-plate connection specimens, the investigation on the tightening sequence and the strain relaxation of high strength bolts in these connections have also been performed. A detailed tightening sequence has been recommended and proposals for the value of pretension force during constructioin, the final value of strain relaxation and the torque check have been presented, which afford some supplements to the relevant technical specification.