| 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.
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