Study On Moment-rotation Relationship Of End-plate Connections And Seismic Behavior Of Semi-rigid Steel Frames

Widespread failures in welded steel beam-to-column connections were observed in boththe1994Northridge Earthquake and the1995Hyogoken-Nanbu Earthquake.. From then on,end-plate connections which possess better seismic performance have been broadly studied.While, so far the majority of researches were focused on the strong-axis connections and fewwere focused on the weak-axis connections and semi-rigid steel frames.With the development of economy, multi-story and high-rise steel frame structures havebeen widely used. Hence, the study on the seismic behavior of weak-axis end-plateconnections and semi-rigid steel frames will be of great necessity.Based on the analysis above, the main content of this thesis is depicted as follows:(1) Monotonic loading tests and FEM analysis were conducted on four weak-axisend-plate connections, in which two were border-column and the other two wereinterior-column, to make clear the stress distribution, plastic development, deformationproperties, semi-rigid features and failure modes of this kind of connections. The differencebetween the bending capacity and initial rotation stiffness of border-column andinterior-column end-plate connections were quantified.(2) The effect of different parameters on the rotation was analyzed through thesensitivity analysis method based on correlation, and the moment-rotation relation model ofweak-axis end-plate connections in the elastic stage was established.(3) An accurate, simple, practical calculation method of moment-rotation curve andhysteretic loop were proposed which mainly concerned about bending stiffness in elastic stage,elastic ultimate bearing capacity and yield bearing capacity.(4) Static loading tests and quasi-static loading tests were conducted on semi-rigidframes using end-plate connections to investigate the failure process, failure modes, hystereticbehavior, displacement ductility coefficient, horizontal resistent rigidity and rigiditydegeneration of this kind of frames. Several suggestions were proposed for the designing ofsemi-rigid space steel frames.(5) Nonlinear FEM analysis was conducted on the semi-rigid steel frames usingend-plate connections through ABAQUS which took the initial geometric imperfections intoconsideration. Compared with the test results, good agreement were achieved whichconfirmed the accuracy of FEM analysis.(6) Another FEM software OpenSees was also used to conduct nonlinear analysis on thesemi-rigid steel frames using end-plate connections. In these FEM models, the constitutive relationship between moment and rotation proposed above was adopted. The analysis resultscoincided well with the test results, which verify the accuracy of the proposed constitutiverelationship of end-plate connections and the reliable of FEM analysis. Dynamic analysis wasconducted on semi-rigid steel frames using OpenSees to study the influences of connationrotation stiffness on the natural vibration period and top-floor displacement.(9) A judgement standard about the semi-rigid interval was proposed based on the basicnatural vibration period, which was certified by theoretical deduce and examples.