Study On The Collapse Resistance Of Steel Moment Frames With Seismic Design And Improved Local Details

The progressive collapse of structures has drawn great attention of engineeringresearchers since the911event, by now many countries have issued relativespecifications to prevent progressive collapse of structures and kinds of designmethods and conceptions have been proposed. The beam-to-column connection, as akey part to connect the primary bearing members in moment frames, is paid evenmore attention for its critical behavior in collapse-prevention. Due to the similaritiesbetween seismic design and anti-collapse design, as many researchers have studied,the use of seismic structure for collapse prevention shows great value for engineering.This paper mainly focuses on the performance of beam-to-column connections withdifferent seismic details in progressive collapse. By using the drop hammer tester ofHunan University,6beam-to-column assemblies were designed and tested to simulatethe dynamic collapse of moment frames. Reasonable finite element models were builtusing general nonlinear FEA software ABAQUS to find out the effect of weld accessdetails in progressive collapse and the applicability of seismic design for collapseprevention. The main job of this paper is summarized as follows:(1) According to the Chinese seismic code and FEMA350standard, two kinds ofwidely used beam-to-column connections (Welded-Flange-Welded-Web and Welded-Flange-Bolted-Web connections) were designed using3weld access hole geometries,namely the standard weld access hole, the enlarged weld access hole and FEMA weldaccess hole.(2) Vertical drop hammer impact tests were carried out on the simplifiedbeam-to-column assemblies to simulate the structures’ dynamic process of progressivecollapse, the effects of connection type and weld access hole details on the structures’bearing capacity, ductility and failure modes were studied. The ductility and energydissipation of specimens were measured to evaluate the structures’ collapse resistance.(3) Numerical models of the impact test were established using general nonlinearFEA software ABAQUS, and the analysis result agreed with the experimental resultwell. A typical segmented force-rotation curve was proposed to interpret the loadingtransfer mechanism of structures under large deformation, and the catenary action’senhancement in bearing capacity was also obtained.(4) Based on the experimental and numerical results, the Alternate Path Method(APM) for collapse prevention in current specifications and its recent researchtrend were discussed. Existing calculation models for APM were introduced and theirapplicability and defects for engineering use were analyzed.