Research On The Effect Of Cast-in-situSlab On"Strong Column-Weak Beam"Mechanism Of Reinforced Concrete Frame Structure

"Strong Column-Weak Beam" mechanism is one of the basic principles of seismicductility design of reinforced concrete frame structure. However, it’s difficult to realize"strong column-weak beam" failure mode in earthquakes due to the effects ofcast-in-situ slab, infill wall and axial compression ratio of column, etc. The effect ofslab contributes more among all these factors. As a general finite element analysissoftware for structural numericalanalysis, ABAQUSis with powerful nonlinear analysiscapability and provides abundant re-development interfaces.However, it is difficult andcomplex to establish the numerical model of RC frame structure with the software ofABAQUS because it cannot realize parametric modeling at present.To improve and simplify the modeling procedure of the softwareABAQUS,thepaper has developed a series of plug-ins to realizeparametric modeling.. Then, threesets of RC frame structures with different types includingnormal frame, frame withoutslab, frame without slab but with mass are modeled and simulated. The modal analysisand Push-over analysis are performed to explore and assess the effects of slab onstructuralintegral stiffness and beam flexural stiffness.The main contents and contributions of this paper are summarizedas below:(1) The computing efficiency and results are compared among different materialmodels, element types, analysis steps and loading methods in ABAQUS, then the mostproper and effective modeling method is selected and improved. The software plug-ins,including "Create RC Frame Structure" and "Create CDP Model", and the softwarescript"Modeling simplification" are developed and programmed based on Pythonwhichisa kind of re-development interface compute language.(2) Considering the characteristics of the normal frame, frame without slab, framewithout slab but with mass, and RC frame structural numericalmodels are establishedbased on the plug-ins developed in the paper. The natural frequencies and the baseshear-top displacement curves of all the models are compared and analyzed by usingmodal analysis and Push-over analysis respectively. A new parameternamedlateralstiffness amplification factor is presented to measure the effect of the slab on RC framestructure stiffness. It is found that its value increases with the increasing of beamheight, but decreases with the increasing of beam length. Furthermore, the empiricalformulafor calculating the lateral stiffness amplification factor is obtained by regression and linear fitmethod.(3) According to the concept of effective flange width of the beam with positivebending moment, the theoreticalcalculation formula for the effective flange width ofthe beamwith negative bending moment is derived and proposed. The effective flangewidthincreases with the beam height, and decreases with beam length. Furthermore,the effective flange widths of the beams of all the numerical structures with slab arecomputed and analyzed. Based on the numerical simulation results, the empiricalformula for calculatingthe effective flange width is obtained by using linear regression,considering the depth and span of the beams.