Nonlinear Analysis Of R/C Sections Based On MCFT

The effect of shear on the nonlinear sectional analysis is often ignored when theshear span ratio is large, it is believed to be appropriate as it brings little error. But if theshear span ratio is relatively small, the effect of shear can not be ignored in this way,hence a modeling method that can take both flexure and shear into account is stronglydesirable. It is an effective analysis method that the modified compression theory(MCFT) being implemented to carry out the nonlinear sectional finite analysis of RCmembers. This method can be used to analyze accurately the complete load-deformationresponse of RC members loaded in combined shear, moment, and axial load.A nonlinear sectional finite analysis program Response2000 based on the MCFTwas developed by Evan C.Bentz. Later a traditional nonlinear sectional program alsobased on the MCFT was developed independently by JianFeng Huang in 2004. Both theabove two programs can simulate monotonic load condition, but none of them can dealwith more general load conditions.It was known that flexural deformation and shear deflection affect each other, but alittle research was done on the analysis of the effect of shear deformation on thecurvature under cyclic loading conditions. The paper discusses the relation betweensectional shear-shear deformation hysteretic curves and moment-curvature hystereticcurves, the effect of shear deformation on member load-deflection curve especiallyhysteretic curve, and the difficulties of the sectional hysteretic analysis using MCFT andsecant formulation.The main points of this paper are as follows:①　An algorithm documented by Batoz.J.L was modified and a secantdisplacement control method serves reinforced concrete nonlinear finite analysis wasput forward in this paper. The validity of the method was tested by simulating a numberof experiment tests under cyclic loading. It was proved to have high precision,stabilization and convergence rapidly by using the displacement control method whensimulating monotonic loading condition and cyclic loading condition.②　　A reinforcement concrete nonlinear sectional finite analysis program based onMCFT and secant method is first developed all over the world by C++ in this paper.And a number of problems such as dealing with the memory and judgment of elementhistory conditions, the abnormity of the secant stiffness matrix not faced in traditionalsectional hysteretic analysis program are successfully solved. Different from thesectional hysteretic analysis program which can only include moment and constant axialload, program in this paper can include the moment, shear, axial load, and has thepotential to include varying axial load. This paper has established a good basis for thestudy group to do the next work. ③　Simulations of specimens tested by R.Park, D.C.Kent and R.A.Sampson usingthe program were carried out. It was indicated by the result that the hystereticcharacteristics of unsymmetrical reinforced section under unsymmetrical cyclic loadingconditions were well simulated. Satisfied results were got when simulating specimenstested by Sheikh and Xingrong Li using the program. Simulations of specimenssubjected to varying axial load tested by Xingrong Li using the program were carriedout too. Good calculated N ? M ?? curves indicated that the sectional nonlinearanalysis program has the potential to analyze RC members loaded in combined moment,shear and axial load. ④　A load-deflection analysis for a series of simple support beams tested at theUniversity of Toronto is also presented in the paper. The program used is basingon thenonlinear sectional finite analysis program presented above. Then comparison amongtest curves, calculated curves not including shear and calculated curves including shearwas done. Principium conclusions are as follows: The results show that effect on the deflection can not be neglected of simplesupported beam whose shear span ration is smaller than 5; and not the same for simplesupported beam whose shear span ration is bigger than 7. Shear has little effect on thesection curvature, namely has little effect on moment-curvature response; on thecontrary, the effect of shear on member deflection namely load-deflection response isnotable.