| As a potent integration of high-tech concrete material and new-style compositestructure, steel reinforced high strength concrete(SRHSC) structure possesses excellentmechanical performance and seismic behaviors, which take the advantage of steel andhigh strength concrete effectively while avoiding their defects. At present, SRHSCframe columns are extensively applied to foreign and domestic high-rise buildings andsuper high-rise buildings. But the research on optimization design for SRHSC framecolumns is relatively scarce, as well as the application of SRHSC frame columns, whichlead to unreasonable structural behavior and waste of material at times. Based on thesituation above, the multi-objective optimization design for SRHSC frame columnsconsidering economy and seismic behaviors is studied in this paper. The multi-objectiveoptimization design method for SRHSC frame columns based on ductility and cost isproposed through introducing ductility index that reflects seismic behaviors of membersinto optimization objective.In order to structure the expression of ductility optimization objective function, thedisplacement ductility factor of SRHSC frame columns is studied by the experimentalresults of80C60~C80column specimens subjected to a constant axial load and cycliclateral loads at first. A4-6-1BP neural network model is built by using artificial neuralnetwork theory based on MATLAB. Furthermore, the influence law and influencemechanism of concrete strength, axial compression ratio, stirrup ratio, shear span ratioon the displacement ductility are investigated by the BP neural network model. Thedisplacement ductility factor calculation model is built based on the influence law ofevery influencing factor on the displacement ductility. The standard values in experimental data and network predicted data are converted to design values. Thedisplacement ductility factor empirical formula considering multiple influencing factorsis proposed through multi-variant nonlinear regression analysis on the converted data.The displacement ductility factor empirical formula is provided to the multi-objectiveoptimization mathematical model for SRHSC frame columns as the ductilityoptimization objective function.Combining research results of design theory for SRHSC frame columns and relatedrequirements in design specification, the multi-objective optimization mathematicalmodel for SRHSC frame columns is built through selecting design variables reasonably,setting the constraints and structuring optimization objective function with the index ofproject cost and displacement ductility. The minimum of project cost and the maximumof displacement ductility are taken as the optimization objectives, and the linearweighted method is used to establish evaluation function. The design variables includesectional dimension of SRHSC frame column and steel, the distance between sectioncenter of steel flange and section edge nearby, quantity and diameter of longitudinalreinforcement bars, diameter and spacing of stirrups. The bearing capacity requirementsof SRHSC frame columns and detailing requirements specified in current designspecification are taken as the constrained conditions. Based on the optimizationprinciple of the complex method, the nonlinear optimization problem with constrainedconditions is solved by MATLAB program. The optimization practical example showsthat the multi-objective optimization mathematical model for SRHSC frame columnsbuilt in this paper is reasonable, and the optimization method, solving procedurepresented in this paper are feasible and effective to SRHSC frame columns, whichprovides optimization design for composite structure members and engineeringapplication with reference. |
