| The slab spatial composite effect plays a significant role in the behavior ofcomposite frame structural systems subjected to lateral loads, and this dissitation mainlyinvestigates such an important effect. The mechanism, design method and numericalmodel of the slab spatial composite effect are discussed in detail, and the influence ofthe slab spatial composite effect on the seismic behavior of the whole compositestructural system is also focused on. The main research works and results are as follows:(1) The mechanism of composite frame structural systems is investigated using thebeam-shell mixed model. A beam-shell mixed model based on the general FE packageMSC.MARC (2005r2) is proposed, and the concrete cracking model, constitutive law ofthe tensile reinforcement, and the overall modeling scheme etc. are discussed in detail.The proposed model is verified by extensive experiments and examples. It can beconcluded that the slab spatial composite effect and the beam-column nonlinearity arethe two critical factors influencing the structural behavior subjected to lateral loads, andfor the fully-connected composite frames usually used in the actual practice, the slipeffect can be neglected.(2) The design methods of composite frame structural systems considering the slabspatial composite effect are proposed. Based on the shell-solid elaborate model andbeam-shell mixed model, the simplified design formulas for calculating the beam endultimate effective flange width and stiffness amplification coefficient of compositeframe beams are derived. The proposed design formulas are verified by extensiveexperiments and examples of composite frame structural systems, and can give moreaccurate predictions compared to some available design formulas provided in thecurrent codes and the literature.(3) An efficient “line” element model reasonably considering the slab spatialcomposite effect is proposed for the nonlinear analysis of composite frames. A fibermodel is developed for the nonlinear analysis of composite frames, and the constitutivelaw of the concrete material is mainly improved. The proposed formulas for effectiveflange widths at two different limit states are combined with the conventional fibermodel so that an improved fiber model, which can reasonabley consider the the slab spatial composite effect, is realized. Based on this model, a subroutine package for thenonlinear analysis of composite structures COMPONASP-MARC (Version1.0) isdeveloped, and applied to the simulations of various types of structural members undervarious load cases. The accuracy and the numerical stability have been fully verified.(4) The influence of the slab spatial composite effect on the composite structuralsystems is studied. Through the application of the developed subroutine package to theseismic elatic-plastic history analysis of a composite frame and a composite frame-corewall structural systems, it can be found that neglecting the slab spatial composite effectmay over-estimate the frequency of natural vibration, under-estimate the seismic effectand displacement responses, and give the inaccurate evaluation of the positions of weakstories, position and sequence of plastic hinge formation, failure mode and degree ofplastic damage etc. As a result, it is necessary to reasonably consider the influence ofthe slab spatial composite effect on the seismic behavior of the structural system.The proposed fiber model considering the slab spatial composite effect and thedeveloped subroutine package for the nonlinear analysis of composite structures in thisdissertation has provided a powerful research tool for the seismic catastropheperformance of composite structural systems.This dissertation is sponsored by National Natural Science Foundation of ChinaProgram (90815006) and Ph.D Candidate “Young Scholar of Distinction” of ChinaEducational Administry. |
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