| The partial concrete-filled rectangular steel tubular truss is a new kind ofstructural system that consists of rectangular steel tubular and filled concrete, thechords are steel tubular or concrete-filled steel tubular members and the web arerectangular steel tubular members, and the chord and web are directly connectedwith welded joint. It is a new long span and heavy load structure and has a goodapplication prospect in bridge engineering. Supported by the programs fromWest Transport Construction Science and Technology(2006319812112) andApplied Basic Research Programs of Transport Ministry (2006319812130),the mechanical behaviors and failure mechanisms of this new structural systemwere studied in this paper, and made it use in the continuous rigid frame bridgeand truss type ribbed arch bridge, which solved the problems of design andcalculation about these bridges, and provided the theory basis for theirapplication in bridge engineering.The main study contents and achievements are summarized as follows:(1) The microscopic element analysis model of PCF rectangular steeltubular truss was researched. Based on the constraint concrete overall straincracks constitutive model, using the large general finite element program ofMidas/FEA with plate and shell and solid unit, the PCF rectangular tubular steel tubular truss model was established to analyze its mechanical behaviors andcompared with the test results. The results show that the finite element analysisare in good agreement with the test results, and the microscopic analysis modelestablished in this paper can accurately analysis the mechanical behaviors of thePCF rectangular steel tubular truss, which is reliable to be used to analysis theinfluence parameters of PCF rectangular steel tubular truss.(2) The influence parameters of the mechanical behaviors of the PCFrectangular steel tubular truss were studied considering the effects of the twoparameters, which were width ratio of web and chord β and the ratio of chordwidth and thickness γ. The main conclusions indicated that the width ratio ofbranch and chord β affects the failure mode of the truss greatly, and with theincreasing of β the failure mode of the truss changes from nodes failure to rodsfailure. The ratio of chord width and thickness γ influences the carrying capacityof the truss more, and with the increasing of γ the carrying capacity of the trussfell sharply and then become stable gradually.(3) The macro element analysis model of PCF rectangular steel tubulartruss was researched. Based on the unified theory of concrete-filled steel tubular,the constitutive relationship of the concrete-filled steel tubular member’s plastichinge was deduced. Adopt the plastic hinge element and using the large generalfinite element program of Midas/CIVIL, the macro element analysis model of PCF rectangular steel tubular truss was established, and the carrying capacity ofthe truss and the failure position and arisen order of plastic hinge were analyzed.The results show that the macro element analysis model established in this papercan accurately grasp the mechanical behaviors of the PCF rectangular steeltubular truss, and it is feasible to be used in the analysis of the PCF rectangularsteel truss bridge, and it is beneficial in bridge elastic-plastic state analysis andthe weak position judgment.(4) The application research of PCF rectangular steel tubular truss incontinuous rigid frame bridge was carried out. Based on the Xiang Jia Ba Bridge,the finite element model of PCF rectangular steel tubular truss continuous rigidframe bridge was established to analysis the static and dynamic properties in theelasticity and plasticity stages; meanwhile the range of the concrete-filled in thegirder was optimized. The static performance analysis shows that PCFrectangular steel tubular truss bridge has technical advantages in the middle spandeflection, member internal force and stress level, bearing capacity and plasticdeformation. The dynamic properties analysis shows that the dynamic behaviorof PCF rectangular steel tubular truss bridge is improved compared with emptysteel tubular truss girder bridge, but decrease when full concrete-filled.(5) The application research of PCF rectangular steel tubular truss in trusstype ribbed arch bridge was carried out. Based on the Shi Tan Xi Bridge, the finite element model of PCF rectangular steel tubular truss ribbed arch bridgewas established to analysis the static and dynamic properties in elasticity andplasticity stages; meanwhile the range of the concrete filled in the arch rid wasoptimized. The static performance analysis shows that PCF rectangular steeltubular truss bridge has technical advantages in the vault deflection, memberinternal force and stress level, bearing capacity and plastic deformation, butmore attention should been pay to the stiffness mutations of arch rib. Thedynamic properties analysis shows that the dynamic behavior of PCFrectangular steel tubular truss bridge is decreased compared with empty steeltubular truss bridge, but still excelled in the full concrete-filled arch bridge.(6) The structural deformation, internal force and stress of members wereinfluenced by the filled length of concrete. The deflection, internal force andstress level of the PCF rectangular steel tubular truss bridges are in a optimalstate when the filling coefficient is0.184~0.395in continuous rigid frame and0.231~0.442in truss type ribbed arch bridge. |
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