Axial Compressive Behavior Of Recycled Concrete-filled Thin-walled Square Steel Tubular Stub Columns

With the wastes of building have been growing day by day, In particular, mostof them are waste concrete. It’s harm to the society and environment. At the sametime, as the recycled concrete have the defects of smaller apparent density, lowerstrength and elastic modulus, bigger shrinkage and creep, poorer liquidity and so on.All of this greatly hinders the Promotion and application in actual structures. In orderto solve this, the thesis introduced the research of the recycled concrete-filledthin-walled steel tubular stub columns. Because the concrete-filled thin-walled steeltubular could take advantages of the two kinds of materials adequately, and it hashigh strength, good plasticity and convenience of erection. Meanwhile, It couldreduce the consumption of the steel and the cost. The recycled concrete-filledthin-walled steel tubular is the new structure with the similar introduction of featureabove. Referring to the Method of the ordinary concrete-filled steel tubular,experimental tests and the finite element method were all used to study thefundamental mechanical behavior of the recycled concrete-filled thin-walled steeltubular stub columns. The conclusion of the thesis was such as follows:The main experimental parameters are the replacement ratio of the recycledaggregate from wasted concrete in construction, the width-thickness ratio of thethin-walled steel tubular, the strengths of concrete filled in the steel tubular. Twelverecycled concrete-filled thin-walled steel tubular stub columns are tested. Thebehavior of the recycled concrete-filled thin-walled steel tubular stub columns isanalyzed. Parametric analysis is performed on the influences of bearing capacities ofthe composite members. Test results show that:(a) The initial rigidity of the recycledconcrete-filled thin-walled steel tubular is close to that of the ordinary concrete-filledthin-walled steel tubular. With the replacement ratio of the recycled aggregate fromwasted concrete has been growing within a range of30%-50%, the bearing capacityof the recycled concrete-filled thin-walled steel tubular stub columns decreased, butthe influence to the bearing capacity is limited.(b) With the increasing of steel ratioand the strengths of concrete filled in the steel tubular, the bearing capacity of therecycled concrete-filled thin-walled steel tubular stub columns is increasing.(c) Theorder of influence in bearing capacity from high is the steel ratio, the replacementratio of the recycled aggregate from wasted concrete and the strengths of concretefilled in the steel tubular. The order of influence in ductility capacity from high is thethe replacement ratio of the recycled aggregate from wasted concrete, steel ratio andthe strengths of concrete filled in the steel tubular.(d) The axial compressive strengthsof the specimens with the recycled concrete-filled thin-walled steel tubular stubcolumns can be determined according to the current design codes of EC4(1994) andconsidering a reduction factor of0.99. Load-deformation relationship curves of the recycled concrete-filled thin-walledsteel tubular stub columns subjected to compression are analyzed by finite elementmethod. The predicted load versus deformation relationship curves are in goodagreement with those of tests. It demonstrates that the numerical method is reliable inpredicting the load versus deformation relationship. The influencing factors of thestrengths of concrete filled in the steel tubular are analyzed and the result is that: withthe increasing of the width-thickness ratio, the binding force to the concrete from thethin-walled steel tubular is decreased. When the width-thickness ratio is fixed, thebinding force is decreased with the the strengths of concrete increasing and thebinding force is increasing with the replacement ratio of the recycled aggregate fromwasted concrete increasing.