Study On Lateral Stiffness Of The Frame With Precast Hybrid Steel-Concrete Beams

In recent years,the proportion of prefabricated buildings in China is rising under the guidance of relevant national policies,the industrialization of construction has gradually developed into an inevitable trend of construction industry in the future.In order to accelerate the application of precast components in practical engineering,the mechanical behavior of different precast components has raised numerous scholars concern.The hybrid steel-concrete beams can be assembled adopting the connection methods of steel structures,which have a coincident characteristics of assembled construction,meanwhile,it has many advantages such as convenient construction,short construction period and et al.On the basis of previous researchers,a further study was carried on the mechanical performance of the frame structure with precast hybrid steel-concrete beams,and provided the theoretical basis for hybrid beam engineering applications.The singular function was used to derive the deflection formula of the hybrid steel-concrete beam under the action of angular displacement and linear displacement at the beam end,based on the test results of previous literatures,the deflection curve of precast hybrid steel-concrete beam in elastic-plastic stage was analyzed.Besides,the stiffness matrix of precast hybrid steel-concrete beam was obtained under the local coordinate ignoring effect of shear deformation.The reduction coefficient was defined and the rationality of equivalent calculating method which will simplify the analysis of the frame structure including precast steel-concrete hybrid beams was proved,and the trend of lateral stiffness of frames was analyzed.Finally,finite element models were created respectively,and the results were compared with the theoretical ones.The results indicate that the theoretical deflection curve considering shear deformation is closer to deflection curve of the finite element model,furthermore,the established uniform beam frames by using reduction coefficient fit well with precast hybrid steel-concrete beam frames under horizontal loads,and it shows that equivalent method has high accuracy.The stiffness matrix of precast hybrid steel-concrete beam with semi-rigid connection was deduced on the base of boundary conditions of the fixed precast hybrid beam.A one-story one-span frame was used to analyze the influence of rotational stiffness on lateral stiffness,the effects of length ratio α,rigidity ratio e and rotational stiffness k on lateral stiffness were studied,and the results show that lateral stiffness increases with increase of k and e,and decreases as α increases.Besides,the lateral displacements of three stories frames under horizontal loads were calculated by displacement method and finite element method were used to compare with the calculated results.The results show that the effect of rotational stiffness variation on lateral stiffness will become more significant with decrease of α or increase of e.The lateral displacements of frames fit well with the finite element analysis results to prove the deduced stiffness matrix is accurate.The lateral displacements and story drift will decrease with increasing rotational stiffness.Finally,the practicability of reduction coefficient was verified through actual engineering examples.