Theoretical Analysis And Experimental Study On Large Span Steel-Concrete Composite Open-web Plate

With the development of society,urban land use is in an increasingly tense.National policy has been encouraging the rapid development of multi-layer public and industrial buildings.However,due to the large span of public and industrial buildings,conventional concrete and steel floor structure are hard to meet the floor ceiling height,the amount of steel and other requirements.Therefore,this paper puts forward a kind of construction of long span assembled monolithic steel-concrete composite open-web plate,which not only meets the relevant requirements,but also has the advantages of graceful shape,strong span ability,construction civilization,high industrialized degree,etc.The system of long span assembled monolithic steel-concrete composite open-web plate mainly consists of lower steel rib-beam,cast-in-place reinforced concrete upper rib-beam,precast reinforced concrete ribbed slaps,as well as shear key connector connecting upper and lower surface layers and making them work together.The construction uses pairwise orthogonal double deck chord to compose cross rib.At the cross point,vertical shear key are set,with connecting the upper and lower rib beam,then,a structure space is formed between their surface layers except the position of shear key.At the lower steel rib inflection point,high-strength bolt would be used to splicing connection of every unit.This thesis mainly focuses static performance,comfort and vertical earthquake action on the long-span assembled monolithic steel-concrete composite ope-web plate by means of model experiment and theoretical analysis.The major contents and results are listed as follows:(1)Prototype structure is 30 m span assembled monolithic steel-concrete composite ope-web plate,according to the theory of similarity,model structure is manufactured with a scale of 1:5,and a load test is carried out.By analyzing the deflection,stress and strain as well as acceleration time history curve,the load capacity,deformation and normal performance of the floor system are evaluated.Then,This chapter analyses the test results and the finite element calculation results by comparison.Research shows that: displacement and stress are approximate to linear variation under the design load,and the maximum displacement appeared in the central part of the floor.Macroscopic damage and crack have not been observed in the whole process of loading test,the working performance of the whole structureis good,and safe reserve is high.Experimental data match well with calculated results through the finite element method.(2)Simplified algorithm for stiffness analysis and static behavior of composite ope-web plate are specially studied.Firstly,the deformation and internal force distribution of independent composite vierendeel beam are studied by using the beam-shell mixed model.The results show that: In the upper and lower ribs,the local bending moment is decreased from the side internode to the middle internode,and in the middle internode,the local bending moment produced fiber tension on the underside of lower ribs.In addition to the bearing,the axial force for the middle section of upper ribs is pressure,the axial force for the middle section of the lower ribs is tensile,and the axial force is gradually increased towards the middle internode.The main performance of shear key is that the plane staggered,because of the axial force difference of both sides.The internal force of the shear key is gradually reduced from the bearing to the middle internode.Secondly,study on variation law of static response of the structure by changing span height ratio,grid number and the shear key section size.With the increase of span height ratio and grid spacing,the results show that displacement and maximum internal force values are increasing.With the increase of shear key section size,the displacement and internal force values are decreased.Finally,the formula for calculating the ratio of the partial bending displacement to the total displacement is derived.the equivalent flexural rigidity and the practical calculation method are given for the engineering design.(3)Comfort of the floor structure system was specially studied by the method of walking route.Firstly,selecting adverse walking routes and determine the step size.Secondly,single step drop foot excitation is applied to time history analysis.The results show that the natural frequency of the structure and the peak value of acceleration meet the requirements of the standard for comfort.When walking routes passed from the low order vibration type center,acceleration peak is larger,and acceleration response reaches the peak when walking near half of the total time.The influence of the span height ratio on the natural frequency and the acceleration of the structure is larger,and appropriate increase in the thickness of the surface layer of concrete sheet is to enhance the overall stiffness of the floor,away from the human walking frequency.(4)The vertical earthquake action of large span composite ope-web plate system was calculated by using vertical response spectrum and time history analysismethod,study on vertical seismic effect of the component and distribution of the vertical acceleration on the floor.The results showed that floor vertical displacement and internal force of the upper ribs,the lower ribs,the shear keys are small,but the response of acceleration is larger on floor middle position.The vertical component of the structure will generate additional axial force,and the effect of the layer axial force is less than 10% of the representative value of gravity load.