Study On Mechanical Properties Of Spiral Tube Hollow Floor,Structure

As a new type of floor slab,the characteristics of cast-in-place concrete hollow floor are not only light in weight and flexible structurally,but also able to reduce floor height,save energy and insulate sound.Therefore,the structure of this type is suitable for large-span buildings with relatively large loads.The stress performance of hollow floor structure varies under the condition with the filler shape and the filler status: whether the filling is inside or outside.In the current work,a new type of hollow floor structure with spiral tube filler has been put forward.Furthermore,equivalent stiffness of hollow floor,punching shear capacity of column cap,and seismic performance of hollow floor frame structure under strong earthquake have been studied theoretically.And the contents are as follows.1.The stiffness difference of cast-in-place concrete hollow slabs with molds among round core tube,oval core tube and square box are obtained.The mechanical properties of the hollow slabs formed by spiral tube filler under vertical loads are conducted further by the loading test of the single component of the hollow floor to study the strength failure and the rigidity degradation law of the hollow slab.The test findings agree basically well with the numerical results simulated by a general finite element software ANSYS.2.Two different theoretical calculation methods are adopted for equivalent stiffness of such hollow slab under vertical loads.First,the equivalent stiffnesses of this hollow slab based on orthotropic plate analytical solution,are deduced to provide theoretical basis for calculation with different mechanical models.Second,the lateral stiffness is smaller than the forward stiffness.Here,the stiffness equivalent formulas of lateral direction are revised considerately for engineering application.Finally,punching resistances of the column cap are studied with numerical simulation.The impacts of negative bending moment on the top of column cap under different spans are taken into account.The results show that the ultimate bearing capacity of punching on the column cap decreases gradually as the hollow slab span increases.The punching bearing capacities of column cap are different between different slab spans,which is always ignored in engineering design.Hence,a new type of column cap reinforcing measurement is presented,and formulas of ultimate punching shear capacity of this proposal measurement are put forward.The precision and efficiency are tested and verified by numerical simulation results.The punching shear capacity of hollow slab column joints can be extended to engineering applications.3.Damage characteristics of three kinds of frame structures with different slabs,such as cast-in-place hollow slab,equivalent slab and normal girder slab,are comparatively analyzed under strong earthquake.First,the code targets of the above structures under small earthquake are satisfied to ensure the reasonability of the structural models.The findings show that the natural periods of hollow slab structure are slightly larger than that of girder slab frame structure,but the overall code targets agree well between them.Second,the parameters of 6 and 7 degrees of seismic intensity are adapted under strong earthquake.Two natural seismic waves(Elcentro wave and Kobe wave)and one artificial seismic wave(TH1TG040)are chosen for dynamic elastic-plastic time history analysis.The failure mechanism among them similar under strong earthquake,and the concepts of "strong column and weak beam(plate strip)" are embodied by the damage patterns.Noticeably,The anti-seismic performance of the hollow slab floor under strong earthquake are slightly less than those of the beam frame structure.But it can be satisfied the requirements of seismic performance of the structure,such as garage,shopping malls,supermarkets,industrial buildings and other buildings with large span.