Experimental Study And Theoretical Analysis On Flexural Behavior Of Lightweight Aggregate Concrete Filled Steel Tube

Compared with common concrete, the density of lightweight aggregate concrete is lower by 25%~40% at the same compression strength. The structure deadweight of concrete filled steel tube can be reduced by about 20% when common concrete is replaced by lightweight aggregate concrete, which brings much advantage to the construction. As a result of its good structure behavior, the lightweight aggregate concrete filled steel tube (LACFST) has good application prospect in bridge engineering etc.Pure bending test of 21 LACFST and 8 hollow steel tubes is carried out, which the experimental parameters are strength of lightweight aggregate concrete, steel ratio and shear-span ratio. Based on the experimental study, the flexural behavior of LACFST is analyzed utilizing finite element method, and all the results are as follows.(1) Pure bending test of 29 specimens is executed using the loading modes of quartering and trisection. It is demonstrated that the flexural bearing capacity of LACFST is increased by 20%~30% compared with the hollow steel tubes thanks to the filled-in of lightweight aggregate concrete, and the LACFST is provided with good flexural ductility.(2) Parameters which affect the flexural behavior of LACFST are analyzed, and results are as follows, the flexural bearing capacity of LACFST is evidently increased with the increasing of steel ratio as well as the flexural stiffness. Lightweight aggregate concrete makes a little influence on flexural behavior of LACFST, while its flexural behavior is not affected by shear-span ratio.(3) The flexural bearing capacity and flexural stiffness of LACFST are calculated using the formula of existing criterions, which are compared with the tested values. Based on the tested results, the formulae for calculating flexural bearing capacity and flexural stiffness of LACFST are suggested.(4) Making use of the finite element program of ANSYS, the LACFST is simulated and calculated, and the moment-curvature relationship of LACFST under monotonic loading is analyzed, which the results agree well with tested ones. The moment-curvature hysteretic relationship curves under cycle loading which like spindle are full, and the good aseismatic behavior of LACFST is demonstrated.