Experimental Study On Flexural Behavior Of Fiber Lightweight Aggregate Concrete Flat Beams

The application of flat beam can reduce the height of the layer,increase the net height,and meet the requirements for the use space.The decrease of the effective height of flat beam make the bearing capacity and capacity of resistance to deformation and cracking lower.Under the same load,the flat beam need more construction material than the normal beam and has a larger self-weight.In view of the better inhibition of the fiber on the expansion of the crack and the improvement of the stiffness and bearing capacity of the concrete beam,and the light aggregate concrete has the advantages of light weight and high specific strength,this paper studied the bending performance of fiber lightweight aggregate concrete flat beam.In this paper,three lightweight aggregate concrete flat beams,eight plastic-steel fiber lightweight aggregate concrete flat beams and six steel fiber lightweight aggregate concrete flat beams were loaded to study the rules of reinforcement ratio(0.97%,1.30%,1.62%)and fiber content(0,0.3%,0.6%,0.9%,1.2%)on crack development,failure morphology,steel strain,concrete strain,deflection,short-term stiffness,cracking load,yield load and ultimate load of the fiber lightweight aggregate concrete flat beam,establishing the calculation formula of short-term stiffness and the the bending capacity of plastic steel fiber lightweight aggregate concrete flat beam,verifying the applicability of the current specification to the calculation of short-term stiffness and flexural capacity of steel fiber lightweight aggregate concrete flat beam.The results show that the fiber can be incorporated into the lightweight aggregate concrete to inhibit the crack propagation and reduce steel strain and the concrete strain in the compression zone,the more the fiber content,the better the effect.Incorporating fibers into lightweight aggregate concrete flat beams can effectively improve its stiffness and bearing capacity.Based on the effective moment of inertia method and analytical stiffness method,the short-term stiffness formulas of plastic steel fiber light weight concrete flat beams are derived,and the formula of flexural bearing capacity of plastic steel fiber lightweight concrete flat beams is established.The calculated results are consistent with the experimental results.According to the bending capacity and short-term stiffness formula of steel fiber reinforced concrete beams specified in the technical specification of fiber reinforced concrete structures(CECS38: 2004),the steel fiber light weight concrete flat beams are calculated.The calculated values of bending capacity are consistent with the experimental values.The steel fiber influence coefficient in the short-term stiffness formula has been specifically revised to provide a reference for the application of steel fiber lightweight aggregate concrete flat beams.