Experimental Research On Flexural Behavior Of Reactive Powder Concrete Structure

Reactive powder concrete (RPC) is one kind of cement-based composite material with many excellent performances such as high strength, high toughness, high durability and so on, which has broad application prospects.At present, studies of RPC in China mostly focus on material performance rather than structural design. Because of RPC’s high tensile strength and large elastic modulus,when superposed with steel orthotropic plate,it will significantly increase the bending stiffness of orthotropic plate with only small thickness. As a result,the weight of superimposed bridge deck slab is significantly reduced. However,there are a lot of groundwork to be done before RPC applied to bridge decks. In this paper,we used the theoretical analysis combined with experimental methods to study the flexural properties of RPC slabs (including superimposed slabs. The main work and conclusions are as follows:According to the measured crack bending moment of 20 reinforced slabs of RPC and 16 steel-RPC superimposed slabs. Based on plane section supposition, the formulas for calculating the cracking moment of the two were derived. On this basis, by using the measured data of the paper and other people, the formula for calculating RPC tensile strength about the volume content of steel fiber was established based on the regression analysis. Considering that the two are flexural members, the unified calculation formula of cracking moment is established.For the RPC material, the steel fiber can still bear the tensile strength after the cracking of the cement base. The calculation methods of stress reduction coefficient and equivalent stress in compression zone and equivalent depth of the compressionzone are derived after the tensile zone of reinforced slabs of RPC cracked. Based on this, the normal section flexural strength calculation formula of reinforced slabs of RPC is established. At the same time, the transformed section method is used to convert the steel plate into concrete slab with the same thickness.Pointing out the two kinds of force mode whose neutral axis of steel-RPC superimposed slabs is located in steel plate or concrete slab. Then the formula of calculating the bearing capacity is obtained. Meanwhile, the bounding relative height of compression zone and critical reinforcement ratio of reinforced slabs of RPC in this paper.Considered the contribution of the RPC in the tension zone, this paper obtained the moment of the tensile force of longitudinal steel bar about the point of resultant force on compressive region of RPC slabs under the normal use stage at all levels by using the measured strains of reinforcement steel.Through the regression analysis of the parameters, the calculation formula of the stiffness of the reinforced slabs of RPC is derived. Considered the influence of reinforced protective layer thickness, this paper established the calculation formulas of maximum crack width of reinforced slabs of RPC by reference to calculating methods of crack width of reinforced concrete beams with steel bars and fibres.According to measured moment-deflection relationship curves of steel-RPC superimposed slabs, measured stiffness are put forward. Based on the method of valid inertia, the effective stiffness formula of superimposed slabs was deduced by making the numerical approximation, So as to get the calculation formula of the deflection of the superimposed slab. Ignore the slip between steel slab and RPC slab, this paper obtained the calculation formula of crack width under negative bending moment by introduce the crack height and reference to calculating methods of crack width of reinforced concrete beams with steel bars and fibres.