Analysis On Flexural Behavior Of Novel Prestressed Composite Beams With Corrugated Steel Webs

With the advantages of good mechanical performance and artistic outlook,prestressed composite beams with corrugated steel webs（PCCSWs）are widely used all over the world.But the lower concrete flange of composite beams suffers cracking problems when bending moment is applied,and it makes adverse effects on the safety and durability of the structure.Based on the above problem,this paper study on the flexural behaviors of a novel kind of PCCSWs that replaces the lower concrete flange with concrete filled steel tubes.By numerical calculation and analysis,the ultimate load carrying capacity,deformation capacity and distribution of normal stress and normal strain are discussed.The theoretical calculation method of bending moment resistance is also proposed.The main research contents and conclusions are as follows:（1）The flexural behaviors of composite beams with unbonded prestressing tendons subjected to positive bending moment were studied with different parameters.The results show that,the ultimate load carrying capacity of composite beams can be significantly increased by decreasing the span-depth ratios and increasing the yield stress of steel tubes.And increasing the concrete strength and decreasing the yield stress of steel tubes can notably improve the deformation capacity of the composite beams.When heights of corrugated steel webs increase 160 mm,the ultimate load carrying capacity has a significant enhancement about 48.2%.When the yield stress of steel tubes changed from345 MPa to 295 MPa,the ductility coefficient increased from 3.43 to 4.63.The stresses of unbonded prestressing tendons at ultimate are between 0.81f_ptk and0.86f_ptk.The k-shaped sway bracing will change the action mode of the shear lag effect.And the sectional maximum shear lag coefficient increases obviously with the width of the upper concrete flange enlarging.Based on the numerical results,the theoretical calculation method of bending moment resistance for the composite beams with unbonded prestressing tendons under positive bending moment is proposed.（2）The flexural behaviors of composite beams with bonded prestressing tendons subjected to positive bending moment were investigated.Decreasing the span-depth ratios and increasing the yield stress of steel tubes can markedly enhance the ultimate load carrying capacity of the composite beams.With the increase of concrete strength and the decline of the yield stress of steel tubes,the deformation capacity of composite beams remarkably improves,and the ductility coefficient increases by up to 35.0%.The stress increment of bonded prestressing tendons in midspan is 30%higher than that of the unbonded prestressing tendons.The distribution of normal strain along the section height and the normal stress along the transverse direction for both the unbonded and bonded composite beams are similir.The extended sandwich theory is suitable to describe the mechanical characteristics of the novel PCCSWs.Based on the numerical calculations,the theoretical calculation method of bending moment resistance for the composite beams with bonded prestressing tendons under positive bending moment is proposed.（3）The flexural behaviors of the novel PCCSWs subjected to negative bending moment were studied.The composite beams with different longitudinal reinforcement ratios,prestressing tendons ratios and span-depth ratios were considered respectively,and the stiffness degradation law is also discussed.The results of this paper can provide references for the design and calculation of the novel PCCSWs.