Research On Static Performance Of Lined Corrugated Steel-Concrete Semicircle Arch

Corrugated steel(CS)structures are widely used in bridges,culverts,granaries,and utility tunnels due to the advantages of fast construction,excellent corrosion resistance and good durability.However,for CS structures with large spans or under high lateral loading,the stability bearing capacity needs to be increased.For this purpose,a new composite structure named lined corrugated steel-concrete(LCSC)arch is proposed.To date,few relevant researches on the mechanical properties of LCSC arches are conducted,and the stress mechanism is not clear.Moreover,reinforcing old bridges with CS(i.e.CS reinforced structures)is gaining interest due to outstanding reinforcement effects and relative ease of implementation.The reinforcing method offers great significance to prolong the service life and to solve local cracking problems of old bridges.Nevertheless,in the current researches on CS reinforced structures based on field measurements,the ultimate bearing capacity and failure mode can not be obtained and the design method is unreasonable.This thesis aims to investigate the mechanical properties of LCSC circular arches and CS reinforced structures.The main rearch work is as follows:(1)Static performance tests of LCSC semicircle arches were carried out.Four kinds of arches,including the LCSC semicircle arch,the CS-plain concrete semicircle arch,the CS semicircle arch and the reinforced concrete semicircle arch,were tested under the midspan concentrated load.The failure mode,ultimate bearing capacity and ductility were obtained and compared.The strain distribution of CS at different measuring points was analyzed to reveal the composite effect and the confining effect.On this basis,the connector type of LCSC arches was optimized,and three optimized LCSC arches and one reinforced concrete arch were tested to investigate the influence of loading modes on failure modes,deformations and the internal force distribution.(2)Stability capacity design formulas of the LCSC arc arch were proposed.A solid-shell nonlinear finite element model with corrugated surface was established using the program ABAQUS and validated against test results.Three analysis methods of composite effects between CS and concrete were proposed based on fully bonded and unbonded finite element models.The influence of the material strength,initial imperfection,width-span ratio,rise-span ratio and slenderness ratio on the stability bearing capacity of LCSC arches was analyzed.Referring to the stability coefficient formulas in existing codes,the design method of LCSC circular arch under axial compression was proposed.The compression and bending distribution of circular arches under whole-span and half-span uniform vertical loadings was studied.And the design method of the LCSC circular arch under combined bending and compression was proposed with the double coefficient product design formula.(3)Static performance tests of CS reinforced structures considering the damage degree of the original structure were carried out.Three CS-plain concrete semicircle arches were tested under the midspan concentrated load to investigate the influence of bolt spacings on the failure mode and bearing capacity.Based on vertical deformations and the strain distribution of CS,the composite effect of each arch is analyzed,and a reliable bolt arrangement type was obtained to ensure the good bond between CS and post-cast concrete in the reinforcement tests.Two CS reinforced structures were tested to analyse the differences in the bearing capacity,stiffness and ductility before and after reinforcement.The influence of the damage degree was also investigated in detail.Based on the failure modes and CS strain distribution,the composite mechnism between CS,post cast concrete and original structure was revealed.(4)Stability capacity design formulas of the CS reinforced structure considering damage reduction were proposed.The nonlinear finite element model of CS reinforced structures was established considering the damage of original structure,and the life-and-death element was used to simulate the actual reinforcing process.The model was validated against test results and used to analyse the composite effect according to the strain distribution of CS and postcast concrete.The influence of the initial imperfection,primary loading level on the original structure,material strength and corrugation on the bearing capacity was studied.A design method for the CS reinforced structures under axial compression and combined bending and compression was proposed,considering the damage degree of the original structure.