Study On The Influence Of Suspender Breakage On Mechanical Properties Of Tied Arch Bridge

Suspenders are the transmission members of tied arch bridges.Their integrity determines the safety of tied arch bridges.The breakage of suspenders may lead to local damage or even overall collapse of structures.In this paper,based on practical engineering,the influence of suspender breakage and fracture on the mechanical properties of concrete filled steel tube tied arch bridge is studied by combining indoor model experiment with finite element simulation analysis.The main contents and achievements of this paper are as follows:?1?Structural robustness is introduced into the study of suspender breakage,and the importance coefficients of 34 Suspenders of background Bridge Based on robustness are obtained.Among them,the importance coefficient of the suspender near the arch foot,1/4 span and midspan is larger,which reflects that the suspender breakage at this place has a greater impact on the bearing capacity of tied arch bridge.Taking the suspender at the above control section as the research object of suspender breakage,combining with the knowledge of material mechanics and structural finite element analysis,the evolution law of stress and internal force in the process of Suspender Damage is analyzed theoretically,and the theoretical curve between the internal force of suspender and the degree of damage is obtained.With this curve,the damage degree of the damaged suspender can be deduced by periodically detecting the change of the internal force of the suspender in practical engineering,and the remaining service life of the damaged suspender can be predicted,so that the damaged suspender can be replaced as early as possible to avoid the breakage of the suspender.?2?The influence of suspender breakage and fracture on the mechanical properties of tied arch bridge is studied.The results show that the internal force of suspender decreases and the stress increases rapidly after the damage occurs,while the influence on the other suspenders is small.The maximum stress increase of the other suspenders is about 10%,and the stress value of the suspenders far from the damaged suspenders is almost unchanged with the increase of the damage degree.After a single suspender breaks,the stress state of the structure is different from that of the suspender"damaged but not broken".The stress increment of the three suspenders adjacent to the broken suspender is larger,the maximum increment is about 30%.Under dead load,the tension stress values of the remaining intact suspenders after a single suspender breaks all meet the requirements of the??0.33f_tpk.The maximum vertical displacement of arch ribs and main girders is about 3 mm,and the maximum compressive stress of concrete meets the specification requirements?_c?[?_b],and there is no tension stress.?3?The asymmetric and symmetrical fracture of suspenders along the transverse bridge are studied.The results show that the suspender is unsymmetrically broken,the structure is no longer symmetrical in the transverse direction of the bridge,the main girder torque increases obviously,the main girder rotation angle increases,and the stress and displacement differences between the upper and lower sides of the main girder cross-section occur.The symmetrical fracture of the suspender has no effect on the torsional effect of the structure,but the stress value of the suspender adjacent to the broken suspender increases greatly,and there are two or more consecutive broken suspenders in the span.Tensile stress appears at the lower edge of the main beam,and cracks may occur in the concrete of the structure,which may cause the collapse of the structure.?4?Ritz method is used to solve the critical load of arch bridge.The results show that the non-directional force of the suspender plays an auxiliary role in the stability of the double-ribbed arch,while the reduction of the internal force of the suspender caused by the breakage of the suspender and the increase of the distance between the suspenders caused by the breakage of the suspender weaken this auxiliary role to a certain extent.The stability coefficient of arch rib is less than the allowable value under the action of main force and additional force,and the arch rib is likely to lose stability.?5?Using the function of MIDAS/civil"unknown load coefficient method"to calculate the tension force of the new suspender after breaking,the tension force of the new suspender calculated by this method can realize one-time tension forming of the new suspender without repeated cable adjustment;the influence matrix of the tension force of the suspender relative to the vertical displacement of the control section of the main beam is solved,and the conclusion of this paper is illustrated from the angle of the influence matrix.