Research On The Damage Of Hangers Of Concrete-Filled Steel Tubular Arch Bridges

In the recent twenty years, boasting the merits of the reasonable loading mechanism,lower construction cost, the handsome form and so forth, the steel pipe concrete archbridge has been increasingly preferred by many bridge designers, and thus developingrapidly. However, some problems are gradually exposed during the operation periods ofmany bridges of this type, such as dilapidation of the bridge's load-transfermember—hangers. Such problems are deleterious to the health condition of the bridges.Through the analysis of the widespread dilapidation phenomena of the hangers,combining the construction features of the hangers of the steel pipe concrete arch bridges, aconclusion is reached in the thesis that corrosion and fatigue are the most important causesfor the dilapidation of the hangers. The improper protection measures of the hangers maylead to their corrosion and dilapidation, and the fatigue due to the stresses caused by thelive loads could mainly explain the dilapidations.The fatigue properties of the hangers in the calculation models of the rigid tied beamsand rigid arches are analyzed in the thesis, based on the various factors influencing thefatigue properties of the hangers, such as the location and spacing of the hangers, the ratioof the distance between the side hanger and the spring to the spacing between theintermediate hangers, the mobile impact, the bridge's arch rise-span ratio, the ratio of thestiffness of the arch to that of the beam, and so forth. Some conclusions can be finallyreached: the maximum stress and the stress amplitude of the intermediate hangers arelarger than those of the side hangers;the spacing of the hangers shouldn't be too large, andalso shouldn't be too small considering the construction measures and in order to be morehandsome in form;either too big or too small distances between the side hanger and thespring would increase the stress amplitude of the side hanger;the mobile impact calculatedaccording to the new codes would increase the stress level of the hangers, therefore theinfluence of the impact shouldn't be overlooked;the influence of the arch rise-span ratioand the ratio of the stiffness of the arch to that of the beam on the maximum stress and thestress amplitude of the hangers is comparatively small. For the continuous arch bridge orthe rigid framed tied arch bridge, the thermal difference and the mobile brake force couldproduce rather adverse influences on the side hangers, thus special construction measuresmust be taken in design.Preservation could be guaranteed through proper protections, which could be improvedby better construction measures. Combing specific design examples, some new protectionmeasures are proposed in the thesis, which are expected to be able to ameliorate theprotection effects.