Research on Temperature Modes and Parameter-Related Responses of Long-Span Asymmetric Cable-Suspended Structures

Cable-suspended structures are important auxiliary structures for the construction of long-span arch bridges. Due to topographic constraints, the cable-suspended structure of Liuchehe Bridge adopts an asymmetric structure form with a main span of 736 m. Nevertheless, research focusing on the mechanical behavior of large-span asymmetric cable hoisting structures remains limited at present. Under unfavorable loads, including temperature and cable saddle friction, tower buckling failure may occur in cable hoisting structures as a result of overstress. In addition, inappropriate changes in physical parameters and temperature of the main cable will alter its sag and consequently compromise construction precision. For the sake of the safety of the cable hoisting structure, a temperature gradient experiment was conducted on the steel pipes of the prefabricated tower by virtue of a practical engineering project. The change rule of the measured point temperature was analyzed, a temperature gradient pattern for tower steel pipes was proposed, and the deficiencies of the specifications were compensated for. On this basis, the effects of variations in temperature, main cable weight, main cable elastic modulus, guy cable tension, and saddle friction resistance on the mechanical behavior of the cable-suspended structure were analyzed. According to the temperature tests on the tower steel pipes, the maximum radial temperature gradient of the steel pipe section reaches 15 °C, which is higher than the thermal gradient value stipulated in the codes. Moreover, the steel pipe stress under the thermal gradient model proposed in the current research is greater than that under the thermal gradient model in the codes. The steel tube stress under the temperature gradient model adopted in this study is 7.6 times that specified in the design code. Temperature and the elastic modulus of the main cable have a significant influence on the mid-span deformation of the main cable. For every 1 °C temperature variation, the vertical displacement at the main cable mid-span changes by 25 mm. During the construction of the main cable, the sag of the main cable should be adjusted according to the rule governing temperature’s influence on the mid-span of the main cable to avoid elevation deviations of the main cable arising from temperature. Saddle frictional resistance exerts a notable effect on tower deformation, guy cable tension, and tower stress. At a friction coefficient of 0.3, the stress caused by friction in the steel tube at the tower bottom constitutes 35.1% of the total stress under the maximum design hoisting load. During construction, the free rotation of rollers at the saddle should be ensured to reduce the mechanical response of the structure. The findings of this study can provide a basis for the design and construction of long-span asymmetric cable-suspended structures.