| The main cable is a main bearing component of suspension bridge.With the constant increase of span length of suspension bridge,the bending rigidity of the main cable has an ever-greater impact on the geometric shape of the cable.In addition,as a jointing and force transferring component between the main cable and the hanger,the cable clamp can decompose the hanger force into distributed force.At the present stage,the frequently-used computing theory and analytical method of suspension bridge is that simplifying the main cable as a few segmental catenaries and simplifying the hanger force as a concentrated force.However,when it comes to some kind of suspension bridges like major diameters,like long cable clamps,the mentioned simplified method would bring about some error in the geometric shape of the cable and the hanger force.In order to prevent the possibly error,an optimization method of considering the influence of the bending rigidity of the main cable and the dispersing character of the cable clamp can be stuied.This thesis carries out the research around the following areas:(1)The load transferring mechanism of the cable clamp is studied based on a series of multi-scale models which take the screw tensioning and the surface contact between the cable clamp and the main cable into consideration.In this process,a total of 3 influence factors are discussed and then on this basis,a total of 3 simplified models of the cable clamp are put forward.(2)Different calculating models of the geometric shape of the cable are summarized based on the three simplified models of the cable clamp.And on this basis,a self-anchored suspension bridge and an earth-anchored suspension bridge are taken as the prototypes to study the incidence of different calculating models of the cable on the cable elevation,the hanger force and the unstrained length of hanger.(3)By using the two prototypes,totaling seven different spans of suspension bridges are redesigned,respectively.The incidence of the bending rigidity of the main cable and the simplified models of the cable clamp facing different spans of suspension bridges is analysed.Proposals of refined analysis of the main cable for different spans of suspension bridge are put forward.Analysis shows that,the vertical force of the main cable among the cable clamp presents a regular of concave parabolic.With the forming of the bending rigidity of the main cable,the force transferring path of the cable clamp shifts to its both ends gradually.In the calculation results of the geometric shape of the cable,the most accurate model is the form of uniform force,and the results of the form of two-force rods show that the cable shape is higher than the real shape all over the bridge.As for self-anchored suspension bridge,if the span of main cable is shorter than 150 meters,it should factor the dispersing character of the cable clamp into the calculating models of the cable between the tower and the quarter of span.When the span of main cable rises from 150 meters to 250 meters,the bending rigidity of the main cable should be taken into account in calculating the hanger force,and the dispersing character of the cable clamp should be taken into account in calculating the cable next to the tower.If the span of main cable is between that of 250 meters and 350 meters,both of the cable and the hanger force models should consider the influence of bending rigidity of the main cable,and the cable next to the tower should consider the influence of dispersing character of the cable clamp.When the span of main cable comes to longer than 350 meters,only the bending rigidity of the main cable should be taken into account in calculating the cable shape and the hanger force.As for earth-anchored suspension bridge,if the span of main cable is shorter than 250 meters,it should factor the dispersing character of the cable clamp into the calculating models of the cable next to the tower.When the span of main cable rises from 250 meters to 500 meters,there is no need to consider the influence of the bending rigidity of main cable and the dispersing character of the cable clamp.When the span of main cable comes to longer than 500 meters,the bending rigidity of the main cable should be taken into account in calculating the geometric shape of the cable. |
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