Arch Bridge Modal Analysis Of The Sling, And Tension Measurements

Because of its graceful bridge type, through and half through arch bridges are a kind of bridge with quicker development and application among all of the city bridges in our country. According to related documents and materials, there have been more than 300 through and half through arch bridges built in our country, which develop in the direction of larger span and scale, and the area of use is expanding gradually. However, in recent years, some accidents of through and half through arch bridges' collapses engendered severe casualties and economic loss related. Such a conclusion can be derived from these accidents' analyses breaking up and collapse of through and half through arch bridges mostly relating with the health condition of suspenders; if timely and real time online monitoring and diagnoses are conducted, a majority of serious accidents can be avoided.Through and half through arch bridges are mostly made up of arch ribs and floor systems ( tied beams ) and systems of suspenders. Suspender is not only a primary carrying member, but also a member vulnerable to rained. The primary damages of suspenders are rupture of some steel wires, corrosion of steel wires, lapse of anchors, and the like. Every kind of damages will bring variance of suspender's stretch stiffness. The floor system is regarded as an indeterminate structure elastically supported on arch ribs. The stiffness variance of some suspenders certainly induces the redistribution of loads. In other words, it causes the variance of static tensile forces of suspenders. The static tensile force of suspenders is a sensitive index of health condition of arch bridge. The health condition of arch bridge can be diagnosed and evaluated by comparison of the values of tension measurement of suspenders and the values of static tensile forces in the health archive of arch bridge.Currently, two methods of tension measurement, direct method and indirect method, are used in the tension measurement of suspender of through and half through arch bridges. Indirect method is mainly used in practical engineering applications. Vibration method is one of the indirect methods, which is mostly put into use. Two respects of tension measurement of suspenders by using vibration method might be involved: tension formula and measurement of vibration frequency. Now the vibration measuring technique has been already developed successfully. The vibration frequency of the suspender can be accurately obtained from the vibration signals. Theory of tension measurement of suspenders mainly depends on the theory of tension measurement of cables of cable-stayed bridge by using vibration method. Since the length of cables is relatively large, the effect of the flexural stiffness and boundary conditions is small on the tension measurement of cable-stayed bridge and can be neglected. Through and half through arch bridges are different from cable-stayed bridge. As the arch ribs of through and half through arch bridges bear compression, the bucking problem is comparatively obvious, and the value of rise of arch can not be too large. Generally the length of suspenders of through and half through arch bridges are relatively small. If the theory of tension measurement of cable-stayed bridge is directly applied to the tension measurement of suspenders, especially short suspenders,a larger error will be produced and it can not satisfy the requirements of practical engineering applications. The effect of the flexural stiffness and boundary conditions must be taken into account during tension measurement of suspenders. On the basis of this background, the raise of practical calculating formulae of suspender's tension suitable for the tension measurement of suspenders in through and half through arch bridges is the major contents of this dissertation.In the theoretical research of tension measurement of suspenders of through and half through arch bridges, when the influence of the flexural stiffness of suspenders is not taken into account, the suspenders can be regarded as a tensioned string. Sin...