| The stay cable is an indispensable force component of cable-stayed bridge,which plays an important role.The value of cable force is an important parameter to evaluate the safety of cable structure.In engineering practice,the cable force of cable-stayed bridge is usually measured by frequency method.When the cable is not installed with shock absorber,the cable force calculated by simplified formula of cable force can meet the engineering requirements.However,when the shock absorber is installed on the cable,the error between the cable force calculated by the simplified formula and the actual cable force is large.It shows that the simplified calculation formula of cable force can not meet the cable force calculation of cable with shock absorber.In this paper,based on an asymmetric cable-stayed bridge with single tower and double cable planes,the analytical solution of cable free vibration without shock absorber and the calculation formula of cable force under general boundary conditions are analyzed.At the same time,the calculation formula of cable force considering bending stiffness is analyzed,and the calculation value of cable force considering bending stiffness is compared with that without bending stiffness by using actual engineering data.The energy method is used to deduce the calculation formula of cable force with shock absorber,and the formula is verified by the actual engineering data.The spatial finite element model of the whole bridge is established by using the finite element software to calculate and analyze the influence of temperature effect on the cable force;meanwhile,the cable breaking is simulated and the influence on the cable force under the condition of cable breaking is analyzed.Through the analysis of engineering examples and finite element model,the results show that:(1)For this type of asymmetric cable-stayed bridge,the influence of bending stiffness can be ignored in practical engineering.(2)The formula of cable force deduced by energy method is correct and meets the requirements of practical engineering.(3)The cable forces at different positions of asymmetric cable-stayed bridge are different due to temperature effect.Under the action of overall temperature rise and fall,the cable force near the main tower changes greatly.Under the effect of the gradient temperature of the main girder,the cable force of the No.8 cable of the steel main girder changes most.Under the action of temperature difference between the left and right sides of the main tower,the cable forces on the outer side of the steel box girder and the outer side of the concrete girder vary greatly.Under the effect of cable beam(tower)temperature difference,the cable on one side of the concrete beam is greatly affected by the temperature difference between the cable beam(tower),and the cable on the side of the steel main beam is affected by the temperature difference of the cable beam(tower),and the influence on both sides is larger than that in the middle.Then,when setting the cable force of the bridge,the change of cable force caused by temperature effect of different parts and lengths of cables should be considered.(4)When the cable of the asymmetric cable-stayed bridge breaks,the main tower will tilt to the side of the cable which is not broken.The farther the anchor point on the beam is from the main tower,the more inclined it is,and the greater the influence on the cable force of the remaining unbroken cables.When a cable is broken,the cable next to the broken cable will be affected most,and this effect will be weakened with the increase of the distance between the cable and the broken cable.When single cable is broken,the cable force of the side with broken cable is larger than that of the side without broken cable.The influence of broken double cable on cable force is greater than that of single cable.The research results of this paper have certain guiding significance for the design,construction and later operation of this kind of bridge. |
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