| Under the background of the level of urbanization in China,buildings with large span and large space gradually become the representative of the degree of urbanization.In large buildings,single cable curtain wall as a kind of prestressed geometric nonlinear flexible system,forms stiffness to resist external load by applying pre-tension to curtain wall cable in advance,so cable is undoubtedly one of the most important components of large buildings.The cable force determines the safety and stability of the structure.The stress state of cable directly affects the safety level of the whole structure,so the research on the prestressed cable is particularly important.Based on the fact that there are few specific researches on prestressed cable of large cable net structure,,the vibration information of cable is obtained through field dynamic test,using response surface methodology,the initial model of single cable and cable net is modified by finite element method with frequency as response information,and the accurate cable model under service condition is obtained.Based on this model,different working conditions are set for damage research,which provides a basis for health monitoring in practice.The main work and conclusions of this study are as follows:(1)In this paper,a finite element model of cable,which is made of strung steel wires,is established by using solid element to accurately reflect the stringing of steel wires,improves deficiency of the model element approximation in previous studies and a rotating spring is proposed to simulate the steering device of cable,which reduces the calculation error caused by the simplification of the model and improves the accuracy of the model.(2)The PSO+Kalman is used to de-noise the measured signal,and the filter parameters are determined more accurately by fitness function of PSO,which effectively avoids the disadvantage of traditional Kalman algorithm that is hard to acquire statistical characteristics of noise.The effectiveness of filtering is guaranteed to a greater extent when the denoising signal is combined with the SNR test.The signal processing method in this paper can reduce the interference very well,which provides a reference for the signal processing of the field detection work.(3)Aiming at the situation that the physical structure of cable net is too large,a proper simplification is made on the basis of ensuring the calculation accuracy.According to the actual structure,the model considers that only the 8-layer cable network between two steel columns is modeled and calculated,and the cable network model of different heights is established to output the frequency response of the measured position of the sensor.The model frequency response is compared with the measured signal to verify the accuracy of the 8-layer cable network model.(4)It is found that cross-sectional area,density,elastic modulus,interaction terms and quadratic terms have significant effects on vibration;It has been proved that the influence of anchors can be ignored during modeling;A rotating spring constraint is proposed for the steering device,fixed-adjustment end is closer to full consolidation,and the cable with steering device is closer to one end of consolidation and one end of rotation spring restraint.After the correction,the vibration error of the model is reduced to about0.5%,and the response surface method has good adaptability to higher order modes,which verifies the effectiveness of cable model modification.(5)The damage and revision of cable force calculation formula was studied based on the modified model.For a single cable,the vibration of the cable is not affected by the same damage at both ends,and the influence degree is positively correlated with the order.The vibration is greatly affected by the damage of different restraints at both ends,and the influence degree is negatively correlated with the order.In the case of stiffness reduction damage,the damage number have significant effects,which are positively correlated with the frequency order,and the end damage is the most serious;Influence degree of injury type: asymmetric > intensive >symmetric;For cable net,a cable damage will increase the surrounding cable force,the increase amplitude is negatively correlated with the distance from the damaged cable.Anchor end damage has the greatest effect on other cables.The modified string and beam theory can be well adapted to cable force calculation of cable net system.In this paper,based on the finite element dynamic analysis,dynamic test and response surface model modification,the system of large cable net is deeply studied,which provides a reference for the health monitoring work of similar long-span buildings in practice. |
