Load-carrying Capacity Evaluation Of Steel-concrete Composite Tower Cable-stayed Bridge Based On Static And Dynamic Loading Tests

In this thesis,the load-carrying capacity evaluation of the cable-stayed bridge is investigated based on the static and dynamic loading tests,and a new constructed steel-concrete composite cable-stayed bridge is considered as a research background.A finite element model of the bridge with the influence of the construction error is firstly constructed,and then,a load test of the cable-stayed bridge is performed.The load carrying capacity of the bridge structure is preliminarily evaluated by using three incies,including the deflection verification coefficient,the modal verification coefficient and the deflection reserved coefficient respectively.In order to further consider the effects of some uncertainty factors,i.e.measurement noise and environmental factors,a Bayesian based finite element model updating approach is applied to calibrate the bridge model by using the measured static and dynamic measurements.Based on the updated model,the load carrying capacity of the significant componnets of the bridge is further evaluated.The main research contents and achievements of this thesis are as follows:1.To consider the influence of the construction errors on the internal force responses of the bridge structure,an initial finite element model of the bridge with the construction error is firstly built.And then,the static and dynamic testing scheme of the bridge is designed based on the constructed finite element model.By performing the loading tests of the bridge,the static responses of the bridge under the control loads and the dynamic responses of the bridge subjected to ambient excitations are recoded,respectively.2.Based on the measured data of the bridge and the finite element analysis results,three indices,including the deflection verification coefficient,the modal verification coefficient and the deflection reserved coefficient,are applied to preliminarily evaluate the load-carrying capacity of bridge structure.The measured modified values of the deflection obtained by using the deflection verification coefficient and modal verification coefficient are all less than the theoretical deflection limit,and the deflection surplus coefficient is good.The results show that the load-carrying capacity of the bridge meets the requirements of the design and the safety reserve is enough.3.Due to the effects of some uncertainty factors,i.e.measurement noise and environmental factors,a Bayesian based finite element model updating approach is developed by using the measured static and dynamic measurements.Combined with the advantages of Bayesian inference in stochastic finite element model updating,the proposed method is conducted to calibrate the static and dynamic performance of the bridge structure based on the measured static data and modal analysis results.4.Based on the updated bridge model,the load carrying capacity of the siganicant comoponents of the cable-stayed bridge is further evaluated.The rating factors of the tower,the cables and the girder of the bridge in service and ultimate limit states are calculated,and the results demonsatrate that the calcauletd rating factors for the brigde structures are all higer than 1.0,indicating the load carrying capacity of the brigde satisfy the design requirements.