Study On Damage Identification Of Girder Bridge Based On Multi-Point Fast Static Acquisition Of Special Test Vehicle

As the most important point in transportation infrastructure,bridge plays a pivotal role in promoting personnel exchanges and economic development.With the development of China’s economy,the number of new bridges is increasing with each passing day.At the same time,there are significant bridges in service.A series of factors,such as bridge overload,material degradation,vehicle impact accident and so on,have a negative influence on the bridge,which makes the health of the bridge during operation not guaranteed.Once the accident occurs due to the failure of the bridge,the life and property losses caused by it are often huge.Therefore,the bridge health monitoring is particularly important and urgent.The traditional bridge health monitoring method is difficult to be popularized and applied in a large number of small and medium-span bridges due to its high cost,complicated operation and non-transferability.In order to ensure the safety of the bridge,the indirect measurement method of the bridge with the characteristics of economy,efficiency and convenience has attracted people’s attention.This method only needs to arrange a small number of sensors on the test vehicle,and it can evaluate the health of the bridge through passing on it.Based on the traditional indirect measurement method,the operation mode of vehicles on the bridge has been adjusted in the thesis.Based on the concept that vehicles stop at different positions on the bridge and cause the parameters of the vehicle-bridge system to change,a new damage identification method of bfidge is proposed.The main work of this method is studied from three aspects of theoretical derivation,numerical simulation and field test.The results achieved are as follows:(1)In theory,the relationship between the frequency of vehicle-bridge system and the modal value of the bridge is deduced when a single test vehicle stops at different positions on the bridge.Considering the actual frequency measurement situation,the number of test vehicles is increased to more than one,and the relationship between the frequency characteristics of the multiple test vehicles bridge system and the modal shape of the bridge is derived,which lays the foundation for the practical application.(2)The theoretical derivation is verified by numerical simulation.Based on the traditional vehicle-bridge interaction(VBI)element,the element characteristic matrix of the vehicle-bridge coupling element that test vehicle parked on the bridge is derived.Based on this,a Finite Element(FE)model suitable for this method is constructed.By solving the characteristic equation of the model,the vehicle-bridge system frequency is obtained to construct the bridge modal shape.The single and multiple test vehicles are parked at different positions on the simply-supported beam bridge to construct the first third-order mode shape of the bridge,and the theoretical derivation is preliminarily verified.The relevant parameters of the test vehicle and bridge are studied to search the appropriate vehicle and bridge parameters.Numerical examples show that the method is also applicable when the simply supported beam support constraint changes to fixed support and the number of bridge spans increases.It is indicated that for different types of girder bridges,whether single damage or multiple damage,the location and severity of damage can be identified by the method proposed in this thesis.(3)The field test is conducted to verify the proposed method.A single-axle test vehicle is desined for this new damage identification method,and the feasibility of this method is verified by the real bridge filed test.