| The external force size and form of the engineering structure system determine the sectional design of each component in the system.However,due to long design lifetime in major engineering structures,such as large-span bridge,etc.,they will meet with adverse factors,including extreme climate conditions,sudden natural disasters,corrosion of special environment,and impact of vehicle ships.These adverse factors are easy to result in local damage of the bridge system within the service lifetime,resulting in reduction of the bridges’ carrying capacity.If influences of local failure on the structure system are not considered in the design stage,some local failure will result in continuous structure collapse.As a result,it is very necessary to use the redundancy theory to evaluate the carrying capacity of bridge after local failure.Main research contents and results are stated as follows:(1)Basic principles of redundancy,application in structure design and its application status are elaborated;(2)The basic concept of redundancy in the civil engineering is narrated.Component redundancy and structure redundancy are respectively studied.Besides,several indexes of evaluating redundancy are respectively enumerated.(3)The anti-shock redundancy of a six-floor frame model is analyzed.The research results indicate that the three layers under the bottom are the weak parts in the frame structure.Two optimization schemes of enlarging three-layer column and girder cross-section area and reinforcing three-layer column and girder material strength under the bottom are compared,finding that the second optimization method is more efficient.(4)Redundancy index based on the strain energy is constructed.The components with initial damage in the concise truss bridge model are analyzed.Continuous collapse analysis is used to find out the key components and failure paths in the truss bridge system.When initial damage of some components is unavoidable,reinforcing a component in the failure path is used to stop optimization of continuous collapse.(5)By analyzing the limit bearing redundancy and local failure redundancy of the bridge structure model are conducted.Carrying capacity of bridge structure in the overload model and local failure is evaluated.According to analysis results,the increase of limit carrying redundancy and local failure redundancy can meet the requirements for the bridge model of key components. |
