Safety Assessment Technology Of Railway Cable-stayed Bridge Based On The Theory Of The Internal Force Envelope

Cable-stayed bridge has been rapidly developed from the 1990s because of its distinguished capacities of span,load,seismic performance,and its beautiful appearance.After entering the new century,urban traffic problem becomes increasingly serious,while rail transportation becomes one of the most effective ways to solve urban traffic problems because of its characteristics of large volume,speed,security,punctuality,environmental protection,energy and land conservation.With the construction and gradually improvement of a large network of rail transportation routes,cable-stayed bridge,as a rail carrier,provides greater convenience for people to travel.The uniqueness of the structure and load of rail cable-stayed bridge make it important to do health monitoring and safety assessment for the rail cable-stayed bridge.Under the guidance of the mentor and after nearly three years of effort,the author have studied the technology of rail cable-stayed bridge based on the theory of force envelope and have completed the related research work.The background and research status at home and abroad of the bridge health monitoring and safety evaluation is analyzed firstly in this paper.It could be concluded that bridge health monitoring and safety evaluation is researched by fuzzy comprehensive evaluation method,analytic hierarchy process(ahp)method,the reliability theory and defect status indicators evaluation method.Under the influence of popularity of urban rail way cable-stayed bridge and the uncertainty factors of bridge itself,application of urban rail cable-stayed bridge technology is not mature enough,and the present situation is still imperfect.And then put forward a kind of suitable for large bridge monitoring mode,namely the construction and operation period of the whole life of health monitoring model.The paper expounds the concept and advantage of life-cycle monitoring,and introduces the construction and operation phase of the life-cycle monitoring seamless connection mode of work,then as a theoretical basis for railway cable-stayed bridge during construction and operation periods of sensor layout analysis,determined the final layout.It's necessary to find a simple and feasible theory,the internal force envelope theory,and study the theory to clarify it can evaluate bridge safety status.The two essential elements of the theory,observed information and interval of the envelope,is difficult to obtain,this is also key point of research.Then the two elements is analyzed and discussed to determine the monitoring and assessment indicators for monitoring.The beam stress and deflection,displacement of tower,cable force are the main monitoring indicators.It researches the measured data and envelope interval by using monitoring indicators to find each envelope for the measured data and determine its obtaining technologies.At last,Caijia Jialing River bridge in Chongqing is used as an example to get measured data and calculate the envelope interval.Determine the safety of the bridge by using internal force envelope theory.The results show that the technology is safe,reliable and worth popularization and application.The preliminary conclusion in this paper,which researches safety assessment technology of railway cable-stayed bridge,provides the positive significance for the long-term health monitoring and safety assessment.