Study On The Key Issues In Mechanical Performance And Construction Monitoring Of Hybrid Girder Cable-stayed Bridge With Single Tower And Single Cable Plane

Hybrid girder cable-stayed bridge is a kind of cable-stayed bridge of which theside span and main span girder are respectively made of concrete and steel connectingand switching at the hybrid joint. The defferences between concrete and steelcomposing the girder in side span and main span and the complication of the structuraland mechanical characteristics of,key part of the bridge,the hybrid joint bring newproblems and challenges to the designing and construction monitoring of which it is avital task to study the key issues,of the hybrid cable-stayed bridge.Most of the hybrid girder cable-stayed bridges,in construction or established,aredesigned into half floating system with double cable plane at present and in theclassical form of the cantilever-construction of the steel box girder that consists themain span of the bridge the length of the steel box girder segment is often equal to thecable spacing assembled as a whole while the bridge studied in this paper is designedinto rigid system consolidating the girder,tower and pier together with single cableplane and the segment of steel box girder is to be separated into two parts hoisted andassembed succesively during the cantilever-construction and thesecharacterastics,including large span,single tower,single cable plane and wide boxgirder,leave torsion to the hybrid joint and make construction monitoring moredifficult.Based on the Nujiang bridge project in Liuku,Yunnan province and latest researchachievement,key issues of construction monitoring of the hybrid cable-stayed bridgeare studied in this paper of which the main contents are listed as follows:1. The MIDAS F.E.M model of the bridge is established to study the mechanicalproperties of the bridge.2. Based on the project in reality the method of optimizing the constructionprocess is studied and the best process is proposed.3. The method of construction monitoring of the cantilever-construction of thesteel box girder is studied of which the key parameters are explained.4.ANSYS F.E.M model of the hybrid joint is made to analyze the mechanicalbehavior of the hybrid joint.And the conclusion is drawn as follows:1. It is better to take rigid system for the hybrid girder cable-stayed bridge with single tower and single cable plane.2. It is better to simplize the hybrid joint for such kind of bridge.3.The cantilever-construction of the main span steel girder can be optimizedthrough the method proposed in this paper.4.The construction process should be monitored by the unstressed cable length,manufacturing and installation line of the girder.5.The hybrid joint shows a good mechanical property under the torsion load wherethe RPC takes the70~80%torsion and the steel takes the rest20~30%.6.The special warping cross-section stress is caused by the torsion in the hybridjoint,leaving30%increase of the cross-section stress in RPC and steel.