Study of Incremental Launching Schemes for Closure of Beipanjiang River Bridge

The main bridge of the Beipanjiang River Bridge is a prestressed concrete open-web continuous rigid-frame bridge with two separated bridge structures and with span arrangement of(82.5+220+290+220+82.5) m.Due to the long span of the bridge,the horizontal displacement at the top of the main piers and the subsidiary side piers might be great in the service period under the action of partial shrinkage and creep of concrete and the closure temperature,which is unfavorable to the load bearing behavior of the bridge pier structure,thus,it is necessary to carry out the horizontal incremental launching construction before the closure of the central span and the subsidiary side spans.Moreover,due to the existence of lateral bracing connection at the inclined legs of the main pier between the two separated bridge structures,the incremental launching construction of the two bridge structures would disturb each other,which is quite different from that of the conventional two independent bridges.In order to ensure that the load bearing condition of each pier could be improved in the incremental launching construction,the pier top displacement in the finished bridge state was analyzed following the principle of getting rid of pier top displacement to determine the rational incremental launching amount and launching force.The torsion twist of the main piers,elevation at the closure gaps and the incremental launching amount in the scheme of independent closure incremental launching for each of the two separated bridge structures and the scheme of parallel closure incremental launching for the two separated bridge structures were contrastively analyzed,and the scheme of parallel closure incremental launching for the two separated bridge structures was considered to be more rational.