Design and Key Construction Techniques of Movable Shuttering System of “One Shuttering for Concreting of Twin Girders”

To resolve the problem of in-situ concreting of the twin box girders of Dongguan Waterway Bridge that were laid out in parallel and had a close and variable spacing distance,it was proposed that the girders should be concreted by the movable shuttering system(MSS) of shuttering for concreting of twin girder.The MSS was designed as an one of deck traveling type and two sets of the formwork systems(the spacing distance between the systems could be freely adjusted in a given range) for concreting of the girders were circled by the suspension beams of the MSS.The MSS was mainly made up of the main beam,front launching nose,upper cross beams,suspension beam systems,supporting legs,formwork systems,traveling system and hydraulic system.The model of the MSS was established by the software ANSYS and the load cases of the concreting and traveling of the MSS were calculated and analyzed.The results of the calculation and analysis proved that various safety indices of the structure of the MSS could satisfy the relevant requirements in the codes.In the construction,the key construction techniques of handling behind the abutment back,pre-loading of the MSS,setting of the pre-cambering,adjusting of the spacing distance,balanced concreting of the girders,concurrent tensioning of the prestressing tendons and traveling of the MSS were applied and finally the concreting of the twin girders,using one set of the MSS,was smoothly implemented.