Study On Application Of Diaphragm Wall Reinforced With GFRP Bars In Construction

The Glass-Fiber-Reinforced Polymer (GFRP) bar is a kind of material formed with resin and glass fiber compound.Because of the characteristics of GFRP, substituting GFRP bars for steel bars at the soft-eye openings for tunnel shield in diaphragm wall is technically and economically feasible. It allows the shield to cut diaphragm wall directly, consequently simplifies the construction process, speeds up the working progress, reduces risks, and saves the investment. By now, however, both domestic and international studies mainly focus on mechanical properties of concrete members of permenent structures reinforced with GFRP bars and are very poor and elementary on diaphragm wall reinforced with GFRP bars, especially on application in construction practice. In addition, because of lack of domestic and international engineering practice, there is no systematic construction method or process.Based on an engineering practice, a study is carried out on application of diaphragm wall reinforced with GFRP bars by means of theoretical analyses, laboratory tests and field measurements.Portative hoisting truss for GFRP diaphragm wall cage (ordinary steel cage) is devised and used in trial hoisting. A series of analyses is made based on the results of FEM calculations and field measurements. By compared with traditional bracing frame in mechanical properties, construction method and economical efficiency respects, the portative hoisting truss is proved having significant advantages in practice. Through the trial hoisting operation, the hoisting truss and the hoisting process are improved and optimized.The hoisting process of GFRP diaphragm wall cage using portative hoisting truss is studied by means of FEM analyses and field measurements. Some valuable conclusions are made by comparing the data. Several technical problems, such as the connections of GFRP bars, lengths of lifting loops and locations of lifting points, cooperation of cranes, are discussed. Laboratory flexural tests are carried out using concrete slabs reinforced with GFRP bars and steel bars. Concrete slabs with different GFRP reinforcement ratio are tested by FEM simulation. Based on tests results, the deformation process of specimens under load is described. Compares and analyses are made between cracking and ultimate load, deflection and strain of concrete of the two slab types. In addition, effect of GFRP reinforcement ratio to the rigidity of slab is discussed. Prediction equation of flexural rigidity is suggested. This equation is acceptable for concrete slabs reinforced with GFRP bars after cracking.FEM analyses are made towards the service behavior of diaphragm wall reinforced with GFRP bars during the whole process of excavation and construction of inner structures. By comparing the FEM results with the data of field measurements, the Contributory factors are studied. Some suggestions are made towards design and construction.