Experimental Study On The Flexural Behavior Of Reinforced Concrete Beams With Bundled Steel Bars

In long span and heavy load structures, it is difficult to position steel bars and to cast concrete at the locations where there are intensive reinforcement bars. An effective way to handle this problem is to use bundled bars, namely, to bundle two or three deformed bars abreast. Based on the experimental research of the anchoring property of members with bundled bars, and referring to the codes in foreign countries, the flexural behavior of reinforced concrete beams with bundled bars is studied and the design method is given out. Results of the study can be applied for design reference and code emendation. The main researches are as follows:First, experiments on the flexural behavior of concrete beams with bundled bars are carried out. Test and analysis results show that the displacement and the cracks of the members with bundled bars are basically the same as normal members. The slight decrease of the bearing capacity of bundled-bars beams caused by the effect of shear reinforcement bars at diagonal cracks can be negligible.Secondly, the force transfer property of lapped bundled bar splices is studied. Test and analysis results show that the beam with lapped bundled bar splices has similar bearing capacity, rigidity and cracking characteristics to normal beams. The splices can be disposed at different locations so that the intensive cracks resulting from thick bars are avoided.Thirdly, the method for calculating bearing capacity of beams with bundled bars and checking their property during service period is worked out according to the equivalent area principle. And the detailing measures for disposing the lapped bundled bar splices are also proposed.