Study On The Performance Of Circular Concrete Columns Confined With Lateral Pre-tensioned FRP Under Axial Pressure

How to reinforce the damaged concrete columns in the existing structures has become one of the main problems in the reinforcement technology. The lateral pre-tensioning FRP can provide active restraint for the core concrete, so the high strength of the FRP can be put into great play. The stress hysteresis can also be avoided, which can make a better reinforcement effect. However, at present the research of columns reinforced by lateral pre-tensioning FRP at home and abroad is still at the exploratory stage. The behavior of the concrete columns reinforced by the lateral pre-tensioned FRP under axial pressure can not be understood fully, and also there is no design code which is available at this time. Based this status, the main research of the paper are as follows:(1) In this paper, experiments on 25 circular concrete columns confined by pre-tensioned FRP under axial pressure are conducted. In the experiment, lateral pretension is exerted by high-strength fiber material self-locking anchor. The effecting factors of the constraints such as the size of pretension, concrete strength, FRP type, section size, intial damage and surface treatment are studied, and the break progress and break modalities of specimens with different parameters are observed.(2) The working mechanism of lateral pretension FRP confined concrete columns was analyzed, and the exiting strength computational model and strain computational model of concrete columns confined with FRP was introduced. It must cause large error if adopt the computational model of non-pretension FRP. In this paper, the initial constraints stress and effective constraints stress were introduced, and the strength computational model,strain computational model and the stress-strain model of circular concrete columns confined with pretension FRP was advanced. Good agreement between theoretical and test results is achieved.(3) The simulation of the experiment was made by using the finite element software-ABAQUS. The modeling process using the ABAQUS was introduced in detail. By studying results of the simulation, the mechanical characteristic of circular concrete columns confined by lateral pre-tensioned FRP under axial pressure is analyzed. The differences among columns without reinforcement, columns confined with non-pre-tensioned FRP and columns confined with pre-tensioned FRP were compared. Through the simulation, the ultimate strength, ultimate strain and the stress-strain curve of the specimens were got, which achieved good agreement with test results, and then reason of the deviation was analyzed.