Study On Mechanical Behavior Of Reinforced Concrete Beams Under Fatigue Load

As an anchoring technology,planting technology has been widely used in the reconstruction,reinforcement and expansion of building structure.At present,the research on the anchorage members is mainly based on the mechanical properties of drawing and bearing static load,whereas,there is not much research on the performance of anchorage members under complex stress state.In the study of the fatigue behavior of anchored beams,the authors found that the residual strain of anchorage bars is greater than the residual strain of pre-reinforced and the creep characteristics of anchorage glue and adhesive interface is proposed,but the study on creep is still blank.With the wide application of planting bar technology in concrete beams,it is very important to study the mechanical properties and creep properties of the tendons under the fatigue properties.This paper analyzes the fatigue behavior of five reinforced concrete beams,as well as,the creep characteristics of deflection,reinforcement strain,concrete strain,crack,bearing capacity and bonding interface.The results show that the increase of the depth of anchorage can extand the ultimate bearing capacity.With the increase of the depth of anchorage,when the depth of planting bar increased from 20,d to 25,d(d for the diameter of embedded steel bars),the bearing capacity increased by 22.3%.if the depth of planting bar increased to 30 d,bearing capacity increased by only 3.9%.With the increase of the depth of planting bar,the failure form of the beam transits from the concrete peeling on the bottom to the concrete being crushed on the top.The creep decreases with the increase of the depth of embedded bar,which indicates that increasing the depth of embedded bar can reduce the creep damage of beam.The damage of beams is mainly concentrated in the first 500,000 cycles,while,the influence of frequency on the beam is very small after 500,000 times.The lower the frequency,the greater the residual creep of the beam and the greater the creep damage;fatigue loading has a bad effect on the compressive zone concrete.The rapid increase of the deflection of 100,000 times before fatigue loading is mainly the development of creep damage,after 500,000 times,.the creep change is stable,and there is a downward trend the increase of the deflection is the result of fatigue damage accumulation.