Experimental Research On Merchanical Properties Of Concrete Beams With Adhesive Reinforcement Under Fatigue Load

As a kind of post-anchorage technology,planting technology solves the problem of new and old structure connection.It has the advantages of convenient construction,simple operation,short construction period and low cost.This paper mainly studies the eight test beams,whose depth of planting bar is 10 d = 500 mm,25d = 625 mm,30d = 750mm(d is the diameter of steel bar)and its test materials are the same.three beams have been carried out to analyze the effects of the reinforcement of the anchorage tip and the depth of planting bar on the mechanical properties of the rebar-planting beam by static load test.Then the upper and lower fatigue limits have been calculated according to the ultimate bearing capacity of the static load test,and the other five beams have been carried on fatigue test.The fatigue properties of the materials and members are analyzed under different frequency fatigue loading.The conclusions of this paper are as follows:(1)Under the action of static load,the ultimate bearing capacity of the tendons can be improved by the reinforcement of the anchorage tip that was added the stirrup and the increase of the depth of planting bar.However,the former can solve the stress concentration problem of the anchorage tip and ductility of beams well.(2)In the static load and fatigue test,the size of the crack load is not changed.The first crack is present at the interface of the old and new concrete,regardless of the depth of planting bar and loading frequency.(3)Under the action of fatigue load,the strain of planting bar,compressive strain of concrete,mid-span deflection and creep of anchorage rubber have accumulated damage.It reaches the maximum in the 10,000 times,100,000 times,100,000 times and 500,000 times of the fatigue cycle load.(4)High-frequency fatigue load has more influences than the low-frequency fatigue load on the fatigue damage of the rebar-planting beam,which reduces the ultimate bearing capacity and ductility of the rebar-planting beam.(5)Fatigue load reduces the mechanical properties of concrete and planting bar,and it shows the same mechanical properties as static load test in the latter.(6)The rebar-planting beam whose anchorage tip was installed stirrups and depth of the planting bar was 25 d has the best static load and the fatigue performance,in view of the ultimate bearing capacity or ductility performance.