Experimental Study On The Fatigue Behavior Of Strand At Anchorage Zone Of Prestressed Concrete Beams With Pretensioned Bend-up Tendons

Prestressed concrete beams with pretensioned bend-up tendons are new presressed beams which have come into practice in recent years.In comparison with straight-line pretensioned method and post-tensioning method,this new beams are more suitable for large span structures,what’s more,grouting process and corrosion pretensioned reinforcements can be avoided,thus the durability of the stucture will be improved.There will be much more benefits to economy and society.The pre-pressure of prestressed concrete beams is established by bond stress though concrete and steel,but the steel strand at anchorage zone of beams may cause stress concentration and the stress state is complex,too.In order to study the fatigue performance of steel strand at anchorage zone of fold-line pretensioned beams,this article based on the actual condition of the bridge engineering,conducting fatigue test for four beam specimens.The main research work of this thesis is shown as following:1.Based on the research results at home and abroad,four prestressed concrete beams with pretensioned bend-up tendons have be designed and produced.The major change parameter is concrete strength,stretching control stress and prestress transfer length of strand.2.Choosing reasonable fatigue loading system and the fatigue load,and then conduct the fatigue test at 2.5 billion times fatigue loading.After this,take the static loading test at last.The results show that after 2.5 billion times fatigue loading,three beams have not suffer anchoring destruction,and the steel strand isn’t break,either.Because of the Fatigue stress amplitude is too large,the strand in last one beam(FA-2a)have break at 1.48 billion times fatigue loading.After the static loading test,the strand of three beams have not break,this shows the ductility of steel strand is well at anchorage zone.3.The bond-slip relation,residual sliding of strand at anchorage zone and the bond strength,the cracks of concrete have been analyzed in detail.The results show that the fatigue performance of strand at anchorage zone of prestressed concrete beams with pre-tensioned bend-up tendons is stable.4.Then analyze the anchoring fatigue bearing capacity and prestress transfer length of strand according to Code for design of reinforced concrete and prestressed concrete highway bridges and culverts,which verify the applicability in prestressed concrete beams with pretensioned bend-up tendons.