| With the rapid development of infrastructure construction,reinforced concrete structure as one of the basic structures was widely applied to bridges,ports and swage treatment plants.Reinforcement corrosion especially in the humid environment causes decrease of the service life and durability of concrete structure.CFRP tendons possess many advantages over steel bars such as high tensile strength,high corrosion resistance and fatigue property.It’s superior material properties make it be an ideal alternative of steel bars.However,in the recent decades,there were a growing number of collision accidents happened to ship and heavy vehicle.These accidents always lead to degradation of structure reliability,service life,safety and seismic capacity,even result in structure collapse and disastrous consequence.Consequently,engineers must take the impact load into account and take effective measures if construction projects widely adopt CFRP bars reinforced concrete.Furthermore,the impact damage and residual bearing capacity can be evaluated scientifically after the accidents.From the microscopic point of view,the key factor that determines the cooperative performance of CFRP bars and concrete under impact load is the bond performance of the interface between CFRP bar and concrete.In the past 30 years,researchers have done plentiful work to study the factors affecting static bond performance and proposed some kinds of bond-slip model at home and abroad.However,the knowledge of the bond performance between FRP bars and concrete under impact load is still an unexplored area.What’s more,《Technical code for infrastructure application of FRP composites》(GB50608-2010)[54]also has not pointed out the dynamic bond performance of FRP bars.Therefore,this article on the bond performance of FRP bars and concrete has an important theoretical significance and practical value.The main contents of this study are summarized as follows:(1)The static CFRP bar pull-out tests were carried out to make an investigation on the influence factors of static bonding properties.The comparison of the corresponding bond-slip curves and the existing constitutive models under static load.Then the requirements of anchorage length in several codes were compared and made a further discussion.(2)The impact load turns into pull-out force by the experimental equipment to pull the FRP bars from the concrete cubes.The bond-slip curves at varying loading rate were obtained.The factors affecting the dynamic bond performance were discussed and compared through analyzing the experimental variables.And the design method of the FRP tendon structure which could bear the impact load is put forward.(3)Through comparing dynamic and static test results,the dynamic bond-slip model of FRP bar is presented based on the test data,the formula of average bond stress considering the strain rate is put forward.The formula of anchoring length of static FRP tendons in some codes is amended to make it have dynamic application value. |
