| The concrete slabs and steel girders of steel-concrete composite Bridges often have serious corrosion problems,especially the corrosion of steel bars,shear joints and steel girders caused by freeze-thaw cycle and chloride erosion in coastal areas.Therefore,it is necessary to replace the aged concrete slab to prolong the service life of composite Bridges.Compared with the traditional steel-concrete composite beams connected by welding bolts,the steel-concrete composite beams connected by bolts are easy to disassemble.However,due to the existence of machining and installation errors,the existing bolt joints will leave a gap in the hole through the steel beam,resulting in the reduction of initial stiffness.At the same time,the filling materials around the bolt joints often need to be poured on site,so the casting quality is difficult to control,the mechanical properties are affected by the post-pouring materials,and the joints cannot be partially replaced.In order to solve the above problems,this paper proposes four new types of detachable bolt connectors and studies their shear resistance and practicability.The main research contents are as follows:(1)Three kinds of detachable bolt connectors are put forward,,including bolt insert,cone nail sleeve and expansion bolt.a new type of single bolt test specimen and loading device are designed.Then,three sets of single bolt test specimen of new detachable bolt connectors and one set of welded bolt test specimen are carried out.The shear stiffness of new detachable bolt connectors is analyzed and compared with the traditional welding studs to verify its feasibility.(2)According to the results of single stud test,Tapered iron bolt connector(TIBC)was proposed.The push-out specimens with bolt diameters of 12mm and 16mm were designed and made,and the shear properties of TIBC were studied through the push-out test.At the same time,the push-out specimens of TIBC were subjected to brine corrosion for 6 months,and the corroded TIBC was replaced with the uncorroded TIBC and the push-out test was carried out to verify the detachability of TIBC under the influence of natural corrosion,and to evaluate the difference of TIBC's shear performance after corrosion replacement.(3)The shear resistance of TIBC is analyzed by finite element method with ABAQUS,and the results of finite element analysis is compared with the test results to verify the rationality of the finite element analysis.And from the bolt diameter and strength,concrete strength,TIBC component strength to evaluate its impact on TIBC shear performance,and put forward the TIBC bearing capacity formula.At the same time,the finite element model of TIBC and traditional welded stud composite beam is established to compare the difference between them in the flexural capacity of composite beam,and the reasonable arrangement of TIBC in composite beam is further discussed. |
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