| After years of seismic research and development,most of the anti-seismic designs have been able to prevent building structures from collapsing under strong earthquakes.However,the main components and non-main components of the structure are usually difficult to repair quickly under the earthquake,or the repair and reinforcement costs are high,resulting in the interruption of building functions.As a result,many buildings have to be demolished and rebuilt,causing innumerable waste of labor,material,time and other resources.Based on this,the academia puts forward the "building seismic resilience " or "post-earthquake functional recovery",in which one important index is the time needed to restore the original building function.As the first seismic defense line,the coupling beam is the most vulnerable under the earthquake,so the rapid replacement of the coupling beam becomes an important part of the building toughness design.Recent years,the concept of replaceable steel coupling beam has been proposed in the academia.And the beams are designed to include energy-dissipating replaceable sections in the middle and elastic non-replaceable sections on both sides.The damage of steel beams is concentrated in the replaceable sections under earthquake,so as to achieve efficient replaceable performance.In order to ensure the replaceable steel coupling beam has sufficient energy consumption before failure,the energy dissipation replacement section is usually designed as an I-beam section that can consume energy by shear yield.However,the excellent seismic performance of the replaceable coupling beam is usually accompanied by a large displacement of the replacement section,which often brings damage to the upper floor of the coupling beam,which affects the post-earthquake recoverability of the overall structure.The purpose of this paper is to minimize the damage of the floor slab on the premise that it has little impact on the initial stiffness and bearing capacity of the replaceable steel coupling beam specimen with floor slab.Therefore,three replaceable steel beam specimens with floor slabs were designed,including SCBS1 with unconnected ordinary concrete floor slabs;SCBS2 with ECC material used in the upper floor of the replacement section,and with cracks in the floor slabs at the joints between the replacement section and the non-replacement section;SCBS3 with variable section designed for the non-replaceable section of the steel beam.Pseudo static test and ABAQUS analysis are carried out on the above three specimens,and the following research conclusions are obtained:(1)The quasi-static test of each specimen was carried out,and the seismic performance indexes and damage of each part of the specimens were analyzed.The result shows that the three specimens all possess excellent seismic performance,and have similar seismic performance indexes.SCBS3 scheme has a great influence on the initial stiffness of the specimens.The distribution of floor cracks of SCBS1 and SCBS2 is basically the same,mainly distributed in the upper part of the end plate and the connection between the floor and the wall limb,but the ECC floor cracks in the middle of SCBS2 show the characteristics of many and dense;SCBS3 has the lowest number of cracks,and the cracks are concentrated in the connection between the floor and the wall limb;Both SCBS2 and SCBS3 have significantly reduced the crack width under seismic action(corner 0.02),and SCBS3 is easier to construct,while SCBS2 has better loss reduction effects under test limit displacement(corner 0.05).The damage of steel coupling beam was concentrated in the middle energy dissipation replacement section,and the specimens were finally damaged due to the fracture of end plate flange crack.(2)The finite element analysis of each replaceable steel coupling beam specimen with floor slab was modeled by ABAQUS.The load displacement curve of each specimen was well fitted to the actual skeleton curve.The Mises stress nephogram of the analysis model shows that when loading to the peak displacement,the replacement section of each specimen yields,while the non-replacement section is still in the elastic range,which verifies the rationality of the design of each specimen.Comparing the DAMAGET nephogram of each specimen with the floor crack in the test,it can be found that the two have a high degree of consistency,which verifies the reliability of the model once again.(3)Parameters analysis of each specimen by ABAQUS: after changing the connection mode between the steel coupling beam and the floor slab of SCBS1,it can be seen that the closer the connection between the two,the higher the initial stiffness and bearing capacity of the specimen,but at the same time,the damage to the floor is aggravated;the change of stiffness ratio caused by changing the web thickness of the non-replacement section has little effect on the stiffness and bearing capacity of the specimen,and the performance of the replaceable steel coupling beam mainly depends on the middle replacement section;the change in stiffness ratio caused by the thickness of web in the replacement section can effectively affect the stiffness and bearing capacity of the specimen,and the stiffness ratio of steel coupling beam should be in the range of 0.29 ～ 0.51;with the increase of the length ratio,the stiffness and bearing capacity of the specimen gradually decrease,but the reduction is getting smaller,and the length ratio should be between 0.42 and 0.98;changing the variable section position of the steel coupling beam in the non-replacement section of SCBS3 has little effect on the mechanical properties such as the bearing capacity of the specimen,and with the increase of the variable section position,the initial stiffness of the specimen increases,and the damage area of the floor slab shifts and increases. |
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