| During the seismic design of super high-rise building, C60high strength concrete ishighly used in columns to meet the demands of axial compression ratio and section size,while the beam-slabs that mainly subjected to bending load use C30instead.As a result,the huge differences of concrete strength grade between beams and columns occurred.Forensuring the continuity of columns, the concrete strength grade of joint core area isusually consistent with that of column. However, because of the long distance ofconcrete vertical transportation and poor concrete workability in the super high-risebuilding construction, concrete of joint core area is not easy to reach the qualityrequirements of column strength grade, causing reduction in concrete strength of jointcore area. If concrete of beams is used in joint core area(i.e. Sandwich Joints), then itmay not meet the design requirements of strong joints which is emphasized in theseismic design of high and super high-rise building in China. Therefore, to investigatethe impact of sandwich joints on super high-rise concrete structure has very importanttheoretical and practical value.The sandwich joints of a super high-rise concrete structure is selected for study. Andfinite element program ANSYS is adopted to make finite element numerical simulationof structure nonlinear.The main work and conclusions are as follows:(1)In order to reflect the true mechanical performance of the structure, and alsomake the result of calculation more realistic, when using ANSYS program, thethree-dimensional space separating finite element model of reinforced concrete sandwichjoint is used to make simulation.(2)Considering the plastic materials factors of reinforced concrete sandwich jointspecimens, the finite element analysis of material nonlinearity is used of model byANSYS program.(3)Considering the differences of force character in super high-rise and multistoried,high buildings, nonlinear finite element analysis of tensile bearing, compressive bearingand shear capacity are made on sandwich joints.(4)Establishing10specimens of sandwich and non-sandwich joints whose beamsand columns concrete strength grade differential are10MPa,15MPa,20MPa,25MPa and30MPa, to make stress analysis and comparative study of ultimate bearing capacity, and to find out the change rules of ultimate bearing capacity of specimens with differentgrade differentials.(5)According to the analysis and comparative study of ultimate bearing capacity ofsandwich and non-sandwich joint core area’s with different grade differentials, theconclusion is that when the grade differential is less than10MPa,sandwich joint core areaunder the constraints of beams and columns can satisfy tensile bearing, compressivebearing and shear capacity of non-sandwich joint core area.(6) According to the analysis and comparative study of ultimate bearing capacity ofsandwich and non-sandwich joint core areas with the same grade differentials, theconclusion is that the upper and lower columns with high concrete strength beyond jointcore area can effectively improve tensile bearing, compressive bearing and shear capacityof joint core area.(7) Establishing six joint specimens of different sandwich layer thicknesses, whosebeam and column concrete strength grade differential is30MPa, analyzing the impact ofdifferent sandwich layer thicknesses on the ultimate bearing capacity of joint core area,getting the conclusion that when increasing the thickness of sandwich layer,the ultimate tensile bearing, compressive bearing and shear capacity of joint core area arereduced. |
