Experimental Study On Seismic Behavior Of The New Assembly Monolithic Columns

Compared with the traditional cast structure, the precast monolithic structure notonly has the advantage of high quality, environmental protection, labor saving, but alsoexcel at high efficiency, low cost, material savings etc. Usually, the joint region is theweak part of the precast monolithic structure. The key problem of the precast monolithicstructure is the quality of the connection, which can not only affect the seismicperformance of structure, but also restrict its development. Our research group proposeda new column-column connection form to the problem that the former precastmonolithic structure were poor in complicated connection, uncertain force transmission,inconvenient construction and other issues. The new connection area of the assembledcolumn adopt the bolt reinforcement acrossing the reserved hole in the concrete column,then wrapped the column with the steel plate hoop, and welded the bolt reinforcement tothe steel plate hoop eventually. According to the experiment that new fabricatedcolumns were tested lateral loading, studied the seismic response of precast monolithicstructure. And the capacity formula about the front section and inclined section were putforward based on the mechanical characteristics of the joint area. Established suitablerestoring force model of the new precast monolithic column in finally.We designed two assemble-monolithic columns with high-strength spiral hoopsand two cast-in-situ columns with high-strength spiral hoops, imposed under lowreversed cyclic loading and at the different axial compression ratio respectively. In this paper, we researched the seismic performance and failure process of theassemble-monolithic columns from a number of different standpoints such as hysteresiscurves, skeleton curves, rigidity degeneration, energy dissipation capacity, ductility, etc.The new assemble-monolithic columns proved to be good seismic performance underthe test. Thanks to the high strength of spiral stirrups which confined the core concreteeffectively, the assemble-monolithic columns remained large eccentric compressiondamage under such large axial compression ratio.Analyzed the stress-strain relations of the longitudinal bars, high-strength spiralhoops and steel plate hoop at connection area. The basic stress-strain relations ofreinforcements can reflect the stress state of the structure in microstructure and providethe grounds for establishing the reasonable calculation model. After the rationalsimplifications and assumptions of the calculation model at joint area, concluded thebending and shear bearing capacity formula at the connection region and checked thestrength of the contact surface.Established and analyzed the three-dimensional solid finite element model of theassemble-monolithic columns by applying ABAQUS finite element software. From thehysteresis curves and the stress nephogram of the simulain results, we could find outthat the simulain results were in good agreement with the test results so that the modelfor the nonlinear analysis was feasible and correct.According to the test results, theoretical skeleton curves meeting the newassemble-monolithic columns were established. Meanwhile, the yield load, yielddisplacement, peak point load, peak point displacement and degradation of thecorresponding stiffness parameters were confirmed. The established theory skeletoncurve coincided well with the experimental data.