Research On Seismic Behavior Of High Strength Reinforced Concrete Frame Columns In Large-scale Thermal Power Plants

In the main factory building structure of large-scale thermal power plants, due to its great height and large vertical loads (such as a furnished for arranging coal bucket between interstory, whose mass is too concentrating), anti-seismic problem is much outstanding. The characteristics of longitudinal and lateral frame columns are different from general frame columns, due to the high depth-to-width ratio of cross-sections and withstanding large vertical loads. The axial compressive ratio is a very important factor in columns design. Problems are often occurred: cross-section of frame columns depends upon the limit of axial compressive ratio, the constructional reinforcement ratio becomes the ratio of longitudinal reinforcing steel bar of frame columns, such problems are not reasonable. The use of high strength concrete in building constructions has many advantages, such as reducing sectional size of component evidently, alleviating the structure self weight and retrenchment the use of reinforcing steel bar, thus the economic benefit is distinct But the brittleness of high strength concrete causes anxious about its use in the earthquake-resistant structure. The intensity of concrete is higher, and the brittleness of concrete is bigger. Therefore, applying the high strength concrete in the main factory building structure frame columns of large-scale thermal power plants needs to research the valid measure that improves the and seismic deformation capability of high strength concrete frame column. The main contents are followed below:(1) For the aim of knowing the characteristics of main factory building structure frame columns of large-scale thermal power plants, nine high strength concrete frame columns with high axial compression ratio and six slender ordinary strength concrete frame columns with high axial compression ratio were tested under low reversed cyclic horizontal loading for the very first time, and thus the influencing factors of normal section bearing capacity, such as concrete intensity grade, axial compressive ratio, slendemess ratio, the type of stirrups and stirrup ratio, etc, the anti seismic deformation capability of frame columns were acquired. Based on the tests, the advised formula of normal section bearing capacity and inclined section bearing capacity of high strengthen concrete framecolumns are put forward, and the limit of axial compressive ratio and the minimum stirrup ratio in the encrypted region which meet ductility requirement to C60 concrete frame columns are given.(2) Based on the tests and theoretic derivation, skeleton curve of restoring force model of frame column with high axial compression ratio is got. It provides basic data and references to anti-seismic performance and dynamical calculation of high strength concrete monolithic structure.(3) Reinforced concrete frame columns modeled by using three-dimensional solid element to concrete and three-dimensional bar to reinforcing steel bar, and at the same time consideration the adhesive bond between reinforcing steel bar and concrete, the FEM is used. By choosing reasonable element, determining mesh division and load steps, simulation of load-displacement, cracking, yielding and ultimate load, crack development history, and calculating fail crack diagram of reinforcement concrete frame columns under laterally monotonic load are conducted. The analyses are compared with the experimental results. Based on finite element simulating tests of frame columns, load-displacement of frame columns without tests are simulated, and the influencing factors of frame columns are synthetically analyzed.(4) It was figured out that variational history of incremental dissipated hysteretic energy of high strength concrete tentative frame columns under different loading cycle levels; through analyzing all sorts of damage models comparatively, damage model of high strength concrete frame column are put forward, which offers good basement for further damage analysis.