【作者】 王妮；

【导师】 燕柳斌； 陈宗平；

【作者基本信息】 广西大学 ， 结构工程， 2014， 博士

【摘要】 型钢混凝土异形柱结合了钢与混凝土的优点,同时将型钢混凝土矩形柱与钢筋混凝土异形柱的优点发挥到极致,已得到越来越广泛的应用。在结构体系中,节点不仅是传力的枢纽,还是受力的重要部位,对框架结构的重要性不言而喻。实际的地震作用方向是与建筑轴线呈任意角度,而L形柱因其不对称的截面特性使得型钢混凝土L形柱空间角节点的受力更加复杂,因此研究空间角节点更加合理的加载方式、抗震性能、破坏机理和剪扭承载力很有必要。在课题组已有研究的基础上,本文对型钢混凝土L形柱空间角节点进行了较为系统的研究。本文采用课题组设计的空间加载装置对12个型钢混凝土L形柱空间角节点进行低周反复加载试验,考虑了柱截面配钢形式、加载角度、轴压比和梁的形式4个变化参数。获取其破坏机理、荷载-位移滞回曲线及骨架曲线、荷载-应变滞回曲线、节点核心区剪切变形、梁截面平均曲率和特征点参数,并分析了不同变化参数对其峰值荷载、位移延性、极限侧移角、强度退化、刚度退化、耗能能力和累积损伤等抗震性能的影响。试验研究结果揭示了型钢混凝土L形柱空间角节点的破坏机理,即弱核心试件破坏形态是以节点核心区剪切斜压破坏为主,弯曲扭转伴随粘结破坏为辅,强柱弱梁试件发生的是梁端弯曲破坏。滞回曲线饱满,位移延性、耗能能力和抗倒塌能力较好,强度、刚度衰减缓慢,具有较好的抗震能力。实腹配钢试件的峰值荷载最高,配T型钢桁架的试件的延性、抗倒塌能力、耗能能力最好,配槽钢桁架试件各级位移下的的累积损伤程度最大。随着加载角度的降低试件的峰值荷载逐渐降低,延性略有增加,00加载试件较45°加载试件峰值荷载降低了约25%,并且各级位移下累积损伤程度最高增加30%,刚度退化速度0°加载试件最快,30°加载试件最缓慢。在一定范围内随着轴压比的增加,耗能能力更好,试件延性和抗倒塌能力变差,试件的刚度退化更加明显。梁形式为型钢混凝土梁的试件较梁形式为钢梁的试件峰值荷载提高38%,并且累积损伤有较大程度的缓解,延性、抗倒塌能力均较好,梁形式为钢筋混凝土梁的试件的刚度退化较带钢梁更加明显。采用有限元软件Abaqus对既有试验试件LJ-1-LJ-9进行有限元分析,破坏形态与试验相似,计算的滞回曲线较试验的更加饱满、对称,初始刚度和峰值荷载较试验值偏大,峰值荷载计算值与试验值的误差基本在10%以内,满足一般的精度。在此基础上设计各种工况下的足尺试件74个,并对其进行滞回特性有限元分析,考虑了柱截面配钢形式、轴压比、加载角度、混凝土强度等级、肢高厚比、配钢率、不等肢、梁线刚度、柱剪跨比9个变化参数,分析了各变化参数对型钢混凝土空间角节点峰值荷载、耗能和延性影响,与试验结果大致相符。综合试验与有限元结果得出主要结论并给出建议：1)工程设计中建议优先选用实腹配钢形式,因其较空腹配钢的峰值荷载提高10%以上,综合抗震性能最好；2)三种配钢形式的试件的位移延性随轴压比增加而下降,特别是配T型钢桁架试件下降最快,建议轴压比限值设计值为0.5；3)加载角度与峰值荷载的关系反映在极坐标轴内关于45°角和135°角对称,加载角在45°以内,随着加载角度的增加峰值荷载增加,加载角度为45°的试件的极限承载力较平面节点提高了约30%。0°是结构的最不利加载方向。试件的耗能和延性随着加载角度的增加逐渐降低,与平面节点相比,加载角度为45°的试件延性系数降低约10%,双向加载对结构的延性有一定的不利影响；4)混凝土强度等级的提高会降低试件延性,建议最优混凝土强度等级为C40；5)提高肢高厚比和柱截面配钢率均可提高试件峰值荷载和耗能能力,但延性变差。建议最优肢高厚比为3.0,最优柱截面配钢率为4%～6%；6)两肢高度比的增加会提高试件的峰值荷载和耗能能力,最大幅度高达16.2%,即使试件延性变差但仍大于3,若工程实际需要,长肢的高度最大可取960mm;7)梁线刚度的增加可以有效提高试件的峰值荷载和延性,与梁柱线刚度比为0.1的试件相比,梁柱线刚度比为0.45的试件峰值荷载增幅可达2倍以上,延性系数增加68%,建议梁柱线刚度比为0.4～0.5；8)柱剪跨比的增加会大幅降低试件的峰值荷载,也会降低试件耗能,剪跨比介于2.0～3.5,延性较好,建议剪跨比为2.0～3.5,对应的建筑层高可取2.80m～5.00m。在分析试验研究结果及对有限元数据的拟合和回归的基础上,提出了型钢混凝土L形柱空间角节点的极限抗剪承载力计算公式,该公式在已有的研究成果基础上引入了加载角度、抗扭降低系数、轴压比和梁高与柱高之比,其计算结果较符合试验结果,该公式具有一定的参考价值。更多还原

【Abstract】 SRC special-shaped column is combining with the advantages of steel and concrete, which reaches maximum advantage on SRC rectangular column and RC special-shaped columns, and it has been widely used. Joint is a hub to transfer force and an important forced location in the structure system, and it is very important to frame structure. The direction of the actual earthquake is arbitrary, and has a certain angle with the building axes. Force condition of SRC L-shaped column space corner joint is much more complicated because of asymmetry of L-shaped column. Therefore, it is necessary to research reasonable loading way, seismic performance, failure mechanism and the shear bearing capacity of space corner joint. On the basis of existing research, SRC L-shaped column space corner joint is systematically studied in this paper.12SRC L-shaped column space corner joint specimens are designed to carrying out the low cyclic loading test by self-designed loading device, and four vary parameters are considered, which are column section steel form, load angle, axial compression ratio and beam form. Failure patterns, load-displacement hysteretic curves and skeleton curves, load-strain hysteretic curve, the shear deformation at joint core area, mean curvature of beam cross-section and feature point parameters are obtained. The influences of vary parameters to seismic performance indicators are analyzed, which are peak load, displacement ductility, ultimate lateral angle, strength and stiffness degradation, energy dissipation capacity and accumulated damage. Test results indicate failure mechanism of SRC L-shaped column space corner joint presents shear-diagonal compression mainly, and bend torsion with bonding secondarily at joint core area for weak core specimen, and bending failure of beam end for strong column weak beam specimens. Hysteretic curve is full, displacement ductility, energy dissipation and the ability to resist collapse are better, strength and stiffness attenuation are slower, and comprehensive seismic performance is better. The peak load of solid web steel specimen is the highest, the ductility, collapse resistance and energy dissipation capacity of the specimens with T-shaped steel truss is the best, with the load angle decreases, peak load of the specimens reduces gradually, ductility increases slightly. Compared with45°load angle specimen, the peak load of0°load angle specimen is reduced by25%, and cumulative damage of0°load angle specimen at all levels displacement increases extremely30%. Stiffness degradation of0°load angle specimen is the fastest, that of30°load angle specimen is most slowly. Increasing axial compression ratio can improve energy dissipation capacity of specimens within a certain range, but its ductility and collapse resistance capacity becomes worse, and stifness degradation of the specimens more clearly. Compared with specimen with RC beam, the peak load of specimen with SRC beam increases38%, and cumulative damage has a larger degree of ease. Ductility and collapse resistance are all better. Stiffness degradation of specimens with RC beam are more obvious than that of specimens with steel beam.Specimens LJ-1～LJ-9are analyzed by finite element software Abaqus. Failure patterns are similar to the test, and the calculated hysteretic curves are more full and symmetrical than measured curves. The initial stiffness and the peak load is larger than test value, and the errors are within10%, which basically meets the general accuracy.74full scale specimens are designed, and the hysteretic characteristics is analyzed. Column section steel form, axial compression ratio, loading angle, concrete strength grade, limb high thickness ratio, steel ratio, ranging from limb, beam line stiffness and shear span ratio are considered as variable parameters, and the influence of variable parameters on the peak load of SRC space corner joint, energy dissipation and ductility are analyzed, which have good agreement with the test results. Base on the experimental results and finite element results, the main conclusions and recommendations from this paper are shown below:1) Compared with open spandrel steel specimens, the peak load of solid web steel specimens can increase by more than10%, comprehensive seismic performance is the best, so the solid web steel form should be the first choice in engineering practical design.2) The increase of the axial compression ratio decreases the displacement ductility of three kinds of steel forms specimens, especially the T-shape steel truss joint specimens with high axial compression ratio finds the most rapid. So for SRC L-shaped column space corner joint, the limit value of axial compression ratio is suggested to be0.5.3) The relationship of load angle and the peak load is reflected in axis symmetry of polar coordinate about45°. Within45°load angle, the peak load increases with the increase of load angle, the peak load of specimens under45°load angle is higher about30%than that of plane joint, and0°load angle is the most unfavorable loading direction. As the load angle increase, the energy dissipation and ductility of specimens reduce gradually. Compared with the plane node, the ductility of specimens under loading angle of45°reduces about10%, and bi-directional loading is likely caused a certain adverse effect on the ductility of the structure.4) The increase of concrete strength grade can reduce its ductility, so the optimal concrete strength grade is suggested to be C40.5) The increase of the limb high thickness ratio and column section steel ratio can increase the peak load and energy dissipation capacity of specimens, but leads to poor ductility, so the optimal limb thickness ratio is suggested to be3.0, and the optimal column section steel ratio is suggested to be4%～6%.6) The increase of two limb height ratio would increase the peak load and energy dissipation capacity of the specimen, the biggest up to16.2%. Even if ductility of specimens decrease, it is still more than3. For the actual needs of project, the commendable maximum height of the long limbs is960mm.7) The increase of beam linear stiffness can effectively increase the the peak load and ductility of the specimens. Compared with specimens which the beam column line stiffness ratio is0.10, the growth of the peak load of specimens which the beam column line stiffness ratio is0.45can reach more than2times and ductility increases68%, and the suggested linear stiffness is0.4-0.5.8) The increase of the column shear span ratio will greatly reduce the peak load of specimens; it also decreases the energy dissipation. When shear span ratio is between2.0-3.5, the ductility of the specimens is better, and the suggested shear span ratio is2.0～3.5, and the corresponding storey height is preferable2.80m-5.00m.Based on experimental research and finite element data fitting and regression. The shear capacity calculation formula of SRC L-shaped column space corner joint is proposed, and load angle, tensional reduce coefficient, axial compression ratio and the height ratio of beam to column are introduced in this formula. Verified by experimental result, the calculated results are proper.更多还原