【作者】 齐岳；

【导师】 郑文忠；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2010， 博士

【摘要】 与普通混凝土相比,高强混凝土微观结构密实,高温下易发生爆裂,这使得高强混凝土柱的抗火性能相对较差。另外,随着混凝土强度的提高,混凝土单轴受压应力—应变曲线的上升段、下降段变陡,表现出强度越高脆性越显著的特性,这使得高强混凝土柱的抗震性能相对较差。为改善高强混凝土柱的抗火性能和抗震性能,同时保证柱具有较高的承载力,本文提出了核心高强混凝土柱这一新型构件。核心高强混凝土柱是指在横截面内以高强混凝土为核心,在核心区外围设置普通钢筋混凝土的柱,此类柱已获国家发明专利。核心高强混凝土柱从概念上讲应具有相对较高的承载力和相对较好的抗火性能及抗震性能。一定厚度的外围普通混凝土可减缓高强混凝土爆裂的发生,从而改善柱的抗火性能。外围普通混凝土与核心高强混凝土相比,受压应力—应变曲线下降段平缓,从概念上讲可使得核心高强混凝土柱的抗震性能相对较好。为探索核心高强混凝土柱的受力性能与设计方法,本文开展了以下几方面的研究工作：(1)针对核心高强混凝土柱横截面内两种混凝土的峰值压应变不同,轴压荷载作用下,核心高强混凝土柱何时达到轴压承载力及如何计算轴压承载力的问题,进行了16根核心高强素混凝土短柱、3根配筋核心高强混凝土短柱及1根普通钢筋混凝土短柱对比试件的轴心受压试验。试验结果表明：核心高强混凝土短柱轴力达最大值时,外围普通混凝土应力—应变曲线已进入下降段,核心高强混凝土尚未达到其峰值压应力。在计算核心高强混凝土柱轴心受压承载力时,考虑到核心高强混凝土和外围普通混凝土均未处于各自的峰值压应力状态,提出了核心高强混凝土抗力调整系数nc和外围普通混凝土抗力调整系数ne。基于试验结果和数值计算结果,拟合得到了抗力调整系数nc和ne的表达式,并提出了核心高强混凝土短柱轴心受压承载力计算公式。按照本文建议公式所得轴心受压承载力计算值与试件的抗力试验值吻合良好。(2)针对实际工程中大多为偏心受压柱这一情况,完成了12根以偏心距和核心高强混凝土面积为参数的核心高强混凝土短柱偏心受压试验,考察了试验柱的破坏情况、距柱端0.5倍柱高处截面在加载过程中应变的分布规律及侧向挠度沿柱高的分布规律。试验结果表明：偏压荷载下核心高强混凝土柱的破坏特征与普通钢筋混凝土柱相似,试件截面在偏压过程中满足平截面假定,侧向挠度曲线符合正弦半波曲线。在计算核心高强混凝土柱偏心受压承载力时,考虑到若采用与普通钢筋混凝土柱相同的以平截面假定为基础的计算理论,确定等效矩形应力图系数比较繁琐这一情况,采用了相对简便实用的强度叠加法。根据折算受压区高度所处的位置,分四种情况分别提出了核心高强混凝土短柱偏心受压承载力计算方法,结果表明：按照本文提出的偏心受压承载力计算方法所得结果与试验结果吻合良好。(3)完成了9根以轴压比和核心高强混凝土面积为参数的核心高强混凝土柱水平低周反复荷载试验,考察了试验柱的破坏过程,测得了荷载—位移滞回曲线,分析了试验柱的耗能性能、抗力衰减、刚度退化、骨架曲线及延性性能。试验结果表明：对于剪跨比为3,轴压比no=0.33～0.42的核心高强混凝土柱,在水平低周反复荷载作用下发生压弯破坏,滞回曲线饱满,无捏缩现象,位移延性系数均大于3,延性较好。采用matlab语言编制了核心高强混凝土柱压弯构件非线性全过程分析程序,该程序得到了试验结果的验证。在此基础上,探讨了轴压比、纵筋配筋率、核心混凝土强度、核心混凝土面积比、配箍特征值、外围混凝土强度及剪跨比对核心高强混凝土柱抗震性能的影响。结果表明：轴压比、核心混凝土面积比、剪跨比是影响核心高强混凝土柱抗震性能的三个主要因素；核心高强混凝土柱的抗震性能优于高强混凝土柱；适当选取核心混凝土面积比,可使核心高强混凝土柱的抗震性能与普通钢筋混凝土柱相近。基于112种工况下核心高强混凝土柱水平荷载—位移关系曲线的计算分析和数值回归,提出了以轴压比、核心混凝土面积比、剪跨比为变量的恢复力模型骨架曲线特征参数计算公式,建立了核心高强混凝土柱水平荷载—位移恢复力模型。按照建立的恢复力模型对试验柱进行了计算,所得计算曲线与实测的滞回曲线吻合良好,说明所建立的恢复力模型具有较高的精确性,能够较好地模拟和反映构件在水平地震作用下的抗震性能。(4)为保证核心高强混凝土柱发生延性较好的大偏心受压破坏,引入了界限轴压比的概念。界限轴压比是根据大、小偏压破坏界限所确定的轴压比,是提出各抗震等级框架柱轴压比限值的前提和基础。通过程序计算,分析了768种不同工况下核心高强混凝土柱大、小偏压破坏的界限点,得到了各工况下的界限轴压比,并提出了设计用界限轴压比。更多还原

【Abstract】 Compared with ordinary concrete,high strength concrete is dense in micro-structure and is prone to burst under high temperature.This makes the fire-resistance performance of high strength concrete columns relatively poor. In addition,as concrete strength increases,the concrete stress-strain curve under axial compression will turn steeper and concrete will be more brittle,therefore making a relatively poor seismic capacity for the high strength concrete columns.In order to improve the fire-resistance and seismic behavior of high strength concrete columns and to remain their high bearing capacity, a new concept of columns with high strength concrete core (HSCC columns) is proposed in this paper. HSCC columns are ordinary reinforced concrete columns with high strength concrete core,which has higher bearing capacity, finer fire-resistant performance and seismic behavior. This kind of columns has already been patented in the State Intellectual Property Office of China.A certain thickness ordinary concrete can slow down the bursting of high strength concrete and thus improve the fire-resistance performance of columns.Compared with high strength concrete,the stress-strain curve of ordinary concrete drops slower, which makes HSCC columns conceptually have better seismic behavior. This thesis presents a series work carried out to investigate the mechanical behavior of HSCC columns and to propound the corresponding design method, as shown in the following:(1)Due to the different concrete material property, the peak compressive strain in the core high strength concrete and that in the external ordinary concrete are different.In this context,16 plain HSCC columns,3 HSCC columns and 1 ordinary reinforced concrete column are tested to collapse to investigate the strain of the columns corresponding to the peak loading and how to calculate the axial compression bearing capacity. Test results indicate that when axial force of HSCC columns reach to the maximum value,external ordinary concrete stress-strain curve has turned into the drop part, while the core high strength concrete is still in the climbing part of the curve.Considering neither the core high strength concrete nor the external ordinary concrete is in the peak compressive stress state,the coefficient of nc and ne whose formula are regressed from tested and analysis results are introduce into the axial compression bearing capacity predicting equation to adjust the resisting force of core high strength concrete and external ordinary concrete.The results of the bearing capacity calculated by the formula brought up in this paper was in good agreement with the tested results.(2)Twelve HSCC columns which has different area of high strength concrete core are tested to failure under eccentric loading with different eccentricity to investigate the failure characteristic of these specimens,the strain distribution in the section of the half-height of columns,and the development of lateral deflections versus the height of column.Test results indicate that failure characteristic of HSCC columns is similar to the ordinary reinforced concrete columns under eccentric loading,the strain distribution along the cross-section is accordance to the plane section assumption,and the lateral deflection curve follows the sinusoidal half-wave curve.Due to the difficulty in giving the coefficient of equivalent rectangular stress block to calculate eccentrically compression bearing capacity of HSCC columns based on the plane section assumption,the relatively simple strength superposition mehod is adopted in this paper. According to the four different reduced height of compressive zone in the HSCC columns, the calculation method is provided to predict their bearing capacity under eccentric loading.It is shown that the predictive results obtained by this method match well with the experimental ones.(3)Nine low cyclic loading tests are conducted on HSCC columns with different axial compression ratio and area of high strength concrete core to investigate their failure procedures.The loading-displacement hysteretic curves are measured,and the behavior of energy dissipation,strength degradation,stiffness degradation,skeleton curves and ductility of these specimens are analyzed to evaluate the seismic behavior of HSCC columns.Test results show that when the shear-span ratio is 3 and the axial compression ratio no=0.33～0.42,HSCC columns would undergo compression-flexure failure under low cyclic loading,its hysteretic curve is plump and no pinch phenomenon occurs,excellent ductility is observed with the ductility coefficient greater than 3.A computer program is developed using Matlab to investigate the nonlinear behavior of HSCC columns subjected to the combination of axial compression and bending loads,which has been verified by the test results on the 9 HSCC columns mentioned above.Parametric analysis is then conducted to discuss the influences of axial compression ratio,longitudinal reinforcement ratio,core concrete strength,core concrete area ratio,lateral confinement eigenvalue,outer concrete strength and shear-span ratio on the seismic behavior of HSCC columns.The results indicate that the axial compression ratio, core concrete area ratio and shear-span ratio have significant effect on the seismic behavior of HSCC columns.The seismic behavior of HSCC columns is better than high strength concrete columns, and can be as good as ordinary columns by controlling the core concrete area ratio without losing much lateral bearing capacity. By analysing the load-displacement curves of 112 HSCC columns,the expression for characteristic parameters are given with 3 variables of axial compression ratio, core concrete area ratio and shear-span ratio to determine their skeleton curve.The restoring-force model for HSCC columns is further established.The numerical results based on the restoring-force model are in good agreement with the experimental results,which proves that the established restoring-force model performs well in simulating the seismic behavior of HSCC columns.(4)The concept of ultimate axial compression ratio is introduced to ensure the HSCC columns collapse in tension failure when subjected to axial compression and bending loads.The ultimate axial compression ratio is defined to specify the ultimate of tension failure and compression failure for columns subjected to axial compression and bending loads,which is the precondition to determine the limit value of axial compression ratio for the columns in the structures under different classes of seismic measure.With the computer program,768 HSCC columns are analyzed to determine the value of the ultimate axial compression ratio for the designing of this kind of columns.更多还原