钢管混凝土与钢管再生骨料混凝土抗冲击性能研究综述

介绍了钢管混凝土（CFST）和钢管再生骨料混凝土（RACFST）抗冲击性能的研究概况,总结了钢管混凝土在应变率、高温、约束系数、材料强度、冲击能量和外包约束等不同因素影响下冲击性能的相关研究成果,列举出目前对于钢管再生混凝土研究的不足之处。根据钢管混凝土抗冲击性能以及再生骨料混凝土相关特性,推测了钢管再生骨料混凝土的抗冲击性能。结果表明:钢管再生骨料混凝土具有良好抗冲击性能,相关结论为钢管再生骨料混凝土抗冲击性能的进一步研究提供了参考。     

配筋圆钢管再生混凝土短柱轴压试验研究

为探明再生粗骨料100%取代率下配筋对圆形钢管再生混凝土(RACFST)短柱受力性能的改善作用，进行了以不同纵筋配筋为参数的配筋RACFST(R-RACFST)的轴压试验。对比分析破坏模式、荷载-位移曲线、刚度、屈强比和组合效应等关键力学特性后发现：钢管与钢筋骨架的双重约束作用能有效改善核心再生混凝土的脆性，明显提升峰值荷载和塑性变形能力，有效减缓刚度退化；就屈强比与组合效应而言，并非配筋率越大越好，在一定配筋率范围内时，可使构件各部分组合效应更好，并能充分发挥钢筋的性能。由此得出结论：配置少量钢筋既可保证构件在再生骨料取代率100%时的各项力学性能，又可达到再生骨料100%利用的目的；推荐R-RACFST合理配筋率范围为0.84%～3.9%;修正的承载力计算式稳定可靠。     

高温后中空夹层钢管再生混凝土短柱的加固性能研究与分析

针对高温煅烧后的再生混凝土进行荷载特性研究,设计了三种再生骨料取代率(0%,50%和100%)的中空夹层钢管再生混凝土短柱,研究了高温后钢管再生混凝土短柱及其加固后的力学性能,比较了截面形式、再生骨料取代率以及玄武岩纤维对其承载力、应变和位移的影响。结果表明,截面形式对承载力的影响最大。最后,利用再生骨料取代率、温度对其抗压强度的影响关系,尝试建立中空夹层钢管再生混凝土轴压强度承载力关于截面形式、约束系数、温度、再生骨料取代率以及外加固纤维布约束面积等变量的相关关系式,并通过试验数据加以验证。     

不同再生粗骨料取代率对再生混凝土短柱承载能力的影响研究

为探究再生混凝土短柱的承载能力与再生粗骨料取代率之间关联性,取废弃混凝土破碎、清洗、筛分后,依据普通混凝土配合比制备再生混凝土并制作再生混凝土短柱试样,同时制作普通混凝土短柱试样以做对比,开展轴心受压试验,观察混凝土短柱破坏情况,分析其承载能力差异。试验结果表明,普通混凝土短柱和再生混凝土短柱之间破坏机理大致相同,其中随着再生粗骨料掺量的提升,再生混凝土短柱承载力水平出现缓慢降低,再生混凝土短柱掺入15%再生骨料时承载力为普通混凝土短柱的94%左右,因此认为适宜掺量条件下再生混凝土短柱具有一定应用价值。     

高温后圆钢管再生混凝土轴压短柱的极限承载力研究

为了研究火灾高温后圆钢管再生混凝土轴压短柱的受力性能及极限承载力,以再生粗骨料取代率、恒温温度和恒温时间为变化参数,对20个设计的圆钢管再生混凝土短柱试件进行火灾高温后的力学性能试验。并对各变化参数对圆钢管再生混凝土短柱极限承载力的影响进行分析。利用统一强度理论和叠加计算理论分别计算高温后其极限承载力,并与试验实测结果比较。研究结果表明:高温后钢管再生混凝土短柱的受力破坏过程和形态与普通钢管混凝土柱相似;火灾温度对承载力影响显著;同一温度下,承载力随恒温时间的延长呈先上升后下降的趋势;骨料取代率对试件的承载力影响不大;采用统一强度理论中钟善桐计算法对高温后圆钢管再生混凝土短柱的极限承载力进行计算,计算值与试验值吻合较好。     

钢管再生混凝土柱塑性铰长度试验研究

为研究钢管再生混凝土柱的塑性铰长度,以再生粗骨料取代率、长细比、轴压比和含钢率为变化参数,对10个圆钢管再生混凝土柱和6个方钢管再生混凝土柱试件进行拟静力试验。根据试件的破坏形态、滞回曲线,并基于等效塑性铰理论,提出压弯状态下圆钢管再生混凝土柱和方钢管再生混凝土柱的等效塑性铰长度计算公式。研究结果表明:钢管再生混凝土柱破坏形态与普通钢管混凝土柱相似,钢管底部鼓曲破坏,底部的核心再生混凝土被压碎;钢管再生混凝土柱滞回曲线比较饱满,其形状从梭形发展到弓形,当再生粗骨料的取代率分别为0%,30%,70%,100%时,试件的滞回曲线受其影响不大;圆钢管再生混凝土柱等效塑性铰长度是其截面高度的0.45~0.95倍,方钢管再生混凝土柱等效塑性铰长度是其截面高度的0.65~0.75倍。     

高温后再生混凝土的变形性能试验

再生混凝土高温性能直接影响到再生混凝土结构的火灾安全。进行了粗骨料替代率分别为0、25%、50%、75%、100%的再生混凝土棱柱体(100 mm×100 mm×300 mm)在经历常温,150、300、450、600、750℃各温度后的单轴受压变形性能试验,获得了不同粗骨料取代率再生混凝土经历不同高温后完整的应力应变曲线,得到了高温后弹性模量和峰值应变。试验表明,在同一再生粗骨料取代率下,随着经历的温度升高,再生混凝土单轴受压应力应变曲线上升段与下降段越来越平缓,其弹性模量逐渐降低,峰值应变逐渐增大,其变化幅度随温度大小不同有所变化。高温后再生混凝土弹性模量和峰值应变随着再生粗骨料取代率的变化并不呈现单一的变化规律,而是随温度大小而不同。     

CFRP方钢管再生混凝土短柱轴压试验研究

进行了6根CFRP方钢管再生混凝土短柱和2根方钢管再生混凝土短柱的轴压性能试验。研究了再生粗骨料取代率、CFRP包裹层数对CFRP方钢管再生混凝土短柱受力性能的影响。试验结果表明,CFRP方钢管再生混凝土短柱的承载力随着再生粗骨料取代率的增加而降低;增加CFRP包裹层数,其试件承载力变大。     

足尺再生混凝土柱小偏压受力性能试验研究

再生混凝土柱受压性能是再生混凝土框架抗震设计的关键。进行了3个足尺再生混凝土柱试件小偏心受压性能试验,采用单向重复加载。各试件纵筋及箍筋配筋相同,3个试件粗骨料取代率分别为0,50%,100%,细骨料为普通砂,粗骨料取代率0的试件为普通混凝土试件。分析了各试件的破坏形态、承载力、刚度、延性、混凝土应变、钢筋应变。研究表明:小偏心受压下,再生混凝土柱的损伤过程及破坏形态与普通混凝土柱类似,两个再生混凝土试件承载力与普通混凝土试件接近,刚度略小于普通混凝土试件,粗骨料取代率50%的试件延性较好,粗骨料取代率100%的试件延性与普通混凝土试件相当,可近似参照现行规范进行再生混凝土柱小偏心受压承载力设计。     

钢管再生混凝土与钢筋再生混凝土轴压短柱力学性能对比试验研究

进行了12个钢管再生混凝土和12个配置螺旋箍筋的钢筋再生混凝土轴压短柱试验,在用钢量相同的情况下,对比分析了钢管再生混凝土短柱与钢筋再生混凝土短柱二者轴压力学性能的差异;分析了核心再生混凝土强度及再生粗骨料取代率等主要试验参数对钢管再生混凝土与钢筋再生混凝土轴压短柱力学性能的影响。试验结果表明：与用钢量相同的钢筋再生混凝土试件相比,钢管再生混凝土试件表现出较好的力学性能;钢管再生混凝土轴压短柱套箍系数较小时（ξ<1.0）,发生剪切破坏;再生粗骨料取代率对钢管混凝土短柱极限荷载的影响幅度相对钢筋再生混凝土短柱较小;核心再生混凝土强度对轴压短柱力学性能的影响规律与相应的钢管普通混凝土短柱和钢筋普通混凝土短柱类似。     

Experimental behaviour of RACFST stub columns after exposed to high temperatures

The experimental studies on the behaviour of recycled aggregate concrete-filled steel tube (RACFST) stub columns after exposed to high temperatures are reported in this paper. Forty specimens, including 32 RACFST stub columns and 8 normal concrete-filled steel tube (CFST) stub columns as reference, were tested, and the failure pattern, load versus strain relation and ultimate strength of the specimens were presented and analysed. Five types of concrete were produced: one reference concrete with natural aggregates, two concrete mixes with recycled coarse aggregate (RCA) replacement ratios of 50% and 100%, and two concrete mixes with recycled fine aggregate (RFA) replacement ratios of 50% and 100%. The specimens were exposed to 300 °C, 600 °C and 800 °C for 3 h. The test results showed that, due to the existence of the recycled aggregates, the post-fire performance of RACFST stub columns was lower than the corresponding normal CFST specimens under the same maximum temperature suffered, and the RACFST specimens with RCA had a better behaviour than those with RFA under the same recycled aggregate replacement ratio.     

Performance and calculations of recycled aggregate concrete-filled steel tubular (RACFST) short columns under axial compression

This paper describes a series of tests on steel tubular short columns of circular section filled with normal concrete (NA) and recycled aggregate concrete (RAC). Twenty-two specimens, including 11 small diameter of RAC-filled steel tubular (RACFST) columns named CA series and 11 larger diameter of RACFST columns called CB series, were tested to research the influence of variations in confinement index and replacement ratio of recycled coarse aggregate (RCA), from 0% to 100% with 10% increasing. The test results show that both types of RACFST columns and normal concrete-filled steel tubular (CFST) columns failed due to oblique shear pressure damage with a drum-like. Comparisons are made with predicted bearing capacities of RACFST columns using the existing theories, such as Unified Strengthen theory (I), Confinement theory (II) and Superposition theory (III). The equation for axial compression stress-strain curves of the whole process are proposed in this investigation for RACFST short columns, which can be directly used in theoretical and numerical analysis as well as practical engineering design and evaluation of RACFST structures.     

Experimental behaviour of recycled aggregate concrete filled steel tubular columns

This paper describes a series of tests on steel tubular columns of circular and square section filled with normal concrete and recycled aggregate concrete. Thirty specimens, including 24 recycled aggregate concrete filled steel tubular (RACFST) columns and 6 normal concrete filled steel tubular (CFST) columns, were tested to investigate the influence of variations in the tube shape, circular or square, concrete type, normal concrete and recycled aggregate concrete, and load eccentricity ratio, from 0 to 0.53 on the performance of such composite columns. The test results show that both types of filled columns failed due to overall buckling. Comparisons are made with predicted ultimate strengths of RACFST columns using the existing codes, such as ACI 318-1999, AIJ-1997, AISC-LRFD-1999, BS5400-1979, DBJ13-51-2003 and EC4-1994. A theoretical model for normal CFST columns is adopted in this paper for RACFST columns. The predicted load versus deformation relationships are in good agreement with test results.     

Behaviors of recycled aggregate concrete-filled steel tubular columns under eccentric loadings

The paper investigates the behaviors of recycled aggregate concrete-filled steel tubular (RACFST) columns under eccentric loadings with the incorporation of expansive agents. A total of 16 RACFST columns were tested in this study. The main parameters varied in this study are recycled coarse aggregate replacement percentages (0%, 30%, 50%, 70%, and 100%), expansive agent dosages (0%, 8%, and 15%) and an eccentric distance of compressive load from the center of the column (0 and 40 mm). Experimental results showed that the ultimate stresses of RACFST columns decreased with increasing recycled coarse aggregate replacement percentages but appropriate expansive agent dosages can reduce the decrement; the incorporation of expansive agent decreased the ultimate stresses of RACFST columns but an appropriate dosage can increase the deformation ability. The recycled coarse aggregate replacement percentages have limited influence on the ultimate stresses of the RACFST columns and has more effect than that of the normal aggregate concrete-filled steel tubular columns.     

圆钢管钢筋再生混凝土短柱轴压承载力

针对再生混凝土相对普通混凝土延性较差、承载力较低的特点,利用钢管和钢筋笼对再生混凝土的约束作用,将钢筋再生混凝土灌入圆钢管中形成圆钢管钢筋再生混凝土短柱进行研究。基于极限分析法、套箍理论以及双剪统一强度理论,考虑钢管和钢筋笼的双重约束效应,提出了一套包含钢管径厚比、约束效应系数、含钢率以及再生粗骨料取代率等影响因素的圆钢管钢筋再生混凝土短柱轴压承载力计算方法。在理论推导的基础上,考虑短柱的非线性、钢管与再生混凝土的滑移影响,采用ABAQUS有限元软件对圆钢管钢筋再生混凝土短柱进行建模分析; 将理论公式值、有限元仿真结果以及相关文献试验数据进行对比,验证公式的有效性与适用性。结果表明:加了钢筋笼的圆钢管钢筋再生混凝土比圆钢管再生混凝土短柱轴压承载力提高10%左右,研究结论可以为实际工程的应用提供理论基础。     

钢管再生混凝土构件受力机理研究

在确定钢管与核心再生混凝土本构关系模型的基础上,采用有限元法对钢管再生混凝土轴压短柱、纯弯构件和压弯构件的破坏模态和荷载-变形关系曲线进行全过程分析,揭示出受力过程中钢管与核心再生混凝土截面应力分布规律及钢管与核心再生混凝土之间的相互作用,较为深入地认识了静力荷载作用下钢管再生混凝土构件的工作机理。     

Testing of self-consolidating concrete-filled double skin tubular stub columns exposed to fire

A concrete-filled double skin tube (CFDST) is an innovative steel and concrete composite construction with the potential to be used as columns in high-rise buildings. Self-consolidating concrete (SCC) can offer convenience for construction and ensure the construction quality of CFDST columns. There is very limited knowledge about the fire performance of CFDST columns, which is a key issue in the application to high-rise buildings. This paper reports an experimental investigation into the fire behaviour of CFDST stub columns filled with SCC and fibre reinforced SCC. The study aims to obtain thermal and structural responses of the stub columns through standard fire testing. Details are given in terms of the failure mode, temperature distribution, critical or limiting temperature and fire resistance. It was found that the added fibre does not affect the temperature distribution whereas the increased concrete thickness and outer tube perimeter reduces the temperature in CFDST specimens. The added steel fibre increases the fire resistance of CFDST stub columns especially for load levels less than 0.6. The critical or limiting temperature for CFDST sections was found to be higher than for CFST (concrete-filled steel tube) or unfilled tubes.     

方钢管再生混凝土柱抗震性能试验研究

为研究方钢管再生混凝土柱的抗震性能,设计并制作了6个试件,对其进行拟静力试验。考虑再生粗骨料取代率和轴压比2个变化参数,观察试件受力的全过程和破坏形态,分析试件的滞回曲线、骨架曲线、延性、耗能性能和刚度退化等,并采用相关规程计算低周反复荷载作用下方钢管再生混凝土柱的压弯承载力。试验研究和计算结果表明：试件破坏过程以及破坏形态均与普通钢管混凝土柱试件相似,主要表现为试件根部钢管的鼓曲破坏;试件的滞回曲线比较饱满,滞回曲线的形状从梭形发展到弓形;在试验选取的再生粗骨料取代率参数范围内,试件的滞回曲线受其影响不大;试件的平均位移延性系数接近3;破坏时等效黏滞阻尼系数介于0.323~0.360之间;建议对采用规程GJB 4142-2000计算的反复荷载作用下方钢管再生混凝土柱的压弯承载力乘以0.92的折减系数;对采用规程DBJ 13.51-2003计算的反复荷载作用下方钢管再生混凝土柱的压弯承载力乘以1.13的扩大系数。     

高温喷水冷却后混凝土柱性能对比分析

为对比分析高温喷水冷却后3种约束再生混凝土柱（即螺旋筋再生混凝土柱、方钢管再生混凝土柱和圆钢管再生混凝土柱）的力学性能退化规律,以截面类型、历经温度和再生粗骨料取代率为变化参数,共设计了36个试件,进行高温喷水冷却后的轴心受压加载试验,观察了试件破坏全过程,并对比分析高温喷水冷却后这3种约束再生混凝土柱的极限承载力、初始轴压刚度和延性的差异。结果表明：随历经最高温度的增大,各种约束再生混凝土柱的极限承载力、初始轴压刚度和延性均出现了不同程度的退化,其中圆钢管再生混凝土柱退化幅度最小且较为稳定,方钢管再生混凝土柱的延性随温度升高出现了正增长;随再生粗骨料取代率的增加,方钢管和圆钢管试件的极限承载力、初始轴压刚度和延性呈现先减小后增大的变化趋势,其波动范围为-15.3%~2.3%,而螺旋筋约束混凝土柱试件受取代率影响则相对较小,其变化范围为0~12.9%。