一种RDX基PBX炸药力学性能和本构关系研究

利用分离式霍普金森压杆(SHPB)对一种RDX基PBX炸药进行了高应变率加载试验,得到了其在不同应变率(300~1 200 s-1)范围内的力学性能,并用扫描电子显微镜(SEM)对回收样品进行了微观分析。结果表明:材料的力学性能和损伤均具有明显的应变率效应。采用含损伤的ZWT非线性黏弹性本构模型,对试验数据进行了拟合,拟合曲线和试验曲线吻合良好。     

Experimental investigation and optimisation in drilling of GFRP composites

Glass fibre-reinforced polymer (GFRP) composite materials are one of the important materials and are economic alternative to engineering materials because of their superior properties. This paper presents an effective approach for the optimisation of drilling parameters with multiple performance characteristics based on the Tagugch’s method with grey relational analysis. Taguchi’s L₁₆, 4-level orthogonal array has been used for the experimentation. The drilling parameters such as spindle speed and feed rate are optimised with consideration of multiple performance characteristics, such as thrust force, workpiece surface roughness and delamination factor. Response table and response graph are used for the analysis. The analysis of grey relational grade indicates that feed rate is the more influential parameter than spindle speed. The results indicate that the performance of drilling process can be improved effectively through this approach.     

Experimental study and code predictions of fibre reinforced polymer reinforced concrete (FRP RC) tensile members

Due to their different mechanical properties, cracking and deformability behaviour of FRP reinforced concrete (FRP RC) members is quite different from traditional steel reinforced concrete (SRC) having great incidence on their serviceability design. This paper presents and discusses the results of an experimental programme concerning concrete tension members reinforced with glass fibre reinforced polymer (GFRP) bars. The main aim of the study is to evaluate the response of GFRP reinforced concrete (GFRP RC) tension members in terms of cracking and deformations. The results show the dependence of load-deformation response and crack spacing on the reinforcement ratio. The experimental results are compared to prediction models from codes and guidelines (ACI and Eurocode 2) and the suitability of the different approaches for predicting the behaviour of tensile members is analysed and discussed.     

GFRP管钢筋混凝土短柱力学性能研究

为研究GFRP管钢筋混凝土短柱的力学性能,对14根GFRP管钢筋混凝土短柱和2根无套管短柱进行轴压试验,通过试验,分析了影响套管钢筋混凝土短柱的部分因素,试验结果表明：对于在不同受力方式下的试件,其承载力与变形能力都基本相同;GFRP管有很强的约束能力,由于GFRP管的约束,使得混凝土的强度得到明显的提高,变形能力也得到明显的增加;对于配置有纵筋的试件,既可以提高试件的承载力,又可以避免核心混凝土发生剪切破坏。     

GFRP管劲性钢筋混凝土组合柱轴心抗压承载力计算

通过8根组合柱的试验,分析了影响GFRP管劲性钢筋混凝土组合柱的轴心受压承载力主要因素。试验结果表明,组合柱的承载力随着GFRP管壁厚度的增加而提高;内部型钢约束混凝土并与钢筋共同承担一定荷载,提高了组合柱的承载力。基于极限平衡理论和统一理论,分别建立了GFRP管劲性钢筋混凝土组合柱和GFRP管钢筋混凝土组合柱的轴压承载力计算公式,计算结果与试验结果吻合良好。统一理论的计算结果与试验结果更为接近,且计算公式简单。     

无机材料植筋拉拔性能试验研究

通过拉拔法试验及理论分析,探讨了混凝土结构无机材料植筋拉拔技术的影响因素,分析了混凝土强度、植筋锚固深度、钢筋外形、直径对无机材料植筋技术的影响,为今后的《混凝土结构工程无机材料后锚固技术规程》的编制提供了理论依据。     

Influence of fibers on flexural behavior and ductility of concrete beams reinforced with GFRP rebars

This research studies the influence of fibers on flexural behavior and ductility of concrete beams reinforced with GFRP bars. The experimental program included seven beams. The tested beams were divided into four groups. Each of the first three groups consisted of two beams one of normal strength and the other of high strength while the fourth group consisted of one normal strength beam. The first group is the reference group which had no internal fibers. The second group studied the effect of using internal polypropylene fibers in the concrete mix. The third group studied the effect of using internal glass fibers in the concrete mix while the fourth group studied the effect of using internal steel fibers in the concrete mix. The experimental results of tests showed that using GFRP as the main reinforcement for the concrete beams achieves reasonable flexural strength. Also the theoretical results calculated using ACI 440 code showed good agreement with the experimental results with an error of about 20%. The results of the current research indicated that all types of the fibers used improved the ductility of FRP- reinforced concrete beams. It was found that the span-to-experimental service load deflection ratio is relatively high when compared to the usually accepted ratio of about span/250.     

GFRP筋活性粉末混凝土梁受力性能试验研究

为了研究GFRP筋活性粉末混凝土梁的受力性能,对8根梁进行三分点加载试验,获得了试验梁的开裂弯矩、极限弯矩以及各级荷载作用下的变形及裂缝分布与开展。试验结果表明：活性粉末混凝土试验梁纯弯区段开裂应变 (750×10-6) 约为普通混凝土梁的7倍,开裂弯矩及截面塑性系数计算应考虑纵向受拉GFRP筋的有利影响。GFRP筋活性粉末混凝土梁正截面受弯破坏形式可分为纵向受拉GFRP筋被拉断而受压边缘活性粉末混凝土未被压碎的受拉破坏,受压边缘活性粉末混凝土被压碎(5500×10-6)而纵向受拉GFRP筋未被拉断的受压破坏,以及纵向受拉GFRP筋被拉断的同时受压边缘活性粉末混凝土被压碎的界限破坏等三种。对于受压破坏可按拉区应力为0.25倍活性粉末混凝土抗拉强度来考虑拉应力对正截面受弯承载力的贡献。对于受拉破坏则基于材料应力-应变关系通过数值积分迭代计算正截面受弯承载力。刚度及裂缝宽度计算的关键是合理计算使用阶段GFRP筋的拉应力,在计算GFRP筋拉应力时所用弯矩应为外荷载弯矩减去拉区活性粉末混凝土拉应力合力对压区合力点的弯矩。图9表12参10     

高温后HRBF500细晶粒钢筋力学性能试验研究

试验研究了16组共48根HRBF500细晶粒钢筋在常温和高温冷却作用后（5种温度、3种冷却方式）的力学性能,得到了不同高温冷却作用后细晶粒钢筋的应力-应变关系,分析了屈服强度、抗拉强度、弹性模量、断后伸长率、均匀伸长率、截面收缩率等的变化规律。试验表明：温度作用相对较低时(300℃、400℃、600℃),细晶粒钢筋力学性能变化不明显;温度作用相对较高时(700℃、900℃),细晶粒钢筋各项力学指标逐渐退化。根据试验结果,经回归分析建议了高温后细晶粒钢筋屈服强度、抗拉强度、弹性模量、断后伸长率的计算公式。研究成果可作为火灾后采用HRBF500级细晶粒钢筋混凝土结构的损伤评估的依据。图12表6参7     

纤维对GFRP筋与自密实混凝土基体粘结性能影响分析

通过18个中心拉拔试件试验,研究在基体中加入不同纤维(聚丙烯长纤维(PPA)、聚丙烯短纤维(PPB)、钢纤维(SF)以及混杂纤维)对玻璃纤维增强聚合物(GFRP)筋与混凝土基体粘结性能的影响,旨在寻找改善GFRP筋与混凝土基体粘结性能的有效途径。参照德国纤维混凝土标准DBV和国际材料与结构研究试验联合会标准RILEM弯曲韧性评价方法,采用等效抗弯强度和变形能来评价粘结韧性。试验结果表明：与素混凝土（NC）基体相比,GFRP筋与掺入混杂钢纤维与聚丙烯长纤维以及各自单掺基体的粘结强度可提高13%～35%,还可改善粘结韧性;同时,GFRP筋与基体的粘结强度随钢纤维掺量增大而提高。根据试验结果拟合得出粘结滑移曲线上升段的模型参数,计算结果与试验结果吻合良好。图11表6参13