Axial stress–strain relationship for FRP confined circular and rectangular concrete columns

A general mathematical model is developed to describe the stress–strain (f_c–ε_c) relationship of FRP confined concrete. The relationship is applicable to both circular and rectangular columns, and accounts for the main parameters that influence the stress–strain response. These include the area and material properties of the external FRP wraps, the aspect ratio of rectangular column sections, the corner radius used for FRP application, and the volumetric ratio and configuration of internal transverse steel. The proposed model reproduced accurately experimental results of stress–strain or load–deformation response of circular and rectangular columns. In addition to its importance in evaluating the effect of FRP confinement on the ultimate axial strength of concrete columns, the developed f_c–ε_c relationship can be employed very efficiently and effectively for analyzing the response of FRP confined concrete under different types of load application.     

纤维增强聚合物复合材料-钢复合圆管约束混凝土轴压性能预测模型

纤维增强聚合物复合材料（FRP）-钢复合圆管约束混凝土由于具有很好的综合性能,近年来得到了广泛的研究,尚缺乏完整的应力-应变关系全曲线计算模型。本文在综合作者现有研究成果的基础上,广泛收集了96个FRP-钢复合圆管约束混凝土柱的轴心受压试验结果,系统分析了试件参数的影响规律,提出了FRP-钢复合圆管约束混凝土的应力-应变关系曲线的完整计算模型,包括峰值应力、峰值应变、极限应力和极限应变的计算方法,并建议了应力-应变关系全曲线预测模型,模型较好地预测了FRP-钢复合圆管约束混凝土的应力-应变关系曲线的特征,预测结果与试验结果吻合较好。建议模型具有较好的通用性和准确性。      

Behavior of air-entrained concrete under the compression with constant confined stress after freeze–thaw cycles

Properties of air-entrained concrete under compressive loads with constant confined stress after 0, 100, 200, 300 and 400 cycles of freeze–thaw were studied. The failure characteristic of specimens and the direction of the crack are observed. Based on the test data, the influence of freeze–thaw cycles and lateral compressive stress ratio on the ultimate compressive strength is analyzed, respectively. The relationships between the ultimate compressive strength and freeze–thaw cycles, lateral compressive stress ratio are given, respectively. The unified failure criterion with consideration of the influence of freeze–thaw cycles and stress ratio is proposed. It provides the experimental and theory foundations for strength analysis of air-entrained concrete structures subject to complex loads in cold environment.