size Effect on compressive Behavior of Plain and Confined Concrete

在本研究中，进行了以下四项研究，以研究尺寸对混凝土棱镜在单轴压缩下的压缩行为的影响。1)研究了试件尺寸和骨料尺寸对普通混凝土和约束混凝土非弹性应力-应变特性的影响。从这项研究中可以得出以下结论。a)当骨料尺寸与试样尺寸不成比例减小时，随着试样或骨料尺寸的增大，其抗压强度增大，应力-应变曲线下降部分表现出更强的脆性行为。b)空气养护时，约束混凝土的抗压强度随试件尺寸的增大而增大。另一方面，水固化试样的尺寸效应几乎可以忽略不计。随着试件尺寸的增大，约束混凝土的应力-应变曲线表现出更强的脆性，且这种尺寸效应的程度取决于环箍间距的增大。2)进行了一系列约束混凝土单轴压缩试验，考察了尺寸对其压缩性能的影响。混凝土的强度从约300-700 kgf/cm^2到约1000 kgf/cm^2的超高水平不等。根据试验结果，讨论了试件尺寸对约束混凝土抗压强度、峰值应力应变及应力-应变曲线的影响。3)研究了试件尺寸对约束混凝土和约束微混凝土棱柱应力-应变特性的影响。试验因素包括试件截面尺寸（bxb, b=9.7,15,20和25cm），箍节距（比例箍节和固定箍节），箍型（矩形箍和矩形箍带十字型subtie）。普通混凝土的骨料最大粒径为15mm，微混凝土的骨料最大粒径为12,9和6mm。从测试结果可以得出以下结论。a)在相同的侧配筋比下，固定箍节距（S=1.6cm，矩形箍节）约束混凝土的尺寸效应小于比例箍节距（S=b/6，当b=9.7cm时S=1.6cm）约束混凝土的强度效应，但尺寸效应对应力-应变行为的影响仍相当显著。b)观察了承压微混凝土的应力-应变曲线的尺寸效应，以及普通混凝土的尺寸效应。4)提出了考虑试件尺寸的约束混凝土应力-应变曲线的完整公式。这些公式考虑了试件截面尺寸、围箍节距（比例节距）、混凝土强度和围箍屈服强度等试验因素。公式计算结果与试验结果吻合较好。少

In the present study, following four studies were carried out to examined the size effect on the compressive behavior of concrete prism under uniaxial compression..1)In the present study, the effects of the specimen size and aggregate size on the inelastic stress-strain behavior of plain and confined concrete were examined. The following statement can be drawn from the study.a)For air cured plain microconcrete in which the size of aggregate is reduced inproportion to the size of a specimen, the compressive strength increased and the descending portion of stress-strain curve showed more brittle behavior with increasing size of specimen or aggregate.b)The compressive strength of confined concrete increased with increasing size of specimen when cured in air. On the other hand, the size effect was almost negligible in water cured specimens. The stress-strain curve of confined concrete showed more brittle behavior with increasing size of specimen and degree of such size effectdepended on th … More e spacing of hoops.2)A series of uniaxial compression tests of confined concretes were carried out to examine the size effects on their compressive behavior. The strength of concrete has been varied from about 300-700 kgf/cm^2 to the ultra-high level of about 1000 kgf/cm^2. Based on the test results, discussion was carried out concerning the effect of specimen size on compressive strength, strain at the peak stress, and stress-strain curves of confined concrete.3)The effects of specimen size on stress-strain behavior of confined concrete and confined micro-concrete prism are examined. Experimental factors include the section size of specimen (bxb, b=9.7,15,20 and 25cm), the pitch of hoops (proportional pitch and fixed pitch), and the type of hoops (rectangular hoop and rectangular hoop with cross type subtie). The maximum sizes of aggregate are 15mm for normal concrete, and 12,9 and 6mm for microconcrete. Following statements can be drawn from the test results.a)For the same lateral reinforcement ratio, size effect on the strength of confined concrete with fixed pitch of hoop (S=1.6cm, rectangular hoop) is smaller than thoseof large specimen with proportional pitch of hoop (S=b/6, S=1.6cm for b=9.7cm), but the size effect on the stress-strain behavior is still rather remarkable.b)The Size effect of stress-strain curves of confined microconcrete are observed, as well as that of normal concrete.4)The comprete formulas of stress-strain curves of the confined concrete considering specimen sizes are proposed. These formulas considerthe experimental factors including the section size of specimen, the pitch of hoops (proportional pitch), concrete strength and yield strength of hoops. The results from the formulas agree well with the test results. Less