size Effect on compressive Behavior of Plain and Confined Concrete

1)研究了试件尺寸和骨料尺寸对素混凝土和约束混凝土非弹性应力-应变行为的影响。研究表明：a)对于集料尺寸与试件尺寸成比例减小的普通混凝土，抗压强度随试件或集料尺寸的增大而增大，应力-应变曲线的下降部表现出更强的脆性；b)在空气中养护时，约束混凝土的抗压强度随着试件尺寸的增加而增加。另一方面，在水养护试件中，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，其影响程度取决于…。2)进行了一系列约束混凝土单轴抗压试验，考察了尺寸效应对其受压性能的影响。混凝土的强度从300-700kgf/cm2变化到约1000kgf/cm2的超高水平。在试验结果的基础上，讨论了试件尺寸对约束混凝土抗压强度、峰值应力应变和应力-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的应力-应变行为的影响。实验因素包括试件的截面尺寸(BXB，b=9.7，15，20和25 cm)，箍的节距(比例节距和固定节距)，以及箍的类型(矩形箍和带十字型紧箍的矩形箍)。普通混凝土骨料的最大尺寸为15 mm，微细混凝土的最大骨料尺寸为12、9和6 mm。试验结果表明：在相同的配筋率下，定箍距约束混凝土(S=1.6 cm，矩形箍)强度的尺寸效应小于比例箍距大试件的尺寸效应(S=b/6，S=1.6 cm，b=9.7 cm)，但尺寸效应对应力-应变行为的影响仍然比较显著。b)观察到约束混凝土和普通混凝土应力-应变曲线的尺寸效应。这些公式考虑了试件截面尺寸、箍间距(比例间距)、混凝土强度和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。较少

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