• 대한건축학회논문집:구조계
• /
• 제35권3호
• /
• pp.27-33
• /
• 2019

The purpose of this study is to provide and evaluate the tensile properties of masonry element such as tensile strength, strain, modulus of elasticity and stress-strain relationship through the direct tension test with varies of mortar strength. From the experiment, the tension fracture was observed along the interfaces between the brick and the mortar. Tension properties of masonry element was significantly affected by compressive strength of mortar, $f_m$, indicating that higher tensile strength and modulus of elasticity of masonry element were obtained with increase of $f_m$. The strain of a masonry element was inversely proportional to $f_m$ due to the lower ductility of a higher mortar strength. A tensile stress-strain relationship of masonry element was generalized based on the numerical analysis and the regression analysis using test data. The proposed model shows fairly good agreement with the test measurements.

• Structural Engineering and Mechanics
• /
• 제5권3호
• /
• pp.239-256
• /
• 1997

The companion paper presents a new three-parameter model for the uniaxial rate-sensitive material response, which is based on a bilinear static stress-strain relationship with kinematic strain-hardening. This paper extends the proposed model to trilinear static stress-strain relationships for steel and concrete, and discusses the implementation of the new models within an incremental-iterative solution procedure. For steel, the three-parameter rate-function is employed with a trilinear static stress-strain relationship, which allows the utilisation of different levels of rate-sensitivity for the plastic plateau and strain-hardening ranges. For concrete, on the other hand, two trilinear stress-strain relationships are used for tension and compression, where rate-sensitivity is accounted for in the strain-softening range. Both models have been implemented within the nonlinear analysis program ADAPTIC, which is used herein to provide verification for the models, and to demonstrate their applicability to the rate-sensitive analysis of steel and reinforced concrete structures.

• 한국지반공학회논문집
• /
• 제18권1호
• /
• pp.41-48
• /
• 2002

공중낙하법에 의해 만든 등방압밀 모래공시 체를 미소변형률 측정장치를 사용한 평면변형률압축시험을 실시하여 미소변형률에서 파괴후까지의 응력-다이레이턴시(stress-dilatancy) 관계를 연구하였다. 세계 각국의 주요 연구기관에서 사용되고 있는 7종류의 연구용 표준사 공시체를 멤브레인의 관입에 의한 오차와 변위를 외부에서 측정함으로 하여 생기는 오차(bedding error) 등의 영향을 제거하여 측정한 최대주응력방향의 변형률과 최소주응력방향의 변형률을 각각 0.0001%에서 파괴 시까지의 응력-변형률 관계를 얻었다. 그 결과 미소변형률 수준에서 파괴 시가지의 주응력비-주변헝률증분비 관계는 과압밀비 및 구속압에 거의 영향을 받지 않고 동일하였다. 또한 미소변형률에서는 이방성이 주응력비-주변형률증분비 관계에 미치는 영향은 거의 없지만, 파괴 부근에서의 K값의 크기는 $\delta$에 따라 다른 값을 나타내었다. 한편, K값은 모래의 종류에 따라 다른 값을 나타내었다. 전체적으로 Rowe의 응력-다이레이턴시식은 미소변형를에서 파괴까지 근사적으로 성립한다는 것을 알았다.

• Advances in concrete construction
• /
• 제2권3호
• /
• pp.177-192
• /
• 2014

One of the main applications of FRP composites is confining concrete columns. Hence identifying the cyclic and monotonic stress-strain behavior of confined concrete columns and the parameters influencing this behavior is inevitable. Two significant parameters affecting the stress-strain behavior are aspect ratio and corner radius. The present study aims to scrutinize the effects of corner radius and aspect ratio on different aspects of stress-strain behavior of FRP confined concrete specimens (rectangular, square and circular). Hence 44 FRP confined concrete specimens were tested and the results of the tests were investigated. The findings indicated that for specimens with different aspect ratios, the relationship between the ultimate stress and the corner radius is linear and the variations of the ultimate stress versus the corner radius decreases as a result of an increase in aspect ratio. It was also observed that increase of the corner radius results in increase of the compressive strength and ultimate axial strain and increase of the aspect ratio causes an increase of the ultimate axial strain but a decrease of the compressive strength. Investigation of the ultimate condition showed that the FRP hoop rupture strain is smaller in comparison with the one obtained from the tensile coupon test and also the ultimate axial strain and confined concrete strength are smaller when a prism is under monotonic loading. Other important results of this study were, an increase in the axial strain during the early stage of unloading paths and increase of the confining effect of FRP jacket with the increase and decrease of the corner radius and aspect ratio respectively, a decrease in the slope of reloading branches with cycle repetitions and the independence of this trend from the variations of the aspect ratio and corner radius and also quadric relationship between the number of each cycle and the plastic strain of the same cycle as well as the independence of this relationship from the aspect ratio and corner radius.

• Structural Engineering and Mechanics
• /
• 제60권1호
• /
• pp.91-110
• /
• 2016

Tube hydroforming (THF) under pulsating hydraulic pressures is a novel technique that applies pulsating hydraulic pressures that are periodically increased to deform tubular materials. The deformation behaviours of tubes in pulsating THF may differ compared to those in conventional non-pulsating THF due to the pulsating hydraulic pressures. The equivalent stress-strain relationship of metal materials is an ideal way to describe the deformation behaviours of the materials in plastic deformation. In this paper, the equivalent stress-strain relationships of SS304 tubes in pulsating hydroforming are determined based on experiments and simulation of free hydraulic bulging (FHB), and compared with those of SS304 tubes in non-pulsating THF and uniaxial tensile tests (UTT). The effect of the pulsation parameters, including amplitude and frequency, on the equivalent stress-strain relationships is investigated to reveal the plastic deformation behaviours of tubes in pulsating hydroforming. The results show that the deformation behaviours of tubes in pulsating hydroforming can be well described by the equivalent stress-stain relationship obtained by the proposed method. The amplitude and frequency of pulsating hydraulic pressure have distinct effects on the equivalent stress-strain relationships-the equivalent stress becomes augmented and the formability is enhanced with the increase of the pulsation amplitude and frequency.

• 대한토목학회논문집
• /
• 제29권4C호
• /
• pp.175-182
• /
• 2009

본 연구에서는 불포화토의 삼축시험시 응력-변형률 관계를 Bishop 응력으로 기술하여 분석하였다. 불포화토의 파괴포락선은 Bishop 응력으로 기술할 경우에 모관흡수력에 무관하게 유일한 관계를 나타내고 있었다. 특히 모관흡수력이 낮은 경우에는 선형적인 관계를 나타내며 실험치와 이론치가 잘 일치하고 있었다. 미소변형률 영역에서의 변형계수는 대체로 Bishop 응력에 따라 선형적으로 증가하는 추세를 보이고 있었다.

• International Journal of Concrete Structures and Materials
• /
• 제10권2호
• /
• pp.221-236
• /
• 2016

The aim of this paper is to investigate the compressive behavior and characteristics of amorphous metallic fiber-reinforced concrete (AMFRC). Compressive tests were carried out for two primary parameters: fiber volume fractions ($V_f$) of 0, 0.3, 0.6 and 0.8 %; and design compressive strengths of 27, 35, and 50 MPa at the age of 28 days. Test results indicated that the addition of amorphous metallic fibers in concrete mixture enhances the toughness, strain corresponding to peak stress, and Poisson's ratio at high stress level, while the compressive strength at the 28-th day is less affected and the modulus of elasticity is reduced. Based on the experimental results, prediction equations were proposed for the modulus of elasticity and strain at peak stress as functions of fiber volume fraction and concrete compressive strength. In addition, an analytical model representing the entire stress-strain relationship of AMFRC in compression was proposed and validated with test results for each concrete mix. The comparison showed that the proposed modeling approach can properly simulate the entire stress-strain relationship of AMFRC as well as the primary mechanical properties in compression including the modulus of elasticity and strain at peak stress.

• 한국공간구조학회논문집
• /
• 제1권2호
• /
• pp.93-100
• /
• 2001

A stress-strain relationship for reinforced concrete membrane elements subjected to reversed cyclic loading is quite different to that of concrete cylinder subjected to uniaxial compression. The compressive strength of cracked concrete membrane elements is reduced by cracking due to tension in the perpendicular direction. Based on the three reinforced concrete panel tests, a softened stress-strain curve of concrete subjected to reversed cyclic loading is proposed. The proposed model consists of seven stages in the compressive zones and six stages in the tensile zones. The proposed model is verified by comparing to the test results.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
• /
• pp.406-412
• /
• 1997

This paper presents the newly developed model for the stress-strain relationship of ultra high- strength concrete on the basis of the more refined statistical to analysis the various test results available in the literature to be more rigorous in accuracy and generalized scheme. Through the comprehensive analysis of the previously existing equations for each model, multiple curves equation has turned out to be most appropriate to simulate the linearly varying ascending branch and brittle type of descending one. The principal variables to model the stress-strain relationship such as the modulus of elasticity, ultimate strain and deformation characteristics due to stress softening phenomenon were extensively studied to be simplified in the function of the concrete compressive strength.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.53-58
• /
• 2003

Many researchers have rigorously studied the nonlinear behavior of stress-strain relationship of concrete using mathematical curves. Most of model equations for stress-strain relationship, however, have been focused on old age concrete, and were not able to adequately represent the behavior of concrete at an early age. A wide understanding on the behavior of concrete from early age to old age is very important in evaluating the durability and service life of concrete structures. In previous study by authors of this paper, a stress-strain model equation for low- and medium-strength concretes was suggested. In this paper, to extend the application region of compressive stress-strain curve to high-strength concrete, an analytical research was performed. An analytical expression of stress-strain curve with strength and age was developed using regression analyses on the experimental results. For the verification of the proposed model equation, it was compared to the experimental data. The result showed that the proposed model equation was not only compatible with the experimental data quite satisfactorily but also describing well the effect of strength and age on stress-strain curve.