• Computers and Concrete
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• v.11 no.2
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• pp.149-167
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• 2013

The complete stress-strain behavior of steel fiber reinforced concrete in compression is needed for the analysis and design of structures. An experimental investigation was carried out to generate the complete stress-strain curve of high-performance steel fiber reinforced concrete (HPSFRC) with a strength range of 52-80 MPa. The variation in concrete strength was achieved by varying the water-to-cementitious materials ratio of 0.40-0.25 and steel fiber content (Vf = 0.5, 1.0 and 1.5% with l/d = 80 and 55) in terms of fiber reinforcing parameter, at 10% silica fume replacement. The effects of these parameters on the shape of stress-strain curves are presented. Based on the test data, a simple model is proposed to generate the complete stress-strain relationship for HPSFRC. The proposed model has been found to give good correlation with the stress-strain curves generated experimentally. Inclusion of fibers into HPC improved the ductility considerably. Equations to quantify the effect of fibers on compressive strength, strain at peak stress and toughness of concrete in terms of fiber reinforcing index are also proposed, which predicted the test data quite accurately. Compressive strength prediction model was validated with the strength data of earlier researchers with an absolute variation of 2.1%.

• Computers and Concrete
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• v.21 no.2
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• pp.209-217
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• 2018

The dynamic compressive behavior of concrete after freezing and thawing tests are investigated by using the split Hopkinson pressure bar (SHPB) technique. The stress-strain curves of concrete under dynamic loading are measured and analyzed. The setting numbers of freeze-thaw cycles are 0, 25, 50, and 75 cycles. Test results show that the dynamic strength decreases and peak strain increases with the increasing of freeze-thaw cycles. Based on the Weibull distribution model, statistical damage constitutive model for dynamic stress-strain response of concrete after freeze-thaw cycles was proposed. At last, the fragmentation test of concrete subjected to dynamic loading and freeze-thaw cycles is carried out using sieving statistics. The distributions of the fragment sizes are analyzed based on fractal theory. The fractal dimensions of concrete increase with the increasing of both freeze-thaw cycle and strain rate. The relations among the fractal dimension, strain rates and freeze-thawing cycles are developed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.1
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• pp.72-78
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• 1999

The purpose of this study was to evaluate the properties of unconfined strength of dry soil which was reinforced with polypropylene fiber. It is found that unconfined compressive strength and strain of dry soil without fiber were decreased as water content was increased. As mixing ration of fiber was increased , unconfined compressive strength and failure strain of dry soil reinforced with polypropylene fiber were increased. When mixing ration was larger than 0.5 % , unconfined compressive strength was gradually increased. The longer fiber was, the largest post peak strength was obtained and the larger strain was reached. Tensile strength of dried fiber reinforced soil was larger than that of dry soil without fiber.

• Geomechanics and Engineering
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• v.32 no.5
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• pp.495-502
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• 2023

In this study, stress relaxation tests were carried out by keeping silt type soil specimens under different strain levels. Decreases in the stress values with time data was collected to better understand the effect of the strain level on the relaxation properties of soil specimens. In addition, the stress relaxation effect on the uniaxial compressive strength (UCS) values of the specimens was investigated with a series of tests. According to the results obtained from this study, the UCS values of the silt specimens significantly vary as a result of the stress relaxation effect. The UCS values were determined to increase with an increase of relaxation strain level to a threshold value. On the other hand, the UCS values were found to be affected adversely in case of high stress levels at the initiation of the relaxation, which are close to the peak level.

• Structural Engineering and Mechanics
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• v.16 no.4
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• pp.405-422
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• 2003

Scaled brick masonry panels were tested under cyclic unialxial compression loading to evaluate its deformation characteristics. An envelope stress - strain curves, a common point curves and stability point curves were obtained for various cyclic test conditions. Loops of the stress-strain hysteresis were used to determine the energy dissipation for each cycle. Empirical expressions were proposed for the relations between energy dissipation and envelope and residual strains. These relations indicated that the decay of masonry strength starts at about two-third of peak stress.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.291-300
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• 1994

The influence of elevated temperatures on the mechanical properties of concrete is important for fire-resistance studies and also for understanding the behavior of containment vessel, such as nuclear reactor pressure vessels, during service and ultimate condition. The present study is to clarify the damage/deterioration of concrete structures that are subjected to high temperature exposure. To this end, comprehensive experiments are conducted. The major test variables are the peak temperatures, rate of temperature increase, and sustained duration at peak temperature. The results include weight loss residual compressive strength and stress-strain curve. From those results, residua compressive strength formula and stress-strain relationship are proposed.

• Computers and Concrete
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• v.19 no.6
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• pp.609-615
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• 2017

In this paper, the effects of elevated temperatures on the strength and compressive stress-strain curve (SSC) of recycled coarse aggregate concrete with different replacement percentages are presented. 90 recycled coarse aggregate concrete prisms are heated up to 20, 200, 400, 600, $800^{\circ}C$. The results show that the compressive strength, split tensile strength, elastic modulus of recycled aggregate concrete specimens decline significantly as the temperature rise. While the peak strain increase of recycled aggregate concrete specimens as the temperature rise. Compared to the experimental curves, the proposed stress-strain relations for recycled aggregate concrete after exposure elevated temperatures can be used in practical engineering applications.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.89-96
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• 2010

This paper focuses on the effect of creep on the critical compressive strain (CCS) of concrete. The strain of concrete corresponding to the peak compressive stress is crucial in the selection of the ultimate yield strength of the reinforcing bar used in reinforced concrete columns. Among the various influencing factors, such as the creep, shrinkage, loading rate and confinement, the effect of creep and shrinkage is the most significant. So far, investigations into how these factors can affect the CCS of concrete have been rare. Therefore, to investigate the effect of creep and shrinkage on CCS, an experimental (part I) and a parametric study (part II) were conducted, as presented in these papers (part I considers creep effect, part II considers effect of creep and shrinkage). In part I, experiments pertaining to the loading age, loading rate, loading duration and loading and creep levels were conducted to study the effect of these variables on the CCS of concrete. It was found that the effects of the loading rate, loading age, and level and duration on the CCS of concrete were negligible. However, it is very important to consider the effect of creep.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.97-104
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• 2008

The objective of this study was to investigate the strength characteristics of frozen clay. Compressive strength tests were performed on frozen clay with different water contents at various temperatures. The dry density of specimens and strain rate was kept constant. Test results showed that compressive strength increased with increasing water content and decreasing temperature. The increase in peak strength became more significant the lower the temperature for a given water content. The failure mode changed from brittle to ductile deformation with increasing water content and decreasing temperature. Tests also showed an increase in deformation modulus with increasing peak strength, increasing water content and decreasing temperature.

• Computers and Concrete
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• v.19 no.5
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• pp.477-488
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• 2017

In this paper, an innovative technique for finite element (FE) modeling of steel tube-confined concrete (STCC) columns with active confinement under axial compressive loading is presented. In this method, a new constitutive model for the stress-strain relationship of actively-confined concrete is proposed. In total, 14 series of experimental STCC stub columns having active confinement were modeled using the ABAQUS software. The results obtained from the 3D model including the compressive strength at the initial peak point and failure point, as well as the axial and lateral stress-strain curves were compared with the experimental results to verify the accuracy of the 3D model. It was found that there existed a good agreement between them. A parametric study was conducted to investigate the effect of the concrete compressive strength, steel tube wall thickness, and pre-stressing level on the behavior of STCC columns with active confinement. The results indicated that increasing the concrete core's compressive strength leads to an increase in the compressive strength of the active composite column as well as its earlier failure. Furthermore, a reduction in the tube external diameter-to-wall thickness ratio affects the axial stress-strain curve and the confining pressure, while increasing the pre-stressing level has a negligible effect on the two.