• Title, Summary, Keyword: strength

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Strength and Modulus Relationship of Concrete for Rigid Pavement (포장용 콘크리트의 강도 및 탄성계수 상관관계식)

  • Yang, Sung-Chul;Park, Jong-Won
    • International Journal of Highway Engineering
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    • v.9 no.4
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    • pp.205-213
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    • 2007
  • Strength relationships are presented through experimental data from the concrete strength tests in this study. Various strength tests such as the compressive, flexural, and splitting tensile strength and the modulus of elasticity are included. An experimental work was performed to determine the various strength characteristics for various mix designs. Three different coarse aggregates such as granite, limestone, sandstone were used and included were fine aggregates such as natural sand, washed sand and crushed sand. Also included was cement amount as experimental variable. It was confirmed that each strength value with respect to curing time is to follow a typical strength development curve. With this somewhat reliable test results various strength relationships such as flexural strength-compressive strength, splitting tensile strength-compressive strength, modulus of elasticity-compressive strength, splitting tensile strength-flexural strength were analyzed through statistics. Experimental data were well fitted to the 0.5-power relationship of flexural strength and compressive strength which has been commonly accepted. The splitting tensile strength is expected to be best in the linear relationship from the flexural strength data. Finally splitting tensile strength was found to be proportional to the 0.87 power of the cylindrical compressive strength.

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Fire Resistance Studies on High Strength Steel Structures

  • Wang, Wei-Yong;Xia, Yue;Li, Guo-Qiang
    • International Journal of High-Rise Buildings
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    • v.7 no.4
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    • pp.287-298
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    • 2018
  • High strength steels have been widely applied in recent years due to high strength and good working performance. When subjected to fire conditions, the strength and elastic modulus of high strength steels deteriorate significantly and hence the load bearing capacity of structures reduces at elevated temperatures. The reduction factors of mechanical properties of high strength steels are quite different from mild steels. Therefore, the fire design methods deduced from mild steel structures are not applicable to high strength steel structures. In recent ten years, the first author of this paper has carried out a lot of fundamental research on fire behavior of high strength steels and structures. Summary of these research is presented in this paper, including mechanical properties of high strength steels at elevated temperature and after fire exposure, creep response of high strength steels at elevated temperature, residual stresses of welded high strength steel member after fire exposure, fire resistance of high strength steel columns, fire resistance of high strength steel beams, local buckling of high strength steel members, and residual strength of high strength steel columns after fire exposure. The results show that the mechanical properties of high strength steel in fire condition and the corresponding fire resistance of high strength steel structures are different from those of mild steel and structures, and the fire design methods recommended in current design codes are not applicable to high strength steel structures.

Influence of Concrete Strength and Lateral Ties on Behavior of High-Strength Concrete Columns (고강도 콘크리트 기둥의 거동에 미치는 콘크리트 강도와 띠철근의 영향)

  • Lee, Young-Ho;Chung, Heon-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.2
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    • pp.245-253
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    • 2002
  • This study was focused on the effect of concrete strength and lateral ties of concrete columns using high-strength concrete. Thirty-six concrete columns with 20cm square cross-section were tested. Experimental parameters included the concrete strength, the distribution of longitudinal bars and the volumetric ratio, yield strength, spacing of lateral ties. From the experiments, we found that: 1) the increasing rate of the strength and ductility of concrete columns caused by confinement of lateral ties was decreasing, as the concrete strength increased. 2) The high volumetric ratio and the reduction of tie spacing had a tendency to enhance the strength and improve the ductility. 3) The high-strength concrete columns required high volumetric ratio of lateral ties to maintain the proper strength and ductility. It was observed that the current AIK design code to specify the maximum tie spacing of high-strength concrete columns led to the poor strength and ductility for seismic design.

A Study on Seam Strength according to Sewing Speed (봉제속도에 따른 봉합강도에 관한 연구)

  • 김정진;장정대
    • Journal of the Korean Society of Clothing and Textiles
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    • v.23 no.7
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    • pp.998-1006
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    • 1999
  • This study has investigated the relation between the sewing speed and seam breaking strength applied perpendicular to the seam direction. Breaking strength efficiency breaking mode of seams were examined under various sewing conditions using three kinds of sewing threads and four kinds of fabrics. The results obtained are as follows : 1. According to the increase in sewing speed seam strength was remarkably decreased. Seam strength and its loss difference were shown variously as threads and fabrics were mixed. 2. In case of fabrics with higher strength seam strength showed higher. And the seam strength was determined by the loop strength. 3. In case of fabrics with lower strength seam strength and its difference for every sample showed lower. So the strength of fabrics dominated the seam strength than those of threads. 4. In the experiment using various fabrics and sewing threads there was a type of thread appropriate to each fabric. Fabrics and threads with have similar physical properties were shown proper seam efficiency. 5. The breaking mode was different for every sample seam that was tested.

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Concrete Strength Estimating at Early Ages by the Equivalent Age

  • Kim, Moo-Han;Nam, Jae-Hyun;Khil, Bae-Su
    • KCI Concrete Journal
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    • v.14 no.2
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    • pp.81-85
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    • 2002
  • The strength development of concrete is influenced by temperature and cement type which greatly affect hydration degree of cement. There is not pertinent concrete strength management method in korea. There are several methods for estimating the in-place strength of concrete. One such method is the maturity concept. The maturity concept is based on the fact that concrete gains strength gradually as a result of chemical reactions between cement and water; and for a specific concrete mixture, strength at any age and at normal conditions is related to the degree of hydration. The rate of hydration and, therefore, strength development of a given concrete will be a function of its temperature. Thus, strength of concrete depends on its time-temperature history. The goals of the present study are to investigate a relationship between strength of high-strength concrete and maturity that is expressed as a function of an integral of the curing period and temperature and predict strength of concrete.

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Direct strength method for high strength steel welded section columns

  • Choi, Jong Yoon;Kwon, Young Bong
    • Steel and Composite Structures
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    • v.29 no.4
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    • pp.509-526
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    • 2018
  • The direct strength method adopted by the AISI Standard and AS/NZS 4600 is an advanced design method meant to substitute the effective width method for the design of cold-formed steel structural members accounting for local instability of thin plate elements. It was proven that the design strength formula for the direct strength method could predict the ultimate strength of medium strength steel welded section compressive and flexural members with local buckling reasonably. This paper focuses on the modification of the direct strength formula for the application to high strength and high performance steel welded section columns which have the nominal yield stress higher than 460 MPa and undergo local buckling, overall buckling or their interaction. The resistance of high strength steel welded H and Box section columns calculated by the proposed direct strength formulae were validated by comparison with various compression test results, FE results, and predictions by existing specifications.

Strength Estimation of the High Strength Concrete by using Rock Test Hammer (암반용 테스트해머 사용에 의한 고강도콘크리트의 강도추정)

  • Seo, Yun-A;Nam, Kyung-Yong;Park, Soo-Hwa;Kim, Seong-Deok;Lim, Nam-Gi;Jung, Sang-Jin
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.77-79
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    • 2012
  • This paper intends to review possible application in the high strength area through compressive strength estimation of the simulated high strength concrete member using Rock Test Hammer and suggest it as a reference data for the strength estimation technique of the ultra high strength concrete in the future. From the results of our test, in the low strength area less than 15MPa and normal strength area in 15~60MPa, as shown on the existing studies, it is indicated that P Type Schmidt Hammer in the low strength area and N Type Schmidt Hammer in the normal strength area have high correlation of rebound-compressive strength. As the Rock Test Hammer indicated more or less reduced accuracy in the low strength area and the normal strength area but high correlation on the high strength area (50~100MPa) defined on this test, it is determined that it would be possible to make the fastest and simplest compressive strength estimation on the site where the high strength concrete is applied.

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Experimental behavior and shear bearing capacity calculation of RC columns with a vertical splitting failure

  • Wang, Peng;Shi, Qing X.;Wang, Qiu W.;Tao, Yi
    • Earthquakes and Structures
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    • v.9 no.6
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    • pp.1233-1250
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    • 2015
  • The behavior of reinforced concrete (RC) columns made from high strength materials was investigated experimentally. Six high-strength concrete specimen columns (1:4 scale), which included three with high-strength transverse reinforcing bars and three with normal-strength transverse reinforcement, were tested under double curvature bending load. The effects of yielding strength and ratio of transverse reinforcement on the cracking patterns, hysteretic response, shear strength, ductility, strength reduction, energy dissipation and strain of reinforcement were studied. The test results indicated that all specimens failed in splitting failure, and specimens with high-strength transverse reinforcement exhibited better seismic performance than those with normal-strength transverse reinforcement. It also demonstrated that the strength of high-strength lateral reinforcing bars was fully utilized at the ultimate displacements. Shear strength formula of short concrete columns, which experienced a splitting failure, was proposed based on the Chinese concrete code. To enhance the applicability of the model, it was corroborated with 47 short concrete columns selected from the literature available. The results indicated that, the proposed method can give better predictions of shear strength for short columns that experienced a splitting failure than other shear strength models of ACI 318 and Chinese concrete codes.

Influence of Steel Fiber Volume Ratios on Workability and Strength Characteristics of Steel Fiber Reinforced High-Strength Concrete (강섬유 혼입율이 강섬유보강 고강도 콘크리트의 작업성과 강도특성에 미치는 영향)

  • Kim, Yoon-Il;Lee, Yang-Keun;Kim, Myung-Sung
    • Journal of the Korea Institute of Building Construction
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    • v.8 no.3
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    • pp.75-83
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    • 2008
  • In this paper, concrete material tests were carried out to investigate influence of steel fiber volumn ratios on variations of workability and strength characteristics of steel fiber reinforced high-strength concrete, $50MPa{\sim}90MPa$ of compressive strength, according to increase of fiber volume. Test specimens were arranged with six levels of concrete compressive strength and fiber volumn ratios, 0.0%, 0.5%, 1.0%, 1.5%, 2.0%. The test results showed that steel fiber reinforced high-strength concrete($70MPa{\sim}90MPa$, 1.5% fiber volumn ratio) with good workability of slump 20cm could be used practically and effects of steel fiber reinforcement in improvement of concrete strength and toughness characteristics such as splitting tensile strength, flexural strength, and diagonal tensioned shear strength, were more distinguished in high-strength concrete than general strength concrete. And the test results indicated that splitting tensile strength of fiber reinforced concrete was proportioned to the product of steel fiber volumn ratios, $V_f(%)$ and sqare root of compressive strength, $\sqrt{f_{ck}}$, and the increasing rate was in contrast with that of flexural strength, and increase of diagonal tensioned shear strength was remarkable at steel fiber volumn ratio, 0.5%.

A Study on the Application of Non-Destructive Testing Equation for the Estimation of Compressive Strength of High Strength Concrete (고강도콘크리트의 압축강도 추정을 위한 비파괴시험식의 적용성에 관한 연구)

  • Kim, Moo-Han;Choi, Se-Jin;Kang, Suk-Pyo;Kim, Jae-Hwan;Jang, Jong-Ho
    • Journal of the Korea Institute of Building Construction
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    • v.2 no.3
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    • pp.123-130
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    • 2002
  • Recently, it is being studied on the high strength concrete in many laboratories and being applied to the construction field actually. But non-destruction testing equation that to be proposed about normal strength concrete in Japan has been using because the systematic study results for the estimation of compressive strength of high strength concrete do nit exist. So it is essential to suggest the non-destruction testing equation for the estimation of compressive strength of high strength concrete. This is an experimental study to analyze and investigate the non-destruction testing equation for the estimation of compressive strength of high strength concrete. The results are as follows; The relation between rebound number, pulse velocity and compressive strength of high strength concrete have lower coefficient than combined method of rebound number and pulse velocity. Also new non-destructive testing equation for the estimation on the compressive strength of high strength concrete was suggested in this study, and it is considered that these equations have possibility to be applied in domestic construction field.