• Title/Summary/Keyword: Strength Method

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Evaluation Technique of Concrete Strength Using Impact-Resonance and Combined Method (충격공진법 및 복합법을 이용한 콘크리트의 강도 평가 기법)

  • 이광명;이회근;김동수;김지상
    • Journal of the Korea Concrete Institute
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    • v.11 no.4
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    • pp.157-167
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    • 1999
  • Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

A Study on the Quality Control of 80MPa UHPC according to the Measurement Method of Compressive Strength (압축강도 측정방법에 따른 80MPa급 UHPC의 품질관리에 관한 연구)

  • Koo, Hyun-Chul;Moo, Ji-Hun;Lee, Hak-ju;Park, Min-Sang;Choi, Sung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2019.05a
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    • pp.176-177
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    • 2019
  • Recently, efforts are made to apply 200MPa levels of ultra-high strength concrete to structures exceeding 40MPa.. Ultra-high strength concrete has been steadily researched in Korea as well as abroad, and now it is equipped with 200MPa ultra-high strength concrete mixing technology. Because ultra-high strength concrete has a higher range of compressive strength than ordinary concrete, it is difficult to accurately measure the compressive strength of UHPC concrete with existing compressive strength measuring equipment and can be less reliable. In this study, the compressive strength of the SC80 was measured according to the test method to compare the compressive strength of the SC80 by applying various methods of measurement of compressive strength. The compressive strength test method measured the compressive strength according to the size of the specimen, the grinding method, and the capacity of the UTM equipment.

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Ultimate Strength of Composite Beams with Unreinforced Web Opening (유공 합성보의 극한강도식의 제안)

  • 김창호;박종원;김희구
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.369-374
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    • 1999
  • A practical approach of calculating the ultimate strength of composite beams with unreinforced web opening is proposed. In this method, the slab shear contribution at the opening is calculated as the smaller of the shear strength of the slab and the pullout capacity of the shear connectors at the high moment end. A simple interaction equation is used to predict the ultimate strength under simultaneous bending moment and shear force. Strength prediction by the proposed method is compared with previous test results and the predictions by other analytical method. The comparison shows that the proposed method predicts the ultimate capacity with resonable accuracy.

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A Study Using Nondestructive Tests Based on Stress Waves for the Estimation of Concrete Compressive Strength (응력파 기반 비파괴 검사법에 의한 콘크리트 강도 추정에 관한 연구)

  • Joo, Hyun-Jee;Cho, Young-Sang
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.675-678
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    • 2004
  • The importance of predicting concrete compressive strength of in concrete structures is gradually increasing in construction industry. The estimation of concrete compressive strength of is a critical factor of the construction schedule and quality control. This study was performed to examine the relationship between concrete compressive strength and stress wave velocity which was determined by the impact echo method and SASW method.

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A Study on the Investigation of Application in Construction Field of Strength Prediction Model using Maturity Method (적산온도를 활용한 강도예측모델의 건설생산현장 적용성 검토에 관한 연구)

  • 주지현;장종호;김재환;길배수;남재현;김무한
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2004.05a
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    • pp.101-104
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    • 2004
  • If predicting of compressive strength of construction in construction field at early age is possibile, rational strength management & schedule plan is possible. With method for predicting strength of concrete, many researchers have been making study of maturity method. On the other hand, nowadays rationalization of construction capacity and reduction of a term of works due to improvement of construction capacity and application of a new method of construction is gathering strength with important issue. In accordance with this present condition, construction is being progressed in winter, but proper construction mothed and countermeasure for strength management is not established in case of winter construction. Therefore to investigate application in construction field at winter of strength prediction model that developed at former study, this study aim to measure application of developed strength prediction model through manufacture of mock-up concrete according to kind of strength level at 5$^{\circ}C$.

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Shear Strength and Seismic Behavior of the Composite Shear Wall with the Steel Plate Embedded in the RC Wall (철판삽입 합성전단벽의 전단강도와 내진거동)

  • Chun, Young-Soo;Park, Ji-Young;Lee, Jong-Yoon
    • Land and Housing Review
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    • v.8 no.3
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    • pp.211-221
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    • 2017
  • This study proposed hybrid coupled shear wall in the steel plate insertion method, which is capable of reinforcing the shear strength of the entire wall without increasing wall thickness in the wall-slab apartment buildings. The proposed hybrid coupled shear wall was tested for its effectiveness, shear strength and seismic behavior in experiment. As a test result, the shear strength improvement by the proposed hybrid coupled shear was found effective. Integral-type of steel plate insertion was found more effective than separate-type steel plate insertion. In this case, if the stud enforcement method proposed in this study was used, the shear strength of hybrid coupled shear wall was recommended to calculate using the KBC2016 0709.4.1(3) method. The steel plate inserted in the proposed method was found to have no significant impact on the final fracture behavior and bending strength of hybrid coupled shear wall. The shear strength at the final destruction of the wall was merely about 1/50 of the entire design shear strength. Thus, it is deemed that the wall was over excessively designed regarding the shear force in the existing design method. This finding indicates further study on wall designing to ensure effective and economic designing based on appropriate strength estimation under the destruction mechanism.

Concrete Strength Prediction System by Maturity Method using RFID (RFID를 활용한 적산온도방식의 콘크리트 강도 추정 시스템 기초 연구)

  • Park, So-Hyun;Oh, Yong-Seok;Song, Jeong-Hwa;Oh, Kun-Soo
    • Proceeding of Spring/Autumn Annual Conference of KHA
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    • 2008.04a
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    • pp.399-404
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    • 2008
  • The objective of this study is to develop the predicting method of concrete strength when remove concrete form-work without making cement test piece at construction site. For this purpose, this study catches the Maturity Method by using RFID, the usability of which is now being emphasized at site, accumulates and record the strength data, which can be gained with the results of existing Maturity Method method that is accompanied with strength estimation study, in database, and finally proposes the system structure which can check the estimated strength by Maturity Method. The merits of this method by using of Maturity Method are as follows; More objective, precise, and rapid decision can be made to the concrete strength and about the maintaining period of concrete form and form support. More efficient control of integrated material management system can be possible. Architectural field example using RFID can be suggested more concretely. RFID applicability can be extended by using DB of material integration management system.

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An Experimental Study on the Compressive Strength of Reinforcing Bars in Concrete Specimens and Compressive Strength Measurement Methods (콘크리트 압축강도 측정법과 공시체 내 철근이 압축강도 측정에 미치는 실험적 연구)

  • Lee, Won-Hong;Choi, Sang-Gi;Lee, Seuong-Yeol;Ahn, Jin-Hee;Kang, Beom-Ju
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.33-40
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    • 2021
  • Measuring the compressive strength of concrete is a very important factor in the safety review of concrete structures. Concrete compressive strength measurement methods include destructive and non-destructive methods. The destructive method includes the uniaxial compression failure method, and the non-destructive method includes the rebound hardness method and the elastic wave measurement method. In this study, the type of measurement method and the effect of reinforcing bars inside the concrete were tested to examine the relationship between them. Regardless of the type of specimen, the average compressive strength by the elastic wave measurement method among the three experimental methods was greater than the average compressive strength by the other methods. When the specimen type is the same, the standard deviation of the measured values of the elastic wave measurement method is smaller than that of the other measurement methods, so it can be seen that the elastic wave measurement method does not show large variance in the measured values compared to the other two measurement methods. When the average compressive strength according to the test method for each specimen was compared with the average compressive strength of the compressive failure test method, the average compressive strength was measured to be high in the order of the elastic wave measurement method, the compression failure test, and the rebound hardness method. Since the measured values of the compressive strength of concrete are different depending on the method of measuring the compressive strength of concrete and the presence or absence of reinforcing bars inside the concrete, further research is required considering the effect of various concrete covers.

A Study on the Curing Method to Improve Bonding Strength of Aluminum/CFRP Composites (알루미늄/CFRP 복합재의 접착강도 향상을 위한 경화방법에 관한 연구)

  • 이경엽;양준호;최낙삼
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.3
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    • pp.130-135
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    • 2002
  • This study investigates the effect of curing method on the bonding strength of aluminum/CFRP composites. The surface of aluminum panel was treated by DC plasma. Lap shear tests and T-peel tests were performed based on the procedure of ASTM 906-94a and ASTMD1876-95, respectively. Test samples were fabricated by using the co-curing method and the secondary curing method. The results showed that the shear strength of test samples made by the co-curing method was 2.5 times greater than that of test samples made by the secondary curing method. The T-peel strength of the co-curing method case was almost 2 times greater than that of the secondary curing method case.

On the direct strength and effective yield strength method design of medium and high strength steel welded square section columns with slender plate elements

  • Shen, Hong-Xia
    • Steel and Composite Structures
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    • v.17 no.4
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    • pp.497-516
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    • 2014
  • The ultimate carrying capacity of axially loaded welded square box section members made of medium and high strength steels (nominal yield stresses varying from 345 MPa to 460 MPa), with large width-to-thickness ratios ranging from 35 to 70, is analyzed by finite element method (FEM). At the same time, the numerical results are compared with the predicted results using Direct Strength Method (DSM), modified DSM and Effective Yield Strength Method (EYSM). It shows that curve a, rather than curve b recommended in Code for design of steel structures GB50017-2003, should be used to check the local-overall interaction buckling strength of welded square section columns fabricated from medium and high strength steels when using DSM, modified DSM and EYSM. Despite all this, EYSM is conservative. Compared to EYSM and modified DSM, DSM provides a better prediction of the ultimate capacities of welded square box compression members with large width-thickness ratios over a wide range of width-thickness ratios, slenderness ratios and steel grades. However, for high strength steels (nominal yield strength greater than 460 MPa), the numerical and existent experimental results indicate that DSM overestimates the load-carrying capacities of the columns with width-thickness ratio smaller than 45 and slenderness ratio less than 80. Further, for the purpose of making it suitable for a wider scope, DSM has been modified (called proposed modified DSM). The proposed modified DSM is in excellent agreement with the numerical and existing experimental results.