• Title/Summary/Keyword: construction Joints

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Damage and deformation of new precast concrete shear wall with plastic damage relocation

  • Dayang Wang;Qihao Han;Shenchun Xu;Zhigang Zheng;Quantian Luo;Jihua Mao
    • Steel and Composite Structures
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    • v.48 no.4
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    • pp.385-403
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    • 2023
  • To avoid premature damage to the connection joints of a conventional precast concrete shear wall, a new precast concrete shear wall system (NPSW) based on a plastic damage relocation design concept was proposed. Five specimens, including one monolithic cast-in-place concrete shear wall (MSW) as a reference and four NPSWs with different connection details (TNPSW, INPSW, HNPSW, and TNPSW-N), were designed and tested by lateral low-cyclic loading. To accurately assess the damage relocation effect and quantify the damage and deformation, digital image correlation (DIC) and conventional data acquisition methods were used in the experimental program. The concrete cracking development, crack area ratio, maximum residual crack width, curvature of the wall panel, lateral displacement, and deformed shapes of the specimens were investigated. The results showed that the plastic damage relocation design concept was effective; the initial cracking occurred at the bottom of the precast shear wall panel (middle section) of the proposed NPSWs. The test results indicated that the crack area ratio and the maximum residual crack width of the NPSWs were less than those of the MSW. The NPSWs were deformed continuously; significant distortions did not occur in their connection regions, demonstrating the merits of the proposed NPSWs. The curvatures of the middle sections of the NPSWs were lower than that of the MSW after a drift ratio of 0.5%. Among the NPSWs, HNPSW demonstrated the best performance, as its crack area ratio, concrete damage, and maximum residual crack width were the lowest.

Effect of Vibratory Injection on Grout Permeation Characteristics (진동주입이 그라우트재의 침투 특성에 미치는 영향 연구)

  • Lee, Mun-Seon;Kim, Jong-Sun;Lee, Sung-Dong;Choi, Young-Joon;Yang, Jae-Man;Lee, In-Mo
    • Journal of the Korean Geotechnical Society
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    • v.26 no.7
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    • pp.37-47
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    • 2010
  • To improve the grout penetration characteristics, a vibratory grout injection technique was adopted in this study. It is a technique of grout injection in which an oscillating pressure is added to the steady-state pressure as an injection pressure. By applying the vibration during grout injection, cement particles will become less adhesive and the clogging tendency will be decreased. A series of pilot-scale chamber tests were performed to verify the enhancement of the groutability by applying the vibratory grout injection; assessment on the change of the lumped parameter $\theta$ which represents a barometer of clogging phenomenon was made. Moreover, the effect of vibratory grout injection through the joint was also investigated using artificially made rock joints. Experimental results as well as analytical results show that the grout penetration depth can be substantially improved by vibratory grouting. Moreover, it was found that enhancement of the permeation grouting due to vibratory injection is more dominant at grouting pressure less than 400 kPa.

A Study on the Seismic Reinforcement of a Low-Rise Building Using Sinusoidal Corrugated Web Members (사인파형 웨브주름 보강재를 이용한 저층건물의 내진보강에 관한 연구)

  • Jung, Dong Jo;Kim, Jin
    • Journal of the Korean Institute of Rural Architecture
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    • v.24 no.2
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    • pp.13-20
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    • 2022
  • In this study, a general low-rise building was selected to compare the new shear wall reinforcement method, which is a general method among the existing reinforcement methods, and the reinforcement method using sinusoidal corrugated web reinforcement. And it was confirmed that the following effects can be expected. Sinusoidal corrugated web members can be carried out in a short period of time as it does not require the removal of the masonry filling wall, the reinforcement of reinforcing bars, and the curing period of the concrete. It is effective in preventing damage that may occur when masonry filling wall is overturned in the out-of-plane direction, and the burden of the foundation is also reduced, and thus the construction period and cost required for reinforcement can greatly be reduced. By adjusting the number of sinusoidal corrugated web member, details of joints, and reinforcement positions, the flow of load can be induced to have an advantageous effect on the building. It can be considered as the most suitable reinforcement plan in terms of life safety. Unlike the shear wall that fills between the columns, the sinusoidal corrugated web members, which has a width of 1.5m, can install openings between two columns depending on the purpose of use, and can be expected to have a great effect in terms of usability due to its free installation location. As mentioned above, the seismic reinforcement using a sinusoidal corrugated web members, can expect great effect compared to conventional reinforcement methods in terms of usability, economic feasibility, and stability.

Fundamental Study on the Design of Steel Tube Structures Based on the Qualitative Analysis (복합강구조물 설계에 정성분석기법을 적용하기 위한 기초연구)

  • Kang, Hyun-Sik;Lim, Seo-Hyung;Park, Yong-Gul
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.1
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    • pp.149-156
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    • 2006
  • Steel hollow section members have been widely used as a major material in the construction market due largely to their efficiency, their aesthetic appeal and to the technical development. But it is true that the commercial Program for dealing with a joint problem using hollow section members is not firmly established due to its uncertain and variable design parameters. The qualitative analysis program developed by using computer is introduced in this study. The results of that analysis are shown in the two-dimensional space in variable ranges and diagrams, so it would be useful to whom have not many experiences and knowledges. It is represented that the differences between Canadian code and the Korean standard for the connections of hollow section members. And It is verified that the software is applicable to the Preliminary design in steel tubular structures.

An Experimental Study on the Structural Characteristics of Tension Joints with High-Strength Bolted Split-Tee Connection (고력볼트 스플릿-티 인장접합부의 구조성능에 관한 실험적 연구)

  • Choi, Sung Mo;Lee, Seong Hui;Kim, Jin Ho
    • Journal of Korean Society of Steel Construction
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    • v.16 no.6 s.73
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    • pp.737-745
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    • 2004
  • In general, most of the beam-to-column connections for steel structures are regarded as either rigid connections or pin connections. Recently, the concept of a semi-rigid connection was introduced for a correct analysis of steel structures. Several experimental and theoretical researches have been performed regarding the structural behaviors of frames and buildings with semi-rigid connections. The results are not well known, and structural frame/building has not been designed to introduce the concept of semi-rigid connections between a beam and column until this time. To resolve this, this research depends on design specifications prepared by other advanced countries for the design of buildings with semi-rigid connections. Such a specification, however, should incorporate domestic characteristics of steel material properties and load conditions. This paper deals with structural capacities and deformable behaviors for a split-T tensile connection with F10T high-strength bolts to investigate the structural characteristics of semi-rigid frames. The experimental parameters include the thickness of T-flanges, painted or not, preloaded or not, and load pushover pattern. A total of 20 specimens were fabricated and tested with a 300-ton UTM. The structural capacities and behavior for split-T tensile connections were evaluated on each research parameter.

Seismic Performance of Precast Infill Walls with Strain-Hardening Cementitious Composites (변형경화형 시멘트 복합체를 사용한 프리캐스트 끼움벽의 내진성능)

  • Kim, Sun-Woo;Yun, Hyun-Do;Jang, Gwang-Soo;Yun, Yeo-Jin
    • Journal of the Korea Concrete Institute
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    • v.21 no.3
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    • pp.327-335
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    • 2009
  • In the seismic region, non-ductile structures often form soft story and exhibit brittle collapse. However, structure demolition and new structure construction strategies have serious problems, as construction waste, environmental pollution and popular complain. And these methods can be uneconomical. Therefore, to satisfy seismic performance, so many seismic retrofit methods have been investigated. There are some retrofit methods as infill walls, steel brace, continuous walls, buttress, wing walls, jacketing of column or beam. Among them, the infilled frames exhibit complex behavior as follows: flexible frames experiment large deflection and rotations at the joints, and infilled shear walls fail mainly in shear at relatively small displacements. Therefore, the combined action of the composite system differs significantly from that of the frame or wall alone. Purpose of research is evaluation on the seismic performance of infill walls, and improvement concept of this paper is use of SHCCs (strain-hardening cementitious composites) to absorb damage energy effectively. The experimental investigation consisted of cyclic loading tests on 1/3-scale models of infill walls. The experimental results, as expected, show that the multiple crack pattern, strength, and energy dissipation capacity are superior for SHCC infill wall due to bridging of fibers and stress redistribution in cement matrix.

Proposal of Estimation Equation for Nominal Strength of Longitudinal Fillet Welds with Different Types of Steel (강종에 따른 종방향 필릿용접부 공칭강도 계산식의 제안)

  • Jo, Jae-Byung;Lee, Hye-Youn
    • Journal of Korean Society of Steel Construction
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    • v.24 no.5
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    • pp.503-510
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    • 2012
  • High performance, high strength steels were developed and used in steel structures recently. Since the newly developed high strength steels posses different toughness, weldability, yield strength ratio, etc. in compare with conventional structural steels, it is requred to investigate the applicability of the design strength of fillet weld specified in the existing design codes. The comparison of the design strengths of various codes from domestic and overseas shows quite a difference. Test results for fillet weld strengths were collected and statistically analysed. Each of yield strength, tensile strength of parent material and tensile strength of weld metal was selected as a main parameter for each estimation equation respectively. All the estimation equations yield almost same values for each type of steel regardless the type of main parameter selected. Considering the behaviour of fillet welded joints and for practical purposes, it is proposed that the equation with tensile strength of parent material is to be used in design codes. The comparison with the proposed nominal strengths of fillet welds shows that the existing design codes could lead to an uneconomical result for low strength steels and lie on an unsafe side for high strength steels.

Cyclic Loading Tests of Concrete-Filled Composite Beam-Column Connections with Hybrid Moment Connections (복합모멘트접합을 갖는 콘크리트 충전 보-기둥 합성접합부의 반복하중 실험)

  • Lim, Jong Jin;Kim, Dong Gwan;Lee, Sang Hyun;Lee, Chang Nam;Eom, Tae Sung
    • Journal of Korean Society of Steel Construction
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    • v.28 no.5
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    • pp.345-354
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    • 2016
  • In the present study, hybrid moment connections of welding and bar reinforcement for composite beam-column connections were proposed. Concrete-filled octagonal tube and U-section were used for the column and beam, respectively. In the beam-column connection, the top flange and web of the beam U-section were connected to the column plate by welding. However, to reduce stress concentration at the weld joints, the bottom flange of the beam was not welded to the column plate. Instead, to transfer the tension force of the beam flange, reinforcing bars passing through the column plate were used. Four exterior connections with conventional welded and hybrid moment connections were tested under cyclic loading and their cyclic behaviors were investigated. The test results showed that the hybrid moment connections successfully transferred the beam moment to the column. The strength and ductility of the hybrid moment connections were comparable to the conventional welded moment connection with exterior diaphragm; however, the connection performance was significantly affected by the details of the hybrid moment connection.

Case Study on the Causes for the Failure of Large Scale Rock Mass Slope Composed of Metasedimentary Rocks (변성퇴적암류로 구성된 대규모 암반사면의 붕괴원인 분석에 관한 사례 연구)

  • Park, Boo-Seong;Jo, Hyun;Cha, Seung-Hun;Lee, Ki-Hwan
    • Tunnel and Underground Space
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    • v.16 no.6 s.65
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    • pp.506-525
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    • 2006
  • For the design of large scale rock slope which has complex formations and geological structures, generally, insufficiency of geotechnical investigations and laboratory tests are the main factors of slope failures doling construction. In such case, remedial measures to stabilize slope should be selected and applied through reliable investigations and analysis considering the geotechnical characteristics. The rock slope of this study, one of the largest cut slopes in Korea with a length of 520.0 m and maximum height of 122.0 m consists of metasedimentary rocks. And a case study on the causes of large-scale rock slope failure was carried out by analysis of landslides history and site investigations during construction. When the slope with the original design slope of 0.7: 1.0 (H:V) was partially constructed, the slope failure was occurred due to the factors such as poor conditions of rocks (weathered zone, coaly shale and fault shear zone), various discontinuities (joints, foliations and faults), severe rain storm and so on. The types of failures were rockfall, circular failure, wedge failure and the combination of these types. So, the design of slope was changed three times to ensure long-term slope stability. This paper is intended to be a useful reference for analyzing and estimating the stability of rock slopes whose site conditions are similar to those of this study site such as geological structures and geotechnical properties.

Comparison of Behavior of Connections between Modular Units according to Shape of Connector Plates (연결 강판 형상에 따른 모듈러 유닛 간 접합부의 거동 비교)

  • Lee, Sang Sup;Bae, Kyu Woong;Park, Keum Sung
    • Journal of Korean Society of Steel Construction
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    • v.28 no.6
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    • pp.467-476
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    • 2016
  • For the connections between modular units in modular buildings, the bolted joints with connector plates are used commonly. The strength of structure is determined by the weakest part of structure and the connections may be weaker than the members being joined. Therefore, to check the safety of modular building, the structural performance of connections between modular units as well as that of beam-to-column connections should be evaluated. In this study, the behavior of module to module connection with straight and cross shaped connector plates is investigated by lateral cyclic tests according to KBC2009 0722.2.4 which shall be conducted by controlling the story drift angle in the width and the longitudinal direction respectively. All of test results generally show the stable ductile behavior up to 0.04rad drift levels and the tests in longitudinal direction show a superior energy dissipation per cycle in each of the load steps. However, the straight shaped connector plates have the degradation of stiffness with cyclic loading and the larger drift angle of column than the cross shaped connector plates.