• Title/Summary/Keyword: slab stiffness

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Effects of new construction technology on performance of ultralong steel sheet pile cofferdams under tidal action

  • Li, Ping;Sun, Xinfei;Chen, Junjun;Shi, Jiangwei
    • Geomechanics and Engineering
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    • v.27 no.6
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    • pp.561-571
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    • 2021
  • Cofferdams made of teel sheet piles are commonly utilized as support structures for excavation of sea-crossing bridge foundations. As cofferdams are often subject to tide variation, it is imperative to consider potential effects of tide on stability and serviceability of sheet piles, particularly, ultralong steel sheet piles (USSPs). In this study, a real USSP cofferdam constructed using new construction technology in Nanxi River was reported. The design of key parts of USSP cofferdam in the presence of tidal action was first introduced followed by the description of entire construction technology and associated monitoring results. Subsequently, a three-dimensional finite-element model corresponding to all construction steps was established to back-analyze measured deflection of USSPs. Finally, a series of parametric studies was carried out to investigate effects of tide level, soil parameters, support stiffness and construction sequence on lateral deflection of USSPs. Monitoring results indicate that the maximum deflection during construction occurred near the riverbed. In addition, measured stress of USSPs showed that stability of USSP cofferdam strengthened as construction stages proceeded. Moreover, the numerical back-analysis demonstrated that the USSP cofferdam fulfilled the safety requirements for construction under tidal action. The maximum deflection of USSPs subject to high tide was only 13.57 mm at a depth of -4 m. Sensitivity analyses results showed that the design of USSP cofferdam system must be further improved for construction in cohesionless soils. Furthermore, the 5th strut level before concreting played an indispensable role in controlling lateral deflection of USSPs. It was also observed that pumping out water before concreting base slab could greatly simplify and benefit construction program. On the other hand, the simplification in construction procedures could induce seepage inside the cofferdam, which additionally increased the deflection of USSPs by 10 mm on average.

Behaviour insights on damage-control composite beam-to-beam connections with replaceable elements

  • Xiuzhang He;Michael C.H. Yam;Ke Ke;Xuhong Zhou;Huanyang Zhang;Zi Gu
    • Steel and Composite Structures
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    • v.46 no.6
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    • pp.773-791
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    • 2023
  • Connections with damage concentrated to pre-selected components can enhance seismic resilience for moment resisting frames. These pre-selected components always yield early to dissipate energy, and their energy dissipation mechanisms vary from one to another, depending on their position in the connection, geometry configuration details, and mechanical characteristics. This paper presents behaviour insights on two types of beam-to-beam connections that the angles were designed as energy dissipation components, through the results of experimental study and finite element analysis. Firstly, an experimental programme was reviewed, and key responses concerning the working mechanism of the connections were presented, including strain distribution at the critical section, section force responses of essential components, and initial stiffness of test specimens. Subsequently, finite element models of three specimens were established to further interpret their behaviour and response that were not observable in the tests. The moment and shear force transfer paths of the composite connections were clarified through the test results and finite element analysis. It was observed that the bending moment is mainly resisted by axial forces from the components, and the dominant axial force is from the bottom angles; the shear force at the critical section is primarily taken by the slab and the components near the top flange. Lastly, based on the insights on the load transfer path of the composite connections, preliminary design recommendations are proposed. In particular, a resistance requirement, quantified by a moment capacity ratio, was placed on the connections. Design models and equations were also developed for predicting the yield moment resistance and the shear resistance of the connections. A flexible beam model was proposed to quantify the shear resistance of essential components.

Development of a Nondestructive Seismic Technique for Flexural Rigidity of Concrete Track as Slab Displacement Index (콘크리트 슬래브궤도의 휨강성 평가를 위한 비파괴 탄성파 기법의 개발)

  • Cho, Mi-Ra;Joh, Sung-Ho;Lee, Il-Wha
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.6D
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    • pp.905-913
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    • 2008
  • Recently, concrete tracks are introduced into high-speed railroads as an alternative to ballast tracks. Concrete tracks are superior to ballast tracks in the aspect of durability, maintenance and safety. However, deteriorated stiffness of railroad bed and settlement of soft ground induced by trapped or seepage water lead to problems in safety of train operation. In this research, flexural rigidity of concrete tracks was employed as an index of track displacement and a new seismic technique called FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) method was proposed to delineate flexural rigidity of concrete tracks in a 2-D image. In this paper, to establish theoretical background, parametric research was performed using numerical simulations of stress-wave tests at concrete tracks. Feasibility of the FRACTAL technique was proved at a real concrete track for Korean high-speed trains. Validity of the FRACTAL technique was also verified by comparing the results of impulse-response tests performed at the same measurement array and the results of DC resistivity survey performed at a shoulder nearby the track.

An Experimental Study on the Behavior of the Perforated Rib Connector with Shearing Bars (전단구속철근을 배치한 유공강판 전단연결재에 관한 실험적 연구)

  • Kim, Sung-Chil;Kim, Young-Ho;Yu, Sung-Kun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.6
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    • pp.175-182
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    • 2006
  • In the design of composite structures, shear connectors such as headed stud, channel, perforated plate, etc, are commonly used to transfer longitudinal shear forces across the steel-concrete interface. Many researches have been conducted to improve the characteristics of different types of shear connector. This paper presents the results of 11 push-out tests performed on the new perforated rib connectors with shearing bars embedded in concrete slab under static loads. The results obtained from these tests are as following : 1) The bearing plate welded on both sides of perforated rib plate improves the stiffness and strength. 2) The capacity of perforated connectors is influenced primarily by the transverse reinforcements and shearing bars.

Fatigue Durability of Cramp Joint at Precast Highway Deck Slabs (프리캐스트 바닥판용 클램프 조인트의 피로내구성)

  • Kim, Yoon Chil
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.156-162
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    • 2008
  • The fatigue durability test using the actual size beam was performed with a cramp joint in order to apply to the highway bridge deck slab. Three types of beam were investigated for durability performance by considering stress conditions in real bridge deck slabs, 1) A beam with major shear force applied at the joint (RC Type) 2) A beam with major bending moments applied at the joint (PSC Type) 3) A beam with the pure shear applied at the joint. The experiment for beams with cramp joints showed that the cramp joint had enough durability for fatigue regardless of the overlaid length of the looped distribution bars under the current design strength level. Moreover, it was clarified that the enough durability for fatigue under the load repetition was achieved by increasing the joint span grater than 1.5D with the consideration of the deformation due to reduction in joint stiffness.

A Study on FE Modeling Techniques of Steel Plate Girder Bridge with Composite Section for the Dynamic Analysis (동특성 분석을 위한 합성단면을 갖는 교량구조물의 FE 모델링 기법)

  • Heo, Gwang-Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.1
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    • pp.139-148
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    • 2006
  • The dynamic characteristics of a bridge deduced by using the modeling techniques depend on its stiffness and mass calculated from its geometric model. This research develops the FE modeling techniques for a steel plate girder bridge with composite section. and proves their validity by comparing the results with those from actual measurement. The FE modeling techniques are divided into two categories--a simplified one and two-dimensional model and a detailed three-dimensional model. In the meantime, the dynamic responses of the bridge tested for this research were measured by the ambient vibration some of accelerometers were been attached to its upper slab girder under normal traffic load. The Cross Power Spectrum obtained from the measurement was used to analyze the dynamic characteristics by natural excitation techniques. The analytic results are compared to those of each FE modeling, and thereby the modeling techniques were proved to be valid.

Influence of Column Aspect Ratio on the Hysteretic Behavior of Slab-Column Connection (슬래브-기둥 접합부의 이력거동에 대한 기둥 형상비의 영향)

  • Choi, Myung-Shin;Cho, In-Jung;Ahn, Jong-Mun;Shin, Sung-Woo
    • Journal of the Korea Concrete Institute
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    • v.19 no.4
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    • pp.515-525
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    • 2007
  • In this investigation, results of laboratory tests on four reinforced concrete flat plate interior connections with elongated rectangular column support which has been used widely in tall residential buildings are presented. The purpose of this study is to evaluate an effect of column aspect ratio (${\beta}_c={c_1}/{c_2}$=side length ratio of column section in the direction of lateral loading $(c_1)$ to the direction of perpendicular to $c_1$) on the hysteretic behavior under earthquake type loading. The aspect ratio of column section was taken as $0.5{\sim}3\;(c_1/c_2=1/2,\;1/1,\;2/1,\;3/1)$ and the column perimeter was held constant at 1200mm in order to achieve nominal vertical shear strength $(V_c)$ uniformly. Other design parameters such as flexural reinforcement ratio $(\rho)$ of the slab and concrete strength$(f_{ck})$ was kept constant as ${\rho}=1.0%$ and $f_{ck}=40MPa$, respectively. Gravity shear load $(V_g)$ was applied by 30 percent of nominal vertical shear strength $(0.3V_o)$ of the specimen. Experimental observations on punching failure pattern, peak lateral-load and story drift ratio at punching failure, stiffness degradation and energy dissipation in the hysteresis loop, and steel and concrete strain distributions near the column support were examined and discussed in accordance with different column aspect ratio. Eccentric shear stress model of ACI 318-05 was evaluated with experimental results. A fraction of transferring moment by shear and flexure in the design code was analyzed based on the test results.

A study on experiment from the Stair Joints Constructed with PC system part of it using the HI-FORM DECK (HI-FORM DECK를 이용한 부분 PC 계단 접합부의 접합방식에 따른 실험적 연구)

  • Chang, Kug-Kwan;Lee, Eun-Jin;Jin, Byung-Chang;Kang, Woo-Joo;Han, Tae-Kyung
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.9-12
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    • 2008
  • The semi-rigid joint is the shape of middle that can supplement the defect of pin joints and accept the good point of rigid joints. Recently, a study on the pin joints is activated in the country, but because the study on semi-rigid joints is not many, this study tried to prove with producing test model of three shape. The test models are rigid joint HI-R, semi-rigid joint HI-S, pin joint HI-P. As a result of the test, respectively HI-R, HI-S, HI-P appeared shear failure of joint, flexure failure of the top fixing, flexure failure of the lower part slipping stair slab, and the maximum strength is measured to 51.74, 51.4, 24.63kN, the stiffness is appeared 1.58, 1.19, 0.37 respectively, The yield strength is respectively kept 44.5, 47.3, 24kN, and ductility ratio is appeared to 3.31, 2.32, 1.54, when is based on KBC code, sag of the acting service load is appeared that HI-P model is over the standard. When is based on distribution of bars strain ratio, HI-S seems similar behavior incipiently, but after the yield, the semi-rigid joint was able to be judged better than pin joint because of the stress allotment of joint internal elements.

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Test on the Structural Performance of the TOX Deck plate - Evaluation of Structural Safety during Construction Stage - (무용접 압접 데크플레이트의 구조성능에 관한 실험 - 시공단계에서의 구조안전성 평가 -)

  • Oh, Sang Hoon;Kim, Young Ju;Yoon, Myung Ho
    • Journal of Korean Society of Steel Construction
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    • v.20 no.6
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    • pp.701-709
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    • 2008
  • Owing to the decreased work term and the convenience of construction work in Korea, the steel deck plate system has been widely used in the construction field. Most of all, due to its good stiffness and economic consideration, the steel-wire-integrated deck plate system (or truss deck plate system) has become very popular in recent years. But although it has many advantages, the truss deck plate system has a critical defect: it gets rusty in the welding joints between the lattice steel wire and the deck plate, resulting in the cracking of such welding joints and water leakage. To address these problems, a new type of truss deck plate system, which need not be welded and does not rust, was proposed herein: the TOX deck plate system. In this study, tests were conducted on 15 specimens to evaluate the structural safety of the proposed deck plate system during the construction stage. The test parameters were as follows: the depth of the slab the length of the span the diameters of the top, bottom, and lattice steel wire and the material properties of the zinc-coated steel sheets. The test results show that the TOX deck plate system can guarantee structural safety owing to its deflection and strength.

Flexural Behavior and Design of Concrete-filled U-shape Hybrid Composite Beams Fabricated from 570MPa High-strength Steel (570MPa급 고강도강을 적용한 콘크리트 채움 U형 하이브리드 합성보의 휨거동 및 설계)

  • Lee, Cheol Ho;So, Hyun Joon;Park, Chang Hee;Lee, Chang Nam;Lee, Seung Hwan;Oh, Ha Nool
    • Journal of Korean Society of Steel Construction
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    • v.28 no.2
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    • pp.109-120
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    • 2016
  • Flexural tests of full-scale concrete-filled U-shape hybrid composite beams were conducted. Ordinary (SS400) and high-strength (SM570) steel plates were used in the web and in the bottom flange of U-shape steel section respectively. The primary objectives were to develop the hybrid section configuration with maximized flexural capacity and to investigate its flexural strength and deformation capacity. All the hybrid test specimens in this study exhibited the plastic moment capacity and resonable deformability. It is shown that the plastic stress distribution can be assumed in calculating the flexural strength of the proposed hybrid composite beams if the plastic neural axis is located within 15% of the total beam depth from the top of the composite slab. The procedure for computing the effective flexural stiffness of hybrid composite beams is also recommended based on test results.