• Steel and Composite Structures
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• 제39권5호
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• pp.583-598
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• 2021

The composite steel reinforced concrete (SRC) columns have been widely used in Structural Engineering due to their good performances. Many studies have been done on the SRC columns' performances, but they focused on the ordinary types with conventional configurations and materials. In this study, nine new types of steel reinforced lightweight aggregate concrete (SRLAC) short columns with cross-shaped (+shaped and X-shaped) steel section were tested under monotonically axial compressive load; the studied parameters included steel section ratio, steel section configuration, ties spacing, lightweight aggregate concrete (LWAC) strength, and longitudinal bars ratio. From the results, it could be found that the specimens with larger ties ratio, concrete strength, longitudinal bars ratio, and steel section ratio achieved great strength and stiffness due to the excellent interaction between the concrete and steel. The well-confined concrete core could strengthen the steel section. The ductility and toughness of the specimens were influenced by the LWAC strength, steel section ratio, and longitudinal bars ratio; in addition, larger ties ratio with smaller LWAC strength led to better ductility and toughness. The load transfer between concrete and steel section largely depends on the LWAC strength, and the ultimate strength of the new types of SRLAC short columns could be approximately predicted, referring to the codes' formulas of ordinary types of steel reinforced concrete (SRC) columns. Among the used codes, the BS-5400-05 led to the most conservative results.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.233-242
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• 2002

This study is to investigate experimentally the shear capacity of high-strength lightweight-aggregate reinforced concrete beams subjected to monotonic loading. Ten beams made of fly-ash artificial lightweight high-strength concrete were tested to determine their diagonal cracking and ultimate shear capacities. The variables in the test program were longitudinal reinforcement ratio; which variabled (between 0.83 and 1.66 percent), shear span-to-depth ratio (a/d=1.5, 2.5 and 3.5), and web reinforcement(0, 0.137, 0.275 and 0.554 percent). Six of the test beams had no web reinforcement and the other six had web reinforcement along the entire length of the beam. Most of beams failed brittly by distinct diagonal shear crack, and have reserved shear strength due to the lack of additional resisting effect by aggregate interlocking action after diagonal cracking. Test results indicate that the ACI Building Code predictions of Eq. (11-3) and (11-5) for lightweight concretes are unconservative for beams with tensile steel ratio of 1.66, a/d ratios greater than 2.5 without web reinforcement. Through a more rational approach to compute the contribution of concrete to the shear capacity, a postcracking shear strength in concrete is observed.

• 한국구조물진단유지관리공학회 논문집
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• 제3권2호
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• pp.155-160
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• 1999

Recently, the study on mix design of lightweight concrete using the polystyrene foam balls is put into practice from the viewpoint to grade up the quality of concrete and recyclable usage of industrial by products. Polystyrene aggregate concrete, PAC, can be used as structural concrete in low strength application. For instance, PAC could be used in the middle part of sandwich panel where stresses are generally low and in the case of grid-type reinforcement where it does not need high bond strength but little compressive strength to resist the pressure of transverse reinforcement. From this point of view, the authors discussed the influence of fluidity and compressive strength of concrete by the difference of the volume percentage of polystyrene foam balls and water cement ratio.

• Structural Engineering and Mechanics
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• 제88권2호
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• pp.169-178
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• 2023

Lightweight aggregate concrete (LWAC) has various advantages, but it has limitations in ensuring sufficient ductility as structural members such as reinforced concrete (RC) columns due to its low confinement effect of core concrete. In particular, the confinement effect significantly decreases as the axial load increases, but studies on evaluating the ductility of RC columns at high axial loads are very limited. Therefore, this study examined the effects of concrete unit weight on the seismic performance of RC columns subjected to constant axial loads applied with different values for each specimen. The column specimens were classified into all-lightweight aggregate concrete (ALWAC), sand-lightweight aggregate concrete (SLWAC), and normal-weight concrete (NWC). The amount of transverse reinforcement was specified for all the columns to satisfy twice the minimum amount specified in the ACI 318-19 provision. Test results showed that the normalized moment capacity of the columns decreased slightly with the concrete unit weight, whereas the moment capacity of LWAC columns could be conservatively estimated based on the procedure stipulated in ACI 318-19 using an equivalent rectangular stress block. Additionally, by applying the section lamina method, the axial load level corresponding to the balanced failure decreased with the concrete unit weight. The ductility of the columns also decreased with the concrete unit weight, indicating a higher level of decline under a higher axial load level. Thus, the LWAC columns required more transverse reinforcement than their counterpart NWC columns to achieve the same ductility level. Ultimately, in order to achieve high ductility in LWAC columns subjected to an axial load of 0.5, it is recommended to design the transverse reinforcement with twice the minimum amount specified in the ACI 318-19 provision.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.425-428
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• 2008

최근 국내에서도 경량콘크리트에 대한 필요성이 점차 증가하고 있으나 아직 비구조용으로 국한되어 사용되어지고 있으며 구조용으로써 사용에 대한 방안이 필요하다. 또한 경량골재콘크리트와 관련한 다양한 연구가 수행되고 있으나 내구적 특성 분석을 통한 장기안정성 검토를 실시한 예는 매우 부족한 실정이므로 다양한 내구특성 실험을 통한 구조용 경량골재콘크리트의 내구성능평가를 실시하여 그 적용성을 검증하는 연구는 매우 시급하다고 할 수 있다. 따라서 본 연구에서는 경량골재콘크리트의 적극적인 활용을 위하여 경량골재 콘크리트의 기초 역학적 성능을 평가하고, 이에 대한 건조수축 및 크리프에 대한 시험을 실시하여 내구특성의 영향요인을 분석하고자 고강도 에코인공경량골재콘크리트의 물성으로 슬럼프플로 500${\pm}$50mm, 공기량 2.0${\pm}$1.0%로 하였으며, 물결합재비는 35, 39% 두 수준으로 하였으며 기본 물성 시험과 압축강도 시험을 실시하고 건조 수축 및 압축 크리프 실험을 실시하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.124-127
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• 2003

Sewage sludge and clay used as raw materials in the study. Green aggregates contain different contents by dried weight of the sewage sludge, up to 80 percent is manufactured and burning conditions of soak temperature, soak time and rate of temperature increase. influence of burning condition and mixing ratio on specific gravity of burned aggregate are discussed. The appropriate burning condition to all aggregates is evaluated. Aggregates result form the thermal treatment get specific gravity under 0.8, water absorption fewer than 7.5 percent, and aggregate crushing value from 28 to 53. As the result, aggregates can be available as the lightweight aggregate for non-structural concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.775-780
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• 2002

Sandwich panel made by foamed styrene and ployuretane has been used generally in the construction area because of the high thermal conductivity and light weight but they occur harmful gases to both bodies and environments in the high temperature over $50^{\circ}C$. So, the purpose of this study is to investigate the physical properties of light-weight panel using the non-structural lightweight aggregate as a part of the substitution of foamed styrene and ployuretane. This paper dealt with the effect of the addition of polymer dispersion such as SBR, St/BA-1 and St/BA-2 having polymer-cement ratio as 5, 10, 15% and the filling ratio of continuous void as 50, 60% on the strength of polymer-modified sandwich panel core. From the results, we could know that the compressive and flexural strength of the sandwich panel core using non-structural lightweight aggregate and polymer dispersion such as SBR, St/BA-1 and St/BA-2 tended to be increased with an increase in the polymer-cement ratio and the filling ratio of continuous void.

• 한국건축시공학회지
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• 제18권2호
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• pp.133-140
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• 2018

이 연구의 목적은 바텀애시 및 준설토 기반의 인공 경량골재 콘크리트의 합리적 배합설계 절차를 제시하는 것이다. 25 배합의 실험결과를 바탕으로 경량골재 콘크리트의 목표성능(압축강도, 절건 밀도, 초기 슬럼프, 공기량)에 대하여 물-시멘트 비, 단위 시멘트양, 경량 잔골재 치환율을 결정하는 식을 제시하였다. 제안된 식과 절대용적 배합의 개념으로부터 각 구성요소들의 단위용적중량을 산정하였다. 제시된 배합설계 절차는 기존 결정에 효율적으로 이용될 수 있다.

• Steel and Composite Structures
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• 제25권3호
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• pp.299-314
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• 2017

The aim of this paper is to investigate the performance of Lightweight Aggregate Concrete Filled Steel Tube (LWCFST) columns experimentally and compare to the behavior of Self-Compacted Concrete Filled Steel Tube (SCCFST) columns under axial loading. Four different L/D ratios and three D/t ratios were used in the experimental program to delve into the compression behaviours. Compressive strength of the LWC and SCC are 33.47 MPa and 39.71 MPa, respectively. Compressive loading versus end shortening curves and the failure mode of sixteen specimens were compared and discussed. The design specification formulations of AIJ 2001, AISC 360-16, and EC4 were also assessed against test results to underline the performance of specification methods in predicting the compression capacity of LWCFST and SCCFST columns. Based on the behaviour of the SCCFST columns, LWCFST columns exhibited different performances, especially in ductility and failure mode. The nature of the utilized lightweight aggregate led to local buckling mode to be dominant in LWCFST columns, even the long LWCFST specimens suffered from this behaviour. While with the SCCFST specimens the global buckling governed the failure mode of long specimens without any loss in capacity. Considering a wide range of column geometries (short, medium and long columns), this paper extends the current knowledge in composite construction by examining the potential of two promising and innovative structural concrete types in CFST applications.

• Steel and Composite Structures
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• 제31권4호
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• pp.329-340
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• 2019

An innovated type of the flat steel plate-lightweight aggregate concrete hollow composite slab was presented in this paper. This kind of the slab is composed of flat steel plate and the lightweight aggregate concrete slab, which were interfaced with a set of perfobond shear connectors (PBL shear connectors) with circular hollow structural sections (CHSS) and the shear stud connectors. Five specimens were tested under static monotonic loading. In the test, the influence of shear span/height ratios and arrangements of CHSS on bending capacity and flexural rigidity of the composite slabs were investigated. Based on the test results, the crack patterns, failure modes, the bending moment-curvature curves as well as the strains of the flat steel plate and the concrete were focused and analyzed. The test results showed that the flat steel plate was fully connected to the lightweight aggregate concrete slab and no obvious slippage was observed between the steel plate and the concrete, and the composite slabs performed well in terms of bending capacity, flexural rigidity and ductility. It was further shown that all of the specimens failed in bending failure mode regardless of the shear span/height ratios and the arrangement of CHSS. Moreover, the plane-section assumption was proved to be valid, and the calculated formulas for predicting the bending capacity and the flexural rigidity of the composite slabs were proposed on the basis of the experimental results.