• Advances in concrete construction
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• 제13권3호
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• pp.233-242
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• 2022

An attempt is made to develop an eco-friendly concrete with ground granulated blast furnace slag (GGBS) and pond ash as partial replacement materials for cement and fine aggregate, respectively without compromising the strength and durability. Sixteen concrete mixes were developed by replacing cement and fine aggregate by GGBS and pond ash, respectively in stages of 10%. The maximum replacement levels of cement and fine aggregates were 50% and 30% respectively. Experimental results revealed that the optimum percentage of GGBS and pond ash replacement levels were 30% and 20% respectively. The optimized mix was used further to study the flexural behavior and durability properties. Reinforced Concrete (RC) beams were cast and tested under a four-point bending configuration. Also, the specimens prepared from the optimized mix were subjected to alternate wet and dry cycles of acid (3.5% HCl and H₂SO₄) and sulphate (10% MgSO₄) solutions. Results show that the optimized concrete mix with GGBS and pond ash had a negligible weight loss and strength reduction.

• Structural Engineering and Mechanics
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• 제47권2호
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• pp.247-263
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• 2013

It is evident that torsional resistance of a reinforced concrete (RC) member is attributed to both concrete and steel reinforcement. However, recent structural design codes neglect the contribution of concrete because of cracking. This paper reports on the results of an experimental and numerical investigation into the torsional capacity of concrete beams reinforced only by longitudinal rebars without transverse reinforcement. The experimental investigation involves six specimens tested under pure torsion. Each specimen was made using a cast-in-place concrete with different amounts of longitudinal reinforcements. To create the torsional moment, an eccentric load was applied at the end of the beam whereas the other end was fixed against twist, vertical, and transverse displacement. The experimental results were also compared with the results obtained from the nonlinear finite element analysis performed in ANSYS. The outcomes showed a good agreement between experimental and numerical investigation, indicating the capability of numerical analysis in predicting the torsional capacity of RC beams. Both experimental and numerical results showed a considerable torsional post-cracking resistance in high twist angle in test specimen. This post-cracking resistance is neglected in torsional design of RC members. This strength could be considered in the design of RC members subjected to torsion forces, leading to a more economical and precise design.

• Computers and Concrete
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• 제31권1호
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• pp.53-69
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• 2023

The rotational stiffness of a semi-rigid beam-to-column connection plays an important role in the reduction of the second-order effects in the precast concrete skeletal frames. The aim of this study is to present a detailed nonlinear finite element study to reproduce the experimental response of a semi-rigid precast beam-to-column connection composed by corbel, dowel bar and continuity tie bars available in the literature. A parametric study was carried using four arrangements of the reinforcing tie bars in the connection, including high ratio of the continuity tie bars passing around the column in the cast-in-place concrete. The results from the parametric study were compared to analytical equations proposed to evaluate the secant rotational stiffness of beam-to-column connections. The good agreement with the experimental results was obtained, demonstrating that the finite element model can accurately predict the structural behaviour of the beam-to-column connection despite its complex geometric configuration. The secant rotational stiffness of the connection was good evaluated by the analytical model available in the literature for ratio of the continuity tie bars of up to 0.69%. Precast beam-to-column connection with a ratio of the continuity tie bars higher than 1.4% had the secant stiffness overestimated. Therefore, an adjustment coefficient for the effective depth of the crack at the end of the beam was proposed for the analytical model, which is a function of the ratio of the continuity tie bars.

• Computers and Concrete
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• 제14권2호
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• pp.193-209
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• 2014

Cyclic test of the columns is of practical relevance to the performance of compression members during an earthquake loading. The strength, ductility and energy absorption capabilities of reinforced concrete (RC) columns subjected to cyclic loading have been estimated by many researchers. These characteristics are not normally inherent in plain concrete but can be achieved by effectively confining columns through transverse reinforcement. An extensive experimental program, in which performance of four RC columns detailed according to provisions of ACI-318-08 was studied in contrast with that of four columns confined by a new proposed technique. This paper presents performance of columns reinforced by standard detailing and cast with 25 and 32 MPa concrete. The experimentally achieved load-displacement hysteresis and backbone curves of two columns are presented. The two approaches which work in conjunction with Response 2000 have been suggested to draw analytical back bone curves of RC columns. The experimental and analytical backbone curves are found in good agreement. This investigation gives a detail insight of the response of RC columns subjected to cyclic loads during their service life. The suggested analytical procedures will be available to the engineers involved in design to appraise the capacity of RC columns.

• Steel and Composite Structures
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• 제13권3호
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• pp.259-275
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• 2012

Concrete filled steel tubular (CFST) member has been widely used in the construction of high-rise buildings for its high axial bearing capacity. It can also be applied on long-span structures such as spatial structures or bridges not only for its high bearing capacity but also for its construction convenience. Concrete casting effect of CFST member is considered in the study of its bearing capacity in this paper. Firstly, in order to authenticate the applicability of constitutive relationship and yield criterion of steel and concrete based on FEM, two ANSYS models are built to simulate and compared with other's test. Secondly, in order to find the huge difference in bearing capacity due to different construction processes, two full-size CFST models are studied when they are horizontally cast and axially compressed. Finally, the effects of slenderness ratio (L/D) and confining parameter (D/t) of CFST members are studied to reveal the intrinsic links between bearing capacity and slenderness ratio or confining parameter.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.998-1001
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• 2011

The concrete track on bridge should be designed to effectively cope with the behavior of the bridge superstructure. For this purpose, in general, shear keys are designed to be installed at a certain intervals on the bridge deck, and the track slab is cast on these shear keys to transfer the load induced by the relative displacement between track and bridge. In this study, to apply the precast concrete slab track on bridge, a shear key structure and its effective installation method are presented. Also, the structural behavior of this shear key has been evaluated by the laboratory mock-up test.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.383-391
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• 2016

This paper reports the results of an experimental program involving several small-scale columns which were constructed to simulate corrosion damage in the field using two accelerated corrosion techniques namely, constant voltage and constant current. A total of six columns were cast for this experiment. For one pair of regular RC columns, corrosion was accelerated using constant voltage and for another pair, corrosion was accelerated using constant current. The remaining pair of regular RC columns was used as control. In the experiment, all the columns were subjected to cyclic wetting and drying using sodium chloride (NaCl) solution. The currents were monitored on an hourly interval and cracks were visually checked throughout the test program. After the specimens had suffered sufficient percentage steel loss, all the columns including the control were tested to failure in compression. The test results generated show that accelerated corrosion using impressed constant current produces more corrosion damage than that using constant voltage. The results suggest that the constant current approach can be better used to simulate corrosion damage of reinforced concrete structures and to assess the effectiveness of various materials, repair strategies and admixtures to resist corrosion damage.

• Steel and Composite Structures
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• 제18권2호
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• pp.375-394
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• 2015

This paper presents the results of four long-term experiments carried out to investigate the time-dependent behaviour of composite floor slabs with particular attention devoted to the development of non-uniform shrinkage through the slab thickness. This is produced by the presence of the steel deck which prevents moisture egress to occur from the underside of the slab. To observe the influence of different drying conditions on the development of shrinkage, the four 3.3 m long specimens consisted of two composite slabs cast on Stramit Condeck $HP^{(R)}$ steel deck and two reinforced concrete slabs, with the latter ones having both faces exposed for drying. During the long-term tests, the samples were maintained in a simply-supported configuration subjected to their own self-weight, creep and shrinkage for four months. Separate concrete samples were prepared and used to measure the development of shrinkage through the slab thickness over time for different drying conditions. A theoretical model was used to predict the time-dependent behaviour of the composite and reinforced concrete slabs. This approach was able to account for the occurrence of non-uniform shrinkage and comparisons between numerical results and experimental measurements showed good agreement. This work highlights the importance of considering the shrinkage gradient in predicting shrinkage deformations of composite slabs. Further comparisons with experimental results are required to properly validate the adequacy of the proposed approach for its use in routine design.

• International Journal of Concrete Structures and Materials
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• 제4권1호
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• pp.3-8
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• 2010

This paper present the results of investigation on the use of rice husk ash as a partial substitute for cement in construction. One hundred and eighty specimens of concrete cubes were cast. 0, 5, 10, 15, and 20% partial replacement of cement with rice husk ash were carried at 1:2:4 mixes by weight with 0.60, 0.65, 0.70 water/cement ratio. The results indicated that compressive strengths of cubes at 0.6, water/cement were higher than 0.65 and 0.70. Also 5% partial replacement cement with rice husk ash at $28^{th}$ day average compressive strength value of $25.4\;N/mm^2$ compared well with 0% partial replacement of cement with rice husk ash of $26.28\;N/mm^2$. This shows that at 5% partial replacement of cement with rice husk ash can be used for structural concrete and at 15% replacement or more it can be used for non - structural construction works or light weight concrete construction. The cost analysis shows substantial amount of savings for the country.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.995-1000
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• 2000

Segmentally erected prestressed concrete box girder bridges have been widely used in Korean high speed railway. Segmental erection has been accomplished along the longitudinal direction and across the depth of cross section. The cross section is similar to a composite cross section, composed of old and new segments. Because these segments have different time-dependent creep and shrinkage properties, a stress redistribution takes place during the construction period. It is the main objective in this research to investigate this behavior. An actual bridge was instrumented with 96 vibrating wire embedded type strain gauges, 6 electronic type steel strain gauges, and 75 thermocouples. Two span continuous high speed railway bridge was selected. Two points of importance, such as the midpoint of the first span and the point of interior support, along the span of the girder were chosen to monitor the time dependent behaviors for an extended period of time. The data collection was starting just after concrete girder were cast and is still going on. According to the measured results, the strain distributions across the depth of the section at midspan and interior support were not continuous and the important redistribution of stresses takes place. Thus, rational design of prestressed concrete composite box girder bridges need.