• Computers and Concrete
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• 제1권2호
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• pp.151-168
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• 2004

A two-dimensional nonlinear finite element model is developed to simulate time-dependent cracking of reinforced concrete members under service loads. To predict localized cracking, the crack band model is employed to model individual crack opening. In conjunction with the crack band model, a bond-interface element is used to model the slip between concrete and reinforcing steel permitting large slip displacements between the concrete element nodes and the steel truss element nodes at crack openings. The time-dependent effects of concrete creep and shrinkage are incorporated into the smeared crack model as inelastic pre-strains in an iterative solution procedure. Two test examples are shown to verify the finite element model with good agreement between the model and the observed test results.

• Computers and Concrete
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• 제14권4호
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• pp.419-444
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• 2014

In this study experimental result of a total of eight SCC and FRSCC slabs with the same cross-section were monitored for up to 240 days to measure the time-dependent development of cracking and deformations under service loads are presented. For this purpose, four SCC mixes are considered in the test program. This study aimed to compare SCC and FRSCC experimental results with conventional concrete experimental results. The steel strains within the high moment regions, the concrete surface strains at the tensile steel level, deflection at the mid-span, crack widths and crack spacing were recorded throughout the testing period. Experimental results show that hybrid fibre reinforced SCC slabs demonstrated minimum instantaneous and time-dependent crack widths and steel fibre reinforced SCC slabs presented minimum final deflection.

• Steel and Composite Structures
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• 제7권3호
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• pp.219-240
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• 2007

An analytical-numerical procedure has been presented in this paper to take into account the nonlinear effects of concrete cracking and time-dependent effects of creep and shrinkage in the concrete portion of the continuous composite beams under service load. The procedure is analytical at the element level and numerical at the structural level. The cracked span length beam element consisting of uncracked zone in middle and cracked zones near the ends has been proposed to reduce the computational effort. The progressive nature of cracking of concrete has been taken into account by division of the time into a number of time intervals. Closed form expressions for stiffness matrix, load vector, crack lengths and mid-span deflection of the beam element have been presented in order to reduce the computational effort and bookkeeping. The procedure has been validated by comparison with the experimental and analytical results reported elsewhere and with FEM. The procedure can be readily extended for the analysis of composite building frames where saving in computational effort would be very considerable.

• Computers and Concrete
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• 제16권2호
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• pp.223-243
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• 2015

Self-compacting concrete (SCC) can be placed and compacted under its own weight with little or no compaction. It is cohesive enough to be handled without segregation or bleeding. Modifications in the mix design of SCC may significantly influence the material's mechanical properties. Therefore, it is vital to investigate whether all the assumed hypotheses about conventional concrete (CC) are also valid for SCC structures. The aim in this paper is to develop analytical models for flexural cracking that describe in appropriate detail the observed cracking behaviour of the reinforced concrete flexural one way slabs tested. The crack width and crack spacing calculation procedures outlined in five international codes, namely Eurocode 2 (1991), CEB-FIP (1990), ACI318-99 (1999), Eurocode 2 (2004), and fib-Model Code (2010), are presented and crack widths and crack spacing are accordingly calculated. Then, the results are compared with the proposed analytical models and the measured experimental values, and discussed in detail.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.355-362
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• 2001

This study deals with cracking control of concrete deck in steel-concrete composite bridges according to the concrete slab casting sequences. In correlation studies between casting sequences, time dependent effects of concrete creep and shrinkage are implemented in the analytical model. Finally, the methods of cracking control in terms of concrete slump and relative humidity are suggested to prevent early transverse cracking of concrete slab.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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• pp.41-44
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• 1991

Time dependent analysis of prestressed concrete beams subjected to pure torsion is studied. The present theory covers the behavior from the service load range to the ultimate stage. The tensile resistance of concrete is appropriately considered. The biaxial stress effects due to diagonal cracking are also taken into account. The time dependent aging, creep and shringkage effects are modelled by employing the equivalent nonmechanical torque concept. The present theory allows more accurate prediction of the service load behavior of pretressed concrete members.

• 콘크리트학회논문집
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• 제11권4호
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• pp.3-11
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• 1999

The creep characteristics of concrete under tensile stress has been usually assumed to have the same characteristics as that under compressive stress in the time-dependent analysis of concrete structures. However, it appears from the recent experimental studies that tensile creep behavior is much different from compressive one. In particular, high sustaining tensile stress may cause time-dependent cracking and thus lead to tensile failure. It is, therefore, necessary to model the tensile creep behavior accurately for realistic time-dependent analysis of concrete structures. The present paper to have been focused to suggested more realistic model for the tensile creep behavior of concrete. The models are compared with tensile creep test data available in the literature. The proposed model may allow more refined analysis of concrete structures under time-dependent loading.

• International Journal of Concrete Structures and Materials
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• 제7권1호
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• pp.79-93
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• 2013

One of the biggest problems affecting bridges is the transverse cracking and deterioration of concrete bridge decks. The causes of early age cracking are primarily attributed to plastic shrinkage, temperature effects, autogenous shrinkage, and drying shrinkage. The cracks can be influenced by material characteristics, casting sequence, formwork, climate conditions, geometry, and time dependent factors. The cracking of bridge decks not only creates unsightly aesthetic condition but also greatly reduces durability. It leads to a loss of functionality, loss of stiffness, and ultimately loss of structural safety. This investigation consists of field, laboratory, and analytical phases. The experimental and field testing investigate the early age transverse cracking of bridge decks and evaluate the use of sealant materials. The research identifies suitable materials, for crack sealing, with an ability to span cracks of various widths and to achieve performance criteria such as penetration depth, bond strength, and elongation. This paper also analytically examines the effect of a wide range of parameters on the development of cracking such as the number of spans, the span length, girder spacing, deck thickness, concrete compressive strength, dead load, hydration, temperature, shrinkage, and creep. The importance of each parameter is identified and then evaluated. Also, the AASHTO Standard Specification limits liveload deflections to L/800 for ordinary bridges and L/1000 for bridges in urban areas that are subject to pedestrian use. The deflection is found to be an important parameter to affect cracking. A set of recommendations to limit the transverse deck cracks in bridge decks is also presented.

• Structural Engineering and Mechanics
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• 제18권3호
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• pp.363-376
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• 2004

The present study provides a relatively simple and accurate analytical model for the prediction of time-dependent stresses and curvatures of cracked R.C. sections under working loads. A more simplified solution is also provided. The proposed models are demonstrated by considering a numerical example and conducting a parametric study on the effects of relevant R.C. design parameters. In contrary to tension reinforcement, the compression reinforcement is found to contribute significantly in reducing tensile stresses in tension steel and in reducing the total section curvatures. The good accuracy of the proposed approximate solution opens a new vision towards a simple yet accurate model for the prediction of time-dependent effects in R.C. structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.657-662
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• 2003

In this study. a micro-corrosion model of steel in RC structure is established for micro-structure development in view to micro-mechanics and the model is composed of chloride penetration model and oxygen diffusion model to evaluate for corrosion rate and accumulated corrosion amounts. Also the model is composed of corrosion-cracking model for prediction of corrosion-cracking. The time and space dependent induced corrosion-cracking of RC structures including changes of corrosion rates and concentrations of chloride ion are simulated using the finite element analysis adopted the proposed model Then, results of the analysis are compared with test results for verification.