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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Computers and Concrete
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Volume & Issues
Volume 3, Issue 6 - Dec 2006
Volume 3, Issue 5 - Oct 2006
Volume 3, Issue 4 - May 2006
Volume 3, Issue 2_3 - Apr 2006
Volume 3, Issue 1 - Feb 2006
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Reinforced concrete beams under drop-weight impact loads
May, Ian M. ; Chen, Yi ; Owen, D. Roger J. ; Feng, Y.T. ; Thiele, Philip J. ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 79~90
DOI : 10.12989/cac.2006.3.2_3.079
This paper describes the results of an investigation into high mass-low velocity impact behaviour of reinforced concrete beams. Tests have been conducted on fifteen 2.7 m or 1.5 m span beams under drop-weight loads. A high-speed video camera has been used at rates of up to 4,500 frames per second in order to record the crack formation, propagation, particle spallation and scabbing. In some tests the strain in the reinforcement has been recorded using "Durham" strain gauged bars, a technique developed by Scott and Marchand (2000) in which the strain gauges are embedded in the bars, so that the strains in the reinforcement can be recorded without affecting the bond between the concrete and the reinforcement. The impact force acting on the beams has been measured using a load cell placed within the impactor. A high-speed data logging system has been used to record the impact load, strains, accelerations, etc., so that time histories can be obtained. This research has led to the development of computational techniques based on combined continuum/discontinuum methods (finite/discrete element methods) to permit the simulation of impact loaded reinforced concrete beams. The implementation has been within the software package ELFEN (2004). Beams, similar to those tested, have been analysed using ELFEN a good agreement has been obtained for both the load-time histories and the crack patterns.
Nonlinear analysis of connectors applied on concrete composite constructions
Winkler, B. ; Bianchi, P. ; Siemers, M. ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 91~102
DOI : 10.12989/cac.2006.3.2_3.091
To place concrete overlays has become a standard application in the strengthening and rehabilitation of concrete structures such as bridges, tunnels, parking decks and industrial buildings. In general, connectors are used to ensure a monolithic behavior of the two concrete layers. Within the framework of the development of a new connector wedge splitting tests and shear tests were performed, in addition nonlinear finite element analyses were applied to investigate the load transfer behavior of the connectors for different prototypes. The numerical simulation results were compared to experimental data. The computed load-displacement curve demonstrates good correspondence with the curves obtained in the experiments, and the experimental crack patterns are reasonably simulated by the computed crack propagation. Both numerical and experimental investigations on the wedge splitting test and on the shear test served as basis for the development of new type of connectors.
The coupling effect of drying shrinkage and moisture diffusion in concrete
Suwito, A. ; Ababneh, Ayman ; Xi, Yunping ; Willam, Kaspar ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 103~122
DOI : 10.12989/cac.2006.3.2_3.103
Drying shrinkage of concrete occurs due to the loss of moisture and thus, it is controlled by moisture diffusion process. On the other hand, the shrinkage causes cracking of concrete and affects its moisture diffusion properties. Therefore, moisture diffusion and drying shrinkage are two coupled processes and their interactive effect is important for the durability of concrete structures. In this paper, the two material parameters in the moisture diffusion equation, i.e., the moisture capacity and humidity diffusivity, are modified by two different methods to include the effect of drying shrinkage on the moisture diffusion. The effect of drying shrinkage on the humidity diffusivity is introduced by the scalar damage parameter. The effect of drying shrinkage on the moisture capacity is evaluated by an analytical model based on non-equilibrium thermodynamics and minimum potential energy principle for a two-phase composite. The mechanical part of drying shrinkage is modeled as an elastoplastic damage problem. The coupled problem of moisture diffusion and drying shrinkage is solved using a finite element method. The present model can predict that the drying shrinkage accelerates the moisture diffusion in concrete, and in turn, the accelerated drying process increases the shrinkage strain. The coupling effects are demonstrated by a numerical example.
Nonlinear finite element analysis of reinforced concrete corbels at both deterministic and probabilistic levels
Strauss, Alfred ; Mordini, Andrea ; Bergmeister, Konrad ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 123~144
DOI : 10.12989/cac.2006.3.2_3.123
Reinforced concrete corbels are structural elements widely used in practical engineering. The complex response of these elements is described in design codes in a simplified manner. These formulations are not sufficient to show the real behavior, which, however, is an essential prerequisite for the manufacturing of numerous elements. Therefore, a deterministic and probabilistic study has been performed, which is described in this contribution. Real complex structures have been modeled by means of the finite element method supported primarily by experimental works. The main objective of this study was the detection of uncertainties effects and safety margins not captured by traditional codes. This aim could be fulfilled by statistical considerations applied to the investigated structures. The probabilistic study is based on advanced Monte Carlo simulation techniques and sophisticated nonlinear finite element formulations.
Fuzzy inference based cover thickness estimation of reinforced concrete structure quantitatively considering salty environment impact
Do, Jeong-Yun ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 145~161
DOI : 10.12989/cac.2006.3.2_3.145
This article involves architecting prototype-fuzzy expert system for designing the nominal cover thickness by means of fuzzy inference for quantitatively representing the environment affecting factor to reinforced concrete in chloride-induced corrosion environment. In this work, nominal cover thickness to reinforcement in concrete was determined by the sum of minimum cover thickness and tolerance to that defined from skill level, constructability and the significance of member. Several variables defining the quality of concrete and environment affecting factor (EAF) including relative humidity, temperature, cyclic wet and dry, and the distance from coast were treated as fuzzy variables. To qualify EAF the environment conditions of cycle degree of wet-dry, relative humidity, distance from coast and temperature were used as input variables. To determine the nominal cover thickness a qualified EAF, concrete grade, and watercement ratio were used. The membership functions of each fuzzy variable were generated from the engineering knowledge and intuition based on some references as well as some international codes of practice.
The effects of different cement dosages, slumps and pumice aggregate ratios on the freezing and thawing of concrete
Turkmen, Ibrahim ; Demirboga, Ramazan ; Gul, Rustem ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 163~175
DOI : 10.12989/cac.2006.3.2_3.163
This research was conducted to determine effect of pumice aggregate ratio, cement dosage and slumps on freeze-thaw resistance, density, water absorption and elasticity of concrete. In the first batch,
cement dosage were kept constant and pumice ratios were changed as 25%, 50%, 75% and 100% of replacement for normal aggregate by volume for
slumps. Other batches were prepared with
cement dosages and 25% pumice aggregate +75% normal aggregate at a constant slump. Test results showed that when pumice-aggregate ratio decreased the density and freeze-thaw resistance of concretes increased. With increasing of cement dosage in the mixtures, density of the concretes increased, however, freeze-thaw resistance of concretes decreased. Water absorption of the concrete decreased with increasing cement dosage but increased with the pumice ratio. Water absorption of the concrete also decreased after freeze-thaw cycles. Freeze-thaw resistance of concretes was decreased with increasing the slumps.
Development of a computer aided program for slipforming operations incorporating maturity approach
Hossain, K.M.A. ; Anagnostopoulos, C. ; Lachemi, M. ;
Computers and Concrete, volume 3, issue 2_3, 2006, Pages 177~195
DOI : 10.12989/cac.2006.3.2_3.177
Slipforming is a construction method in which the forms move continuously during the placement of concrete. This paper presents the development of a computer aided program designated as "CADSLIPFORM" for slipforming operations. The program incorporates maturity methods for the prediction of initial setting times of slipform concrete layers using laboratory data (time-temperature histories and setting times of concrete mixtures at different temperatures) and generates slipform mock-up times. The performance of CADSLIPFORM is validated by comparing simulated mock-up times with those estimated in the field through conventional hard front by rod (R) method. Moreover, the program versatility is demonstrated by illustrating mock-up simulations for different cases with variable slipform parameters such as: number and thickness of concrete layers, concrete temperature (simulating variable setting times) and slipform speed. The program also incorporates the choice of Freiesleben Hansen & Pederson (FHP) and Carino & Tank (CT) maturity functions. CADSLIPFORM can assist user to develop reliable schedule of slipforming operation suitable for a specific project by optimizing various slipform parameters.