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CONTENTS
Volume 3, Number 2, April/June 2006
 

Abstract
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

Key Words
impact testing; drop-weight; RC beams; numerical modelling.

Address
Ian M. May and Yi Chen; Department of Civil Engineering, Heriot-Watt University, Edinburgh EH14 4AS, UKrnD. Roger J. Owen, Y. T. Feng and Philip J. Thiele; University of Wales Swansea, Singleton Park, Swansea, SA2 8PP, UK

Abstract
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.

Key Words
concrete; composite construction; connector; nonlinear analysis.

Address
Hilti Corporation, New Business & Technology FL-9494 Schaan, rnFeldkircherstrasse 100, Principality of Liechtenstein

Abstract
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.

Key Words
drying shrinkage; moisture diffusion; damage; composite mechanics; concrete.

Address
A. Suwito; Department of Civil, Environmental and Architectural Engineering, University of Colorado at Boulder, USArnAyman Ababneh; Department of Civil and Environmental Engineering, Clarkson University, USArnYunping Xi and Kaspar Willam; Department of Civil, Environmental and Architectural Engineering, University of Colorado at Boulder, USA

Abstract
(Received November 28, 2005, Accepted May 23, 2006)rnAbstract. 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.

Key Words
corbels; reinforced concrete; experimental program; reliability; probabilistic study; safety margins; high developed Monte Carlo simulation; nonlinear finite element concept; 2D and 3D models.

Address
Alfred Strauss; Department of Civil Engineering + Natural Hazards, Institute for Structural Engineering,rnUniversity of Natural Resources and Applied Life Sciences, Vienna, AustriarnAndrea Mordini; Department of Civil Engineering, University of Parma, Parma, ItalyrnKonrad Bergmeister; Department of Civil Engineering + Natural Hazards, Institute for Structural Engineering,rnUniversity of Natural Resources and Applied Life Sciences, Vienna, Austria

Abstract
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 water-cement 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.

Key Words
durability design; reinforced concrete; fuzzy inference system; expert system.

Address
Research Center of Industrial Technology, Chonbuk National University, Chonju 561-756 Korea

Abstract
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, 300 kg/m3 cement dosage were kept constant and pumice ratios were changed as 25%, 50%, 75% and 100% of replacement for normal aggregate by volume for 3? cm, 5? cm and 7? cm slumps. Other batches were prepared with 200 kg/m3, 250 kg/m3, 350 kg/m3, 400 kg/m3 and 500 kg/m3 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.

Key Words
pumice aggregate, concrete, freezing thawing resistance, density.

Address
Ataturk University, Engineering Faculty, Civil Engineering Department, 25240- Erzurum, Turkey

Abstract
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

Key Words
maturity function; concrete; slipforming; mock-up times; computer aided program.

Address
K.M.A. Hossain; Department of Civil Engineering, Ryerson University, 350 Victoria St, Toronto, ON, M5B 2K3, CanadarnC. Anagnostopoulos; Colt Engineering, 10201 Southport Road, Calgary, AB, CanadarnM. Lachemi; Department of Civil Engineering, Ryerson University, 350 Victoria St, Toronto, ON, M5B 2K3, Canada


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