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CONTENTS
Volume 6, Number 6, December 2009
 

Abstract
The effect of six different curing conditions on compressive strength and ultrasonic pulse velocity (UPV) of volcanic pumice concrete (VPC) and normal concrete (NC) has been studied. The curing conditions include water, air, low temperature (4oC) and different elevated temperatures of up to 110oC. The curing age varies from 3 days to 91 days. The development in the pulse velocity and the compressive strength is found to be higher in full water curing than the other curing conditions. The reduction of pulse velocity and compressive strength is more in high temperature curing conditions and also more in VPC compared to NC. Curing conditions affect the relationship between pulse velocity and compressive strength of both VPC and NC.

Key Words
volcanic pumice; curing; lightweight concrete; pulse velocity; compressive strength.

Address
Khandaker M. Anwar Hossain: Department of Civil Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada

Abstract
Based on a numerical method to analyse the full-range behaviour of prestressed concrete beams with unbonded tendons, parametric studies are carried out to investigate the influence of 11 parameters on the curvature ductility of unbonded prestressed concrete (UPC) beams. It is found that, among various parameters studied, the depth to prestressing tendons, depth to non-prestressed tension steel, partial prestressing ratio, yield strength of non-prestressed tension steel and concrete compressive strength have substantial effects on the curvature ductility. Although the curvature ductility of UPC beams is affected by a large number of factors, rather simple equations can be formulated for reasonably accurate estimation of curvature ductility. Conversion factors are introduced to cope with the difference in partial safety factors, shapes of equivalent stress blocks and the equations to predict the ultimate tendon stress in BS8110, EC2 and ACI318. The same equations can also be used to provide conservative estimates of ductility of UPC beams with compression steel.

Key Words
curvature ductility; full-range behaviour; prestressed concrete; unbonded tendon.

Address
F. T. K. Au: Department of Civil Engineering, The University of Hong Kong, Hong Kong, China
K. H. E. Chan: Department of Civil Engineering, The University of Hong Kong, Hong Kong, China
A. K. H. Kwan: Department of Civil Engineering, The University of Hong Kong, Hong Kong, China
J. S. Du: School of Civil Engineering, Beijing Jiao Tong University, Beijing 100044, China

Abstract
This paper presents a new methodology to evaluate the load carrying capacity of deteriorated non-slender concrete bridge pier columns by construction of the full P-M interaction diagrams. The proposed method incorporates the actual material properties of deteriorated columns, and accounts for amount of corrosion and exposed corroded bar length, concrete loss, loss of concrete confinement and strength due to stirrup deterioration, bond failure, and type of stresses in the corroded reinforcement. The developed structural model and the damaged material models are integrated in a spreadsheet for evaluating the load carrying capacity for different deterioration stages and/or corrosion amounts. Available experimental and analytical data for the effects of corrosion on short columns subject to axial loads combined with moments (eccentricity induced) are used to verify the accuracy of proposed model. It was observed that, for the limited available experimental data, the proposed model is conservative and is capable of predicting the load carrying capacity of deteriorated reinforced concrete columns with reasonable accuracy. The proposed analytical method will improve the understanding of effects of deterioration on structural members, and allow engineers to qualitatively assess load carrying capacity of deteriorated reinforced concrete bridge pier columns.

Key Words
corrosion; deterioration model; concrete columns; bridge evaluation; P-M interaction diagrams.

Address
Mucip Tapan: Department of Civil Engineering, Yuzuncu Yil University, Zeve Kampusu, Van 65080, Turkey
Riyad S. Aboutaha: Department of Civil & Environmental Engineering, Syracuse University, 255 Link Hall, Syracuse, NY 13244, USA

Abstract
This paper presents a design framework developed using axiomatic design (AD) theory that can be applied in the design process of porous concrete. The main contribution of this paper is the definition of an AD framework based on the needs and functional requirements of porous concrete. The framework shows how AD theory can be used to provide guidelines for proportioning and manufacturing porous concrete. The advantage of the AD approach is that it systemizes the way to decouple design parameters and makes designers to think rationally between what we want to achieve and how we propose to satisfy the functional requirements of porous concrete. In this paper, test results of laboratorysize porous concrete specimens under compression were analyzed to evaluate the performance of the porous concrete based on the desired functional requirements.

Key Words
axiomatic design; porous concrete; mix proportioning; functional requirements; design parameters; process variables.

Address
X. H. Tran: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea
R. Tawie: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea
H. K. Lee: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea

Abstract
The analysis of prismatic members made of reinforced concrete under inclined bending, especially the computation of ultimate loads, is a pronounced non-linear problem which is frequently solved by discretizing the stress distribution in the cross-section using interpolation functions. In the approach described in the present contribution the exact analytical stress distribution is used instead. The obtained expressions are integrated by means of a symbolic manipulation package and automatically converted to optimized Fortran code. The direct problem-computation of ultimate internal forces given the position of the neutral axis-is first described. Subsequently, two kinds of inverse problem are treated: the computation of rupture envelops and the dimensioning of reinforcement, given design internal forces. An iterative Newton-Raphson procedure is used. Examples are presented.

Key Words
reinforced concrete sections; ultimate limit state; prismatic members; inclined bending; formulation; design.

Address
V. Dias da Silva: Department of Civil Engineering, University of Coimbra, Polo II-Pinhal de Marrocos, 3030-290 Coimbra,, Portugal
M. H. F. M. Barros: Department of Civil Engineering, University of Coimbra, Polo II-Pinhal de Marrocos, 3030-290 Coimbra,, Portugal
E. N. B. S. Julio: Department of Civil Engineering, University of Coimbra, Polo II-Pinhal de Marrocos, 3030-290 Coimbra,, Portugal
C. C. Ferreira: Department of Civil Engineering, University of Coimbra, Polo II-Pinhal de Marrocos, 3030-290 Coimbra,, Portugal


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