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CONTENTS
Volume 4, Number 6, December 2007
 

Abstract
This study is mainly focused on applying Fuller?s ideal gradation curve to theoretically design blended ratio of all solid materials of a reactive powder mortar (RPM), also known as reactive powder concrete (RPC), with the aid of error function, and then to study the effect of fly ash/slag on the performance of RPM. The solid particle is assumed to be spherical particles. Then, the void volume of paste (Vv) and the paste content with specific quality can be obtained. As conclusion, under Fuller?s ideal grading curve, the amount of fly ash/slag mixture is higher than that with silica fume along due to it better filled the void within solid particle and obtains higher packing density.

Key Words
reactive powder mortar (RPM); reactive powder concrete (RPC); Fuller?s gradation curve; error function; fly ash/slag.

Address
C. L. Hwang; Department of Construction Engineering, National Taiwan University of Science and Technology, No. 43, section 4, Keelung Road, Taipei 106, Taiwan
S. L. Hsieh; Department of Civil Engineering, National Taiwan University of Science and Technology, Nanya Institute of Technology, No. 414, section 3, Chung-Shang E Road, Taipei 302, Taiwan

Abstract
The shrinkage of large reinforced concrete floors often gives rise to cracking problems. To identify the problematic areas, shrinkage movement analysis is often carried out by finite element method with proper creep and shrinkage models using step-by-step time integration. However as the full stress history prior to the time interval considered is necessary, with the increase in the number of time intervals used, the amount of computations increases dramatically. Therefore a new method using the shrinkageadjusted elasticity modulus (SAEM) is introduced so that analysis can be carried out using one single step. Examples are presented to demonstrate its usefulness.

Key Words
F. T. K. Au, C. H. Liu and P. K. K. Lee; Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China

Address
age-adjusted elasticity modulus; creep; finite element method; reinforced concrete floor; shrinkage; shrinkage-adjusted elasticity modulus.

Abstract
A simple analytical procedure to analyze reinforced concrete (RC) beams with cracked section is proposed on the basis of the simplified moment-curvature relations of RC sections. Unlike previous analytical models which result in overestimation of stiffness and underestimation of structural deformations induced from assuming perfect-bond condition between steel and concrete, the proposed analytical procedure considers fixed-end rotation caused by anchorage. Furthermore, the proposed analytical procedure, compared with previous numerical models, promotes effectiveness of analysis by reflecting several factors which can influence nonlinearity of RC structure into the simplified moment-curvature relation. Finally, correlation studies between analytical and experimental results are conducted to establish the applicability of the proposed analytical procedure to the nonlinear analysis of RC structures.

Key Words
reinforced concrete; anchorage slip; fix-end rotation; moment-curvature relation.

Address
Hyundai Development Institute of Construction Technology, #102-4, Mabuk-Dong, Giheung-Gu, Yongin-Si, Gyounggi-Do, 446-716, Korea

Abstract
The ultrasonic pulse velocity method has been widely used to evaluate the quality of concrete and assess the structural integrity of concrete structures. But its use for predicting strength is still limited since there are many variables affecting the relationship between strength and pulse velocity of concrete. This study is focused on establishing a complicated correlation between known input data, such as pulse velocity and mixture proportions of concrete, and a certain output (compressive strength of concrete) using artificial neural networks (ANN). In addition, the results predicted by the developed multilayer perceptrons (MLP) networks are compared with those by conventional regression analysis. The result shows that the correlation between pulse velocity and compressive strength of concrete at various ages can be well established by using ANN and the accuracy of the estimates depends on the quality of the information used to train the network. Moreover, compared with the conventional approach, the proposed method gives a better prediction, both in terms of coefficients of determination and root-mean-square error.

Key Words
ultrasonic pulse velocity; concrete compressive strength; artificial neural network; multilayer perceptrons.

Address
Chao-Wei Tang; Department of Civil Engineering & Engineering Informatics, Cheng-Shiu University, Taiwan, R.O.C.
Yiching Lin and Shih-Fang Kuo; Department of Civil Engineering, National Chung Hsing University, Taiwan, R.O.C.

Abstract
The densified mixture design algorithm (DMDA) was employed to manufacture high-performance lightweight concrete (LWAC) using silt dredged from reservoirs in southern Taiwan. Dredged silt undergoing hydration and high-temperature sintering was made into a lightweight aggregate for concrete mixing. The workability and durability of the resulting concrete were examined. The LWAC made from dredged silt had high flowability, which implies good workability. Additionally, the LWAC also had good compressive strength and anti-corrosion properties, high surface electrical resistivity and ultrasonic pulse velocity as well as low chloride penetration, all of which are indicators of good durability.

Key Words
densified mixture design algorithm; silt; lightweight aggregate; durability.

Address
H. Y. Wang; Department of Civil Engineering and Disaster Mitigation Technology, National Kaohsiung University of Applied Science, Kaohsiung, 807, Taiwan


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