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CONTENTS
Volume 10, Number 1, June 2012
 

Abstract
This paper presents the details of studies conducted on hollow concrete block masonry (HCBM) units and wall panels. This study includes, compressive strength of unit block, ungrouted and grouted HCB prisms, flexural strength evaluation, testing of HCBM panels with and without opening. Non-linear finite element (FE) analysis of HCBM panels with and without opening has been carried out by simulating the actual test conditions. Constant vertical load is applied on the top of the wall panel and then lateral load is applied in incremental manner. The in-plane deformation is recorded under each incremental lateral load. Displacement ductility factors and response reduction factors have been evaluated based on experimental results. From the study, it is observed that fully grouted and partially reinforced HCBM panel without opening performed well compared to other types of wall panels in lateral load resistance and displacement ductility. In all the wall panels, shear cracks originated at loading point and moved towards the compression toe of the wall. The force reduction factor of a wall panel with opening is much less when compared with fully reinforced wall panel with no opening. The displacement values obtained by non-linear FE analysis are found to be in good agreement with the corresponding experimental values. The influence of mortar joint has been included in the stress-strain behaviour as a monolith with HCBM and not considered separately. The derived response reduction factors will be useful for the design of reinforced HCBM wall panels subjected to lateral forces generated due to earthquakes.

Key Words
hollow concrete block masonry; prisms; wall panels; ductility; finite element analysis; static nonlinear.

Address
A. Rama Chandra Murthy, S. Chitra Ganapathi, Nagesh R. Iyer,
N. Lakshmanan and N.G. Bhagavan: CSIR-Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai-600 113, India

Abstract
The performance of a concrete is significantly influenced by its mixture proportion and the coating thickness on aggregate surface. The concrete in this study is designed by estimating the blending ratio of aggregate using a densified mixture design algorithm (DMDA) based on an ideal grading curve and estimating the paste volume as the sum of the amount of paste needed to provide an assigned coating paste thickness. So as to obtain appropriate concrete amount, and thus can accurately estimate the property of concrete. Deduction of this mix design formula is simple and easy understanding, and meanwhile to obtain result is fast. This estimation model of mix design is expected to reward to industry and effectively upgrade concrete quality.

Key Words
densified mixture design algorithm (DMDA); ideal grading curve; coating paste thickness.

Address
H.Y. Wang: Department of Civil Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan. R.O.C.
C.L. Hwang and S.T. Yeh: Department of Construction Engineering and Technology, National Taiwan University of Science and Technology, Taipei, Taiwan. R.O.C.

Abstract
The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of

Key Words
ideal gradating curve; coating paste thickness; concrete property; experimental work.

Address
H.Y. Wang: Department of Civil Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan. R.O.C.
C.L. Hwang and S.T. Yeh: Department of Construction Engineering and Technology, National Taiwan University of Science and Technology, Taipei, Taiwan. R.O.C.

Abstract
Nano-particle-reinforced cement mortars have been the basis of research in recent years and a significant growth is expected in the future. Therefore, optimization and quantification of the effect of processing parameters and mixture ingredients on the performance of cement mortars are quite important. In this work, the effects of nano-silica, water/binder ratio, sand/binder ratio and aging (curing) time on the compressive strength of cement mortars were modeled by means of artificial neural network (ANN). The developed model can be conveniently used as a rough estimate at the stage of mix design in order to produce high quality and economical cement mortars.

Key Words
cement mortar; nano particle; computer modeling; compressive strength; artificial neural networks; curing.

Address
Reza Alavi: Doust Construction Engineering Group Co., Isfahan 81736-95716, Iran
Hamed Mirzadeh: Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

Abstract
Although the effect of corrosion of reinforcing bar on the shear behavior of the reinforced concrete (RC) beam had been simulated by tests of the beam with unbonded, half-exposed or wholeexposed tensile steel reinforcements as well as defective stirrup anchorages, theoretical methods to accurately predict remaining capacity of this kind of RC beams, especially shear capacity, are still lacking. Considering the possible position of the critical inclined crack, the actual pattern of strains in the concrete body within the partial length and the proposed compatibility condition of deformations of the RC beam, shear strength of the RC beam with unbonded or exposed tensile steel reinforcements and/or defective stirrup anchorages is predicted. Comparison between the model

Key Words
shear strength; unbonded length; critical inclined crack; defective stirrup anchorages.

Address
Xiao-Hui Wang and Xi-La Liu: Department of Civil Engineering, Shanghai Jiaotong University, Shanghai, 200240, P.R. China

Abstract
This paper estimates theoretically the diffusion-reaction behaviour of sulfate ion in concrete caused by environmental sulfate attack. Based on Fick's second law and chemical reaction kinetics, a nonlinear and nonsteady diffusion-reaction equation of sulfate ion in concrete, in which the variable diffusion coefficient and the chemical reactions depleting sulfate ion concentration in concrete are considered, is proposed. The finite difference method is utilized to solve the diffusion-reaction equation of sulfate ion in concrete, and then it is used to simulate the diffusion-reaction process and the concentration distribution of sulfate ion in concrete. Afterwards, the experiments for measuring the sulfate ion concentration in concrete are carried out by using EDTA method to verify the proposal model, and results show that the proposed model is basically in agreement with the experimental results. Finally, Numerical example has been completed to investigate the diffusion-reaction behavior of sulfate ion in the concrete plate specimen immersed into sulfate solution.

Key Words
model; diffusion-reaction behavior; concrete; sulfate ion; model; EDTA.

Address
Xiao-Bao Zuo: Department of Civil Engineering, Nanjing University of Science & Technology, Nanjing, 210094, P.R. China; Jiangsu Key Laboratory of Construction Materials, Southeast University, Nanjing 211189, P.R. China
Wei Sun and Hua Li: Jiangsu Key Laboratory of Construction Materials, Southeast University, Nanjing 211189, P.R. China
Yu-Kui Zhao: Department of Civil Engineering, Nanjing University of Science & Technology, Nanjing, 210094, P.R. China


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