Structural Concrete, Vol. 7, no. 3, September 2006

Written on 19 August 2011.

Cracking analysis of reinforced concrete tensioned members

S. Khalfallah, University of Jijel, Algeria 

An analytical model, which can simulate the cracking response of reinforced concrete tensioned members, is presented. This model is principally based on the bond stress-slip repartition function that was successfully applied to the analysis of tensile reinforced concrete members. The formalism of repartition functions of loads, strains and slip between steel and surrounding concrete, has allowed analysis of the cracking phenomenon and its influence on the structural behaviour of reinforced concrete members. The tension stiffening effect accompanying the cracking mechanism is taken into account in a more appropriate manner. The phenomenon of localisation of micro-cracking owing to the softening behaviour of concrete in tension is based on the conservative concept of the cracking fracture energy assuming that the band of strain localisation is an intrinsic parameter of the material. The predictive results show that the model is very satisfactory, allowing the evaluation of each material contribution especially in the cracked range. Moreover, a correlation between the obtained and experimental results is observed through the local and global responses. 

Structural Concrete, Vol. 7, no. 2, June 2006

Written on 19 August 2011.

Report on the First fib Congress 2002, Osaka, Japan

T. Yoshioka, Oriental Construction, Japan
T. Mori, P.S. Mitsubishi Construction, Japan
A. Kasuga, Sumitomo Mitsui Construction, Japan
T. Miyagawa, Kyoto University, Japan

With a theme of "Concrete Structures in the 21st Century", the First fib Congress was successfully held in Osaka, Japan. Organised jointly by the Japan Prestressed Concrete Engineering Association and the Japan Concrete Institute, the Congress ran from 13th October to 19th October 2002. This report introduces the Congress and confirms that it has enabled us to envisage the prospects for concrete structures in the 21st century. 

Structural Concrete, Vol. 7, no. 3, September 2006

Written on 19 August 2011.

Extradosed bridges in Japan

A. Kasuga, Sumitomo Mitsui Construction Co., Ltd., Tokyo, Japan

Extradosed bridges are similar to cable-stayed bridges in that stay cables are used for strengthening. The concept of extradosed bridges has been taken up in Japan, where several bridges of this type have now been constructed. This paper shows five extradosed bridges that were designed and built by the author, and explicates the difference between extradosed and cable-stayed bridges in terms of structural aspects. In addition, the method of design for stay cables in Japanese specifications is introduced. 

Structural Concrete, Vol. 7, no. 2, June 2006

Written on 19 August 2011.

Bond clause proposals for FRP-bars/rods in concrete based on CEB/FIP Model Code 90. Part 2: Design lengths and tension stiffening

R. Tepfers, Chalmers University of Technology, Göteborg, Sweden

The bond clauses in the CEB/FIP Model Code 1990 (MC90) were written for steel reinforcement in concrete. Since then, fibre reinforced polymer (FRP) reinforcing bars have been introduced as an alternative. To make use of fibre composites, it is necessary to bring these materials into codes of practice and the easiest way is to adapt the code clauses for steel reinforced concrete to FRP reinforced concrete. Proposals for the design bond stress code clauses have been presented in an earlier paper. This paper covers proposals for the design lengths and tension stiffening code clauses. 

Structural Concrete, Vol. 7, no. 2, June 2006

Written on 19 August 2011.

Load-deflection performance of partially prestressed concrete T-beams with steel fibres in partial and full depth

J. Thomas, Indian Institute of Science, Bangalore, India
A. Ramaswamy, Indian Institute of Science, Bangalore, India

A total of twelve partially prestressed concrete T-beams were cast without and with fibres in partial and full depth. These beams were tested to assess the effect of fibre addition in different zones in the cross-section, namely, flange, web or the entire cross-section, on the load-deflection performance of the flexure critical beam specimens. An attempt has been made to predict the load-deflection characteristics of the beam specimens utilising the tension softening effects in the stress-strain behaviour of fibre-reinforced concrete. The proposed model accounts for the interaction of the matrix with the fibre pull-out mechanism. The details of the constitutive material properties used and the proposed layer-based analysis are presented in this paper. Comparisons with test data show good agreement. 

Structural Concrete, Vol. 7, no. 1, March 2006

Written on 19 August 2011.

Strength efficiency of metakaolin in concrete

K. Ganesh Babu, Indian Institute of Technology, Chennai, India
P. Dinakar, Indian Institute of Technology, Chennai, India

The use of mineral admixtures is widely accepted, because of several improvements possible in concrete composites and the overall economy. Of these metakaolin is one mineral admixture that appears to have significant potential for the production of high-strength and high-performance concretes. Although available information on metakaolin concretes is limited, the present paper attempts to quantify the 28-day cementitious efficiency of metakaolin in concrete at various replacement levels from the data available in the literature. It was seen that the efficiency of metakaolin in concretes can also be defined through a procedure adopted earlier for other cementitious materials like fly ash, silica fume and ground granulated blast-furnace slag (GGBS). The overall strength efficiency was found to be a combination of two parameters, one depending on the age and the other depending on the percentage of replacement, as is the case with other pozzolans.