Written on 19 août 2011.
R. N. F. do Carmo, Department of Civil Engineering, ISEC-Polytechnic Institute of Coimbra Portugal S. M. R. Lopes, Department of Civil Engineering, FCTUC-Polo II-University of Coimbra Portugal L. F A. Bernardo, Department of Civil Engineering, University of Beira Interior Portugal Evaluating the ducility of reinforced concrete beams is essential in order to avoid a fragile collapse of the structure by ensuring an adequate deformation at ultimate load. This paper presents a theoretical model for the calculation of plastic rotation. Results obtained are compared with those obtained from an experimental programme in which a set of beams were tested to failure. From the comparison, a good agreement between theoretical and experimental results was achieved. The proposed theoretical model considers the influence of certain factors: steel properties, concrete strength, section depth, and the tension stiffening effect. Concrete strength, particularly, is an interesting parameter since for high-strength concrete, the ultimate concrete strain, εcu, decreases as the concrete strength increases.
Written on 19 août 2011.
Catherine French, University of Minnesota, USA This paper provides a brief overview of Session 8 'Durability of Concrete Structures' of the fib 2002 congress on Concrete Structures in the 21st Century, which was held in Osaka on 13-19 October 2002. The keynote speaker of the session, Dr Odd E. Gjørv, Professor and Head of the Department of Building Materials at the Norwegian University of Science and Technology at Trondheim, has conducted concrete research for more than 40 years. His research has focused on a broad range of topics related to the durability of reinforced and prestressed concrete structures in severe environments. His paper addressed durability and service-life issues of concrete structures. In addition to the keynote address, more than 50 papers were considered for this session, covering topics in the following areas: general issues related to concrete serviceability and durability, corrosion of reinforcement, and grouting of post-tensioned systems, as well as several case studies. The highlights of some of the papers are described here.
Written on 19 août 2011.
I. Kovacs, College Faculty of Technology, Department of Civil Engineering, University of Debrecen, Hungary G. L. Balazs, Budapest University of Technology and Economics, Department of Construction Materials and Engineering Geology, Hungary Results of an experimental study on 21 fibre reinforced concrete beams indicate that steel fibres do not only increase shear capacity but also provide substantial post-peak resistance and ductility in conventionally reinforced beams as well as in prestressed pretensioned concrete beams. The tests were carried out on 2m long beam specimens reinforced with longitudinal bars and fibres. Test variables were amount and type of fibres, amount of stirrups and type of longitudinal reinforcement (prestressed or non-prestressed).
Written on 19 août 2011.
I. Kovacs, College Faculty of Technology, Department of Civil Engineering, University of Debrecen, Hungary G. L. Balazs, Budapest University of Technology and Economics, Department of Construction Materials and Engineering Geology, Hungary Results of an experimental study on 21 fibre reinforced concrete beams indicate that steel fibres do not only increase shear capacity but also provide substantial post-peak resistance and ductility in conventionally reinforced beams as well as in prestressed pretensioned concrete beams. The tests were carried out on 2m long beam specimens reinforced with longitudinal bars and fibres. Test variables were amount and type of fibres, amount of stirrups and type of longitudinal reinforcement (prestressed or non-prestressed).
Written on 19 août 2011.
No abstract
Written on 19 août 2011.
Jiri Strasky, Technical University of Brno, and Strasky Husty and Partners, Brno, Czech Republic The idea of prestressing - a product of the twentieth century - has announced the single most significant new direction in structural engineering of any period in history. It put into the hands of the designer an ability to control structural behaviour and, at the same time, it enabled the designer - or forced the designer - to think more deeply about the construction. Moreover, the idea of prestressing opened up new possibilities for a form that influences the general culture. To focus on that fact, and to narrow the scope, the paper will consider bridges only, even though prestressing has broad applications to all kinds of buildings. However, the idea of prestressing arose out of bridge design, and its most impressive forms, from a purely engineering viewpoint, have appeared in bridges.
Written on 19 août 2011.
Rajaiah Selvaraj, Central Electrochemical Research Institute, Tamilnadu, India Srinivasan Muralidharan, Central Electrochemical Research Institute, Tamilnadu, India Seshadri Srinivasan, Central Electrochemical Research Institute, Tamilnadu, India The effect of silica fume in concrete is reviewed from the point of view of chloride diffusion, carbonation, oxygen diffusion, the pH of the pore solution and electrical resistivity, as they are the main parameters influencing the corrosion phenomenon in concrete.
Written on 19 août 2011.
Niels C. Lind, University of Waterloo, Canada Structural safety is a part of general safety in a society. Safety factors should conform to a general rationale for all life safety. Two rationales are presented here, using a principle of time economy and using social indicators. The common-sense time principle of risk management states that a `life-saving' alternative, if it is truly to save lives, should return to the community more years of life in good health than the years of work consumed to pay for its cost. Alternatively, a risk acceptability criterion can be derived from a compound social indicator that reflects general benefit to society and that is a function of gross domestic product and life expectancy. To be acceptable, alternatives should increase the social indicator. The two compound social indicators, the Life Quality Index and the Human Development Index, yield practically identical criteria for risk acceptance.
Written on 19 août 2011.
A. H. J. M. Vervuurt, TNO Building and Construction Research, the Netherlands N. Kaptijn, Dutch Ministry of Transport and Public Works W. B. Grundlehner, Spanstaal BV, the Netherlands In mid-2001 the final two bridges over the River Dintelhaven in the harbour area of Rotterdam were put into use. Both bridges are concrete box girder bridges and have been erected using the balanced cantilever method. In the first bridge, with a main span of about 185 m, four (external) tendons each with 91 carbon fibre reinforced wires (5 mm diameter) have been applied next to conventional steel tendons. The project is the result of an initiative that was started in 1994 by the Civil Engineering Division of the Dutch Ministry of Transport and Public Works and the CUR (Dutch Centre for Civil Engineering Research and Codes). In order to guide the activities, with regard to the application of the carbon fibre reinforced plastic (CFRP) tendons in the Dintelhaven Bridge, experiments were carried out at TNO Building and Construction Research, focussing upon the long- and short-term behaviour of the CFRP wires and tendons. In this paper the results of these tests are presented. Moreover, in the paper, attention is paid to the manufacturing of the tendons, as well as the installation of the tendons in the bridge.
Written on 02 mai 2011.
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