fib Directory 2023
07.06.2023 fib-news
The fib Directory 2023 is now available for download!
Read morefib-news
Structural Concrete, Vol. 11, no. 2, June 2010
19.08.2011 fib-news
S. Leivestad, Standards NorwayJ. Mehus, Standards NorwayStandards are a system of tools that should be recognised by all the stakeholders in the construction industry and be used as the instrument that can provide structures that meet all societal expectations: safety, cost-effectiveness and sustainability.
Read moreStructural Concrete, Vol. 11, no. 1, March 2010
19.08.2011 fib-news
S. Helland, Skanska Norge AS, NorwayR. Aarstein, Rakon AS, NorwayM. Maage, Skanska Norge AS, NorwaySince 1973 a total of 34 platforms for the oil and gas industry, representing 2 650 000 m3 high-strength concrete/high-performance concrete, have been installed in the North Sea. The structures have been closely monitored by the operating companies with regard to their in-field performance. This paper analyses chloride profiles from some 180 cores taken from ten structures after 2-26 years service. The profiles are applied to assess the remaining service life by modelling. Based on this, the remaining service life as a function of reliability for not passing a critical chloride content at the reinforcement, is directly quantified. The findings are compared with the requirements given in the present Norwegian standards for concrete works exposed to a harsh marine environment.
Read moreStructural Concrete, Vol. 10, no. 3, September 2009
19.08.2011 fib-news
L. da Conceição Domingues Shehata, Universidade Federal Fluminense, Niteroi, BrazilA. Lopes de Paula, Engevix, Rio de Janeiro, BrazilI. Abd El Malik Shehata, COPPE - Universidade Federal do Rio de Janeiro, Rio de Janeiro, BrazilThe use of high-strength concrete (HSC) is more advantageous in structural elements under compression and the compressive stress-strain relationship is a relevant characteristic of the concrete required for behaviour analysis and design of those elements. For cross-section design, the codes of practice usually allow curved-rectangular and/or simplified rectangular idealised concrete stress blocks. Comparisons between idealised concrete stress blocks of different codes are presented and examples of their influence on the cross-section theoretical axial load-bending moment interaction diagram are given in this paper. The theoretical strengths obtained considering those compressive stress diagrams for the concrete are compared with experimental strengths of 403 elements subjected to pure axial load or to combined axial load and bending moment. Besides the cross-section type (square or rectangular), the elements had the variables of dimensions, steel and concrete strengths, load eccentricity and reinforcement ratios and configuration. The analysis of the comparisons between experimental and theoretical strengths considering different stress diagrams for the concrete under compression provides an insight to the level of safety related to the different design procedures, which is highly relevant for those who want to design HSC structures.
Read moreStructural Concrete, Vol. 8, no. 3, September 2007
19.08.2011 fib-news
E.G. Burdette, University of Tennessee, Knoxville, USAS.C. Howard, University of Tennessee, Knoxville, USA J.H. Deatherage, University of Tennessee, Knoxville, USAD.W. Goodpasture, University of Tennessee, Knoxville, USAThe Tennessee Department of Transportation (TDOT) in the United States has become the national leader in the design and construction of jointless bridges with abutments which are integral with the bridge deck. While TDOT criteria call for limits of length of 152 m (500 ft) and 244 m (800 ft) for steel and concrete bridges, respectively, they have on more than one occasion exceeded these limits significantly. TDOT's desire to address any questions raised about the efficacy of using prestressed concrete piles to support integral abutments and perhaps to extend the limits on bridge length led to the tests reported in this paper. Four full-size abutments, 3.05 m (10 ft) wide, were built and tested in the field. The description and results of these tests are reported and discussed. Of particular interest are the testing of one pile to failure and the cyclic tests performed on one pile. The conclusions drawn were, first, that prestressed concrete piles are appropriate to use to support integral abutments and, second, that the TDOT criteria for bridge lengths are reasonable and conservative.
Read moreStructural Concrete, Vol. 7, no. 3, September 2006
19.08.2011 fib-news
N. De Belie, Ghent University, BelgiumW. De Muynck, Ghent University, BelgiumW. Verstraete, Ghent University, BelgiumBiological techniques for cleaning and repair of concrete and stone can be an ecological alternative to traditional conservation techniques. Weathered concrete samples fouled by lichens were treated with Thiobacillus bacteria and an appropriate nutrient, by submersion or sprinkling. The general effect of cleaning was documented by the use of colorimetry and microscopy. For remediation of decayed concrete, biomineralisation of mortar samples of different porosity by ureolytic sludge was tested. For the most porous mortar samples and when urea, nutrient broth and an external calcium source were provided, the amount of water absorbed after 200 hours was decreased by a factor of five compared to untreated samples. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed a dense layer of calcite and vaterite crystals.
Read moreStructural Concrete, Vol. 6, no. 1, March 2005
19.08.2011 fib-news
K. Neocleous, Centre for Cement and Concrete, University of Sheffield, UKK. Pilakoutas, Centre for Cement and Concrete, University of Sheffield, UKM. Guadagnini, Centre for Cement and Concrete, University of Sheffield, UKInnovations in concrete construction can be held back by the inability of codes of practice to accommodate new materials. The current design and safety philosophy (DSP) of reinforced concrete relies heavily on the properties of steel reinforcement. The need to embrace new materials, such as fibre-reinforced polymer (FRP) reinforcement, led to an in-depth examination of the DSP of European concrete codes of practice and resulted in a new philosophy, presented in this paper. The basis of the new philosophy remains the limit-state design and achievement of target notional structural reliability levels, but aims at the attainment of a desired failure mode hierarchy. The implementation of the philosophy, through a proposed framework, utilises the concept of average measure of closeness for the determination of appropriate material partial safety factors. An example of the application of the proposed framework is presented for FRP reinforcement.
Read moreStructural Concrete, Vol. 5, no. 3, September 2004
19.08.2011 fib-news
A. El-Nabawy Atta, Tanta University, EgyptS. El-Din Fahmy Taher, Tanta University, EgyptA.-H. A. Khalil, Tanta University, EgyptS. E. El-Metwally, Tanta University, EgyptDesign provisions of many international codes for beam-column joints are limited to ordinary-strength concrete. The experimental work presented in Part I of the paper (Structural Concrete, 2003, 4, No. 4, 175-183) has indicated a significant difference in behaviour of normal concrete joints from those made of hybrid or monolithic high-strength concrete joints. To conduct an extensive parametric study, a non-linear, three-dimensional finiteelement analysis was carried out for external reinforced concrete type-1 joints under quasi-static monotonic loading. The computational model has been verified and validated against several experimental tests. The numerical work was aimed at providing more insight about the behaviour and determining the fundamental mechanisms of load transfer within the joint. The basic parameters included the effects of geometrical aspects as well as the amounts of reinforcement and detailing in column, girder and joint. Furthermore, the strength parameters, existence of axial column load, presence of vertical haunches and the restraining effects by transverse elements have been considered in the analysis. The present study indicated that the modes of failure and shear behaviour of high-strength concrete connections behaved differently from normal-strength concrete connections at various axial loading levels.
Read moreStructural Concrete, Vol. 5, no. 2, June 2004
19.08.2011 fib-news
P. J. Nixon, Centre for Concrete Construction, Building Research EstablishmentK. Quillin, Centre for Concrete Construction, Building Research EstablishmentG. Somerville, Associate, Building Research EstablishmentAs the premier construction material across the world, concrete has a major determining role on the effects, good or bad, of construction on the environment. Working towards a more sustainable form of concrete construction, within an overall strategy for more sustainable construction, can, therefore, have major environmental benefits. 'Sustainable concrete construction' is, however, a multi-faceted objective and demands many diverse approaches. This paper examines how the objectives and themes of sustainable concrete construction can be met by using the concepts of service life design.
Read moreStructural Concrete, Vol. 4, no. 4, December 2003
19.08.2011 fib-news
Mounir Khalil El Debs, University of Sao Paulo at Sao Carlos, Brazil Aline da Silva Ramos Barboza, Federal University of Alagoas, Brazil Anamaria Malachini Miotto, Tuiuti University of Parana, Brazil Bearing pads are used in precast concrete connections to provide a more uniform distribution of contact stresses over the bearing areas and to allow relative movements between precast concrete elements, in order to prevent cracking at the connection area. This paper presents the study of an alternative material made with styrene-butadiene latex modified on Portland cement mortar, polymeric fibres, and, eventually, lightweight aggregate (vermiculite). The developed material showed a good compression strength and low elasticity modulus. These characteristics make it suitable for use as bearing pads in precast concrete connections, such as beam-to-column connections or wall-to-wall connections. The paper shows the main characteristics of this material and the application and tests on: (a) beam-to-column connections and (b) samples that reproduce a wall-to-wall connection.
Read more