News - fib International

Structural Concrete, Vol. 10, no. 2, June 2009

19.08.2011 News

S. L. Matthews, Building Research Establishment, UKJ. Jacobs, Technial Approvals and Standardisation Division, BBRI, BelgiumI. Stipanovic Oslakovic, Civil Engineering Institute of Croatia, Zagreb, CroatiaD. J. Cleland, Queen's University, Belfast, UKWith correct design, specification and construction, concrete structures provide high-performance durable assets with long service lives. Owners can maximise the benefits to be gained from concrete structures, while minimising through-life cost and sustainability impacts, by taking a through-life perspective on the design, specification and management of their structures; rather than simply focusing on first cost. This first part of a two-part paper provides an overview of the advice given in the fib guide to good practice entitled Concrete Structure Management - Guide to Ownership and Good Practice (fib Bulletin 44): the paper deals with general issues associated with concrete structure ownership, giving owners an insight into their responsibilities and obligations, what they should do and seek to achieve in the context of concrete structure management, and information regarding potential deterioration mechanisms and the merits of adopting proactive as opposed to reactive structure management. 

Structural Concrete, Vol. 10, no. 2, June 2009

19.08.2011 News

W. Raphael, École Supérieure d'Ingénieurs de Beyrouth, St. Joseph Univeristy, Riad El Solh Beirut, LebanonR. Faddoul, École Supérieure d'Ingénieurs de Beyrouth, St. Joseph Univeristy, Riad El Solh Beirut, LebanonD. El-Asmar Selouan, École Supérieure d'Ingénieurs de Beyrouth, St. Joseph Univeristy, Riad El Solh Beirut, LebanonA. Chateauneuf, LGC-UBP Polytech Clermont Ferrand, Aubière, FranceThe disparity between theoretical and experimental results reveals that the creep of concrete is often underestimated by most, if not all, codes of design; this is particularly true in the case of Eurocode 2. Thus it is necessary to calibrate the present code models. Bayesian-type inferences turn out to be an especially suitable tool for the work needed in revising and updating design codes. This is by virtue of their capability to incorporate additional information resulting from current practice and research so as to improve existing models. In this paper, corrective coefficients are proposed for the Eurocode model, allowing better estimation of the long-term creep of concrete. To achieve this aim, the authors rely on a large database of experimental results compiled by collecting data from several research institutions in Europe. Two descriptive statistical methods are applied in order to compare the experimental results from the above-mentioned database with results calculated using the Eurocode 2 model for the same input parameters. A Bayesian-type statistical inference is then performed to evaluate the corrective coefficient for different categories of concrete strengths using various prior distributions. The approach presented here has proven to be an effective and systematic framework for the consideration of all possible types of uncertainties in model calibration. The results obtained are very interesting for engineers involved in design and supervision of structures. The adoption of such a design approach would improve long-term serviceability of structures subjected to creep. 

Structural Concrete, Vol. 10, no. 2, June 2009

19.08.2011 News

E. Oller Ibars, Civil Engineering School, Technical University of Catalonia, Barcelona, SpainD. Cobo del Arco, Tec-Cuatro, SA, Barcelona, SpainA. R. Marí Bernat, School of Civil Engineering, Technical University of Catalonia, Barcelona, SpainExisting experimental research has shown that the application of externally bonded laminates to strengthen reinforced concrete (RC) structures can lead to brittle failures involving debonding of the laminate before the design load is reached and a classical failure mode occurs. In an externally bonded RC beam, this peeling failure can initiate either near mid-span owing to the effects of flexural or shear cracks, or at the laminate end as a result of stress concentration at the laminate cut-off point. The design procedure to obtain the laminate area to strengthen a RC element should avoid these premature peeling failures. Therefore, there is a need to understand the mechanics of the laminate debonding process in order to prevent it. The evolution of the debonding process can be analysed by using non-linear fracture mechanics assuming a bilinear constitutive law for the interface. The crack propagation process is described through the evolution of different stages, in which the interfacial shear stresses can be obtained. As the transfer of stresses from laminate to concrete through the interface is a critical parameter in the correct performance of externally bonded structures, the transferred force should be limited to a maximum value in order to prevent peeling failure. A shear-bending interaction diagram based on this maximum transferred force associated with peeling failure is the main point of the design proposal presented in this paper. 

Structural Concrete, Vol. 10, no. 1, March 2009

19.08.2011 News

Structural Concrete, Vol. 10, no. 1, March 2009

19.08.2011 News

H. Y. Leung, Hong Kong College of Technology, Hong KongA. Nadeem, Hong Kong College of Technology, Hong KongG. K. W. Tse, Hong Kong College of Technology, Hong KongThis paper examines the water permeability and chloride penetrability of self-compacting concrete with fly ash and silica fume as admixtures. The influence of 28-day concrete strength on concrete permeability is also investigated. It was found that addition of fly ash and silica fume was effective in reducing the concrete permeability. Most self-compacting concrete specimens showed low to very low water permeability and chloride penetrability. Test results also indicated that the 28-day concrete strength should not be used as an indicator for concrete permeability.

Structural Concrete, Vol. 10, no. 1, March 2009

19.08.2011 News

S. Hetland, Aker Solutions, Lysaker, NorwaySakhalin II is an integrated oil and gas development in the Russian Far East. It involves the installation of a large offshore platform at the Piltun sector of the Piltun-Astoskhskoye field (PA-B) and a single large platform at the Lunskoye gas field (LUN-A). These platforms, together with the existing Molikpaq drilling and production platform, are equipped to export their output by pipeline to Sakhalin. From here it is transported by way of an onshore link of 800 km to Prigorodnoye, Aniva Bay at the south of the island, which is the location for a major liquefied natural gas (LNG) storage facility and terminal, and oil handling terminal. The two fields contain an estimated 1.2 billion barrels (190 000 000 m3) of crude oil and 500 billion m3 of natural gas. Output is scheduled at up to 9.6 million of LNG per year and about 180 000 barrels per day (29 000 m3/day) of oil. The project partners are Gazprom (50% plus one share), Shell (27.5%), Mitsui (12.5%) and Mitsubishi (10%). The GBS contracts were issued on 1 July 2003 and both platforms were installed during the summer of 2005. 

Structural Concrete, Vol. 10, no. 1, March 2009

19.08.2011 News

Structural Concrete, Vol. 10, no. 1, March 2009

19.08.2011 News

M. Taliano, Politecnico di Torino, Italy This paper reports the main results of a parametric analysis which is based on the calculation of stresses on concrete and steel of r.c. rectangular sections subjected to bending under quasi-permanent and characteristic loads. Two calculation methods are used: a general method and a simplified one, namely the n-method. The main parameters that influence the calculation of stresses are then discussed and the differences that are produced by the n-method using the classical values found in the literature compared with the general method are evaluated. By varying only some of the involved parameters, appropriate new values of the modular ratio, called 'improved modular ratios', are determined and two equations for the assessment of the improved modular ratios are proposed, one for each considered load combination. In this way, applying the 'improved' n-method, it is possible to calculate the stresses on concrete and steel with good accuracy. 

Structural Concrete, Vol. 9, no. 4, December 2008

19.08.2011 News

G. Morgenthal, Principal Engineer, Maunsell AECOM, Shatin, Hong KongR. Sham, Executive Director, Maunsell AECOM, Shatin, Hong Kong K. Yamane, Engineering Manager, Maeda-Hitachi-Yokogawa-Hsin Chong Joint Venture One of the most challenging aspects in the construction of Stonecutters Bridge, Hong Kong, was the erection of the concrete backspan structures. At a height of about 70 m a geometrically complex grillage deck was to be constructed. The superstructure cannot support its own weight before the stay cables are installed; it was thus constructed on a unique falsework system required until stressing of the stays. The paper describes the development of the construction procedures, the construction engineering and the design of the temporary works. The work involved the accurate stage-by-stage modelling of the entire construction process to assess the structural adequacy throughout and to facilitate geometry control. The different strands of work were highly interactive and optimised erection methodologies, developed together with the contractor, led to a successful implementation of the project. 