This paper presents the development of a mix design method for geopolymer mortar mixes with a principal focus on compressive strength. The method is based on the hypothesis that the overall strength of geopolymer mortar depends on the strength of the geopolymer binder materials, the packing density of the aggregates in the mortar and the amount of geopolymer binder. First, the strength of the binder was evaluated experimentally. Fly ash obtained from two different sources and ground granulated blast-furnace slag were used as the main ingredients in the production of the geopolymer binder. Correlation between the packing density of the aggregates in the mortar and their influence on the binder demand and compressive strength were investigated. Finally, a conceptual framework for a geopolymer mortar mix design approach is proposed. In addition to describing the mortar mix design methodology in a rational way, it is hypothesized that the approach can also be extended to the development of a geopolymer concrete mix.

Prestressing in flat slabs helps to control deformations and cracking under service loads and allows the required slab thickness to be reduced, thus leading to more slender structures and an economic solution for long spans. However, as a consequence of the limited thickness of these members, punching typically governs at the ultimate limit state. Studies of the punching shear strength have shown that the presence of prestressing in flat slabs has a number of potential beneficial effects, namely the vertical component (force) carried by inclined tendons, the in-plane compression stresses and the bending moments developed near the supported region. However, the approach provided by codes of practice for punching design in the presence of prestressing may differ significantly. Some codes neglect the influence of the bending moments introduced as a result of prestressing and the sections at which the deviation forces of the tendons are considered may be located at different distances from the edge of the supported region. The influence of prestressing on the punching shear strength of members without shear reinforcement is investigated in this paper by using the fundamentals of the critical shear crack theory. Using that as a basis, and also taking into account 65 tests available in the scientific literature, the suitability and accuracy of a number of design codes, e.g. Model Code 2010, Eurocode 2 and ACI 318-11, are investigated and compared.

A recycled aggregate concrete (RAC) with different replacement percentages of recycled coarse aggregates (RCAs) (i.e. 0, 30, 50, 70, 100%) was investigated experimentally at elevated temperatures. The residual compressive strength as well as the residual flexural strength of the RAC following elevated temperatures was studied and evaluated. A relationship between the residual compressive flexural strength of RAC and the elevated temperature was proposed. Furthermore, the relationship between the residual flexural strength and the compressive strength of the RAC was compared and analysed. It was found that both the residual compressive strength and the residual flexural strength of the RAC decrease with a rise in temperature, and the effect of the RCAs replacement percentage on the residual flexural strength and the residual compressive strength of RAC was found to be obvious.

This research study involves obtaining an analytical model for the perforation of unreinforced concrete targets by a hemispherical hard projectile. Dynamic cavity expansion theory and the reflection of compressive waves from the end of the concrete targets are used for developing the analytical model. The effect of the friction coefficient is also investigated in the analysis. Numerical modelling of the problem has been performed in LS-DYNA code for validating the analytical results. Johnson-Holmquist concrete and rigid material models have been employed for the concrete and the projectile respectively. The impact velocity range considered in this work is between 250 and 850 m/s. No projectile erosion is considered in this range. The analytical results have been compared with numerical results and show good agreement with numerical simulations.

• 2013 fib symposium in Tel Aviv: Engineering a Concrete Future
• 2013 fib Medal of Merit and Honorary Membership
• 2013 Achievement Award for Young Engineers
• fibUK meeting
• Advances in Cement and Concrete Technology in Africa (ACCTA)
• Report from the Norwegian fib Member Group)
• Congresses and symposia

No short description available.

No short description available.

No short description available.

The Model Code for Concrete Structures 2010 is a recommendation for the design of structural concrete, written with the intention of giving guidance for future codes. As such, the results of the newest research and development work are used to generate recommendations for structural concrete at the level of the latest state of the art. While carrying out this exercise, areas are inevitably found where information is insufficient, thus inviting further study. This paper begins with a brief introduction to the new expertise and ideas implemented in fib Model Code 2010, followed by a treatment of areas where knowledge appeared to be insufficient or even lacking and where further research might be useful.

CEB/FIP Model Code 1990 (MC-1990) did represent the technology and focus some 20 years ago. However, it soon became evident that the document had some notable lacunas. In 1995 the general assemblies of the two organizations endorsed CEB/FIP bulletin No. 228, extensions to MC 1990 for high-strength concrete, and in 2000 a similar extension to MC 1990 for lightweight aggregate concrete as bulletin No. 4.
The fib approved bulletin No. 34 Model Code for Service Life Design (MC SLD) in 2006. All these three additions have since matured and are now incorporated in the new fib Model Code for Concrete Structures 2010 (MC-2010).
The main purpose of an fib Model Code is to act as a model for operational standards. The obvious counterpart for a body such as fib operating worldwide is ISO. The initiative taken by MC SLD has therefore further matured in ISO TC-71/SC-3/WG-4 and it was accepted as ISO 16204 “Durability - Service Life Design of Concrete Structures” during the summer of 2012.
According to the obligations given in the WTO Agreement on Technical Barriers to Trade, it is hoped that these principles will be further implemented in national and regional standards.
This article describes the need for a transparent methodology when dealing with service life design, and the process - originating from a group of enthusiasts one decade ago - through fib and finally reaching international consensus in ISO.

The fib Model Code 2010 for Concrete Structures introduces numerical simulation as a new tool for designing reinforced concrete structures. The model of resistance based on non-linear analysis requires adequate model validation and a global safety format for verifying designs. The numerical simulations combined with random sampling offer the chance of an advanced safety assessment. Approximate methods of global safety assessment are discussed and compared in a case study. An example of a bridge design supported by non-linear analysis is shown.

Semi-probabilistic safety formats for the non-linear analysis of reinforced concrete structures are of practical interest for structural designers. The safety format proposed in EN 1992-2 enables a safety assessment through a non-linear structural analysis and the application of a global safety factor, which is defined as the ratio between the representative and design values of the material resistances. A more realistic estimate of the global safety factor can be obtained from the distribution of the structural response. This paper proposes a safety format based on the mean values of the material resistances and a global resistance factor. Its practical application in the structural design of concrete beams and columns is also presented.

Concrete shells have been widely used in the past as economical and suitable solutions for a number of structures such as roofs, silos, cooling towers and offshore platforms. Taking advantage of their single or double curvature, bending moments and shear forces are limited, and the structures develop mostly membrane (in-plane) forces, allowing them to span large distances with limited thicknesses (typically just a few centimetres). In recent decades, advances in numerical modelling, formwork erection and concrete technology have opened up a new set of possibilities for the use of concrete shells. This paper describes the design and construction of a shell in the form of an ellipsoid (93 × 52 × 22 m) and with thickness varying between 100 and 120 mm. The shell was built using sprayed concrete and also ordinary concrete in some regions. A number of tailored solutions were also adopted, such as post-tensioning, addition of fibres and shear studs, to ensure satisfactory performance at both the serviceability and ultimate limit states.

The lattice equivalent continuum model (LECM) has proved to be very effective in analysing reinforced concrete structures in two-dimensional cases. That model is extended here to three dimensions and is fitted to a finite element formulation for analysing three-dimensional reinforced concrete structures. In any of the three principal directions, the stress-strain behaviour of concrete will be affected by the stress state in the other two directions. Consequently, stress-strain curves for concrete will shift from a uniaxial pattern. This phenomenon is considered in this work by selecting concrete peak stresses in three alternative approaches. The effectiveness of those approaches is also evaluated. The results of the calculations show good reproduction of the test data, which indicates the validity of this proposed 3D modelling of reinforced concrete.

Eight sets of large, circular, short reinforced concrete columns were tested under monotonic axial compression. The primary variables are type of transverse reinforcement (spiral vs. circular tie), type of splice, end hook length and staggered length of adjacent circular ties. The tests confirmed the acceptable performance of the circular tie newly proposed in ACI 318M-11. In addition, the circular tie scheme in which the ends terminate with hooks that engage with a longitudinal steel bar and bend into the concrete core is acceptable for performance and ease of construction. The effectiveness of its end hook length and the staggered length of adjacent circular ties is also investigated.

This article describes an experimental programme aimed at studying the effect of cover, ratio between diameter and effective reinforcement ratio (&phgr;/&rgr;s, ef) and the influence of stirrup spacing on the cracking behaviour of reinforced concrete elements. The experimental programme was conceived in order to contribute to the debate - fuelled by the publication in recent years of Eurocode 2 EN1992-1-1 and the revision of the Model Code under way when the tests were carried out (and now published as a finalized document) - regarding the influence of these parameters on cracking. Important theoretical aspects are discussed, including where the crack width is estimated by current code formulations and what relevance this may have on the correlation between crack opening and durability of RC structures, especially with regard to structures with large covers. The effect of stirrup spacing, a variable absent from current codes, is also discussed.

fib-days in Chennai, India
fibUK Technical Meeting in recognition of Andrew Beeby
Design of Concrete Bridges: fib short course in Ankara, Turkey
New fib officers
Gordon Clark visits Japan
Short notes
Congresses and symposia
fib membership benefits
Acknowledgement

No short description available.

No short description available.

A two-dimensional simulation of concrete behaviour using the discrete element method (DEM) is presented in this work. The main aim of this paper is the modelling of the failure process and crack initiation. The failure process of a concrete prism during a compression test is simulated. A substructure representing the concrete components - aggregate and cement matrix - is introduced. It is shown that convex and concave concrete specimens can be treated, whereas the particle geometry always remains convex. The crack patterns of the concrete specimens resulting from the simulation are shown and compared with laboratory experiments. It is shown that the calculated peak load does not depend on the particle number used in the simulation. The ratio of lateral strain to longitudinal strain of the concrete specimen during load application is simulated and compared with experimental results.

This work investigates the effect of olive waste ash (OWA) on the durability of concrete exposed to alkali-silica reaction (ASR). Three OWA contents were considered in the work: 7, 15 and 22 %, with crushed Pyrex glass used as reactive fine aggregate. The other experimental parameters investigated in the study were: w/c ratio (0.4 and 0.5) and air content (non-air-entrained and air-entrained). The OWA concrete specimens were submerged in 1-N NaOH solution at 40 °C to accelerate the ASR. The ASR damage was monitored by measuring the expansion of concrete prisms and the decrease in compressive strength.
The study demonstrates that OWA concrete is more resistant to ASR deterioration than plain concrete. The durability of OWA concrete with respect to ASR damage improved with the increase in OWA content. The OWA concrete with a w/c ratio of 0.4 exhibited a better performance with respect to ASR deterioration than the OWA concrete with a w/c ratio of 0.5. The air-entrained OWA concrete exhibited better durability with respect to ASR damage than the non-air-entrained OWA concrete.

Spatial and temporal temperature variations in a concrete structure due to variations in the surrounding climate will produce movements which, if restrained, may induce stresses in the structure. To get a better understanding of transverse thermal stresses due to climatic effects in concrete box cross-sections, the FE simulations in this study have been performed using extensive climatic input data directly or by using simplified methods to simulate the temperature and resulting stress fields in a section of the hollow concrete arch of the New Svinesund Bridge. Studies of other cross-sections with varying depth, width and wall thicknesses have also been performed to investigate the geometrical influence. The results reveal an overestimation of the maximum thermal tensile stress when using a linear temperature differential approach compared with the direct use of climate data that includes the non-linear part of the temperature distribution. The effect of depth, width and orientation is negligible compared with variations in thickness between slabs and walls. For box sections with slabs/walls having different thicknesses, the transverse thermal stresses will be significantly larger in the thinner members, irrespective of the actual orientation and position of the member.

Vertical and differential deformations in super-high-rise buildings are extremely important during construction. In order to be able to adjust the construction process accurately, taking the deformations into account, such deformations must be calculated exactly. The analysis of the vertical deformations of the high-rise Shanghai World Financial Centre building is illustrated in this paper. The prediction models of CEB-FIP 90 are used for calculating shrinkage and creep. The fictitious degree of hydration method has been applied for calculating the creep behaviour of the early-age concrete. The influence of steel bars on the vertical deformations has been analysed based on the macroscopical modulus method. Calculation of the vertical deformations includes the pre-construction and the post-construction deformations. Finally, the differential deformation between the concrete and the mega-structure column is determined. Theoretical results for the vertical displacement of this super-high-rise building agree very well with field monitoring data.

Nowadays, it is more and more often necessary to design two-dimensional reinforced concrete elements to satisfy both architectural demands and to comply with traffic safety requirements in the design of road and railway infrastructures. In fact, the demand for non-regular structural geometry is increasing in both cases.
As a consequence, the use of finite element analyses to model structures and calculate internal actions is constantly growing because closed-form solutions are generally unavailable for irregular shapes. Therefore, the problem of reinforcement design needs our attention because steel bars, in general, should be placed in non-orthogonal directions and can vary over the structure.
Consequently, there are two different kinds of design problem: choice of reinforcement direction and evaluation of the reinforcement ratio between the chosen directions, with the aim of minimizing the total amount.
Such problems can be easily overcome by generalizing a mechanical model consolidated in the literature for orthogonal reinforcement for skew directions. The model is set up according to the ultimate plastic behaviour of the elements. An optimization technique based on genetic algorithms is then applied to the new model to reduce the amount of reinforcement.
This paper describes both the ultimate resisting mechanism with generic reinforcement directions and the way genetic algorithms are employed to optimize the amount of reinforcement.

Call for entries: 2014 fib Awards for Outstanding Concrete Structures
fib 2013 Symposium, Tel Aviv
Commission 9 update
70th birthday symposium for Rolf Eligehausen
BEFIB2012 - An overview
Symposium for Joost Walraven
fib bulletins
Walter Thorpe † 1928-2012
Congresses and symposia
Acknowledgement
2012 reviewers