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This paper presents an experimental research program aiming at assessing the current code provisions of vmin. A large test series was carried out, by varying the reinforcement ratio and loading conditions, the minimum average shear stress that can cause shear failure of a specimen with different depth, concrete strength is determined. The three test series cover two types of concrete mixtures and a moderate structure depth range. In addition, the Eurocode and ModelCode 2010 provisions on vmin are discussed. They are compared with the test results. Recommendations on the present code expression are given.

A majority of the bridges and viaducts in the Netherlands were built in the sixties and seventies of the last century and many of them will need to be replaced in the near future due to technical or functional reasons. This is a replacement issue, faced by many countries worldwide. But what about the concrete structures? Should we replace them with the same structural systems and by using the same conventional concrete as used before? Or do we apply the newly developed concrete types, such as Ultra High Performance Concrete (UHPC) and Strain Hardening Cementitious Composites (SHCC) and install them with structural health monitoring techniques? In the paper the findings of several exploratory studies, performed at Delft University of Technology, are presented. In general, but especially for the replacement of existing structures, there is a tendency for increasing the slenderness of the concrete structures. In tenders it is even seen that contractors can get an increased bonus when building with reduced heights. A driving force is the fact that piers in roads are highly undesirable (freedom in space), while, in order to reduce additional costs, the new bridge should stay aligned with the existing roads. Most of the existing viaducts in the Netherlands are three or four span plate bridges with a total span between 20 and 60 m. Is it feasible to replace these by single span bridges with slenderness as high as 60? In a feasibility study, the possibilities for this are investigated and steps to be made are addressed. The exploratory study focuses on long, slender concrete structures, which can be obtained by applying Advanced Cementitious Materials (ACMs) while furthermore new building methods are explored. In general, the idea is to make steps towards our future SMART bridges for which structural health monitoring, sustainability, no hinder, zeroenergy, no maintenance and aesthetics are keywords.

Blast furnace slag cement (BFSC) has been used in reinforced concrete structures in marine and road environment in The Netherlands for nearly a century. Experience is good and long service lives can be obtained. In Norway experience with BFSC is scarce. In The Netherlands, a high resistance against chloride penetration and a high electrical resistivity, was demonstrated both in the field and in the laboratory for CEM III/B with 65-75% of slag by mass of binder. Such a cement is not readily available on the Norwegian market. The introduction of CEM III/A with c. 50% slag is anticipated. An experimental program was carried out to study the properties of five mortar mixes made with: CEM III/B (two brands); a CEM III/A (with c. 50% slag) with silica fume; and a CEM I and a CEM II/A-V (fly ash cement), both with silica fume. Rapid Chloride Migration (RCM) and electrical resistivity were tested at ages between two days and one year. RCM values showed consistent decrease and resistivity showed consistent increase between two days and one year. The program is intended to collect data up to three years age. The ultimate goal is to provide a basis for evaluating the use of slag cement in Norway for durable concrete structures. The paper reports the results and discusses the preliminary conclusions

A fully triaxial material model for concrete was implemented in a commercial finite element code. The only required input parameter was the cylinder compressive strength. The material model was suitable for non-linear finite element analyses of large concrete structures. The importance of including a crack closure algorithm was demonstrated on a case involving sequential loading. Bayesian inference was applied to results from a series of benchmark analyses, and the results indicate that the modelling uncertainty can be represented by a log-normal variable with a mean 1.10 and a coefficient of variation of 10.9%.

As the bridge stock in The Netherlands and Europe is ageing, various methods to analyse existing bridges are bemg studied. Proof loading of bridges is an option to study the capacity when crucial information about the structure is lacking. This information could be related to the material (for example, the effect of alkali-silica reaction on the structural capacity) as well as to the structiu-al system (for example, the effect of restraints at the supports or transverse redistribution capacity). When it is decided to proof load a bridge, the question arises which maximum load should be attained diuing the experiment to approve the capacity of tiie bridge, and which criteria, based on the measiurements during the test, would indicate that the proof loading needs to be aborted before reaching the maximum desired load (the so-called stop criteria). To defme the requked loading criteria, a review of the literature has been made, finite element models of existing viaducts have been made, and on tiiese viaducts, proof loading tests have been carried out. These bridges were heavily instrumented, with a goal of leaming as much as possible about the structural behaviour during proof loading. As a result of the analysis and experiments, recommendations are given for proof loading of bridges with respect to the required maximum load and the stop criteria. These recommendations are important, since they form the basis of a guideline for proof loading of existing concrete bridges that is under development in The Netherlands.