Partial Factor Format Research Articles

Adaptive Estimation of the <i>In Situ</i> Characteristic Concrete Strength

For calculation of existing concrete structures on the basis of the partial factor format, the main representative value is the actual in-situ characteristic value of the concrete strength. When samples are tested, the concrete in-situ strength of the structure shall be determined, statistically if possible, from the test results. In accordance with EN 1990 the 5% percentile value is calculated on the basis of a unilaterally limited constant confidence level. It was found the in some case, estimation of the in-situ characteristic concrete strength taking a constant confidence level does not allow to adequately assess the reliability of the existing structures. A new estimator based on non-parametric statistical method was proposed for estimating of the in-situ characteristic concrete strength with a given arbitrary confidence level. The procedure that was proposed allows one to re-establish of the estimator pdf even with a very limited sample size. It is established, that the choice of the confidence level of the estimator should be based on the average reliability of the structure.

Safety Factors for Assessment of Existing Structures

Current structural codes have been developed mainly for new design and are not efficient for assessment because of significant differences between these situations. One of the main differences is the possibility to update information about an existing structure. This paper proposes a way in which updating can be taken into account when developing code safety formats (partial factor and load and resistance factor design). Updating information about individual structural properties such as material strengths by carrying out on-site inspections is discussed. Uncertainties associated with on-site testing including “model” uncertainty are considered and a method for treating these uncertainties in the context of the partial factor format is described. Results indicate that “model” uncertainty may have a significant effect on partial factors. Furthermore, we consider updating information about the resistance of the whole structure by proof load testing or by taking into account the previous safe performance of ...

Modern structural design codes

In this paper from the UK Building Research Establishment the authors suggest that a simple partial factor format is a practical alternative to the more complex formats of many national and international code drafts currently in preparation. The role of codes of practice within the overall structure of building control is also discussed. It is argued that any format of practical value must accord with our current state of knowledge of structural behaviour, which is limited. The partial factors used must be unambiguously defined, and must further be capable of rational evaluation. These criteria themselves tend to produce a simple format.