Assessment of consequence class two (CC2) buildings

Abstract

Numerous structural failure incidents have occurred in the past years. It was found that current methods, such as NEN 2767, fall short in guaranteeing the structural safety of existing buildings. Although structural failure incidents infrequently result in casualties, there are also social and economic consequences that impact both building user as owner. Interviewed asset managers have noted that the current lack of insight into a building’s structural condition often leads to preventable maintenance and repair costs, and safety risks. When coupled with changes in the outdoor and built environment, such as a focus of continuity in use, these risks become increasingly challenging for owners to manage.
To ensure structural safety of significant public buildings within CC3, mandatory assessment via NTA 8790 must be performed. However, this method is exclusively tailored to CC3 buildings and only considers potential casualties as risk consequences. This strategy neglects CC2 buildings and other potential consequences, exposing them to elevated risks due to a lack of insight into their structural conditions. All the asset managers interviewed for this study, all managing CC2 buildings, reported these issues.
The goal of this thesis is to develop an efficient and effective assessment method to evaluate existing consequence class two buildings on structural safety to prevent incidents with structural failures. As a start (CC2) building typologies within the Netherlands were examined to determine the typologies for which the method should be optimised. Subsequently, structural failure incidents were analysed, resulting in a list of common causes that should be considered during the assessment. However, due to limited data availability, expert interviews and general literature this list is not exhaustive but rather an initial attempt. It can serve as a focus during the assessment but should not be solely relied upon. Finally, existing assessment methods were evaluated based on trustworthiness, effectiveness and efficiency. The findings from this evaluation have been incorporated into the development of an efficient and effective assessment process, which is described in the document.
The assessment process developed in this study was validated by applying it to two existing buildings, leading to the following conclusions. The assessment process developed in this study has proven effective in evaluating the structural safety of CC2 buildings, thereby preventing incidents relating to structural failures. While the necessity for comprehensive risk analyses does impact the time required for the assessment, these analyses have been optimised to concentrate on the most critical aspects. Along with other efficiency-enhancing aspects, it presents an efficient method within the parameters of effectivity and trustworthiness.
However, as revealed during validation, not all deficiencies can be detected using this method. There will always be hidden deficiencies that remain undetected and assessors are made aware of this limitation. Despite this constraint, the method provides an efficient and effective evaluation of the structural safety of existing buildings.