1. Introduction
The ‘Reference Approach’ is a method that aims to utilize the vast knowledge, expertise, and database of VIIA in the seismic analysis of buildings in Groningen region. For the past couple of years VIIA has performed several advanced analyses in finite element software such as Non-linear time history analysis (NLTH) and Non-linear push over analysis (NLPO) to assess the seismic capacity of various buildings. The Reference Approach leverages this experience to make reliable and quick seismic assessment of buildings by referencing documented outputs of FEA, simplified calculations pertaining to NPR9998:2020 [RA3], knowledge of typical construction in Groningen and expertise of lead engineers. The advantage of this method is it enables assessing buildings with the quality of a FEA without performing one. Thus, minimizing the required duration of analysis to a maximum of 2 weeks.
The core workflow of the process focuses on relevant failure mechanisms of the load bearing and stability system (PSSEs) as well as non-structural elements (NSCEs) of the building. The considered failure mechanisms for PSSEs are in-plane failure of walls, out-of-plane failure of walls, in-plane shear failure of floors and roofs, failure of connections and failure of foundation. For NSCEs, these failure mechanisms apply as well. However, the assessment procedure stated in the NPR9998:2020 [RA3] for NSCEs is followed.
In the early stage, the expected behaviour of the building is outlined. During this stage, critical or governing elements with respect to each failure mechanism are identified. Critical elements are those expected to fail. The idea is by validating a few critical elements it is possible to validate or extend the conclusion that the remaining elements of the building will be safe. Further explanation of this is given in this section.
Subsequently, when it comes to validating the critical PSSEs, the method is as follows:
By primarily utilising results of previous NLTH analysis of similar buildings:
Reference based NLTH: REF-NLTH, uses the results of similar buildings previously analyzed with NLTH. A good reference building is comparable with regards to PGA, network of walls, thickness, and material property of the PSSEs. If no suitable reference building is not found, simplified calculation tools and engineering judgement is applied to conclude the safety of the elements.
The NSCEs are validated in the same manner following the guideline stated in NPR9998:2020 [RA3]. In case a building is ‘out of the ordinary’ or presents elements that are ‘out of the ordinary’, a more specific and detailed look is carried out.
The workflow is described in the next page: ‘Reference approach workflow’.