Building financiers and insurers are asking for seismic assessments to evaluate earthquake risk before financing a particular building project. The Territorial Authorities will identify the buildings at their possible risks and ask owners to conduct a detailed seismic assessment, especially on buildings prone to earthquakes.
Tenants are increasingly moving to buildings, which have less of a seismic risk, making it a highly marketable asset. Thus, real estate owners or any housing company should get a detailed seismic assessment before they start construction. But, if these real estate owners have failed to perform DSA, the financier and investor would ask in advance whether the project has undergone seismic risk.
The role of DSA
A building owner is advised to perform DSA, which is a requirement for the building’s seismic strengthening. DSA follows an Initial Seismic Assessment where more reliability or information is sought. Yet, the assessments are performed independently. It is a more detailed quantitative assessment than the ISA seeking to establish a building’s seismic performance.
Three main methods of DSA
There are three main methods to perform seismic risk, namely:
- analytical methods
- empirical methods
- hybrid approaches
DSA and accurate assess earthquake performance
After an Initial Seismic Assessment is performed, it is advisable to perform a more quantitative assessment and detailed evaluation with DSA. It intends to offer an accurate assessment of the capacity of a building to withstand in case of an earthquake event.
DSA requires some form of site measurement and testing and calculation and analysis. It may include a complete analysis of the existing building systems and elements’ capacities.
A DSA report includes a review of all the site inspection and property records about the following:
- Critical members’ %NBS
- Description of methodology
- Executive summary
- Bracing elements’ detailed description
- Summary of results
- Overall rating of the structure
- The initial range of remedial works
- Rough order of costs
DAS of existing buildings
The DAS of existing buildings provides the technical basis for the engineers to assess the existing buildings that are potentially prone to earthquakes.
Part 1 of the Guidelines in DSA outlines the application and scope, providing a general overview of the seismic assessment process. It shows the linkage with the requirements of the Building Act 2004 along with the regulations and the EPB methodology. DSA delivers a summary and outline of the principles to lessen the seismic risk in buildings.
Part 3 of the Guidelines set on the DSA process is a more complete assessment than the ISA process set in Part 2. DSA assesses the following:
- structural load paths for the entire building
- capacity of each structural element
- inelastic mechanisms
- global building reaction in the event of earthquake shaking
- impact of secondary structural
- critical non-structural building elements
The DSA process is based on the principle of Part 1, which is an integral part of the seismic assessment process.
An assessment summary report template summarizes the information from DSAs and ISAs. The summary should be included at the front of all the assessment reports for the potentially earthquake-prone buildings.