Improving Seismic Resilience: Assessment, Design and Retrofit Installation
Learn how we helped a major nuclear facility upgrade its existing buildings to meet regulatory safety requirements.
Identify potential vulnerabilities of existing facility buildings
Provide a clear, concise overview of the structures reviewed and the identified vulnerabilities
Determine the necessity for further detailed structural analysis and provide appropriate strengthening measures in relation to onsite conditions if required
ABS Group played an integral part in helping a client review and assess several of their critical building structures against the demands of an earthquake, including identifying key vulnerabilities. To determine the seismic resilience of the buildings a tiered review was performed using the guidance presented in the American Society of Civil Engineers/Structural Engineering Institute Standard 41 (ASCE/SEI 41).
After identifying potential seismic shortfalls, a more in-depth assessment was performed using Finite Element Methods (FEM) to assess the severity of the vulnerability; strengthening (seismic retrofitting) was required. Bespoke retrofit solutions were provided to solve the vulnerabilities identified.
- Review of structural systems to determine seismic vulnerabilities
- Designed engineered solutions to improve the resilience of vulnerabilities
- Report on the potential impacts should safety measures not be addressed
The solution provided was broken down into stages in line with ASCE/SEI 41 guidance, which provides a screening checklist to identify seismic vulnerabilities in the safety-critical buildings considered.
Review and Site Walkdown
Prior to the commencement of work, the safety functionality requirement of each building was agreed upon. This established the required seismic resilience and overall behavior of each building following a potential seismic event and allowed the appropriate performance criteria to be defined.
A walkdown of the buildings was then performed in conjunction with a desktop review of any supporting drawings and design information. This review enabled us to identify key shortcomings in the as-built conditions (such as missing structural members, supports or bolts), as well as condition concerns (such as watertightness, corrosion or collision damage) and any structural modifications (new opening or extensions) made to the buildings.
Once the required information was collated, screening checks were completed in accordance with ASCE/SEI 41. This process enabled common structural deficiencies to be readily identified, such as insufficient lateral bracing members. Following the completion of the review, meetings were held with the client to present the findings and discuss the next steps.
Detailed Structural Assessments
Once buildings with potential seismic vulnerabilities had been identified, a more detailed assessment was undertaken to quantify and establish their severity.
These detailed reviews typically consist of the following:
- Finite Element Analysis of the buildings
- A detailed design standard review (using relevant ACI, Euro Code and British Standards)
- Determination of the severity of shortfall (overall utilization)
The outcome from a more detailed analysis and assessment enabled us to provide the client with additional feedback about the seismic vulnerabilities and what potential mitigation or retrofit measures were required to resolve them.
Retrofit Design and Solution
Structural retrofits to mitigate the structural vulnerabilities were identified, such as upgrades to structural bracing members, strengthening of connections, additional structural members and similar fixes or modifications. These were designed bespoke for the client's buildings to relevant design codes (i.e., Eurocodes). Our team of engineers then worked with the client to provide detailed installation guidance and risk assessments to help create safe and practical solutions. The solutions proposed were designed to minimize any impact or disruption to site operations.
ABS Group's team of engineers and seismic specialists provided the client with a detailed review of the seismic resilience of several of the client's buildings. Our knowledge and experience allowed a cost-effective approach to be taken and gave the client confidence that it had seismically robust buildings.