Structural Engineering Evaluation and Analysis of Foothill Transit Headquarters
ABS Group assessed a California building's ability to resist damage during a large earthquake and recommended seismic retrofit options. Read about our award-winning Advanced Engineering project.
Provide an overview of the structure's seismic lateral force-resisting system and vulnerabilities in the event of an earthquake
Evaluate the seismic integrity of the structural elements against ASCE/SEI Standard 41-06
Recommend seismic retrofit options and estimate costs to repair the building
Foothill Transit needed to improve its understanding of the ability of their existing West Covina, California Administration Headquarters Building to resist earthquake forces. The company wanted to know how the vintage six-story building, which was built in 1969, could be retrofitted to limit structural damage during future large earthquake events.
Foothill Transit also wanted to know the rough estimate of construction costs for various seismic retrofit options to compare (1) the cost benefit of various seismic retrofit options with the reduction in earthquake risk to the building and (2) the potential repair costs in the event of a major earthquake.
- Understand the potential impact of a seismic event on the company's headquarters
- Determine the cost of seismic retrofit options compared with risk and potential repair costs
ABS Group's Advanced Engineering team developed three-dimensional computer models of the building utilizing the commercially available ETABS modeling and analysis software. We also performed structural engineering calculations to identify specific areas of seismic deficiency relative to code criteria. The engineers assessed strengths, weaknesses, and deficiencies in the building's lateral-force (earthquake)-resisting system with particular attention to critical and major structural members and connections.
Recommend Strengthening Retrofit Options
We developed seismic strengthening concepts to mitigate structural deficiencies and estimated construction costs for budgeting purposes. Our hazard evaluation revealed that the existing exterior cladding system at the north and south elevations of the building was inadequately attached and in need of replacement. We recommended replacing the existing cladding system with a new system.
During the assessment of the building, the following potential strengthening concepts were evaluated:
- Provide concrete overlays (i.e. thickened walls) on all existing concrete shear walls at all floor levels
- Addition of special reinforced concrete shear walls at the perimeter of the building
- Addition of a new special reinforced concrete shear wall adjacent to the non-ductile concrete moment frame at the northeast corner of the building
- Utilize an exterior exo-skeleton steel frame system at the outside of the building to provide additional lateral support for the building
- Base isolate the building above or below the ground floor level
- Provide wall dampers at the existing concrete shear walls
- Replace the existing cladding system (travertine) at the north and south sides of the building with a new metal louver system.
Develop Structural Engineering and Architectural Designs
As the Prime Consultant, ABS Group hired a local architectural firm to assist with architectural issues, such as replacement of the existing travertine cladding system with a new vertical metal louver system and installation of a new exterior LED lighting system. ABS Group was responsible for developing structural engineering and architectural design and construction drawings for the new louver system and lighting, as well as providing recommendations for tenant improvements to the existing main lobby and elevators.
Guide Selection of Strengthening Concepts
Each proposed strengthening concept for the building was developed considering the overall constructability in relationship to building operation, with an attempt to minimize potential conflicts with existing building tenants.
In addition, three architectural options were proposed to replace the existing exterior cladding (travertine) system at the north and south sides of the building. Since the existing connections and travertine elements were susceptible to failure during a moderate to large seismic event, a new vertical metal louver system was selected as the final cladding system to replace the existing cladding.