Seismic Evaluations of Concrete Reinforced Buildings after Earthquakes
Worldwide earthquakes have claimed thousands of lives and caused billions of dollars of economic impact in the past 15 years. The 2023 earthquake in Turkey killed at least 50,000 people and the cost of the damages was approximately $100 billion.
A new report issued in April 2023 entitled “Hazus Estimated Annualized Earthquake Losses for the United States”(FEMA P-366) by the United States Geological Survey and the Federal Emergency Management Agency estimates that the cost of earthquake-related damage in the U.S. is $14.7 billion annually. This estimation is based on updated earthquake hazard data and building inventory exposed to seismic risk. Similarly, the National Center for Prevention of Disasters of Mexico estimates the annual cost of earthquake damage at $1.4 billion.
FEMA P-366 states that the vulnerability of aging building inventory, including non-ductile reinforced concrete buildings is a pattern of steadily increasing damage and losses during recent earthquakes. Non-ductile reinforced concrete buildings are brittle and have a limited capacity to dissipate the energy of an earthquake due to the lack of adequate reinforcement and seismic detailing. These buildings have a high probability of collapse. New buildings with design and construction deficiencies can also have poor performance during seismic events. Typical failures observed in concrete buildings during recent earthquakes are soft story, short-column, frame infill cracking, and roof diaphragm anchorage, among others.
Post-earthquake assessments of concrete buildings are critical for saving lives and helping with recovery operations. During these assessments, a professional and experienced structural engineer verifies whether or not structural safety, stability, and serviceability are compromised after seismic events. Gathering information about damaged buildings, such as recorded ground motion, geometry, mass distribution, gravity and lateral systems damage, and non-structural component damage, is an important aspect of post-earthquake assessment, including the general condition of buildings. Rapid and detailed assessments are typically conducted to restrict, prevent, or enable access to specific areas or the whole building after earthquakes. ATC-20, Post-earthquake Safety Evaluation of Buildings provides procedures and guidelines for a rapid and detailed evaluation of earthquake-damaged buildings, including evaluation forms, and posting them as:
- Inspected (apparently safe, green placard)
- Limited Entry (yellow placard), or
- Unsafe (red placard)
Detailed evaluations should follow a rapid evaluation to assess specific components or essential facilities.
After a rapid or detailed post-earthquake assessment, buildings require an evaluation regarding whether or not they shall be repaired to their pre-damaged condition or retrofitted before being reoccupied and restarting operations. International Existing Building Code (IEBC) establishes a methodology to evaluate if a structure shall be repaired or retrofitted after earthquakes. This methodology evaluates the level of damage using the disproportionate earthquake damage condition concept. If this evaluation establishes that the building in its pre-damaged condition complies with IEBC, then the damaged elements can be restored to their pre-damaged condition.
On the other hand, if the building does not comply, it must be repaired and retrofitted. Retrofit of buildings shall be performed following the requirements of the IEBC, American Society of Civil Engineers “Seismic Evaluation and Retrofit of Existing Buildings” (ASCE41), and local codes, including extensive non-destructive and material testing.
In an effort to help with recovery after seismic events, Walter P Moore has team members in North America, Latin America, and India who are highly trained in post-earthquake damage assessment and reconnaissance in high seismic zones.
We have provided post-earthquake assessments of buildings after the 2014 Napa and Vallejo, 2015 Nepal, 2017 Mexico City, 2020 Puerto Rico, 2021 Guerrero, and 2022 Michoacan earthquakes. Within 24-48 hours of the event, the firm can deploy industry-acclaimed structural experts worldwide.
Our engineers are well-versed in international codes and local construction practices worldwide. The Walter P Moore experts will focus on a range of seismic evaluations, including rehabilitation solutions. Most importantly, our team is committed to providing technical direction for structural safety and recovery of any damaged structures after these natural disasters. We can also provide services to evaluate seismic risks and vulnerability of existing buildings.
The Walter P Moore team is proud to be a trusted advisor during times of crisis after earthquakes. To find more information about our post-earthquake assessment and catastrophic (CAT) event services at walterpmoore.com.
Luis Buitrago, P.E., is a principal and managing director in Walter P Moore’s Diagnostics Group. He can be reached at email@example.com.
For information on how to receive assistance with buildings and infrastructures affected by earthquakes, contact Walter P Moore at 800.364.7300.