Several major bridge structures and buildings in San Francisco were damaged during the 1989 Loma Prieta Earthquake. The review of some structures revealed damage that could not be repaired economically.
Because the bridge structures were located downtown, often within feet of office, retail, hotel, residential buildings and pedestrian or vehicular traffic, blasting and crane and impact ball were not permitted. Demolition had to be controlled and engineered.
Before demolition, an engineering analysis is conducted to evaluate the structure's capacity during each demolition stage to support the weight of equipment or other demolition-related loads, usually debris. The analysis reviews strength and stability for gravity and lateral loads as parts of the structure are demolished or no longer contribute to capacity.
The new equipment technology challenges well-established demolition considerations. The recent demolition of earthquake-damaged bridge structures offered new perspectives for engineered demolition of concrete structures. Many well-respected demolition contractors with years of experience have adapted to new equipment and procedures.