Three major studies of the Golden Gate Bridge were performed at T.Y. Lin International (TYLI) between 1989 and 1991 under the direction and leadership of current OPAC staff. Ongoing seismic and wind retrofit programs resulted from these studies. The transit study (1990) evaluated the feasibility of building a second deck. Structural feasibility of a proposed bridge within a bridge was evaluated by numerical studies of static and dynamic bridge response. Wind tunnel tests and dynamic computer modeling provided refined estimates of bridge vulnerability to extreme winds. The seismic evaluation (1990) was the first of its kind for an existing major bridge. It included seismic hazard assessment, synthesis of incoherent multi-support ground motions, 3D dynamic analysis, assessment of the performance of structural components, identification of structural deficiencies and vulnerabilities, and peer review. The seismic retrofit studies (1991) continued the evaluation work and provided strategies for retrofitting the bridge to a new higher standard. Nonlinear local and global analyses provided refined vulnerability estimates. Retrofit measures were studied to arrive at cost estimates for a system of necessary and sufficient retrofit measures.

• Mark Ketchum, current OPAC Principal, served as Project Manager and Lead Investigator for TYLI through project completion.
• Kwong Cheng, current OPAC Principal, served as Supervising Engineer for TYLI.