The site of the structure crosses an active seismic fault, which presented several challenges for the design team. Recognizing this, the Construction Authority commissioned a detailed fault analysis and provided this information to the proposers to manage a key risk element for the project. Designers also faced the challenge of designing the bridge to meet both Metro and Caltrans structural design criteria to which an innovative approach was adopted. Designers also faced the challenge of developing an approach to build the large woven concrete basket feature – the signature architectural elements of the project. Combined with other architectural features on the project, the design of the structure was unique and required workmanship and attention to detail not normally seen on freeway structures.
Innovation was utilized both in the design and management of the Gold Line Bridge. During design, the engineers faced the challenge of meeting design criteria, which required that damage to the structure, including deep foundations, should be visible for inspection following occurrence of the maximum design earthquake (MDE). To address this requirement, the engineer incorporated the use of Time Domain Reflectometry (TDR) within each pile foundation as a tool for inspectors seeking information about the structural integrity of the bridge foundations. In the first application of this kind, TDR consists of placing instruments in each column from which baseline readings are established. Following the MDE event, new data could be collected for analysis to determine whether deformations occurred deep within the supporting columns. With this data, engineers could determine whether more invasive inspections should be considered – a truly innovative approach to bridge design.
“I believe this piece of inspired infrastructure changes the quality of life for everyone who experiences it. It took the collaboration and hard work of a truly talented team of professionals from the Construction Authority, Hill International, Skanska and AECOM. Together, we were able to design and build the bridge better and more efficiently than ever done before. And through our work, we’ve been able to contribute to a cultural legacy for the region and its citizens. I’m proud of that.”
Habib F. Balian
Metro Gold Line Foothill Extension Construction Authority