Smart Engineering has collaborated in the structural optimization of the reinforcement and the modeling of the fiber-reinforced concrete segments for the construction of a new tunnel in order to expand the operational and traffic capacity of vehicles through the Chesapeake Bay Bridge and Tunnel ( CBBT).

The CBBT is a 28.3 km open road to traffic formed by a set of bridges that cross the Cheasapeake Bay (Virginia, USA) and connected by two tunnels under the Thimble Shoal and Cheasepeake Channel channels that allow the navigation of boats through the Bay. The Parallel Thimble Shoal Tunnel (PTST) project consists of the design and construction of a new tunnel of approximately 1.7 km parallel to the existing one under the Thimble Shoal navigable channel. The design and construction of the project has been carried out by Cheasapeake Tunnel Joint Venture, formed by Dragados USA and Schiavone Construction.

Once completed, the tunnel is designed to accommodate two new lanes of traffic that will serve southbound traffic, while the existing tunnel will route traffic northbound. The construction of the new tunnel will thus improve the level of service and security of the current infrastructure, allowing greater traffic capacity under normal conditions and providing an alternative route in the event of an accident in the existing tunnel.

The Parallel Thimble Shoal Tunnel project is carried out using the Tunnel Boring Machine (TBM) technique for the excavation and use of voussoirs to support the tunnel. The tunnel has an internal diameter of 12 meters, requiring around 9000 pieces of concrete. For this, approximately 32000 m3 of concrete are necessary for the manufacture of the tunnel sections.

As an alternative to conventional reinforcement based on steel reinforcement, the use of steel fibers as concrete reinforcement has been chosen as a solution. This implies, in addition to the need to satisfy the structural specifications, to meet the service and durability requirements specified in the project. In this regard, Smart Engineering has provided support in the process of structural optimization of the reinforcement with steel fibers in the segments by studying, evaluating and modeling the characteristics of the segments. The structural optimization studies carried out allow analyzing the expected mechanical behavior of the segments and verifying compliance with the project requirements regarding durability and behavior in service.