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https://www.nationalacademies.org/trb/events

SEAHIVE® solutions to mitigate bridge scour – PH 1

Scour remains the primary cause of bridge failure. It can occur locally around an abutment/pier or in between foundation elements. Scour is difficult to predict as there is no unified method based on soil properties and complex hydrological flow profiles to understand soil erodibility. Once bridges are installed, changes in the hydraulic load from the foundation obstructions constructed in the flow path, natural river meandering (i.e., direction change) or unprecedented loading from extreme events can further alter bridge scour predictions. The objective of this research project is to show a proof-of-concept of using innovative hydraulic load dissipating elements, known as SEAHIVE®. This is a modular engineered protection system composed of concrete perforated hexagonal prisms. Perforations on the side faces of the elements provide passage for water flow dissipating the energy within the system while also adding structural complexity which improves its potential for habitat creation. SEAHIVE® has been under research and development at the University of Miami (UM) for wave energy dissipation and habitat enhancement with three pilot installations completed. This UTC study will investigate the performance of the SEAHIVE® system in mitigating bridge scour. This project has the potential to create a consortium-wide effort for implementing the SEAHIVE® system into practice and creating transformational change in how we design bridge foundations considering scour. It will consist of three phases at UM. The first one (year one) will be devoted to the characterization and production of the SEAHIVE® elements using industrialized technologies. We have currently identified four possible methods to manufacture SEAHIVE® elements. The first-year phase one will focus on externally prestressed elements given the mass production and scaling-up advantage. Externally prestressed (by Glass FRP rovings) units produced by dry cast with the same equipment used to produce concrete pipes. The most significant advantages of this construction method are: a) speed of production of fully cured units at a rate of five or more per hour; b) elimination of internal reinforcement; and, c) the leanest possible concrete mixture. The unit’s length would be limited to a maximum of 8-ft.vc. Other potential fabrication techniques include, precast internally reinforced wet-cast or longitudinally prestressed production based on existing pile production methods for longer units, and 3D construction printing for more complex multi-unit combinations. Texas State University (TXST) will focus on evaluating the potential for bridge scour mitigation in highly erodible sediment in year one. This will be achieved using flume tests and a calibrated numerical model. Model tests in the flume will be conducted to determine the optimized SEAHIVE® configuration, considering a SEAHIVE monopile and a three-unit system in front of a traditional monopile. A coupled hydrodynamic-morphodynamic model in Open FOAM will be created to offer insights into the changed flow dynamics from the SEAHIVE® elements for bridge scour energy dissipation. The hydrodynamic-morphodynamic model will be verified with the monopile flume data.