Innovative precast prestressed concrete truss system using shape memory alloys and conventional steel

Truss systems are mainly made with steel due to their lightweight, high strength in both compression and tension, and ease of manufacture. Concrete truss systems on the other hand have not been widely used in the construction industry because of its weak strength in tension. In this study, a concrete truss system prestressed with a conventional prestressing system and shape memory alloy (SMA) is proposed, and its sustainability is evaluated by estimating the embodied carbon footprint of the proposed system. The bottom concrete chord of the Howe truss is prestressed with conventional high-strength steel (HSS) reinforcement using mechanical tensioning, and the vertical elements are prestressed with SMA bars. The embodied carbon footprint of the FeMnSi SMA bar is evaluated by comparing it with the HSS reinforcements in chemical components and manufacturing processes. The concrete truss is designed and numerically validated for the concrete bridge girder application to satisfy the American Association of State Highway and Transportation Officials (AASHTO) service and strength limit states. The designed concrete truss satisfies the AASHTO service and strength limit states with 37.3% less total weight and 25.9% less carbon emissions than the reference model, which is as per the AASHTO type 2 I-girder.