DESIGN, FABRICATION, AND CONNECTION DETAILING OF A SMALL-SCALE ALUMINIUM PRATT TRUSS BRIDGE PROTOTYPE FOR STRUCTURAL LABORATORY APPLICATIONS

The design and fabrication of physically accurate structural prototypes for laboratory testing requires precise attention to member geometry, connection detailing, material selection, and construction methodology. This paper documents the systematic design and fabrication process of a small-scale aluminium Pratt truss bridge prototype developed for structural laboratory testing, with a total span of 1,800 mm, a panel height of 440 mm, and a width of 500 mm. The study details the rational basis for Pratt truss configuration selection, the design of aluminium alloy 40 × 40 × 2 mm square hollow section members, the four gusset plate typologies (Types A–D) designed for the distinct joint configurations of the truss, and the bolted connection detailing using Grade 4.8 M6 bolts. Support conditions pin at one end and roller at the other are discussed in the context of static determinacy requirements. The fabrication process, including member cutting to prescribed angles, gusset plate shaping, drilling, and bolted assembly, is described in detail. The resulting prototype demonstrates good dimensional compliance with design specifications and provides a reproducible reference design for aluminium Pratt truss bridge laboratory studies. Key lessons from the fabrication process, including diagonal member cutting challenges and joint assembly sequencing, are identified and discussed.