Hoover Mason Trestle: A Modern Steel Walkway on the Tracks of a Former Ore Train, Bethlehem Steel Plant, Bethlehem, PA

Abstract

For decades, the 1906 Hoover Mason Trestle at the historic Bethlehem Steel plant in Bethlehem, PA, supported ore-filled rail cars transporting raw materials from the Ore Yard to the steel plant’s large furnaces, five of which remain standing. After being left to decay for several decades, the Trestle is getting a new life as the backbone of a new, half-mile long promenade that will offer unique and publicly-accessible views into the historic steel plant, the new SteelStacks Campus, and surrounding town. The architectural design of the walkway follows a sinuous path both vertically and horizontally along the linear railway tracks. The underlying structure of the walkway is a series of wide flange post and beam ‘bents’ with ‘feet’ that affix to the train rails. The bent’s horizontal girders vary in length, cantilevering to one or both sides of the posts to accommodate the varying geometry of the walkway. Affixing the posts to the rails offered a uniform connection type and methodology. Between the main steel bents, secondary steel beams support one of three features: cast-in-place concrete walkways on steel deck, steel bar-grating walkways, or cast-in-place concrete planters on steel deck supporting up to 30 in. of soil and vegetation. Bearing on the existing historical structure created a variety of design challenges. Despite the original drawings and many of the repair and/or replacement drawings being available, several portions of the trestle have been reconstructed or heavily modified without documentation. This created complexities in understanding the limitations and opportunities in the existing framing.