305 2nd Street
There are six different adjoining commercial structures on this property that extends over a full city block along 4th Avenue in Brooklyn. Five of the buildings are one story warehouse structures with the roof supported by wood joists on large span timber “bowstring” trusses bearing on the brick perimeter walls. A partial collapse of the roof over one of the structures occurred in the winter of 2010 the area underwent preliminary stabilization work, until 2012, when Madsen was approached by the owner to take over the project from another structural engineer. Madsen performed a thorough investigation of all the existing structures and it was discovered that several roof trusses exhibit considerable damage at the end bearing connections particularly visible by cracking and loss of integrity in the bottom chord and attaching tie plates. Certain trusses also exhibit significant lateral displacement at the top and bottom chords often causing displacement of adjacent trusses attached by cross-bridging steel rods.
The current rehabilitation work includes the rebuilding of the masonry walls along damaged or leaning portions of the existing building. Existing bowstring trusses have been supported by placing steel tube columns on concrete footings underneath the bottom chords, at each end, and at the interior spans, with built-up timber posts continuing up to the top chords. New steel cross-braces and horizontal timber braces were introduced between trusses to restore the rigidity of the lateral system. Aside from filing structural drawings, Madsen provided full calculations and reports for the thorough review of the NYC Department of Buildings engineers.