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Constructed in 1872 after the Chicago Fire, the Delaware Building was designed in the Italianate style of Architecture and constructed as a six-story structure clad with one of the earliest uses of precast concrete facade construction. In 1889, two additional floors were added along with a dramatic steel-framed atrium. The added floors were clad with sheet metal to replicate the original precast construction. The lowest two floors were clad with ornamental cast iron and glass.
Designated a Chicago Landmark, over time, various owners and tenants knocked large holes through interior brick masonry bearing walls for doors and mechanical ductwork. Floors were leveled with a thick concrete topping, which added significant weight to the structure.
RRJ was retained by the building owner to investigate the cause of bowing door jambs and sagging floors. RRJ’s findings disclosed that the lower bearing walls had begun to collapse and sagging timber floor joists were split and cracked in certain areas.
RRJ designed a substantial emergency shoring system consisting of needle beams and high-capacity shoring posts for supporting the building’s weight. After the bearing walls were stabilized, RRJ designed repairs consisting of structural steel frames and brick masonry that were installed in a specific construction sequence to restore the bearing wall load-carrying capacity while accommodating existing door and mechanical ductwork openings. RRJ recommended that all concrete topping slabs be removed to minimize the floor overload condition. Repairs were designed to strengthen existing floor joists by supplementing existing joists with new plywood web and sawn lumber bottom chord members designed to act compositely with the existing floor joists acting as top chord members. All bearing wall and floor joist strengthening repairs were successfully completed.