Formwork Analysis and Design/ Shoring-Reshoring Analysis

FKC  reviewed and evaluated the formwork system used to form the cast-in-place exterior arched walls along the perimeter of the North River water treatment plant.

The new addition to the Smiley Arts Building is a three-story flat slab reinforced concrete structure.  Soon after the concrete slab construction and the removal of the formwork, the slabs developed spider-like cracking at the vicinity of columns and further exhibited excessive deflections.   The slabs were constructed during the winter time with temperatures averaging below 32° F for several days.  Early age concrete gains little to no strength at such low temperatures and cracks and deflects if loaded prematurely.  FKC  investigated the effects of shoring-reshoring formwork operations, the cold weather conditions, and the slow concrete strength development on the slab cracking and deflections.  Concrete maturity models were developed and the approximate concrete strength and slab stiffness at the time of formwork removal were estimated.   In addition, FKC conducted field surveys of slab cracking patterns, slab deflections, slab thickness, and performed concrete testing including strength test and petrographic examinations.  A report was issued with conclusions and recommendations.  FKC provided litigation support services.

The elevated slabs  of this two-story reinforced concrete structure were designed as one-way slabs supported in the middle by a wide shallow beam.  Shortly after the construction, the concrete slabs developed extensive cracking and excessive deflections.   The already installed partition wall metal studs at the ground floor buckled  due to the deflection of the slab above.   FKC investigated the causes for the slab damage.  FKC  investigated the effects of the shoring-reshoring  formwork operations, as well as the effects of design details on the slab cracking and deflections.   Concrete maturity models were developed and the approximate slab strength and stiffness were estimated for the various phases of construction. The estimated load carrying capacity  and deflections of the concrete slabs  were evaluated with respect to the applied construction loads.    FKC issued a report summarizing the findings, conclusions and recommendations.