Project Type: Evaluation
The Vital Structure: 

The Crossings Condominium

Issue

 

The Crossings Condominium contacted Vital Structures due to concerns of sloping and deflection in the floor of a board member’s condominium unit; located on the 2nd floor above a fitness center space. Upon opening the drop ceiling in the space below, Vital Structures observed several open web wood floor joists (trusses) had failed along their connection to a W24 steel beam.

temporary structural shoring
the crossings condominium diagram

Diagnosis

Drop ceiling tiles were removed in the entire gym and office spaces below the affected. Vital Structures prepared a partial as-built floor and roof framing plan, discussed with the joist connector plate manufacturer, and performed a gravity load analysis using STAAD.Pro. The evaluation concluded the following:

  • The failed joists appeared to have been installed upside-down.
  • The steel beam was overstressed with respect to lateral torsional buckling failure, apparently due to loss of lateral buckling restraint at the top flange along the row of failed joists.
  • Limited low roof joists were found to be overstressed.
  • The steel beam web blocking which secured the low roof joists and floor joists to the beam was questionably attached to the beam.
  • Top mounted joist hangers were fastened solely into plywood subfloor, against the hanger manufacturers fastening requirements.

 

 

 

Solution

Vital Structures submitted an evaluation report with general repair recommendations; including re-framing the entire floor area below the unit. Temporary structural shoring was immediately installed under the affected joists and beam, requiring periodic monitoring and adjustment by the shoring contractors. Due to the volume of suspended utilities in the drop ceiling area, a thorough MEP coordination and feasibility study was also recommended.

failed open-web floor joists

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