Precast Double-Tee Garage Connections Failures due to Vehicular FatigueLoad

The FFC ICRI chapter is excited have Lawrence E. Keenan, AIA PE, of Northford Structural Connections to discuss Precast Double-Tee Garage Failures due to Vehicular Fatigue Loading.

Lawrence Keenan brings experience and technical insight to complex structural challenges. Both a licensed structural engineer and a registered architect, he has over 30 years’ experience testing, investigating, and rehabilitating concrete structures. He is a past president of the Connecticut Chapter of ICRI and holds two US Patents for precast concrete structural connections.

Flange connections of precast concrete double-tee parking structures are poorly configured to withstand high-cycle vehicular loading and fail to meet Code requirements for fatigue resistant design. Connection failures typically spread along the joint until the joint is completely severed. While commonly considered a maintenance item or nuisance, these connections are an essential part of the lateral load resisting system; loss of connections along a joint severs the deck diaphragm and threatens the general stability of the structure. Testing and analysis recently performed by the precast industry purport to allay concerns regarding these connections; however, careful review of these studies reveals the common, modern connection exacerbates the fatigue failure mechanism by concentrating stress at the ends of the welded connection. This presentation explores the fatigue failure mechanism as it applies to double-tee connections and explains how fatigue failures are easily identified in the field. Code requirements for high-cycle fatigue performance are discussed and recent studies are examined to provide an alternate interpretation to that established by the precast industry.

Objectives:

1. To provide an understanding of the mechanism behind high cycle fatigue failure of double-tee connections.

2. To demonstrate methods for assessing parking structures for fatigue connection failures, including visual identification of fatigue fractures.

3. To review AWS and AISC Code requirements regarding design of connections for fatigue resistance.

4. To examine the current state of the art in design of precast double-tee connections for fatigue resistance.

Host or Publisher ICRI Florida First Coast Chapter