Fatigue Analysis and Design of Steel Orthotropic Deck for Bronx-Whitestone Bridge, New York City

Abstract

A description is given of the parametric study done to evaluate the structural behavior of the replacement steel orthotropic deck planned for the Bronx—Whitestone Bridge in New York City. A principal objective was to analyze the deck details for stress ranges that indicated sensitivity to fatigue cracking. On the basis of the analysis findings, important modifications were made to the preliminary deck design. These changes were primarily to reduce the maximum stresses in the diaphragms and ribs around the diaphragm cutouts—locations that traditionally have been prone to cracking, as observed on orthotropic decks on other bridges. After the completion of the deck design, a full-scale prototype deck measuring 48 by 37 ft was fabricated and subjected to a series of laboratorycontrolled fatigue tests. Proper boundary conditions and loading procedures were created to produce stress ranges similar to those in the full bridge model. Laboratory test results correlated well with the computed stress ranges and demonstrated that the deck had outstanding fatigue resistance and could readily provide the 75-year design service life specified for the orthotropic deck.

Fatigue of steel bridge infrastructure

“…Several orthotropic decks in service were known to have developed load-induced fatigue cracks as a result of localized in-plane and out-of-plane bending stresses that are complex and variable at this location (Gajer et al 1996, Fanjiang et al 2004.…”

“…The internal stiffeners reduced the force transmitted through the rib wall and served to distribute the distortion of the rib wall away from the diaphragm connection. The deeper rib also better accommodated the rib wall distortion (Fanjiang et al 2004).…”

“…The test programme for the Bronx-Whitestone Bridge used three deck actuators in the outer lane spaced at 1.5 metres along the length of the deck, and two floor actuators spaced at 6.0 metres to simulate the curvature of the symmetrically loaded (and deflected) full-width section, shear and moment, and the resulting floor-beam diaphragm effects (Fanjiang et al 2004). The load level was equivalent to the original load level used for the design of the prototype deck of 3 6 HS15 fatigue trucks with an additional 15% for impact (3.45 6 HS15 ¼ 369 kN per single-axle), a load level that corresponded to the (estimated) maximum stress range in the random variable spectrum determined from field measurements by Connor and Fisher (2001) and Connor et al (2003).…”

Full-scale fatigue tests of steel orthotropic deck panel for the Bronx – Whitestone Bridge rehabilitation

“…The refined design solution (using 2.3 6 HS15) resulted in the use of a deep diaphragm cutout geometry and internal rib wall stiffeners at each supporting floorbeam diaphragm (in place of 'bulkhead' plates as used in other decks (Kaczinski et al 1997, Tsakopoulos and Fisher 1999, Fanjiang et al 2004. The rib-to-diaphragm connections were specified to be complete-penetration groove welds with back-to-back reinforcement fillet welds along the entire length of the connection, similar to those used in other decks (Kaczinski et al 1997, Tsakopoulos andFisher 1999).…”

Fatigue life estimates for a slender orthotropic steel deck

“…[1,2] while cracks at the rib to floorbeam connection might occur for different cut out details [3]. Improving these geometrical details [3,4] in order to reduce stress variations has been an important task for the design engineer.…”