Rating Methods for Defining Performance of Existing Concrete Bridges (ACI Spring 2018 Convention, Salt Lake City, UT) Load rating is the process used in determining the safe load-carrying capacity of a bridge. When available information about a bridge is not sufficient to inform conventional analysis practices, bridge engineers often use engineering judgment to formulate a rational estimate of a bridge’s load rating. This engineering judgement is subjective and can potentially be unconservative, which could pose potential risk to safety or accelerate damage to an overloaded structure. Alternatively, if the rating is too conservative, the result can affect prioritization of maintenance operations and may unnecessarily restrict commerce. This presentation describes an investigation aimed at developing rational engineering approaches for load rating structures within the Virginia Department of Transportation inventory for bridges with insufficient details. The presentation will highlight features of select Structural Identification (St-Id) approaches that were used in the study along with a description of their performance and accuracy. Results demonstrate the benefits and limitations, but also the viability of the proposed method to help VDOT improve the ratings of these structures in a safe, cost-effective manner while also increasing or eliminating postings on some bridges, and thus improving the flow of commerce within the Commonwealth.

Constructability: From Definition to Industry Practice (ACI Fall 2018 Convention, Las Vegas, NV) This presentation will discuss the tower crane innovative scheme for construction in a challenging urban site. A new residential development is currently being constructed in the heart of downtown Chicago along upper Wabash Avenue near the Chicago River. The project consists of an 18-story, 150,000 sq ft residential vertical expansion to an existing “in-service” 4-story cast-in-place reinforced concrete parking structure that was built in the 1980’s. The project site is bounded on the west side by the existing congested two-level Wabash bridge viaduct constructed in the1930’s, an existing 54-story residential tower to the east, and private driveways to the north and south of the site. Since the 18-story concrete structure is being built on top of an existing parking garage, new foundations were not required. Extensive review of the existing Wabash Bridge and existing garage structure as well as the tower crane were performed and will be discussed in this presentation.