Engineering Commons^™

Comprehensive Subgrade Deflection Acceptance Criteria - Executive Summary, James Crovetti

Transportation Research Center: Subgrade Deflection Studies

This executive summary presents a summary of the findings of all study phases conducted to develop recommendations for the development of specifications for subgrade acceptance based on measured deflections. The rolling wheel deflectomter (RWD), portable truck-mounted deflection measurement systems, and dynamic cone penetrometer (DCP) were utilized on numerous subgrade construction projects between the 1998 and 2001 construction seasons. Comparative nuclear density and soil stiffness gauge readings were also obtained at selected locations on many of the included construction projects.

The research findings indicate that deflection test results may be appropriate for identifying areas of poor in-place stability within constructed subgrades. …

Transfer Length Of Strands In Prestressed Concrete Piles, Baolin Wan, Kent A. Harries, Michael F. Petrou

Civil and Environmental Engineering Faculty Research and Publications

A top bar effect has been identified in prestressed concrete piles. The effect that this top bar effect has on the development of the prestressing strand is investigated. Strand transfer length is found to be proportional to the observed end slip. While the average transfer length of all strands in a section may satisfy the assumptions inherent in the ACI transfer length equation, due to the top bar effect, top-cast strand transfer lengths are considerably in excess of the ACI-calculated value. The flexural behavior of the pile, accounting for varying transfer lengths through its section, is investigated. Finally, recommendations for …

Top Bar Effects In Prestressed Concrete Piles, Baolin Wan, Michael F. Petrou, Kent A. Harries, Aly A. Hussein

Civil and Environmental Engineering Faculty Research and Publications

The top bar effect in reinforced concrete is a widely recognized phenomenon. Currently, the ACI Building Code prescribes a 30% increase in the development length of top cast reinforcing bars. No such provision is required for strands in prestressed concrete members. In this paper, the top bar effect for prestressing strands is introduced. Parameters affecting top bar phenomena in prestressed concrete piles are identified, and strategies for reducing this effect are presented. Finally, for the first time, the application of a top bar effect factor for prestressed concrete development length calculations, similar to the one applied in reinforced concrete structural …

Comprehensive Subgrade Deflection Acceptance Criteria - Pilot Implementation Report, James Crovetti, Jay Schabelski

Transportation Research Center: Subgrade Deflection Studies

This report has presents the findings of implementations of pilot specifications for subgrade acceptance based on measured deflections. The reconfigured rolling wheel deflectomter (RWD), portable truck-mounted deflection measurement systems, and dynamic cone penetrometer (DCP) were utilized on four subgrade construction projects during the 2001 construction season. Comparative nuclear density readings were obtained at selected locations within each project. Comparative soil stiffness gauge readings were also obtained on 2 of the pilot projects

The research findings from this and previous study phases indicate that deflection test results may be appropriate for identifying areas of poor in-place stability within constructed subgrades. However, …

Public Perceptions Of The Midwest’S Pavements: Policies And Thresholds, David Kuemmel, Richard Robinson, Ronald C. Sonntag, Robert Griffin, James K. Giese

Marketing Faculty Research and Publications

A 5-year, pooled fund study with the Iowa, Minnesota, and Wisconsin departments of transportation assessed the public's perceptions of pavement improvement strategies and developed thresholds of satisfaction using the departments' physical indices, such as pavement ride and condition on rural, two-lane highways in the states. Approximately 3,600 drivers in the three states were involved in the three phases of the project, which included 18 focus groups, 400 statewide surveys in each state, and 2,300 targeted surveys across the three states. A multidisciplinary team from Marquette University and a mass media survey lab conducted the studies. A summary of focus group …