Instrumentation and Monitoring of Rustic Road Geosynthetic Reinforced Soil (GRS) Integrated Bridge System (IBS)

An instrumentation and monitoring system was implemented for a geosynthetic reinforced soil (GRS) integrated bridge system (IBS) constructed in Boone County, Missouri in 2014. The project location is subjected to relatively frequent flash flooding, which was a significant consideration in the design of the bridge and the design of the monitoring system. The monitoring system includes 26 surveying points on the bridge exterior to monitor external movement; settlement plates and inclinometers to monitor vertical and horizontal exterior movement, respectively; earth pressure cells to monitor total stresses within the abutment backfill; and vibrating wire piezometers to monitor pore pressures and drainage within the abutment backfill. The GRS-IBS was monitored for a period of 19 months after construction. The monitoring period included several high-water events, but none overtopped the bridge. The results indicate satisfactory performance, including negligible external and internal movements and rapid backfill drainage in response to groundwater level increases.

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Report number: cmr 16-019
Published: November 2016
Project number: TR201417
Author(s): Andrew Boeckmann, Eric Lindsey, Sam Runge, and J. Erik Loehr

Performing organization: University of Missouri-Columbia Department of Civil & Environmental Engineering

Driving Simulator Study of J-Turn Acceleration/Deceleration Lane and U-Turn Spacing

The J-turn, also known as RCUT (Restricted Crossing U-Turn) and Superstreet, is an innovative geometric design that can improve intersection safety. Even though this design has been in use in several states for many years, there is very little research-based guidance for several design parameters. A driving simulator study was conducted to analyze the parameters of lane configuration, U-turn spacing, and signage. Two lane configurations were examined: 1) acceleration/deceleration configuration where acceleration and deceleration lanes are provided and 2) deceleration only configuration where only deceleration lanes are provided. Lane configuration was found to be the most important parameter affecting J-turn safety based on speed-differentials. The only significant interaction effect among parameters was between lane configuration and U-turn spacing. The acceleration/deceleration configuration performed better than the deceleration only configuration with 66.3% fewer safety critical events. Vehicle trajectories and average lane change locations showed that U-turn spacing impacted significantly the acceleration/deceleration configuration (e.g. average merge locations changed by 96% to 101%) but not the deceleration only configuration. No strong preference was demonstrated by the study subjects for either the directional or the diagrammatic signage style. This report presented the first human factors study of the J-turn focused on developing design guidance. This human factors approach complements other traditional approaches such as crash analysis and micro-simulation.

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Report number: cmr 16-018
Published: November 2016
Project number: TR201515
Author(s): Carlos Sun, Ph.D., P.E., J.D., Professor (PI), Praveen Edara, Ph.D., P.E., Associate Professor (co-PI), Charles Nemmers, P.E., Research Professor (co-PI), and Bimal Balakrishnan, Associate Professor (co-PI) 

Performing organization: University of Missouri-Columbia Departments of Civil & Environmental Engineering and Architectural Studies