Investigation of the Effect of Speed on the Dynamic Impact Factor for Bridges with Different Entrance Conditions, 2016

The dynamic interaction of vehicles and bridges results in live loads being induced into bridges that are greater than the vehicle’s static weight. To limit this dynamic effect, the Iowa Department of Transportation (DOT) currently requires that permitted trucks slow to five miles per hour and span the roadway centerline when crossing bridges. However, this practice has other negative consequences such as the potential for crashes, impracticality for bridges with high traffic volumes, and higher fuel consumption. The main objective of this work was to provide information and guidance on the allowable speeds for permitted vehicles and loads on bridges .A field test program was implemented on five bridges (i.e., two steel girder bridges, two pre-stressed concrete girder bridges, and one concrete slab bridge) to investigate the dynamic response of bridges due to vehicle loadings. The important factors taken into account during the field tests included vehicle speed, entrance conditions, vehicle characteristics (i.e., empty dump truck, full dump truck, and semi-truck), and bridge geometric characteristics (i.e., long span and short span). Three entrance conditions were used: As-is and also Level 1 and Level 2, which simulated rough entrance conditions with a fabricated ramp placed 10 feet from the joint between the bridge end and approach slab and directly next to the joint, respectively. The researchers analyzed and utilized the field data to derive the dynamic impact factors (DIFs) for all gauges installed on each bridge under the different loading scenarios.

Iowa Statewide Recreational Trails Plan, 1990

The Iowa Statewide Recreational Trails Plan was developed in response to the State Legislature's recognition of the increased public demand for quality outdoor recreational facilities and the numerous benefits associated with the development and usage of trail systems. The plan presents a statewide trails system that will serve as a basis for trail planning efforts throughout the state. Included are design guidelines for each of the major trail modes contained within the plan including bike, hiking, cross-country skiing, snowmobiling, off-road vehicles, and equestrian, as well as for locating trails within the highway right-of-way. Also included are estimates of implementation costs and financing alternatives. This report contains the complete plan. Separately bound documents include the Executive Summary and two additional appendices: (1) Trails Plan Resource Inventory and (2) Summary of Public Comments and Summary of Technical Advisory Committee Comments.