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

Image: Side angle view from the right rear of the full dump truck crossing the long-span concrete girder bridge approach with As-is entrance conditions (no ramp before the joint between the pavement and the bridge deck) during live load testing

Full dump truck crossing the instrumented long-span concrete girder bridge with As-is entrance conditions

Researcher(s)

Principal investigators:

Co-principal investigators:

Project status

Completed

Start date: 12/01/14
End date: 05/31/16

Publications

Report: Investigation of the Effect of Speed on the Dynamic Impact Factor for Bridges with Different Entrance Conditions (3.48 mb pdf) May 2016

Tech transfer summary: Investigation of the Effect of Speed on the Dynamic Impact Factor for Bridges with Different Entrance Conditions (1.43 mb pdf) May 2016

Sponsor(s)/partner(s)

Sponsor(s):

About the research

Abstract:

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. Based on the calculated DIFs and the change trends for the associated important factors, the conclusions were as follows: