Identifying Magnitudes and Locations of Loads on Slender Beams With Welded and Bolted Joints Using a Strain Gage Based Force Transducer With Application to a Portable Army Bridge

Abstract

A strain gage based force transducer has been developed to identify magnitudes and locations of loads on non-continuous slender beams with welded and bolted joints. The slopes of the bending moment curves on the two sides of a load are calculated from measured strains on a beam. Four uniaxial strain gages are mounted to the bottom surface of the beam, with two strain gages on each side of the load. A calibration method developed earlier can be used to account for the discrepancies between the theoretical and actual scaling factors arising from stress concentrations and unpredictable stress patterns in the beams due to the presence of the joints. The force transducer methodology is experimentally validated on a continuously tapered aluminum beam with a series of welded joints, an aluminum beam with a constant cross section and a bolted joint, a half aluminum and half steel beam with two different cross sections and a bolted joint, and a full scale portable army bridge at the US Army Aberdeen Test Center.

Identifying Magnitudes and Locations of Multiple Loads and the Resultant of a Distributed Load on a Slender Beam Using Strain Gage Based Methods

“…When the loads are separated by two or more strain gage locations, multiple force transducers, each consisting of four uniaxial strain gages mounted to the bottom surface of the beam, can identify the magnitudes and locations of the loads. 28 γ n Scaling factor at strain gage location n ε Bending strain ε 1 − 1 , ε 2 − 2 Principal strains ε n Strain or strain gage at strain gage location n ν Poisson's ratio σ 1 , σ 2 Principal stresses τ Shear stress When the loads are separated by one strain gage location, the problem is ill posed because many solutions exist for the calculated bending moment diagram.…”

Identifying Magnitudes and Locations of Multiple Loads and the Resultant of a Distributed Load on a Slender Beam Using Strain Gage Based Methods

“…The strain gage based force transducer methodology is extended to slender beams with welded and bolted joints, with application to a portable army bridge, in a follow-up article. 28 γ n Scaling factor at strain gage location n ε Bending strain ε 1 − 1 , ε 2 − 2 Principal strains ε n Strain or strain gage at strain gage location n ν Poisson's ratio σ 1 , σ 2 Principal stresses τ Shear stress…”

A combined loading transducer for calculating the bending moment and torque in a slender circular beam using the minimum numbers of strain gauges, strain grids, and measurement channels

“…One such advanced case would be using multiple uniaxial strain gauges to build a strain gauge-based force transducer to measure static or dynamic loading on a simply supported beam. 5 It has been shown in Bednarz and Zhu 6 that the strain gauge-based force transducer can be applied to a large-scale bridge. Uniaxial strain gauges can also be utilized to measure static or dynamic pressure.…”