Understanding Half Bridge Strain Values

[CanoIsDbo]

Hi, I am using a half bridge strain gage configuration on a simply supported beam. If i get negative strain, does that mean I am getting a positive force or a negative force on the beam? I am confused since one gage is in tension and the other is in compression.

Thanks

 

[Astronuc]

A negative strain indicates a reduction in dimension, which indicates compression.

When a solid is in uniaxial tension, there is a slight reduction in cross-sectional area, or a negative strain in the directions transverse to the tensile axis. The relationship between (ratio of) transverse contraction strain to longitudinal extension strain is expressed through Poisson's ratio.

http://silver.neep.wisc.edu/~lakes/PoissonIntro.html