University of Mississippi  Department of Civil Engineering 
CE407: Civil Engineering Laboratory II 

Experiment S2b:  Nondestructive Strain Measurement In A Three-Hinged Arch Bridge
Dr. Chris L. Mullen
Last Updated: 10-31-01

1.2 The objective is to observe how the normal strain may be measured at various positions along the arch and deck and to compare the measured predictions with theoretical estimates obtained by elementary structural analysis and numerical analysis to be performed in Experiment S2a.
 

2.0 THEORY
2.1 Definitions.

Strain- the intensity of length change per unit of length.
Strain gage- measurement transducer which converts change in electrical resistance to change in length per unit of the gage length in a particular direction- the gage axis in the case of a single output gage (the case here).
Strain gage indicator- device which receives the electrical impulse trasmitted through a wire (attached at one end to the strain gage and at the other end to the indicator input location), and then converts the analog signal to a digital LED (light emitting diode) display.

4.0 EXPERIMENTAL PROCEDURE
For the symmetrical configuration in Experiment S1, consider three load cases consisting of the 50 N wheel follower load placed sequentially at positions, x0 / L0= { .25 , .50, and .75 } .

Measure the strain, i.e. attach the appropriate wire to the indicator and record the LED readout, at each of the strain gage positions on the arch for each position of the wheel load.
 
 

5.0 RESULTS AND CALCULATIONS
5.1 Data Collection/Results Table

Summarize the recorded data in a simple table.
 

6.0 DISCUSSION
Comment on sources of error and random variation in recorded data. See Experiment S2a for comparisons to be made with theoretical hand calculations as well as numerical computations performed using the finite element method.
 
 

7.0 CONCLUSIONS
See Experiment S2a for conclusions to be drawn.