bridges

Integrity has pioneered the use of computer measured multiple velocity transducers for testing of bridges. Now with over five hundred bridges tested, Integrity Testing is among the most experienced bridge testing and evaluation companies. Some examples are here.

We not only undertake "electronic " testing of structures but complement it with traditional methods.We have experience on both rail and road.

We have tested over five hundred bridges of nearly all shapes and types ranging from just constructed pc stressed beam to over 100 year old cast iron trellis. Our testing principle looks at the bridge as an equivalent beam. With suitable excitation only basic parameters of the bridge deck are required to be known. As long as we know the span length we can determine the EI and mode deflection shape of the deck from the test..

Graphic displays of bridge mode deflection shapes together with intelligent AI look up of frequency tables enables accurate determination of bridge capacities.

Technical

The basic principle is given in the graphic, basically instead of measuring the structural stiffness by load testing, typically d = (constant * mass * length²)/EI dynamically you measure f= (constant/length²)*

Measurement of displacement is not accurate and at best measuring to 0.01 (mm) out on a bridge is hard to do, where as time (frequency) to 0.000001 (s) common place. Most computers run at 10 Mhz. and faster. The looking at the errors in the formulation, EI is approximately X.XX x 10^9 commonly for bridges which gives the measurement of frequency as sqrt (10^9), five orders of magnitudes more accurate in determining EI that by deflection methods.

Typical out put is given, a defect at the top right corner can be seen

	The support piers for this bridge are made out of cast iron! The decking is local hard wood dressed with a sealer. The bridge spans a 30m (100') ravine and is used mainly by logging trucks and farm related traffic.
The testing showed that the bridge had the capacity to meet with the new axle loads to be imposed. A definite case of foresight as the bridge is over 100 yrs old !

Original plots and in depth description are available on request.