ABSTRACT
In this paper, we evaluate the effect of uniform and non-uniform temperature on the dynamic parameters of a simplified laboratory scaled aluminum bridge. The model is placed on a climate chamber which can be set to any temperature value from 0 to 40° C. Non-uniform temperature distribution is introduced through two 1000W heaters along the structure.
Results show an increase of uniform temperature has a direct correlation on the decrease of fundamental frequency, with a maximum variation of 0.92% in the temperature range analyzed (Fig. 1). No relationship is found between temperature and damping. Non-uniform temperature distribution (NUTD) only shows a slight variation in fundamental frequency, not considering it a crucial parameter to be studied. Non-uniform and uniform temperature curves comparison. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig83_1.tif"/>
Damage is simulated on a calibrated finite elements model and validated with laboratory testing, where the variation of frequency caused by a severe damage scenario is in the order of variation caused by uniform temperature distribution (Table 1).
Uniform temperature effects should not be neglected, where similar dynamic behavior could represent multiple structural condition scenarios (Fig. 2). To avoid false diagnostics, it is important to include thermal normalizations in the analysis for accurate damage identification. Tests results summary.
Case
Location
Variation (%)
NUTD – 1000 W
L/2
−0.055
NUTD – 2000 W
L/2
−0.131
MASS – 50 g
L/2
−0.272
MASS – 100 g
L/2
−0.535
MASS – 200 g
L/2
−1.102
CUT – 5 mm
L/2
−0.212
CUT – 10 mm
L/2
−0.493
CUT – 15 mm
L/2
−1.075
CUT – 20 mm
L/2
−1.857
Frequency comparison among different scenarios. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig83_2.tif"/>A more complex laboratory scale model is needed to represent the effect of temperature gradients as observed on full scale bridge structures (Farrar et al., 2000).
