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shown on-line by the software DACview of SMS. SMS can store the data from the four kinds of
sensors for one year. And based on the real-time data, the preprocessing program installed in the
workstation of the bridge can separate the strain and displacement data into two parts as either the
traffic effect or the temperature effect. The acceleration and temperature data also will be preprocessed
for the purpose of efficiency. Moreover, SMS can automatically analyze and calculate the daily,
weekly, monthly and annual statistical data.
i
j
Bending Stttfness
Max/Mm strains
Strain |
FEM Updating
Number ot trucks
Real-time Display
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Young s Modulus of concrete Truck Speed
Data stored tor tracking (one vear)
Compare to preset values
Truck Weight
Data pre processed for efficiency
Warning for abrupt change
v earlv monthly weekiv and daily summary Traffic Effect
Temperature Effect
Max/Mm strains
Strain/degree change( "C )
Real time Display
Stress in Shear Reinforcement
Data stored for tracking (one year)
Max/Mm crack opening displacement
Shear Stiffness
Number of trucks
Data pre processed tor efficiency
Compare to preset values
Yearly monthly, weekly and daily summary
Truck Weight
Acceleration
Real-time Display
Data stored r or tracking (one year)
Traffic Effect
Temperature Effect
Warning for abrupt change
Max/Mm crack opening displacement
Displacement/degree change
Data pre processed tor efficiency
Max/Mm G level
Yearly monthly weekly and daily summary
Frequency Analysis (the first 5 frequencies)
'—i*j Temperature j
Compare to preset frequency at prescribed temperature
Red-time Display
Warning tor unusual change of acceleration (Traffic lam or accident)
Data stored for tracking (one year)
Data pre processed for efficiency
Yearly monthly weekly and daily summary
Max/Mm temperature
Inside/outside difference
Outside/concrete difference
Warning tor unusual change of temperature
Fig. 4 Flow Chart of Smart Monitoring System
3.1 Strain Data Analysis
Due to the traffic and temperature effect, strain data were preprocessed and separated into two parts, as
shown in Figure 5 and Figure 6. Based on the relationship between strain and truck weight, we found
that a strain record over 4 microstrain represents a truck passing through the location of the strain gage.
In order to verify the threshold of strain, the actual number of trucks and the time when the trucks
passed the bridge were recorded on March 30, 2002 from 2:00 pm to 3.00 pm. Figure 7 shows the
comparison between these two records of truck numbers. In addition, it can be observed that the onthe-spot
record matches the result from the strain analysis. Since strain gages are located on SB2-N16
and SB2-S16 and the distance between these two locations is known to be 225.6 ft, the speeds of
trucks can be obtained by calculating the time difference between two strain peaks at these two
locations. Figure 8 presented the record of truck speed in March 2002. As observed in the figure, one
truck's speed is 51.3 m/h. According to the load test in 2000, the maximum positive strain in the web
of the segment SB2-S16 of Kishwaukee Bridge, under two three-axles trucks each weighing 96,000
Ibs, turned out to be 24 microstrain. And the maximum was 16.92 at the same location. Tablet shows
the comparison of monthly maximum strain and curvature with the result of Load Test. As shown in