r - The Hong Kong Polytechnic University

correlation plots of wind vs acceleration and/or dynamic strain results. The second type is deployed for the
monitoring of horizontal winds above 45 m/s and for the correlation analysis of wind vs displacement and/or
static strain results. The third type is deployed for the monitoring/calibration of the horizontal wind directions
determined by the ultrasonic anemometers. The first and second types are also deployed for the monitoring of
the wind turbulence coherence characteristics by installing the anemometers around 20~30 meters apart from
each other (longitudinally – or along the bridge-deck alignment). The barometers (RM Young 61202) and
rainfall gauges (Casella 103800D) are deployed for the calibration of and/or making references to the wind
speeds taken by the anemometers, in particular under the condition of extreme heavy rains.
The functions of the software tools for wind and weather monitoring are : (i) to derive the relevant wind and
weather monitoring parameters such as wind turbulence characteristics, the frequency response functions and
the correlation plots of wind vs responses, and (ii) to output the measured/derived results in the standardized
format of four –in-one format, i.e. 3 graphs and 1 table on one page. The 3 graphs are location plan of bridge
site, location of sensors in bridge, graphical report of monitoring results, and a legend-table to monitoring results,
as shown in Figures 32-39 and 43-45. The flow diagram of the software tools for wind and weather monitoring
is shown in Figure 11. In Figure 11, the fundamental wind data analysis should be carried out first before the
execution of other types of analysis. The details of this fundamental wind data analysis are tabulated in Table 5,
as an example of fundamental wind data analysis for wind data collected from 3D ultrasonic type anemometers.
B. Customized Software Tools for Temperature Monitoring [Ref. 15, 17 and 24]
The temperature monitoring in Stonecutters Bridge is devised to monitor the temperature in five types of
materials, i.e., structural steel sections (steel deck sections and steel tower skin sections), structural concrete
sections (concrete deck sections and concrete tower sections), cable steel sections, air (un-shaded, shaded, and
inside section) and asphalt pavement. Due to different installation requirements and measuring materials, the
temperature sensors are classified as seven types, i.e. TMU-1, TMU-2, TMU-3, TMU-4, TMU-5, TMU-6 and
TMU-7. TMU-1 and TMU-2 are both for structural steel temperature measurement, in which the former is bolt
fixed type and the latter is bond mount type. TMU-3 and TMU-4 are both for structural concrete temperature
measurement, in which the former is for tower and the latter is for deck. TMU-5 is for cable steel temperature
measurement. TMU-6 is for air temperature and relative humidity (thermo transmitter type) measurement.
TMU-7 is for asphalt pavement temperature measurement. All temperature sensors are Class A Platinum
Resistance Thermometry except TMU-5 which is distributed optical fiber sensors (based on Raman scattering
process).
Two major parameters are required for temperature monitoring of structural steel sections and they are the
effective temperature and the differential temperature. In order to derive these two parameters in the orthotropic
steel deck section, the temperature sensors should be distributed along the top and bottom deck plate-trough
sections and the web plates. The computational method for effective and differential temperatures basing on
such arrangement of temperature sensors is shown in Figure 12. In a similar way, the effective temperature and
differential temperatures in structural concrete sections are determined. Differential temperature in steel cable,
tower skin and asphalt pavement is not required (as the respective diameter, thickness and depth are comparative
small) and only the average (or effective) temperature is required. The effective temperature is normally used to
estimate the thermal movement of the structural component and to calibrate/eliminate thermal effects for other
aspects of monitoring such as stay forces monitoring. The flow diagram of the software tools for temperature
monitoring is shown in Figure 13.
C. Customized Software Tools for Seismic Monitoring [Ref. 10, 15 and 17]
In an earthquake, no actual force is applied to the bridge. Instead, the ground moves back and forth (and/or up
and down) and this movement induces inertial forces that then deform the bridge. It is the displacements in the
bridge, relative to the moving base, that impose deformations on the bridge. Through the elastic properties, these
deformations cause elastic forces to develop in the individual members and connections. Earthquake ground
motions usually are imposed through the use of the ground acceleration records. In Stonecutters Bridge, if an
earthquake with a Modified Mercalli Scale of 5 or more is occurred, the time-series acceleration data at
tower-base will be used to generate the response spectrum of the bridge at a certain level of damping (which is
5% according to Design Memorandum of Stonecutters Bridge). The spectrum is obtained by repeated solving
the dynamic equilibrium equations (expressed in terms of bridge’s circular frequency) by Newmark’s method
with the input of the recorded time-series acceleration data (in a time increment of 0.02 seconds) for the bridge
with various circular frequencies and then plotting the peak displacement obtained for that circular frequency (ω)
versus the frequency for which the displacement was obtained. The velocity (or pseudo-velocity) response
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