r - The Hong Kong Polytechnic University

potential durability (fatigue) problems on the steel deck and its connections with stay cables and the latter will
induce potential stability (static) problems on global bridge structural system. Three types of sensors are
deployed to monitor these two types of potential problems, i.e. (i) dynamic weigh-in-motion stations(or DWIMS)
installed in each traffic lane on both side spans, (ii) dynamic strain gauges on the steel deck plates, webs and
deck trough sections in steel deck sections at towers, 1/4, 1/2 and 3/4 main span, and (iii) video cameras at
tower-tops, mid-height of towers and at deck-levels near the DWIMS. The fatigue problem is monitored by the
DWIMS and dynamic strain gauges and the stability problem is monitored by video cameras, DWIMS and
dynamic strain gauges.
In daily traffic flow monitoring or fatigue damage monitoring, the DWIMS measures two basic data, i.e.
axle-loads and axle-speeds. The software provide by DWIMS would process these two basic data into the
highway loading spectrum diagram on each traffic lane. A software tool, which is customized based on Clauses
8.4 (based on measured traffic data), 11.1, 11.2, 11.3 and 11.4 of BS5400: Part 10: 1980, is used to estimate the
fatigue induced-damage or the fatigue life of a particular structural component basing on the measured
axle-loads and axle-speeds from the DWIMS. This software tool has two options, i.e. simplified vehicular
classification or the 6- vehicle type approach (which is the default in software application) and detailed
vehicular classification or the 20-vehicle type approach. The simplified option is devised to provide quick and
concise information for daily monitoring works and the detailed option is devised to produce more accuracy
evaluation for quarterly (or special event) monitoring reports. The procedures of fatigue damage monitoring are
illustrated in Tables 6, 7 and 8, which are based on the simplified vehicular classification. Fatigue damage
monitoring by strain data are discussed in Paragraph N below.
In traffic jams monitoring or static stability monitoring, the video cameras records the traffic flow and a
software tool is required to classify the recorded traffic flow into 3 conditions, i.e. Condition 1 refers free-flow
traffic, Condition 2 refers to Jammed Traffics with a jammed length of less than 100m, and Condition 3 refers to
Jammed Traffics with a jammed length of greater than or equal to 100m. Further analysis works are solely
required for Condition 3. Another software tool is required to carry out such analysis works, which include: (i)
determining the highway loading spectrum diagram, (ii) determining the positions and vehicle-weights of goods
vehicles in main span, and (iii) analyzing the load-effects on each pre-defined key locations. The flow diagram
of the software tools for highway traffics monitoring is shown in Figure 17.
F. Customized Software Tools for Ship Impacting Monitoring [Ref. 7 and 15]
In Stonecutters Bridge, as the foundation of the towers are located within the reclaimed land at approximately
10m from the cope-line of the seawalls, ship impacting monitoring on towers is therefore required. Ship
impacting monitoring on back-span piers is not required as they are sufficiently remote to be not directly subject
to ship collision loads. The approach for ship impacting monitoring is similar to that in seismic monitoring
except Duhamel Integral is used to determine the shock response spectra of relative displacement, relative
velocity and absolute acceleration rather than the Newmark’s method. The flow diagram of the software tools
for ship impacting monitoring is shown in Figure 18.
G. Customized Software Tools for Permanent Loads Monitoring [Ref. 6, 15 and 24]
The permanent loads monitoring refers to the monitoring of the load-effects on the tower-bases due to dead
loads and super-imposed dead loads. This monitoring work has been started since the beginning of the tower
construction, and the purpose is to monitor the long-term effects of shrinkage and creep on tower deformation.
Static strain gauges (Geokon 4200 – vibrating wire type strain gauge with a measuring range of ±3500με at an
accuracy of 0.1% of full scale and a resolution of 1με) are installed at tower-bases, and in order to have a
sampling rate of 20 Hz, Campbell CR5000 is used as the data acquisition system for all static strain gauges. The
monitoring is carried out by comparing the estimated total strain with the measured strain at tower-bases. The
estimated strain is estimated in terms of structural strains (due to the dead loads and super-imposed dead loads),
the creep strains and the shrinkage strains, which are estimated basing on Structures Design Manual and BS5400:
Part 4: 1990. Both estimated and measured should be calibrated to the same reference temperature (or 20°C used
in this comparison) for comparison. The flow diagram of the software tools for permanent loads monitoring is
shown in Figure 19.
H. Customized Software Tools for Global Static Features Monitoring [Ref. 15]
The global static features monitoring is the measurement of stress and displacement at instrumented points of
GPS and dynamic strain gauges under static and moving vehicular load-trials. This monitoring is scheduled to
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