Civil Engineering Reference
In-Depth Information
13.2 Field-Testing Methods
In this study, various field testing systems were utilized to obtain the actual strain, deflection and velocity data. Various types
of sensors and data acquisition systems were instrumented on a selected 12.2 m long, open deck steel girder railway bridge.
The bridge supports two active tracks using four girders that allow two-way traffic. The field instrumentation includes
Structural Testing System (STS) and the Laser Doppler Vibrometer (LDV). A typical testing plan is shown in Fig.
13.2
.
The Structural Testing System (STS), which measures the strain in structural members, is a modular data acquisition
system manufactured by Bridge Diagnostics, Inc. (BDI) of Boulder, Colorado. The system includes three parts: strain
transducers, junction nodes, and a main unit. The strain transducers shown in Fig.
13.3a
were mounted on structural elements
and connected with the junction nodes. Each strain transducer is assigned a unique number that can help to recognize the
location of the transducer easily in the computer software when operating the test. The junction nodes shown in Fig.
13.3b
can transfer the data from strain transducer to the main unit (Fig.
13.3b
) that produces wireless signal. The junction nodes
were placed on the pier of the tested span. The main unit is a processing unit that samples data and was placed between the
junction nodes and the computer to allow control the system remotely by the operator.
Fig. 13.2
Field testing plan for a typical span of selected bridge
Fig. 13.3
(
a
) Strain transducers on the girder; (
b
) Junction nodes and main unit of STS; (
c
) Laser Doppler Vibrometer mounted to a tripod,
Decoder unit; (
d
) Reflective tape on structural element
