pile instrumentation datasheet
TRANSCRIPT
8/12/2019 Pile Instrumentation Datasheet
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Technical Data
ApplicationStrain Measurement
Temperature monitoringDatalogging
Static load testingLong term monitoring
Advantages• Accurate strain measurement
• Accurate temperaturemeasurement
• Automated sensor interrogation
• Remote data collection
Various types of pile instrumentation can be used to measure changes in physical
properties of the concrete and steel massof a pile during static load testing orduring long term monitoring. CementationSkanska has extensive experience in theuse of vibrating wire strain gauges, rodextensometers and temperature
measurement and can provide a full in-house service from installation toreporting.
Cementation has installed embedment
and sister bar strain gauges to measure thetransfer of load along the length of the pile during the short term or long term
loading of the structure. Both types ofsensor work on the principle that atensioned wire housed within the sensorwhen electronically plucked will changethe frequency of its response with achange in length. The output frequency of
the sensor is recorded by a dedicateddatalogger.
The embedment or dumbbell gauge(pictured overleaf) is designed to measure
strain in concrete, this vibrating wirestrain gauge is typically tied to a
PileInstrumentation
reinforcing cage. It is usual to install them inarrays of three or four gauges at several depthshorizons within the structure.
The sister bar strain gauge comprises oftwo lengths of ribbed rebar welded to a centralgauge section. The central gauge section has a
miniature stainless steel, vibrating wire straingauge element, fitted along the longitudinalaxis of the gauge. Incorporated within thegauge section are two coils for excitation andoutput of the vibrating wire strain gaugeelement. This type of gauge is particularly
rugged and reliable. They are particularlyapplicable for strain measurements in massconcrete pours where placing of concrete isremote and uncontrolled such as typicallyoccurs in diaphragm walls or deep piles, sincethe instruments are capable of withstanding
impact from tremie pipes and large concreteflows. For installation, the sister bars aresimply tied by soft iron tie wire to an adjacentreinforcing bar. As the sister bars are of longlength, they are readily able to maintain theirorientation to the reinforcing cage
Single and multi-point rod extensometershave been used to as an alternativemeasurement of strain or in conjunction with
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Further information
Cementation SkanskaMaple Cross House
Denham WayMaple Cross
RickmansworthHertfordshire
WD3 9SWUnited Kingdom
Tel: +44 (0)1923 423100Fax: +44 (0)1923 423681
www.skanska.co.uk
OfficesHead Office +44 (0)1923 423100
North +44 (0)1302 821100
South West, Midlands & Wales+44 (0)1454 453200
Scotland +44 (0)1698 735899
Northern Ireland +44 (0)28 9024 2746
Republic of Ireland +353 (0)1296 0790
strain gauges. Extensometers are steeltubes attached to the reinforcement cage
and cast into the pile. Rods are theninserted into the steel tubes, these rodswill behave independently of the steeltubes as the pile is loaded. The rod
appears to protrude from the top of thesteel tube as load is increased and thismovement can be accurately measuredusing displacement transducers. Multiplerod extensometers can measure strain atdifferent levels. Temperature monitoring
using thermocouples has been used todetermine the temperature profile during
curing of the concrete mass.
We also has extensive experience inthe interrogation on large numbers ofsensors by dedicated datalogging systems.
For example 260 strain gauges have beeninstalled in 8 piles at the Bankside 123
project, London. These sensors areinterrogated every hour by threenetworked dataloggers with remote accessusing GSM technology to allow data
collection from the Maple Cross office.
PileInstrumentation