EIF Wiki

Strain Gauges (SG) sensors and Ion Selective Electrodes (ISE) measuring Chloride Ions (CI) were cast into the concrete slab, columns, shear walls, footings and link bridges at strategic locations during construction of the Broadway Building.

Data cabling was routed back to a centrally located datalogger (DataTaker DT80) located on each instrumented level.

The three-core cable from the SG was connected into the DT80 (see DT8x User Manual p293, R2 - 3-wire resistance inputs). SG's were placed longitudinally and transversally to the building long axis. A series of SG's have been nominated for rain-flow analysis.

The ISE's (reference reading) are wired via 2-core cable to the DT80 (R4 - 2-Wire Independent Resistance Inputs). Additional single-wire electrodes (excite and calibrate readings) were added adjacent to the ISE to allow future potentiometric measurement.

All readings can be calibrated against level 6 sensors (which are located in the middle of the building and considered baseline). A full breakdown of the naming conventions can be found here.

The two sensors output the following readings:

• ISE reading (mV): Voltages between zero to -2000mV indicate a normal level of chloride. Readings become further negative as chloride count goes up. Readings beyond -3000mA indicates a structurally-dangerous chloride presence.
• SG reading (mA): The milliamp reading alone has little use. We have a suggested methodology for calculating strain (ppm) from the raw readings here. The raw readings are supplied for you to apply your own methodologies.

Sensors are located in the following places throughout the building concrete construction

• Slabs (self-explanatory)
• Columns. 3 Strain Gauges are used in combination in columns. Floor columns are placed between floor levels and gauges are placed at the extreme bottom, top and centre of the column in a vertical line
• Footings (self-explanatory)
• Shear Wall. A shear wall is a continuous concrete wall from the top of the building down to the bottom of the building and are usually part of the fire stairwell or lift voids. Sensors are placed in the same manner as for columns. Shear Walls are so-called due to the nature in which they crack or split under extreme applied forces, such as an earthquake.
• Link Bridges. Connecting Building 11 and Building 10 at levels 3,5 and 7. Bondek structural steel is used for the link bridges, and there has been an expressed interest in monitoring this type of building construction method. Strain Gauge sensors (2) are placed in the centre of the bridge, with 1 gauge fixed to the reinforcement bar and the other, directly to the Bondek.

Embedded Sensor Names are in the following format e.g. SG.03SW.92B

• SG: Strain Gauge (CI-Chloride Ion)
• 03: Level 03 (Building 11)
• SW: Shear Wall (S-slab, C-column, L-link bridge, FTP-footing)
• 92: Sensor number 92
• B: Located at Bottom of wall section (C-located in center, T-located in top)

or CI.13S.B277L

• CI: Chloride Ion (ISE counts chloride ions)
• 13: Level 13 (Building 11)
• S: Sensor in Slab
• B: Black cable (for potentiometric future use) (W-white cable, R-red cable)
• 277: Sensor number 277
• L: Longitudinal (sensor is placed longitudinal to building long axis), (T-transverse to building long axis)

….you may also find the following name format, rSG.B4SW.201B

• rSG: r means this sensor has been earmarked as of interest for Rainflow Analysis (see downloads)
• SG: Strain Gauge
• B4: Level B4 (Building 11)
• SW: Shear Wall
• 201: Sensor number 201
• B: Bottom section of the Shear wall

Sensors in the Bondek use the following name format SG.03L.187BL

• SG: Strain Gauge
• 03L: Level 3 Link bridge
• 187: Sensor number 187
• B: Sensor fixed to Bondek
• L: Sensor is placed Longitudinal to the bridge long axis

Another rare sensor you may notice is TP.B1S.3

• TP: Test Point. A wire connection directly fixed to the concrete reinforcement steel has been bought out to a handy connection point in the column
• B1: Level B1 (Building 11)
• S: Slab
• 3: Test Point 3

• DT80 Technical Sheet
• DT8x User Manual
• Sensor Test Data and Certificates
• Floor Plans with sensor layout location
• Methodology
• Multiple Quarter Bridge Completion Circuit
• Rainflow Counts
• Fatigue and Rainflow Analysis
• Rainflow Cycle Distribution - Thesis
• What does a Strain Gauge look like?
• What does an Ion Selective Electrode (ISE) look like?
• Bondek User Guide
• Gauge Mounted to Column Steel
• Gauge Data Cables leave Slab
• Toby Boxes used to Bring data cable from Shear Wall
• Sensor Bar seen in Column Steel