Structural Health Monitoring: Instrumentation and Planning for Project Teams

Structural health monitoring uses measurements collected over time to help engineers understand how a structure or component is behaving.¹ This guide focuses on strain, local movement, tilt and load, measured using strain gauges, crack meters, joint meters, tiltmeters and load cells. These measurements inform engineering review; they do not, by themselves, establish the condition or safety of the whole structure.

Start with the structural question: which component and behaviour matter, where and in which direction should they be measured, and what reference conditions will the responsible engineer need? Answering those questions helps a project team prepare a useful monitoring brief before choosing equipment.

In this guide: Monitoring objectives · Measurements and instruments · Location and coverage · Baselines and context · Review and escalation · Installation and handover · Preparing an enquiry.

What should structural monitoring help you understand?

Define the structural question and intended use of the measurements

A useful objective names both the behaviour of interest and the intended use of the information. “Monitor the building” leaves too much unresolved. A more useful objective identifies a particular component, what change needs investigation and the project stage during which that information matters.

Define the objective: Identify the asset and component; describe the behaviour to investigate; state the relevant construction or operating stage; and nominate the technical decision-maker who will use the results. Then connect that objective to the measurement-and-interpretation matrix below.

Illustrative example—not a TERRASENSE project: A team wants to establish whether a particular joint is opening or closing during a construction stage. Relative movement across that joint is relevant. The brief still needs to identify the joint, measurement direction, reference state and engineer who will interpret the observations. It does not yet justify a conclusion about the rest of the structure.

Separate monitoring information from structural assessment

Measurement, interpretation and assessment are different tasks. A reading describes the monitored quantity at its recorded location and time. Explaining its significance requires the structural question, relevant asset information and the assumptions used in the assessment.

A US bridge-research report illustrates this distinction by treating structural modelling, sensor selection, sensor placement and data analysis as separate parts of developing a monitoring system. It is useful methodological context, not Australian regulatory guidance.¹

A structural monitoring brief should therefore state what the measurements are intended to inform and what they cannot resolve alone. It should not diagnose the cause of a crack, prescribe repairs or replace inspections and engineering assessments required for the project.

Which instruments measure strain, movement, tilt and load?

Strain gauges and load cells

Strain gauges measure deformation relative to a measurement length. Strain is the change in length divided by the original length, in the direction being considered. It is not force. Bending can produce extension on one side of a member and shortening on the other, so the position and orientation of the gauge matter.²

The attachment arrangement connects the gauge to the member being measured. In the documented Model 4000 example, different end arrangements allow attachment to steel or concrete. The appropriate connection depends on the instrument and host material; one attachment method is not suitable for every asset.³

Load cells measure force applied to the cell. In the annular, or ring-shaped, arrangement documented in the cited manual, tension in an anchor produces compression through the cell between bearing surfaces. The result concerns force transmitted through that arrangement, not every load acting on the structure.⁴⁵

Neither a local strain reading nor a load-cell reading directly states the remaining capacity of a structure. Converting measurements into a structural conclusion requires an appropriate engineering model and relevant information about the asset, rather than a change of units alone.

Crack meters, joint meters and tiltmeters

Crack and joint meters measure relative movement between defined points. The names overlap: the surface crackmeter arrangement documented here can span either a crack or a joint. Movement is measured between its attachment points along the instrument’s axis; one monitored direction does not describe every movement component.⁶⁷

An embedded jointmeter is a different installation arrangement. In the construction-joint example documented for Model 4400, the instrument is anchored in successive concrete placements. Selection therefore depends on the construction sequence as well as the movement of interest.⁸⁹

Tiltmeters measure angular inclination, rather than distance. The cited Model 6190 example measures static tilt; the relevant axes and their positive directions depend on its mounting orientation.¹⁰¹¹ Tilt is not a direct settlement measurement: vertical movement can occur without rotation. Inferring displacement from an angle requires additional geometry and justified assumptions.

The following matrix connects each category to its measurement and limits. The cited models illustrate arrangements; they are not a recommendation for a particular project or confirmation of TERRASENSE stock.

Where should measurements be taken, and what will they cover?

Identify the component, location and direction of interest

A measurement location needs a clear relationship to the structural question. Convenient access alone does not establish useful coverage: sensor placement is part of monitoring design.¹

Identify locations on an appropriate drawing or annotated record. “Joint movement” is incomplete without identifying the joint and direction. “Member strain” needs the member, face and orientation. For tilt channels, connect the recorded axis and positive direction to the installed sensor, not merely its label in a dashboard.¹¹

Account for mounting, access and unmonitored areas

The location plan also needs to account for physical access and the permitted attachment arrangement. An instrument accessible during installation may be difficult to inspect or protect after the next construction stage. Record those constraints alongside the areas and directions the system will leave unmonitored.

Location-and-coverage check:

• Record the component, face, precise location and measurement direction, with the structural information used to select them.
• Confirm the proposed mounting is compatible with the asset, and identify access, protection and later inspection constraints.
• State which components, directions and areas are not monitored, including any gap caused by access restrictions or construction sequencing.

An unchanged reading only describes the measured quantity at that monitored location. It should not be reported as proof that nothing changed elsewhere. The brief should make that coverage boundary visible to anyone reading the results.

Why do baseline readings, temperature and loading conditions matter?

Document the reference state and existing condition

A baseline is the documented state against which later observations are compared. It is not automatically an unloaded condition or evidence that the asset was undamaged. A newly installed instrument cannot supply the missing measurement history from before its installation.

Construction stage can be particularly important for an embedded instrument. For the embedment jointmeter described above, the manual distinguishes readings before the subsequent concrete placement and after curing. That illustrates why “initial reading” needs an installation-stage description; it is not a universal baseline schedule for other instruments.⁹

Keep these records with the baseline:

• Instrument and channel identity, location, orientation, units, date and time, and the selected reference reading.
• Installation and commissioning state, relevant calibration information, temperature observations, and known loading or construction conditions.
• Available condition surveys, drawings and photographs, together with any missing earlier information or unresolved assumptions.

Keep the original reference identifiable when later readings, instruments or configurations change. Record what changed rather than silently substituting a new starting point.

Interpret changes alongside environmental and operating information

Temperature can affect both the measuring system and the structure. Instrumentation effects can arise from the gauge’s thermal behaviour or a temperature difference between gauge and host. Separately, a member can expand or contract; restraint can turn that tendency into a stress response. Temperature-related change is therefore not simply unwanted noise.¹²

The cited vibrating-wire strain-gauge manual treats thermal response, external loading and restraint separately, with different assumptions for steel and concrete.¹² Record the relevant temperature and operating conditions, then establish what the reported quantity represents. Removing every temperature-related trend could discard real structural behaviour; leaving every trend unexplained could mislabel change as damage. Neither approach justifies a generic correction across different instruments and structures.

How should readings, technical review and escalation work together?

Define measurement timing and data-quality checks

A reading schedule needs to suit the behaviour being investigated. Discuss gradual trends and rapidly changing events separately, and have the technical team confirm that the proposed instrument, readout or logger and review process can address the intended behaviour. Remote connectivity alone does not establish that capability.

Distinguish when a measurement is acquired, when it becomes available and when it is reviewed. Remote systems depend on the configured logging, communications and platform arrangements. The remote monitoring and data-services scope also needs to address interruptions, reporting, notifications, access, licensing, retention and data ownership.

Agree how missing, inconsistent or suspect readings will be handled. Investigation may need to examine the measurement chain as well as the structure: the cited vibrating-wire crackmeter guidance identifies connections, electrical interference and readout configuration as possible causes of unstable readings.⁷

Agree interpretation, thresholds and response responsibilities

For each part of the review process, agree an owner:

Measurement requirements: Name the person who approves the monitored quantities, locations, timing and reference conditions.

Data-quality checks: Name the person who checks missing or suspect information and records unresolved faults or exclusions.

Technical interpretation: Name the engineer or other appropriately responsible technical reviewer who assesses trends against the structural question and relevant conditions.

Escalation and action: Identify who receives an issue, who has authority to decide the response, and what happens when the nominated person or data service is unavailable.

Thresholds need a project-specific technical basis. A notification reports that a configured condition has been met; it does not decide whether the structure is safe. For TERRASENSE remote-monitoring engagements, alert delivery is best-effort and depends on the agreed system and third-party communications. The response arrangements must account for missed or delayed notifications; an alerting system is not a commitment to continuous supervision.

TERRASENSE’s reporting and interpretation services are defined by the agreed engagement. Data provision does not automatically include engineering interpretation; interpretation can be specifically commissioned within the instrumentation and monitoring scope. Final engineering design decisions and certification remain with the client’s nominated engineer or consultant. Instrumentation support is not structural design certification or statutory approval.

What should installation, commissioning and handover cover?

Confirm asset access, installation constraints and compatibility

Installation planning turns the proposed measurement locations into an agreed, workable arrangement. Asset-owner permissions, site restrictions and construction activities need to be resolved with the person approving the installation method.

Before installation, agree:

• Who approves the proposed locations and attachment arrangement, including compatibility with the asset and any restrictions on modifying it?
• What access windows, sequencing and protection are needed for instruments and cables during installation and subsequent work?
• What evidence and checks will demonstrate that the installed arrangement is suitable for the agreed measurement purpose?

A factory calibration certificate does not establish the performance of the complete installation. In the annular load-cell example, bearing friction and loading conditions affect how calibration applies in the field.⁵ Installed-system acceptance therefore needs the agreed checks as well as the instrument’s calibration record.

Document the installed system and its ongoing responsibilities

The handover record should let a later reader trace each reported value to the installed instrument and its measurement basis. Agree these records and acceptance responsibilities before installation.

At handover, confirm:

• Installed arrangement: instrument identities and as-installed locations, directions, mounting records and any approved departures from the proposal.
• Measurement basis: relevant calibration records, reference readings, units, sign conventions and documented calculations or corrections used to produce reported values.
• System configuration and checks: channel mapping, applicable readout or logger settings, agreed commissioning results, and any outstanding limitations or faults.
• Ongoing ownership: responsibility for inspections, maintenance, configuration changes, replacement instruments, reference changes, data access and technical review.

Supply-only and turnkey delivery can allocate these responsibilities differently. Confirm which installation, commissioning, maintenance and support activities are included in the agreement, and who owns the remainder.

What information should you include in a structural monitoring enquiry?

Describe the structure, concern and available records

Lead with the asset and the question you need monitoring to inform. Identify relevant drawings, existing-condition information and previous monitoring records where available. You can state that detailed records exist without placing sensitive engineering documents in a public enquiry form; agree an appropriate exchange route when needed.

This structural information complements the overall monitoring brief: it connects the concern to the measurements and records needed for a useful technical discussion.

Clarify the requested monitoring and delivery scope

Use this enquiry checklist to describe what is known and what still needs to be resolved:

• Asset and question: asset type and location, structural concern, and the component or locations of interest.
• Available evidence: relevant drawings, condition records and earlier measurements, including known gaps.
• Timing: project or construction stage and anticipated monitoring duration.
• Site constraints: access restrictions, installation requirements and existing instrumentation.
• Information needed: reporting requirements and the intended use of the results.
• Responsibility: the nominated technical decision-maker and the supply, installation, data-service or interpretation support being requested.

Mark uncertain inputs as unresolved. Do not invent sensor quantities, measurement ranges or trigger values simply to make the enquiry appear complete.

Discuss these five structural instrument categories with TERRASENSE on a by-enquiry basis, with suitability, availability and lead time to be confirmed for the project. Turnkey instrumentation and monitoring enquiries are welcome. Consultation is available on request; field-service availability and inclusions depend on project location and the agreed scope.

Discuss Your Project — describe the structure, the behaviour you need to understand and the information already available.

Public references

1. Kong, Z. (James), Ley, T. and Liu, T. Development of a Structural Health Monitoring (SHM) Guidebook for Critical Bridge Structures. Oklahoma Transportation Center / Oklahoma State University, report OTCREOS9.1-29-F, July 2013. Executive Summary, printed pp. x–xi; §1, printed p. 1; §4.1, printed p. 16. Full report: https://rosap.ntl.bts.gov/view/dot/27050/dot_27050_DS1.pdf . Repository record: https://rosap.ntl.bts.gov/view/dot/27050 . US bridge research, not Australian regulatory guidance.

2. NI. Measuring Strain with Strain Gages. Sections “What is Strain?” and “Measuring Strain”. https://www.ni.com/en/shop/data-acquisition/sensor-fundamentals/measuring-strain-with-strain-gages.html . The definition of strain is used here; the page’s electrical-gauge discussion is not a description of every strain-gauge technology.

3. GEOKON. Arc Weldable (VW) | Model 4000. Product description, including steel and concrete attachment arrangements. https://www.geokon.com/4000 . Model-specific configuration information, not a universal installation method.

4. GEOKON. Load Cells (VW) | Model 4900. Product description and “Specifications” qualification concerning end-loading conditions. https://www.geokon.com/4900 .

5. GEOKON. Model 4900 Vibrating Wire Load Cell Instruction Manual. Revision CC.4, 6 May 2026. §1.1 and Figure 1, printed p. 1; §1.2, printed pp. 2–3; §§1.2.1–1.2.2, printed p. 4. https://www.geokon.com/content/manuals/4900_Load_Cell.pdf . Applicable to the documented annular load-cell and bearing arrangements.

6. GEOKON. Crackmeters (VW) | Model 4420. Product description: surface crack and joint movement. https://www.geokon.com/4420 .

7. GEOKON. Model 4420 Vibrating Wire Crackmeter Instruction Manual. Revision X.6, 13 April 2026. §1, printed p. 1; §3.1, printed p. 3; §6.1.1, printed p. 13; §7, printed p. 17. https://www.geokon.com/content/manuals/4420_Crackmeter.pdf . Surface-mounted measurement and model-specific troubleshooting context.

8. GEOKON. Embedment Jointmeters (VW) | Model 4400. Product description: movement across construction joints. https://www.geokon.com/4400 .

9. GEOKON. Model 4400 Vibrating Wire Embedment Jointmeter Instruction Manual. Revision L.2, 26 September 2024. §1, printed p. 1; §2.3, printed pp. 3–4; §2.7, printed p. 5. https://www.geokon.com/content/manuals/4400_Embedment_Jointmeter.pdf . Construction-joint installation and reference-reading context, not instructions for every joint-monitoring arrangement.

10. GEOKON. Tilt Sensor (Triaxial MEMS) | Model 6190. Product description and mounting context. https://www.geokon.com/6190 .

11. GEOKON. Model 6190 Tilt Sensor (Triaxial MEMS) Instruction Manual. Revision B.3, 11 September 2026. §1, printed p. 1; §§2.3–2.4, printed pp. 2–3; Appendix E, printed p. 23. https://www.geokon.com/content/manuals/6190-Tilt-Sensor-Manual.pdf . Static inclination, installation orientation and axis/sign conventions; not a claim of dynamic response or direct settlement measurement.

12. GEOKON. Model 4000 Series (4050 included) Vibrating Wire Strain Gauges Instruction Manual. Revision GG.3, 14 May 2026. §4.6, printed p. 10; Appendix E, printed pp. 28–29; Appendix F, printed p. 30. https://www.geokon.com/content/manuals/4000_Strain_Gage.pdf . Temperature interpretation is specific to the documented gauge, host material, restraint and loading assumptions.