IEEE 693 & Telcordia Seismic Standards with Biaxial Tables

IEEE 693 and Telcordia GR-63-CORE help engineers determine whether electrical substation and telecommunications equipment can withstand earthquake-related movement. Biaxial shake tables can provide a cost-effective solution for suitable seismic qualification tests. Still, the required test axes, motion, equipment configuration, and acceptance criteria must be checked against the applicable standard.

Selecting the perfect testing setup involves much more than simply measuring the maximum force a shake table can produce. Through properly engineered testing systems, the equipment must precisely experience the intended motion, remain firmly anchored, and fully meet all structural and operational performance criteria from start to finish.

What Are IEEE 693 and Telcordia GR-63 CORE?

IEEE 693 and Telcordia GR-63-CORE address seismic performance in different industries. IEEE 693 focuses on electrical substations and power equipment, while GR-63-CORE establishes physical protection requirements for telecommunications equipment and network facilities.

Both standards help engineers plan tests, evaluate equipment response, and document whether specified requirements have been met.

What IEEE 693 Covers

IEEE 693, Recommended Practice for Seismic Design of Substations, provides guidance for seismic design and qualification of substation structures and electrical equipment. It addresses seismic criteria, qualification methods, performance levels, equipment operation, installation, and documentation.

Depending on the equipment and qualification method, engineers may need to evaluate control cabinets, instrument transformers, switchgear, disconnect switches, and other substation components. The objective is to establish that the equipment can withstand the specified seismic demand and meet its required performance criteria.

When planning a test, use the applicable edition and amendments. IEEE 693-2018 has Amendment 1, IEEE 693a-2024, which addresses selected equipment, response spectra, time histories, and qualification methodologies. Confirm which version the project specification requires before preparing the test plan.

What Telcordia GR-63-CORE Covers

Telcordia GR-63-CORE is part of the Network Equipment-Building System (NEBS) requirements used for telecommunications equipment. It addresses physical and environmental conditions associated with network facilities, including seismic performance.

Typical test articles include telecommunications racks, equipment cabinets, servers, network switches, and assemblies mounted within a rack. Testing can evaluate whether the frame, anchorage, mounted components, and required equipment functions withstand the prescribed earthquake motion.

The required qualification depends on the product, the relevant standard edition, and the network operator’s specifications. A laboratory report should clearly identify what was tested and which requirements were evaluated. A general statement that a product is “earthquake tested” does not establish compliance with every NEBS requirement.

Key Differences Between the Two Standards

The standards should not be treated as interchangeable. If a product is sold into both power and telecommunications applications, its manufacturer should review each customer’s requirements separately.

Why Use a Biaxial Shake Table?

A biaxial shake table applies controlled motion along two perpendicular axes, typically in the horizontal plane. It can help laboratories evaluate how equipment responds to earthquake-like movement without requiring a three-axis system for every test.

For laboratories testing electrical cabinets, control panels, and telecom racks, biaxial equipment may offer a practical balance between capability, floor space, operating complexity, and cost. However, the table must reproduce the required test motion at the actual specimen mass.

What a Biaxial Shake Table Does

A biaxial shake table moves a securely mounted test specimen along two axes using precision shake table components and backlash-free swivels. The system follows a specified motion profile via dedicated control software while sensors record the motion delivered to the table and, where required, the equipment’s response.

A typical test involves:

1. Mounting the specimen using the specified fixture and anchorage.
2. Installing accelerometers and other required sensors.
3. Checking the table’s operating limits and control settings.
4. Applying the prescribed seismic input.
5. Monitoring the equipment for damage, movement, or functional problems.
6. Comparing recorded data and inspection results with the acceptance criteria.

For example, a loaded electrical cabinet may look sturdy while sitting on a laboratory floor. Under earthquake motion, however, its frame, mounting rails, doors, and internal components can respond differently. Shake-table testing allows engineers to investigate those responses under controlled conditions.

When Biaxial Testing Is Suitable

Biaxial testing may be suitable when the governing procedure permits horizontal excitation along two perpendicular axes and does not require simultaneous vertical input.

Common applications include:

• Electrical cabinets: Checking frame integrity, mounting rails, fasteners, and component retention.
• Telecommunications racks: Evaluating rack stability and the security of installed network equipment.
• Industrial control panels: Examining structural response and the continued operation of essential controls.
• Selected substation components: Testing equipment where the applicable qualification procedure supports the proposed biaxial setup.
• Engineering research: Studying horizontal seismic response in structural models and equipment assemblies.

The complete specimen matters. A cabinet tested without its normal internal equipment may have a different mass distribution and natural frequency from the production configuration. If the intended application uses a fully loaded assembly, the test plan should account for that arrangement.

When Triaxial Testing Is Required

A triaxial shake table can apply motion along three axes, including the vertical direction. Use it when the applicable procedure requires vertical excitation or when the test objective specifically involves combined horizontal and vertical response.

Vertical acceleration can change axial forces in columns, alter connection loads, affect foundations and supports, and influence equipment with sensitive moving parts. For some structures, these effects can influence stability or the performance of critical components.

For instance, a heavy electrical assembly may experience substantial horizontal forces while its supports also experience changing vertical loads. If the qualification needs to assess those combined effects, horizontal-only testing may not provide sufficient evidence.

Before selecting a biaxial table, confirm:

• The required test axes and whether excitation must be simultaneous.
• Whether vertical motion affects the expected equipment response.
• The applicable standard edition and qualification method.
• Whether separate-axis tests are allowed by the specified procedure.
• The table’s payload, displacement, acceleration, and frequency capabilities.

A biaxial table is not automatically acceptable for every seismic qualification, and a triaxial table is not automatically required for every test. The governing procedure determines the correct configuration.

IEEE 693 Seismic Qualification With Biaxial Tables

IEEE 693 seismic qualification evaluates whether substation equipment meets the requirements specified for its intended application. A biaxial table can support suitable tests, provided the proposed test arrangement complies with the applicable qualification method.

Required Response Spectrum and Test Levels

A required response spectrum (RRS) defines the target structural response across a range of frequencies. It specifies the seismic demand the test motion must represent.

Peak acceleration alone does not describe an entire earthquake input. Frequency content, duration, displacement, and the equipment’s natural frequencies also influence a specimen’s response. A test can therefore reach a target peak acceleration yet still fail to reproduce the required response spectrum.

IEEE 693 provides qualification approaches and seismic performance levels. The applicable test requirements depend on the equipment category, qualification method, project specification, and relevant standard edition.

The laboratory should check that its shake table can reproduce the required motion with the actual specimen and fixture installed. Maximum payload, maximum acceleration, and maximum displacement are separate specifications; they are not necessarily available at the same time.

Equipment Types Covered by IEEE 693

Equipment that may require seismic evaluation under IEEE 693 includes:

• Substation control and protection cabinets.
• Instrument transformers.
• Selected circuit breakers and switchgear.
• Disconnect and grounding switches.
• Electrical control assemblies and supporting structures.
• Other equipment covered by the applicable qualification provisions.

The qualification route can differ between equipment types. Depending on the standard and project requirements, evidence may come from physical testing, engineering analysis, or an approved combination of methods.

Mounting conditions are particularly important. A component secured to a rigid laboratory fixture may behave differently when installed on a flexible support or a specific foundation. Test conditions and any differences from the intended installation should be documented.

Test Setup and Acceptance Criteria

A clear test plan reduces the risk of an invalid test or an unexpected failure. Before testing begins, document the specimen, mass, dimensions, mounting method, fixture, instrumentation, required input, and operating conditions.

The test process generally includes the following steps:

1. Inspect the specimen: Record its initial condition, installed components, and mounting details.
2. Confirm the fixture: Check that the fixture and anchorage are appropriate for the required test and specimen.
3. Install sensors: Position accelerometers and other instruments according to the measurement plan.
4. Verify table performance: Confirm that the recorded motion meets the required input criteria.
5. Run the prescribed sequence: Apply the specified motion and monitor the equipment.
6. Complete inspections: Check for structural damage and verify required functions before and after testing, as specified.

Acceptance criteria depend on the equipment and procedure. They may include structural integrity, secure fasteners, acceptable deformation, electrical clearances, component retention, and continued operation of essential functions.

A test report should identify the applicable standard and edition, test configuration, measured input, observed response, deviations, and final assessment against the specified requirements.

Telcordia GR-63-CORE Testing With Biaxial Tables

Telcordia GR-63-CORE testing evaluates whether telecommunications equipment meets applicable NEBS physical protection requirements. Biaxial tables can support suitable seismic tests, but the laboratory must confirm that the required axes and test procedure are compatible with the system.

NEBS Seismic Zones 0 to 4

NEBS seismic zones represent different levels of seismic demand for equipment qualification. Zone 4 requires demanding seismic testing for relevant telecommunications equipment.

Identify the required zone from the applicable GR-63-CORE edition, customer specification, and intended deployment requirements. Laboratories should not select a zone based on the equipment’s size or general assumptions about the installation location.

For example, a tall telecommunications rack containing servers, power equipment, and cable-management assemblies may require testing in a specified seismic zone with its intended loading and anchorage. An empty rack test may not demonstrate the performance of the loaded configuration.

Before testing, confirm the zone, specimen loading, mounting arrangement, prescribed motion, and required functional checks. Also establish whether the customer’s specification includes additional requirements beyond the standard.

Required Response Spectrum and Test Duration

The seismic test procedure defines the required motion, including the applicable response spectrum, waveform or time-history requirements, and duration. These details must come from the governing procedure, not from a generic test description.

The required duration does not have to be the same for every test. It depends on the applicable edition, prescribed waveform, and test sequence. A laboratory should not change the duration or substitute a different input without confirming that the change is permitted.

During testing, table accelerometers record the motion delivered to the specimen. Additional sensors can help engineers understand how the rack or equipment responds. The recorded test response spectrum is then evaluated against the required spectrum according to the procedure.

This verification matters because a table’s programmed command alone does not prove the required motion was achieved. The actual measured input must be reviewed.

Structural and Functional Performance Criteria

Structural performance concerns whether the equipment remains physically secure. Functional performance concerns whether it continues to perform its required operations under the conditions defined by the test procedure.

A telecommunications rack might remain upright but still suffer loose mounting rails, damaged connectors, shifted equipment, or interrupted network service. The acceptance criteria should address the failures relevant to the product and its intended use.

The test plan should define:

• Acceptable structural damage or deformation.
• Requirements for rack anchorage and equipment retention.
• Which functions must be monitored during or after testing.
• Required checks for power, network connectivity, alarms, or other operations.
• Post-test inspections and reporting requirements.

Where equipment must remain operational during testing, the monitoring system and cables should be arranged safely so that they do not create hazards or distort the test results.

Equipment Suitable for Biaxial Seismic Testing

Biaxial shake tables can be used for many equipment assemblies that need to be assessed under horizontal earthquake motion. Suitability depends on the table’s operating envelope, specimen configuration, and applicable qualification requirements.

Electrical Cabinets and Enclosures

Electrical cabinets may contain relays, terminal blocks, control devices, and other components that need to remain secure during seismic motion. Testing can reveal weaknesses in the cabinet frame, door latches, mounting rails, fasteners, and internal supports.

The specimen should represent the intended application as closely as the test plan requires. Internal components and realistic loading can affect the centre of gravity and natural frequency, so these factors should be considered before the test begins.

Telecom Racks and Network Equipment

Telecommunications racks often hold servers, switches, power supplies, storage devices, and cable-management systems. Their seismic response depends on rack height, total mass, component placement, anchorage, and the stiffness of the supporting structure.

Testing should consider the complete configuration, not just the rack frame. Equipment retention, cable strain, mounting hardware, doors, and specified functional checks may all be important. If the system must operate during the test, its monitoring and shutdown arrangements should be defined in advance.

Substation Components and Control Equipment

Selected substation components and control cabinets may be suitable for biaxial testing where the applicable IEEE 693 qualification method permits it. The test setup should represent the relevant installation and operating conditions.

Some equipment may exceed the table’s payload or dimensions. Other components may require vertical excitation or specialised fixtures. Identifying these limitations early helps avoid unnecessary test delays and additional laboratory costs.

Setting Up a Cost-Effective Seismic Test Lab

A cost-effective seismic test lab meets qualification requirements reliably without paying for unnecessary capabilities. The best investment depends on the types of equipment the lab expects to test, the applicable standards, and future workload.

Biaxial Table Specifications to Check

Review the full performance envelope rather than a single headline number.

Ask the supplier to confirm performance for the expected payload. A system rated for a particular maximum mass may not achieve its maximum acceleration or displacement at that load.

For a laboratory primarily testing cabinets and telecom racks under suitable horizontal-motion procedures, a biaxial table or real-time hybrid testing setup may be a practical option. If future work will regularly require simultaneous vertical excitation, our servo-hydraulic services team can help you compare the long-term cost of a triaxial system or an upgrade path.

Sensors and Data Acquisition Requirements

Instrumentation records the motion applied to the specimen and its response. Base the measurement plan on the test objectives and required reporting, not simply on the number of available channels.

Common instruments include:

• Accelerometers: Record table input and equipment acceleration.
• Displacement sensors: Measure movement where required.
• Strain gauges: Measure strain in selected structural members.
• Force sensors: Record forces when needed for the test objective.
• Data acquisition systems: Collect and synchronise sensor signals.
• Functional monitoring equipment: Records selected equipment operations during testing.

Sensor range, mounting, calibration, sampling rate, and channel synchronisation all influence data quality. Each sensor should have a clear purpose, and the test report should explain how the recorded data was evaluated.

Fixtures, Anchorage, and Safety Systems

The fixture transfers the shake-table motion to the test article. A flexible or poorly designed fixture can change the specimen’s response and make the results difficult to interpret.

Check fixture stiffness, fasteners, anchorage, clearances, and specimen alignment. Tall racks and heavy cabinets may require lifting equipment, restraints, and a controlled installation process.

Safety planning is equally important. Appropriate emergency stops, access controls, operating procedures, exclusion zones, and protection against electrical or hydraulic hazards should be established before testing. Inspect the specimen and fixture for secure mounting before applying high-intensity motion.

How to Plan a Compliance Test

Start a compliance test with the evidence the customer or project requires. Once the standard, specimen, test input, and acceptance criteria are clear, the laboratory can determine whether its equipment is suitable.

Identify the Applicable Standard and Zone

Confirm whether the product must meet IEEE 693, Telcordia GR-63-CORE, or another specified requirement. Record the applicable edition and amendment (where relevant), seismic level or zone, required test method, and any additional customer requirements.

If the same product is intended for substation and telecommunications applications, compare the requirements separately. One test does not automatically establish compliance with both standards.

Resolve uncertainties with the responsible engineer or customer before booking the laboratory. This is far less expensive than discovering that the wrong test configuration was used.

Prepare the Equipment Configuration

Prepare a configuration sheet covering:

• Specimen dimensions, mass, and centre of gravity where available.
• Internal components and loading.
• Mounting brackets, anchorage, and fixture details.
• Required test axes and input motion.
• Sensor locations and data requirements.
• Operating state and functional monitoring.
• Acceptance criteria, safety measures, and test sequence.

Document differences between the test specimen and the production equipment. Missing brackets, incomplete loading, or incorrect mounting hardware can affect the result and may require additional testing.

Review Test Reports and Certification Evidence

A useful test report explains what was tested, how the test was performed, and whether the results met the specified requirements.

Review the report for the equipment identification, standard edition, specimen configuration, fixture and anchorage details, instrumentation, recorded motion, observations, functional checks, deviations, and conclusion.

Do not rely only on a statement such as “Zone 4 tested” or “IEEE 693 compliant.” Confirm the scope of the evidence, the tested configuration, and the exact requirements covered. Formal acceptance may also depend on customer review or other qualification procedures.

People Also Ask: Seismic Standards and Biaxial Shake Tables

What is IEEE 693 seismic qualification?

IEEE 693 seismic qualification evaluates whether applicable substation equipment meets specified seismic performance requirements. Depending on the equipment and qualification method, the evidence may involve physical testing, engineering analysis, or an approved combination.

What is Telcordia GR-63-CORE testing?

Telcordia GR-63-CORE testing evaluates telecommunications equipment against applicable NEBS physical protection requirements. Seismic evaluation can include checks of equipment frames, anchorage, component retention, and required functionality.

What is the difference between IEEE 693 and Telcordia GR-63-CORE?

IEEE 693 focuses on seismic design and qualification for substations and electrical equipment. GR-63-CORE addresses physical and environmental protection requirements for telecommunications equipment and network facilities.

What is a biaxial shake table?

A biaxial shake table applies controlled motion along two perpendicular axes, usually horizontal directions. It is used to evaluate how equipment responds to specified earthquake-like movement.

Can a biaxial shake table perform Telcordia GR-63-CORE testing?

It may be suitable for a GR-63-CORE seismic test if the table meets the required motion, payload, and other test conditions. The laboratory must confirm the required axes and test procedure before selecting the system.

Does IEEE 693 require triaxial shake table testing?

The required axes depend on the applicable edition, equipment category, and qualification method. Engineers should check the relevant provisions and project specifications rather than assume all tests require biaxial or triaxial input.

What is NEBS Zone 4 seismic testing?

NEBS Zone 4 testing evaluates equipment against the applicable high-seismic-demand requirements for telecommunications installations. The precise input and acceptance criteria must be taken from the relevant GR-63-CORE edition and customer specification.

What is a required response spectrum in seismic testing?

A required response spectrum (RRS) defines the target response across a range of frequencies for the seismic test. It helps engineers determine whether the applied motion represents the specified seismic demand.

What is the difference between RRS and TRS?

RRS stands for Required Response Spectrum, the target specified for the test. TRS stands for Test Response Spectrum, calculated from the recorded test motion; comparing it to the RRS helps determine whether the input met the prescribed spectrum requirements.

What equipment needs IEEE 693 qualification?

Relevant substation equipment may include control cabinets, instrument transformers, switchgear, disconnect switches, and other electrical apparatus. The actual requirement depends on the equipment and project specification.

What equipment needs Telcordia GR-63-CORE testing?

Telecommunications equipment subject to applicable NEBS requirements may need GR-63-CORE evaluation. Examples include racks, cabinets, servers, switches, and related assemblies.

How long does a Telcordia GR-63-CORE seismic test take?

No single duration applies to every qualification test. The required sequence and duration depend on the applicable edition and approved test procedure.

What are the acceptance criteria for Telcordia seismic testing?

Criteria may address structural integrity, rack anchorage, equipment retention, deformation, damage, and specified functions. The test plan should define the applicable pass/fail requirements before testing begins.

Can a biaxial table test both horizontal directions?

Yes. A biaxial table can apply motion along two perpendicular axes. Whether the required test uses simultaneous or sequential excitation depends on the governing procedure.

Is vertical testing required for GR-63-CORE?

The required axes must be confirmed from the applicable edition and test procedure. Do not assume vertical input is always required or always unnecessary when selecting a biaxial table.

What is the difference between structural and functional seismic performance?

Structural performance concerns physical stability, integrity, and secure mounting. Functional performance concerns whether the equipment continues to operate as required under the specified test conditions.

How much does biaxial shake table testing cost?

Cost depends on specimen size, payload, fixture design, required motion, instrumentation, test duration, engineering support, and reporting. A detailed test specification helps laboratories provide comparable quotations.

What sensors are used in seismic qualification testing?

Accelerometers are commonly used to measure table input and equipment response. Depending on the test objectives, laboratories may also use displacement sensors, strain gauges, force sensors, and functional monitoring systems.

What is the frequency range for Telcordia seismic testing?

The required frequency range depends on the applicable GR-63-CORE edition and prescribed test procedure. Confirm the specified range, and verify that the shake table can reproduce the required motion at the specimen’s actual mass.

Conclusion

IEEE 693 and Telcordia GR-63-CORE serve different industries, but both require a clear test scope and reliable evidence of seismic performance. A biaxial shake table can be a cost-effective choice for suitable horizontal-motion tests on cabinets, racks, control panels, and selected electrical equipment. Where vertical excitation or combined three-axis input is required, a biaxial system may not be sufficient.

Before requesting a quotation, prepare a one-page test requirement document that identifies the applicable standard and edition, seismic level or zone, equipment configuration, required axes, response spectrum, frequency range, payload, instrumentation, acceptance criteria, and reporting requirements. This gives the laboratory the information needed to assess its capabilities and price the work accurately.

The most economical solution is not necessarily the table with the lowest purchase price. It is the system that can reproduce the required motion, accommodate the intended specimen, support safe testing, and produce credible evidence for the qualification being requested.

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