Project or owner requirement
Document compliance of equipment, a structure or a system with defined seismic criteria.
Seismic · Dynamics · Anchorage
Seismic qualification of structures and equipment.
From global seismic demand to the critical anchorage detail — response spectra, modes, amplification, supports and interfaces.
The required outcome: a traceable qualification from demand through supports and anchorage.
The required outcome is a traceable qualification from the applicable demand through supports and anchorage. Mass, inertia and load-path calculations come before modal, response-spectrum or time-history models used only to the necessary level.
When to qualify
When continuity of the load path must be demonstrated.
Useful seismic qualification does not stop at the spectrum or the global model. It follows the forces through supports, baseplates, bolts and anchors that make the response possible.
Equipment installed above grade
Account for amplification associated with the building, floor elevation and actual support flexibility.
Post-earthquake function required
Assess stability, required continued function and the mechanisms that could interrupt service.
Modification or relocation
Revisit demand, modes, centre of gravity and interfaces after a configuration change.
Supports or anchors not demonstrated
Connect global reactions to plates, bolts, welds, anchors and the existing supporting structure.
Non-trivial dynamic response
Address multiple modes, local amplification, torsion or interactions that simple static forces do not represent.
Qualification chain
From seismic demand to the detail that governs.
Each link must be consistent with the previous one. An anchor reaction is defensible only when the demand, dynamic model and load path are also defensible.
- 01
Seismic demand
Project criteria, applicable spectrum, directions, damping and required performance level.
- 02
Response at the installation point
Specified spectrum, floor demand or transfer from the building model when required.
- 03
Equipment response
Mass, stiffness, modes, modal participation, amplification and directional combinations.
- 04
Force distribution
Frame, panels, components, supports, welds, bolts and reactions at the interfaces.
- 05
Anchorage and support
Shear, uplift, baseplate, anchor group, concrete or supporting steel.
Anchorage is part of the system
Qualification is complete only when the forces have a real path.
Global equipment behaviour can shift demand from one support to another. Baseplates, interfaces and anchorage should therefore be checked using reactions from the same qualification model.
- Demand and damping consistent with project criteria.
- Modes and participating mass verified in the relevant directions.
- Modal and directional combinations documented.
- Reactions extracted at the actual support interfaces.
- Uplift, shear, contact, anchor-group action and local support checked according to the real mechanism.
Capabilities
The right level of analysis for the demand and risk.
Scope can range from a focused anchorage check to complete dynamic qualification of the equipment and its supports.
Modal analysis
Frequencies, mode shapes, participating mass, torsion and sensitivity to support stiffness.
Response spectra
Spectral response, modal combination, orthogonal directions and enveloped reactions.
Floor demand
Use of a supplied floor spectrum or demand transfer from a global building model when the assignment requires it.
Time-history response
Transient analysis when criteria, nonlinear behaviour or the nature of the demand justify it.
Structures and equipment
Frames, skids, tanks, cabinets, supports, enclosures and mechanical or electrical assemblies.
Supports and baseplates
Local stiffness, reaction distribution, contact, uplift, welds and bolts.
Anchorage
Shear, tension, interaction, anchor-group action, edge conditions and transfer into the support.
Local FEA details
Focused analysis of critical regions, interfaces or nonlinear behaviour governing qualification.
Approach
Traceable qualification from criterion to conclusion.
Each step is defined to prevent gaps between imposed demand, calculated response and demonstrated capacity.
Confirm the criteria
Identify the spectrum, location, directions, damping, performance category and documentation requirements.
Establish the configuration
Gather geometry, masses, centre of gravity, interfaces, materials, supports and installation conditions.
Build and verify the model
Represent useful stiffness and verify modes, participating mass, equilibrium and sensitivity to assumptions.
Calculate the response
Apply demand, combine modes and directions, extract forces and identify governing mechanisms.
Check critical details
Assess members, panels, supports, welds, bolts, baseplates, anchors and the local support.
Conclude and recommend
Document margins, limitations, required modifications and information to preserve for installation or approval.
Useful starting information
Start with what exists, then identify what is truly missing.
An initial review quickly confirms whether the demand and configuration are sufficiently defined to begin qualification.
Drawings and model
Geometry, assembly, supports, interfaces and installation details.
Mass and centre of gravity
Total mass, distribution, internal components and operating conditions.
Seismic criteria
Spectrum, location, elevation, damping and client or project requirements.
Materials and connections
Properties, welds, bolts, plates, anchors and existing support.
Required function
Stability only, integrity, continued operation or other performance criteria.
Equipment condition
New, existing, modified or relocated, with photographs and field measurements where relevant.
Deliverables
Qualification that supports design, installation and approval.
The format is matched to the assignment, but the conclusion remains traceable to the criteria and assumptions used.
Qualification basis
Criteria, spectra, configuration, masses, materials, interfaces, assumptions and limitations clearly documented.
Results and reactions
Modes, participating mass, enveloped demands, support reactions and checks of critical elements.
Conclusion and modifications
Qualification status, margins, strengthening, anchorage or support changes, and installation recommendations.
Frequently asked questions
What to clarify before qualification begins.
The qualification path depends on the applicable criteria, required function and available information about the equipment and installation.
Is shake-table testing always required?
No. Analytical qualification may be appropriate depending on the project criteria, configuration and phenomena that must be demonstrated. Some equipment or specifications may require testing, so the qualification path should be confirmed at the outset.
Can existing equipment be qualified?
Yes, when its configuration, condition, masses, connections and installation can be established with sufficient confidence. Field measurements and inspection may be part of the assignment.
What if a floor response spectrum is unavailable?
The first step is to identify an acceptable demand source for the project. Depending on the context, a specified spectrum, code-based demand or building analysis may be required.
Is anchorage included?
It can be, and should be tied to reactions from the same model when anchor capacity is part of the demonstration. Scope can then include baseplates, bolts, anchors and the local support as required.
Start simply
Equipment, a spectrum or anchorage to qualify?
Send the available drawings, masses, seismic criteria and installation information. An initial review will quickly confirm the most useful approach.