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ISO/TR 25741-1:2025 — Lifts and Escalators Subject to Seismic Conditions: Part 1 — Rule by Rule Comparison
A detailed comparison of seismic design requirements for lifts and escalators across EU, US, Canadian, Australian, New Zealand, and Japanese codes
1. Scope and Purpose of ISO/TR 25741-1:2025
ISO/TR 25741-1:2025 provides a comprehensive rule-by-rule comparison of seismic design requirements for lifts (elevators), escalators, and moving walks across six major international codes and standards. This Technical Report, prepared by ISO/TC 178, compares the EN 81-77:2018 (European), ASME A17.1/CSA B44 (North American), AS 1735 (Australian), NZS 4332/NZS 1170.5 (New Zealand), and Japanese Building Code requirements side by side, identifying areas of convergence and divergence in seismic design philosophy, load application methods, and acceptance criteria.
This first edition of ISO/TR 25741-1:2025 cancels and replaces ISO/TR 25741:2008, incorporating significant technical revisions reflecting advances in seismic engineering knowledge and lessons learned from major earthquakes over the intervening period. The report covers two primary categories: elevators and lifts (Section 4.2) and escalators and moving walks (Section 4.3), with the comparison structured against the clause numbering of EN 81-77:2018 (EU) and EN 115-1:2017 Annex M as the reference framework.
| Region / Code | Seismic Standard | Scope | Key Design Parameters | Special Features |
|---|---|---|---|---|
| Europe (EU) | EN 81-77:2018 | Lifts subject to seismic conditions | Seismic acceleration ah,v, response spectra | Harmonized with Eurocode 8 |
| USA / Canada | ASME A17.1/CSA B44 Ch. 8.4 | Elevator seismic requirements | Seismic force Fp, component factor | Risk category based on building use |
| Australia | AS 1735.1, AS 1735.5 | Lifts and escalators seismic | Earthquake load combinations | Referenced to AS 1170.4 |
| New Zealand | NZS 4332, NZS 1170.5 | Elevator installations | Seismic coefficient Cp(Z) | High seismic zone specific |
| Japan | BSLJ / GFS:2016 | Building standard law | Seismic intensity K, shear coefficient | Performance-based design |
One of the most significant divergences identified in the report is the treatment of seismic acceleration. EN 81-77 applies a seismic acceleration that varies with building height and soil type, while ASME A17.1 uses a component amplification factor approach. Engineers working on international projects must understand these differences to ensure compliant design in each jurisdiction.
2. Key Technical Differences and Design Implications
The report’s detailed clause-by-clause comparison reveals several critical differences in how each code addresses seismic protection of lifts. One fundamental divergence is the seismic load combination approach: EN 81-77 applies seismic loads in combination with 30% of the rated load and guide rail forces, while the Japanese code requires full rated load combined with seismic forces at a specified seismic intensity.These differences can result in up to 40% variation in required guide rail section modulus between jurisdictions.
Another significant difference is in the treatment of counterweight retention. All codes require counterweight guardrails or barriers to prevent derailment during seismic events, but the design load for these barriers varies considerably: EN 81-77 requires a horizontal force of 5% of the counterweight mass applied at the centre of gravity, while ASME A17.1 requires 10% of the counterweight mass. The Japanese code takes a more analytical approach based on the response acceleration at the specific installation height within the building.
A critical finding from the comparison is that seismic requirements for escalators are significantly less developed than those for lifts in most codes. Only EN 115-1 Annex M and the Japanese Building Code provide comprehensive escalator seismic requirements. Engineers specifying escalators in seismic zones outside Europe and Japan must carefully evaluate which national provisions apply and whether additional engineering analysis is warranted.
3. Engineering Insights for Seismic Resilient Lift Design
From an engineering design perspective, the Technical Report highlights that the most cost-effective seismic protection measures for lifts are those integrated at the building design stage rather than retrofitted later. Key design decisions affecting seismic performance include: the location of the machine room (overhead versus basement-mounted drives), the configuration of guide rail brackets (continuous fishplate connections versus intermittent bracket support), and the selection of compensation rope systems (tensioned versus compensated sheave arrangements).
The report also draws attention to the critical role of seismic switches or seismic detection devices. EN 81-77 requires seismic detection devices that automatically bring the lift to a stop at the nearest landing and open the doors when a predetermined acceleration threshold is exceeded. The threshold levels and required response actions differ across codes, with implications for lift operational reliability and post-earthquake functionality. ASME A17.1 requires seismic switches set at 0.15 g for automatic shutdown, while the Japanese code specifies a more graduated response based on earthquake early warning system inputs.
Following the 2011 Christchurch earthquake in New Zealand, lifts retrofitted with seismic protection measures based on NZS 4332 demonstrated significantly better performance than non-retrofitted installations. A post-event survey revealed that 85% of retrofitted lifts remained operational or required only minor repairs, compared to only 30% of non-retrofitted lifts. The key differentiators were the presence of seismic switches, adequately designed guide rail brackets, and counterweight guardrails.
Frequently Asked Questions
Which seismic standard should I use for a lift installation in a country with no national seismic lift code?
A: ISO/TR 25741-1 recommends adopting the EN 81-77 framework as a baseline reference in the absence of a national code, while adjusting the seismic acceleration parameters to reflect local seismicity data from national building codes. The report’s comparative analysis can help identify which code provisions are most appropriate for the specific seismic zone and building type.
A: ISO/TR 25741-1 recommends adopting the EN 81-77 framework as a baseline reference in the absence of a national code, while adjusting the seismic acceleration parameters to reflect local seismicity data from national building codes. The report’s comparative analysis can help identify which code provisions are most appropriate for the specific seismic zone and building type.
How do seismic requirements differ for machine-room-less (MRL) lifts compared to traditional lifts?
A: MRL lifts present unique seismic challenges because the drive components are located within the hoistway, making them vulnerable to seismic-induced displacement and potential impact with hoistway walls. The report notes that MRL lifts require special attention to controller cabinet seismic anchorage, drive sheave positioning, and emergency battery backup for evacuation functionality.
A: MRL lifts present unique seismic challenges because the drive components are located within the hoistway, making them vulnerable to seismic-induced displacement and potential impact with hoistway walls. The report notes that MRL lifts require special attention to controller cabinet seismic anchorage, drive sheave positioning, and emergency battery backup for evacuation functionality.
What is the most important seismic protection measure for escalators?
A: The most critical measure is preventing escalator truss dislodgement from its supporting structure. This requires adequate anchorage at both ends, with the connection design capable of resisting the full seismic demand. Additionally, the gap between the escalator and building structure must accommodate the maximum inter-story drift without causing structural interference.
A: The most critical measure is preventing escalator truss dislodgement from its supporting structure. This requires adequate anchorage at both ends, with the connection design capable of resisting the full seismic demand. Additionally, the gap between the escalator and building structure must accommodate the maximum inter-story drift without causing structural interference.
The report's findings have direct implications for lift manufacturers exporting equipment to multiple countries. A lift designed to EN 81-77 requirements may require significant modification to comply with Japanese seismic codes, and vice versa. Understanding these differences at the design stage rather than during the certification process can save substantial time and cost in product development and market access.
