ISO 6897:1984

Overview

ISO 6897:1984 provides guidelines for evaluating the human response to low-frequency horizontal motion (0.063 to 1 Hz) of fixed structures - primarily buildings and seabed-founded off‑shore platforms. The standard focuses on whole‑body perception and subjective response (alarm, intrusion, interference with tasks) rather than structural damage or injury. It gives recommended r.m.s. acceleration magnitudes for use in assessing occupant response to wind‑ or wave‑induced motion, with specific guidance for storm events (notably 10‑minute peak intervals and a 5‑year return period reference).

Key topics and technical requirements

• Scope and exclusions
  • Applies to human perception of horizontal motion in standing, sitting or reclining postures.
  • Excludes injury effects, blasting/earthquake events and floating platforms (tension‑leg, articulated).
• Frequency band
  • Targets 0.063–1 Hz (very low‑frequency horizontal motion).
• Human response categories
  • Basic threshold effects, alarm/intrusion (adverse comment), and interference with activities.
  • Acceptance criteria tied to percent of occupants likely to comment (e.g., ~2% adverse comment in buildings for a 5‑year storm peak).
• Measurement and analysis
  • Measure r.m.s. horizontal acceleration at the structural surface that transmits motion to occupants.
  • Analyze continuous records for discrete frequency components; use one‑third octave bands and vector addition of orthogonal components (accounting for phase).
  • For low frequencies, long averaging times are required (examples: >200 s for good confidence at ~0.08 Hz).
  • Filtering: vibration outside 0.063–1 Hz should be filtered (recommended slope ≥24 dB/octave).
  • Recommended instrumentation includes calibrated accelerometers, matched amplifiers and spectral analysis (FFT or equivalent).
• Assessment guidance
  • Annex provides perception threshold curves (referred to as curve 1 and curve 2) for satisfactory r.m.s. acceleration magnitudes: general-purpose buildings and precision/critical tasks or trained offshore personnel respectively.
  • Short‑duration events (<10 min) and rare storms need special consideration; adverse comment levels depend on return period and exposure duration.

Applications and users

• Structural and wind‑engineering consultants assessing human acceptability of building or off‑shore platform motion.
• Architects and building designers evaluating occupant comfort in tall or flexible structures.
• Offshore engineers planning seabed‑founded installations where crew performance and comfort matter.
• Human factors specialists, vibration measurement contractors, and standards/compliance teams validating vibration mitigation or operational criteria.

Related standards

• ISO 2631 (evaluation of human exposure to whole‑body vibration) - referenced for frequencies above 1 Hz and complementary guidance.
• Developed under ISO/TC 108 (Mechanical vibration and shock).

Keywords: ISO 6897:1984, low‑frequency horizontal motion, building vibration, offshore structures, human response, whole‑body vibration, 0.063–1 Hz, r.m.s. acceleration, vibration measurement.