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Manufacturing plants that produce micro-electronic components, and facilities for extremeprecision experimental measurements have strict vertical vibration serviceability requirements due to sub-micron feature size or optical/target dimensions. Failure to meet these criteria may result in extremely costly loss of production or failure of experiments. For such facilities floors are massive but stiff, generally have first mode natural frequencies above 10Hz and are typically classed as 'high frequency floors'. The process of design to limit in-service vibrations to within specific or generic vibration criteria is termed 'vibration control'.Several guidance documents for vibration control of high frequency floors have been published, for different applications. These design guides typically propose simplifications of complex floor systems and use of empirical predictive design formulae. A recently published guide uses a more rigorous approach based on first-principle modal analysis and modeling footfalls as effective impulses, but there remain unresolved issues about its application, and this paper addresses these in order to develop an improved methodology.First, the significant but conventionally discounted contribution of resonance well above the conventionally accepted boundary between low and high frequency floors is examined. The level of necessary modeling detail is then considered along with the effect of accounting for adjacent bays in simulation of a regular multi-bay floors. Finally, while it is assumed that contributions of higher modes to impulsive response decrease so that a cut-off frequency can be prescribed, simulations demonstrate that with both effective impulse and real footfall forces, there is not necessarily asymptotic response with rising floor mode frequency.The conclusion is that there are no shortcuts to predicting response of high frequency floors to footfall excitation. Simulations must consider resonant response due to high order harmonics, provide adequate detail in finite element models and adopt a cutoff frequency that depends more on usage than on features of the floor or of the walking.

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Experimental and analytical modal analysis and in-operation vibration measurements were performed on the massive concrete structural floors of several structurally connected 'units' of a six-level, multi-tenant industrial complex with total floor usable area exceeding 0.1km 2. The aim of the systematic study was to characterise vibration sources and factors that affect vibration serviceability, which is a major concern when changing usage patterns lead to conflicting requirements for vibration generation and tolerance for different types of industrial/commercial user. This was a rare investigation aiming to provide information on specific performance and relevant technologies for occupancy decisions by tenants and building management of similar structures. Floors evaluated were within different types of industrial single-occupant unit stacked up to six levels and having multi-bay floors with spans up to 12m with first vibration mode frequencies greater than 8Hz. These 'high frequency floors' display typical transient response behaviour to footfalls, with response levels controlled by modal mass. Units were studied in typical operational conditions including warehousing, instrument assembly and testing, light electronic/mechanical manufacturing and machining. Vibration sources included internal and external vehicles, human footfalls and machinery. The study showed the most onerous form of loading to be forklift trucks and that higher level floors of the same type were least serviceable. Experimental modal analysis showed a surprising range of modal properties for nominally identical floors of the same type and the relevance to performance of modal mass.

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