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Summary

For wood floor systems, their vibration performance is significantly dependent on the conditions of their supports, specifically the rigidity of the support. Detrimental effects could result if the floor supports do not have sufficient rigidity. This is special ture for floor supporting beams. The problem of vibrating floor due to flexible supporting beams can be solved through proper design of the supporting beams. However, there is currently no criterion set for the minimum requirement for floor supporting beam stiffness to ensure the beam is rigid enough. Designers’ current practice is to use the uniform load deflection criteria specified in the code for designing the supporting beams. This criterion is based on certain ratios of the floor span (e.g. L/360, L/480 etc.). The disadvantage of this approach is that it allows larger deflections for longer-span beams than for shorter beams. This means that engineers have to use their experience and judgement to select a proper ratio, particularly for the long-span beams. Therefore, a better vibration-controlled design criterion for supporting beams is needed. This study was conducted with the objective of proposing a minimum requirement for floor supporting beam stiffness to ensure that the floor supporting beam is sufficiently rigid to avoid any detrimental effect on floor vibrations induced by normal walking of occupants. To meet the objective, the following steps were undertaken: • Establish a database of performance of supporting beams in the field, including their bending stiffnesses; • Conduct laboratory study to develop the stiffness criterion for supporting beams; • Derive the supporting beam minimum stiffness criterion using the laboratory data; and • Verify the criterion using the field supporting beam database. A stiffness criterion for supporting beams was developed and verified using field supporting beam database. It was found that the proposed criterion predicted well the field supporting beam performance. Three design examples were provided to demonstrate the application of the proposed beam stiffness criterion. Based on the results obtained in this study, the proposed criterion is simple and rational for designing floor supporting beams that would provide adequate stiffness to control vibrations of floor systems. It is recommended to further verify the ruggedness of the proposed stiffness criterion for floor supporting beams using new field supporting beam data whenever they become available.

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