| Lightweight wood floors for residential and light industrial applications have been known at times to exhibit annoying levels of vibration even under normal occupancy loading. This unsatisfactory performance is mainly attributed to the availability and the use of higher strength materials of reduced weight and size. Most existing design methods dealing with this serviceability problem have been developed primarily with respect to the dynamic characteristics of the floor. Available experimental data, however, suggest alternative design methods which recognize the behavioural characteristics of the floor with its occupants as a coupled problem.; This study presents a numeric tool for analyzing the frequencies, and the dynamic response of a light wood floor system under occupants' footfall loadings. In particular, the occupant's interaction with the floor is found to be sufficiently modelled by a measured forcing function applied in conjunction with a human oscillator. The time and positional characteristics of the footstep forces from occupants' activities are also accounted for. Principally, the modal synthesis analysis techniques are used to assemble the mass and stiffness matrices of the floor system, and are able to account for the various complexities common to wood floor construction: orthotropic plate cover, semi-rigid subfloor-joist connections, joists' end supports rigidity, joist bridging, and gaps in subfloor sheathing. Since analytical mode shapes are used to express the floor system's displacement fields, the size of each of the system's dynamic parameters (mass, stiffness, and damping) is correspondingly reduced which makes this method even adaptable to microcomputers. A comparison with existing experimental results confirms the adequacy of this numerical tool.; The rationale behind this study is towards a provision of a realistic tool for evaluating a lightweight floor system's dynamic response under occupancy-induced loading, which is a necessary step in the development of vibrational-based serviceability design criteria. Using the tool developed for this thesis, a new vibration serviceability design guideline for lightweight wood floors of short to medium span has been developed which is not only cost effective, but also requires simple input parameters of the floor which are readily available to the designer at the design stage. A more achievable feature of the proposed model is its uniqueness in accounting simultaneously for both the essential features of the occupant-induced forces and those of the floor in a simplistic manner. |
