Keywords: wood floors, I-joists, sawn lumber, vibrations, OpenSees, finite element analysis, spreadsheet.

Engineered wood floor systems have provided engineers with a method to span greater distances with significantly less raw material than standard sawn lumber, providing increased economic efficiency. However, longer spans with lighter floors have made engineered wood floors susceptible to undesirable levels of vibrations resulting from human activities. Presently, in the U.S. there are two design methods to limit the vibrations of the wood floors. The first method relies on the current National Design Standards (NDS), and the other is to perform a detailed static and dynamic response of the floor system. If an engineer chooses to use the NDS standards, the design will be based on estimating the static deflection under uniform loads. NDS has developed minimum thicknesses in an attempt to minimize the floor vibrations. While the NDS standards provide an efficient method for designing wood floors, the approach is over-simplified. Engineers who choose to design floors using detailed static and dynamic analyses may develop an overall improved design, albeit at the cost of a more complicated and time consuming approach. This paper presents a computer analysis method that considers realistic floor behaviour without the complexity associated with finite element modelling.

To validate the analysis approach, it was first necessary to perform experiments on a floor system constructed and tested in a controlled environment. These tests were developed in order to estimate the floor system vibration characteristics and simulate responses under human activities.

The floor was then modelled using a finite element (FE) package called OpenSees. This FE package was selected because it is an open source and it utilizes a scripting language. These properties make it easier to create a generic floor model that can be altered to fit a specific project. In order to select the appropriate elements to fit this FE model, several verifications were conducted. It was determined that shell, beam-column, and zero-length elements were most effective in modelling the plywood sheathing, joists, and nail connections, respectively. The user of the OpenSees script inputs various geometrical and engineering properties using an ExcelR interface. OpenSees will then simulate the static and dynamic responses of the system. During the simulation, OpenSees records the floor's displacement, velocity, and acceleration at the centre of the floor and outputs these responses to the ExcelR interface.

Adequacy of the floor system is based upon several serviceability limit states that have been commonly used by engineers performing detailed dynamic analyses of floor systems. These limit states include floor behaviour such as maximum static deflection, natural frequency, and maximum acceleration of the system. All the acceptability thresholds have been included in the proposed dynamic analysis approach.

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