Abstract
Wood truss joist floors are increasingly used to replace traditional solid timber joist floors in low-rise timber houses. An understanding of the vibration performance of wood truss joist floors is critical for the design and serviceability of the floors. It is difficult to model wood truss joist floors accurately because of the complicated boundary conditions and numerous sophisticated flexible connections. This paper discusses three simplified modeling methods for the wood truss joist floor system. The modeling results were validated by a series of static deflection tests and vibration modes and frequencies tests of a full-size floor. And predictive analysis of human-induced vibration of the floor was also conducted. The vibration characteristics of the wood truss joist floor were investigated. The examination of the applicability of these modeling methods was provided. The results indicate that the point loading deflection more easily affects the deflection of the adjacent joist. However, the deflection influence on other joists that are three spaces away is minimal. Walking on the wood truss joist floor produces steep vibration acceleration fluctuations at the floor center for a relatively long time period. The sheathing-to-joist connections and the metal plate connections of the joists have significant influences on the vibration response of the wood truss joist floor. The modeling method, which considers the flexible metal plate connections and flexible sheathing-to-joist connections, performs best for predicting the vibration performance of the floor.
Highlights
Lightweight joist wooden floors are widely used in residential and low-rise commercial buildings and include solid lumber joist floors, wood I-joist floors, and wood truss joist floors, as shown in Figure 1. e timber floor systems consist of several parallel joist members supporting the wood flooring or sheathing, which is connected to the joists in a semirigid manner
Glisovic and Stevanovic [23] developed the numerical models of the solid lumber joist floor system to investigate the parameter effect on the vibration performances
A person sitting on a movable wood frame moved from one side to the other side of the floor and used an instrumented ICP hammer to hammer the floor and created impact excitation. e distribution of the excitation points was displayed in the DASP-V10 Software on the computer screen. e vertical vibration movements of the measured points were transformed into electrical signals and continually recorded by the data acquisition, and the electrical signals were processed based on fast Fourier transform (FFT) to obtain the frequency response function (FRF). e modal frequencies, shapes, and damping ratios of the tested wood truss joist floor were extracted from the FRF
Summary
Lightweight joist wooden floors are widely used in residential and low-rise commercial buildings and include solid lumber joist floors, wood I-joist floors (stiffening ribs), and wood truss joist floors, as shown in Figure 1. e timber floor systems consist of several parallel joist members supporting the wood flooring or sheathing, which is connected to the joists in a semirigid manner. Ohlsson [4] investigated the vibration performance of wood I-joist floors and proposed design criteria by limiting the fundamental frequency to values exceeding 8 Hz, the point load deflection to 1.5 mm, and the impulse velocity response to100[f(1)ξ−1]. Glisovic and Stevanovic [23] developed the numerical models of the solid lumber joist floor system to investigate the parameter effect on the vibration performances (joist spacing, depth, sheathing thickness, nail spacing, bridging, and support condition). Three modeling methods of the wood truss joist floor were developed and the numerical modeling results were verified with a series of static test results, vibration frequencies, and modes of a full-size floor. Dimensional lumbers of spruce-pine-fir (SPF) (38 mm × 89 mm) used for the flange and web members compose the herringbone truss joist with an overall joist depth of 440 mm, illustrated in Figure 4. e mean elastic modulus parallel to the grain EL for dimensional lumbers chords had been determined as 8700 N/mm, with the elastic modulus for the radial direction ER of 600 N/mm and for the chord direction ET of 400 N/mm2. e mean density of dimensional lumbers, ρ, was determined as 560 kg/m3. e flange and web members were connected with metal plates produced by MiTek Ltd. e metal plates were made using thin steel plates of 1 mm thickness with zinc coat and teeth of 8.4 mm height. e mean yield strength of the metal plates has been measured as 271.95 MPa, and the tension strength has been measured as 341.32 MPa. e mean elastic modulus of the steel plate is assessed as 203 GPa
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