SERVICEABILITY SENSITIVITY ANALYSIS OF WOOD FLOORS ALLOWING FOR SHEATHING DISCONTINUITIES
Keywords:
sensitivity analysis, wood floors, engineered joists, vibrations, OpenSees, finite element analysis, spreadsheet.Abstract
This paper compares several design criteria for preventing unacceptable wood floor vibrations under occupant-induced loads and presents a sensitivity analysis based on static and dynamic responses of wood floor with engineered I-joist. Responses of floors with continuous and discontinuous (jointed) sheathing are compared. To accomplish this task, a user interface for the OpenSees finite element analysis program was developed. The interface was created in Microsoft Excel and allows user input for various floor system properties which are used as input into OpenSees. Results from the OpenSees program are imported into the user interface and compared against multiple acceptance criteria which have been established by researchers to determine fitness of the floor system. It was determined that a system with a 1.92 kPa (40 psf) uniform load modeled with one continuous piece of sheathing covering the entire floor system produced deflections which averaged 32 percent to a maximum of 45 percent lower than a floor system modeled with jointed sheathing. For a 1 kN (225 lb) force applied at the center of the floor, floors with jointed sheathing had an average of 12 percent and a maximum of 15 percent larger displacements compared to the floors with continuous sheathing. Floors with jointed sheathing had an average of 8 percent and a maximum of 12 percent lower unoccupied natural frequencies compared to the floors with continuous sheathing. Floors with jointed sheathing had an average of 10 percent and a maximum of 13 percent lower occupied natural frequencies compared to the floors with continuous sheathing. Floors with jointed sheathing also had an average of 17 percent and a maximum of 38 percent larger frequency-weighted one-second root-mean-square acceleration values compared to the floors with continuous sheathing. The results show that great care must be taken when simplifying the sheathing setup on a floor model since the results create the illusion of better serviceability performance than actual installed floors will achieve.
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