"Buildability" is a concept that refers to the ease of constructing a building that meets end-user needs; as such, it is a measure of the desirability and value of a building. Building "serviceability" is a measure of the ability of a building to serve its intended and normal use and occupancy. It is clear that buildability and serviceability of wood-framed buildings, like other building performance attributes, significantly affect the competitiveness of wood-framed construction. A thorough study of the buildability and serviceability of wood-framed buildings needs multidisciplinary efforts. However, as a pioneer study, this project focuses on the major buildability and serviceability issues in wood-framed floor construction. The issues include the lack of a design method to control vibrations in a broad range of wood-based floors in codes, the lack of a rational method to determining bending and shear stiffness of wood parallel-chord metal-plate connected trusses, the need of a design method for bridging and blocking and the need of system approaches for resolving the conflicting construction solutions such as using concrete topping and/or continuous sub-floor and joists.
This project was designed to cover a three-year period to address these issues. Four tasks were identified:
Task-1 proposing a new design method to control vibration in wood-based floors to code committee;
Task-2 recommendations for a method to determine bending and shear stiffness of wood parallel – chord metal-plate connected trusses;
Task-3: development of design method and design values for various bridging and blocking systems;
Task-4: establishment of a knowledge base on the effects of various construction practices on the serviceability, structural reliance, fire resistance, and sound-transmission performance of wood-framed floors.
In the first two years, Tasks 1- 3 were completed. A new design method to control vibrations in wood-based floors was presented to CSA 086 General Design Sub-Committee. A method to determine true bending and shear stiffness of wood parallel – chord metal-plate connected trusses was proposed based on ASTM D198 method to determine shear and true MOE of wood. An approach to account for the stiffness contribution of bridging/blocking was developed. Test results show that the approach is reasonably accurate even if it is on conservative side and the test method to determine bridging/blocking properties is easy and economical to implement. A study of the impact of the new floor design method on current floor spans was conducted by the wood industry. The results of the impact study have revealed that the new design method is on right track, however, some adjustment may be needed. To make the adjustment with a minimum negative impact to the wood industry, an industry survey of the most common product types, spans and floor construction practises in the marketplace was conducted. The survey results have shown that the constructions of the floors using 9-1/2 inches joists at 16 inches spacing, spanned from 12 to 16.6 feet, or 11-7/8 inches joists at 16 inches spacing, spanned from 15 to 20 feet are the most popular floor systems.
To complete this project in the coming year, the effort will be spent on Task-4 and on the finalization of the design method.