Development of A Ready-To-Assemble Construction System
Platt, Robert Terry
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To accommodate an expanding global population, a renewable raw material resource base, in conjunction with new building technologies, must be applied to the residential housing sector. Desirable characteristics of housing systems are economy, safety, environmental sustainability, durability, design flexibility and a long service life. The system should be acceptable to the end-user, consist of renewable, indigenous resources, and require a minimum investment in labor and equipment for both production and erection. The objective of this research was to develop a ready-to-assemble (RTA) framing system. Integral to the framing system is a nail plate connector, developed in this project, that laminates wood or wood composite elements into larger building components. The laminated components can be bolted together to form various structural configurations. Decisions on the development of the RTA system were structured according to an Innovation Development Decision Model (IDDP) that was constructed from previous adoption and diffusion research. The IDDP model elucidates and illustrates the innovation process from conceptual idea to product adoption. The critical issues for product acceptance include system performance in terms of safety, cost, and building code approval. The objective of the experimental portion of the research was to test the performance of the RTA connection system in specific modes and to develop a theoretical method to predict the strength of the connection. A series of experiments to quantify the shear strength and stiffness of six joint configurations assembled with the RTA connector were designed and conducted. The joints were fabricated from solid sawn lumber and three different wood-base composites. The experimental results indicated that the strength of the RTA connector in perpendicular-to-grain and parallel-to-grain orientations can be predicted from a theoretical dowel yield model. The material properties used in the yield model were adjusted for duration of load and safety. Empirical test values were within ±6.3 % of the predicted values from the theoretical model. Joint stiffness was evaluated, modeled and quantified in the linear and non-linear ranges. A structural analysis program was used to design and model a simple RTA building for realistic gravity and wind loads. The structural model was used to predict joint forces that the RTA connector must resist in-service. The computer model predictions were compared to the empirical joint test data. The results indicate that the RTA system can be designed to meet safety and serviceability criteria. A comparison between the estimated costs of a RTA building and the costs of traditional on site construction of a building of equal dimensions indicated that the RTA system is economically competitive.
- Doctoral Dissertations