Design of a Glulam-arched mountain hut near Whistler, British Columbia
Howatson, Fraser (author) British Columbia Institute of Technology Civil Engineering Department (Degree granting institution)
Research paper/project
http://rightsstatements.org/vocab/InC/1.0/ © Fraser Howatson, 2022. All rights reserved. No part of this work covered by the copyright heron may be reproduced or used in any form or by any means – graphics, electronic, or mechanical including photocopying, taping, or information storage and retrieval systems – without written permission of the author.
British Columbia Institute of Technology
2022
41 pages
The purpose of this project was to design a glulam-arched structure that was suitable for use as a backcountry hut. Large snow and wind loads combined with remote access conditions ensured that the preferred structure would be relatively lightweight and largely pre-fabricated. This project provides a design for a glulam-arched structure. The primary structural members of this design consist of 130 mm x 342 mm D.Fir-Larch 24-EX arches with approximate lengths of 6.3 m for each half of the arch. Each half-arch is comprised geometrically of a lower straight-vertical section which transitions into a constant radius arc in the upper sections. Dead, live, snow, and wind loads were calculated using various methods and approximations. As no sitespecific data for snow and wind loads were available for the proposed elevation, ground snow loads and wind pressures were adopted from the designers of the nearby ‘Kees and Claire’ Hut. For the purpose of calculating internal forces, the arches were assumed to be pinned at both the peak and base connections. As a ‘three-pinned-arch’, the structure is determinant; allowing internal forces to be calculated through equilibrium equations alone. As the structure has a somewhat complex geometry, a numerical model was created to calculate the bending moment, shear, and normal forces acting throughout the members under various load combinations. In general, the largest normal and shear forces were observed at the base and the peak of the arches, respectively, while the largest bending moments occurred mid-span near the transition from vertical to curved sections of the arch. Resistance values for compression, bending moment, and shear were calculated using clauses from CSA- 086 (2017) with supplementary information and procedures from CWC-2017. Considerations for radial tension strength and bearing strength were also made following similar clauses. Though this project does not consider seismic forces, a lateral resistance system was considered against factored wind loads. As the profile of the building is unconventional, general approximations for the NBCC 2015 static wind force calculation procedure were made. The lateral resistance system consists of 13 mm plywood nailed to the exterior of the arches with 2.5” common spiral nails at 75 mm on center. The connections at both the peak and base of the arches are quite similar comprising of 2-6mm steel plates on either side of the member with 2x ½” through bolts. At the base of the arches, a continuous glulam beam spans the five foundation piers with a similar set of connections. The foundations are only considered in compression for this design with the approximate sizing based on an assumed bearing pressure of 100 kPa for the site. Reinforcement design is based on minimum steel requirements as described in CSA-A23 2019.
Huts--British Columbia--Design and construction
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