Reinforced Wood I-Joists with Web Openings Md Shahnewaz 1 ; M. Shahidul Islam 2 ; Moein Ahmadipour 3 ; Thomas Tannert, M.ASCE 4 ; and M. Shahria Alam, M.ASCE 5 Abstract: Prefabricated wood I-joists with web openings are commonly used in light-frame wood construction. The capacity and the failure pattern of such I-joists in the presence of a circular web opening were experimentally investigated on 100 specimens with various sizes and locations of web openings and two different span lengths of 3.66 m (12 ft) and 6.10 m (20 ft). The control I-joists, i.e., I-joists without any opening, failed in flexure in the midspan, whereas most of the I-joists with an opening failed in a brittle and sudden shear mode. The presence of an opening reduced the capacity up to 54% compared to I-joists without web openings depending on the size and location of the opening. Subsequently, to prevent brittle failure and improve capacity, the I-joists were reinforced using two perpendicular OSB collar layers with a variation in the reinforcement length. The effectiveness of reinforcing the web around openings was investigated on another 100 specimens. After reinforcement, brittle premature failure of I-joists was prevented with an increase in capacity up to 27% com- pared to the I-joists with openings. Analytical models to calculate the capacity of unreinforced and reinforced I-joists with openings are proposed, validated with results from previous research, which prove to be more accurate compared to existing models from the literature. DOI: 10.1061/(ASCE)ST.1943-541X.0001747. © 2017 American Society of Civil Engineers. Author keywords: Wood structures; Experimentation; Reinforcement; Regression analysis. Introduction Timber as a Construction Material Timber is a widely used renewable material that exhibits several favorable characteristics, such as high strength-to-weight ratio, low carbon footprint, and good insulation properties. Solid timber as a natural material, however, exhibits very large variability in its properties and quality and can only be used to produce linear mem- bers. Historical timber structures were often characterized by ele- ments that were limited both in their cross-sectional dimensions and length by the dimensions of the existing trees in the surround- ing area (Dietsch and Tannert 2015). To meet the engineering and architectural desires to utilize the sustainable features of timber in homogeneous and planar elements, timber can be broken down into sequentially smaller fractions that can then be reassembled into glued composite members, labeled engineered wood products (EWPs) (Vallée et al. 2017). Depending on the wood fraction used as raw material, grain orientations, glue application, and manufac- turing processes, EWPs can be classified into lumber-based such as glued laminated timber, veneer-based such as plywood or laminated-veneer lumber (LVL), strand-based such as oriented- strand board (OSB) or laminated-strand lumber (LSL), and particle- based products such as Fibreboard. Composite I-Joists EWPs are combined to produce prefabricated composite structural members such as wooden I-joists, which are popular in light-frame construction as floor and roof joists because of their high strength and stiffness, low weight, dimensional stability, and low cost in comparison to solid timber (American Forest & Paper Association 2001). The flanges and the web are glued together to form an I-shaped cross section that can save 50% of wood fiber compared to solid lumber beams (Leichti and Tang 1983; Islam et al. 2011). Composite I-joists often consist of flanges made of LVL or LSL with the web made of OSB or plywood, where the flanges and webs are designed to carry moment and shear forces, respectively, and the stresses between the flanges and web are transmitted through the flange-web glue line. Early studies on wood I-joists (Fergus 1979; Hilson and Rodd 1984; Samson 1983; Leichti and Tang 1983, 1986; Leichti et al. 1990b) focused on determining the influence of the flange and web materials on the capacity, stiff- ness, and stability and provided the groundwork for the widespread structural application of I-joists. Modern wood I-joists are proprietary products with producers providing their specific design values after conducting tests accord- ing to ASTM D5055 (ASTM 2013) and WIJMA (1999). The de- sign criteria for prefabricated composite I-joists include (1) bending resistance, governed by the flanges; (2) shear resistance, governed by the web; (3) deflection limits for live and dead loads; (4) bearing deformation at supports; (5) span-to-height ratio to prevent web instability, especially when web holes are present; and (6) bracing for lateral stability. The manufacturers furthermore list their limi- tations with respect to concentrated loads and web openings. 1 Graduate Research Assistant, Dept. of Civil Engineering, Univ. of British Columbia, Vancouver, BC, Canada V6T 1Z4. E-mail: md .shahnewaz@alumni.ubc.ca 2 Graduate Research Assistant, School of Engineering, Univ. of British Columbia, Kelowna, BC, Canada V1V 1V7. E-mail: shahidul.islam@ ubc.ca 3 Graduate Research Assistant, School of Engineering, Univ. of British Columbia, Kelowna, BC, Canada V1V 1V7. E-mail: moein.ahmadipour@ ubc.ca 4 Associate Professor, Dept. of Wood Science and Civil Engineering, Univ. of British Columbia, Vancouver, BC, Canada V6T 1Z4. E-mail: thomas.tannert@ubc.ca 5 Associate Professor, School of Engineering, Univ. of British Columbia, Kelowna, BC, Canada V1V 1V7 (corresponding author). E-mail: shahria.alam@ubc.ca Note. This manuscript was submitted on October 14, 2015; approved on November 4, 2016; published online on February 13, 2017. Discussion period open until July 13, 2017; separate discussions must be submitted for individual papers. This paper is part of the Journal of Structural En- gineering, © ASCE, ISSN 0733-9445. © ASCE 04017022-1 J. Struct. Eng. J. Struct. Eng., -1--1 Downloaded from ascelibrary.org by University Of British Columbia on 02/14/17. Copyright ASCE. For personal use only; all rights reserved.