Wood I-joists Research Articles

Withdrawal Capacity of a Novel Rigging Device for Prefabricated Wood I-Joist Floor Panels

Prefabricated wood construction relies heavily on efficient material handling, yet rigging system design for floor panels remains understudied. This study introduces a novel rigging device that attaches to prefabricated wood I-joist floor panels using self-tapping screws, avoiding potential damage caused by predrilled holes in the sheathing panels and framing members. To establish allowable lifting capacities and optimal installation practices, comprehensive withdrawal tests were conducted on 114-floor panel specimens. Factors influencing withdrawal capacity, such as anchor plate placements, flange materials and width, screw type and quantity, and sheathing panel thickness, were systematically evaluated. Results indicate that withdrawal capacity does not scale linearly with screw quantity and that anchor plates with eight screws centered on the flange enhance performance by up to 20% compared to four-screw configurations. Unexpectedly, thinner sheathing panels yielded higher capacities, potentially due to increased screw penetration depth in the joist flange. In addition, anchor plate orientation, flange width, and flange materials also impact capacity. These findings provide essential data for designing reliable and efficient rigging systems in prefabricated wood construction.

Calculation of sound transmission parameters for wood-frame and mass timber assemblies

While much of it is proprietary, a significant amount of the data from sound transmission tests performed on mass timber assemblies has been shared in the public domain. Previous efforts at using this data to develop empirical models for estimating single-number ratings of floor assemblies have been limited in scope and have not always yielded accurate results. In order to provide an additional means of demonstrating compliance with code requirements, the American Wood Council (AWC) has developed calculation-based analysis approaches for deriving STC and IIC ratings for assemblies constructed with wood-based framing and mass timber. As required by the International Building Code (IBC), these analysis procedures are based on comparisons of data from floor/ceiling assemblies having STC and IIC ratings as determined by the test procedures set forth in ASTM E90 and ASTM E492, respectively. The models presented in this report can be used to estimate STC and IIC ratings of: a.) light-frame floor/ceiling assemblies framed with either sawn lumber, wood I-joists, or wood trusses and b) mass timber floor/ceiling assemblies constructed with either cross-laminated timber (CLT), dowel-laminated timber (DLT), or veneer-based mass timber. Descriptions of the models are provided. Validation and application of the models are also discussed.

Bending Behaviour of Different Types of Timber I-Joist

Engineered wood I-joist is a structural system that comprises of flanges and web elements, and utilised as beams in buildings. Both elements must work together as a structural system to fit and meet the strength behaviour of a solid wood beam. The main objective of the study was to determine the bending strength behaviour of I-joist which produced from three types of jointed technique (finger, L-butt and nail plate) of oriented strand board (OSB) web element with two types of flange element (Keruing solid wood and laminated veneer lumber (LVL)). A total of 18 specimens of I-joist were tested to determine the bending behaviour, especially the modulus of elasticity (E) and modulus of rupture (MR). From the result of testing, LVL flanges specimen were obtained almost as strong as the specimens with solid wood flanges. Additionally, either solid wood or LVL flange was shown non-significant variances in bending strength behaviour because the MR values of the I-joist were insignificantly affected by flange element material. The I-joist specimen with finger jointed web was observed to be the strongest specimen when compared with other joints. Furthermore, the weakest joint among the three types of joints were fabricated with nail plate jointed web. The failures mode of the I-joist specimens were observed to fail due to tension or compression.

Simultaneous evaluation of bending and shear stiffness of wood I-joists by transverse vibration tests

Prefabricated wood I-joists are widely used in lightweight wood constructions. Accurate and efficient measurements of their elastic properties are of great importance for predicting their mechanical behaviour during structural design. In this study, an alternative algorithm for simultaneous measurement of bending and shear stiffness of wood I-joists was developed for transverse vibration techniques based on Timoshenko beam theory. Sixty-five wood I-joists with thirteen configurations were tested by using the proposed modal testing method as well as traditional third-point bending tests. Based on the test results, the influences of section properties of wood I-joists on the shear rigidities were studied. It was found that the transverse vibration tests can be simply and efficiently implemented to determine the true and apparent bending stiffness of wood I-joists. In addition to the I-joist depth, the shear rigidities are also influenced by the web thickness and flange width. More importantly, shear deflection coefficients of tested wood I-joists are significantly larger than those theoretical values currently used by wood I-joist manufacturers.

Wood I-joists with web holes and flange notches: A literature review

Wood I-joists are increasing being used as floor and roof joists in the construction of commercial and residential buildings, due to their light weight, high strength, easy handing, and good durability. Web holes and flanges notch are often made in the joists to allow passage of ventilation systems, electrical wiring, and service pipes, but it is strictly restricted by joist manufactures. If not handled improperly, it is very easy to produce the crack growth and eventually result in catastrophic damage. This paper presents a comprehensive review on experimental studies investigating the mechanical performance of wood I-joists web holes and flange notches. The effect of flange-notches and web-holes on the structural performance (e.g., ultimate load carrying capacity, shear strength and stiffness) of unreinforced I-joists are discussed and typical failure modes are described. Reinforcement techniques may be required to improve the mechanical behavior of deficient joists, and the existing design approaches are presented. Based on the findings from this review, recommendations are proposed for future works, which can provide a reference for further research on wood I-joists.

Lateral Load Performance of Panelized Wood I-Joist Floor Systems

Abstract Panelized light wood frame construction is becoming more popular due to the faster construction time and shortage of onsite skilled labor. To use light wood frame panels effectively in panelized floor systems, panel-to-panel joints must be fastened adequately to allow load transfer between panels. They must also possess in-plane shear strength and stiffness comparable to stick-built, staggered-sheathed assemblies. This study was designed to develop efficient and effective panel-to-panel joints for connecting adjacent floor panels built with wood I-joists and evaluate the efficiency of the joints in achieving diaphragm action. At first, a number of these panel-to-panel joints were tested in the laboratory using a small-scale diaphragm test setup to determine their efficiency in transferring in-plane forces between panels. Test results showed that a small decrease in in-plane stiffness was expected for the most effective joints, but their strengths were significantly higher than at the same location in a conventional site-built floor diaphragm. The presence of blockings and use of two-row nailing were found to considerably improve stiffness and strength. These features can be used to mitigate the potential reduction in mechanical performance of panelized floor construction, in comparison with the site-built wood I-joist floor.

Comparison of Lateral Load Performance of Light Wood Diaphragms Built with Sawn Lumber and Wood I-Joists

AbstractDiaphragm design provisions in North America were originally developed based on the performance of diaphragms constructed with sawn lumber framing members. Although these design guidelines ...

Development of Rigging System for Prefabricated Wood I-joist Floor Panels

Panelized building construction are highly mechanized. Material handling and lifting equipment dominate construction sites and constitute the critical element in achieving productivity. In recent construction practice, panelized wood I-joist floor panels are normally lifted into place by mobile crane using flexible slings inserted through the predrilled holes on the I-joist web and sheathing panels above the I-joist top flange and then wrapped around the I-joists at the four corners. However, the pre-drilled holes on the web and sheathing may weaken the floor panels. Moreover, a range of techniques for lifting and handling mass timber panels have been developed. A typical rigging technique consists of a lifting ring and a steel plate with pre-drilled holes. By using several self-tapping screws, the panel was connected with the rigging device for lifting. However, since prefabricated I-joist floor panels are much lighter than mass timber panels and the I-joist flange is relatively narrow and thin, the rigging device for mass timber panels cannot be applied directly to I-joist floor panels, but a modified design can be developed for prefabricated I-joist floor panels. In the present study, a new rigging device was designed for prefabricated wood I-joist panels and their load capacity was evaluated by withdrawal tests. Several factors influencing the withdrawal capacity were investigated including screw types and quantities, flange width and materials, and OSB thickness.

Investigation of the Lateraltorsional Buckling Behaviour of Engineered Wood I-Joists with Varying End Conditions

Abstract Beam members, especially those that have large depth/width ratios and long spans, are prone to lateral-torsional buckling as a possible mode of failure. Laboratory testing rarely takes into account actual end conditions and initial imperfection which might have a significant impact on the buckling behavior of beams. The current research project aims to investigate the lateral-torsional buckling of wooden I-joists with realistic boundary conditions used in construction. A total of 41 joists were tested using various commercial joist hangers and enhanced connections to represent different support conditions. A numerical 3D model was also developed using commercially available finite element program ABAQUS to determine the buckling loads and associated mode shapes of joists similar to those tested. Based on the results from the current study it is recommended that 20% reduction in the critical moment capacity be considered in order to take into account the use of joist hangers typically used in construction. Finite element analysis of the linear eigenvalue buckling load was found to be in reasonable agreement with the experimental results. The nonlinear behavior of the joists was found to be influenced by the initial imperfections. The ultimate critical load was attained at large lateral displacement of the joists due to their non-linear behaviour. This observation could have a significant implication on design and should be investigated further.

Investigation of the lateral-torsional buckling behaviour of engineered wood I-joists with varying end conditions

Beam members, especially those that have large depth/width ratios and long spans, are prone to lateral-torsional buckling as a possible mode of failure. Laboratory testing rarely takes into account actual end conditions and initial imperfection which might have a significant impact on the buckling behavior of beams. The current research project aims to investigate the lateral-torsional buckling of wooden I-joists with realistic boundary conditions used in construction. A total of 41 joists were tested using various commercial joist hangers and enhanced connections to represent different support conditions. A numerical 3D model was also developed using commercially available finite element program ABAQUS to determine the buckling loads and associated mode shapes of joists similar to those tested. Based on the results from the current study it is recommended that 20% reduction in the critical moment capacity be considered in order to take into account the use of joist hangers typically used in construction. Finite element analysis of the linear eigenvalue buckling load was found to be in reasonable agreement with the experimental results. The nonlinear behavior of the joists was found to be influenced by the initial imperfections. The ultimate critical load was attained at large lateral displacement of the joists due to their non-linear behaviour. This observation could have a significant implication on design and should be investigated further.

Flange-notched wood I-joists reinforced with OSB collars: Experimental investigation and sensitivity analysis

A total of 220 four-point quasi-static bending tests were performed on 3.66 m and 6.10 m long wood I-joists. In addition to control specimens, two different notch sizes (100 × 100 mm and 100 × 150 mm) at three different locations (305, 455 and 610 mm from the support) and two Oriented Strand Board (OSB) collar reinforcements were considered to evaluate their impact on failure mode, stiffness, and load-carrying capacity. While the joist from the control series without notch failed in flexure, the notched I-joists failed mostly in combined flexure-shear failure. It was found that the reduction in capacity and stiffness increases with the increase in notch depth and notch distance from support. Reinforcing the I-joists with OSB collars at the notch prevented brittle shear failure and improved capacity compared to the unreinforced I-joists. Regression models were proposed to estimate the capacity of unreinforced and reinforced I-joists with flange notches. By conducting a sensitivity analysis, it was found that the I-joist aspect ratio, notch depth, notch location and reinforcement type have a significant impact on the capacity of reinforced I-joists.

Bending properties of wood I-joist made with pinus (Pinus sp.) and curupixá (Micropholis venulosa) flanges

Bending properties of wood I-joist made with pinus (Pinus sp.) and curupixá (Micropholis venulosa) flanges

Experimental and numerical investigation of lateral torsional buckling of wood I-joists

This paper investigates the elastic lateral torsional buckling capacity of wood I-joists. A sensitivity analysis determined that the orthotropic material properties that affect the critical buckling load of wood I-joists are the longitudinal modulus of elasticity, the transverse shear modulus of the flanges, and the elastic modulus of the web. A 3D finite element (FE) model was developed using experimentally determined material properties and initial imperfections. The study found that FE linear predictions provided reasonable agreement with the experimental buckling loads. The FE geometric nonlinear analysis was able to replicate the experimental nonlinear behavior that was observed during the test. Comparison with contemporary North American design standards showed significant conservatism in the design approach.

Reinforced Wood I-Joists with Web Openings

AbstractPrefabricated 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 ope...

Evaluation of Remediation Techniques for Circular Holes in the Webs of Wood I-Joists

Remediation methods and strength predictions were evaluated for wood I-joists with single, circular holes in the webs, leaving utilities in place. A full-scale bending test using four equally spaced point loads was applied to three depths of joists with varying flange widths and span lengths of 4.88 and 2.44 m. Failure modes for long-span joists without holes were in the flanges in tension, compression, or lateral buckling, but once a hole was introduced, the majority failed in shear. The curved beam approach and manufacturers software were used to predict strength. Seven remediation techniques were investigated initially, and remediation effectiveness was evaluated on the basis of strength, stiffness, and ease of installation/cost. The oriented strand board (OSB) collar remediation worked very well and returned 8 of 12 series of joists to a strength statistically equivalent to the “no hole” condition. The OSB collar was not quite as effective in returning stiffness to the joists but was easier to install and less expensive than a laminated strand lumber patch.

Buckling Behavior of Sinusoidal Web for Composite Wood I-Joist with Elastically Restrained Loaded Edges under Compression

AbstractWood I-joists are efficient and lightweight structural members that are well suited for long-span floor and rafter applications. However, because of the thin-wall nature of the web and relatively low stiffness, local web buckling of the joist is an issue that must be considered. To increase the buckling capacity of these joists, investigators at West Virginia Univ. and Univ. of Idaho developed web panels with a sinusoidal geometry, instead of the flat web panels commonly used for prefabricated I-joists. This study presents analytical modeling, experimental testing, and finite-element (FE) analysis of the local buckling capacities of these sinusoidal web panels under compression. The flanges and web are not rigidly connected; thus, this problem can be described as the instability of a sinusoidal shell with two rotationally restrained loaded edges under compression. Using an energy method, the critical compression buckling stresses were obtained in terms of the elastic rotational restraint stiffness...

Effect of Density on the Properties of Oriented Strandboard Web Stock Used in Wood I-Joists

Numerical simulation of structural member behavior requires knowledge of mechanical properties. This study proposes a methodology to obtain reliable mechanical properties of the oriented strandboard (OSB) web of I-joists, including variability. OSB panel samples were scanned by X-ray densitometry to measure in-plane density variation. Specimens were cut from predefined homogeneous density areas in three different orientations (parallel, perpendicular, and diagonal to the strong axis) to measure three basic elastic properties required for an elastic model of the OSB web of I-joists: modulus of elasticity (MOE) parallel and perpendicular to the panel's strong axis and shear modulus (G). Given the required small specimen size, shear modulus was determined using a combination of in-plane tensile MOEs, including MOE at 45°. Results showed a strong relationship between OSB density and small-scale mechanical properties: coefficients of determination (R2) varied between 0.57 and 0.79. This provided information on I-joist OSB web mechanical properties as a function of density for input into a numerical model. Properties showed considerable variability in the 600 to 900 kg/m3 density range, with a 207 percent increase in tensile modulus of elasticity in the parallel direction, 187 percent in the perpendicular direction, and 172 percent at 45°. The mechanics-based OSB shear modulus equation used proved to be reliable.

Study of the Bonding Property between Flanges and Web Plates of Wood I-Joist

Wood I-joists is a kind of wood-based engineering material which was widely used in wood construction. As it is in fact, the property of I-joists are influenced not only by normal stress but also by a part of shear stress when they are taking into application. In this study, the effects of different factors were evaluated on the tensile property of the wood I-joists. The factors include the depth of the tanks on the flanges, the length of joint and different kinds of flanges. The method of control test was used in the process of the experiment design, and tensile shear test were taken during the experiment at the aim of testing the bonding property of the I-joists using a universal mechanical testing machine. Ultimately, it has been discovered that the factor of depth of the tanks and the length of the joint influence the bonding property mostly. So this paper offers the optimal fabrication technology of the I-joists to make it is possible for the increase of reliability when wood I-joists are taken into application.

Optimization Design of the Bonding Property between Flanges and Web Plates of Wood I-Joists

Wood I-joists is a kind of wood-based engineering material which was widely used in wood construction. As it is in fact, the property of I-joists are influenced not only by shear stress but also by a part of normal stress when they are taking into application. In this study, the effects of different factors were evaluated on the tensile property of the wood I-joists. The factors include the depth of the tanks on the flanges, the amount of glue spread and adhesive type. The method of orthogonal test was used in the process of the experiment design, and tensile test were taken during the experiment at the aim of testing the property of the I-joists using a universal mechanical testing machine. Ultimately, it has been discovered that the factor of adhesive type is the most influential one in the three factors which had been listed. So this paper offers the optimal fabrication technology of the I-joists to make it is possible for the increase of reliability when wood I-joists are taken into application.

Unprotected Floor Assemblies and Tenability Conditions in a Test House Under Two Basement Fire Scenarios

A full-scale experimental program was undertaken to study the impact of two basement fire scenarios on the structural integrity of unprotected floor assemblies above a basement and the tenability conditions in a test facility representing a typical two-storey detached single-family house with a basement. The experiments utilized relatively severe, fast-growing fires set in the basement, which had an unprotected (unfinished) ceiling, to challenge the structural integrity of the floor system above the basement, which provides the normal egress route on the first storey for occupants. A range of floor assemblies constructed with various types of engineered floor joists and trusses (including wood I-joists, steel C-joists, metal plate wood trusses and metal web wood trusses) and with solid-wood joists, were used in the experiments with the basement side unprotected (unsheathed). Potential exposure to toxic gases, heat and smoke obscuration under the test conditions was analyzed to estimate the time available for escape. The results help establish the sequence of fire events such as fire initiation, smoke alarm activation, onset of untenable conditions, and structural failure of the floor assembly above the basement to understand how these factors affect the ability of occupants on the upper storeys to escape in the event of a basement fire.