Ghasan Doudak

Experimental Evaluation of Load Paths in Light-Frame Wood Structure

Despite much experience that low-rise wood buildings are vulnerable to damage by extreme wind events, few such structures have been tested in fullsize to understand how they respond to wind loads as a whole system. This paper presents a study that measured internal force flows throughout the framing of a typical North American single-story structure with platform construction. Applied forces were concentrated horizontal loads normal to walls and patches of gravity loads on the sloped roof. Two series of load cells were embedded into the system, between the roof trusses and supporting walls and between the floor platform and the foundation. It was observed that even localized external forces have effects that propagate through the entire system. For instance, horizontal loads applied near eave level or to the roof were reacted at the top of the foundation around the entire wall perimeter of the building footprint, both parallel and transverse to the applied loading. For vertical loads, measurements showed ...

Nonsway Model for Lateral Torsional Buckling of Wooden Beams under Wind Uplift

AbstractSimply supported wooden beams nailed to deck boards subjected to wind uplift forces are subjected to compressive stresses at their bottom fibers. Because the restraining action provided by decking is at the top fibers, it is unclear to what extent such restraints are effective in controlling lateral torsional buckling as a possible mode of failure under wind uplift. Present design standards do not have provisions for such cases. Thus, the present study aims to quantify the effect of restraints provided by the deck boards on the lateral torsional buckling capacity of twin-beam-deck systems under wind uplift. Toward this goal, a series of analytical and numerical models were formulated. All models capture the continuous rigid lateral restraint and partial twisting restraint provided by the deck boards. The effects of load type and load position were investigated. The bending stiffness of deck boards was observed to have a significant influence on the lateral torsional buckling capacity of twin-beam-...

Analytical Approach to Establishing the Elastic Behavior of Multipanel CLT Shear Walls Subjected to Lateral Loads

AbstractStructures assembled with cross-laminated timber (CLT) panels, and designed to resist gravity and lateral loads, are being considered as viable options for low-rise to mid-rise buildings. I...

Experimental and Analytical Investigation of Cross-Laminated Timber Panels Subjected to Out-of-Plane Blast Loads

AbstractPresented in this paper are the results of an experimental program investigating the out-of-plane behavior of CLT panels under static and blast loading. A total of 18 CLT panels, with panel...

Effect of Eccentric Lateral Bracing Stiffness on Lateral Torsional Buckling Resistance of Wooden Beams

An energy-based solution is developed for the lateral torsional buckling (LTB) analysis of wooden beams with flexible mid-span lateral bracing offset from section mid-height and subjected to uniformly distributed or mid-span point load. The study shows that such beams are prone to two potential buckling modes; symmetric or anti-symmetric. The symmetric mode is shown to govern the capacity of the beam for low bracing stiffness while the anti-symmetric mode governs the capacity when the bracing stiffness exceeds a threshold value. Using the present formulation, the threshold bracing stiffness required to suppress the symmetric mode and maximize the critical moments is directly obtained by solving a special eigenvalue problem in the unknown bracing stiffness. The technique thus eliminates the need for trial and error in standard solutions. A parametric study is conducted to investigate the effect of bracing height, load height, and bracing stiffness on the critical moments. A large database of runs is genera...

Lateral Torsional Buckling of Wooden Beams with Midspan Lateral Bracing Offset from Section Midheight

AbstractAn energy-based solution is developed for the lateral torsional buckling analysis of wooden beams with a midspan lateral brace subjected to uniformly distributed loads or midspan point load...

Contribution of Type-X Gypsum Wall Board to the Racking Performance of Light-Frame Wood Shear Walls

AbstractThis paper presents an experimental investigation of the racking performance of light-frame wood shear walls to evaluate the effect of Type X gypsum wall board (GWB). Twelve shear walls sheathed with oriented strand board (OSB) alone, GWB alone, or in combination were tested under static monotonic or reversed cyclic lateral load. The racking performance of these wall specimens in terms of stiffness, strength, ultimate displacement, ductility, energy dissipation, and failure modes was investigated. Specifically the effects of panel orientation, GWB panel joint taping, and double-layer GWB were examined. It was found that shear walls sheathed with GWB provide ductility ratios similar to or higher than those of OSB sheathed walls. The direct superposition rule can be applied to estimate the overall strength of a shear wall sheathed with single-layer OSB and GWB on opposite faces, provided there is no panel joint taping and the panel orientation is the same for both materials. The superposition rule p...

Predicting the Fundamental Period of Light-Frame Wood Buildings

AbstractThis paper presents a research investigation of the period formulation in the national building code of Canada through testing and modeling of a light-frame wood structure. The experimental aspect of the study was focused on ambient vibration measurements, and a simple analytical shear-building model was developed to study the effect of multistory sway deflections. The results of the study showed that the calculated periods based on the code equation could be conservative if used to determine seismic base shear. Estimates for building stiffness are evaluated using the deflection equation for wood shearwalls from the current Canadian timber design standard. The calculated fundamental periods using the multiple-degree-of-freedom shear-building model are compared with the experimental results.

Floor Vibration Serviceability Problems in Wood Light-Frame Buildings

AbstractExcessive floor vibrations can occur in wood light-frame buildings and cause inconvenience to occupants in terms of unsatisfactory serviceability. There has been much unresolved debate about how to perform vibration serviceability design calculations for such floors. The research reported in this paper is built around field observations of the vibration behaviors of floors in building superstructure constructed using alternative contemporary wood materials using advanced vibration test and data analysis techniques, and synthesis of findings with existing knowledge. Field investigations were performed on residential units of two multioccupancy multistory buildings having distinctly different architectural and construction features. Those buildings are similar to many in North America. Detailed modal testing was performed with the objective of understanding effects associated with construction method choices made by engineers. Analysis of the data showed that architectural and construction detailing...

Investigating the Behavior of Light-Frame Wood Stud Walls Subjected to Severe Blast Loading

AbstractAn understanding of the behavior of wood stud walls in a region corresponding to hazardous-blowout damage levels is currently lacking. The focus of the current study is on investigating the flexural response of full-scale wood stud walls subjected to pressure-impulse combinations that would yield severe damage levels. Static material properties were determined and used as input in an analytical model that considers the nonlinear behavior of stud-to-sheathing joints, as well as high strain-rate effects. Experimental results showed that premature sheathing failure could occur prior to full flexural stud response, and that sheathing panel debris could be generated. The use of thicker sheathing and screws shifted the failures to the studs, while decreasing the amount of debris. Welded wire mesh was successfully used as a reinforcement of the sheathing or as a catcher system while maintaining the residual axial capacity of the studs. A single-degree-of-freedom material-predictive model was successfully...