Wood Stud Walls Research Articles

Quantitative comparisons of resilient channel designs in walls and ceilings

Resilient channel is common within lightweight construction to improve the airborne and impact noise isolation of wall and floor-ceiling assemblies. The authors have previously presented results from systematic studies of resilient channels in wood stud wall assemblies (Internoise 2009; International Congress on Acoustics 2010) and wood-joist floor assemblies (International Congress on Sound and Vibration 2015) in which the effect of brand and model of resilient channel was compared in various assemblies. These studies documented the clear and significant acoustical performance differences between makes and models of channel that would have been considered equivalent before the release of this work. Additional comparative studies have been performed adding to the data previously presented. Acoustical performance is compared and conclusions about products are presented.

Blast resistance of timber structural elements: A state-of-the-art review

The response of structures subject to impulsive loads remains a field of intense research. Whilst traditional construction materials, such as steel and concrete/masonry, have been the focus of most studies, further research on the performance of alternative materials for blast-resistant applications has been driven by their growing use in sustainable construction. Over the last years, engineers have been re-evaluating the use of timber as a prime construction material for a range of building types, from small office to high-rise residential buildings. As a result, there is now a growing need to study the blast resistance of timber structures, as they may become potential targets of terrorist attacks or being placed in the blast-radius of other critical buildings. A review of existing research on the blast resistance of timber structures is presented and key factors on the blast analysis and design of such structures are discussed. Most of the research has been conducted on light-frame wood stud walls, glued- and cross-laminated timber, and addresses material properties under high strain rates, typical failure modes, behaviour of structural connections and retrofitting solutions. Failure modes are reported to be highly dependent on the element layout and manufacturing aspects, and dynamic increase factors for the modulus of elasticity and maximum strength in the ranges of [1.05, 1.43] and [1.14, 1.60], respectively, have been proposed for different timber elements. Mechanical connectors play a significant role in dissipating energy through plastic deformation, as the brittle nature of timber elements compromises the development of their full capacity. Regardless the element type, SDOF models can accurately predict the dynamic response as long as idealised boundary conditions can be considered. Overall, although a good amount of research is available, more extensive research is needed to guide the design and engineering practice and contribute to the development of design codes and testing standards for timber structures under blast loading.

Identifying the critical orientation of wood-frame walls in assessing moisture risks using hygrothermal simulation

Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an efficient analysis, it is important to appropriately select the wall orientation in the simulations. ASHRAE 160 recommends to using orientation with highest amount of annual wind-driven rain (WDR) and the orientation with the least annual solar radiation. The objective of this work was to identify the orientation which leads to the worst moisture performance of different wall assemblies under historical climate in different Canadian cities. Four cardinal orientations (North, East, South, and West) and orientation receiving the highest amount of annual WDR (Default) were tested in this study. The simulations were carried out assuming three scenarios of moisture loads for four different wood-frame (2×6 wood stud) wall systems that differ by their claddings: brick, fibreboard, stucco, and vinyl. With an assumption of no WDR, north facing wall always leads to the worst moisture performance. In the presence of WDR, with and without water source, default orientation leads to the worst moisture performance with few exceptions. As default orientation was based on total sum of WDR, it sometimes may not lead to worst performance and hence hourly distribution of WDR should be taken into consideration.

Sensitivity analysis of hygrothermal performance of wood framed wall assembly under different climatic conditions: the impact of cladding properties

One of the parameters that influences the moisture performance of the wood framed wall assembly is the material properties of exterior cladding. The uncertainties of its properties, would result in a range of wall performance. The objective of this study was to investigate the impact of uncertainties in cladding material properties on moisture performance of wood framed wall assembly under different climatic conditions. A wood framed (2×6 wood stud) wall with exterior brick cladding was simulated assuming 1% rain leakage deposited on the exterior side of sheathing membrane. A parametric study was carried out to analyze the impact of the cladding properties on the moisture response of OSB. The simulations were conducted in five different cities located in different climate zones across Canada. The aim was to identify the most influential cladding property on the moisture response of OSB, i.e., mould growth index and moisture content, to the varying cladding properties under different climatic conditions i.e., different cities under historical and future conditions. In general, it was found that liquid diffusivity is the parameter that has the most influence on moisture response of OSB in all the five cities. Also, the significance of this influence varies depending on the climatic conditions.

Canadian initial-condition climate ensemble: Hygrothermal simulation on wood-stud and retrofitted historical masonry

Given the long lifespan of buildings it becomes inevitable to assess the impact of climate change when designing building envelopes or retrofitting solutions. Hygrothermal simulations would benefit from using a climate ensemble to account for the large uncertainties that come with modelled climate data. However, this has been rarely done so far, and no state-of-the-art methodology exists to implement ensemble data in hygrothermal simulations. This paper presents the application of a Canadian initial-condition ensemble CanRCM4 LE in hygrothermal (HAM) modelling. A brick-clad wood-stud wall assembly and historical solid masonry wall, before and after retrofitting, are analysed for Ottawa, CA. Variations in the HAM model are studied to evaluate whether the ensemble can be represented by one smaller “reduced” ensemble for different studies. And, the potential of climate-based indices to predict this “reduced” ensemble is studied. Further, the uncertainty of the ensemble is analysed, as well as the climate change signal of the damage functions. It is found that the application of a climate ensemble is highly valuable for HAM modelling, as it is able to account for the high uncertainty of climate change data. To maintain the level of information, it is recommended to perform HAM simulations using the entire ensemble. However, there is potential to select a “reduced” ensemble to represent spread of the climate change signal.

Damage level assessment of response limits in light-frame wood stud walls subjected to blast loading

Currently, no systematic approach exists for damage evaluation of light-frame wood structures subjected to blast loading. This paper presents a detailed assessment of the behaviour of 33 full-scale light-frame wood stud walls subjected to a total of 48 shots of simulated blast loading. Detailed documentation of the observed damage allowed for the development of an accurate evaluation strategy of the response limits. The observed response limits are compared to limits derived from single-degree-of-freedom modelling using scaled pressure–impulse diagrams and to current code performance levels. It was concluded that the assumption made in contemporary blast design codes overestimates the ductility ratios for light-frame wood stud walls, and that using a maximum ductility of 2 is more appropriate and safer for blast design. Based on the observed damage levels obtained from the experimental study, the authors propose new ductility ratios corresponding to four damage regions.

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...

Investigating the behaviour of typical and designed wall-to-floor connections in light-frame wood stud wall structures subjected to blast loading

The performance of light-frame wood stud walls under simulated blast loading has so far been limited to investigating the behaviour of structural elements with idealized boundary conditions. The current study investigates, experimentally and analytically, whether walls with prescriptive connection detailing for low and high seismic and wind regions are capable of resisting blast loadings such that the walls’ ultimate capacity can be reached. The study also investigates the behaviour of different connections with various design capacity levels to develop failure in the stud wall system rather than in the connection. A total of ten full-scale walls with different boundary conditions were tested dynamically. The results showed that typical prescriptive connection detailing did not perform adequately. Designed connections performed well, but the findings show that basing the connection design solely on capacity may be inadequate. Single degree-of-freedom modelling may only be utilized if damage in the connections is limited.

Investigation of Dynamic Increase Factors in Light-Frame Wood Stud Walls Subjected to Out-of-Plane Blast Loading

Abstract The results of an experimental program investigating the dynamic increase factors of light-frame wood stud walls under blast loading are presented in this paper. A total of 20 walls with two different sheathing types and thicknesses were tested to failure under static and dynamic loading. The study found that the observed failure mode for both static and dynamic loading was flexure; however, a difference in the type of flexural failure was observed. Average increase factors of 1.40 and 1.18 on the resistance and stiffness, respectively, were found. A detailed literature review combined with the test results from the current project yielded a strong correlation between the increase in strain rate and the relative increase in strength and an equation relating the dynamic increase factor (DIF) on the resistance to strain rate was proposed for strain rates in the ranges of 1.67– 1.65 × 10 3 s − 1 .

Integrated LCA–LEED sustainability assessment model for structure and envelope systems of school buildings

In Canada and USA, nearly 80 million students and teachers spend at least eight hours daily in schools that could be unhealthy and restrict their ability to learn. Despite this fact there is lack of adopting sustainability principles in school buildings. Even though life cycle assessment (LCA) and LEED® could serve as sustainability measurement tools, studies show that the integration of sustainability principles to LCA has not become standard practice yet. This paper presents an integrated LCA–LEED model that incorporates LCA into LEED and assigns corresponding LEED scores to achieve a high level of sustainability assessment, for the structure and envelope systems of Canadian school buildings. In this model, the selection of the most sustainable structure and envelope type for school buildings is done through the evaluation of three categories of the LEED rating system: energy and atmosphere, materials and resources, and LCA (incorporated under the innovation and design process category of LEED). Various options are tested by considering structures such as concrete, steel, masonry and wood, and envelope types such as precast panels, steel stud, wood stud and cavity wall. Energy simulation is performed by eQUEST® (version 3.64) program and LCA is performed by ATHENA® impact estimator. The results show that concrete and masonry buildings have high energy consumption and global warming potential during certain life cycle stages such as manufacturing, construction and demolition. However they have lower annual energy consumption and environmental impact during the operating stage, as well as for the overall life span. Concrete building with minimum insulation has obtained the highest total LEED score (19) followed by masonry (17), while steel and steel-masonry buildings have the least score (14).

Acoustical performance of damped gypsum board in double wood stud wall assemblies

A common assembly for demising walls in multifamily residential projects is double wood studs with multiple layers of gypsum board on one or both sides. While improving the acoustical performance, installing multiple layers of gypsum board adds significant cost to the project; complicates scheduling, materials storage, and delivery; and may require additional inspections. On some types of projects, removing these complications has been desired. In these cases, the use of damped gypsum board has been pursued to reduce the number of layers of gypsum board on the demising wall while attempting to achieve equivalent acoustical performance. Acoustical testing was performed to determine if damped gypsum board was a suitable alternative to the standard gypsum board assemblies in typical demising constructions. Laboratory and field tests were performed on double wood stud walls with a variety of gypsum board configurations, and the results are presented.

Seismic Performance of Low-Rise Wood-Framed and Reinforced Masonry Buildings with Clay Masonry Veneer

AbstractThis paper describes a coordinated experimental and analytical study that investigated the seismic performance of wood-stud construction with clay masonry veneer and of RC masonry construction with clay masonry veneer designed according to current U.S. building codes. As part of this study, two 1-story buildings were tested on a shaking table. Both had clay veneer on the outside. One had wood-frame walls for the backing and load-resisting system, whereas the other had RC masonry walls. With one exception, the behavior of the veneer in the wood-framed building was satisfactory up to levels of shaking consistent with the design level earthquake. That exception was related to the relatively low pullout strength in wet wood of the conventional nails used to attach the veneer connectors to the wood-stud wall. On the basis of this study, code changes have been implemented to require the use of higher-capacity fasteners for such applications. The wood-frame building specimen itself did not collapse under...

Simplified Methods for Improving the Blast Resistance of Cold-Formed Steel Walls

In recent years, cold-formed steel stud walls have become an attractive alternative to wood stud walls. Relative to wood, cold-formed steel is highly ductile, sustainable, and unaffected by insects, mold or rot. Research has demonstrated that cold-formed steel stud walls can perform well when subjected to large blast threats, but such performance has depended upon specially designed fasteners that are expensive to manufacture and require experienced workers to install properly. Despite the potential performance of these types of wall systems when specialized fasteners are used, current U.S. Department of Defense design guidelines for conventionally constructed steel stud walls use acceptability criteria that are much more conservative than wood stud walls due to the lack of data available. Thus, the goal of the current research effort is to develop techniques for mitigating large blast threats acting against steel stud walls using conventional construction methods and materials. The research includes controlled laboratory tests that are intended to identify the various failure mechanisms that can occur for different combinations of wall system parameters. Variables considered in the testing program include stud and track section properties, stud-to-track connection details, stud orientation and wall layout, and sheathing system properties. Based on the results obtained from the testing program and supporting analyses, the most promising wall system designs will be identified, and design guidance will be developed. Final designs will be tested under actual blast loads to verify performance and to ensure that wall systems behave as desired.

Seismic Performance Tests of Masonry and Masonry Veneer

Abstract This paper summarizes the preliminary findings of a research project on performance-based design of masonry and masonry veneer. The project includes quasi-static testing of clay masonry veneer with wood-stud and concrete masonry backings; shaking-table tests of concrete masonry and wood-stud wall segments with clay masonry veneer; and shaking-table tests of a full-scale wood-stud structure with clay masonry veneer and a concrete masonry structure with clay masonry veneer; and nonlinear analytical modeling. Based on the test results, recommendations are presented for refinements to current seismic design and detailing provisions for masonry and masonry veneer.

Dynamically loaded light-frame wood stud walls: experimental verification of an analytical model

Light-frame wood structures may deform well beyond the elastic limit when loaded by dynamic forces such as earthquakes and sea wave impacts. This paper reports the results of an investigation into the response effects of structural modeling assumptions typically made in the design of light-frame wood structures. Two dimensional and three dimensional models based on previous research were developed to simulate such responses and examine the validity of such models. The models utilize the finite-element method and include options of nonlinear connection properties, elastic constitutive laws of wood material, large deformations, contact forces, and inertial forces. The models were subjected to an estimate of the impact load imparted by a rapidly moving sea wave. To validate the models, the results of a wave-channel experiment of a full-scale wall were used wherein the wall was instrumented with reaction load cells, displacement transducers, and strain gauges on plywood sheathing and wood framing. A closed-loop hydraulic system utilizing a time varying loading function generated the wave trains. The resulting reactions, deformations, and strains were recorded as functions of time while high-speed cameras visually recorded the failure modes and wall behavior. Material tests were conducted before and after testing to record both the observed member properties and the localized section properties. Connection tests were conducted to provide the ultimate strengths for input in the finite element model. Reasonable agreement between the experimental and analytical results over the duration of the analysis depended on the model and model assumptions as well as the result of interest. The three dimensional model captured observed failure modes including rigid-body motions after connection failures and may reliably be used to analyze similar nonlinear systems loaded well beyond the elastic limit.

Lateral Load Resistance Evaluation of Wood- and Steel-Stud Partition Shear Walls

This paper summarizes the findings of an experimental study to characterize the cyclic racking and monotonic loading performance of wood-stud and steel-stud wall specimens, which were sheathed on both faces with gypsum wall board (GWB). Some specimens were finished with joint compound at the GWB joints and over screw heads. The study provided data on monotonic and cyclic hysteresis load-displacement relationships. Based on the visual inspection of the specimens during the tests, several aspects of the failure modes were noted. Shear-load capacity and drift capacities were determined based on the envelope curves of the hysteresis cycles. A comparison of the envelope curves for steel-stud and wood-stud specimens provided insight as to the relative behaviors of the two wall system types, including capacity, measures of ductility, and energy dissipation. Finally, the study provided better understanding of the effects of finishing GWB joints on the shear capacity of the wall systems.

Comparison of acoustical measurements of demising walls in luxury condominiums and townhomes to illustrate the importance of decoupling the mass layers

Field Sound Transmission Class (FSTC) tests and acoustical measurements of impact noise from cabinet door and drawer impacts were made of demising walls in a number of multifamily luxury townhomes and luxury condominium tower units due to complaints from residents about noise intrusion from adjacent living units. The demising wall constructions included concrete or cmu with gypsum board attached, gypsum board on wood studs, and gypsum board on metal studs. The results of these measurements will be presented to illustrate the need to decouple the mass layers to maximize the acoustical performance. A case study of one project will be presented showing the effects of incremental changes made to a base wood stud wall with gypsum board on each side (STC 36) in which added mass (STC 44), added mass plus decoupling (STC 62), and decoupling with reduced additional mass (STC 58) were tested in an effort by the developer to strike a balance between acoustic performance and cost.

Reliability of Light-Frame Wall Systems Subject to Combined Axial and Transverse Loads

Wood frame walls are essential subassemblies used to transmit roof, floor, wind, and seismic loads into lower stories and eventually into the foundation of light-frame structures. There has been some discussion and debate in recent years over appropriate system factors for use in the design of repetitive wall members, which typically are much smaller in the cross section than floor joists. In addition to having greater flexibility than floors, wood stud walls also may be subject to the actions of combined loads, and their load-sharing behavior may be significantly influenced by the presence of openings. As a precursor to evaluating system factors for design, this study investigated load-sharing and system effects in light-frame walls subject to combined axial and transverse loads. An analytical model was developed to account for partial composite action, load-sharing, two-way action, and openings in the wall system. The model consisted of two main components: A system model and a member model. The system ...

Modeling Wood Walls Subjected to Combined Transverse and Axial Loads

Repetitive-member wall systems are among the most essential structural systems in conventional light-frame construction. Wood stud walls serve a variety of structural functions, particularly in regions of high natural-hazard risk, carrying axial forces, in-plane shear forces, and out-of-plane forces. This paper describes a structural analysis model for wood walls under transverse wind loads combined with either axial tension from wind uplift or axial compression from snow and live load suitable for reliability studies. The average model results compared well to available wall test data. Monte Carlo simulation was used in sensitivity studies of the transverse ramp-load behavior of walls under various levels of axial load. These simulations show that the model captures the range of possible behaviors of stud walls under various levels of axial load, both compression and tension. The model is accurate and simple enough to be used in reliability analyses, which will be described in a later paper.

Water entry function of a hardboard siding-clad wood stud wall

This paper presents derivation of a water entry function of a hardboard siding-clad wood stud wall assembly. Water entry function provides input data to heat, air and moisture simulation models to facilitate the prediction of the long-term water entry performance of the specific assembly. Initially, an experimental work was conducted in which the hardboard siding-clad wood stud wall specimen was subjected to simulated driving rain loads, i.e. spray rates and static pressure differential. The specimen included a drainage cavity and specific deficiencies such as a missing length of sealant at the interface between the cladding and penetrating components, i.e. window, ventilation duct and electrical outlet. Water entering the deficiencies was collected at the drainage and stud cavities just below the penetrating components. Water entry results provided information on water entry rates as functions of simulated driving rain loads, which in turn permitted the development of a water entry function of the assembly. Entry function is a basic relationship that relates the quantity of water entry in a certain location within the assembly to the simulated driving rain loads. Measured climatic data of a specific climate, i.e. rainfall intensity and wind speed, was related to the simulated driving rain loads, and the entry function provided a means of estimating the water entry loads of the hardboard siding-clad wood stud wall assembly located in the specific climate.