Light-frame Wood Research Articles

Seismic Performance Assessment of Wood Light-Frame Shearwalls Using the Performance-Based Unified Procedure

Seismic Performance Assessment of Wood Light-Frame Shearwalls Using the Performance-Based Unified Procedure

Lateral response of post-tensioned pendulum shear walls

This paper presents an experimental evaluation of a new interface configuration for unbonded post-tensioned shear (UPTS) walls. In the proposed configuration, the wall-base interface is shaped in a circular profile. This circular profile presents a major difference from the currently used flat profile at the wall-base interface of rocking UPTS walls. During lateral response, this circular profile induces the wall to predominantly rotate as a rigid body about a fixed point without uplift, and the system dissipates energy through the contact friction that develops at the wall-base interface. This rigid body motion resembles that of a pendulum, thereby designating this system as a pendulum UPTS wall. At this stage, research has demonstrated the many advantages of this system by proof-of-concept testing of a pendulum light-frame wood (LiF) UPTS wall specimen under increasing levels of post-tensioning force. Compared with rocking UPTS walls, experimental results demonstrate that besides performing damage-free when subjected to high drift levels, the proof-of-concept pendulum LiF-UPTS wall offers the following promising outcomes: (1) insignificant to no wall uplift, (2) insignificant to no wall base shear sliding, (3) reduced stress concentrations at the wall toes because contact stresses are distributed along the wall-base interface over a larger region, (4) nearly constant post-tensioning forces under high drift levels, which limits post-tensioning losses due to yielding of prestressing bars or tendons, (5) increase in energy dissipation capacity of the system through friction, and (6) decrease in the damping reduction factor and thus, reduction in the lateral displacement and force demands in pendulum LiF-UPTS walls. These research outcomes are likely to translate positively to other shear wall types, namely reinforced concrete (RC) precast pendulum UPTS walls.

Novel Panelized Roof Design for Offsite Fabrication of Residential Light-Frame Wood Homes

Novel Panelized Roof Design for Offsite Fabrication of Residential Light-Frame Wood Homes

Performance-Based Design of Posttensioned Cross-Laminated Timber and Light-Frame Wood Shear Wall Hybrid System

Performance-Based Design of Posttensioned Cross-Laminated Timber and Light-Frame Wood Shear Wall Hybrid System

Seismic performance of light wood shear wall infilled timber frame structures with openings

To study the seismic performance of wood frame structures filled with light wood shear walls, three full-size single-layer single span wooden frame structures with infill walls were designed and manufactured. The beams and columns were connected by mortise-tenon joints, and quasi-static tests were conducted on the specimens under reversed cyclic load. The failure modes and load-displacement hysteresis performance of structures with door opening infill wall, window opening infill wall, and solid infill wall were investigated. The seismic performance was analyzed using indicators such as strength, ductility, and equivalent viscous damping ratio. The failure modes of light wood frame filling walls were the tearing of sheathing panel and the failure of nail connections. The filled wall with the opening initially exhibited inclined cracks at the corner of the opening, and then they extended to the periphery. Compared with the solid filled wall, the positive and negative bearing capacity of the structure with door opening decreased, and that of the structure with window opening decreased also. Because the specimens with opening in the filled wall were more conducive to the deformation of the structure when the bearing capacity was not significantly reduced, the ductility of the specimen with door opening was the highest.

Containing Carbon: Assessing the Carbon Impacts of Repurposed Shipping-Container-Based Housing

Constructing habitable buildings from repurposed shipping containers is commonly seen as an inherently sustainable approach to building that reduces environmental impacts. While numerous studies have analyzed the relative energy performance of container-based buildings, few studies examine the relative carbon impact of high-performance container dwellings concerning other high-performance residential construction types. This paper presents a life cycle assessment that compares the material carbon emissions, operational carbon emissions, and carbon use intensity of a shipping container dwelling with an equivalent high-performance, light-frame wood dwelling across the critical time frames for meeting global climate goals. Analysis shows that the light-frame dwelling produces approximately 22% fewer carbon emissions and suggests that shipping containers do not necessarily offer an unequivocal path toward low-carbon building.

Finite element analysis of a light-frame wood panelized gable roof

This paper presents a three-dimensional (3D) finite-element analysis of a light-frame wood panelized gable roof. The study developed equivalent macro elements representing the major roof components, such as the roof panel and support wall, in the finite-element model (FEM) by utilizing analytical models of the diaphragm and shear wall of CSA 086–19. The most critical load response of the panelized roof structure was obtained by considering the governing load cases, including the partial load case for snow load. The load path analysis revealed that the panelized roof had a two-way load distribution due to the deep beam action of the support wall. The gable ends of the roof carry approximately one-third of the load. In the gravity load case, the in-plane shear governed the connection design at the eave and support wall lines. Self-tapping screws were very effective in resisting wind uplift forces due to their high withdrawal capacity. Furthermore, the deflection pattern of the ceiling joist revealed the effect of panelized construction on the load path.

Shake Table Testing and Modeling of New Zealand Light-Frame Wood Buildings

Shake Table Testing and Modeling of New Zealand Light-Frame Wood Buildings

Understanding Flexibility Effects in the Interaction of Light-Frame Wood Structures with Wave Action

Understanding Flexibility Effects in the Interaction of Light-Frame Wood Structures with Wave Action

Nonlinear modelling parameters for performance-based seismic evaluation of existing wood light-frame buildings in Canada

The mechanical behaviour of wood light-frame shearwalls is difficult to explain unless system-level performance is taken into account. Although the behaviour of wood light-frame shearwalls with wood structural panels is consistent with and represented by the behaviour of the panel to framing nail joints, comprehensive seismic evaluation guidelines for Canadian practice are currently lacking. This study presents a critical review of the available literature on the performance-based seismic evaluation of wood light-frame buildings through nonlinear analysis approach. To verify the applicability of these standards in Canada, the procedure outlined in these documents is compared to available experimental testing. Nonlinear pushover analysis is performed on two representative wood light-frame buildings in Montréal and Vancouver. Results are compared, and further discussion is provided on the adequacy of each document to Canadian practice.

The sound insulation performance of light wood frame construction floor structure based on phononic crystal theory

The development of timber structures worldwide is rapid and promising. Acoustic insulation is an important metric to measure the quality of occupants' living conditions. Therefore, to effectively improve the harm caused by low-frequency noise of the wood structure floors that people are concerned about, this paper combines the structural characteristics of the light wood frame construction floor with the phononic crystal structure with excellent sound insulation performance and carries out the impedance tube test through the simulation calculation results of COMSOL software. Impedance tube tests and field test studies were also carried out on a two-story light wood frame construction floor in Nanjing, China, to obtain a phononic crystal structure building cover with good sound insulation performance … The conclusion of the study shows that: the G8-40 phononic crystals structure obtained by COMSOL simulation matches with its impedance tube test results, and the effectiveness of its sound insulation performance has been verified by the airborne sound insulation field test; the phononic crystals structure floor has excellent sound insulation performance in the low-frequency band, which can significantly improve the user's living comfort needs and has good engineering application value.

Elevated light-frame wood residential building physical and numerical modeling of damage due to hurricane overland surge and waves

An experimental program of a 1:6 scale elevated wood frame shear-wall residential building was developed to model the damage progression of buildings subjected to increasing hurricane surge depth and wave conditions until collapse. This paper presents testing and system identification methods used to characterize structural engineering properties of the physical model that accumulated damage during hydrodynamic testing under increasing surge depth and wave heights. Methods used include (a) quasi-static lateral load-deformation testing, (b) out-of-water dynamic structural characterization testing under free vibration, ambient vibration, and forced vibration, conducted on the test specimen prior to hydrodynamic testing, (c) in-water dynamic structural characterization during hydrodynamic testing, (d) quantification of accumulated damage in hydrodynamic testing through observed changes in the laser scan point cloud data of the specimen, and (e) finite element model updating. The accumulated damage in the test specimen is correlated to changes in modal features (frequency, damping, and mode shapes) assessed using two output-only system identification (SID) methods. In addition, finite volume numerical models are used to determine detailed pressure distributions on the test specimen which are coupled with finite element (FE) models that are updated, in a phased manner, to understand the contribution of structural and nonstructural components on the modeled stiffness and strength of the physical model. Lastly, the impact of the damage on the modal features of the physical model of the building and their sensitivity to FE model assumptions are presented.

Parametric analysis of the effective flange width of mass timber composite floor panels

Mass timber composites (MTCs), where the webs are typically spaced 750–2000 mm apart, have shown potential in overcoming span limitations of conventional flat slab mass timber floors. However, fundamental research investigating the non-linear stress distribution (i.e., shear lag) in the flanges is required. While this behaviour has been simplified in design for other materials using the concept of an effective flange width (EFW), no guidance exists in international design codes for mass timber composites. In the current study, a parametric analysis was conducted on a mass timber I-beam under positive bending where the effects of web spacing, beam configuration (edge or interior placement), shear connection stiffness, concentrated versus uniform loading, web depth, web width, flange thickness, and flange modulus of elasticity on the EFW, were investigated. The reference section in the finite element model consisted of a glued-laminated timber (GLT) panel for the flanges, a glulam beam web, and a fully composite glued connection between elements.The results have shown that existing design code provisions, even those meant for light-frame wood members, over-estimate the EFW of GLT-glulam I-beams. The web spacing, shear connection stiffness, loading type, flange thickness, and web width were observed to be the most influential parameters on the EFW of GLT-glulam MTCs. Between the upper and lower boundaries of connection stiffness, a sharp increase in the EFW was observed below the point of full composite action due to the section beginning to behave as three separate elements. Although, the decrease in composite action resulted in an overall decrease in the bending stiffness of the section. For GLT-glulam MTCs, the modulus of elasticity (MOE) of the GLT flange was not observed to significantly affect the EFW for high degree of composite action configurations. A small increase in the EFW was observed when the degree of composite action was relatively low. Ultimately, the development of equations for quantifying the EFW of MTCs is key to their increased adoption but requires the expansion of the current study to include other mass timber elements, as well as experimental data investigating the most significant parameters identified herein.

Physics-based probabilistic capacity models and fragility estimates for light wood frame shear walls

Light wood frame buildings are common in the United States, and due to their prevalence, there has been significant damage to this type of building in previous earthquakes. For this building type, shear walls (typically sheathed with oriented strand board) are the main lateral force-resisting element. Probabilistic models and fragility estimates incorporating the prevailing uncertainties for shear walls are needed to make accurate predictions of the effects of future earthquakes on buildings of this type. This paper uses experimental data to develop probabilistic capacity models for the shear force and drift of light wood frame shear walls at the yield, peak, and ultimate performance levels. The proposed models are applicable to shear walls in low-rise buildings where the shear deformation is dominant. Moreover, the proposed models are applicable to walls that are similar to walls in the dataset. The probabilistic models are constructed starting from deterministic models. For the shear force, a new deterministic model is proposed. This model predicts the shear force capacity of the wall based on the capacity of individual nails. For drift, existing deterministic drift limits are used. The deterministic models are then improved by incorporating the effect of additional physical characteristics through explanatory basis functions that are shown to be significant in a probabilistic model selection procedure. Finally, fragility estimates are constructed for an example shear wall using the proposed capacity models and conditioning on the shear force and drift demands.

Unlock the myth of low-frequency footstep thumping noise in lightweight wood floors

Major occupants' complaints received in lightweight wood floors of Impact Insulation Class (IIC) above 55, are low-frequency footstep thumping noise. Lack of understanding of fundamentals and solutions motived this study. A series experiments were conducted to answer the following questions: 1) what are the frequency range of the low-frequency footstep thumping noises heard by the occupants in mass timber slab floor and in light frame wood joisted floor when the floors are impacted by the ISO tapping machine, footsteps of a person walking with shoes, and with bare foot? 2) how look like the impact sound spectrums below 50 Hz (ISO) or below 100 Hz (ASTM)? 3) Can the tapping machine excite the low-frequency noise down to the range of wood floor natural frequency around 15 Hz? 3) Can the current measurement system measure the sound signals at such low frequency range reliably? 4) can the measured spectrums of impact sound signals reveal the low-frequency impact noise issues? 5) what are the special construction details of the wood floors contributing to the low-frequency impact noise problem? 6) what are the solutions for the problem? Our experiments answered the questions. The findings and solutions will be shared in the full-length paper.

Lateral Resistance of Reinforced Light-Frame Wood Shear Walls

In light-frame timber construction, the shear wall is one of the most important components that provide resistance to lateral loads such as earthquakes or winds. According to KDS (Korea Design Standard) 42 50 10, shear walls are to be constructed using wood-based structural sheathing, with studs connected by 8d nails spaced 150 mm along the edge and 300 mm in the field. Even though small-scale residential timber building can be designed to exhibit seismic resistance using light-frame timber shear walls in accordance with KDS 42 50 10, only the abovementioned standard type of timber shear wall is available. Therefore, more types of timber shear walls composed of various materials should be tested to measure their seismic resistance, and the results should be incorporated into the future revision of KDS 42 50 10. In this study, the seismic resistance of shear walls composed of structural timber studs and wood-based structural sheathing with reinforced nailing is tested to evaluate the effects of the reinforcement. For the nailing reinforcement, shear wall specimens are constructed by applying nail spacings of 75–150 mm and 50–100 mm. For the shear wall specimens with one sheathing and reinforced nailing, the shear strengths are 1.7–2.0 times higher than that of the standard shear wall (nail spacing of 150–300 mm). The shear strength of the shear walls with sheathing on both sides is 2.0–2.7 times higher than that of the standard shear wall.

Design of stick-framed wood roofs under tornado wind loads

Light-frame wood construction comprises nearly 90% of the housing industry in Canada and the United States. The roofs of these houses can be constructed either entirely on site or using prefabricated trusses. Assembling the roof structure on site, otherwise known as stick-framing, is a framing technique with current code guidelines that are based on past practice and limited consideration of wind loads. This makes these roof structures susceptible to failure in high-speed wind events, such as tornadoes. This research proposes improved stick-framing guidelines that would work for EF-2 tornadoes. Using non-linear finite element analysis, a stick-framed roof was designed following the guidelines in the National Building Code of Canada. Non-linear links were used to model all of the connections between the members in the roof structure, with frame elements used to represent the members. Increasing wind loads were applied to the structure and the first elements of the roof that failed were improved using an iterative performance-based design approach until the performance target of resistance to EF-2 tornadoes was achieved. The failure of the roof-to-wall-connections and the lack of members used in the framing were the two main issues highlighted and addressed. Damage survey photos were used to compare failures observed in the model with failures after real tornado events, which demonstrate many similar failure modes. The research recommends the requirements to ensure stick-framed roofs can withstand EF-2 tornadoes. Most notable is an improved gable end frame, which gives the structure more roof-to-wall connections, as well as a more structurally sound frame where the loads are the highest. Other additions include struts, hurricane ties at all roof-to-wall connection locations and increased number of nails in various connections throughout the repeating inner frames. Minimum member sizes and qualities for each type of member used in the roof structure are also recommended.

Social Representations of Mass Timber and Prefabricated Light-Frame Wood Construction for Multi-Story Housing: The Vision of Users in Quebec

The increased use of wood and prefabrication are solutions that are helping to address current and future challenges in the construction sector. However, these practices are slow to become widespread due to the conservative nature of this industry. The objective of this study is to characterize the social representations of Province of Quebec (Canada) individuals with regard to these construction methods in order to determine the motivations and barriers to their use in the construction of multi-story housing. The social representations of a representative panel of the Quebec population were collected through standardized surveys. The data were analyzed using descriptive statistics. The results indicate that the use of wood in the construction of high-rise multi-story housing is not part of the representations of a majority of Quebecers. The motivations identified are the aesthetics of wood and the environmental aspect, although forestry exploitation remains an important concern for respondents. The main barriers are the safety aspect and lifespan because they tend to dominate the other themes in decision making. The results suggest that the acceptance and adoption of these construction methods by users can be improved by adapting the transfer of knowledge towards the negatively perceived themes and the identified social groups.

Effect of thermal bridge in light-frame wood wall

The presence of thermal bridges in a wall increases local heat conduction of the building envelope, resulting in a decrease in the wall’s average thermal resistance. Simultaneously, the internal surface temperature of thermal bridge is lower than that of the surrounding areas and shows a tendency of condensation. Therefore, it is necessary to employ thermal bridges in the stage of construction design. In the research, a two-dimensional steady-state numerical simulation was performed targeting thermal bridges with light-frame wood wall. Meanwhile, the heat bridge effect was simulated under different circumstances by changing the types of insulation and cladding materials, the number of the studs, and the framing factor. The results showed that the linear heat transfer coefficient increased linearly as the studs and framing factor rose. After the test was validated, the relative error rate between the simulated correction coefficients and the experimentally derived correction coefficients was 11.4%, indicating that the correction coefficients can be simulated.

Novel Apex Connection for Light Wood Frame Panelized Roof.

Panelized fabrication of light-frame wood buildings has higher productivity than the traditional stick-built method. However, the roof production process is not very efficient due to the structural system and construction method. This study proposes a novel apex connection that allows for a folding mechanism in a panelized light wood frame roof system. Proof of concept of the proposed connection assembly is presented by a 3D printout of the developed connection. Following the steel design code and timber code, the initial estimation of different parameters, such as the pinhole diameter and number screws, were established. A detailed finite element analysis (FEA) was performed to determine the connection strength requirement for different load case scenarios. The results of the FEA and 3D printout of the assembly show that the proposed connection can provide the required folding mechanism before roof installation and can withstand the load in the unfolding state at service.