Light-frame Wood Research Articles

Testing and analytical modelling of intermediate gypsum wallboard in wood shear wall sheathing to framing connections

Light frame wood shear walls resist lateral loads primarily through the individual nailed connections between the sheathing and framing. The most common arrangement for such shear walls is to have sheathing on one side and gypsum board on the other. In various situations it can be desirable to increase the capacity of this type of walls by fastening a layer of sheathing overtop of the drywall. This study considered the effect that an intermediate layer of gypsum has on the strength of nailed connections in shear walls, while maintaining code-defined minimum nail penetrations. Results show that intermediate gypsum placed between the sheathing and framing resulted in significantly reduced capacity and stiffness. Analytical modelling showed good correlation with experimental results. The implications of the experimental testing and modelling are that code provisions allowing the use of intermediate gypsum wallboard should not be relied upon.

Hybrid System of Unbonded Post-Tensioned CLT Panels and Light-Frame Wood Shear Walls

Cross-laminated timber (CLT) is a relatively new type of massive timber system that has shown to possess excellent mechanical properties and structural behavior in building construction. When post-tensioned with high-strength tendons, CLT panels perform well under cyclic loadings because of two key characteristics: their rocking behavior and self-centering capacity. Although post-tensioned rocking CLT panels can carry heavy gravity loads, resist lateral loads, and self-center after a seismic event, they are heavy and form a pinched hysteresis, thereby limiting energy dissipation. Conversely, conventional light-frame wood shear walls (LiFS) provide a large amount of energy dissipation from fastener slip and, as their name implies, are lightweight, thereby reducing inertial forces during earthquakes. The combination of these different lateral behaviors can help improve the performance of buildings during strong ground shaking, but issues of deformation compatibility exist. This study presents the results of a numerical study to examine the behavior of post-tensioned CLT walls under cyclic loadings. A well-known 10-parameter model was applied to simulate the performance of a CLT-LiFS hybrid system. The post-tensioned CLT wall model was designed on the basis of a modified monolithic beam analogy that was originally developed for precast concrete-jointed ductile connections. Several tests on post-tensioned CLT panels and hybrid walls were implemented at the Large Scale Structural Lab at the University of Alabama to validate the numerical model, and the results showed very good agreement with the numerical model. Finally, incremental dynamic analysis on system level models was compared with conventional light-frame wood system models.

Testing and Modeling of Wood–Masonry Hybrid Wall Assembly

AbstractReinforced concrete or masonry cores commonly exist in multistory light wood frame buildings (LWFBs) as elevator shafts and stairwells. These cores are often not accounted for in structural design as part of the lateral load resisting system in combination with the light wood frame subsystem due to the uncertainty regarding material compatibility. In this paper, the interaction between the wood frame and masonry walls in a hybrid lateral load resisting wall system was investigated using a two-dimensional numerical model. Two two-story hybrid wood-masonry walls as well as individual wall subsystems and connections were tested experimentally under reversed cyclic loading to provide confidence in the ability of the numerical model to predict the lateral load response of the hybrid wall systems. From the experimental results it was noted that the bolted connections first failed when the load was applied to the wood frame in the hybrid system, while masonry walls first failed when the load was applied ...

Assessing Modeling Complexities on the Seismic Performance of an Instrumented Short-Period Hospital

AbstractLow-rise, short-period buildings dominate the construction in the United States including residential, recreational, and critical, including hospital, facilities. Previous analytical studies have indicated that these structures behave poorly under seismic excitation compared to buildings with longer fundamental periods; however, such trend has not been observed in previous earthquake events. In this paper, a case study is considered to better evaluate the dynamic response of short-period light-frame wood buildings and help identify the modeling parameters and level of complexity required to accurately capture their dynamic response. For this purpose, a portion of the Twin Cities Community Hospital, located in Templeton, California (called herein the Templeton Hospital), was considered. This one-story light-frame wood building with a large roof diaphragm layout did not suffer any structural damage during the 2003 San Simeon earthquake despite being subjected to intense ground shaking. The Templeton...

Dream or Dilemma: The Unconscious Construction of the Modern House

Over time, balloon-frame construction has been debased, promoted, and then submerged into a collective cultural unconscious. In the nineteenth-century, diverse methods of house construction gradually combined into a single way of building. This created a “massive system”—a type of practice that technology historian Thomas Hughes describes as ubiquitous and resistant to change—including every point of material production to every scale of application, from forestry to urban design, including many unsustainable practices. How will things change? Either the system will adopt token improvements or there will be radical change, perhaps returning our ways of building to more diverse practices of construction. This article revisits material presented in this journal nearly twenty years ago, analyzing new data and introducing concepts of knowledge conversion, hybridity, and the social construction of technology to develop a history of wood framing that is rich and contingent, and that reveals, discusses, and elaborates implications of our indifferent use of light-wood frame construction.

실측데이터를 이용한 에너지제로주택의 연간 에너지성능평가

Purpose: In this study, we evaluate the annual energy performance of the detached house which was designed with the aim of zero energy. Method: The experimental house which was constructed in Gonju Chungnam in 2013, is the single family detached house of light weight wood frame with <TEX>$100m^2$</TEX> of heating area. Thermal transmittance of roof (by ISO 10211) and building external walls are designed as <TEX>$0.10W/m^2K$</TEX> and <TEX>$0.14W/m^2$</TEX> respectively and low-e coating vacuum window glazing with PVC frame was installed. Also grid connected PV system and natural-circulation solar water heater was applied and 6kWp capacity of photovoltaic module was installed in pitched roof and <TEX>$5m^2$</TEX> of solar collector in vertical wall facing the south. We analyzed the 2014 annual data of the detached house in which residents were actually living, measured though web-based remote monitoring system. Result: First, as a result, total annual energy consumption and energy production (PV generation and solar hot water) are 7,919kWh and 7,689kWh respectively and the rate of energy independence is 97.1% which is almost close to the zero energy. Second, plug load and hot water of energy consumption by category showed the highest numbers each with 33% and 31%, with following space heating 24%, electric cooker 8%, lighting 3% in order. Hot water supply is relatively higher than space heating because high insulation makes it decreased.

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.

Joint Earthquake–Snow Hazard Characterization and Fragility Analysis of Wood-Frame Structures

AbstractThis paper presents a study to statistically characterize the joint earthquake–snow hazard and subsequently develop maximum interstory drift fragility curves for a series of archetype engineered light-frame wood structures. Of particular focus are structures built in moderate-seismic, heavy-snow regions. For these light-frame structures, the additional seismic mass due to the presence of roof snow may be significant. Although load standards such as ASCE 7 provide guidance on combining design loads when considering life safety (e.g., flexural and shear limit states), guidance is not yet available for other performance levels (limit states with specified nonexceedance probabilities), performance (rather than safety) based limit states or damage indicators (e.g., maximum interstory drift), and hazard levels other than those implied in life safety design (e.g., 2%/50 years). All of these are expected to become more relevant as performance-based design procedures continue to evolve and gain acceptance...

Nailed Connection Behavior in Light-Frame Wood Shear Walls with an Intermediate Layer of Insulation

AbstractThe shear strength and stiffness of light-frame wood shear walls is highly dependent on the behavior of their individual nailed connections. Eighty-four nailed connection specimens were tested under shear loading to determine the effect of including rigid insulation as an intermediate material between the sheathing and framing elements in a light-frame wood shear wall. Each specimen contained common 10d or 16d nails, 15.9 mm oriented strandboard sheathing, spruce-pine-fir lumber, and rigid insulation in varied thicknesses between 0 and 38.1 mm. From the load-deformation results, maximum load, yield load, and stiffness were assessed using curve-fitting and yield-point determination methods. The results indicate that, as the insulation thickness increases, the connection strength and stiffness both exhibit a steep reduction. In addition, nonlinear two-dimensional (2D) finite-element models of the same nailed connections were developed. These models showed good correlation with experimental data and ...

Experimental and Statistical Evaluation of the Size Effect on the Bending Strength of Dimension Lumber of Northeast China Larch.

This study investigated the size effect on the bending strength (modulus of rupture—MOR) of dimension lumber of Northeast China larch (Larix gmelinii); providing a basis for the further application in light wood frame construction. Experimental and statistical evaluations were conducted on the bending strength. A total of 2409 full-size dimension lumber samples were tested by static bending tests; which included three different sizes: 2 × 3; 2 × 4; and 2 × 6. Results indicate that the size has a significant effect on the MOR. Both the chi-square (χ2) and Kolmogorov-Smirnov (K-S) test results show that the lognormal distribution generally fits to the MOR better than to the normal distribution. Additionally; the effects of partial safety factor (γR) and live-to-dead load ratio (ρ) were studied by reliability analysis. Reliability analysis results indicate that the reliability index increases nonlinearly with the decrease of γR and the rise of ρ. Finally; the design value of bending strength and its adjusting factor of size effect of 2 × 3; 2 × 4; and 2 × 6 larch dimension lumber were obtained according to the Chinese National Standards’ requirements of the reliability index.

Energy Consumption Analysis of Multistory Cross-Laminated Timber Residential Buildings: A Comparative Study

AbstractCross laminated timber (CLT) is a new panelized mass timber product that is suitable for building tall wood buildings (higher than eight stories) because of its structural robustness and superior fire resistance as compared with traditional light-framed wood systems. A number of tall CLT buildings have been constructed around the world in the past decade, and taller projects are being planned. The energy efficiency of this emerging building type was evaluated numerically in this comparative study with the use of a building energy simulation program. A 10-story multiunit residential building model constructed using CLT was simulated and compared with a light-frame metal construction model with the same floor plan. A sensitivity analysis was also conducted to study the impact of different weather profiles, building types, and internal load conditions on building energy consumption performance. It was concluded that CLT generally provides significant improvement on heating energy efficiency as a heav...

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 she...

Comparisons of impact and airborne sound isolation among cross laminated timber, heavy-timber mill buildings, concrete, and light weight wood frame floor/ceiling assemblies

While laboratory measurements of the Impact Sound Pressure Level (ISPL) and Transmission Loss (TL) of concrete and lightweight wood-frame constructions are well understood, not much laboratory research has been conducted into the acoustical performance of CLT and heavy-timber mill buildings. Recent work on the performance of these wood based floor/ceilings has been presented at other conferences. This paper will review that previously published research for both the bare assemblies and assemblies that include resilient elements. These resilient elements include recycled rubber floor underlayment and sound isolation clip systems. This paper will then compare the performance of these assemblies to each other and to more common concrete and lightweight wood frame floor/ceiling assemblies. The analysis will also include the comparable strengths and weaknesses of each structural system along with the effectiveness of the various acoustical isolation techniques and their effectiveness on each of various floor ceiling assembly. It will be shown that the acoustical isolation techniques will perform differently on the various floor/ceiling assemblies.

Effects of salinity on the nail-holding power of dimension lumber used in light-frame wood building

We studied the effect of salinity on nail-holding power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail-holding power of the wood specimens both declined, but the differences between salinity treatments were not significant. However, compared to the surface and side nail-holding power, the power on the edge was generally less and the difference was not obvious in different salt concentrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.

Investigations of Structural Damage Caused by the Fertilizer Plant Explosion at West, Texas. II: Ground Shock

An explosion occurred at a fertilizer plant in the town of West, Texas, on Wednesday, April 17, 2013, devastating a populated neighborhood. A total of 15 people were killed, and approximately 160 more people were injured. Approximately 150 buildings were damaged in the explosion, and the damage to affected homes and businesses was estimated to exceed $100 million. This research documents the building damages caused by the unprecedented explosion and evaluates the technical information for the explosion. The Part I paper of this research focused on the building damage documentation and air-blast incident overpressure calculations. As a companion paper, this manuscript (Part II) primarily focuses on the study of blast-induced ground-shock effects. The ground shock–induced building damages and ground vibration peak particle velocities (PPVs) are analyzed. With a combined consideration of these two types of blast loadings, the air-blast incident overpressures and ground shocks, the field investigated damages caused by the West Fertilizer plant explosion are explained in a more precise manner. The air-blast incident overpressure is identified as the dominant factor for the damages of both wood light-frame buildings and engineering buildings. The ground shock is the secondary factor but is still important. Concluding the research outcomes in the Part I and Part II papers, this study proposes a four-scale blast-induced damage severity evaluation system, demonstrates efficient blast-loading calculation methods for both the air-blast incident overpressure and ground-shock PPV, and provides a correlation between the blast loadings and the blast-induced damages for the West Fertilizer plant explosion case. The documentation and analyses that resulted from this research could serve as a good case study for better understanding of the blast loadings and building structural responses.

The Study of Structure Supporting System in Log Cabins

Modern timber buildings are more and more popular with their characteristics of green, environmental protection, low carbon. According to their structure, they are divided into light wood frame construction, sawn and log timber structures, glued laminated timber structures, log cabins. This paper analyzes the structure supporting structural system of log cabins, from material requirements, structural design to production process, supplemented by practical case to demonstration, to explore the design method of log cabin’s structure supporting system.

Testing and modelling of shearwalls studded with small-diameter round timber under cyclic lateral load

As a forestry by-product mainly from thinning of the artificial forests, small-diameter round timber is not suitable for structural members due to its low quality. For use in structural applications, a kind of shearwall utilising small-diameter round timber in the form of built-up studs was developed. To investigate the structural behaviour of the shearwalls, 15 full size specimens with different configurations were manufactured and tested under cyclic lateral loading. The failure modes of the shearwalls were observed and the hysteresis curves obtained. The lateral resistance, stiffness and displacement capacity were evaluated. An FE model of the shearwalls was then developed using ABAQUS, and the structural behaviour simulated. FE modelling and testing of the shearwalls correlated closely. The results of this study showed that the developed shearwalls performed quite well under cyclic lateral load, with sufficient lateral resistance for use in light wood frame construction.

An estimate of tornado loads on a wood-frame building using database-assisted design methodology

Thunderstorms and related tornadoes caused over $25 billion in damages in 2011, the majority of which occurred to residential structures. Over 13,000 homes were damaged or destroyed by two tornadoes in Tuscaloosa and Joplin alone. Such substantial losses should not be surprising because as yet, no design guidelines exist for tornadoes, and with the current wind provisions in accepted building codes there is limited capacity in any wood-framed structure to withstand tornado loads. The objective of this current study is to develop appropriate design structural reactions for light-framed wood structures that is subjected to tornado loads. The study uses tornado simulator-generated surface pressure data from a fully sealed 1:100 scale gable roof model, experimentally-determined structural influence functions, and a modified database-assisted design (DAD) methodology to predict the reactions. Forces are established at structural connections for a tornado with peak wind speeds of 60.3m/s (135mph). Results are compared against structural reactions due to straightline winds with an identical peak wind speed, as determined using ASCE 7–10 wind pressure distributions. It is shown that for a sealed building (i.e., no pressure equalization between the building interior and exterior), the peak shear forces under tornado loads are 1.8 times as strong for roof-to-wall connections and twice as strong for wall-to-foundation connections, as compared to those from ASCE 7–10 wind loads. The peak vertical loads on connections are even higher, nearly four times as high for the roof-to-wall and wall-to-foundation connections. Nearly 60% of the peak loads can be attributed to the assumption of a fully sealed building mode, which results in the full effect of the pressure drop within the vortex being experienced on all surfaces of the building.

Finite-element modeling of a light-framed wood roof structure

Past high speed wind events have exposed the vulnerability of the roof systems of existing light-framed wood structures to uplift loading, contributing greatly to economic and human loss. This paper further investigates the behaviour of light-framed wood structures under the uplift loading of a realistic pressure distribution. A three-dimensional finite-element model is first developed to capture the behaviour of a recently completed full-scale experiment. After describing the components used to develop the numerical model, a comparison between the numerical prediction and experimental results in terms of the deflected shape at the roof-to-wall connections is presented to gain confidence in the numerical model. The model is then used to analyze the behaviour of the truss system under realistic and equivalent uniform pressure distributions and to perform an assessment of the use of the tributary area method to calculate the withdrawal force acting on the roof-to-wall connections.

Special Issue on Performance of Timber and Hybrid Structures

Special Issue on Performance of Timber and Hybrid Structures