Wood-frame Buildings Research Articles

Wind Performance Enhancement Strategies for Residential Wood-Frame Buildings

Extreme winds such as tornadoes and hurricanes are relatively common natural hazards in the United States and can result in fatalities as well as damaging physical and socioeconomic infrastructure. Buildings are a critical sector within the built environment of a community and studying their performance under natural hazards is a major step for the risk and resilience assessment of a community. More than 80% of the total building stock in the United States and more than 90% of the residential buildings in North America are wood-frame construction; a construction type that is vulnerable to wind damage because they are light and typically are not engineered, only prescriptive in their design. Performance enhancement strategies for wood-frame residential buildings were investigated in this study by exploring combinations of roof coverings, roof sheathing nailing patterns, and roof-to-wall connection types. In this regard, a total of nine construction product combinations were considered. Further, recent changes to the wind standards were also explored. Specifically, the damage fragilities of five wood-frame building archetypes are considered for four damage states defined based on the performance of the building envelope, including roof coverings, doors and windows, roof sheathing, and roof-to-wall connections. The fragility curves are explained at the component level and then the building level for one archetype as an example, and the building fragility parameters are provided for all archetypes and for all construction product combinations. Comparison between fragilities developed using the last two versions of the wind standards are also presented. Then, an existing approach that amplifies the wind pressures in the wind standards to represent a tornado load is also compared. The fragility curves provided in this study can be used to represent residential buildings within a community for risk or resilience assessment/mitigation under hurricane or tornado loading.

Finite-element modeling framework for predicting realistic responses of light-frame low-rise buildings under wind loads

Low-rise wood frame buildings are one of the most vulnerable structures that are often damaged in windstorms. On the other hand, numerically modeling the structural behavior of wood frame buildings poses significant challenges. This paper presents a computational modeling methodology that can help determine the realistic load paths and load sharing for light-frame low-rise buildings under wind loadings throughout the linear to the nonlinear range. A three-dimensional finite-element (FE) model is developed to capture the behavior of a building under wind loading, a large-scale model of which was tested at the Wall of Wind (WOW) Experimental Facility (EF) at Florida International University to provide experimental results for the validation of the FE modeling. This comprehensive numerical model can accommodate various materials and structural connections with mechanics-based load-deformation characteristics such as sheathing nails and framing-to-framing connections, so as to be capable of predicting the performance of the components and connections that are difficult to model in general but are the most vulnerable parts of a low-rise structure as witnessed during past hurricanes. The predicted structural responses of the computational framework showed reasonable agreement when compared to the experimental measurements in terms of the deflection at roof sheathings and roof-to-wall connections (RTWCs). This validated framework is then used to analyze different modeling effects. Different ways to represent the RTWCs and foundation fasteners are compared, which determines the boundary conditions of the roof assembly and full building simulations, respectively. The modeling of wall stud connections is discussed to fill in the corresponding gaps in the past research. A controversial issue that whether the effect of the rotational capacities of sheathing nails can be ignored or not is also discussed.

BIM-based automated design and planning for boarding of light-frame residential buildings

Abstract Building information modelling technology provides a game-changing solution to address the challenges encountered in the AEC industry. However, this technology currently is not sufficient to fulfil the needs of construction practitioners in terms of proactive design and planning for boarding of light-frame residential buildings. This is partially due to the fact that boarding design and planning requires trades' know-how and substantial manual effort in developing the building information models. Current manual and ad hoc decision making for boarding of light-frame buildings leads to the generation of a significant amount of material waste. This research thus proposes a rule-based automated building information model (BIM) approach for designing boarding layout and planning material sheet cutting, resulting in practically feasible solutions with minimal material waste. In this research, object-based computer-processable layout design rules are comprehensively formalised based on trades' know-how. On this basis, rule-based design algorithms are further developed and integrated with mathematical algorithms in order to automatically generate design and planning alternatives while minimising material waste. Rich information in the BIM is leveraged to automate the rule-based boarding design and planning. A prototype system is developed based on Autodesk Revit via Application Programming Interface. A typical wood-framed residential building is used as a case study to test the developed prototype system. The results show the proposed approach successfully preserves the know-how of senior trades people while also minimising material waste in automating the boarding design and planning.

Experimental and Numerical Analysis of Wood-Framed Buildings

Paper presents current technologies and building structure used in wood-framed multistory buildings and also refers to calculation methods of strains and stresses. Structure of these buildings is recently based on modular technology. Elements in the form of module are constructed in the industrial plant and then delivered to the site for assembling. The wood-framed building structure undergoes significant deformations relevant to changes of moisture content in material and resulted from load acting perpendicular to the grain direction in wood. In four story building the vertical displacement of the top floor has been estimated to over 80 mm. FEM model with application of the shell elements in description of posts, beams and sheathing and applying the beam finite elements in description of linking fasteners is used in stress evaluation in structure. The model permits for precise analysis of stresses in overloaded parts of structure distinguishing to the other simplified analytical models of analyses. Analytical model leads to determination of stresses under typical exploitation standard loadings and in result of non-typical loadings arising at the time of module handling within assembling.

Tornado community-level spatial damage prediction including pressure deficit modeling

Based on the observation of damage from past tornadoes, tornado intensity is frequently the highest at the center and gradually decreases outward, which is consistent with a Rankine vortex model. In this study, the Rankine vortex model was applied to model the pressure deficit resulting from a tornado, and then combined with pressures resulting from wind velocity to develop fragility surfaces for buildings representative of the typical residential building stock in a community. In the absence of data, an additional coefficient is used herein to consider different amount of pressure deficit participating in wind loads on buildings to enable community resilience studies. However, it is duly noted that at the individual building level the internal pressure coefficient used in ASCE-7 should be adjusted based on data to be consistent with current wind engineering methods in the United States. Moreover, a scenario tornado path was modeled based on historical statistics of U.S. tornadoes over almost four decades using mean values, and spatial damage to a cluster of wood-frame buildings representative of a residential subdivision of a community was investigated. The methodology presented herein can provide damage information spatially over a community which is a key to studying resilience at the community-level.

Effective Model for Analysis of Wood-Framed Timber Structures

AbstractThis paper presents new procedure modeling based on finite element method analysis of wood-framed timber structures. The fasteners linking boards of sheathing with the timber frame both modeled applying shell finite element, with individual material parameters, remain the main objective of this manuscript. Material parameters are obtained from experimental tests and numerical identification. The main objective of the paper is the elaboration of the numerical model with high precision of mapping, and, at the same time, diminishing the number of the unknown simplifying the process of the modeling of timber structures. The new presented method leads to a simplification of analysis of multistory wood-framed multifamily building structures.

Tests on full-scale and static analysis models of the wood-framed building stucture horizontaly loaded

This paper focuses on development of the high energy saving timber building and ecological technology protecting environment in civil engineering. Wood framed with sheathing, large panel structures became more popular building constructions in Poland last decade. Experimental tests and numerical analysis of panels and complete wood framed building have been taken into account. Typical two-story residential building was selected for test. Test of three dimensional (3D) whole building was conducted on the base of experimental investigations results of large panel similar to those used in building structure. Also adequate tests of materials and connections were accompanying of the whole structure investigations. Obtained results were adopted in numerical models elaborated for wall and floor panels and in 3D model of whole building. Load -displacements characteristics were acquired from tests and numerical models. The displacements computed from 3D numerical model were 10–20% higher than from experiment. Experimentally ob-tained lower displacements than those from analytical analysis are resulted from higher stiffness of wall system due to diaphragms interconnections, their common interaction and three-dimensional character of building structure. Presented research analyzed method of computation of internal forces in building as well in the range of engineering methods in the form of rigid beam scheme up to the advanced methods using 3D spatial model adopting FEM.

Mass Timber Rocking Panel Retrofit of a Four-Story Soft-Story Building with Full-Scale Shake Table Validation

Soft-story wood-frame buildings have been recognized as a disaster preparedness problem for decades. There are tens of thousands of these multi-family three- and four-story structures throughout California and other cities in the United States. The majority were constructed between 1920 and 1970, with many being prevalent in the San Francisco Bay Area in California. The NEES-Soft project was a five-university multi-industry effort that culminated in a series of full-scale soft-story wood-frame building tests to validate retrofit philosophies proposed by (1) the Federal Emergency Management Agency (FEMA) P-807 guidelines and (2) a performance-based seismic retrofit (PBSR) approach developed within the project. Four different retrofit designs were developed and validated at full-scale, each with specified performance objectives, which were typically not the same. This paper focuses on the retrofit design using cross laminated timber (CLT) rocking panels and presents the experimental results of the full-scale shake table test of a four-story 370 m2 (4000 ft2) soft-story test building with that FEMA P-807 focused retrofit in place. The building was subjected to the 1989 Loma Prieta and 1992 Cape Mendocino ground motions scaled to 5% damped spectral accelerations ranging from 0.2 to 0.9 g.

Hurricane loss estimation in wood-frame buildings using Bayesian model updating: Assessing uncertainty in fragility and reliability analyses

This paper proposes a Bayesian model updating method for quantification of uncertainty in the analytical capacity predictions of roof-to-wall connections of wooden structures. The ultimate goals are to construct fragility models for various mitigation options accounting for uncertainties due to model discrepancy and experimental error and to determine the most cost-effective option under a potential hurricane in terms of aggregate loss estimates based on total probability of failure. The proposed approach is applied to both hurricane-clips (mitigated specimen) and toenails (unmitigated specimen) and the exceedance probability of different aggregated loss scenarios are found using both the proposed method and the existing lognormal approach. The advantage of the two-stage Bayesian model is that it provides the uncertainty bound on the exceedance probability which gives a measure of the factors unaccounted for in the capacity estimation process.

Current Directions in Development of Modern Wood-framed Houses

Realization of the wood-framed buildings in Europe and in the Nord America are discussed in the introduction to presented paper. Current directions in realizations of single family, multifamily and the other purpose the wood-framed buildings are outlined in paper. Paper describes formation of structural building elements industrially constructed and then dispatched to site. Next part of the paper presents analytical models applied in analysis of internal forces in structure. Numerical model is based on the assumptions of the finite element method. Paper contains exampled application of numerical model in 3D analysis of modular element built-in as the lower segment of multistorey and multifamily building. Summary and conclusions are ending the paper.

Post-Earthquake Damage Inspection of Wood-Frame Buildings by a Polarimetric GB-SAR System

Structural damage inspection after an earthquake is essential for safety assessment of the affected wood-frame buildings and for making knowledgeable decision regarding their repair, renovation, or replacement. We present a polarimetric radar system for sensing the concealed wood-frames damaged by earthquakes. This system employs an antenna array consisting of four linearly polarized Vivaldi antennas recording full-polarimetric radar echoes in an ultra-wideband ranging from 1 to 20 GHz. The detailed design of the system and the signal processing algorithms for high-resolution 3D imaging are introduced. We conducted a number of surveys on damaged wooden wall specimens in laboratory. The experiment results indicate that the high-frequency radar waves can penetrate the wooden walls. Deformations of wooden structures (about 2 cm displacement) inside the wall, as well as the concealed small metal nails (about 3 mm in diameter and less than 2 cm in length) and bolts can be clearly imaged. The shape and orientation of the wooden members have shown a great sensitivity to the radar polarization. It is concluded that radar polarimetry can provide much richer information on the condition of concealed building structures than the conventional single-polarization subsurface penetrating radar.

Life risks due to fire in mid- and high-rise, combustible and non-combustible residential buildings

CUrisk, a comprehensive model available for assessing fire risks in buildings, is used to assess and compare the life risks due to fires in mid-rise and high-rise residential buildings of non-combustible, light wood frame, and cross laminated timber constructions. The non-combustible buildings and some of the light wood frame buildings are explicitly code compliant designs, while some of the light wood frame buildings and the cross laminated timber buildings are alternative solutions. The computation results show that, the life risks of the simulated buildings are very low due to the installation of sprinkler systems and the risks are limited to the occupants in the rooms of fire origin. The effects of building area and storeys on life risk are minor. However, the area of the room of fire origin affects life risk significantly. Properly designed and protected combustible buildings do not impose higher life risk to occupants than non-combustible buildings. Life safety performance of buildings depends more on the design solutions as a whole rather than the selection of the construction type.

The sociotechnical regime and Swedish contractor perceptions of structural frames

To deepen the understanding of the sociotechnical regime that directs the selection of structural frames in multifamily buildings in Sweden, we study the perceptions of contractor representatives. Contract managers (CMs) employed at contractor firms were interviewed regarding their role, the selection of the structural frame and how they perceived different options. The results show that CMs largely influence the selection of the structural frame in multifamily buildings, which are guided by the established concrete-based sociotechnical regime. The regime is maintained through cognitive rules regarding structural frame options and the alignment of skills of construction professionals. Because of their influence and their investments in the skills of construction workers, CMs make important contributions to maintain the regime and the concrete path dependency. Furthermore, the regime varies in strength in different locations. Some locations carry a strong norm to cast concrete frames on site. This makes it more difficult to deviate from the established practice. In other locations, wood-promoting initiatives have changed the cognitive rules associated with the regime. Nonetheless, the sociotechnical regime makes the selection of concrete structural frames beneficial. This prevents wood-framed multifamily buildings from entering common usage, even though such buildings can contribute to mitigating climate change.

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 ...

Sensitivity analysis of probabilistic seismic behaviour of wood frame buildings

This paper examines the contribution of three sources of uncertainties to probabilistic seismic behaviour of wood frame buildings, including ground motions, intensity and seismic mass. This sensitivity analysis is performed using three methods, including the traditional method based on the conditional distributions of ground motions at given intensity measures, a method using the summation of conditional distributions at given ground motion records, and the Monte Carlo simulation. FEMA P-695 ground motions and its scaling methods are used in the analysis. Two archetype buildings are used in the sensitivity analysis, including a two-storey building and a four-storey building. The results of these analyses indicate that using data-fitting techniques to obtain probability distributions may cause some errors. Linear interpolation combined with data-fitting technique may be employed to improve the accuracy of the calculated exceeding probability. The procedures can be used to quantify the risk of wood frame buildings in seismic events and to calibrate seismic design provisions towards design code improvement.

Damage estimation of roof panels considering wind loading correlation

Roof panels on light wood-frame building roofs are very vulnerable to high winds. Once the roof is breached, a series of consequences will occur, including the rainwater penetration and dangerous projectiles originating from blown panels. Damage mitigation and risk management require a better estimation of wind-induced damage on roof panels. In this study, a data-based wind damage estimation method considering wind loading correlation is developed for roof panels. This method is composed of three steps. Firstly, the peak uplift force on roof panels is estimated by Hermite polynomial model-based translation process method. Then the correlation of peak uplift forces is incorporated by Nataf transformation. Finally, the failure probability of a single panel and the damage ratio of panels on the whole roof are estimated by either the numerical method or Monte Carlo simulation. A numerical example demonstrates the effectiveness of the proposed method. The importance of the correlation of wind loading on the wind damage estimation for roof panels is highlighted. Note that the proposed method can be extended to damage estimation for other roof components such as shingles when the wind loading correlation is included.

Closure to “Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. II: Shake Table Test Results” by John W. van de Lindt, Pouria Bahmani, Gary Mochizuki, Steven E. Pryor, Mikhail Gershfeld, Jingjing Tian, Michael D. Symans, and Douglas Rammer

Closure to “Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. II: Shake Table Test Results” by John W. van de Lindt, Pouria Bahmani, Gary Mochizuki, Steven E. Pryor, Mikhail Gershfeld, Jingjing Tian, Michael D. Symans, and Douglas Rammer

Discussion of “Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. I: Building Design, Retrofit Methodology, and Numerical Validation” by Pouria Bahmani, John W. van de Lindt, Mikhail Gershfeld, Gary L. Mochizuki, Steven E. Pryor, and Douglas Rammer

Discussion of “Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. I: Building Design, Retrofit Methodology, and Numerical Validation” by Pouria Bahmani, John W. van de Lindt, Mikhail Gershfeld, Gary L. Mochizuki, Steven E. Pryor, and Douglas Rammer

Closure to “Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. I: Building Design, Retrofit Methodology, and Numerical Validation” by Pouria Bahmani, John W. van de Lindt, Mikhail Gershfeld, Gary L. Mochizuki, Steven E. Pryor, and Douglas Rammer

Closure to “Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. I: Building Design, Retrofit Methodology, and Numerical Validation” by Pouria Bahmani, John W. van de Lindt, Mikhail Gershfeld, Gary L. Mochizuki, Steven E. Pryor, and Douglas Rammer

Evolution of Predicted Seismic Performance for Wood-Frame Buildings

AbstractFollowing natural disasters, major changes are often adopted in design codes, provisions, and guidelines that highlight existing or perceived deficiencies in design code calibration and sometimes design philosophy. The work presented herein chronicles the evolution of seismic design for wood-frame buildings from 1959 through current state-of-the-art methodologies available as of 2015. Included in the approaches in this study were two performance-based seismic retrofit levels and a soft-story-only retrofit design that followed a recent guideline published by FEMA. A brief background on the historical significance and major changes adopted in each provision or guideline is provided. Building performance was quantified and compared using multirecord fragilities for a range of wood-frame building types for the historical seismic provisions, demonstrating that the predicted seismic performance of wood-frame buildings has improved over time. It was also demonstrated that performance-based seismic retrof...