Wood-frame Buildings Research Articles

Seismic performance factors for timber buildings with woodframe shear walls

Seismic performance factors are an engineering tool to estimate force and displacement demands on structures designed through linear methods of analysis. In Chile, the NCh433 standard provides the regulations, requirements, and factors for seismic design of several structural typologies and systems. However, when it comes to wood frame structures, previous research has found that the NCh433 provisions are highly restrictive and result in over-conservative designs. Therefore, this paper presents an experimental and numerical investigation aimed at proposing new, less restrictive seismic performance factors for wood frame buildings. Following the FEMA P-695 guidelines and a novel ground motion set for subduction zones, this research embraced: (1) testing of several full-scale specimens, (2) developing of detailed and simplified numerical models, and (3) analyzing the seismic performance of a comprehensive set of structural archetypes. 201 buildings were analyzed and results showed that changing the current NCh433 performance factors from R = 5.5 & Δmax = 0.002 to R = 6.5 & Δmax = 0.004 decreases the average collapse ratio of wood frame structures by 13.3% but keeps the collapse probability below 20% for all the archetypes under study. Besides, it improves the cost-effectiveness of the buildings and enhances their competitiveness when compared to other materials, since savings of 40.4% in nailing, 15.9% in OSB panels, and 7.3% in timber studs were found for a 5-story building case study. Further analyses showed that the buildings designed with the new factors reached the “enhanced performance objective” as defined by the ASCE 41–17 standard, guaranteeing neglectable structural and non-structural damage under highly recurring seismic events. Finally, dynamic analyses revealed that the minimum base shear requirement Cmin of the NCh433 standard is somewhat restrictive for soil classes A, B, and C, leading to conservative results compared to archetypes where the Cmin requirement did not control the structural design.

Application of MEPLWF: method performance evaluation of the Light Wood Frame construction system

Abstract One of the 17 Sustainable Development Goals (SDG) set out in this agenda, objective 11 is related to the search for more sustainable cities and communities. This study wishes to contribute in this effort, presenting a method application to evaluate the performance of light wood frame buildings in Brazil. The structure of the method used, named MEPLWF, is based on five dimensions, which involve criteria and sub-criteria that analyse technical, social, environmental and economic requirements to evaluate buildings. It allows the examination of the operating results of buildings and the discovery of performance-related problems. The proposed method was applied in a real case study in southern Brazil, during the pre-occupation phase of the building. As a result, the performance identified in the building was 94%, which is a high performance. The application of the method in this case study diagnosed points that should be reviewed by the construction company, such as items related to fire protection and safety, flexibility and adaptability of the building system, environmental plan, energy efficiency and Costs.

Design of computer experiments for developing seismic surrogate models

Surrogate models are growing in popularity within the earthquake engineering community because of their ability to increase the efficiency of computationally intensive tasks. This article examines the design of computer experiments (DoCE) for the purpose of developing seismic surrogate models. Two categories of DoCE approaches are discussed while underscoring the benefits and drawbacks of specific methods. Further insight is provided through an illustrative case study that develops surrogate models to predict the median collapse capacity and expected annual losses in single-family woodframe buildings with cripple walls. The implications of the chosen DoCE method on the predictive performance and efficiency (in terms of the required number of explicit simulations) of the associated surrogate models are closely examined. The results show that both factorial and Latin hypercube designs [Formula: see text] do not perform well when different approaches are used to generate the training and testing sets (i.e. out-of-design-type testing). An efficient hybrid design that combines an orthogonal array-based composite design with a small number of [Formula: see text] samples is shown to produce a surrogate model with superior predictive performance.

Stochastic Simulation of Mould Growth Performance of Wood-Frame Building Envelopes under Climate Change: Risk Assessment and Error Estimation

Previous studies have shown that the effects of climate change on building structures will increase the mould growth risk of the wood-frame building envelope in many circumstances. This risk can be controlled by wind-driven rain deflection, improving water tightness of the exterior facade, and improving cladding ventilation. However, the effectiveness of these risk mitigation strategies are subject to various uncertainties, such as the uncertainties of wall component properties and micro-climatic conditions. The objective of this paper is to apply stochastic hygrothermal simulation to evaluate the mould growth risk of a brick veneer-clad wood-frame wall with a drainage cavity under historical and future climatic conditions of Ottawa, a Canadian city located in a cold climate zone. An extensive literature review was conducted to quantify the range of stochastic variables including rain deposition factor, rain leakage moisture source, cladding ventilation rate and material properties of brick. The randomised Sobol sequence-based sampling method, one of the Randomized Quasi-Monte Carlo (RQMC) methods, was applied for risk assessment and error estimation. It was found that, under the climatic condition of Ottawa, limiting the amount of wind-driven rain to which walls are subjected is a more robust mitigation measure than improving cladding ventilation in controlling mould growth risk, the improving of water tightness of exterior façade is not as robust as wind-driven rain deflection and cladding ventilation, however, the reduction of rainwater penetration can reduce the mould growth risk at different levels of rain deposition factor and cladding ventilation rate.

Cyclic behavior of wood-frame shear walls with vertical load and bending moment for mid-rise timber buildings

In light wood-frame buildings, the gravitational and lateral force-resisting systems are composed of floor diaphragms and shear walls. During an earthquake, these walls are subjected to the simultaneous action of in-plane vertical force, shear force, and in-plane bending moment. In a mid-rise building, these internal forces can reach large magnitudes, especially on the lower stories, and could have an important influence on the lateral behavior of the walls. The historical use of light wood-frame construction has been in low-rise buildings. Consequently, few investigations have analyzed the effects of high gravitational forces or in-plane bending moment on the lateral behavior of wood shear walls designed for multi-story buildings. This paper presents an investigation of the cyclic lateral behavior of light wood-frame shear walls, designed for mid-rise buildings, subjected to large axial compressive load and in-plane bending moment. Eight wall specimens were experimentally tested with a cyclic lateral displacement protocol, a constant compressive load, and a cyclic in-plane bending moment. The effects of axial compressive load and in-plane bending moment were analyzed. Also, the wall length and the spacing of sheathing nails were varied to study the effects of these variables on the response. A numerical study was performed to show how these effects could influence the response of mid-rise timber buildings. An improvement in the lateral performance of the walls was observed compared to walls tested without compressive force nor bending moment, showing an increase in stiffness, load-carrying capacity, and dissipated energy.

Current approaches to the modeling and calculation wood frame building, taking into account the joint work of the load-bearing elements of the frame and cladding

The analysis of the current state of issues related to the construction of design models of building structures based on wood. The main software systems are presented, in which the calculation of wooden structures is realized. The need to develop software for timber frame buildings was identified, which would allow an engineer to select sections, check structural units of spatial models of various geometric configurations and take into account the joint work of supporting structures and cladding.

Comparative Review and Assessment of Various Flood Retrofit Methods for Low-Rise Residential Buildings in Coastal Areas

Recent hurricanes indicated that retrofitted residential buildings are still susceptible to wind- and flood-induced damage in coastal areas. This poor performance indicates that flood retrofit methods need to be evaluated in terms of efficiency and effectiveness to resist hurricane wind and flood loads. This paper discusses various aspects in the hurricane-resistant design and retrofit of coastal residential buildings, including potential wind and flood-induced damage, risk mitigation, cost of retrofit methods, and the need for better standards. The cost analysis is performed for a typical one-story wood-frame residential building with a gable roof system considering several flood retrofit methods. The result indicates that selecting a flood protection level higher than the basic 100-year flood level can significantly decrease the risk of damage. This result seems appropriate and essential for specific hurricane-prone regions considering recent changes in the intensity/frequency of storms. A review of actual damage types indicates that wood-frame elevated houses are susceptible to experiencing wind-induced damage to the structural system and more extensive damage to the envelope system. The performance of breakaway walls below the base flood elevation (BFE) strongly depends on the connections between such walls and structural members. The result of cost analysis indicates that the foundation type can directly affect the total cost of retrofit solutions, such as elevation, wet, and dry methods for houses in coastal areas. Regarding the elevation method, adding a freeboard higher than the BFE does not significantly increase the total cost once the elevation method is selected as the preferred retrofit solution.

Benchmarking FEMA P-58 repair costs and unsafe placards for the Northridge Earthquake: Implications for performance-based earthquake engineering

Performance-based earthquake engineering organizes the explicit quantification of building seismic performance and risk, facilitating risk-informed design and mitigation decisions. However, little work has been done to benchmark outcomes from these procedures with the available empirical evidence from past earthquakes. In this study, we benchmark the end-to-end outcomes of the FEMA P-58 performance-based engineering methodology against empirical data from California's 1994 Northridge Earthquake. Specifically, we perform a regional scenario assessment for around 2.6 million buildings in the Los Angeles area at the time of the 1994 earthquake to hindcast repair costs and numbers of unsafe placards from the earthquake. Based on the initial comparison with losses from the Northridge earthquake, we find expected values from our FEMA P-58 regional assessment to overpredict repair costs and unsafe placards, especially for wood frame buildings at low-to-moderate levels of shaking. We use this comparison to investigate underlying methodological and modeling assumptions and propose procedures to improve the outcomes, including increasing elastic damping for wood buildings, updating the FEMA P-58 virtual inspection process for unsafe placarding, and adopting truncated fragility functions to define uncertainties in damage. Outcomes from the proposed methodological updates provide a close match to observed losses in terms of repair costs and numbers of unsafe placards from the event for most building types.

Effect of vapor diffusion port on the hygrothermal performance of wood-frame walls

Vapor diffusion ports (VDPs) that are drilled in the exterior sheathing of wood-frame walls are commonly used in wood-frame buildings in the coastal region of British Columbia with the intention to improve the drying capacity of wood-frame exterior walls. This practice originated following the systematic building envelope failures due to rain penetration that occurred in this region around 1985–1995. A previous laboratory study found that VDPs provided substantial improvement in the drying rates of OSB sheathed walls, but not for plywood sheathed walls. A more recent laboratory test using wood-frame walls with higher insulation levels in compliance with the current energy code found that VDPs did not significantly improve the drying rates. To provide a more comprehensive evaluation of the effect of VDPs, hygrothermal simulations using WUFI 2D are carried out based on the recent tests. The WUFI 2D model is firstly validated with measurements from the recent tests and the validated model is then used for a parametric study to evaluate the effect of VDPs under three wetting scenarios using yearly weather data for Vancouver. It is found that VDPs have the ability to improve the rate of drying, which is directly related to the moisture content level of the wall assemblies, although the improvement is moderate even for high moisture levels. The contribution of VDPs to reducing mold growth risk is insignificant under a moderate moisture load and becomes considerable only under a sustained high level of moisture load, i.e., east orientation with an ongoing rain infiltration. Therefore, efforts should be made towards properly designing and constructing building envelope details instead of relying on VDPs as a mitigation measure to improve durability performance.

Contribution of Partition Walls in Lateral Load–Resisting Systems of Low-Rise Light Wood Frame Buildings

AbstractPrescriptive design is a common practice in North America for low-rise light wood frame buildings. The prescriptive wood-based shear wall details provided in building codes to resist latera...

Seismic force-modification factors for mid-rise wood-frame buildings with shearwalls using wood screws

Wood-screw shearwall (WSS) is generally considered to have limited ductility under seismic load. Conservatively, minimum ductility-related force-modification factor, Rd, of 1.0 and over-strength related force-modification factor, Ro, of 1.3 are used in the National Building Code of Canada for seismic design. In this study, the structural performance of WSS’s with different thicknesses of wood-based panels and sizes of wood screws was investigated by conducting monotonic and cyclic loading tests. The combined force-modification factor RdRo was estimated based on shearwall test results. To verify the estimated modification factors, mid-rise light wood-frame buildings (LWFBs) with different numbers of storeys, wall aspect ratios, magnitudes of gravity and diaphragm flexibilities were designed and analysed numerically. Nonlinear dynamic analyses were performed with 22 scaled Far-Field earthquake time-history records. The seismic response of the mid-rise LWFBs with WSS’s under design hazard level met the design criteria of strength and deformation, and the collapse margin ratios obtained by using a simplified FEMA P695 method complied with the requirements. The study indicates that it is appropriate to use an Rd factor of 1.5 and an Ro factor of 1.7 for seismic design of WSS’s.

Seismic fragility analysis of wood frame building in hilly region

A comprehensive study on seismic performance of wood frame building in hilly regions is presented. Specifically, seismic fragility assessment of a typical wood frame building at various locations of the northeast region of India are demonstrated. A three-dimensional simplified model of the wood frame building is developed with due consideration to nonlinear behaviour of shear walls under lateral loads. In doing so, a trilinear model having improved capability to capture the force-deformation behaviour of shear walls including the strength degradation at higher deformations is proposed. The improved capability of the proposed model to capture the force-deformation behaviour of shear wall is validated by comparing with the existing experimental results. The structural demand values are obtained from nonlinear time history analysis (NLTHA) of the three-dimensional wood frame model considering the effect of uncertainty due to record to record variation of ground motions and structural parameters as well. The ground motion bins necessary for NLTHA are prepared based on the identified hazard level from probabilistic seismic hazard analysis of the considered locations. The maximum likelihood estimates of the lognormal fragility parameters are obtained from the observed failure cases and the seismic fragilities corresponding to different locations are estimated accordingly. The results of the numerical study show that the wood frame constructions commonly found in the region are likely to suffer minor cracking or damage in the shear walls under the earthquake occurrence corresponding to the estimated seismic hazard level; however, poses negligible risk against complete collapse of such structures.

Experimental study of the effects of continuous rod hold-down anchorages on the cyclic response of wood frame shear walls

When designing mid-rise wood frame buildings in high seismicity areas, overturning moments induce large tensile forces in the anchoring system that cannot be resisted by conventional discrete hold-downs. To address this issue, continuous rod hold-downs are used instead to transfer the generated tensile loads to the foundation. However, investigations on the lateral response of wood frame walls employing this anchorage system are quite limited. This paper presents an experimental–numerical study aimed at providing a better understanding of the response of such walls under lateral loads. Four specimens with different configurations were tested under lateral cyclic load, and their behavior was compared with that of walls with discrete hold-downs. Results showed that employing the continuous rod system increases the wall strength by 35.8%, with the specimens behaving elastically up to drifts of about 0.8%. The walls exhibited a marked stiffness degradation during the tests, keeping a residual value of about 15–20% of the initial stiffness. Further analyses showed that the Special Design Provisions for Wind and Seismic (SDPWS) guidelines underestimate the wall strengths by 39.9% and overestimate the stiffnesses by 37.5%, on average. Finally, a nonlinear model was developed to investigate the specimens of this research in depth, showing a special failure pattern that concentrates the damage in the nails located at the central studs of the wall.

Fatigue performance of wood frame roof-to-wall connections with elastomeric adhesives under uplift cyclic loading

Roof-to-wall-connection (RTWC) is critical in the loading path of wood-frame residential buildings, whose fatigue performance under varying wind loading is investigated in this paper. To get an insight on the wind-induced fatigue behavior at low to moderate hourly mean wind speeds and to demonstrate the effects of adhesives on the fatigue performance of RTWC, two types of fatigue experiments, namely the constant and the varying amplitude loading tests, were conducted on three RTWC configurations with and without elastomeric construction adhesives. Based on the constant amplitude loading test results, fatigue life prediction models were developed, and the reduction in the static load capacity due to cyclic loadings were estimated. Adhesives are shown to increase the endurance limit of the RTWCs, which is desirable to enhance the life-cycle performance of wood buildings. The varying amplitude loading test results indicate that buildings in non-hurricane regions are vulnerable to fatigue damage at a low-level mean wind speed. It may induce loadings above the endurance limit of the RTWCs. On the other hand, the linear Miner’s cumulative fatigue damage model can be reasonably used to predict fatigue damage of the RTWCs when subject to multi-amplitude wind loadings. Toenailed connections generally fail in a less ductile manner at a certain number of load cycles with no warnings compared to the connections with adhesives that fail in a more ductile manner. The testing results presented herein provide essential data on the hysteresis behavior and failure modes of RTWCs to facilitate future implementation of adhesives in wood constructions.

Tensile Properties of Utgulisanji Connection

ABSTRACT The objective of this study was to evaluate tensile properties of utgulisanji connection. The utgulisanji connection is a traditional wood-to-wood connection used in wood-frame buildings in Korea. Different sizes (120 × 120, 180 × 180, 180 × 240, 240 × 240 mm2) of glulam beam at 2.4 m length made from Larix kaempferi and Pinus koraiensis were used to determine the tensile properties of utgulisanji connection. Most failure occurred at the re-entrant corner of utgulisanji connections. Different elasto-plastic behaviors of utgulisanji connection made from different species under tension indicated that tensile properties of utgulisanji connection could not be determined by specific gravity, but by a combination of manufacturing parameters with properties of materials. Initial stiffness, yield load, and maximum load of utgulisanji connections determined using three different methods increased with the size of member, whereas the yield displacement showed an inconsistent trend with the size of member.

Holding Ground 1

An exploration of Black freedmen settlements in Austin Texas through archival images and the ecology of place. ​ Black communities in Austin grew along the banks of creeks throughout the city. In many places, all that remains of these important refuges are the waterways that sustained them, the trees that sheltered them and a few historic wood-frame buildings. ​ This project is a cultural cartography of the historic communities that brings together the cultural and ecological context using archival materials and plant materials.

Analysis of Validation and Simplification of Timber-Frame Structure Design Stage with PU-Foam Insulation

The transition from experimental studies to the realm of numerical simulations is often necessary for further studies, but very difficult at the same time. This is especially the case for extended seismic analysis and earthquake-resistant design. This paper describes an approach to moving from the experimental testing of an elementary part of a wood-frame building structure to a numerical model, with the use of a commercial engineering analysis software. In the presented approach, a timber-frame structure with polyurethane (PU)-foam insulation and OSB (oriented strand board) sheathing was exposed to dynamic excitation. The results were then used to generate a numerical 3D model of the wooden frame element. The process of creating the 3D model is explained with the necessary steps to reach validation. The details of the model, material properties, boundary conditions, and used elements are presented. Furthermore, the authors explain the technical possibilities for simplifying the numerical model in used software. Simplifying the model leads to a substantial reduction of calculation time without the loss of accuracy of results. Such a simplification is especially useful when conducting advanced numerical calculations in the field of seismic and dynamic resistant object design.

Liquefaction and Related Ground Failure from July 2019 Ridgecrest Earthquake Sequence

ABSTRACT The 2019 Ridgecrest earthquake sequence produced a 4 July M 6.5 foreshock and a 5 July M 7.1 mainshock, along with 23 events with magnitudes greater than 4.5 in the 24 hr period following the mainshock. The epicenters of the two principal events were located in the Indian Wells Valley, northwest of Searles Valley near the towns of Ridgecrest, Trona, and Argus. We describe observed liquefaction manifestations including sand boils, fissures, and lateral spreading features, as well as proximate non-ground failure zones that resulted from the sequence. Expanding upon results initially presented in a report of the Geotechnical Extreme Events Reconnaissance Association, we synthesize results of field mapping, aerial imagery, and inferences of ground deformations from Synthetic Aperture Radar-based damage proxy maps (DPMs). We document incidents of liquefaction, settlement, and lateral spreading in the Naval Air Weapons Station China Lake US military base and compare locations of these observations to pre- and postevent mapping of liquefaction hazards. We describe liquefaction and ground-failure features in Trona and Argus, which produced lateral deformations and impacts on several single-story masonry and wood frame buildings. Detailed maps showing zones with and without ground failure are provided for these towns, along with mapped ground deformations along transects. Finally, we describe incidents of massive liquefaction with related ground failures and proximate areas of similar geologic origin without ground failure in the Searles Lakebed. Observations in this region are consistent with surface change predicted by the DPM. In the same region, geospatial liquefaction hazard maps are effective at identifying broad percentages of land with liquefaction-related damage. We anticipate that data presented in this article will be useful for future liquefaction susceptibility, triggering, and consequence studies being undertaken as part of the Next Generation Liquefaction project.

Statistical analysis of earthquake debris extent from wood-frame buildings and its use in road networks in Japan

Debris scattering is one of the main causes of road/street blockage after earthquakes in dense urban areas. Therefore, the evaluation of debris scattering is crucial for decision makers and for producing an effective emergency response. In this vein, this article presents the following: (1) statistical data concerning the debris extent of collapsed buildings caused by the 2016 Mw 7.0 Kumamoto earthquake in Japan; (2) an investigation of the factors influencing the extent of debris; (3) probability functions for the debris extent; and (4) applications in the evaluation of road networks. To accomplish these tasks, LiDAR data and aerial photos acquired before and after the mainshock (16 April 2016) were used. This valuable dataset gives us the opportunity to accurately quantify the relationship between the debris extent and the geometrical properties of buildings.

Connection Performance of Mass Plywood Panels

Abstract Tall wood buildings have become more prevalent in North America in the past 10 years. Tall wood-frame buildings implement both mass timber construction and products. Mass timber products are wood-based products that can withstand and hold large loads for long durations of time. Mass timber has allowed for large buildings, which consist mainly of wood, to be erected comprising multiple stories. One new mass timber product that has been fashioned is Mass Plywood Panels (MPP). MPP is a veneer-based engineered wood product, which is a massive, large-scale, structural composite lumber–based panel designed for use in building applications as both a vertical and horizontal element. For any new product to be used in the industry with confidence, a thorough investigation of its physical, mechanical, and connection properties is needed. A series of connection tests, such as fastener withdrawal resistance, dowel-bearing strength, lateral resistance, and a component test on a wall-to-floor system were conducted. The lateral resistance test indicated that the current European Yield Models can be used to calculate the yield loads and yield mode of the MPP by using the dowel-bearing strength of plywood. Three different connection configurations were tested in two distinct loading directions—shear and withdrawal. Their performances are evaluated and compared using two existing engineering models—namely, the American Society of Civil Engineers 41-13 tri-linear model and the seismic analysis of wood-frame structures 10-parameter connection model.