Progress 06/01/04 to 05/31/10
Outputs
OUTPUTS: The following studies were conducted during this period: Effects of Reference Displacement and Damage Accumulation in Wood Shear Walls: The objectives of this study were: (1) to evaluate the effect of reference displacement on wall behavior under fully reversed cyclic loading using the CUREE test protocol and (2) to assess damage accumulation for the imposed drift levels. The Effect of Hold-down Misplacement on the Strength and Stiffness of Wood Shear Walls: The objective of this study was to determine the effect of misplaced hold-downs on the monotonic and cyclic behavior of wood shear walls. Comparison of Screening, Evaluation, Rehabilitation and Design Provisions for Wood-Framed Structures: This investigation examines the demand-to-capacity ratios for shear walls and roof diaphragms in the two existing wood-framed structures. This study also discusses the assumptions and methods employed for investigation of two wood structures using four references: FEMA 154, FEMA 356, ASCE/SEI 31, and 1997 UBC. Performance of Partially and Fully Anchored Wood Frame Shear Walls Under Monotonic, Cyclic & Earthquake Loads: The objectives of this study was to evaluate the performance of wood frame shear walls under monotonic, cyclic and earthquake loads. The Performance of Wood Frame Shear Walls Under Earthquake Loads: The overall goal of this study is to evaluate the earthquake performance of wood frame shear walls, and more specifically to get a preliminary understanding of the performance of walls subjected to a sequence of earthquakes, and to compare this performance with that of walls subjected to a single earthquake. Performance of Wood Frame Wall with Thin Shell ECC Shear Panel: The overall goal of this study was to evaluate an alternative to traditional wood framed shear wall construction. This study introduced the innovative idea of using a water and seismic damage resistant, wood concrete-composite (WCC) construction instead of an all-wood design. The WCC design consisted of a thin shell of engineered cementitious composite (ECC) cast in composite with a traditional wood frame. Strain Distribution in OSB and GWB in Wood Frame Shear Walls: The overall goal of this study was to gain an insight into the load sharing aspect between oriented strand board (OSB) and gypsum wall board (GWB) in shear wall assembly during racking load. PARTICIPANTS: Jeff Langlois, Dana Lebeda, Preston Baxter, Arijit Sinha, Mike Lewis, Kevin White, Peter Seaders, and Thomas Miller. TARGET AUDIENCES: Structural Engineers, Home Builders, Building Contractors PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Effects of Reference Displacement and Damage Accumulation in Wood Shear Walls: Results show that the reference displacement can influence wall strength by up to 15 percent while there was little or no effect on stiffness and area under the backbone curve. Results also show that while visible damage was minimal at drifts as high as 1 percent, (8 percent of nails slightly damaged), a 52 percent reduction in secant stiffness had occurred. The Effect of Hold-down Misplacement on the Strength and Stiffness of Wood Shear Walls: Results from this study show that misplaced hold-downs cause reductions in strength and absorbed energy. The strength reductions are much higher than the 17 percent anticipated strength loss due to the reduction in effective wall width. Application of a denser nail spacing to the stud attached to the misplaced hold-down helped achieve higher strength. Comparison of Screening, Evaluation, Rehabilitation and Design Provisions for Wood-Framed Structures: The results of this study show that the new building design provisions in the 1997 UBC are not necessarily conservative when compared to the rehabilitation design provisions in FEMA356. The provisions in the design documents FEMA356 and the 1997 UBC are not necessarily conservative when compared to existing building evaluation provisions in ASCE 31. Performance of Partially and Fully Anchored Wood Frame Shear Walls Under Monotonic, Cyclic & Earthquake Loads: CUREE tests generally appear to give a more conservative estimate of shear wall performance under actual earthquake loads than monotonic tests. A comparison of the test results with FEMA 356 m-factors also shows that the ductility of partially anchored walls is below the acceptance criteria for shear walls with structural panel sheathing. The Performance of Wood Frame Shear Walls Under Earthquake Loads: The results of preliminary tests for fully and partially anchored walls subjected to a sequence of earthquake loads show that wall performance was about the same or better than the performance under a single earthquake loading, depending on the performance measure. Overall, the results from this study suggest that cyclic tests, rather than monotonic tests, may provide the most conservative measure for some characteristics of wall performance under design earthquake loads. Performance of Wood Frame Wall with Thin Shell ECC Shear Panel: Overall, the test results indicate that the WCC is comparable with or superior to the OSB wall in regards to shear strength, shear stiffness, energy absorption and ductility. During lateral loading tests the WCC wall appeared to sustain less damage than the OSB wall. The WCC design appears to be a viable shear wall system that should be refined and fully tested for building code compliance. Strain Distribution in OSB and GWB in Wood Frame Shear Walls: Overall, these tests suggest that initially during loading of a wall the load is shared between OSB and GWB. However, the proportion of load sharing is not known. As GWB fails first the load shifts to the OSB panel which resists it till the failure of the wall.
Publications
- White, K.B.D., T.H. Miller and R. Gupta. 2010 Effects of Dead Load and Multiple Earthquake Loadings on Seismic Performance of Wood-Frame Shear Walls. Forest Products Journal 60(2):150-156.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: The overall goal of this project was to design a wood frame shear wall which could withstand greater displacement before damage occurred to the Gypsum Wall Board (GWB). More specifically, the objectives of the study were to: (1) to evaluate damage to the GWB in alternative shear wall designs at 1%, 2% and 3% drift levels and compare these results to current performance based design standards; (2) to evaluate quantitatively the relative displacement between the GWB and the wood frame under monotonic loading; and (3) to evaluate the value of alternative shear wall designs considering damage sustained from design drift levels. A total of 14 shear walls consisting of seven different designs with two walls built per design were tested to failure. Six of these walls had 1105 x 610 mm window openings and eight did not. All shear walls were 2440 x 2440 in size and built from 38 x 89 mm Douglas fir studs at 610 mm on center. The seven shear wall designs tested included two control designs based on the minimum International Residential Code requirements. One control design included a window opening and another did not. The SEPSTUD wall design included a larger screw to GWB edge distance, while the 3INNAIL design included a smaller OSB nail spacing. The 2OSBWIN and 2OSB wall designs, respectively with and without a window opening, included Oriented Strand Board (OSB) panels attached to both sides of the wood frame and the GWB attached on top of the OSB. The 4PNLWIN design attached the GWB as four different panels around the window opening, instead of two panels. PARTICIPANTS: Scott Goodall, Graduate Research Assistant, Wood Science and Engineering, Oregon State University and Milo Clauson, Senior Faculty Research Assistant, Wood Science and Engineering, Oregon State University TARGET AUDIENCES: Structural Engineers, Home Builders, Building Contractors PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Shear wall test behavior generally agreed with the ASCE/SEI 41-06 performance based drift criteria. 1% drift occurred between 57%-80% of total wall capacity, 2% drift occurred between 84%-97% of wall capacity and 3% drift occurred between 97%-100% of wall capacity. The results of the visual failure comparison indicated that little damage was observed in the GWB for walls loaded to the NDS allowable strength. The results of the shear wall visual failure comparison indicated that all innovative shear wall designs outperformed the control designs at 1% drift. At 2% and 3% drift, the 4PNLWIN and SEPSTUD designs preformed worse than the control. The 3INNAIL design preformed slightly better and the 2OSB and 2OSBWIN designs preformed superior to the control designs at 2% and 3% drift. The greater performance of all these designs can be attributed to the increase in strength and stiffness of these shear walls. However, superior performance of the 2OSB and 2OSBWIN designs was due to the similar stiffness of both sides of the shear wall, resulting in equal load sharing and less damage to the GWB. Shear walls with magnitudes of the relative displacement vectors above the visual failure limit of 3 mm exhibited inferior GWB performance which is consistent with the visual failure results. A cost benefit analysis indicated that the 3INNAIL, 2OSB and 2OSBWIN designs all exhibited a more efficient use of shear wall materials at 1% and 2% drift than the control designs. However, when considering a design earthquake drift level, 2OSB and 2OSBWIN designs demonstrate the most efficient use of shear wall materials.
Publications
- Seaders, P., R. Gupta and T.H. Miller. 2009. Monotonic and cyclic load testing of partially and fully anchored wood-frame shear walls. Wood and Fiber Science 41(2):145-156.
- Seaders, P., T.H. Miller and R. Gupta. 2009. Performance of partially and fully anchored wood frame shear walls under earthquake loads. Forest Products Journal 59(5):42-52.
- Sinha, A. and R. Gupta. 2009. Strain distribution in OSB and GWB in wood-frame shear walls. Journal of Structural Engineering 135(6):666-675.
- Jayawickrama, K.J.S., T.Z Ye, R. Gupta and M.L. Cherry. 2009. Including wood stiffness in tree improvement of coastal Douglas-fir in the US Pacific Northwest: A literature review and synthesis. Research Contribution 50, Forest Research Laboratory, College of Forestry, Oregon State University, Corvallis.
- Lewis, M.C., R. Gupta and T.H. Miller. 2009. Performance of wood frame wall with ECC shear panel. Practice Periodical on Structural Design and Construction 14(3):123-129.
- Oshnack, M.B., F. Aguiniga, D. Cox, R. Gupta and J. van de Lindt. 2009. Effectiveness of small onshore seawalls in reducing tsunami forces induced by tsunami bore: Large scale experimental study. Journal of Disaster Research 4(6):382-390.
- van de Lindt, J., R. Gupta, D.T. Cox and J. Wilson. 2009. Wave impact study on a residential building. Journal of Disaster Research, 4(6):419-426.
- van de Lindt, J., R. Gupta, R. Garcia and J. Wilson. 2009. Tsunami bore forces on a compliant residential building model. Engineering Structures 31(2009):2534-2539.
- van de Lindt, J.W., Y. Li, W.M. Bulleit, R. Gupta and P.I. Morris. 2009. The next step for AF&PA/ASCE 16: Performance-based design of wood structures. Journal of Structural Engineering 135(6):611-618.
- White, K.B.D., T.H. Miller and R. Gupta. 2009. Seismic performance testing of partially and fully anchored wood-frame shear walls. Wood and Fiber Science 41(4):396-413.
- Wilson, J., R. Gupta, J. van de Lindt, M. Clauson and R. Garcia. 2009. Behavior of a one-sixth scale wood-framed residential structure under wave loading. J. of Performance of Constructed Facilities 23(5):336-345.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The overall goal of this part of the project was to evaluate an alternative to traditional wood framed shear wall construction. This study introduced the innovative idea of using a water and seismic damage resistant, wood-concrete-composite (WCC) construction instead of an all-wood design. The WCC design consisted of a thin shell of engineered cementitious composite (ECC) cast in composite with a traditional wood frame. The WCC wall was evaluated with regards to structural performance during lateral loading, cost and damage sustained during lateral loading. The WCC test results were compared to a traditional wood frame wall with OSB sheathing. Data from the monotonic tests of the WCC walls show that the average maximum load was 47.5 kN (10700 lb), average elastic shear stiffness was 1.78 kN/mm (10200 lb/in) and the average energy absorbed was 4810 J (42600 lb-in). Overall, the test results indicate that the WCC is comparable with or superior to the OSB wall in regards to shear strength, shear stiffness, energy absorption and ductility. During lateral loading tests the WCC wall appeared to sustain less damage than the OSB wall. Panelized construction of the WCC system may increase overall project cost but could provide many additional benefits such as decreased construction time and greater durability. The WCC design appears to be a viable shear wall system that should be refined and fully tested for building code compliance. PARTICIPANTS: Mike Lewis - Graduate Student (This was his idea and he did all the work); Tom Miller - Co-Thesis Advisor. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This research project seeks to provide a solution to the performance problems associated with seismic damage and moisture damage sustained by traditional wood framed shear walls. This study introduced the innovative idea of using a water and seismic damage resistant, wood-concrete-composite (WCC) construction instead of an all-wood design. The WCC design consisted of a thin shell of engineered cementitious composite (ECC) cast in composite with a traditional wood frame. The main energy dissipation modes for the wood concrete composite (WCC) construction are fundamentally different from wood sheathed walls. The WCC walls dissipate energy through deformation of the polymer reinforcement. The WCC structure is designed to prevent fastener (staple) deformation or withdrawal and damage to the wood frame. This is achieved by designing the wall system such that the reinforcement strength is less than the fastener yield or withdrawal strength and wood strength. The concrete material used in this study was Engineered Cementitious Composite (ECC). This is a fiber reinforced concrete-like material that exhibits strain hardening and steady-state, flat cracking behavior in tension and flexure. Steady-state, flat cracking behavior occurs when each crack that initiates in the concrete matrix maintains a uniform and very small width along the entire length of the crack. Fiber bridging behavior allows the fibers in the concrete to continue transferring load across the crack without loss of strength. Polyvinyl alcohol (PVA) fibers are used in this variety of ECC to provide tensile strength during fiber bridging. If the ECC should be exposed to tensile stress that causes cracking, the behavior of the material is ductile. Tension cracking in normal concrete creates a brittle failure that is undesirable from a safety and durability standpoint. ECC also provides an extremely durable shell that can withstand severe freeze/thaw cycles and has low permeability to moisture. The PVA-ECC used in this study is usually ductile to approximately 2-5 percent tensile strain. Finally, this research study attempted to synthesize these new ideas into the design of an optimum WCC structure. The current design dissipates lateral forces mainly by inelastic deformation of the polymer grid reinforcement. The design attempted to minimize inelastic fastener deformation by engineering a fastening system that is stronger than the reinforcing grid in tension. The goal of the proposed design is to create a WCC shear wall that can withstand lateral forces with only minor damage to the fastener system, ECC shell and wood components. The WCC shear wall is intended to remain in service after experiencing lateral loading conditions that would cause a traditional wood shear wall to require replacement or major repair.
Publications
- Wilson, J. 2008. Behavior of a 1/6th Scale, Two-Story, Wood Framed Residential Structure under Surge Wave Loading. M.S. Thesis. Department of Wood Science and Engineering and School of Civil and Construction Engineering. Oregon State Univ., Corvallis. 109 p.
- Gupta, R. and P. Limkatanyoo. 2008. Practical approach to designing wood roof truss assemblies. Practice Periodical on Structural Design and Construction 13(3):135-146.
- Lewis, M. 2008. Performance of Wood Frame Wall with Thin Shell ECC Shear Panel. M.S. Thesis. Department of Wood Science and Engineering and School of Civil and Construction Engineering, Oregon State Univ., Corvallis. 92 p.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Damage assessments performed after recent natural disasters (earthquakes and hurricanes) have demonstrated that damage to residential wood structures is significant during these events. Some of these losses may be due to gaps in knowledge that require testing of wood-frame structures to be more representative of the in-service conditions. The goal of projects in this area is to gain an insight into the behavior of wood structures as a system and their components under actual lateral loads, like subduction zone earthquake and wave loads cause by storm surge during hurricane or Tsunami.
PARTICIPANTS: Rakesh Gupta, Principal Investigator; Heather Redler, Graduate Student; Arijit Sinha, Graduate Student; Bill Kirkham, Graduate Student; Preston Baxter, Graduate Student; Jebediah Wilson, Graduate Student; Kraisorn Lucksiri, Graduate Student; Tom Miller, Collaborator; and John van de Lindt, Collaborator.
Impacts
The impact of a recent study in this area (Redler - MS Thesis, expected completion 2008) has been summarized by Philip Line, P.E., Manager, Engineering Research, American Wood Council, American Forest & Paper Association, Washington, DC (email dated 10/08/2007) as follows: "Data from the OSU shear wall tests conducted for AF&PA have been used as part of a benchmark setting effort within the International Code Council - Evaluation Service process. The same data set has also been useful in activities of the Building Seismic Safety Council's Technical Subcommittee 7 on Wood for purposes of defining wood-frame shear wall performance expectation. Finally, data has been shared with a Task Group working under AF&PA Wood Design Standards Committee in order to address inconsistent recommendations for bottom plate anchorage requirements for shear walls." Another major effort underway in this area is the development of a rapid screening and analysis system for estimating and
mitigating seismic losses in single-family, wood-frame dwellings (Kirkham and Lucksiri - current PhD projects). The research in this area has generated considerable interest in the Oregon building community and has received media/public attention. The other most significant work I have done in this area was damage assessment of wood-frame residential structures in the wake of Hurricane Katrina. I was a part of a five member, NSF-funded team that toured the Gulfport/Biloxi area in Mississippi three weeks after Katrina made landfall. Our goal was to gather and process perishable wind-damage data on residential wood-frame structures in non-flooded regions of Mississippi that can be used by the research and design code development community to improve the performance of wood-frame structures to strong wind loading. The results of this study were published in more than 100 newspapers worldwide and one peer-reviewed publication (van de Lindt et al. 2007). The study has also led to NSF
funding of an SGER NEESR payload project to study wave loading on residential structures with earthquake and hurricane applications. We will be testing a 1/6th scale, two-story wood frame residential structure in the Tsunami wave basin in Fall of 2007 (Wilson - current MS Project).
Publications
- Baxter, P., T.H. Miller and R. Gupta. 2007. Seismic screening, evaluation, rehabilitation and design provisions for wood-framed structures. Practice Periodical on Structural Design and Construction. (In Press).
- van de Lindt, J.W., A.J. Graettinger, R. Gupta, T.D. Skaggs, S.E. Pryor and K.J. Fridley. 2007. Performance of wood-frame structures during Hurricane Katrina. Journal of Performance of Constructed Facilities 21(2):108-116.
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Progress 01/01/06 to 12/31/06
Outputs
Year 2006 focused on developing a proposal for testing pitched roof diaphragms. While experimental studies on wood frame shear walls are plentiful, testing of roof diaphragms (pitched or flat) has been very rare, probably due to cost and complexity associated with the testing such systems. Much of the work has been concentrated on large, flat diaphragms used in masonry or light framed wood construction of commercial buildings. These studies have been intended to test large high capacity diaphragms commonly seen in commercial construction. They are typically flat, blocked, chorded, and constructed on dimension lumber or heavy timber framing without a directly attached finished ceiling. These diaphragms have been frequently damaged in major earthquakes. Before the Northridge earthquake, residential buildings were largely viewed as "safe" in earthquakes, so little research had been performed in typical residential construction. Commercial diaphragms seldom have
significant pitches. The goal of most previous testing has been to evaluate the strength of the horizontal diaphragm configurations. Formulas were also developed for the deflection of the diaphragm at the elastic limit maximum loading. These formulas are of limited use to us. The most common residential diaphragm configuration is generally pitched, is not blocked, and is constructed on light trusses with a horizontal, stiff gypsum ceiling. Our proposal includes testing of flat and pitched (gable and hip) diaphragms of the construction used in typical residential construction. The project also began development of tools for rigid diaphragm analysis for a house (UCSD house) which was tested on a shake table as a portion of the CUREE-Caltech woodframe project. The basic house has been modeled in Vectorworks (VW) 12 which is an extensible, programmable CAD program. The three dimensional model includes exact locations of doors and windows in the walls and types of wall finishes so that
wall stiffnesses can be correctly determined. Special macros in VW determine the center of mass for each level of the structural model. VW also determines the relative stiffness of the shearwall components through database queries of the three-dimensional model. Center of rigidity is determined by considering the relative stiffnesses of the supporting shear walls. Once the centers of mass and rigidity are known, and the relative stiffnesses of the walls are estimated, torsional analysis is performed. The damage states are assigned based on the calculated wall deflections. The results will be compared to the actual performance of the UCSD house. The tools are undergoing testing at this time and further development and testing will continue into 2007.
Impacts
Most structures in the US are wood-frame residential dwellings and were constructed before seismic provisions were introduced during the 1970s and 1980s. Therefore, it is important to know how these structures would perform under a major seismic event. This project will provide a practical analytical tool to assist in evaluation of existing dwellings.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Year 2005 focused on researching literature on pitched roof diaphragm tests and a review of the current standard used for the metal-clad, post-frame building roof diaphragm. This was conducted to determine the state of the art in roof diaphragm testing of wood frame housing. CUREE wood frame project findings were also evaluated in light of the goals of this project since our goal is to compliment and extend the work of CUREE-Caltech Wood frame Project. Our goal is to perform analyses on specific selected floor plans using traditional use of designed structural shear walls as the principal resisting system. The evaluation method will be flexible diaphragm analysis as per IBC, rigid diaphragm analysis (torsion) adapted from Seismic Design Handbook and a two dimensional adaptation of a stiffness method. The design hazard will be based on USGS Seismic maps from FEMA 356. There are a few other methods (FEMA 154, ASCE 31, FEMA 356) to evaluate existing structures but non
specifically designed for single-family dwellings. These methods have their merits but they are generally too complex to be applied to single-family dwellings. Wood frame structures with wood shear walls and diaphragm are typically designed as flexible diaphragm structures, regardless of configuration. It is unlikely that structures with significant plan irregularities or large horizontal diaphragm openings will behave as ideal diaphragms. An analysis of a simple wood frame, box-type structure with openings in shear walls reveled that its diaphragm behaved like a rigid diaphragm. More analysis of such types for typical wood frame residential buildings and for a few structures which have been tested on shake table (from literature) is underway. Year 2006 will also focus on developing a proposal for testing pitched roof diaphragm.
Impacts
Most structures in the US are wood-frame residential dwellings and were constructed before seismic provisions were introduced during the 1970s and 1980s. Therefore, it is important to know how these structures would perform under a major seismic event. This project will provide a practical analytical tool to assist in evaluation of existing dwellings.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
In 2004, a literature review was conducted to determine the state of the art in seismic evaluation of woodframe housing. CUREE wood frame project findings were also evaluated in light of the goals of this project since our goal is to compliment and extend the work of the CUREE-Caltech Woodframe Project. Eighty to ninety percent of all structures in the U.S. are wood structures. In Los Angeles County, 96 percent of all buildings are of wood-frame construction. In the U.S. and Canada, more wood, measured either by weight or by volume, is used in construction than all other construction materials combined. The current stock of the American houses showed that most residential dwellings were constructed before most of the current seismic design provisions were introduced during the 1970s and 1980s. More than half of the existing housing inventory was constructed before 1970. Seventy-five percent were constructed before 1985. Engineered seismic design for residential
dwellings is generally not done because they are built according to the prescriptive code provisions, like International Residential Code. Therefore, seismic performance of these structures is critical to understand. There are a few methods (FEMA 154, ASCE 31, FEMA 356) to evaluate existing structures but not specifically designed for single-family dwellings. These methods have their merits but they are generally too complex to be applied to single-family dwellings. Wood frame structures with wood shear walls and diaphragm are typically designed as flexible diaphragm structures, regardless of configuration. It is unlikely that structures with significant plan irregularities or large horizontal diaphragm openings will behave as ideal diaphragms. An analysis of a simple woodframe, box-type structure with openings in shear walls revealed that its diaphragm behaved like a rigid diaphragm. More analysis of such types for typical woodframe residential buildings and for a few structures
which have been tested on the shake table (from literature) is underway, and will be the focus of this project in 2005.
Impacts
Most structures in the US are wood-frame residential dwellings and were constructed before seismic provisions were introduced during the 1970s and 1980s. Therefore, it is important to know how these structures would perform under a major seismic event. This project will provide a practical analytical tool to assist in evaluation of existing dwellings.
Publications
- Kirkham, W.J., R. Gupta and T.H. Miller 2004. Development of a Practical Analysis System for Estimating and Mitigating Seismic Damage in Single-Family Dwellings. Poster. 11th Annual Meeting of the Earthquake Engineering Research Institute, February 4-7, Los Angeles, CA.
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