Progress 07/01/12 to 06/30/17
Outputs
Target Audience:wood engineers/technologist, civil engineers, truss designer, Residential Building Designer Changes/Problems:there were no major changes/problems in approach in this project. What opportunities for training and professional development has the project provided?This project has trained 4 graduate students/. How have the results been disseminated to communities of interest?So far results have been in refereed journal and conference proceedings. That is how the results of further studies will be disseminated What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
A practical 3D model of a full-size, wood-frame residential structure was created via four MS projects. This project was designed to evaluate wind load. The model was then used to accomplish the second objective focused on evaluation of load paths. In the future, this same model can be used to evaluate seismic loads as well. The third objective, to develop design guidelines for disaster resistant housing is ongoing based on result of the study #4. The first two goals were met by doing the following four studies: Study #1 (Pfretzschner 2012) - The objective of this study was to develop and validate practical modeling methods for investigating load paths and system behavior in a realistic, light-frame wood structure. The activities included modeling an L-shape house. The modeling methods were validated against full-scale tests on sub-assemblies and an L-shaped house. The model of the L-shaped house was then modified and used to investigate the effects of re-entrant corners, and wall openings on system behavior and load paths. The study showed that the effects of adding re-entrant corners and wall openings on uplift load distributions were dependent on the orientation of the trusses with respect to the walls. Openings added to walls parallel to the trusses had the least effect on loads carried by the remaining walls in the building. Varying re-entrant corner dimensions of the L-shaped house under ASCE 7-05 design wind loads caused increasing degrees of torsion throughout the house, depending on the relative location and stiffness of the in-plane walls (parallel to the applied wind loads) as well as the assumed direction of the wind loads. Balancing the stiffness of the walls on either side of the house with the largest re-entrant corner helped to decrease torsion in the structure somewhat. Study #2 (Malone 2013) - Timber frame (TF) and light frame (LF) buildings were used to model load paths. Modeling methods developed by Martin et al. (2011) and further developed and validated by Pfretzschner et al. (2012), Study #1, were used for the creation of structural models. Models for each framing system (LF and TF) were created using SAP2000 (2012) structural analysis software, and load paths generated by applied design loads were investigated and compared. Both structures were modeled with and without openings (doors and windows), and comparisons were made based on resistance to uplift, story drift and twisting, the addition of large openings, a break in load path, and the relative ranges of axial loads in posts and studs. Results showed that the TF outperforms the LF in resisting uplift, as well as in story drift. The TF also provided load paths that are more resilient to the introduction to large openings and the loss of a central post. Observed axial loads in posts showed smaller ranges compared to LF studs. Study #3 (Huynh 2016) - This study involved creation of realistic light frame wood building model. A 3D computer model of an index building (provided by Modern Building Systems Inc.) was developed. Based on 3D modeling of the index building we evaluated the four foundation types, given below: Typical "block and level" with tie down straps Concrete piers at corners, endwall columns and center column. Concrete piers at endwall columns and center column with smaller concrete piers at optimum spacing around perimeter of building. Continuous concrete strip footing at perimeter of building and concrete piers at endwall and center columns. There would still be discrete attachment points at 6' O.C. along the strip footing, so very similar to foundation #3. Analysis was performed for a series of foundation types to examine effects on overall and local behavior. The effectiveness of the different foundation schemes was evaluated. It was found that the racking shear stiffness calibration procedures implemented previously for light-framed construction were also applicable for light-frame, modular shear walls. Additionally, it was found that anchorage elongation substantially affects the racking shear stiffness of shear walls with aspect ratios within limits similar to those provided by the Special Design Provisions for Wind and Seismic Design Standard. For regularly shaped modular structures, it was found that assuming tributary areas of resisting elements for lateral loads produced conservative demands when ignoring contributions from uplift pressures from wind loads. Thousands of structures such as these are being used throughout the United States in various applications. Consequently, with wind loads being a major contributor to annual structural damage of light-framed wood structures and a need for methods to sufficiently evaluate load paths, this study was an important development in the design of modular buildings and their acceptance by building code officials. Study #4 (Holman 2018) - This study is ongoing with anticipated completion by late 2018. Based on currently completed work, it can be concluded that a light frame wood buildings can be modeled in 3D, using a commercially available software, in order to take into account all of the system effects! Currently, the roof of a house is designed in 2D with each truss type designed in 2D. With this simple changed in the design to a 3D, a designer can take into account all of the system effects directly, insured of including them in some artificial way by including a number.
Publications
- Type:
Theses/Dissertations
Status:
Other
Year Published:
2018
Citation:
Pfretzschner, Kate 2012 Practical Modeling for load paths in a realistic, light frame house. M.S. Thesis
Malone, Brian P. 2013 Light frame versus timber: A study in quantifying the differences. M.S. Thesis
Huynh. Q. T. 2016 Lateral load path analysis: practical methods for light-frame modular structures. M.S. Thesis
Holman, J. 2018 Load path analysis of a real house. M. S. Thesis (In-preparation)
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:Engineers, architects, house designers, wood scientists and technologists Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?training of graduate students! How have the results been disseminated to communities of interest?mainly thru the refereed publications. What do you plan to do during the next reporting period to accomplish the goals?We are in the process of developing the model for a real house. We have just acquired the plans for the house. We will be reporting the result of such an analysis. After doing this step, the following three objectives will guide us at to what we will be reporting. 1. Develop a practical 3D computer model of a full-size, wood-frame, residential structure with a realistic, complex geometry. 2. Evaluate critical load paths and system effects under various extreme (e.g., wind - hurricanes and tornadoes and seismic) loading scenarios. Examine load concentration effects of the complex-plan-geometry structure. 3. Develop design guidelines for the disaster resistance housing.
Impacts
What was accomplished under these goals?
We have hired a graduate student to work on the project, and he is working a bit slower then expected. But we hope to have the resuls by end of the summer of 2017.
Publications
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Progress 10/01/14 to 09/30/15
Outputs
Target Audience:Engineers, architects, house designers, wood scientists and technologists Changes/Problems:nothing major, this past year we modeled a modular class room instead of a real house , mainly because the geometry of the structure was available. but this year we are planning to model a real house. What opportunities for training and professional development has the project provided?Three Graduate students have been trained. How have the results been disseminated to communities of interest?Yes, thru the journal articles, and we will continue to do it. What do you plan to do during the next reporting period to accomplish the goals?Finally, we will take a real house and model its complex geometry to look at the load paths and system efffects...!
Impacts
What was accomplished under these goals?
A model of a modular classroom structure is used to investigate the effects of stiffness distribution, torsion and uplift on system behavior and lateral load paths. ASCE 7-10 main lateral force resisting system and components and cladding wind loads are applied in perpendicular directions to the load bearing walls. The analysis is done for a series of foundation types. The modifications in the foundation change the locations where the structure is securely connected to the foundation, and therefore have significant effects on how the load will be distributed throughout the structure. Thousands of structures such as these are used throughout the United States. Consequently, with wind loads being a major contributor to annual structural damage and a lack of methods to evaluate sufficient load paths, accurate modeling techniques to validate the performance of these structures is integral to attesting that these structures are safe for occupancy under their designed loads.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
1. Pfretzschner, K., Gupta, R. and Miller, T.H. 2014 Practical Modeling for Load Paths in a Realistic, Light-Frame Wood House. J. of Performance of Constructed Facilities, Vol. 28(3):430-439.
2. Malone, B., Gupta, R., Miller, T.H., and Puettmann, M. 2014 Environmental impact assessment of light-frame and timber frame buildings. J. of Green Building, 9(2):102-123
3. Malone, B., Miller, T.H. and Gupta, R. 2014 Gravity and wind load path analysis of a light-frame and a traditional timber frame building. Journal of Architectural Engineering, 20(4): B4013001-1 to 10
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Engineers, architects, house designers, wood scientists and technologists Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals? Three-dimensional models previously developed for 3D roof truss assemblies at OSU will be modified and used to model the building. All truss members and studs will be modeled as beam-column or column elements. For simplicity and practicality, all joints will be either pinned or rigid depending on the continuity of the members. Sheathing beams will be modeled using frame elements with a row of these elements representing a row of roof/wall sheathing. The sheathing beam element will be assigned the same thickness, tributary width, and modulus of elasticity (MOE) as the actual plywood/OSB sheathing. Sheathing beams will be rigidly connected to the truss top chord with no discontinuities between sheathing panels to include "two-way action." The model will include structural straps and connectors and all exterior walls will include interior gyp board finish, as specified in construction drawing set. Note that the interior restroom walls that are shown in the provided plans may be omitted from the model. Based on the findings from OSU studies, truss supports will be assumed as pinned where the side walls and end or cross walls intersect. Roller supports are assumed where side walls do not meet with either cross or end walls. Moreover, the wall top plate will be modeled using frame elements with the same physical properties as the actual top plate, and be rigidly connected to the heel joints. All the studs will be modeled as column element with sheathing beam rigidly connected to it. Foundation anchorage will vary as described above. A linear elastic analysis will be done at the baseline load level and at a load level that creates the maximum code allowable diaphragm deflections. In a wood truss assembly, the variation of stiffness (MOE) in wood members actually creates a significant and beneficial system effect where stiffer/stronger trusses carry more load than more limber and weaker trusses. This has been observed in a number of previous research studies. This study will use deterministic material properties. Specific objectives of the proposed project are: 1. Develop a practical 3D computer model of a full-size, wood-frame, residential structure with a realistic, complex geometry. 2. Evaluate critical load paths and system effects under various extreme (e.g., wind - hurricanes & tornados and seismic) loading scenarios. Examine load concentration effects of the complex-plan-geometry structure. 3. Develop design guidelines for the disaster resistance housing. Objectives 1 and 2 will be partially completed by the end of summer of 2015.
Impacts
What was accomplished under these goals?
The practical modeling methods developed by Martin (2010) were used to develop a three-dimensional structural model of the L-shaped house constructed and tested by Paevere (2002) in Australia. The model was fully developed using the commercial software package: SAP2000 (2012) Version 14. After verification of the model, the full house model was used to explore load paths and system behavior within the structure under various load cases. Currently we are in the process of modeling a realistic light frame wood building. A three-dimensional computer model of an index building (provided by the Modern Building Systems Inc.) is being developed. Please see figure 1 for the index building. Based on 3D modeling of the index building we will be evaluating for the four foundation types. Typical "block and level" with tie down straps as detailed in the provided plan set. Concrete piers at corners, endwall columns and center column. Concrete piers at endwall columns and center column with smaller concrete piers at optimum spacing around perimeter of building. Continuous concrete strip footing at perimeter of building and concrete piers at endwall and center columns. There would still be discrete attachment points at 6' O.C. along the strip footing, so very similar to #3. Also note that where CMU block piers are present, they act to resist gravity loads but not uplift. For each of the (4) foundation types we will look at the option of sizing the center column pier for gravity loading only. This means that there would be net uplift at the center column that would be transferred through the roof ridge beams to the endwall columns. Each model will also be loaded to create the maximum code allowable deflection of the building diaphragms to determine the reserve capacity. The report results will include wind or seismic loading (as required by code), be detailed enough to follow the wind loading analysis procedure and contain a summary of the overall results. It appears that SAP2000 has an internal wind loading analysis and this may be acceptable. Should the analysis find a 'weak link' where a strap or simple modification could significantly enhance the response of the building, Modern would be given an opportunity to modify the model and run the analysis again. Baseline lateral loading to be: Wind: Vult= 140 mph (3-sec gust) exposure B Seismic: Ss=1.50 This work, evaluation of system effects and load paths will be conducted in a rectangular building using SAP2000. The building will be constructed using typical residential construction based on the PI's expertise. Construction drawings will be used to layout the assembly, and to provide geometry and loading conditions for the building. Based on the geometry, material properties, and loading a 3D assembly model will be generated for system analysis in SAP2000. Results from SAP2000 will be used to describe system behavior along with the load path.
Publications
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Engineers, Architects, House Designers, Wood Scientists and Technologists Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Three journal articles What do you plan to do during the next reporting period to accomplish the goals? Objective 1 has been partially completed, i.e., we have a practical 3D model but not of a real full-size, wood-frame, residential structure with a realistic, complex geometry. We have a model which has been verified by a lab-test house. The next step is to model a full-size, wood-frame, residential structure with a realistic, complex geometry.
Impacts
What was accomplished under these goals?
The practical modeling methods developed by Martin (2010) were used to develop a three-dimensional structural model of the L-shaped house constructed and tested by Paevere (2002) in Australia. The model was fully developed using the commercial software package: SAP2000 (2012) Version 14. After verification of the model, the full house model was used to explore load paths and system behavior within the structure under various load cases. Next, a timber frame (TF) and a light frame (LF) buildings were used to model load paths. Modeling methods developed by Martin et al. (2011) and further developed and validated by Pfretzschner et al. (2013) were used for the creation of structural models. Models for each framing system (LF and TF) were created using SAP2000 (2012) structural analysis software, and load paths generated by applied design loads were investigated and compared. Both structures were modeled with and without openings (doors and windows), and comparisons were made based on resistance to uplift, story drift and twisting, the addition of large openings, a break in load path, and the relative ranges of axial loads in posts and studs. Results showed that the effects of adding re-entrant corners and wall openings on uplift load distributions were dependent on the orientation of the trusses with respect to the walls. Openings added to walls parallel to the trusses had the least effect on loads carried by the remaining walls in the building. Varying re-entrant corner dimensions of the L-shaped house under ASCE 7-05 (ASCE 2005) design wind loads caused increasing degrees of torsion throughout the house, depending on the relative location and stiffness of the in-plane walls (parallel to the applied wind loads) as well as the assumed direction of the wind loads. Balancing the stiffness of the walls on either side of the house with the largest re-entrant corner helped to decrease torsion in the structure somewhat. Results also showed that the TF outperforms the LF in resisting uplift, as well as in story drift. The TF also provided load paths that are more resilient to the introduction to large openings and the loss of a central post. Observed axial loads in posts showed smaller ranges compared to LF studs. Specific objectives of the proposed project are: 1. Develop a practical 3D computer model of a full-size, wood-frame, residential structure with a realistic, complex geometry. 2. Evaluate critical load paths and system effects under various extreme (e.g., wind – hurricanes & tornados and seismic) loading scenarios. Examine load concentration effects of the complex-plan-geometry structure. 3. Develop design guidelines for the disaster resistance housing.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2013
Citation:
Malone, B., Gupta, R., Miller, T.H., and Puettmann, M. 2013 ENVIRONMENTAL IMPACT ASSESSMENT OF LIGHT-FRAME AND TIMBER FRAME BUILDINGS. J. of Green Buildings (in-press)
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Malone, B., Gupta, R., and Miller, T.H. 2013 Gravity and wind load path analysis of a light-frame and a traditional timber frame building. Journal of Performance of Constructed Facilities (in-press, posted online on September 26, 2013. doi:10.1061/(ASCE)AE.1943-5568.0000136 )
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Pfretzschner, K., Gupta, R. and Miller, T.H. 2013 Practical Modeling for Load Paths in a Realistic, Light-Frame Wood House. J. of Performance of Constructed Facilities, (in press, posted online on February 27, 2013. doi:10.1061/(ASCE)CF.1943-5509.0000448)
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: The objective of this study is to develop and validate practical modeling methods for investigating load paths and system behavior in a realistic, light-frame wood structure. The activities included modeling an L-shape house. The modeling methods were validated against full-scale tests on sub-assemblies and an L-shaped house. The model of the L-shaped house was then modified and used to investigate the effects of re-entrant corners, wall openings and gable-end retrofits on system behavior and load paths. PARTICIPANTS: Rakesh Gupta, Kathryn Pfretzschner and Thomas Miller, Oregon State University. TARGET AUDIENCES: Structural Engineers, Home Builders, Building Contractors. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The following change in knowledge occurred as a results from the load path investigations in a realistic, light-frame wood structure: The study showed that the effects of adding re-entrant corners and wall openings on uplift load distributions were dependent on the orientation of the trusses with respect to the walls. Openings added to walls parallel to the trusses had the least effect on loads carried by the remaining walls in the building. Varying re-entrant corner dimensions of the L-shaped house under ASCE 7-05 design wind loads caused increasing degrees of torsion throughout the house, depending on the relative location and stiffness of the in-plane walls (parallel to the applied wind loads) as well as the assumed direction of the wind loads. Balancing the stiffness of the walls on either side of the house with the largest re-entrant corner helped to decrease torsion in the structure somewhat. Finally, although previous full-scale tests on gable-end sections verified the effectiveness of the gable-end retrofit that was recently adopted into the 2010 Florida building code, questions remained about the effects of the retrofit on torsion in a full building. The current study found that adding the gable-end retrofits to the L-shaped house did not cause additional torsion.
Publications
- No publications reported this period
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