Progress 10/01/99 to 09/30/04
Outputs
In this project, we first developed testing and data acquisition system and testing procedures for full-scale post-frame buildings. Each frame is simultaneously pulled laterally to simulate wind loads. A full-scale building (40 ft wide by 80 ft long by 16 ft to eave height and 4 on 12 roof slope) was constructed and tested in various stages of construction in order to determine the contribution of the metal cladding to the stiffness of the building by diaphragm action During the tenure of this project, several tests were performed under different situations in order to generate information regarding stiffness values, effect of openings, effective bracing methods, contribution of purlins and effect of in-service conditions on roof and end-wall stiffness. Results from the full-scales tests have enabled us to predict stiffness values that can be incorporated in design of post-frame buildings. Other outcomes from this research project include 1) effectiveness of steel
strapping, plywood sheathing, and stitching of panel laps as supplemental reinforcement alternatives for end walls with large opening due to doorways, 2) determination of contribution of interior roof purlins in resisting diaphragm forces, 3) development of a predictive semi-empirical 3-dimensional stiffness model for roof diaphragms, 4) insights into the interaction between roof purlins and metal cladding, and load sharing between frames including end-wall frames, 5) we were able to address whether or not the end walls are rigid, 6) whether or not the two roof halves in a gable-type roof are continuous. In other words, does the ridge cap provide sufficient continuity in transferring shear, 7) effect of different size of openings at the end walls on stiffness of end walls, and 8) effect of in-service conditions, such as cyclic wind loading and weather conditions on the stiffness of the roof diaphragm. The project produced 16 peer-reviewed articles, two book chapters and 5 conference
technical papers over 13 years.
Impacts
Including diaphragm action in design of post-frame buildings proved to be of significant economic benefit by reducing side and embedment (foundation) requirements for side-wall posts. Our work became the basis for the development of a National ASAE Standard (ASAE Ep484.11991) on diaphragm design of metal-clad, timber-framed rectangular post-frame buildings. The principal investigator of this project has made several invited presentations at the Annual National Frame Builders Association Conference to practicing engineers, architects, contractors and builders. Therefore, many professionals are made aware of the design procedure and benefits of including diaphragm action in post-frame design. Also, software called Metclad has been developed in this study. Metclad is two-dimensional frame analysis software that includes diaphragm action in design of post-frame rectangular buildings. The software has been used for teaching, research and engineering practice throughout the
U.S. for several years now.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
In our ten-years full-scale building diaphragm testing program, we have addresses to several assumptions that are made in the analysis and design of metal-clad, timber-framed post-frame rectangular buildings. The data generated have been critical in either validating or improving some of the design assumptions and analysis procedure of this type of buildings. Some of the critical issues addressed to date include: (1) Contribution of the roof diaphragm in transferring loads to end walls, which translates into reducing the size of the sidewall posts and their embedment requirements, (2) Whether or not the end walls are rigid, (3) Whether or not the two roof-diaphragm halves in a gable-type roof are continuous. In other words, does the ridge cap provide sufficient continuity in transferring shear, (4) Effect of different sizes of openings at the end walls on stiffness of end walls, (5) Use of different supplemental reinforcement alternatives (such as (a) steel strap
cross bracing, (b) plywood sheathing, and (c) stitching end walls to regain lost stiffness from the opening, (6) Stress distribution on roof purlins, and (7) Effect of in-service conditions such as cyclic wind loading and weather conditions on the stiffness of the roof diaphragm. We did our last experiment to address #7 in 2002. Since then we have been developing mathematical models, based on constitutive equations, that will allow us to predict end-wall stiffness values and how those stiffness values change with size of opening in the end walls. We have made some progress in this effort last year but the work still continues. The models will be validated using our test results. Based on the test results, we have established that end walls are not rigid and their deflections should be taken into account in analyzing and designing diaphragms of post-frame buildings. Movement of end walls increases bending moment of sidewall posts. Therefore, not considering end-wall deflection
underestimates design. Further research is needed to determine the implications of the complete composite-action of roof diaphragms.
Impacts
The test results from our full-scale post-frame building was the basis for developing a national standard on diaphragm design of metal-clad, timber-framed rectangular post frame building by ASAE (The Society for Engineering in Agriculture, Food, and Biological Systems). The results obtained were used to refine the assumptions and design procedure of post frame buildings. The model, when completed and validated, is expected to be an alternative to an experimentally based design. It is important to note that testing full-scale buildings is an expensive enterprise.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Several assumptions have to be made when analysis is based on data from scaled-down laboratory test assemblies. Testing full-scale building diaphragm systems provide data to validate those assumptions and/or improve on them. In diaphragm design, some of the critical issues that need to be addressed include: (1)Interaction between two roof-diaphragm halves in buildings that have a gable-type roof. In other words, is shear continuous at the ridge? (2)Effect of in-service conditions such as cyclic wind loading and weather conditions on the stiffness of the roof diaphragm. (3)Modeling and testing to validate the stiffness of end walls. This includes interaction between end walls and roof diaphragm. The research work on the first two issues is completed. Contrary to previous assumptions, the ridge cap helps to transfer shear at the ridge. With the ridge cap removed, the stiffness of the roof diaphragm was 1.60 times the sum of stiffness values of the two roof halves
assumed as independent diaphragms but was less than the stiffness of the full roof when considered as a single diaphragm, spanning from eave to eave. The results related to the effect of in-service conditions on roof diaphragm stiffness have been published (see below). We have made some progress in modeling end-wall stiffness. End walls are not rigid. We have measured deflections of end walls from the full-scale tests. Movement of end walls increases bending moment of sidewall posts, which need to be considered in design of posts. The deformations of in-plane shear force and bending moment were also isolated to determine the bending stiffness of the roof diaphragm. Further research is needed to determine the implications of the complete composite-action of roof diaphragms
Impacts
The results from the full-scale post-frame building reflect that results obtained from small-scale laboratory tests simplify and in some cases compromise the actual behavior and performance of the diaphragm. Care must be exercised in analyzing and interpreting the information obtained from laboratory tests. Based on this study, it is important to learn that the stiffness of the roof diaphragm and end walls is not affected by in-service conditions within the time frame (9 years) since the building was constructed. It is also important to realize that ridge cap transfer shear along the ridge.
Publications
- Gebremedhin, K.G. 2002. Testing a full-scale building after nine years in service. Wood Design Focus - A Journal of Contemporary Wood Engineering, Volume 12(3): 20-23.
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Progress 01/01/01 to 12/31/01
Outputs
When laboratory static panel tests are used to obtain shear stiffness design values, several assumptions have to be made because the test assembly can not realistically mimic the actual behavior of the building system. Some of the assumptions and simplifications also pertain to our lack of understanding, at this point in time, of the distribution of loads in the building envelope. The assumptions and simplifications made in laboratory tests are automatically accounted for when the properties are directly obtained from full-scale building tests. Additional tests were performed to address the following specific objectives: (1) To assess whether or not in-service conditions, such as cyclic natural wind and weather effects, have caused any enlargement of the holes around connectors to affect the stiffness of the roof diaphragm during the nine-year service of the building. (2) To test the full-scale building in such a way as to produce a wide zero-shear region in the
diaphragm so that in-plane bending deformation is separated from in-plane shear deformation. (3) To determine the bending stiffness as well as the combined shear and bending stiffness of the roof diaphragm. The full-scale post-frame building was tested after being in service for nine years to determine if in-service conditions such as cyclic natural wind loading and weather conditions had an effect on the stiffness of the structural elements. The deformations of in-plane shear force and bending moment were also isolated to determine the bending stiffness of the roof diaphragm. The results reveal that there was no apparent effect of in-service conditions on the stiffness of the elements during the nine years the building has been in service. The bending stiffness of the roof diaphragm calculated from a wide shear-free region was 1,725 kN/m (9,850 lb/in.), which is around 82.5% of the combined shear and bending stiffness of the roof diaphragm. Further research is needed to determine the
implications of the complete composite-action
Impacts
The results from the full-scale post-frame building reflect that results obtained from small-scale laboratory tests simplify and may reveal the actual behavior and performance of the diaphragm. Care must be exercised in analyzing and interpreting the information obtained from laboratory tests. Based on this study, it is important to learn that the stiffness of the roof diaphragm and end walls is not affected by in-service conditions within the time frame (9 years) since the building was built.
Publications
- Gooch, C.A. and K.G. Gebremedhin. 2001. Practices that enhance post-frame construction. Frame Building News 13(4): 30-36.
- Gebremedhin, K.G. 2001. Testing a full-scale building to separate shear and bending moment stiffness values. Trans. Of ASAE (accepted).
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Progress 01/01/00 to 12/31/00
Outputs
Over the years, several tests have been performed using the full-scale post-frame building. This year, the full-scale post-frame building was tested after being in service for nine years to determine if in-service conditions such as cyclic natural wind loading and weather conditions had an effect on the stiffness of the structural elements. The results reveal that there was no apparent effect of in-service conditions on the stiffness of the elements during the nine years the building was in service. Also loading procedures were developed in order to be able to separate deformations due to in-plane shear force and bending moment. This procedure would allow determining the bending stiffness of the roof diaphragm.
Impacts
Solutions to the objectives will allow safe and reliable designs by accounting into consideration the effect of weather conditions and cyclic wind loading that the structure may be subjected to during its existence. Another benefit is to be able to design post-frame buildings as realistically as possible.
Publications
- Gebremedhin, K.G.. 2000. Testing a full-scale building to separate shear and bending moment stiffness values. Applied Journal in Agriculture (in press).
- Gebremedhin, K.G. 2000. Testing a full-scale building to separate shear and bending moment stiffness values. 2000 ASAE Annual International Meeting, Milwaukee, WI, ASAE Microfiche No. 00-4037, St. Joseph, MI.
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Progress 01/01/99 to 12/31/99
Outputs
The Cornell Full-Scale Building Testing Program, initiated in 1991, has been to date the most extensive and elaborate testing program of post-frame buildings. The test building is 40 ft wide by 80 ft long by 16 ft-3 in. to the eave height and a double pitched roof of 4 on 12 slope. Since its construction, sophisticated instrumentation and data acquisition systems have been put in place to monitor and control the hydraulic pressure applied to hydraulic jacks that pull laterally on each frame in simulating wind loads, and to record the data. Load and displacement (both deflection and rotation) transducers are placed at each frame at eave height as well as at floor level to measure forces, lateral deflections and rotations. Recently, ninety (90) strain gauges were mounted at selected strategic locations of roof purlins and metal skin to determine the strain distribution throughout the roof envelope. Control strain gauges are also installed from which transient conditions
(such as temperature) can be accounted for and appropriately adjusted from the test strain gauges. All digitized signals are recorded with an IBM PS/2 computer, and the load-displacement curve of each frame can be plotted in real-time when testing. The building has been tested at different stages of construction to determine the contribution of the different components (frame only, with end-wall cladding, with side-wall cladding, with roof sheathing, etc.) to the stiffness of the building when subjected to simulated wind loads. Stiffness values of end-wall and roof diaphragms have been determined and a three-dimensional building stiffness model has been developed. The information generated out of the Cornell Full-Scale Testing Program have been, in a major way, detrimental in the revision of the Standard (ASAE EP 484). With the data generated and models developed, we were able to validate some of the critical assumptions made in the diaphragm design procedures outlined in the
Standard. We are currently in the process of developing a procedure for predicting the end-wall from that of the stiffness of the roof diaphragm. This procedure, when completed, will simplify diaphragm design procedures in a major way because the need to test both end wall and roof diaphragm can be avoided.
Impacts
(N/A)
Publications
- Gebremedhin, K.G. and J.W. Price. 1999. Experience of a testing program of a post-frame building. Journal of Structural Engineering, Vol. 125(10):1170-1178.
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Progress 01/01/98 to 12/31/98
Outputs
The Cornell Full-Scale Building Testing Program, initiated in 1991, has been the most extensive and elaborate testing program of post-frame buildings to date. The test building is 40 ft wide by 80 ft long by 16 ft-3 in. to the eave height and a double pitched roof of 4 on 12 slope. Since its construction, sophisticated instrumentation and data acquisition systems have been put in place to monitor and control the hydraulic pressure applied to hydraulic jacks that pull laterally on each frame in simulating wind loads, and to record the data. Load and displacement (both deflection and rotation) transducers are placed at each frame at eave height as well as at floor level to measure forces, lateral deflections and rotations . Recently, we have mounted ninety (90) strain gauges at selected strategic locations of the roof purlins and metal skin to determine the strain distribution throughout the roof envelope. Control strain gauges were also installed from which transient
conditions (such as temperature) can be accounted for and appropriately adjusted from the test strain gauges. Now, all digitized signals can be recorded with an IBM PS/2 computer, and the load-displacement curve of each frame be plotted in real-time when testing. Stiffness values of end-wall and roof diaphragms have been determined based on testing the full-scale building. We still need to develop a model that predicts the stiffness of the end wall from the stiffness of the roof diaphragm so that only prototype roof diaphragms need to be tested. The information generated out of the Cornell Full-Scale Testing Program have been critical in the revision of the Standard (ASAE EP 484) underway. With the information generated and models developed, we were able to validate some of the critical assumptions made in the diaphragm design procedures outlined in the Standard. When the objectives of the proposed study are completed, the results will simplify diaphragm design procedures in a major
way.
Impacts
(N/A)
Publications
- Gebremedhin, K. G. 1998. Building to increase diaphragm strength and stiffness. Frame Building Professional, Vol 10(3):50-58.
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Progress 01/01/97 to 12/31/97
Outputs
A scaled-down (test panels) and full-scale post-frame building were extensively instrumented to determine the interaction between the wood roof framing system and the metal cladding membrane. The behavior of the full-scale building was analyzed from a global rather than from a localized viewpoint. The extensive instrumentation using strain gages to measure strain, load transducers to measure applied loads, and LVDT's to measure displacements provided insights that include: (a) contributions of interior purlins in resisting diaphragm forces, (b) interaction between the two roof halves, (c) interaction between the roof purlins and the metal cladding, and (d) load sharing between frames including end-wall frames. The interactions were captured by the development of a three-dimensional stiffness model. The model determines eave displacement of post-frame buildings based on a stiffness of a scaled-down test panel. The predicted eave displacements at different frames were
compared with measured displacements from three full-scale building tests. A procedure for estimating the upper-bound strength of a full-scale building is suggested. Results from this work provide information that would help us refine the ASAE post-frame diaphragm standard which is currently based on results from laboratory diaphragm test panels. The analytical procedure developed in this study is also the first step toward predicting diaphragm stiffness without having to conduct laboratory tests of these systems.
Impacts
(N/A)
Publications
- Niu, K.T. and K.G. Gebremedhin. 1997. Evaluation of interaction of wood framing and metal-cladding in roof diaphragms. Transactions of
- Niu, K.T. and K.G. Gebremedhin. 1997. Three-dimensional building stiffness model for post-frame buildings. Transactions of ASAE, Vol.
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Progress 01/01/96 to 12/30/96
Outputs
It might be important to mention at the outset that results from this project became the basis for revising a nationally recognized engineering practice on diaphragm design of metal-clad post-frame buildings that was developed by ASAE. Currently, diaphragm design involving metal-on-wood diaphragms is conducted according to the ASAE Engineering Practice. The Engineering Practice first published in the 1990 edition of the ASAE Standards, was initially developed based on scaled-down laboratory test panels. Data from full-scale buildings were not available to validate the assumptions made in the Engineering Practice document. A full-scale post-frame building was built and tested at different stages of construction: (1) frame only, (2) when the end walls only were sheathed, (3) when all walls were sheathed, (4) when one side of the roof was sheathed, and (5) when both sides of the roof was sheathed.
Impacts
(N/A)
Publications
- Gebremedhin, K. G., J. A. Bartsch and M. C. Jorgensen. 1992. Full-scale testing of post-frame buildings. Chapter 10, In: Post-Frame Building Design. Editors: J.N. Walker, and F. E. Woeste. ASAE Monograph, St. Joseph, MI, 189-210.
- Gebremedhin, K. G., J. A. Bartsch and M. C. Jorgensen. 1992. Full-scale testing of post-frame buildings. Chapter 10, In: Post-Frame Building Design. Editors: J.N. Walker, and F. E. Woeste. ASAE Monograph, St. Joseph, MI, 189-210.
- Gebremedhin, K. G. 1994. Design of bracing systems for end walls with doors. Frame Building News Vol. 6(4):64-70.
- Pollock, D.G., D.A. Bender and K.G. Gebremedhin. 1996. Designing for chord forces in post-frame roof diaphragms. Frame Building News, Vol. 8(5): 40-44.
- Gebremedhin, K. G. 1992. Application of diaphragm action in post-frame buildings. Wood Design Focus, Vol. 3(1):7-10.
- Gebremedhin, K. G. and H. B. Manbeck. 1992. Diaphragm design procedures for post-frame buildings. Wood Design Focus, Vol. 3(1):15-18.
- Gebremedhin, K. G., J. A. Bartsch and M. C. Jorgensen. 1992. Predicting roof diaphragm and end-wall stiffness from full-scale test results of a metal-clad post-frame building. Trans. ASAE 35(3):977-985.
- Gebremedhin, K. G., H. B. Manbeck and E. L. Bahler. 1992. Diaphragm analysis and design of post-frame buildings. Chapter 4, In: Post-Frame Building Design. Editors: J. N. Walker and F. E. Woeste. ASAE Monograph, St. Joseph, MI, 35-59
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Progress 01/01/95 to 12/30/95
Outputs
A two-dimensional analytical model was developed that extrapolates the shear stiffness of a small-scale test panel to a full-scale roof diaphragm. The two-dimensional model was then used to develop a three-dimensional building model that takes into account the interactions or load sharing between the frames, end walls and roof diaphragm. Predicted critical eave displacements using the 3-dimensional model was within 2 to 15% range of the experimental eave displacements measured from full-scale building tests conducted by us and similar data obtained from the literature. Sensitivity analyses were also performed to study the effects of varying end wall stiffness, roof diaphragm stiffness and frame stiffness on building performance as measured by eave displacements. The model is, therefore, fully validated. To the best of our knowledge, to-date, this is the only model developed that incorporates the global stiffness of the building in analyzing and designing post-frame
buildings. This inclusion substantially enhances the capacity of the building, particularly the side wall frames, to carry more loads and reduce the embedment requirements. In other words, when diaphragm action is included in design, the size of the side wall posts are significantly reduced because around 40% of the in-plane loads are transferred to the end walls by shear action. Our work in this area was the basis for the development of an ASAE Standard (ASAE EP484.1, 1991) on diaphragm design.
Impacts
(N/A)
Publications
- Niu, K.T. 1995. A semi-empirical three-dimensional stiffness model for metal-clad post-frame buildings. Unpublished Ph.D. Thesis, Agricultural and Biological Engineering Department, cornell University, Ithaca, NY.
- Niu, K.T. and K.G.Gebremedhin. 1995. A semi-empirical three-dimensional stiffness model for metal-clad post frame buildings. Paper presented at the 1995 International Summer Meeting of ASAE, Chicago, IL , June 18-23, Paper No. 95-4783.
- Gebremedhin, K.G. and F.E. Woeste. 1995. Evaluation of diaphragm design assumptions. Journal of Applied Engineering in Agriculture (submitted).
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Progress 01/01/94 to 12/30/94
Outputs
This year, we continued testing the full-scale metal-clad, post-frame building to generate data that was necessary for developing a predictive semi-empirical 3-dimensional stiffness model for roof diaphragms. The model is being developed, and calibrated based on frame and diaphragm displacements and purlin strain data. Ninety strain gauges were mounted onto the roof purlins, and a fully automated data acquisition system was developed and installed to record the building responses. Contrary to current assumptions in engineering practice, the interior roof purlins were experimentally determined to be as contributory in resisting diaphragm forces as the exterior roof purlins. The model, the only one of its kind, includes roof and end wall stiffnesses will be used in developing a simplified 2-dimensional model that could be used by practicing engineers.
Impacts
(N/A)
Publications
- GEBREMEDHIN, K.G. AND F.E. WOESTE. 1994. Evaluating diaphragm design assumptions in current engineering practice. Submitted to ASAE Applied Journal in Agriculture.
- NIU, K.T. AND K.G. GEBREMEDHIN. 1994. A semi-empirical three dimensional stiffness model for metal-clad post-frame building subjected to lateral loads. ASAE Paper No. 94-4564. Presented at the 1994 International Winter Meeting, Atlanta, GA.
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Progress 01/01/93 to 12/30/93
Outputs
We continued testing our full-scale post-frame building to further evaluate diaphragm design assumptions made in the ASAE Standard. The Standard was primarily based on our work. Results from the full-scale test have enabled us to predict stiffness of roof and endwall diaphragms so that principles of diaphragm action can accurately be incorporated in design of post-frame buildings. In addition, several lab tests were conducted so that similar predictions could be made from scaled down diaphragms. Including diaphragm design in post-frame has tremendous economic benefit by reducing member sizes of sidewall posts and embedment requirements. Results from our work this year will further refine two critical assumptions made in the current Standard which are 1) lateral deflection of endwalls can be neglected, and 2) definition of diaphragm length for stiffness calculations.
Impacts
(N/A)
Publications
- GEBREMEDHIN, K.G. AND JORGENSEN, M.C. 1993. Stiffness of post-frame building endwalls. Transactions, Amer. Soc. of Agric. Engineers 36(3):905-13.
- GEBREMEDHIN, K.G. AND WOESTE, F.E. 1993. Evaluating diaphragm design assumptions required by ASAE EP484.1. Amer. Soc. of Agric. Engineers, St. Joseph, MI. Paper 93-4548.
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Progress 01/01/92 to 12/30/92
Outputs
A full-scale post-frame building was constructed and tested in various stages ofconstruction to determine the contribution of the metal cladding to the stiffness of the building. From measured deflection data, we are now able, for the first time, to predict frame stiffness, roof diaphragm stiffness, and end wall stiffness. Including diaphragm theory in design of post-frame buildings proved to be of significant economic benefit by reducing size and embedment depth requirements for side wall posts. The effectiveness of steel strapping, plywood sheathing, and stitching of panel laps as supplemental reinforcement alternatives for end walls with large opening due to doorways was tested, analyzed and design recommendations given.
Impacts
(N/A)
Publications
- GEBREMEDHIN, K.G., BARTSCH, J.A., AND JORGENSEN, M.C. 1992. Predictingroof diaphragm and endwall stiffness from full-scale text results of a metal-clad, post-frame building. Transactions of ASAE 35(3):977-85.
- GEBREMEDHIN, K.G. AND JORGENSEN, M.C. 1992. Predictions of endwall stiffness and deflection of a full-scale post-frame building. Paper 92-4542. Submitted to Transactions of ASAE, St. Joseph, MI.
- GEBREMEDHIN, K.G. 1992. Application of diaphragm action in post-frame buildings. Wood Design Focus 3(1):7-10.
- GEBREMEDHIN, K.G. AND MANBECK, H.B. 1992. Diaphragm design procedures for post-frame buildings. Wood Design Focus 3(1):15-18.
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Progress 01/01/91 to 12/30/91
Outputs
In this project, a sophisticated testing and data-acquisition system for a full-scale building diaphragm was developed. The full-scale post-frame building was tested in stages of construction to determine the contributions of the steel cladding to the stiffness of the building. In-plane concentrated loading was applied at each interior post-frame to simulate wind loading. The building has been tested at nine construction stages. These test stages include: with no steel sheathing but with all wood framing members attached; with steel sheathing fastened to the endwalls; sidewalls; one side of the roof; both sides of the roof; without an opening; and with 25 and 50% opening (doorway) at one of the endwalls. 1) The horizontal eave deflection of the critical center post decreased by 79% when steel sheathing was fastened to the walls and one side of the roof, and 93% with both sides of the roof. 2) Fastening steel sheathing to the endwalls resulted in dramatically stiffer
endwalls. The endwalls were not rigid as are assumed in the current standard. 3) A 25% opening did not significantly affect the stiffness of the endwall but at 50%, the deflection of the endwall increased by about 87%.
Impacts
(N/A)
Publications
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