Progress 09/30/09 to 09/30/12
Outputs
OUTPUTS: During this final year of the project, one more experimental study was conducted: an undergraduate student investigated the use of epoxy adhesive as a shear connector between the wood and concrete components. The undergraduate student investigated two techniques to upgrade old floors for improved strength and stiffness by adding and bonding concrete to existing planks to form a composite deck. Three full scale wood plank-concrete composite floor decks were fabricated and tested to failure in four point bending. The three specimens differed only in the type of interfacial connector between the planking and the concrete slab. One specimen used a layer of epoxy designed to bond wet concrete to wood, another used a layer of cured epoxy as well as an evenly distributed layer of embedded aggregate, and the final specimen had no deliberate connection - this was the control specimen, which relied only on friction between the two components. In summary of the entire project for the past three years, the most significant outputs were: Three undergraduate students were trained in fabricating, testing (using a universal testing machine) and analyzing WCC specimens for truss plate shear strength and stiffness, effect of gap size and epoxy connection performance. One graduate student was trained in data synthesis, statistical analysis and Finite Element modeling. Two students were given experience in communicating their research through papers and presentations. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Professional engineers, architects, builders, building inspectors, and the light-frame construction industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The outcome of this year's study was the finding that significant increases in both strength and stiffness of historic mill floor systems are possible. This result is significant because it brings new and innovative options to the design community to renovate old mill buildings, as opposed to alternative retrofit methods, such as re-building new or renovating with steel. One key advantage to implementing wood-concrete composites in this manner, is that it provides a historically sensitive solution, limiting the changes in look and feel to that of the original building. In summary of the entire three year project, the techniques developed in this project move designers closer to implementation of an optimized connection system for residential or industrial floor systems with full composite action. The numerical simulation study proved successful in modeling the metal shear connector as validated by comparison of load-displacement data with experimental tests. This is important because it is necessary to be able to use computational methods to predict the composite behavior in alternative beam configurations.
Publications
- Beauregard, E.; Clouston, PL.; Arwade, SR. Finite Element Analysis of Wood-Concrete Composite with Continuous Metal Connector. 66th International Forest Products Society Convention. Washington DC, June 4-7, 2012 pp. 1-8
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: During this past year, two separate activities were carried out: one experimental study was conducted by an undergraduate student and a Finite Element Model was created by one Masters student. They were both trained and mentored in conducting experimental and analytical research as follows: 1) The experimental investigation involved an undergraduate student who explored the implications of gap size (needed to support the permanent plywood formwork) between the concrete slab and LVL. Sixty test specimens were fabricated to compare a standard truss plate and a custom truss plate for use as shear connectors. Each truss plate was tested in standard push-out tests using 1.9E Laminated Veneer Lumber. Each plate was tested thirty times; ten specimens with a 0" space between the two pieces of wood, ten specimens with 0.5 inch space, and ten specimens with 0.75 inch space. The results from these shear tests determined which truss plate would be more successful as a shear connector, and what amount of space between the wood beams and concrete floor would provide the best results. 2) The second study involved a Masters student who developed a Finite Element (FE) model of a Wood-concrete composite beam using one row of metal plates as shear connectors. The FE model was 2 dimensional and used ADYNA commercial software and assumed spring connections along the interface between the concrete and the LVL beams. The analysis was pseudo-empirical in that it used the slip modulus from previous push-out tests to predict mechanical behavior of full-scale beams in four-point bending. The results were compared to experimental test results to validate the model. PARTICIPANTS: Principal investigators Peggi L. Clouston and Alexander C. Schreyer managed and educated the undergraduate and graduate students involved in the work. TARGET AUDIENCES: The target audience is professional engineers, architects, builders, building inspectors, and the light-frame construction industry. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Several outcomes have resulted from these studies. The students involved were trained in using a universal testing machine, and were given skills in communicating science and using descriptive statistics for data analysis, as well as a commercial FE software. It was discovered from the first experiment that type A truss plates had a higher slip modulus for all three gap spacings. In each case, the type A slip moduli were about 20N/mm/mm greater than the Type B truss plates slip moduli. The average peak load was also greater in the type A tests than in the Type B tests. Even with the 0.75 inch gap, the type A tests had a greater average peak load than the type B test with no gap. Overall, it seemed that the type A truss plates created a stiffer connection and could support more load than the type B plates. This result is significant because it brings the researchers closer to developing an optimized plate with full composite action. The analytical study proved successful in modeling the shear connector as validated by comparison of load-displacement data with experimental tests. This is important because it is necessary to be able to use computational methods to predict the composite behavior in alternative beam configurations.
Publications
- Clouston, P.; Schreyer, A. Truss plates for use as shear connectors in laminated veneer lumber concrete composite systems. Structures Congress proceedings. Las Vegas, April 14-16, 2011
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: Over the past year, two undergraduate students and one Masters student were trained and mentored in conducting and analyzing three experimental studies as follows: 1) The first experimental investigation was conducted to determine the shear slip and strength properties of MT20 steel truss plates when connected to lumber with load parallel to the grain. Four types of shear specimens were fabricated: two types made from 2 pieces of 38mm wide No. 2 or better Spruce-Pine-Fir (SPF) (piece dimensions of 114mm x 152mm and 89mm x 178mm) and two types made from 44.5mm Eastern Pine Laminated Veneer Lumber (LVL) (piece dimensions of 121mm x 152mm and 89mm x 178mm). The two pieces of each lumber material were sandwiched between and connected by two MT20 truss plates with slots parallel [0degrees] and slots perpendicular [90degrees] to the longitudinal direction of the wood. The plates were installed through static pressing of up to 200kN force using steel bearing plates and a universal testing machine. 2) The second experiment entailed fabricating and testing five push-out specimens. Each specimen was made from two pieces of 44mm x 133mm x 330mm Eastern species LVL, 19mm thick plywood, a 102mm x 102mm wire mesh against concrete shrinkage, two pieces of 152mm x 305mm MT20 truss plates with one half the width (76mm) pressed into the LVL and the other embedded into a concrete slab with dimensions 89mm x 305mm x 330mm. These specimens were subjected to shear load to establish slip-modulus and ultimate shear capacity of the truss plates when used in a wood-concrete assembly. 3) The third study entailed fabricating and testing two T-beams in bending to investigate overall composite bending stiffness and strength. One beam employed two continuous rows of truss plates and the other employed only one row. Both T-beams were fabricated from two 44mm wide x 133mm deep x 2743mm long LVL beams (the same as for the push-out tests) with a separating 19mm layer of plywood covered by a 89mm thick x 457mm wide x 2743mm long concrete slab. The tests and results are being prepared for publication in the ASTM Journal of Testing and Evaluation. Also, one Abstract has been accepted for oral presentation and accompanying conference paper at the Structures Congress - Las Vegas, April 14-16, 2011. PARTICIPANTS: Principal investigators Peggi L. Clouston and Alexander C. Schreyer managed and educated the undergraduate and graduate students involved in the work. TARGET AUDIENCES: The target audience is professional engineers, architects, builders, building inspectors, and the light-frame construction industry. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Several outcomes have resulted from the experimental studies. In all three studies, the students involved were trained in using a universal testing machine and were given skills in communicating science and using descriptive statistics for data analysis. It was learned from the first experiment that truss plates would perform in the elastic range marginally better using LVL for wood-concrete composite beams than using SPF lumber. From the second experiment, two composite properties necessary for structural design of an LVL - concrete composite were evaluated: the slip modulus and truss plate capacity. The values obtained indicated excellent ductility and strength, showing good promise of this new technology being adopted for light-frame construction. The third study confirmed the hypothesis that two rows of plate connectors improved beam strength but indicated no distinct difference between initial elastic stiffness of the two beam assemblies. This result is significant because it provides insight into the failure mechanism of the composite. It also indicates that less steel can be used in the composite (improving cost and environmental impact) without effecting beam performance in the linear-elastic working range of the member.
Publications
- No publications reported this period
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