تأثیر تقویت‌کنندۀ ورق فولاد گالوانیزه، آلومینیوم و الیاف شیشه بر عملکرد خمشی گلولام ساخته‌شده از صنوبر با اتصال‌دهندۀ پیچ

نوع مقاله: مقاله پژوهشی

نویسنده

استادیار گروه منابع طبیعی، دانشکدۀ کشاورزی و منابع طبیعی، دانشگاه محقق اردبیلی، اردبیل، ایران

چکیده

هدف این تحقیق، تقویت عملکرد خمشی گلولام ساخته‌شده از صنوبر (Populus alba) و پیچ بود. برای ساخت گلولام سه‌لایه از چسب پلی‌اورتان برای اتصال لایه‌ها و پیچ برای اعمال فشار استفاده شد. متغیرهای بررسی‌شده شامل نوع تقویت‌کننده (ورق آلومینیوم، فولاد گالوانیزه و الیاف شیشه) و آرایش قرارگیری تقویت‌کننده (آرایش 1 (در قسمت پایین (کششی))، آرایش 2 (در قسمت پایین (کششی) و بالا (فشاری))، آرایش 3 (در پایین، بالا و بین دو لایۀ پایین) و آرایش 4 (در پایین، بالا و بین لایه‌ها) بودند. آزمون خمش با ASTM D7341 و دستگاه اینسترون انجام گرفت. بیشترین مدول گسیختگی (MOR) (MPa 96/82) و مدول الاستیسیته (MOE) (MPa 33/10166) در گلولام‌های تقویت‌شده با ورق فولاد گالوانیزه با آرایش 2 و کمترین MOR (MPa 82/57) و MOE (MPa 33/4397) نیز در گلولام‌های تقویت‌شده با الیاف شیشه با آرایش 1 مشاهده شد. MOR و MOE گلولام شاهد به‌ترتیب 1/48 و MPa 4330 بود. مقدار افزایش MOR در نمونه‌های تقویت‌شده با ورق فولاد گالوانیزه، ورق آلومینیوم و الیاف شیشه نسبت به نمونه‌های شاهد به‌ترتیب 5/72، 8/57 و 6/42 درصد بود. این مقدار افزایش برای MOE به‌ترتیب 8/134، 6/57 و 4/28 درصد بود. با کاربرد تقویت‌کننده تردشکنی به شکست نرم تغییر می‌کند و خواص خمشی بهبود می‌یابد. نتایج نشان داد که تأثیر مستقل نوع و آرایش تقویت‌کننده بر MOR و MOE و همچنین تأثیر متقابل آنها بر MOE در سطح اعتماد 95 درصد از نظر آماری معنی‌دار است.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of reinforcement of the galvanized steel, Aluminum sheet and Glass fiber reinforcement polymer wrapped on flexural behavior of screwed glued laminated timber (glulam) made with poplar

نویسنده [English]

  • Akbar Rostampour Haftkhani
Assist. Prof., Department of Natural Resources, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, I.R. Iran
چکیده [English]

The aim of this study was to investigate flexural strengthening of screwed Glulam made with poplar (Populus alba). Polyurethane adhesive and screw were used for joining layers and applying pressure for manufacturing of three-layer glulam. The variables of this study were types of reinforcing (galvanized steel, aluminum sheet and glass fiber reinforcement polymer) and arrangements of reinforcing: No. 1 (bonded on the bottom (tension) side); No. 2 (bonded on the bottom and top (Tension and compression) side); No. 3 (bonded on the bottom, top and between two bottom layers); No. 4 (bonded on the bottom, top and among layers). Bending test was conducted by Instron according to ASTM D7341. The highest MOR (82.96 MPa) and MOE (1066.33 MPa) were both observed in Glulams reinforced by galvanized steel sheet with arrangement of No. 2 and the lowest MOR (57.82 MPa) and MOE (4397.33 MPa) were both related to Glulams reinforced by GFRP wrapped with arrangement of No. 1. MOR and MOE of control Glulams were 48.1 and 4330 MPa. The increasing percentage of MOR due to reinforcing by galvanized steel, aluminum sheet and GFRP Wrapped were 72.5, 57.8 and 42.6, respectively. The increasing percentages for MOE were 134.2, 57.6 and 28.4, respectively. Failure modes of Glulams changed from brittle to ductile by reinforcing resulted in improving of flexural behavior. The independent effect of types and arrangements of reinforcing on MOR and MOE and also the interaction of types and arrangements of reinforcing on MOE were statistically significant.

کلیدواژه‌ها [English]

  • Flexural behavior reinforcement
  • Glued laminated timber (Glulam)
  • Aluminum Sheet
  • Galvanized steel sheet
  • GFRP wrapped
[1]. BS EN 301. (2013). Adhesives, Phenolic and Aminoplastic, for Load-Bearing Timber Structures-Classification and Performance Requirements. British Standards Institution.

[2]. Gagnon, S., and Pirvu, C. (2011). CLT handbook: cross-laminated timber. FPInnovations.

[3]. Eckelman, C. A. (2003). Textbook of Product Engineering and Strength Design of Furniture, Purdue University, West Lafayette, Indiana, 65-67.

[4]. BS EN 338:2009. Structural timber. Strength classes.

[5]. BS EN 1992-1-1. Eurocode 2. Design of concrete structures.

[6]. EN 1993-1-1. Eurocode 3: Design of Steel Structures.

[7]. Kliger, I.R., Haghani, R., Brunner, M., Harte, A.M., and Schober, K.U. (2016). Wood-based beams strengthened with FRP laminates: improved performance with pre-stressed systems. European Journal of Wood and Wood Products, 74(3): 319-330.

[8]. Coleman, G., and Hurst, H. (1974). Timber structures reinforced with light gage steel. Forest Products Journal, 24: 45-53.

[9]. Alam, P., and Ansell, M. (2012). The effects of varying nailing density upon the flexural properties of flitch beams. Journal of Civil Engineering Research, 2(1): 7-13.

[10]. Nowak, T.P., Jasieńko, J., and Czepiżak, D. (2013). Experimental tests and numerical analysis of historic bent timber elements reinforced with CFRP strips. Construction and Building Materials, 40: 197-206.

[11]. Ansell, M. P. (2015). Wood Composites, Woodhead Publishing.

[12]. Nowak, T., Jasieńko, J., Kotwica, E., and Krzosek, S. (2016). Strength enhancement of timber beams using steel plates–review and experimental tests. Drewno, 59(196):75-90.

[13]. Jankowski, L.J., Jasieńko, J., and Nowak, T.P. (2010). Experimental assessment of CFRP reinforced wooden beams by 4-point bending tests and photoelastic coating technique. Materials and Structures, 43(1):141-150.

[14]. Jasienko, J. (2001). Glue joints used for reinforcing the damaged ends of wooden beams. Structural Engineering International, 11(4): 246-250.

[15]. Raftery, G.M., and Harte, A.M. (2011). Low-grade glued laminated timber reinforced with FRP plate. Composites Part B: Engineering, 42(4): 724-735.

[16]. Standard method of testing small clear specimens of timber. Annual Book of ASTM Standard, 04.10, D 143. 2018.

[17]. Standard Practice for Establishing Characteristic Values for Flexural Properties of Structural Glued Laminated Timber by Full-Scale Testing. Annual Book of ASTM Standard, 04.10, D 7341, 2018.

[18]. Franke, S., Franke, B., and Harte, A.M. (2015). Failure modes and reinforcement techniques for timber beams-State of the art. Construction and Building Materials, 97: 2-13.

[19]. NDS (2018). National design specification for wood construction: recommended practice for structural design.

[20]. Bergman, R., Cai, Zh., Carll, C G., Clausen, C A., Dietenberger, M A., Falk, R H., Frihart, C R., Glass, S V., Hunt, C G., Ibach, R E., Kretschmann, D E., Rammer, D R and Ross, R J. (2010). Wood handbook: Wood as an engineering material. General Technical Report FPL-GTR-190. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 508 p.