مطالعه تجربي مقاومت خمشي تير لايه اي (گلولام) ساخته شده از گونه صنوبر با اتصال دهنده هاي مكانيكي و مقايسه آنها با گلولام ساخته شده با پرس سرد

Experimental study on flexural performance of poplar glued-laminated timber constructed by mechanical fastener and comparing them with those made with cold press

اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﺑﺎ ﻫﺪف ﺑﺮرﺳﯽ ﻣﻘﺎوﻣﺖ ﺧﻤﺸﯽ )MOR( و ﻣﺪول اﻻﺳﺘﯿﺴﯿﺘﻪ ﺧﻤﺸﯽ )MOE( ﺗﯿﺮ ﻻﯾﻪاي )ﮔﻠﻮﻻم( ﺳﺎﺧﺘﻪ ﺷﺪه از ﺻﻨﻮﺑﺮ )Populus alba( ﺑﺎ اﺗﺼﺎل-دﻫﻨﺪهﻫﺎي ﻣﮑﺎﻧﯿﮑﯽ ﻣﺎﻧﻨﺪ ﻣﯿﺦ ﻓﻮﻻدي ﮔﺎﻟﻮاﻧﯿﺰه، ﻣﯿﺦ ﺷﺎﻧﻪاي و ﭘﯿﭻ ﭘﺎﻧﻠﯽ رزوه درﺷﺖ و ﻧﯿﺰ ﺑﺎ و ﺑﺪون ﭼﺴﺐ و ﻣﻘﺎﯾﺴﻪ آﻧﻬﺎ ﺑﺎ ﮔﻠﻮﻻم ﺳﺎﺧﺘﻪ ﺷﺪه ﺑﺎ ﭘﺮس ﺳﺮد اﻧﺠﺎم ﺷﺪ. ﭼﺴﺐ ﻣﻮرد اﺳﺘﻔﺎده ﭘﻠﯽاورﺗﺎن و ﻣﻘﺪار ﻣﺼﺮف آنg/m2 300 ﺑﻮد. ﺿﺨﺎﻣﺖ، ﭘﻬﻨﺎ و ﻃﻮل دﻫﺎﻧﻪ ﮔﻠﻮﻻمﻫﺎي ﺳﻪﻻﯾﻪ ﺑﺮاي آزﻣﻮن ﺧﻤﺶ ﺑﻪﺗﺮﺗﯿﺐ 80 ،57 و mm 640 ﺑﻮد. آزﻣﻮن ﺧﻤﺶ ﺑﺮاﺳﺎس ASTM D7341 و ﺑﺎ دﺳﺘﮕﺎه اﯾﻨﺴﺘﺮون اﻧﺠﺎم ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺑﯿﺸﺘﺮﯾﻦ MOR و MOE ﺑﻪﺗﺮﺗﯿﺐ ﻣﺮﺑﻮط ﺑﻪ ﮔﻠﻮﻻمﻫﺎي ﺳﺎﺧﺘﻪ ﺷﺪه ﺑﺎ ﭼﻬﺎر ﻋﺪد ﭘﯿﭻ در ﺳﻄﺢ cm2×8 8 ﺑﻪ ﻫﻤﺮاه ﭼﺴﺐ )MPa 69/3( و دو ﻋﺪد ﻣﯿﺦ ﻓﻮﻻدي ﺑﻪ ﻫﻤﺮاه ﭼﺴﺐ )MPa 6737/7( ﺑﻮد. ﻫﻤﭽﻨﯿﻦ ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﮐﻤﺘﺮﯾﻦ MOR و MOE ﻫﺮدو ﻣﺮﺑﻮط ﺑﻪ ﮔﻠﻮﻻمﻫﺎي ﺳﺎﺧﺘﻪ ﺷﺪه ﺑﺎ دو ﻋﺪد ﻣﯿﺦ ﺷﺎﻧﻪاي ﺑﺪون ﭼﺴﺐ ﺑﻮد )ﺑﻪﺗﺮﺗﯿﺐ 23/9 و MPa 1252/7(. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺑﺎ ﺗﻐﯿﯿﺮ ﻣﺴﺘﻘﻞ ﺗﻌﺪاد اﺗﺼﺎلدﻫﻨﺪه MOR و MOE ﺑﻪﺗﺮﺗﯿﺐ 3/7 و ﮐﻤﺘﺮ از ﯾﮏ درﺻﺪ ﺗﻐﯿﯿﺮ ﮐﺮد. ﺑﯿﺸﺘﺮﯾﻦ ﺗﻐﯿﯿﺮات ﻣﺮﺑﻮط ﺑﻪ ﺗﺎﺛﯿﺮ ﻣﺴﺘﻘﻞ ﮐﺎرﺑﺮد ﭼﺴﺐ ﺑﻮده اﺳﺖ )130درﺻﺪ ﺑﺮاي MOR و 317/8 درﺻﺪ ﺑﺮاي MOE(. ﺗﺠﺰﯾﻪ و ﺗﺤﻠﯿﻞ آﻣﺎري ﻧﺸﺎن داد ﮐﻪ ﻓﻘﻂ ﺗﺄﺛﯿﺮ ﻣﺴﺘﻘﻞ ﮐﺎرﺑﺮد ﭼﺴﺐ ﺑﺮ MOR و MOE در ﺳﻄﺢ اﻋﺘﻤﺎد 95درﺻﺪ از ﻧﻈﺮ آﻣﺎري ﻣﻌﻨﯽدار اﺳﺖ. ﻧﺘﺎﯾﺞ ﻣﻘﺎﯾﺴﻪ MOR و MOE ﮔﻠﻮﻻمﻫﺎي ﺳﺎﺧﺘﻪ ﺷﺪه ﺑﺎ ﺗﯿﻤﺎرﻫﺎي ﺳﺎﺧﺘﻪ ﺷﺪه ﺑﺎ دو اﺗﺼﺎلدﻫﻨﺪه و ﭼﺴﺐ در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﭘﺮس ﺳﺮد ﻧﺸﺎن داد ﮐﻪ ﻫﯿﭻ اﺧﺘﻼف ﻣﻌﻨﯽداري ﺑﯿﻦ آﻧﻬﺎ وﺟﻮد ﻧﺪارد، ازاﯾﻦرو، ﻣﯽﺗﻮان از ﭘﯿﭻ، ﻣﯿﺦ ﻓﻮﻻدي و ﺷﺎﻧﻪاي ﺑﺮاي ﺳﺎﺧﺖ ﮔﻠﻮﻻم اﺳﺘﻔﺎده ﮐﺮد، ﮐﻪ از ﺑﯿﻦ آﻧﻬﺎ ﻣﯿﺦﺷﺎﻧﻪاي ﺑﻪ دﻟﯿﻞ ﺳﻬﻮﻟﺖ ﮐﺎرﺑﺮد و ﻧﺼﺐ آن ﺑﺎ ﻣﯿﺨﮑﻮب ﺑﺎدي و ﻫﺰﯾﻨﻪ ﮐﻤﺘﺮ ﺑﻬﺘﺮﯾﻦ ﮔﺰﯾﻨﻪ اﺳﺖ.

In this study, modulus of rupture (MOR) and modulus of elasticity (MOE) of glued-laminated timber (Glulam) made out of poplar (Populus alba) with galvanized steel nail, brad strip nail, coarse thread drywall screw for applying pressure were investigated and compared with those constructed with cold press. Amount of polyurethane adhesive was 300 g/m2. Thickness, width and span of 3-ply glulam specimens were 57, 80 and 640 mm, respectively. Static bending test was performed according to ASTM D 7341 by Instron testing machine. The results showed that the higher MOR and MOE were related to Glulam connected by 4 screws on 8×8 cm2 with adhesive (69.3 MPa), and those connected by 2 galvanized steel nail with adhesive (6737.7 MPa), respectively. The results also revealed that the lower MOR and MOE were both observed in Glulam connected by 2 brad strip nail without any adhesive (23.9 and 1252.7 MPa, respectively). The results showed that MOR and MOE of glulam were changed with the independent variation of number of fastener 3.7 and ˂1%, respectively. The higher variation was related to independent effect of adhesive (130 and 317.8% for MOR and MOE, respectively). Analysis of variance indicated that only the independent effect of adhesive application was only statistically significant at 95% confidence level. The comparison of MOR and MOE of Glulam made with two fasteners with those constructed by cold press showed that there was not significant difference between them. So, the use of galvanized steel nail, brad strip nail, coarse thread drywall screw for applying pressure to manufacture Glulam instead of cold press is possible and the best item was brad strip nail due to easy application and installation by pneumatic nailer and low cost.