Week  3  Journal  Wenjie  Cai    

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In  week  3  studio,  we  were  doing  works  as  groups  of  three  to  build  a  beam  and  make  as  strong  as  we  can  to  suffer  load.  I  am  in  Group  3  and  the  materials  that  provided  to  us  are  one  ply  (1200  x  3.2  x  90  mm),  three  pines  (1200  x  35  x  35mm)  and  several  tools  (figure  1).  

 figure  1:  Materials  for  building  beam  

(author)  During  our  planning,  we  think  that  our  pines  are  strong  enough  to  support  heavy  load.  Therefore,  our  first  step  of  building  our  beam  was  to  nail  two  pines  on  the  same  surface  of  the  ply  with  6  nails  to  make  it  as  a  simple  frame  (figure  2  &  3).  Before  we  nailed  them  together,  we  cut  the  ply  to  make  it  shorter  so  that  we  could  use  fewer  nails  to  make  the  fixed.  

 figure  2:  first  step  of  constructing  

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(author)  

 figure  3:  Structure  of  the  frame  

(author)  In  this  type  of  structure,  using  two  pines  is  better  as  they  can  share  the  heavy  loads  and  separate  the  stress  into  the  both  side  of  the  ply  instead  of  concentrating  them  in  the  middle.  This  structure  strengthens  the  ability  of  the  beam  to  carry  load.      At  the  second  stage  of  constructing,  we  use  the  extra  ply  that  was  cut  in  the  first  step  to  strengthen  the  beam.  We  cut  it  into  several  little  equal  pieces  and  so  did  the  other  pine  that  was  not  used  (figure  4).    

 

figure  4:  example  of  cutting  the  materials  (author)  

We  filled  some  of  the  little  pieces  of  pine  in  the  gap  between  two  long  pines  of  the  beam  (figure  5).  We  also  used  the  little  pieces  of  ply  to  cover  the  pines  and  nailed  the  ply  with  the  beam  with  two  nails  for  each  (figure  6).  

 

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figure  5:  little  piece  of  pine  in  the  gap  (author)  

 figure  6:  usage  of  the  little  pieces  of  ply  

(author)  As  I  mentioned,  the  purpose  of  this  structure  is  to  strengthen  the  beam.  These  little  pieces  of  pine  were  used  to  support  the  long  ply  so  that  it  would  not  be  broken  easily.  The  little  pieces  of  ply  were  used  to  make  the  little  pieces  of  pine  fixed  so  that  they  can  play  their  important  role.  If  we  did  not  use  the  little  pieces  of  ply,  the  pines  would  easily  fall  and  could  not  support  the  beam.  These  materials  also  used  to  connect  every  part  of  the  beam  so  that  they  have  stronger  connection  and  share  the  loads  equally.  After  finishing  this  step,  the  whole  construction  of  the  beam  was  completed  (figure  7).  

 

figure  7:  Complete  beam  

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(author)    During  testing  the  beam’s  strength,  we  decided  to  put  it  at  a  position  that  the  surface  the  ply  faced  up.  However,  we  realize  that  the  ply  may  be  easily  broken  because  the  pines  are  not  flexible  and  the  ply  is  too  thin.  When  the  heavy  loads  push  on  them,  the  strong  depression  may  break  the  beam  (figure  9).  Pines  may  be  stronger  to  suffer  the  loads  and  the  ply  was  flexible  enough  to  support  the  two  pines  so  we  put  the  beam  in  opposite  position  (figure  8).  

 figure  8:  different  positions  of  putting  the  beam  

(author)  

 figure  9:  Possibilities  of  different  positions  

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(author)  The  same  as  our  estimates,  the  pines  were  very  strong  and  the  ply  was  flexible  enough.  The  beam  was  very  strong  that  it  was  hard  to  be  broken.  When  is  was  nearly  reach  the  bottom,  we  heard  sound  of  cracking.  When  we  looked  at  it  carefully,  we  could  only  see  it  cracked  a  little  bit  in  one  of  the  pines  (the  red  circle  in  figure  10).  

 figure  10:  Cracking  of  the  pine  

(author)    We  also  test  it  in  another  position  as  figure  11  shown.  The  results  of  it  was  that  one  of  the  nails,  which  was  used  to  nail  the  little  pieces  of  ply,  was  broken  and  the  pines  were  broken  (figure  12).  

 

figure  11:  Second  test  of  the  beam  (author)  

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figure  12:  Breaking  pines  (author)  

From  figure  12,  we  can  see  that  the  upper  one  was  broken  more  serious  than  the  lower  one  as  it  suffer  more  loads.  While  we  were  building  this  beam,  we  did  not  put  the  little  pieces  of  pine  into  the  middle  of  the  beam.  Therefore,  when  the  forces  acted  on  the  upper  pine,  there  was  nothing  to  support  it.  It  was  broken  easily  without  support  and  then  cause  the  lower  one  to  break.  If  we  put  one  more  little  piece  of  pine  in  the  middle  of  the  beam,  the  upper  pine  would  be  supported  and  these  two  pines  would  share  the  forces  so  they  would  not  be  broken  so  easily  (figure  13).  

 figure  13:  Beam  with  support  by  little  pieces  of  pine  

(author)  In  conclusion,  in  this  week’s  studio,  I  learn  that  materials  are  very  important  for  building  a  beam.  Strong  materials  such  as  the  pines  (1200  x  35  x  35  mm)  make  the  whole  structure  stronger.  Also,  sharing  forces  between  every  part  of  the  beam  is  very  important  as  well.  Only  one  of  its  parts  is  impossible  to  support  the  loads  on  the  whole  beam.  Every  piece  of  materials  is  important  in  sharing  load.  

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CONSTRUCTING ENVIRONMENTS

ENVS10003

ACTIVITY_CONSTRUCTION WORKSHOP

NAME GROUP MEMBERS 1_DESCRIPTION (length, width, depth, composition and structural properties) AND PHOTO OF ALL MATERIALS PROVIDED

Length 1200mm, width 35mm, depth 35mm pine x 3 Length 1200mm, width 90mm, depth 3.2mm ply x 1

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2_PHOTO AND DESCRIPTION OF ALL TOOLS USED 2 hammers, 1 try-square, 1 saw, several nails,

3_SKETCH OF YOUR DESIGN AND PHOTOS OF ALL FOUR DESIGNS Our Group’s:

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Other 4 groups’:

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4_PHOTO AND DESCRIPTION OF STRUCTURAL PERFORMANCE AND FAILURE MECHANISM OF ALL FOUR DESIGNS

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1. One 1200mm x 42mm x 18mm pine in the middle, four 600mm x 90mm x 3.2mm ply nailed on

both side of the middle pine. Several little pieces of pine are nailed beside the middle pine, which is the gap between the other thin plies. It was being put in a vertical position. Easily be broken because of the weakness of the plies. Too many nails become a problem for this design. Nails make the structure weaker.

2. Two 1200mm x 90mm x 3.2mm plies were nailed together. A 1200mm x 42mm x 18mm pine nailed on one side of the nailed-plies. Two short pines with 42mm width & 18mm depth were nailed either on the top or the bottom of the middle of the beam. Very flexible materials and stronger support in the middle. Therefore, it was not broken even if it reached the bottom.

3. Two 1200mm x 42mm x 18mm pine were nailed on one surface of the 1200mm x 90mm x 3.2 mm ply. Four little pieces of pine were filled in the gap between the two long pines to support them. It was put in vertical position that is similar with the first design and it also had the same problem with the first design – the ply was too weak in this position. Therefore, it was broken easily.

4. It was designed as a truss. The 1200mm x 90mm x 3.2mm plies were used as the top and the bottom of the truss. The cut-pines were used in the middle to form several triangle structures. The pines have transferred the load so that the load was not concentrate only in the middle of the beam. It was broken because of the break of the nail. The middle-structure was separated with the bottom.

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5. Our groups design used two 1200mm x 35mm x 35mm pines to nail with the 1000mm x 90mm x 3.2mm ply. Four little pieces of pines were used to fill in the gap between the two long pines. Four little pieces of plies were used to cover and support the pines in the gap and strengthen the connection of the two long pines.

5_DESCRIPTION/DEFINITION OF THE FOLLOWING KEY CONCEPTS Span_ The distance between two vertical support of a horizontal structure. Cross Section_ Something that is cut straight through a material Strength_ The ability of a material/structure/construction of carrying loads. Compression_ A force that compress on something Tension_ A force that pull the material apart Flexion_ The action of being bent but not be broken. Shear_ It happens when two touched surfaces shift in opposite direction Deflection_ Buckling_ A material attached to a strap. 6_EXTRA NOTES AND COMMENTS