Lecture 20 - Page 1 of 13 Lecture 20 – Computer Structural Analysis using “STAAD” BACKGROUND: Structural analysis by hand methods is feasible only for relatively simple structural members such as simply-supported beams and other 2-dimensional statically determinate frames. The real world, however, is much more complex and is composed of structures having multiple stories and supports, trusses, space frames, flat plates, arches, etc. Prior to the advent of digital computers in the 1960s, the analysis of these structures was most likely performed by “approximate” methods (such as moment distribution and portal analysis), or more rigorous exact methods involving applications of matrix and differential math. Originally, computer structural analysis was developed by mechanical and aerospace engineers for the airplane industry to calculate stresses on the wings and fuselage. Over the years, software was further developed and refined for usage by structural engineers to include analysis of structural elements as well as design of these members. Basics of Computer Structural Analysis: All computer based structural analysis programs work in a similar manner – the structure is broken into individual joints and members and Hooke’s law is used to determine forces, stresses, deflections and moments from large matrices of the load interactions between the joints and members. STAAD Computer Software: STAAD Pro is one of many commercially available general-purpose structural analysis/design software packages. STAAD is an acronym for ST ructural A nalysis and D esign, and was introduced in the early 1980s. It is capable of analyzing the largest 3- dimensional projects such as skyscrapers, stadiums, etc., or simple beams, trusses, or any other structural member or system. Joint Member
Transcript
Lecture 20 - Page 1 of 13
Lecture 20 – Computer Structural Analysis using “STAAD” BACKGROUND: Structural analysis by hand methods is feasible only for relatively simple structural members such as simply-supported beams and other 2-dimensional statically determinate frames. The real world, however, is much more complex and is composed of structures having multiple stories and supports, trusses, space frames, flat plates, arches, etc. Prior to the advent of digital computers in the 1960s, the analysis of these structures was most likely performed by “approximate” methods (such as moment distribution and portal analysis), or more rigorous exact methods involving applications of matrix and differential math. Originally, computer structural analysis was developed by mechanical and aerospace engineers for the airplane industry to calculate stresses on the wings and fuselage. Over the years, software was further developed and refined for usage by structural engineers to include analysis of structural elements as well as design of these members. Basics of Computer Structural Analysis: All computer based structural analysis programs work in a similar manner – the structure is broken into individual joints and members and Hooke’s law is used to determine forces, stresses, deflections and moments from large matrices of the load interactions between the joints and members. STAAD Computer Software: STAAD Pro is one of many commercially available general-purpose structural analysis/design software packages. STAAD is an acronym for STructural Analysis and Design, and was introduced in the early 1980s. It is capable of analyzing the largest 3-dimensional projects such as skyscrapers, stadiums, etc., or simple beams, trusses, or any other structural member or system.
Joint
Member
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STAAD Truss Analysis Example: The following simple truss will be analyzed using STAAD: By hand-calculations, it was determined that the forces in the members are as follows: Member: Force: Tension or Compression: Stress: AB and BC 7203 lbs. Compression 1372 PSI AD and DC 5625 lbs. Tension 1071 PSI BD 9000 lbs. Tension 1714 PSI To begin the analysis, a computer model of the truss must be determined, and joints must be defined (in X,Y coordinates) and members must be assigned as follows: Member No. Start Joint: End Joint: 1 1 2 2 2 3 3 1 4 4 3 4 5 2 4
R2 = 4500 Lbs. R1 = 4500 Lbs.
3 4
5
(10’,8’)
1
2
3 4
A
B
C
D
9000 lbs.
R1 R2
8’-0”
10’-0” 10’-0”
(0’,0’)
1 2
Member No.
Joint No. and coordinates
ALL members are nominal 2x4 wood (actual 1½” x 3½”)
(10’,0’)
Stress = AreaLoad
= )"5.3"5.1(.9000
xLbs
= 1714 PSI
(20’,0’)
Lecture 20 - Page 3 of 13
Follow the following steps to input the computer model, run the analysis and view & print the results: 1. Open the STAAD program by the following:
START → PROGRAMS → STAAD Pro Rel.3.1 → STAAD
This will open the program and will look like:
2. Pick the “New Structure” icon (or, go to File → New) and the following will appear:
Be sure to click “Truss” and put in a title as shown here. Then pick “Next”.
New Structure Icon
Lecture 20 - Page 4 of 13
3. The next screen will look like the following:
Another screen will appear, pick “Finish”. 4. You are now in the main graphic environment of the program, and the screen will
look like the following:
Be sure to click “Foot” and “Pound”, then pick “Next”.
STAAD Editor Icon
Lecture 20 - Page 5 of 13
5. Save your work by clicking on the Save icon. At this point, you are ready to begin
inputting your geometry. First, you must SAVE your work by clicking on the Save icon. The easiest way to do this is by picking the STAAD Editor icon (see above) and input information EXACTLY as shown below:
When finished inputting the information EXACTLY as shown above, click the “X” (close) button. The following screen will appear: (See next page)
YD = Depth in “Y” direction = 3.5” ZD = Width in “Z” direction = 1.5”
Member 1 is between Joints 1 & 2 Member 2 is between Joints 2 & 3 Member 3 …
Load of -9000 lb in the “Y” direction at Joint 4 (minus = downward force)
6. You are now ready to analyze the structure you just created. From the root menu,
select “Analyze” (see above) and pick “Run Analysis”. You will then see the following:
Analyze
STAAD Output
Be sure to pick “STAAD Analysis” and then hit the “Run Analysis” button
Lecture 20 - Page 7 of 13
The next screen should look like the following. IF you made any mistakes in your input, you will be informed! Hit the “Done” button.
7. If you get any error messages, you can edit your input by hitting the “STAAD Editor”
icon (see Step 4 above) to revise tour work, then follow Steps 5 and 6. DON’T GET s likely you will need to “tweak” your input to get the proper results of your analysis. BE PATIENT.
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8. You can view your results after you have run your analysis by picking the “STAAD Output” icon (see Step 5 above). Here you will be able to view your results and decide if you need to revise your input. The following is the STAAD output of your analysis:
9. IF YOUR RESULTS ARE CORRECT, you can print the output by hitting the “Print”
