Table of Contents Click on a topic below to go directly to the page.

Transcription

1 CE 331, Spring 2004 RISA Frame Design Procedures 1 /9 Table of Contents Click on a topic below to go directly to the page. 1) Setup your Structural Model ) Draw the Members ) Set the Boundary Conditions ) Input the Loads ) Analyze the frame for DL+LL to compare with hand-calculations ) Analyze the frame for WL-only to compare with Sidesway hand calculations ) Design your structure ) Record the design results ) Verify RISA s Unity Checks ) Setup your Structural Model a) Set the correct yeild stress in General Materials b) Setup your sections in Sections Specify W sections and use the largest listed (default). c) Tell RISA to redesign your sections in Section Redesign

2 CE 331, Spring 2004 RISA Frame Design Procedures 2 /9 2) Draw the Members a) Setup your grid for drawing members. b) Draw your members, being careful to specify the correct section ( columns vs. girder ). c) You can check that your sections are correctly assigned to your members by clicking Plot Options, then Members, then Section Set under Labeling. 3) Set the Boundary Conditions a) All nodes in your 2D model should be restricted from moving out of plane

3 CE 331, Spring 2004 RISA Frame Design Procedures 3 /9 b) Specify reactions for nodes having X, Y or Z-rotation reactions. The boundary conditions for the column bases in our moment frame are shown below c) The correct boundary conditions for our moment frame are shown at rightw 4) Input the Loads a) Set up the Basic Load Cases and the Load Combinations Be sure to enter the correct factors for each combination.

4 CE 331, Spring 2004 RISA Frame Design Procedures 4 /9 b) Input the loads for each load case graphically. Input loads at the joints using Joint Loads and loads between joints using Point Loads. Be careful to specify the correct Basic Load Case before drawing the loads. 5) Analyze the frame for DL+LL to compare with hand-calculations. a) Turn off shear deformations when running RISA to compare against your hand calculations. Click on Global then Switch to ADVANCED Options

5 CE 331, Spring 2004 RISA Frame Design Procedures 5 /9 Then Shear Deformation? b) Analyze the DL + LL load combination c) If this is the first time you ve analyzed the model, it s a good idea to check the deflected shape of the structure. This can catch a multitude of different errors. Click on Plot Options Then Deflection Diagrams The Load Combination You may need to increase the Magnification Factor

6 CE 331, Spring 2004 RISA Frame Design Procedures 6 /9 d) Display the axial forces, shear forces and bending moment diagram to compare with hand-calcs. Click on Plot Options Members Axial under Member Results Outline Magnitudes Repeat for: y Shear and z-z Moment 6) Analyze the frame for WL-only to compare with Sidesway hand calculations.. 7) Design your structure. a) Turn Shear Deformations back on b) Specify self wt. by typing -1 under Y-Gravity for the DL Basic Load Case. c) Checking the Solve boxes for each appropriate load combination d) Click on Solve Envelope

7 CE 331, Spring 2004 RISA Frame Design Procedures 7 /9 e) Display Alternate Shapes and ask RISA to Replace (members) and Re-solve by rightclicking anywhere in the Alternate Shapes dialog box.. f) Since RISA frequently converges to slightly different shapes, we will type the final member sizes into RISA in the Sections diaglog box. 8) Record the design results a) select Steel Code Checks. Translate the information in the first four columns of the table above to provide the max unity check, member and location of max unity check, and the critical load combination.

8 CE 331, Spring 2004 RISA Frame Design Procedures 8 /9 9) Verify RISA s Unity Checks. a) Analyze the appropriate Load Combination for each member (e.g. for the columns, analyze LC 3: DL +.7LL +.7WL b) Use the Detailed Results button and click on the desired member (e.g. M2 for the columns). c) Write down the numbers needed to calculate the Unity Check for the member, including the equation A, fa, Fa Mz, fc, Fbz

9 CE 331, Spring 2004 RISA Frame Design Procedures 9 /9 d) To get section properties for calculating stresses, Select Sections Record A and Izz You will need to select the shape and select Edit from the Shape Selection dialog box to get the depth of section for calculating the section modulus: S = I/depth