SAP2000 tutorial course for beginners - 6: Solving trusses and arches


Introduction:

This is the last SAP2000 tutorial, at the end of this tutorial you'll be able to make a full structural analysis of any truss and areches and to display shear, moment and member forces diagrams as well.


Solving 2D Trusses using blank template (Continued)

Example 1: draw and analyze the truss shown in figure 1 using SAP2000. 

[Fig.1]

1- build the suitable grid system for the truss system (3 spacing in x- 1 spacing in z).
2- Draw the element of trusses using “moment releases” option as pinned instead of continuous. This will create moment releases at both ends (see figure 2). 

[Fig.2]

3- Assign supports and loads and set self-weight multiplier to be zero to neglect self-weight.
4- Run analysis.
5-Display deformed shape and non-deformed shape at the same time. To do this see figure 3. 

[Fig.3]

6- To display displacements at any point select it and then right click (see figure 4). 

[Fig.4]

7- Change units to mm to get better displacement (see figure 5). 

[Fig.5]

Solving 2D Trusses using 2D truss template: 

If user selects 2D truss template then awareness must be paid to end releases. Following steps are for choosing default vertical truss:

1- Choose 2D truss template as shown in figure 6. 

[Fig.6]

2- End releases can be checked in two ways: A) - click on “set display options” then check releases as shown in figure 7. 

[Fig.7]

Figure 8 indicates the members with moment releases. SAP suggestions can be modified manually by user. 

[Fig.8]

B) Select any member than right click on it so you can display moment releases in the member selected as shown in figure 9. 

[Fig.9]

Trusses problems: 

Problem #1:
Build this truss using SAP 2000 - see fig.10
Determine all the member forces
Identify the zero forces members

[Fig.10]

Problem #2:
Build this truss using SAP 2000 - see fig.11
Determine all the member forces
Identify the zero forces members

[Fig.11]
Problem #3:
Determine all the member forces
Identify the zero forces members
See fig.12

[Fig.12]

Problem #4:
Determine the force in members FG and DG of the truss shown in the figures below. State whether the members are in tension or compression.
Note: The reactions at the supports have been calculated. 

[Fig.13]

Creating arches using SAP2000: 

Arches can easily be created using SAP if user learn how to build cylindrical systems. So learning how to build cylindrical systems is the first thing to be done.
Building a cylindrical grid is an easy process in SAP. To Define a cylindrical system follow these steps:

1- Open a new file; Choose Blank.
2- Right click ➥ Edit grid data ➥ high light “GLOBAL” ➥ Modify/show system ➥ Quick start.
3- To draw cylindrical grid choose cylindrical tab. Cylindrical systems are defined by radius (R) and Theta (ϴ) (see figure 14)

Quick start window to define cylindrical system

[Fig.14]

Example 4:
Draw the grid line shown in figure 15.

[Fig.15]

1- As mentioned before user needs to define R & ϴ, R is 6 m as shown in figure 10. User can determine ϴ simply by dividing 180 on 6 (6 is number of angles):

2- Input at quick start must be as shown in Fig. 15. Number of grid lines along radius can easily be determined using this relation: Number of grid lines along radius = No. of radiuses+1

[Fig.16]

Exercise: Draw the cylindrical system shown in figure 17. Use R=6 m.

[Fig.17]

Example: Build arch shown in figure 18 using SAP.

[Fig.18]

1- SAP do not draw curves. Curves are represented as a small line segments connected to each others. This can be understood by looking at figure 19.

[Fig.19]

2- The much lines you have the more accurate you are in the simulation of the arch.

3- This arch will be divided into 8 parts. You must understand that this number is not the only correct way to simulate the arch. You may use less or more lines. Now look at figure 20.

[Fig.20]

4- Now user is going to create cylindrical system. Note that arch lies on xz plane while proposed grid will be drawn in xy plane.

5- Create a cylindrical system with the same input shown in figure 21.

[Fig.21]

User must now have a cylindrical system exactly as the one shown in figure 22.

[Fig.22]

6- Draw the arch in XY plane. User must have the same result as shown in figure 23.

[Fig.23]

7- This step is about transferring the drawn arch from xy to xz. To do that, first select arch elements ➥ Edit ➥ replicate ➥ radial (see figure 24).

[Fig.24]

After doing the previous step user will have same as shown in figure 25.

[Fig.25]

8- Now change view to RZ (actually xz) to view the arch in 2D (see figure 26).

[Fig.26]

9- Assign the supports to finish building the system (see figure 27).

[Fig.27]

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