STRUCTURAL ANALYSIS WITH SAP2000
By Mr. Linzhong Deng and Prof. Michel
Department of Civil Engineering
The City College of New York
SAP2000 is a general purpose finite element program which performs the static
or dynamic, linear or nonlinear analysis of structural systems. It is also a
powerful design tool to design structures following AASHTO specifications, ACI
and AISC building codes. These features, and many more make SAP2000 the
state-of-the-art in structural analysis program.
The SAP2000 graphic user interface (GUI) is used to model, analyze, design,
and display the structure geometry, properties and analysis results. The
analysis procedure can be divided into three parts:
Part I. Preprocessing.
In preprocessing, the following information is needed by SAP2000.
- Choosing the units for this project.
- Setting up geometry.
- Defining material and member section properties.
- Assigning member section properties and element releases.
- Defining load cases.
- Assigning load magnitudes.
- Assigning restraints.
From the combo (i.e. the drop down list) in the main window’s status bar,
choose the units for this project.
- Choosing units.
II. Setting up structure’s geometry.
There are two ways to set up the structure’s geometry: The first is from the
SAP2000’s templates. The other is by creating a completely new model.
When creating from a template, follow these steps:
- From File menu, choose New Model from Template… This will display the
Model Template dialog box.
- In this dialog box:
- Click on the template which most closely resembles the structure you
want to analyze. This will display the template dialog box.
- In this dialog box, choose the appropriate parameters.
- Click OK button.
The screen will refresh and display 3-D and 2-D views of the model in
vertically tiled adjoining windows. You can activate the one you plan to work in
by clicking the window’s title. You can any one of the two windows if you
When creating from a new model, follow these steps:
- From the File menu, choose the New Model… This will display the window
of coordinate system definition.
- In the window of coordinate system definition, enter the appropriate
grid information. The cross points of the grid will define the necessary
joints of your structure. This will display the 3-D and 2-D view window with
- 3-D and 2-D views of the model are displayed in vertically tiled
adjoining windows. You can close the 3-D windows if you wish. Active the 2-D
view by click the x-y button in toolbox or by clicking any point inside the
- From draw menu, choose "Draw From Element". This will change your mouse
point from " " to " " in the area of
- Draw your structure in the grid based on the grid spacings defined in
step 2. Click your left mouse button to define the joints. Every joint needs
one click. SAP2000 will connect the joints automatically. Double click the
left mouse button to stop the action of connection. When you draw something
wrong, click the " " inside the
floating toolbox situated in the lower part of your screen. Then click the
members which need to be deleted. Then from the edit menu, choose "delete".
To see the modified structure, from the display menu, choose the show
III. Define material and structural section properties.
In this step, we are going to define all the material types and all section
properties which are present in this structure. This requires the following
- From the define menu, choose material… This will display the window of
- If your material is standard steel or concrete, you can click
modify/show material button and use the library supplied properties. Click
button OK to accept appropriate properties. Otherwise click the
button add new material to define a new material’s properties, or the button
modify/show material to change the library’s data according to your
- From the define menu, choose Frame sections… This will display the Frame
sections dialog box.
- In this dialog box, you can define a new section type, import a
section’s geometry from the SAP2000’s library, or modify a section’s
geometry from the default values. Suppose you have two rectangular sections,
you need the following steps to define these sections.
- Highlight the FSEC1 in the box frame name.
- Click the modify/show section button. This will display the
window of rectangular section dialog box.
- In this box, choose the corresponding material from the material combo,
type in the number in the section’s width and height’s text box. Click ok to
terminate this dialog box and return to Frame sections dialog box.
- Choose Add rectangular in the second combo box. This will display
the rectangular section dialog box.
- repeat step c to define the properties of section section.
- If you want to delete a section type, you highlight the section’s name
which is to be deleted, then click the button delete sections.
- Click on the OK button to return the main window.
IV. Assigning member section properties.
There are three selection methods used by SAP2000 to assign member
properties, support restraints, loads... For clarity and convenience, these
three selection methods are summoned here. The first is to click the members one
by one after you click on the pointer tool button (" ") on the floating toolbox. The second way is
to drag a rectangular box after you click on the pointer tool button on the
floating toolbox. All of the objects inside this rectangular will be selected
simultaneously. The third way is to draw a straight line after you click the
"Sect intersecting line select mode" button on the floating toolbox. All the
objects intersecting the line you draw will be simultaneously selected.
You need the following steps to assign member section properties:
- Select a group of members which have the same sections by one of the 3
selection methods described above.
- From assign menu, choose frame, then sections… from
the submenu. This will display the define frame sections dialog box.
- In the name area of this dialog box, click the section corresponding to
this selected group (e.g. FSECT1 or FSECT2, etc).
- Repeat steps a, b and c until you have assigned a section for every
member of the structure.
- Select a group of members which will be assigned the same member
- From assign menu, choose frame, then release… from the
submenu. This will display the frame release dialog box.
- Choose the appropriate release parameters for the already selected
members. If these members are truss members, click the check-boxes of
torsion-start, moment22-start, moment22-end, moment33-start and
- Repeat steps e, f and g until you finish to assign release properties
for all the necessary members.
V. Defining load cases.
Now, it is time to give SAP2000 the applied load’s information. The steps
- From Define menu, choose Static load cases… This will
display the define load case dialog box.
- This dialog box will display the default load, LOAD1, with type set to
Dead, and self-weight multiplier set to unity. This will automatically
include the self-weight of structural members in the analysis based on
preset specific weights given in function of the material type. We don’t
have to change anything for this first load case. But if you wish to enter
the weight by your self and put it as joint load, or if you went to ignore
the offset of the dead weight, then you should change the self-weight
multiplier to 0 to avoid count the self weight twice.
- Define additional load cases, change the LOAD1 to LOAD2 (or the case you
defined), select load type from the Type drop-down list box, change the
self-weight multiplier to appropriate number. In most times, you change the
self-weight multiplier to 0 because dead load already count dead load in
LOAD1). Then click on the Add new Load button to notify SAP2000.
Repeat this step until you define all the load cases.
- Finally, click OK to back to main window.
In the following section of assigning joint load cases, you must assign a
numerical volume and the location of each joint loads for every load cases.
VI. Assigning loads.
For simplicity, we just talk about assigning joint loads. If you wish to
apply a distributed load on a member, you can refer to SAP2000 manual for
detail. To assign joint loads execute the following steps:
- Select the joints which have the same joint loads. You can use one of
the three selection methods used previously to select members.
- From the Assign menu, choose Joint Static Loads, then
Forces… from the submenu. This will display the Joint forces dialog
- In this dialog box, accept the default load case name as LOAD1, enter
the corresponding joint force components in the Load area. Click OK
to accept the above joint loads.
- Repeat steps a, b and c until you assign all the joint loads of this
load case defined to this structure.
- Repeat steps a, b, c and d until you finish every load case’s load
VII. Assigning restraints.
It is very important to assign restraints to your structure. Otherwise your
structure will become unstable or it becomes a free body and it cannot be solved
by SAP2000. Applying joint restraints requires the following steps:
- Click the Pointer Tool button ( i.e. ) in the Floating Toolbar.
- Click the joints which have the same restraints.
- From the Assign menu, choose the Jointà Restraints… from the submenu. This
will display the joint restraint dialog box.
- In this dialog box, choose appropriate restraint parameter. Then click
OK to accept this assignment.
- Repeat steps a, b, c and d until you finish the restraint assignment.
PART II. SolvingIn this part SAP2000 will assemble and solve the
global matrix. The following steps are needed:
- From the Analysis menu, select Set Option… This will display
the Analysis Option dialog box.
- In this dialog box, check the available DOF. If you are analyzing a plane
truss, check UX and UY, leave the UZ, RX, RY and RZ blank.
- Click OK to accept what you choose.
- From the analysis menu, select Run. This will display the
Save Model File As dialog box.
- In this dialog box, save the model under a filename. No extension is
- Click the OK button, the analysis will begin. A top window is
opened in which the various phases of analysis process are progressively
reported. When the analysis is complete, the screen will display the message
- Click OK button in the top window to close it.
PART III. Postprocessing.
The main options in postprocessing are:
- Displaying the deformed shape.
- Displaying the member forces.
- Printing the results.
- Designing the structural members and checking the safety of a design.
- Modifying the structure.
For simplicity, we just discuss the three fundamental options: displaying the
deformed shape, displaying the member forces and printing results here.
- Displaying the deformed shape.
After the analysis is complete, SAP2000 automatically displays the deformed
shape of the model for the default load case, LOAD1, in the active display
window. We can now display the deformed shape for another load case in one of
the two view windows.
- Activate one of the two view windows by clicking anywhere inside that
- Click the display deformed shape button on the floating toolbar. This will
display the deformed shape dialog box.
- In the drop down list in the load area of this dialog box, select the load
case to be displayed, then click OK button. The deformed shape will
- Displaying the member forces.
- From the Display menu, click the Show element
forces/stressesà frames, this
will display the member force diagram dialog box.
- In this dialog box, select the component which need to display (for truss,
choose Axial force) in the Component area, and click OK button.
The axial force diagram for the entire truss is displayed. By moving cursor to
a specific location, we can read the values of the force at that point.
- Printing the results.
- From File menu, select Print Output Table… In the display
dialog box, click OK to accept the default setting. The detailed output
results will be printed.
- From File menu, select Print Input Table… In the display
dialog box, click OK to accept the default setting. The detailed input
information will be printed.
You can also get the detailed results in another way. When we analyze a
structure, by default, SAP2000 will create three output files: filename.out,
filename.log and filename.EKO. The output file filename.out stores the output of
your analysis. The output file filename.EKO stores the input information for
this structure. The output file filename.log take all of the running
information. These files are text files. You can print these files using
computer operating system. For example, we can print these files from Notepad.
The steps are:
- Open Notepad by double click the Notepad icon on the main window.
- From File menu, choose Open. This will display a standard
Microsoft file selection dialog box.
- In this dialog box, choose the drive and subdirectory where your file is
- Click on the file name you want to display and print. (i. e. any one of
filename.out, filename.EKO, or filename.log.)
- Click OK to terminate this dialog box. Your file will display by
- Review the file to make sure your results are correct.
- From File menu, choose print… This will display the print
- Click OK to accept the default print setting. Your file will print on
- Repeat steps b, c, d, e, f, g and h to print another file.
- Close Notepad by choosing Exit from the File menu.