Pushover Analysis Using STAAD.Pro

Using Pushover Analysis

This section details using a pushover analysis in the STAAD.Pro graphical environment.
An advanced analysis module license is required to access this feature.

1.1 To define general pushover data

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1. Select Commands > Loading > Definitions > Pushover.

The Create New Definitions / Load Cases / Load Items dialogue opens with only the Pushover tab displayed.

1. On the Define Input tab, select the General Input Parameters option.
2. (Optional) Select the Type of Frame as either Moment or Braced (Moment is used by default).
3. (Optional) Select Include Effect for the Geometric Non-Linearity Effect if this is to be considered.

Pushover Analysis Using STAAD.Pro

1.2 To define member-specific pushover data

Use the following optional procedure to specify parameters for individual members.

1. Select Commands > Loading > Definitions > Pushover.

The Create New Definitions / Load Cases / Load Items dialogue opens with only the Pushover tab displayed.

1. On the Define Input tab, select the Member Specific Parameters option.
2. (Optional) Set the Expected Yield Stress option and specify a value for the yield stress in current units.
3. (Optional) Set the Effective Length Factor for Member (Y/Z) option (separate options for each local direction) and specify values for the effective length factor for members.
4. Click Add.
5. Once any other parameters have been added, click Close.

Entries for the member parameters are added in the Loads & Definitions dialogue in the Definitions > Pushover Definitions section.

1. Select one of the member parameters and click Assign.

Refer to Graphical Environment help for using the various assignment methods in the Loads & Definitions dialogue.

1.3 To manually define and assign hinges

Use the following optional procedure to define parameters and assign hinges manually.

If the pushover analysis will make use of the built-in FEMA hinge properties for all members,

1. Select Commands > Loading > Definitions > Pushover.

The Create New Definitions / Load Cases / Load Items dialogue opens with only the Pushover tab displayed.

1. Select the Define Hinge Property tab.
2. Select the Hinge Type.

Types FEMA or Ignore do not require any additional parameters.

1. (User Defined hinge type only) Select an existing Type ID or select New Type to define a new hinge type.
2. (User Defined hinge type only) Specify a unique integer for the Type Identifier.
3. (User Defined hinge type only) Specify coordinate values for points C, D, and E in the Load Deformation Curve Points and IO, LS, and CP values in the Acceptance Criteria.

These values are can be determined using Tables 5-6 and 5-7 in FEMA 356.

1. (User Defined hinge type only) Specify values for Yield Moment (YR) and Yield Rotation (YR).

These values are calculated per Section 5.5.2.2.2 of FEMA 365 (See “Frame element hinge properties”).

1. Click Add.
2. Once any other parameters have been added, click Close.

Entries for the hinge types are added in the Loads & Definitions dialog in the Definitions > Pushover Definitions section.

1. Select one of the hinge types and click Assign.

Refer to Graphical Environment for help for using the various assignment methods in the Loads & Definitions dialogue.

1.4 To define pushover spectral data

Use the following procedure to define the seismic hazard per FEMA 356.

1. Select Commands > Loading > Definitions > Pushover.

The Create New Definitions / Load Cases / Load Items dialogue opens with only the Pushover tab displayed.

1. Select the Define Spectral Details tab.
2. Specify up to four Critical Damping values for the 1st through 4th spectrums.

At least one is required, which has a default value of 5.0%.

1. (Optional) Select the Site Category which describes the soil per Section 1.6.1.4.1 of FEMA 356 (Site Class D is used by default).
2. Specify the Mapped Spectral Acceleration At Short Period, S_s, to be used per Table 1-4 of FEMA 356.
3. Specify the Mapped Spectral Acceleration At One-Second Period, S₁, to be used per Table 1-5 of FEMA 356.
4. Click Add.

1.5 To add a pushover loading

Use the following procedure to define the pushover loading to be used in the pushover analysis.

1. Select Commands > Loading > Definitions > Pushover.

The Create New Definitions / Load Cases / Load Items dialogue opens with only the Pushover tab displayed.

1. Select the Define Loading Pattern tab.
2. (Optional) Select User Defined as the Loading Pattern type if you want to manually specify the gravity loading to be used for the pushover analysis.

If the default Autoload pattern is used, the program will internally compute the gravity loads.

1. (Optional) Set the Method for Lateral Load Calculation option and select the method to be used.

See “Define Loading Pattern “ for additional information on each method.

1. (Optional) Set the Total Base Shear to be Distributed option then select the Direction and specify the Total Base Shear value.
2. (Optional) Specify a Number of Push Load Steps to be used in the analysis.
3. Click Add.

Only one pushover loading definition may be used for a model. If a different pushover loading definition is required, either change the individual parameters or delete them and create a new definition.

1.6 To define solution control

Use the following procedure to define at least one solution control method for the pushover analysis.

1. Select Commands > Loading > Definitions > Pushover.

The Create New Definitions / Load Cases / Load Items dialog opens with only the Pushover tab displayed.

1. Select the Define Solution Control tab.
2. (Optional) Set the Push Up to Defined Base Shear option and specify both a Direction and Defined Base Shear value.
3. (Optional) Set the Push Up to Defined Displacement at Control Joint, specify the Direction and Joint Displacement Value, and select the Joint Number to be used.
4. Click Add.

1.7 To specify a pushover analysis

Use the following procedure to direct the program to perform a pushover analysis.

You must first define pushover data and the pushover loading.

1. Select either

Commands > Analysis > Perform Pushover Analysis

or

the Analysis/Print | Analysis page and then click Add on the Perform Pushover Analysis tab in the Analysis/Print Commands dialogue.

A message dialogue opens to confirm you want to add this command.

1.8 To review pushover analysis results

Once a successful pushover analysis is performed, pushover results are available in the Post Processing mode.

1. Select either

Mode > Post Processing

or

the Post Processing tab in the mode control bar

The Post Processing mode opens.

1. Select the Pushover page in the page control.
2. Select the Pushover | Loads page and use the Select Load Step control in the Load Values table to review the pushover load applied at each load step.
3. Select the Pushover | Capacity Curve page to review the plot of the Base Shear versus the Displacement at Control Joint in the Capacity Curve graph.
4. Select the Pushover | Node Results page and use the Select Load Step control in either the Node Displacements table or the Support Reactions table to review the nodal displacements and support reactions at each load step.
5. Select the Pushover | Beam Results page and use the Select Load Step control in either the Beam Hinge Results table or the Beam Force Detail table to review the nodal displacements and support reactions at each load step.

The hinges are graphically displayed on the structure for each load step using the colour coding for acceptance criteria:

• (Green) The initial Hinge format at the top of the elastic range represents Immediate Occupancy.
• (Blue) Hinge in the Life Safety range
• (Purple) Hinge in the Collapse Prevention range.
• (Red) Hinge greater than Collapse Prevention range.

What is the performance point in pushover analysis?

The Performance Point, which represents the state of the maximum inelastic capacity of the structure, is found through the cross point of the Capacity Spectrum and Demand Spectrum for a given damping ratio.

What is a pushover curve?

A pushover curve is a plot drawn between base shear along the vertical axis and roof displacement along the horizontal axis. The performance point of the structure in various stages can be obtained from the pushover curve.

What is target displacement in pushover analysis?

The target displacement is an estimation of the top displacement of the building when exposed to the design earthquake excitation. Then a pushover analysis is carried out on the building until the top displacement of the building equals the target displacement.

How do you do a pushover analysis in Etabs?

Click here to watch

Why do we use pushover analysis?

In existing structures where the owner does not care of it being partly damaged, as long as total collapse is avoided, you take samples in order to understand the remaining stress. You create a structural analysis model based on that remaining stress. After that, you use pushover analysis in order to rehabilitate the structure. It is also at times more cost-effective to just design the structure to just avoid collapse than totally rehabilitate it according to more current design codes.

How do you do a pushover analysis in sap2000?

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To watch click here

Why Pushover Analysis?

Pushover analysis is commonly used to evaluate the seismic capacity of existing structures and appears in several recent guidelines for retrofit seismic design. It can also be useful for the performance-based design of new buildings that rely on ductility or redundancies to resist earthquake forces.

Pushover Analysis in STAAD Pro

Pushover analysis is a nonlinear static analysis procedure used to assess the seismic performance of structures. It is a common tool used in performance-based seismic design (PBSD), which aims to design structures to achieve specified performance levels under earthquake loading.

Steps involved in pushover analysis in STAAD.Pro:

1. Define the pushover load pattern: The pushover load pattern defines how the lateral load is applied to the structure. The load pattern can be triangular, uniform, or any other user-defined pattern.
2. Define the pushover control point: The pushover control point is the point at which the displacement is monitored during the analysis. The control point is typically located at the roof or another representative point of the structure.
3. Define the pushover criteria: The pushover criteria define the conditions under which the analysis will terminate. The criteria can be based on displacement, force, or any other user-defined parameter.
4. Run the analysis: STAAD.Pro will incrementally apply the pushover load pattern to the structure and monitor the displacement at the control point. The analysis will terminate when one of the pushover criteria is met.
5. Review the results: The results of the pushover analysis include the pushover curve, which is a plot of the base shear versus the roof displacement. The pushover curve can be used to assess the overall strength and ductility of the structure.

Pushover analysis in STAAD.Pro can be used to:

• Evaluate the seismic performance of a structure
• Identify potential weak points in a structure
• Develop performance-based design criteria
• Compare the performance of different design alternatives

Limitations of pushover analysis in STAAD.Pro:

• Pushover analysis is a static analysis, and it does not account for the dynamic effects of earthquakes.
• Pushover analysis is only as accurate as the material properties and modeling assumptions used in the analysis.
• Pushover analysis cannot be used to predict the actual response of a structure in an earthquake.

Here are some additional things to keep in mind when performing pushover analysis in STAAD.Pro:

• The pushover load pattern should be representative of the expected earthquake loading.
• The pushover control point should be located at a point where the displacement is representative of the overall response of the structure.
• The pushover criteria should be based on the performance objectives for the structure.
• The results of the pushover analysis should be interpreted with caution, as they are only an approximation of the actual response of the structure in an earthquake.