Enter, modify or delete load cases and analysis conditions for pushover analysis.

Click the to create new load cases. Click the to confirm or modify and the to delete the data entry.

If Load Control is selected, pushover analysis is carried out to reach the estimated collapse load (Qud) through the load increments.

Enter the load case name pertaining to Pushover analysis.

Description

State a brief description related to the pushover load case.

General Control

Incremental Steps (nstep) : Number of steps to reach the estimated collapse load

Note

The incremental steps must be entered as a positive integer value (nstep≥1), and minimum 20 steps are recommended. (Default = 20)

Consider P-Delta Effect : Check on to consider P-Delta geometric nonlinear effects.

Note 1

P-Delta effect is very important in pushover analysis. Lateral displacement caused by the lateral load can be magnified by the gravitational load and this effect can reduce the lateral stiffness of the structure. Especially when plastic hinges occur at the lower part of the columns, which are under large axial forces, the reduced lateral stiffness can cause the collapse of the structure.

Note 2

The stiffness rapidly decreases after reaching peak strength in case of FEMA and Eurocode type hinge, while geometric stiffness is neglected after reaching ultimate strength, i.e. Collapse Prevention (CP) and Near Collapse (NC), respectively.

Use Initial Load : Accumulate the reaction/story shear/displacement due to the initial load to the pushover analysis result.

Reaction / Story Shear by Initial Load : Accumulate the reaction/story shear due to the initial load

Displacement by Initial Load : Accumulate the displacement due to the initial load

Note

When P-M interaction is considered, the user needs to apply the initial load.

Stepping Control Option

Specify the control data for the load increment.

Auto-Stepping Control : The applied load (Qud) is divided by the automatically calculated load parameters. The first step is loaded up to 90% of the elastic limit of the structure. Further steps are automatically divided by the ratio of

.

Note 1

Elastic limit means the estimated load under which the first yield occurs.

Note 2 Analysis method and example for the Auto-Stepping Control option

  Example

Equal Step (1/n step) : The applied load (Qud) is equally divided by the number of nstep.

Incremental Control Function : The applied load (Qud) is divided by the user-defined function. Refer to Design>Pushover Analysis>Pushover Increment Functions to see how to define user-defined function.

Analysis Stopping Condition

Specify the condition of termination of Pushover analysis.

Current Stiffness Ratio (Cs) : If the Current Stiffness Ratio (Cs) is entered and the ratio of the stiffness at the current an incremental step to the initial stiffness reaches the specified value, the analysis is terminated. For example, if the user specifies the Current Stiffness Ratio as 5%, analysis will be terminated when the ratio of the current stiffness to the initial stiffness becomes 0.05.

Note

In addition to the above conditions for termination of analysis, analysis is also terminated if the maximum number of increments is reached, or negative values are encountered in the stiffness matrix.

Limit Inter-Story Deformation Angle : If the Limit Inter-Story Deformation Angle is entered and the maximum Inter-Story Deformation Angle reaches the specified value, the analysis is terminated. (Default=1/10)

Define the type of load pattern (ratio of magnitude) to be applied to pushover analysis

Note

The combination of load cases multiplied by the corresponding scale factors is used as the load pattern.

Uniform Acceleration : he load is distributed relative to the inertia forces developed in the structure, which has been subject to a uniform acceleration. If the acceleration is uniform, the load pattern is determined proportionally to the mass at each story level.

Mode Shape : The pushover load pattern retains a mode shape and as such, eigenvalue analysis is a prerequisite. The user can select the orders of natural modes that are applied to determining the pushover load pattern.

Normalized Mode Shape* Mass: The Load pattern for the pushover analysis is obtained by the normalized mode shape x mass.

Example:

Note

For the Static Load Cases: All the static load cases are activated.

For the Uniform Acceleration: Load distribution directions (DX, DY, DZ) are activated.

For the Mode Shape: The User directly enters the mode. For this option, eigenvalue analysis must precede pushover analysis.

Note 2

If the following temperature loads are entered in the Load Pattern input box, pushover analysis cannot be performed.

1. Beam Section Temperature

3. System Temperature

4. Nodal Temperature

5. Element Temperature

If Displacement Control is selected

If Displacement Control is selected, pushover analysis is carried out to reach the target displacement through the incremental displacements.

Enter the load case name pertaining to Pushover analysis.

Description

State a brief description related to the pushover load case.

General Control

Specify the general control data for nonlinear analysis.

Incremental Steps (nstep) : Number of steps to reach the prescribed displacement

Note

The incremental steps must be entered as a positive integer value (nstep≥1), and minimum 20 steps are recommended. (Default = 20)

Consider P-Delta Effect : Check on to consider P-Delta geometric nonlinear effects.

Note 1

P-Delta effect is very important in pushover analysis. Lateral displacement caused by the lateral load can be magnified by the gravitational load and this effect can reduce the lateral stiffness of the structure. Especially when plastic hinges occur at the lower part of the columns, which are under large axial forces, the reduced lateral stiffness can cause the collapse of the structure.

Note 2

The stiffness rapidly decreases after reaching peak strength in case of FEMA type hinge, while geometric stiffness is neglected after reaching ultimate strength, i.e. Collapse Prevention (CP) and Near Collapse (NC), respectively.

Accumulate the reaction/story shear/displacement due to the initial load to the pushover analysis result.

Reaction / Story Shear by Initial Load : Accumulate the reaction/story shear due to the initial load

Displacement by Initial Load : Accumulate the displacement due to the initial load

Note

When P-M interaction is considered, the user needs to apply the initial load

Control Option

Specify the Target Displacement to be applied to pushover analysis

Global Control

Target displacement is specified with respect to the node where the maximum translational displacement occurs.

Maximum Translational Displacement: Specify the max. target translational displacement.

Note

For any structure with an irregular plan the node and direction of maximum displacement can be changed at each increment.

Master Node Control

Target displacement is specified relative to the master node.

Master Node: Master Node number

Master Direction: Select one of the three translational directions for the target displacement in the GCS.

Maximum Displacement: Max. target displacement

Analysis Stopping Condition

Specify the condition of termination of Pushover analysis.

Limit Inter-Story Deformation Angle : If the Limit Inter-Story Deformation Angle is entered and the maximum Inter-Story Deformation Angle reaches the specified value, the analysis is terminated. (Default=1/10)

Define the type of load pattern (ratio of magnitude) to be applied to pushover analysis

Load  : In a pushover analysis by displacement control, relative proportions are of importance for the distribution pattern rather than the magnitudes of the loads.

Note

The combination of load cases multiplied by the corresponding scale factors is used as the load pattern.

Uniform Acceleration : he load is distributed relative to the inertia forces developed in the structure, which has been subject to a uniform acceleration. If the acceleration is uniform, the load pattern is determined proportionally to the mass at each story level.

Mode Shape : The pushover load pattern retains a mode shape and as such, eigenvalue analysis is a prerequisite. The user can select the orders of natural modes that are applied to determining the pushover load pattern.

Note 1

For the Static Load Cases: All the static load cases are activated.

For the Uniform Acceleration: Load distribution directions (DX, DY, DZ) are activated.

For the Mode Shape: The user directly enters the mode. For this option, eigenvalue analysis must precede pushover analysis.

Note 2

If the following temperature loads are entered in the Load Pattern input box, pushover analysis cannot be performed.

1. Beam Section Temperature