Versions Compared

Old Version 16

changes.mady.by.user Mike Abell

Saved on

compared with

New Version Current

changes.mady.by.user Ondrej

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.


{info} This page is devoted to *frequently asked questions* (FAQ) specific to [acceleration|Acceleration]. {info} {on-this-page} h1. General FAQ h2. How does SAP2000 calculate and apply acceleration loads? _[See acceleration load page.|Acceleration load]_ h2. What is the procedure used for calculating rotational acceleration loads? *Question:* What is the exact procedure the program uses to calculate the rotational acceleration loads? For translational acceleration loads, the loads are calculated as negative translational mass times the acceleration. For rotational acceleration loads how exactly is the translational mass, rotational mass, or both masses used to calculate the acceleration loads? *Answer:* _[See acceleration load page.|Acceleration load]_ h2. Under "Display > Show Plot Functions" menu command, absolute or relative acceleration (velocity or displacement) can be chosen. What is the difference between relative and absolute responses? Relative acceleration is acceleration relative to the ground. Absolute acceleration is the sum of relative acceleration and the input ground acceleration. h2. Can I apply acceleration loads only to selected members in the model? If you need to apply acceleration loads only to some elements in your model, you would need to apply these loads manually
Wiki Markup
Info

This page is devoted to frequently asked questions (FAQ) related to acceleration.

On this page:

Table of Contents

General

What is the difference between relative and absolute acceleration?

ANSWER: Relative acceleration is within the reference frame local to the structure. Absolute acceleration is within a universal reference frame, and is given as the sum of relative acceleration and ground acceleration. The same relative and absolute designations also apply to velocity and displacement.

The Display > Show Plot Functions menu presents options for either relative or absolute acceleration.

Show if
groupeditors

Related Incidents:

  • Incident 77662: Relative vs absolute joint displacements

Alternate explanation:

Relative displacement is within the reference system local to the structure. Absolute displacement is within a universal reference system and is given as the sum of relative displacement and ground displacement.

In other words, the relative displacement is displacement of joints on the structure relative to the displacement of the foundation joints. Absolute displacements are measured from a fixed point located far away on the ground that is not affected by the earthquake.

Is acceleration load only applied to selected members?

ANSWER: No. CSI software automatically generates and envelopes a set of acceleration loads for translation along, and rotation about, each global axis. These acceleration loads are applied at each node and object to simulate ground motion during time-history and translation-only response-spectrum analyses. 

Acceleration loads may be manually assigned to specific nodes and objects, then applied through a load case. Acceleration loads in the program are included as a percentage of gravity, g. Therefore, to manually assign acceleration loads to selected members, first divide the acceleration by g. Then enter the percentage in the Scale Factor box in the Loads Applied area of the Load Case Data form.  

Formulation

How is acceleration load calculated and applied?

ANSWER: Please see the Acceleration loads article for response.

How is rotational-acceleration load calculated and applied?

ANSWER: Please see the Acceleration loads article for response.