Seismisk analyse av konstruksjoner ved Robot Structural ... · Robot Structural Analysis (RSA) Marius Jablonskis NTI CADcenter AS. NTI CADcenter AS · Telefon: 482 03 300 · · Sandvika

NTI CADcenter AS · Telefon: 482 03 300 · www.nticad.no · Sandvika · Ålesund · Bergen

Seismisk analyse av konstruksjoner ved

Robot Structural Analysis (RSA)

Marius Jablonskis

NTI CADcenter AS


• Defining modal analysis load case

• Defining added masses using or conversion of loads to masses

• Defining appropriate number of modes

• Defining seismic analysis:

• Specifying code parameters and selecting direction definition

• Determining the number of modes to be taken into account

• Defining combination sign

• Defining design combinations

• Running analysis

Basic workflow of seismic analysis using RSA



Defining modal analysis load case

using Analysis Type / New:



Defining added masses using Loads

/ Load definition or conversion of

loads to masses using appropriate

dialogue:



Defining appropriate number of modes:



Defining seismic analysis EC8 using

Analysis Type / New:



Specifying code parameters and

selecting Direction definition:



Selecting the method of creating

combinations between directions –

on European market usually

Newmark combinations are used.

Specifying the type of

combinations between modes

(usually CQC) used for each

direction in combinations between

directions:



Filters / Determining the number

of modes to be taken into account:



In case of using signed quadratic

combinations it will be necessary to

set main modes for each of

directions. Usually the main

criterion to select such modes is

their contribution to participation

mass for given direction - this

contribution can be checked in

Dynamic Analysis Results with

appropriate columns added:



Defining design combinations

(manual or automatic ones)

considering static load cases and

dynamic combinations:



Running analysis:


Special issues in seismic analysis using RSA

• Mass matrix type

• Active mass directions

• Mass eccentricities

• Torsion

• Fixed supports vs spring supports

• Defining stories

• Defining core walls

• Reduced results

• Q&A



Mass matrix types:

• Consistent (consistent matrix always with

regard to the rotational degrees of freedom)

• Lumped with rotations (diagonal matrix with

regard to rotational degrees of freedom)

• Lumped without rotations (diagonal matrix

without rotational degrees of freedom).



Mass matrix types:

If you use lumped masses then mass is

'assigned' to nodes existing in the structure.

The larger number of the intermediate nodes

along a beam you create the closer to the

reality you are and it increases the precision of

the solution. If you use the consistent mass

matrix the mass is distributed along a bar

element rather than assigned to the nodes.



Active mass direction:

You may need to deselect a direction when

performing the seismic analysis. If you deselect

the mass in the Z direction, for the modal

analysis that precedes the seismic case, it

eliminates local vertical vibration modes for

floor slabs. In the seismic analysis for such

model you will consider only transversal

vibrations.



Mass eccentricities:

The tensional effect is taken into account by

adding mass eccentricity. You can do this as

either modal analysis parameters (exact

method) or seismic analysis parameters

(simplified approach).



Torsion:



Reduced results:



Q&A

Documents

Seismisk analyse av konstruksjoner ved Robot Structural ... · Robot Structural Analysis (RSA) Marius Jablonskis NTI CADcenter AS. NTI CADcenter AS · Telefon: 482 03 300 · · Sandvika