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Scia Engineer 2013

Reporting Engineering Competence

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Nemetschek Scia is part of the Nemetschek Group

Seismic Design of Buildings

As a general 3D structural analysis software, Scia Engineer is able to provide a detailed analysis of civil engineering structures. However, the particular field of seismic design of buildings requires specific tools in order to improve the efficiency of that process.

The overall seismic behaviour of a building can very often be analyzed accurately by considering each floor as a mass linked to adjacent floors by walls and columns. Therefore the concept of storeys is widely used in this context. Several aspects of data input, as well as analytic model, result output and design functionality, will be directly linked to the storeys of a 3D building. Storey results give a summarised view of results in each storey. Displacements, accelerations, internal forces and resultant forces may be displayed per storey, either as bulk values for each storey, or as detailed results for each wall and column. That feature may also be used for fast determination of load paths.



Once an explicit, detailed 3D model of the structure has been defined and prepared for the purpose of static analysis, it is common for the same model to be used for dynamic analysis and for seismic design as well. A typical issue of using the full 3D model for obtaining the dynamic response is that seismic design focuses on the overall behaviour of the structure while analysing the full mesh of the model often results in ample information about local vibrations. More specifically in the case of modal analysis, the numerous local vibration modes are irrelevant for the overall seismic structural response. Hence, it seems practical to use a different, reduced mesh when performing dynamic analysis.

To enable this, an Improved Reduced System (IRS) method has been implemented, which takes into account not only the stiffness matrix of the system, but also the mass matrix, during the reduction process. This method has proven to give excellent results in dynamic analysis while calculation time is reduced tremendously.




Seismic Design of Buildings - Media

Seismic Design of Buildings - more information & links


StoreyResultsSummaryMasses.PNG Summary_Mass per storey.jpg

Most of the seismic codes require that structures be checked for torsion due to mass eccentricity by including an additional eccentricity in the model (the so-called accidental eccentricity). In Scia Engineer, using the IRS reduced model simplifies the introduction of accidental eccentricity, because reduced models use only one rotation-node (R-node) per storey. Accidental eccentricity may be taken into account either as real mass eccentricity or as additional torsional actions (simplified method according to design codes).

Scia Engineer makes it possible that masses which simulate the actual load effects on the structure are generated automatically based on static load cases. To ensure that no discrepancies occur in the introduced masses in the case of updated load values, the mass and load values are linked and continuously checked and updated.



Det_IntForces_Persp.jpg Downloads

Downloads

Storey Results


Improved Reduced System

Accidental Eccentricity

Seismic Design - Masses

Seismic Design - Internal Forces

Seismic Design of Buildings - Frequently Asked Questions (www.nemetschek-scia.com )


More Frequently Asked Questions on www.nemetschek-scia.com/support/faq

Det_ResultantsStorey_FL1+2_full building.jpg

Seismic Design - Resultant per Storey