Introduction
CYPECAD carries out the design, analysis, and sizing of structures for building and civil works which are subject to vertical and horizontal forces as well as fire exposure.
More information about seismic analyses carried out by CYPECAD can be found on this webpage.
More general information about this program can be found on the CYPECAD website.
Design load analysis
Before specifying the features of the seismic analysis that CYPECAD can carry out, it is worth noting the analysis of vertical and horizontal design loads that the program performs.
A summary of this information can be found in the “Design load analysis” section of CYPECAD’s main information page.
Detailed information on this topic can be found in the “CYPECAD - Calculations manual”. This manual can be accessed from the main menu of CYPE programs or from the “Help” drop-down menu in CYPECAD.
Seismic analysis
The seismic analysis is carried out by means of a modal spectral analysis that solves each modal as a loadcase and performs modal expansion and modal combination in order to obtain forces.
The “CYPECAD - Calculations manual” can be accessed from the main menu from any CYPE program or from the “Help” drop-down menu in CYPECAD, where extensive information about seismic analysis carried out by CYPECAD can be found.
The selection of the code for carrying out seismic analysis in CYPECAD appears in the “General data” window, more precisely, in the “Load selection” section. On the “CYPECAD. General data, and analysis and general options” page there is information on how to access this window.
The codes that can be used can be consulted on the “Codes included in the user license” web page.
Some important aspects of the seismic analysis carried out by CYPECAD are explained in the following sections.
Effect of non-structural construction elements on buildings’ seismic behaviour
Considering the effect of the non-structural construction elements (external walls and partitions) on a building’s behaviour when facing seismic actions is of vital importance, especially when there are open floors or floors with partitions and external walls that are less rigid than the rest of the floors.
CYPECAD allows the effect of non-structural elements during an earthquake to be considered in two ways:
- By means of amplifying forces in open floors or those with less rigid partitions compared to the rest of the floors
Approximate method. - By means of a dynamic analysis of buildings subjected to seismic actions that include the effect of non-structural construction elements
Accurate analysis developed by CYPE with the collaboration of the “International Centre for Numerical Methods in Engineering (CIMNE)” from the “Polytechnic University of Catalonia (UPC),” and included in the “Interaction of the structure with the construction elements” module (in order to be used, the module must be included in the user license).
Seismic analysis with force amplification in open floors or those with less rigid partitions compared to the rest of the floors
Some codes require the absence or reduction of stiffness of the partitions and external walls on certain floors, by applying moment and shear amplification factors for columns, beams, walls and shear walls, on the floors with less stiffness than others when faced with horizontal displacements caused by seismic action. For example, code IS 13920 (India) -Soft Storey- or the code CIRSOC 103-2008 (Argentina) -Piso débil. Naturally, the tendency of the codes that do not consider these effects should focus on addressing them.
CYPECAD allows users to introduce the moment and shear amplification factors for columns, beams, walls and shear walls, on the desired floors, regardless of the selected code. For this purpose, the Amplification forces by floor option has been added to the General data window (Project menu > General data). By activating this option, a window with the same name will open. If the selected code considers the effect of the reduced stiffness of floors with weaker partitions, the program will display the corresponding moment and shear amplification factors onscreen so that users can select the floors where they wish to apply them. Users also can indicate the factors they desire. If the selected code does not consider these effects, the program will allow users to introduce the desired amplification factors to the floors they select.
This method for considering the effect that the absence of partitions and external walls has on certain floors when faced with seismic action is an approximation to the reality of the behaviour of the building.
CYPECAD has a software tool that takes a more accurate look at the influence that the distribution of partitions and external walls has on the building: the “Interaction of the structure with the construction elements” module which is summarised in the following section.
Interaction of the structure with the construction elements
CYPECAD has a software tool that allows dynamic analysis of buildings under seismic actions including the effect of the nonstructural construction elements used in the external walls and partitions of a building and considers various models of building behaviour corresponding to different situations or states of these elements.
The external walls and partitions of the buildings are considered as ‘nonstructural’ elements, however, during an earthquake, they provide the structure with stiffness, modifying the distribution and magnitude of the forces caused by the seismic action. For example, when there is an uneven distribution between the floors of the stiffnesses associated with the external walls, the horizontal forces have a greater impact on the columns of the floors with less stiffness, causing a high magnitude of shear forces in the columns. If the columns are not properly designed, the forces could cause their brittle failure, which would endanger the stability of the building and even lead to its collapse.
This module has been developed by CYPE, with the collaboration of the International Centre for Numerical Methods in Engineering (CIMNE) from the Polytechnic University of Catalonia (UPC), financed by the Centre for the Development of Industrial Technology (CDTI) and co-financed by the European Regional Development Fund (ERDF).
There are currently no software tools on the market for the structural analysis of buildings that include the possibility of considering external walls and partitions in a simple way, despite the fact it has been proved that they have direct consequences on stability, stiffness and building safety in the event of an earthquake. Since this CYPECAD module does include them, keeping computation times at an admissible value, their incorporation in building projects will increase their quality and the safety of occupants, thus avoiding major losses, both material and human, following an earthquake.
More information can be found on the “Interaction of the structure with the construction elements” webpage.
