Nonlinear Analysis In Etabs

[Cripin Plascencia]

FastNonlinear Analysis (FNA) is a modal analysis method useful for the static or dynamic evaluation of linear or nonlinear structural systems. Because of its computationally efficient formulation, FNA is well-suited for time-history analysis, and often recommended over direct-integration applications. During dynamic-nonlinear FNA application, analytical models should:

In addition to nonlinear material force-deformation relationships, these link objects may simulate concentrated damping devices, isolators, and other energy-dissipating technologies. If fuse mechanisms are not integral to the design intention, an initial elastic analysis may reveal locations where inelasticity is likely to occur. However, it is always best to predefine inelastic mechanisms such that their design may provide for sufficient ductility, while elastic systems are ensured sufficient strength. Capacity Design provides for a more reliable model and a better-performing structure.

The efficiency of FNA formulation is largely due to the separation of the nonlinear-object force vector RNL(t) from the elastic stiffness matrix and the damped equations of motion, as seen in the fundamental equilibrium equation of FNA, expressed as:

Stiffness- and mass-orthogonal Load-Dependent Ritz Vectors represent the equilibrium relationships within the elastic structural system. At each time increment, the uncoupled modal equations are solved exactly, while forces within the predefined nonlinear DOF, indexed within RNL(t), are resolved through an iterative process which converges to satisfy equilibrium. Following this procedure, FNA is an efficient and accurate dynamic-nonlinear application which satisfies equilibrium, force-deformation, and compatibility relationships.

Nonlinear analysis methods are best applied when either geometric or material nonlinearity is considered during structural modeling and analysis. If only elastic material behavior is considered, linear analysis methods should suffice, though P-Delta formulation may still be applied. Linear and nonlinear methods may be static or dynamic. A few of the traditional analysis methods, and the relations between their attributes, are presented in Figure 1:

Founded in 1975, Computers and Structures, Inc. (CSI) is recognized globally as the pioneering leader in software tools for structural and earthquake engineering. Software from CSI is used by thousands of engineering firms in over 160 countries for the design of major projects, including the Taipei 101 Tower in Taiwan, One World Trade Center in New York, the 2008 Olympics Birds Nest Stadium in Beijing and the cable-stayed Centenario Bridge over the Panama Canal. CSI's software is backed by more than four decades of research and development, making it the trusted choice of sophisticated design professionals everywhere.

Each of these programs offers unique capabilities and tools that are tailored to different types of structures and problems, allowing users to find just the right solution for their work. SAP2000 is intended for use on civil structures such as dams, communication towers, stadiums, industrial plants and buildings. CSiBridge offers powerful parametric design of concrete and steel bridges. ETABS has been developed specifically for multi-story commercial and residential building structures, such as office towers, apartments and hospitals. The SAFE System provides an efficient and powerful program for the analysis and design of concrete slabs and foundations, with or without post-tensioning. PERFORM-3D is a highly focused nonlinear tool offering powerful performance based design capabilities.

With its uniquely qualified staff of professional structural engineers, researchers, academicians, and its worldwide involvement in the structural engineering community, CSI has been at the forefront of structural software development for nearly four decades. With CSI products you can be confident that you have the finest structural engineering software available, backed by a company with an unmatched record of innovation, and an unrivaled commitment to meet the ever-evolving needs of the profession.\r\n\t\t\t

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Computers and Structures, Inc. (CSI) has implemented a comprehensive quality management system to ensure that customer expectations and industry requirements are not only met but exceeded. Since 2008, CSI has been certified ISO 9001-compliant by Det Norske Veritas, an independent certification agency accredited by the International Organization for Standardization.

Our quality management system covers processes and procedures for activities specific to the design and development of all of our software products. Sales, licensing, customer support, and purchasing- and distribution-related processes are also controlled under the quality management system.

\r\n\t\t\tCSI offers an enhanced error notification service for customers wishing to comply with reporting regulations set forth by the nuclear industry. With this service, customers receive a customized notification whenever a qualifying error is found in CSI software, including the nature, scope and impact of the error and a workaround whenever possible. Customers may make their own determination as to whether the error is safety-related. Contact CSI Sales for more information about the Error Notification Service or contact sales for pricing. CSI does not report software errors directly to the NRC or any other agency. \r\n\t\t

\r\n CSiXCAD, a CSI developed plug-in for AutoCAD and BricsCAD, streamlines drawing production by directly interacting with ETABS and SAP2000. CSiXCAD provides a live link between structural models defined and maintained in ETABS or SAP2000 and the drawings documenting them in the CAD software. CSiXCAD generates a full 3-D model and automatically generates an initial set of drawings that can then be refined within the CAD software.\r\n

\r\n The link between Tekla Structures and SAP2000 or ETABS allows models to be started in either product, then transferred to the other. Round-tripping of models is possible, including accepting of changes when transferring from SAP2000 or ETABS to Tekla Structures. It is also possible to merge changes to a Tekla Structures model to an existing SAP2000 or ETABS model.\r\n

\r\n Support of IFC (Industry Foundation Classes) data models provides compatibility with other BIM enabled applications. SAP2000, CSiBridge, and ETABS all support import and export of IFC 2x3 and IFC 4 formats.\r\n

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\r\n If you purchased your software through one of our international channel partners and have questions regarding support, upgrades, or maintenance, please contact them directly.\r\n

\r\n\t\t\tWith a little programming knowledge, it is possible to create a spreadsheet, plugin or third-party application that can interface with CSI software. The API is compatible with most major programming languages including Visual Basic for Applications (VBA), VB.NET, C#, C++, Visual Fortan, Python, and Matlab. Whether you are a seasoned developer or new to programming, you will find the CSI API syntax easy and intuitive.\r\n\t\t\t

Starting with ETABS v18, SAP2000 v21, CSiBridge v21, and SAFE v20 it is now possible to develop cross-product API tools that work with all three products. This allows you to write the code once and use it in all three products. These versions of the API are also forward compatible to future major versions of these products without the need for recompiling.

\r\n\t\t\tThird-party developers, such as CAD and 3D modeling developers, can use the API to enable their software with all of the sophisticated analysis and design technology of CSI software. Developers can create rich and tight two-way links with CSI software, allowing for accurate transfer of models, complete control of execution, and extraction of analysis and design information, all from within their application. \r\n\t\t\t

\r\n\t\t\tThe CSI API offers direct, fast and efficient access to all of the advanced numerical methods of CSI software. It allows direct two-way transfer of information without intermediate files, providing fast throughput for large models. Use of the CSI API by third-party developers all but guarantees that their applications will remain compatible with future releases of CSI software, a nontrivial concern for both developers and users.\r\n\t\t\t

For qualified users and third-party developers who would like technical support to help them build solutions and integrations with CSI Products using the OAPI, CSI has created a subscription-based service, CSI Developer Network (CSIDN). Qualified developers may also be entitled to free licenses of CSI Products for integration development purposes. CSI reserves the right to qualify potential subscribers to CSIDN on a case by case basis.

CSI has long been at the forefront of software development and our products are used by the most sophisticated\r\n design professionals in over 160 countries worldwide. We are a company with an unmatched record of innovation\r\n and an unrivaled commitment to meeting the ever-evolving needs of the structural engineering profession. We are\r\n pleased to offer an excellent salary package plus benefits including 401(k), health coverage, dental coverage,\r\n vision coverage, and more.

Computers and Structures, Inc. (CSI) is seeking an experienced developer to join our\r\n development team in Walnut Creek, California where they will be tasked with improving the\r\n graphical display in our line of engineering analysis software, using DirectX or OpenGL. The\r\n chosen candidate shall be highly motivated and have a passion for computer graphics. This\r\n position will include development of new features, as well as improving the existing graphical\r\n display to make the end user experience more enjoyable and easy to use.

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