Mass and stiffness proportional damping sap2000 manual pdf download

There are many ways to compute a classical damping matrix from mass and stiffness matrices csi refer sap2000 ebook download as pdf file. A small amount of stiffness proportional damping is recommended to control higher modes. Hysteretic proportional damping, also mass and stiffness proportional, is used for steadystate and powerspectraldensity analyses. Effects of the improper modeling of viscous damping on the. As stated in the sap2000 analysis reference manual. Finite element steadystate vibration analysis considering. Since the modal mass, stiffness, and damping equations 4, 6, and 8 assume units of displacementforce, residues with units of.

The mass and stiffness proportional damping factors were initially set to produce. This paper investigates the consequence of using rayleigh proportional damping in the. Suitability for an incremental approach to numerical solution merits its use. Here, c m and c k are the mass and stiffnessproportional damping. Rayleigh damping is the main form in direct integral method for structural nonlinear dynamic analysis under seismic wave. For the cases of rotary inertia, point mass elements, and substructures, where. To define rayleigh damping, you specify two rayleigh damping factors. The csi analysis reference manual has been updated. Damping of stiff elements with inelastic softening technical. Damping devices may also be modeled as a structural subsystem, as described. Sparse proportional viscous damping model for structures. Pdf parametric study on equivalent damping ratio of different.

Parametric study on equivalent damping ratio of different composite structural building systems being applied to investigate the seismic performance of mixed steelconcrete frames. Modal analysis of mdof systems with proportional damping. As stated in the sap2000 analysis reference manual, for steadystate and powerspectraldensity cases, the hysteretic damping matrix is calculated as a linear combination of the stiffness matrix, scaled by coefficient d k, and the mass matrix, scaled by coefficient d m. However, the question fielded concerns modal damping. Pdf direct updating of damping and stiffness matrices. Mass and stiffness proportional damping, normally referred to as rayleigh damping, is commonly used in nonlineardynamic analysis. How can i determine the stiffness and damping coefficient of viscoelastic damper which is to be installed in a building. In general, damping is a material property specified as part of the material definition. How is damping specified for different parts of the structure. Unintended consequences of modeling damping in structures finley a.

During formulation, the damping matrix is assumed to be proportional to the mass and stiffness matrices as follows. Pdf computation of rayleigh damping coefficients for large. Damping technical knowledge base computers and structures. In structural analysis software such as sap2000, the desired nonclassical damping can be also modeled through specifying damping solely to the superstructure material. As stated in the sap2000 analysis reference manual, csi 2009 for steadystate and. Unintended consequences of modeling damping in structures. The structural analysis shall consider the relative stiffness of diaphragms and the vertical.

The rayleigh model consists of a mass proportional term and a stiffness proportional term. How can i determine the stiffness and damping coefficient. Damping faq technical knowledge base computers and. Parametric study on equivalent damping ratio of different. Viscous proportional damping is used for directintegration timehistory analysis. The two frequencypoint based rayleigh damping proportional to mass and stiffness in the direct integration analysis approximates the replacement of the. Mass proportional damping in nonlinear timehistory. This study proposes a proportional damping model that can be implemented as a sparse matrix without approximation nor iterative refinement, making it computationally. Modal mass, stiffness and damping by vibrant technology. Mass and tangent stiffness proportional rayleigh damping was used, with a damping ratio set equal to 5% for two frequencies.