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Modificed Elastic Beam

Description

The ModElasticBeam element uses linear-elastic section properties for axial, flexural, and torsional response of frame members along with stiffness modifiers for the flexural response. The element is defined by two nodes, section properties, flexural stiffness modifiers, and an optional mass density per length. The mass matrix formed for this element can either be lumped or consistent. A GeomTransf object defines the transformation of element response between the basic and global coordinate systems.

Syntax

For 2D models:

ops.element('ModElasticBeam',tag,ndI,ndJ,A,E,I,K11,K33,K44,transfTag,'-mass',rho,'-cMass')

For 3D models:

ops.element('ModElasticBeam',tag,ndI,ndJ,A,E,G,J,Iy,Iz,K11z,K33z,K44z,K11y,K33y,K44y,transfTag,'-mass',rho,'-cMass')

Parameters

• tag : integer Unique element identifer
• ndI : integer Tag of node at end I
• ndJ : integer Tag of node at end J
• E : float Elastic modulus
• A : float Cross-section area
• I : float Second moment of cross-section area (for 2D models)
• Iz : float Second moment of cross-section area about z-axis (for 3D models)
• Iy : float Second moment of cross-section area about y-axis (for 3D models)
• G : float Shear modulus (required for 3D models)
• J : float Second polar moment of cross-section area (for 3D models)
• K11 : float Modifier for basic stiffness term at end I (K11=4 for unmodified element)
• K33 : float Modifier for basic stiffness term at end J (K33=4 for unmodified element)
• K44 : float Modifier for basic stiffness term for I-J term (K44=2 for unmodified element)
• K11z,K33z,K44z : float Modifier for basic stiffness terms about local z-axis (for 3D models)
• K11y,K33y,K44y : float Modifier for basic stiffness terms about local y-axis (for 3D models)
• transfTag : integer Tag of geometric transformation

Optional Parameters

• rho : float Mass density per unit length
• -cMass : string When present, compute consistent mass matrix

Notes

• The modifiers can be used to give an equivalent combination of one elastic element with stiffness-proportional damping, and two springs at its two ends with no stiffness proportional damping to represent a prismatic section.
• The modifiers can also be calibrated to give different flexural responses depending on the element loading, e.g., sway and non-sway response.

Examples

ops.element('ModElasticBeam',1,1,2,20,29000,800,3.5,3.5,1.8,1)

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