simdesign.rcmrf.bnsm.dp05
BNSM DP05 Library
This package provides an instantiable distributed-plasticity (DP) modelling strategy within the Building Nonlinear Structural Model (BNSM), suitable for nonlinear seismic assessment of reinforced concrete (RC) moment-resisting frame buildings.
DP05 is DP03 (fiber-section beams and columns) with an axial release at one
end of each beam. The rigid floor diaphragm enforces zero axial strain in the
beams, whereas the axis of an RC beam with fiber sections elongates as the
section cracks and yields (the neutral axis moves towards the compression
face). With the diaphragm, this elongation is restrained and the beams
develop fictitious axial compression, which increases their flexural
strength and stiffness. In DP05, the beam frames into an auxiliary node at
its end section (j-end), connected to the joint by a zeroLength
element that is free along the beam axis and rigid in the other degrees of
freedom (an axial buffer element), so the beams can elongate freely.
Model Characteristics
Beam: As DP03 (force-based elements with fiber end sections), with an axial release at the j-end. The beams carry no axial force.
Column, Joints, Infill, Floor Diaphragm, Foundation: Identical to DP03.
Building: Aggregator class assembling all nonlinear components into a unified OpenSees domain. Extends the DP03 assembly by connecting the j-end of each beam to an auxiliary node through the axial release.
References
Priestley, M. J. N., Calvi, G. M., & Kowalsky, M. J. (2007). Displacement-based seismic design of structures. IUSS Press.
Mander, J. B., Priestley, M. J. N., & Park, R. (1988). Theoretical stress-strain model for confined concrete. Journal of Structural Engineering, 114(8), 1804-1826.
OpenSees Wiki. Rigid Diaphragm Consequences. https://opensees.berkeley.edu/wiki/index.php/Rigid_Diaphragm_Consequences