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Pseudodynamic testing of strain-softening systems with adaptive time steps
36A
UNDERGROUND EXCAVATIONS:OPENING STRESS
structure is also carried out. It is shown that the HD-LRB system significantly reduces the mean-square, as well as the peak acceleration and deflection responses without generating large base displacements. Furthermore, the non-linear behaviour of the HD-LRB somewhat improves the performance of the bearing in reducing the peak responses of the secondary system and the primary structure when compared with the linear LRB model. (from Authors)
951260 Pseudedynamic testing of strain-softening systems with adaptive time steps O. S. Bursi, Pui-Shum B. Shing & Z. Radakovic-Guzina, Earthquake Engineering & Structural Dynamics, 23(7), 1994, pp 745-760. A structure may exhibit a severe strain-softening behaviour when subjected to strong earthquake excitation. Pseudodynamic testing of such structures using an implicit timeintegration algorithm may be conceived of as a problem, since the Newton-type iterations, which are often required when structural non-linearity develops, may not converge under these circumstances. An unconditionally stable implicit timeintegration algorithm implemented with Newton-type iterations is analysed to provide an insight into this problem. A simple convergence condition is derived to detect possible divergence. The condition is shown to be a sufficient criterion for convergence for general multiple-degree-of-freedom structures, and it is used to develop an adaptive timestepping strategy to avoid divergence under severe strainsoftening conditions. (from Authors)
951261 An inelastic substructure technique for the pseudodynamic test method S. P. Schneider & C. W. Roeder, Earthquake Engineering & Structural Dynamics, 23(7), 1994, pp 761-775. An inelastic substructure technique for the pseudodynamic test method is described. This technique requires testing of only a critical component of a multi-degree-of-freedom structure, while the remaining portion is modelled using standard inelastic analytical procedures. This paper describes the development of a substructure algorithm which is verified with a numerically s~aulated test. (from Authors)
951262 Inelastic seismic response of torsionally unbalanced systems designed using elastic dynamic analysis C. M. Wong & W. K. Tso, Earthquake Engineering & Structural Dynamics, 23(7), 1994, pp 777-798. This paper evaluates the inelastic seismic response of torsionally unbalanced structural systems with strength distributed using elastic response spectrum analysis. It is shown that the inelastic responses depend strongly on the torsional stiffness of the system. For a torsionally stiff system, the torsional response leads to a decrease in the stiff edge displacement; however, for a torsionally flexible system, it tends to increase the stiff edge displacement. With accidental torsion effect incorporated, the response spectrum analysis will give a strength distribution such that there will be no excessive additional ductility demands on the lateral load resisting elements. (from Authors)
951263 Seismic rnndom-vibration analysis of multisupport-strucrural systems E. Heredia-Zavoni & E. H. Vanmarcke, Journal of Engineering Mechanics - ASCE, 120(5), 1994, pp 1107-1128.
A random-vibration methodology is formulated for the seismic-response analysis of linear multisupport-structural systems. It reduces the response evaluation to that of a series of linear one-degree systems in a way that fully accounts for the multiple-support input and the space-time correlation structure of the ground motion. Three spectral parameters are introduced and interpreted in terms of cross-correlation coefficients and spectral moments associated with the response of one-degree systems. The influence of localspatial variation of ground motion on the spectral parameters is also studied. (Authors)
951264 Analysis of embedded foundations by substructure-deletion method R. Betti & A. M. Abdel-Ghaffar, Journal of Engineering Mechanics - ASCE, 120(6), 1994, pp 1283-1303. An alternative formulation of the substructure-deletion method for the dynamic analysis of thrce-dimensional embedded foundations of arbitrary shape subjected to applied external forces and to incoming seismic waves is presented. The analysis is performed in the frequency domain, and the foundations are assumed to be rigid and embedded in a homogeneous viscoelastic half-space, with welded contact along the embedded surface. This new formulation of the substructure-deletion method is characterized by a boundaryintegral approach for the analysis of the removed soil inclusion, using Green's functions for an infinite viscoelastic medium, while half-space Green's functions are applied in the analysis of the fiat half-space. (from Authors)
951265 Seismic shear demand of ductile cantilever walls: a Canadian code perspective A. Filiatrault, D. D'Aronco & R. Tinawi, Canadian Journal of Civil Engineering, 21(3), 1994, pp 363-376. During severe earthquakes, ductile flexural walls are expected to exhibit inelastic flexural behaviour while other brittle deformation mechanisms, such as shear, should remain elastic. The philosophy of the Canadian seismic provisions for flexural walls is based on the assumption that the force reduction factor is applicable to both flexure and shear. If the bended moments are limited because of the flexural strength of a wall, then the shear forces are considered to be limited by the same ratio. Brittle shear failures in walls are still possible even if their shear strengths are established by the Canadian standards. This paper presents an analytical investigation on the shear demand of ductile flexural walls designed for three different seismic zones in Canada. (from Authors)
UNDERGROUND EXCAVATIONS Stresses around underground openings 951266 Excavation of gaHerles in deep clay formations: an analytical tool for the control of finite element results D. J. De Bruyn, C. C. Ramaeckers & P. J. Huergo, Computers & Geotechnics, 16(3), 1994, pp 247-260. The equations of pressure and displacement equilibrium in an elastic perfectly plastic medium are presented for both spherical and cylindrical symmetry. The excavation of a gallery in a deep clay formation is then modelled and the displacements behind the tunnel face may be estimated. Numerical simulations are compared to field data; within the limitation of the hypotheses taken into account, the compar-
UNDERGROUND EXCAVATIONS:OPENING STRESS
structure is also carried out. It is shown that the HD-LRB system significantly reduces the mean-square, as well as the peak acceleration and deflection responses without generating large base displacements. Furthermore, the non-linear behaviour of the HD-LRB somewhat improves the performance of the bearing in reducing the peak responses of the secondary system and the primary structure when compared with the linear LRB model. (from Authors)
951260 Pseudedynamic testing of strain-softening systems with adaptive time steps O. S. Bursi, Pui-Shum B. Shing & Z. Radakovic-Guzina, Earthquake Engineering & Structural Dynamics, 23(7), 1994, pp 745-760. A structure may exhibit a severe strain-softening behaviour when subjected to strong earthquake excitation. Pseudodynamic testing of such structures using an implicit timeintegration algorithm may be conceived of as a problem, since the Newton-type iterations, which are often required when structural non-linearity develops, may not converge under these circumstances. An unconditionally stable implicit timeintegration algorithm implemented with Newton-type iterations is analysed to provide an insight into this problem. A simple convergence condition is derived to detect possible divergence. The condition is shown to be a sufficient criterion for convergence for general multiple-degree-of-freedom structures, and it is used to develop an adaptive timestepping strategy to avoid divergence under severe strainsoftening conditions. (from Authors)
951261 An inelastic substructure technique for the pseudodynamic test method S. P. Schneider & C. W. Roeder, Earthquake Engineering & Structural Dynamics, 23(7), 1994, pp 761-775. An inelastic substructure technique for the pseudodynamic test method is described. This technique requires testing of only a critical component of a multi-degree-of-freedom structure, while the remaining portion is modelled using standard inelastic analytical procedures. This paper describes the development of a substructure algorithm which is verified with a numerically s~aulated test. (from Authors)
951262 Inelastic seismic response of torsionally unbalanced systems designed using elastic dynamic analysis C. M. Wong & W. K. Tso, Earthquake Engineering & Structural Dynamics, 23(7), 1994, pp 777-798. This paper evaluates the inelastic seismic response of torsionally unbalanced structural systems with strength distributed using elastic response spectrum analysis. It is shown that the inelastic responses depend strongly on the torsional stiffness of the system. For a torsionally stiff system, the torsional response leads to a decrease in the stiff edge displacement; however, for a torsionally flexible system, it tends to increase the stiff edge displacement. With accidental torsion effect incorporated, the response spectrum analysis will give a strength distribution such that there will be no excessive additional ductility demands on the lateral load resisting elements. (from Authors)
951263 Seismic rnndom-vibration analysis of multisupport-strucrural systems E. Heredia-Zavoni & E. H. Vanmarcke, Journal of Engineering Mechanics - ASCE, 120(5), 1994, pp 1107-1128.
A random-vibration methodology is formulated for the seismic-response analysis of linear multisupport-structural systems. It reduces the response evaluation to that of a series of linear one-degree systems in a way that fully accounts for the multiple-support input and the space-time correlation structure of the ground motion. Three spectral parameters are introduced and interpreted in terms of cross-correlation coefficients and spectral moments associated with the response of one-degree systems. The influence of localspatial variation of ground motion on the spectral parameters is also studied. (Authors)
951264 Analysis of embedded foundations by substructure-deletion method R. Betti & A. M. Abdel-Ghaffar, Journal of Engineering Mechanics - ASCE, 120(6), 1994, pp 1283-1303. An alternative formulation of the substructure-deletion method for the dynamic analysis of thrce-dimensional embedded foundations of arbitrary shape subjected to applied external forces and to incoming seismic waves is presented. The analysis is performed in the frequency domain, and the foundations are assumed to be rigid and embedded in a homogeneous viscoelastic half-space, with welded contact along the embedded surface. This new formulation of the substructure-deletion method is characterized by a boundaryintegral approach for the analysis of the removed soil inclusion, using Green's functions for an infinite viscoelastic medium, while half-space Green's functions are applied in the analysis of the fiat half-space. (from Authors)
951265 Seismic shear demand of ductile cantilever walls: a Canadian code perspective A. Filiatrault, D. D'Aronco & R. Tinawi, Canadian Journal of Civil Engineering, 21(3), 1994, pp 363-376. During severe earthquakes, ductile flexural walls are expected to exhibit inelastic flexural behaviour while other brittle deformation mechanisms, such as shear, should remain elastic. The philosophy of the Canadian seismic provisions for flexural walls is based on the assumption that the force reduction factor is applicable to both flexure and shear. If the bended moments are limited because of the flexural strength of a wall, then the shear forces are considered to be limited by the same ratio. Brittle shear failures in walls are still possible even if their shear strengths are established by the Canadian standards. This paper presents an analytical investigation on the shear demand of ductile flexural walls designed for three different seismic zones in Canada. (from Authors)
UNDERGROUND EXCAVATIONS Stresses around underground openings 951266 Excavation of gaHerles in deep clay formations: an analytical tool for the control of finite element results D. J. De Bruyn, C. C. Ramaeckers & P. J. Huergo, Computers & Geotechnics, 16(3), 1994, pp 247-260. The equations of pressure and displacement equilibrium in an elastic perfectly plastic medium are presented for both spherical and cylindrical symmetry. The excavation of a gallery in a deep clay formation is then modelled and the displacements behind the tunnel face may be estimated. Numerical simulations are compared to field data; within the limitation of the hypotheses taken into account, the compar-