- Email: [email protected]
Some applications of the boundary element method in geomechanics
Venturini, W S and Brebbia, C A 'Some applications of the boundary element method in geomechanics' Int. J. Numer. Anal. Methods in Geomechonics Vol 7 (1983) pp 4 1 9 - 4 3 3 The complete formulation for the application of the Boundary Element Method to solve nontension material problems is presented. The formulation is based on including an extra term due to an initial stress field into the boundary integral statement. This term is then used to iterate the solution until a state of nontension is achieved. The resulting iteration process is very simple to apply and basically consists only of a single matrix-vector product. The applications show that accurate results can be obtained for boundary discretizations involving a small number of unknowns. Whenever possible, results are compared with analytical solutions or finite elements. EI-Ghazaly~ H A, Dubey, R N and Sherbourne, A N 'Elasto-plastic buckling of stiffener plates in beam-column flange connections' Comput. Struct. Vol 18 No 2 (1984) pp 2 0 1 - 2 1 3 The problem of plastic buckling of steel plates is reviewed in relation to the loadcarrying capacity of stiffener plates in beamto-column flange connections. Because of the non-uniformity of the stress distribution in these plates, the finite element method is used to compute the stresses in the elastic and plastic ranges. A bifurcation analysis is performed using both flow and deformation theory to evaluate the elasto-plastic buckling of the stiffener. A parametric study is conducted on stiffeners and design curves are obtained showing the relationship between the critical stress and the slenderness ratio for different plate aspect ratios. Lai, S A and MacGregor, J G 'Geometric nonlinearities in unbraced multistorey frames' J. Struct. Division ASCE, Vol 109 No 11 (November 1983) pp 2528-2545 The geometric nonlinearities in elastic sway frames are examined. Various approximate methods of second-order analysis for sway frames are reviewed and the conditions limiting the use of these procedures are stated. A rational method for combining the nonsway and sway moments is developed. A practical method is derived of including the effects of sway deflections due to gravity load moments and out-of-plumb construction in the approximate second order analysis. Fillipou, F C, Popov, E P and Bertero, V V 'Modeling of R/C joints under cyclic excitations' j, Struct. Division ASCE, Vo1109 No 11 (November 1983) pp 2 6 6 6 - 2 6 8 4 An accurate and efficient analytical model
112
describing the hysteretic behaviour of R/C beam-column joints subjected to random cyclic excitations is presented. The model takes into account the cyclic bond deterioration along anchored bars as well as the hysteretic behaviour of cracked R/C sections at beam-column interfaces, thus allowing consideration of the interaction between the two end sections of the joint. Bicanic, N and Zienkiewicz, O C 'Constitutive model for concrete under dynamic loading' Earthquake Eng. Struct. Dyn. J. Vol 11 (Septembe~r-October 1983) pp 6 8 9 - 7 1 0 A rate and history-dependent numerical model for plain concrete under seismic loading conditions is proposed. The model follows the modified Perzyna' theory of elasto/viscoplasticity employing the stressrate sensitive fluidity parameter and two surfaces in the principle stress space. A discontinuity surface defines the departure from elasticity, and a strength limit surface serves as a damage monitoring device and to initiate the degradation of the discontinuity surface once the stress point reaches the limiting strength level. A general model concept is given together with the detailed description of the model version, based entirely on uniaxial test data.
Mejia, L H and Seed, H B 'Comparison of 2-D and 3-D dynamic analyses of earth dams' J. Geotech. Eng. Division ASCE, Vol 109 No 11 (November 1983) pp 1383--1398 Considerable judgement is required to estimate the overall 3D dynamic response of a dam in a narrow canyon from plane strain analyses of individual sections of the dam. Accordingly, the purpose of this paper is to present a comparison between the results of 3D and 2D dynamic analyses of two dams with different canyon geometries. From this comparison are determined the conditions under which 3D behaviour is of importance in the dynamic response of a dam. The applicability of 2D analyses for the determination of the dynamic behaviour of dams in steep walled canyons is also evaluated. Park, R and Falconer, T J 'Ductility of prestressed concrete piles subjected to simulated seismic loading' J. Prestressed Concr. Inst. Vol 28 No 5 (SeptemberOctober 1983) pp 1 1 2 - 1 4 4 The available ductility of prestressed concrete piles when subjected to large inelastic deformations due to severe earthquake loading is considered. The results of tests and analyses of five pretensioned prestressed concrete piles with a 400mm (15.7 in) octagonal cross-section are reported. The results showed that when a satisfactory quantity of spiral reinforcement is present,
the piles were capable of undergoing large post-elastic deformations when subjected to cyclic lateral loading without significant loss in toad-carrying capacity. Streeter, V L 'Transient cavitating pipe flow'
J. Hydrau/. Eng. Division ASCE, Vol 109 No I I (November 1983) pp 1 4 0 8 - 1 4 2 3 When a liquid column in a pipeline is pulled apart by the upstream velocity being less than the downstream velocity for a sufficient period of time, cavitating flow occurs over portions of the pipeline. The cavitating flow, with vapour pressure at its surface, is acted on by friction and by gravity. Analytical equations are developed which yield vaporous velocity and vapour fraction as functions of time and distance throughout the cavitating reglons. A program which includes these concepts permits transients in piping systems to be calculated for several boundary conditions. Comparisons with experiment and with other methods are presented. Jain, P C and Rao, M N G 'Analysis of steel frames under fire environment' Int. J. Numer. Methods Eng. Vol 19 (September 1983) pp 1 4 6 7 - 1 4 7 8 A numerical technique is developed using an implicit time-marching scheme to study the deformation history of steel building frames in fire, by considering the change in material properties due to rise of temperature, effect of creep and large deformations. A computer program has been developed for the analysis of plane frames based on the above algorithm using incremental and iterative procedures. Based on such a study, the length of time for which the structure can perform its function without either local or overall failure can be predicted. McGuire, W and Pesquera, C I 'Interactive computer graphics in steel analysis/design' Eng. J. Am. Inst. Steel Construct. Vol 20 No 3 (1983) pp 8 9 - 1 0 2 This is a progress report of research on the development of a CAD system that will provide for the description of a 2D or 3D steel frame to the computer, preliminary and final analyses of the frame, and a review of its adequacy under both service and ultimate loads. Included are provisions for conducting interactively the normal iterative procedures for refining a trial design to its final state. Several levels of analysfs are available, from conventional linear elastic analysis to full geometric and material nonlinear analysis. The capabilities of the system as it exists at present are illustrated through a series of pictures of graphical displays.
S Sutharshana
c o m p u t e r - a i d e d design
112
describing the hysteretic behaviour of R/C beam-column joints subjected to random cyclic excitations is presented. The model takes into account the cyclic bond deterioration along anchored bars as well as the hysteretic behaviour of cracked R/C sections at beam-column interfaces, thus allowing consideration of the interaction between the two end sections of the joint. Bicanic, N and Zienkiewicz, O C 'Constitutive model for concrete under dynamic loading' Earthquake Eng. Struct. Dyn. J. Vol 11 (Septembe~r-October 1983) pp 6 8 9 - 7 1 0 A rate and history-dependent numerical model for plain concrete under seismic loading conditions is proposed. The model follows the modified Perzyna' theory of elasto/viscoplasticity employing the stressrate sensitive fluidity parameter and two surfaces in the principle stress space. A discontinuity surface defines the departure from elasticity, and a strength limit surface serves as a damage monitoring device and to initiate the degradation of the discontinuity surface once the stress point reaches the limiting strength level. A general model concept is given together with the detailed description of the model version, based entirely on uniaxial test data.
Mejia, L H and Seed, H B 'Comparison of 2-D and 3-D dynamic analyses of earth dams' J. Geotech. Eng. Division ASCE, Vol 109 No 11 (November 1983) pp 1383--1398 Considerable judgement is required to estimate the overall 3D dynamic response of a dam in a narrow canyon from plane strain analyses of individual sections of the dam. Accordingly, the purpose of this paper is to present a comparison between the results of 3D and 2D dynamic analyses of two dams with different canyon geometries. From this comparison are determined the conditions under which 3D behaviour is of importance in the dynamic response of a dam. The applicability of 2D analyses for the determination of the dynamic behaviour of dams in steep walled canyons is also evaluated. Park, R and Falconer, T J 'Ductility of prestressed concrete piles subjected to simulated seismic loading' J. Prestressed Concr. Inst. Vol 28 No 5 (SeptemberOctober 1983) pp 1 1 2 - 1 4 4 The available ductility of prestressed concrete piles when subjected to large inelastic deformations due to severe earthquake loading is considered. The results of tests and analyses of five pretensioned prestressed concrete piles with a 400mm (15.7 in) octagonal cross-section are reported. The results showed that when a satisfactory quantity of spiral reinforcement is present,
the piles were capable of undergoing large post-elastic deformations when subjected to cyclic lateral loading without significant loss in toad-carrying capacity. Streeter, V L 'Transient cavitating pipe flow'
J. Hydrau/. Eng. Division ASCE, Vol 109 No I I (November 1983) pp 1 4 0 8 - 1 4 2 3 When a liquid column in a pipeline is pulled apart by the upstream velocity being less than the downstream velocity for a sufficient period of time, cavitating flow occurs over portions of the pipeline. The cavitating flow, with vapour pressure at its surface, is acted on by friction and by gravity. Analytical equations are developed which yield vaporous velocity and vapour fraction as functions of time and distance throughout the cavitating reglons. A program which includes these concepts permits transients in piping systems to be calculated for several boundary conditions. Comparisons with experiment and with other methods are presented. Jain, P C and Rao, M N G 'Analysis of steel frames under fire environment' Int. J. Numer. Methods Eng. Vol 19 (September 1983) pp 1 4 6 7 - 1 4 7 8 A numerical technique is developed using an implicit time-marching scheme to study the deformation history of steel building frames in fire, by considering the change in material properties due to rise of temperature, effect of creep and large deformations. A computer program has been developed for the analysis of plane frames based on the above algorithm using incremental and iterative procedures. Based on such a study, the length of time for which the structure can perform its function without either local or overall failure can be predicted. McGuire, W and Pesquera, C I 'Interactive computer graphics in steel analysis/design' Eng. J. Am. Inst. Steel Construct. Vol 20 No 3 (1983) pp 8 9 - 1 0 2 This is a progress report of research on the development of a CAD system that will provide for the description of a 2D or 3D steel frame to the computer, preliminary and final analyses of the frame, and a review of its adequacy under both service and ultimate loads. Included are provisions for conducting interactively the normal iterative procedures for refining a trial design to its final state. Several levels of analysfs are available, from conventional linear elastic analysis to full geometric and material nonlinear analysis. The capabilities of the system as it exists at present are illustrated through a series of pictures of graphical displays.
S Sutharshana
c o m p u t e r - a i d e d design