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Application of boundary element analysis for multiple seismic cracking in concrete gravity dams
EXCAVATIONS:FAILURE MECHANISMS design. The relationship between the system's asymmetry and its inelastic deformations is yet to be determined. This study defines the asymmetric building system and its key components namely the stiffness and strength eccentricities. The solution is mathematically formulated and its accuracy discussed. (from Authors)
966290 Behaviour of asymmetric building systems under a monotonic load - H A. Ferhi & K. Z. Truman, Engineering Structures, 18(2), 1996, pp 142-153. This study is a detailed examination of the effects of the stiffness and strength eccentricities on the inelastic bchaviour of the asymmetric building system. Results showing the asymmetric building system's deformations under possible combinations of stiffness and strength eccentricities are examined. Ultimately the questions of what type of deformations the asymmetric building system will undergo and what happens to its behaviour as it approaches collapse wil he answered. (from Authors) 966291 Application of boundary element analysis for multiple seismic cracking in concrete gravity dams V. Batta & O. A. Pekau, Earthquake Engineering & Structural Dynamics, 25(1), 1996, pp 15-30. A previously developed two-dimensional boundary element procedure for analysing the propagation of a single discrete crack is extended to simultaneous multiple cracking in concrete gravity dams. A brief discussion of the generalized methodology is presented and the validity of the extended procedure is verified by performing a fracture analysis of the Fongman dam and comparing the predicted rupture process with the available experimental results. The fracture response of the Koyna dam is then studied extensively under the Koyna earthquake. In relation to the phenomenon of hydrodynamic uplift pressure within propagating cracks, openings of the crack on the upstream face of the dam are examined in particular. Results indicate that this phenomenon is not expected to be significant during the crack development phase and hence unlikely to affect the final rupture characters. (from Authors) 966292 An investigation into the base sliding response of rigid concrete gravity dams to dynamic loading R. A. Mir & C. A. Taylor, Earthquake Engineering & Structural Dynamics, 25(1), 1996, pp 79-98. A series of dynamic slip tests on a concrete gravity dam model was conducted on a shaking table. The aim of the experiments was to investigate the dynamically induced sliding and overturning characteristics of a typical low height gravity dam monolith cracked at its base. Tests indicated that downstream sliding is the main instability that could be expected during an earthquake. A comparison of the experimental and analytical responses indicated that the seismically induced slip can be predicted reasonably by a contact surface algorithm implemented in a standard finite element package. A comparison of observed displacements with Newmark's sliding block displacements indicated that a conservative estimate of seismic induced slip of a gravity dam could be obtained by using this concept. (from Authors) 966293 Three-dimensional analysis of soil-steel bridges Y. Girges & G. Abdel-Sayed, Canadian Journal of Civil Engineering, 22(6), 1995, pp 1155-I 163. A three-dimensional finite element analysis is presented in this paper to examine the actual three-dimensional behaviour of soil-steel bridges. The thrust and bending moment around the conduit walls as well as the stability of a single conduit are presented and compared with the results obtained from planestrain analysis. Also, the live load dispersion in the soil above
277A
the conduit is examined and compared with some present codes. (Authors)
966294 Experimental study of FPS system in bridge seismic isolation P. Tsopelas, M. C. Constantinou, Y. S. Kim & S. Okamoto, Earthquake Engineering & Structural Dynamics, 25(1), 1996, pp 65-78. An experimental study of a seismically isolated and a comparable non-isolated bridge is presented. The bridge model featured flexible piers, weighed 158 kN and was tested on a shake table with an array of real and simulated seismic motions with peak acceleration in the range 0.1-1.1g. When isolated, the bridge deck was supported by four spherically shaped sliding bearings (known as Friction Pendulum System or FPS bearings) with friction coefficient under dynamic conditions in the range 0.07-0.12. The experimental results demonstrated a substantial improvement in the ability of the isolated bridge to sustain all levels of seismic excitation under elastic conditions. (Authors) 966295 Wave interaction with permeable coastal structures M. R. A. Van Gent, Communications on Hydraulic & Geotechnical Engineering - Delft University of Technology, 95-5, 1995, 177 pp. Wave interaction with permeable coastal structures is studied and discussed in this thesis. Physical processes involved in the hydraulic and structural response of coastal structures under wave attack are examined and predictive numerical models for wave interaction with permeable coastal structures are developed. Special attention is given to berm breakwaters. This relatively new type of rubble-mound structure reshapes under heavy storm conditions by redistributing the stones in the seaward profile. The reshaping of such dynamic structures is modelled numerically. (from Authors)
EXCAVATIONS Geological factors 966296 Engineering geological characterization of low strength anisotropic rocks in the Himalayan region for assessment of tunnel support R. Bhasin, N. Barton, E. Grimstad & P. Chryssanthakis, Engineering Geology, 40(3-4), 1995, pp 169-193. The project (the Nathpa Jhakri Hydroelectric Project) will have one of the world's largest and longest water conducting systems. Because these constructions are made in low strength metamorphosed anisotropic rocks like quartz mica schists, biotite schists and muscovite schists, it was necessary to undertake a comprehensive study. The studies include petrographic and petrofabric analyses of the rocks, geo-mechanical properties, rock stress measurements, rock mass classification using the Q-System and data concerning joint geometry, joint roughness and joint strength. The use of mapped geological and geotechnical data along with the experimental and modelling studies have helped to better understand the behaviour of these rocks in underground openings. (from Authors)
Excavation failure mechanisms 966297 Ring of confidence A. Oliver, New Civil Engineer (NCE), 1156, 1995, pp 10-11. This article reports on work in progress following the collapse of the Heathrow Express tunnel in 1994. A 60 m cofferdam will encircle the collapsed area. Work is underway to rebuild the wrecked concrete filled tunnels. Six new shafts have been sunk for access. Changes in tunnel design and construction
966290 Behaviour of asymmetric building systems under a monotonic load - H A. Ferhi & K. Z. Truman, Engineering Structures, 18(2), 1996, pp 142-153. This study is a detailed examination of the effects of the stiffness and strength eccentricities on the inelastic bchaviour of the asymmetric building system. Results showing the asymmetric building system's deformations under possible combinations of stiffness and strength eccentricities are examined. Ultimately the questions of what type of deformations the asymmetric building system will undergo and what happens to its behaviour as it approaches collapse wil he answered. (from Authors) 966291 Application of boundary element analysis for multiple seismic cracking in concrete gravity dams V. Batta & O. A. Pekau, Earthquake Engineering & Structural Dynamics, 25(1), 1996, pp 15-30. A previously developed two-dimensional boundary element procedure for analysing the propagation of a single discrete crack is extended to simultaneous multiple cracking in concrete gravity dams. A brief discussion of the generalized methodology is presented and the validity of the extended procedure is verified by performing a fracture analysis of the Fongman dam and comparing the predicted rupture process with the available experimental results. The fracture response of the Koyna dam is then studied extensively under the Koyna earthquake. In relation to the phenomenon of hydrodynamic uplift pressure within propagating cracks, openings of the crack on the upstream face of the dam are examined in particular. Results indicate that this phenomenon is not expected to be significant during the crack development phase and hence unlikely to affect the final rupture characters. (from Authors) 966292 An investigation into the base sliding response of rigid concrete gravity dams to dynamic loading R. A. Mir & C. A. Taylor, Earthquake Engineering & Structural Dynamics, 25(1), 1996, pp 79-98. A series of dynamic slip tests on a concrete gravity dam model was conducted on a shaking table. The aim of the experiments was to investigate the dynamically induced sliding and overturning characteristics of a typical low height gravity dam monolith cracked at its base. Tests indicated that downstream sliding is the main instability that could be expected during an earthquake. A comparison of the experimental and analytical responses indicated that the seismically induced slip can be predicted reasonably by a contact surface algorithm implemented in a standard finite element package. A comparison of observed displacements with Newmark's sliding block displacements indicated that a conservative estimate of seismic induced slip of a gravity dam could be obtained by using this concept. (from Authors) 966293 Three-dimensional analysis of soil-steel bridges Y. Girges & G. Abdel-Sayed, Canadian Journal of Civil Engineering, 22(6), 1995, pp 1155-I 163. A three-dimensional finite element analysis is presented in this paper to examine the actual three-dimensional behaviour of soil-steel bridges. The thrust and bending moment around the conduit walls as well as the stability of a single conduit are presented and compared with the results obtained from planestrain analysis. Also, the live load dispersion in the soil above
277A
the conduit is examined and compared with some present codes. (Authors)
966294 Experimental study of FPS system in bridge seismic isolation P. Tsopelas, M. C. Constantinou, Y. S. Kim & S. Okamoto, Earthquake Engineering & Structural Dynamics, 25(1), 1996, pp 65-78. An experimental study of a seismically isolated and a comparable non-isolated bridge is presented. The bridge model featured flexible piers, weighed 158 kN and was tested on a shake table with an array of real and simulated seismic motions with peak acceleration in the range 0.1-1.1g. When isolated, the bridge deck was supported by four spherically shaped sliding bearings (known as Friction Pendulum System or FPS bearings) with friction coefficient under dynamic conditions in the range 0.07-0.12. The experimental results demonstrated a substantial improvement in the ability of the isolated bridge to sustain all levels of seismic excitation under elastic conditions. (Authors) 966295 Wave interaction with permeable coastal structures M. R. A. Van Gent, Communications on Hydraulic & Geotechnical Engineering - Delft University of Technology, 95-5, 1995, 177 pp. Wave interaction with permeable coastal structures is studied and discussed in this thesis. Physical processes involved in the hydraulic and structural response of coastal structures under wave attack are examined and predictive numerical models for wave interaction with permeable coastal structures are developed. Special attention is given to berm breakwaters. This relatively new type of rubble-mound structure reshapes under heavy storm conditions by redistributing the stones in the seaward profile. The reshaping of such dynamic structures is modelled numerically. (from Authors)
EXCAVATIONS Geological factors 966296 Engineering geological characterization of low strength anisotropic rocks in the Himalayan region for assessment of tunnel support R. Bhasin, N. Barton, E. Grimstad & P. Chryssanthakis, Engineering Geology, 40(3-4), 1995, pp 169-193. The project (the Nathpa Jhakri Hydroelectric Project) will have one of the world's largest and longest water conducting systems. Because these constructions are made in low strength metamorphosed anisotropic rocks like quartz mica schists, biotite schists and muscovite schists, it was necessary to undertake a comprehensive study. The studies include petrographic and petrofabric analyses of the rocks, geo-mechanical properties, rock stress measurements, rock mass classification using the Q-System and data concerning joint geometry, joint roughness and joint strength. The use of mapped geological and geotechnical data along with the experimental and modelling studies have helped to better understand the behaviour of these rocks in underground openings. (from Authors)
Excavation failure mechanisms 966297 Ring of confidence A. Oliver, New Civil Engineer (NCE), 1156, 1995, pp 10-11. This article reports on work in progress following the collapse of the Heathrow Express tunnel in 1994. A 60 m cofferdam will encircle the collapsed area. Work is underway to rebuild the wrecked concrete filled tunnels. Six new shafts have been sunk for access. Changes in tunnel design and construction