排序方式： 共有38条查询结果，搜索用时 15 毫秒
11.
Carl T. F. Ross Andrew P. F. Little Leonidas Chasapides Jeff Banks Daniele Attanasio 《Ocean Engineering》2004,31(2):239-252
The paper reports on the buckling of three ring-stiffened prolate domes under external hydrostatic pressure. The study was partly theoretical and partly experimental, where in the case of the latter, the finite element was used. Comparison between experiment and theory was good. The effect of ring stiffening the domes was to increase their buckling resistances by factors varying from 4.43 to 5.72. 相似文献
12.
C. T. F. Ross Bak Hock Huat Tay Boon Chei Chai Min Chong M. D. A. Mackney 《Ocean Engineering》2003,30(5):691-705
The paper reports on a theoretical and an experimental investigation into six GRP hemi-ellipsoidal dome shells, which were tested to destruction under external hydrostatic pressure. All six domes were of oblate shape and of three different aspect ratios. Each aspect ratio consisted of two dome shells, one made from two layers of glass fibre and one made from three layers of glass fibre. The theoretical analysis was via the finite element method where a non-linear theory was used which allowed for both geometrical and material non-linearity. Comparison between theory and experiment was good. 相似文献
13.
The soil resistance developed during temperature- and pressure-induced large lateral movements of shallowly embedded subsea flowlines is an important input parameter for the structural design process. A major source of uncertainty in calculation of the soil resistance is the undrained shear strength of the soil berm produced as the flowline moves across the seabed, which is affected by the level of remoulding. To investigate the effect of pipeline embedment and displacement amplitude on the shear strength of the berm, a set of centrifuge model tests was conducted on kaolin clay, involving laterally moving pipelines with constant embedments in the range 5%–35% of the pipe diameter. Back-analysis of the test results, using finite element limit analysis, showed that the shear strength of the soil berm is a function of pipe displacement amplitude, pipe embedment, and soil sensitivity. On the basis of these results, we propose that the overall berm undrained shear strength may be determined as a convolution of the shear strengths of its constituent soil elements. Finally, a formula is presented for calculating the shear strength of soil elements within the soil berm, and this is used to back-analyse the overall soil berm resistance from the model tests. 相似文献
14.
The buckling and vibration of tube-stiffened axisymmetric shells under external hydrostatic pressure 总被引：1，自引：0，他引：1
The paper reports on a theoretical and an experimental investigation into the buckling and vibration of prolate hemi-ellipsoidal tube-stiffened domes under external water pressure. The theoretical analyses were via the finite element method, where both the fluid and the structure were modelled with finite elements. The dome was modelled with a varying meridional curvature element and with eight displacement degrees of freedom and the water was modelled by solid annular elements where each element had eight pressure degrees of freedom in its cross-section. Comparison was good between experiment and theory. 相似文献
15.
The failure mechanism of a Late Glacial Sturzstrom in the Subalpine Molasse (Leckner Valley, Vorarlberg, Austria) 总被引：2，自引：0，他引：2
A number of prehistoric landslides and rock avalanches occurred in the folded and faulted section of the Molasse Zone in Vorarlberg, Austria. Some developed into a Sturzstrom, defined as a ‘rapidly moving fluidised mass movement of large volumes of rock, derived from the disintegration of a falling rock mass, that spread under the influence of gravity’. Their impact on the landscape usually is related to obstruction of rivers and valleys.In this paper, we analyse the geomorphology and the failure mechanism of a relative small ‘Sturzstrom’. The failure mechanism can be described as a ‘buckling failure’. The morphological situation indicates that failure took place after local deglaciation by the end of the Upper Würm. The period of failure coincides with glacial and ice-marginal remnants, which developed between 15.000 and 14.600 BP. The lithological sequence and rock structure, as well as the impact of the processes related to the former glacial environment, were major causal conditions. The rock sequence consists of conglomerates, sandstone layers, and marls. Next to glacial scouring, which increased the inclination of the valley slopes, the effect of late-glacial unloading and postglacial processes, such as weathering and fluvial erosion, subsequently weakened the mass rock fabric until failure occurred.Discontinuity orientation measurements, geostructural and geomechanical conditions, and the former hydrological and geomorphological conditions support bucklings failure. In fact, three-hinge buckling may have occurred. The frontal section of the Sturzstrom consists mainly of large conglomerate blocks, averaging 1.5 m3 in volume, although megablocks, reaching of up to 4000 m3, are present as well. The volume of the entire Sturzstrom equals approximately 10×107 m3. Present activity is only restricted to minor rock falls derived from the conglomerates and mudflows originating from the marl layers. 相似文献
16.
Local buckling of submarine pipelines is unavoidable under extreme conditions and it can propagate along the pipeline. Thus, arrestors are installed in a periodic placement along the pipeline to limit the extent of catastrophic collapse between two adjacent arrestors. Generally, the integral buckle arrestors are crossed by two modes: the flattening mode and the flipping mode. This paper focuses on the cross-over mechanisms of arrestors by analyzing results from experiments and numerical simulations. Fifteen groups of full-scale and reduced-scale physical experiments are conducted to investigate the effect of local ovality of the downstream pipes on the arrestor performance. Furthermore, an extensive parametric study of cross-over modes of arrestors is performed by FE models to supplement the experimental results. It is found that the local ovality of the downstream pipes impacts the cross-over modes of integral buckle arrestors, which is more likely to deform by ovalization in the same sense as the local ovality. On the other hand, a new formula involving the major geometric and material characteristics of pipes and arrestors is proposed to estimate the flattening mode and the flipping mode of arrestors when the downstream pipes are intact. And the switch point of the two cross-over modes is 0.265. 相似文献
17.
Collapse and/or severe damage to pile-supported structures are still observed in liquefiable soils after most major earthquakes.
Poor performance of pile foundations remains a great concern to the earthquake engineering community. This review paper compares
and contrasts the two plausible theories on pile failure in liquefiable soils. The well established theory of pile failure
is based on a flexural mechanism; where the lateral loads on the pile (due to inertia and/or lateral spreading) induce bending
failure. This theory is well researched in the recent past and assumes that piles are laterally loaded beams. A more recent
theory based on buckling instability treats the piles as laterally unsupported slender columns in liquefiable soils and investigates
the buckling instability (bifurcation). The objective of this paper is to investigate the implications to practical pile foundation
design that flow from both these theories. Provisions for design made by major international codes of practice for pile design
including the Japanese Highway Code (JRA) will be considered. The necessity for such codes to consider alternative forms of
failure mechanisms such as the buckling instability of piles in liquefied ground will be discussed.
S. Bhattacharya–Previously Departmental Lecturer in Engineering Science, University of Oxford, UK and Fellow of Somerville
College, Oxford. S. P. G. Madabhushi–Fellow of Girton College, Cambridge. 相似文献
18.
Sarah E. Mouring 《Ocean Engineering》1999,26(8):793
The U.S. shipbuilding industry recently has started incorporating composite materials in the construction of both military and commercial ships due to the advantages of composite construction. These advantages include the reduction in total life costs, corrosion resistance, high strength- and stiffness-to-weight ratios, and improved stealth for military applications. One disadvantage is the higher costs of composites compared to steel and other conventional materials. Therefore, new higher quality materials with lower costs and new fabrication methods need to be developed before composite materials will be fully accepted for the construction of large ships. A new composite preform framing technology shows promise in the reduction of fabrication costs for large ship construction. There already has been significant cost savings using this framing technology in the construction of small recreational boats and large yachts. This framing technology involves casting a dry glass fiber-reinforced plastic (GRP) fabric into shape in a closed mold with a foam core. One unresolved issue using this framing technology is the orientation of the fiber for the frames. This paper summarizes experimental results of the testing of composite panels stiffened with preform frames under in-plane uniaxial compressive loads. Biaxial (0,90), quadaxial (0,90,+45,−45), and triaxial (+45,−45,0) laminates were used in the frames. 相似文献
19.
L. De Chant 《Engineering Geology》1998,50(3-4):329-335
Folds and faults in the Devonian shales of the Berea area, Ohio have been analyzed on a small scale (several meters) to determine their method of formation. A simple elastic model has been developed to account for stress concentration due to lithostatic pressures induced by local relief. This analytical model is then coupled to the beam–column buckling stability theory. The possibility of failure due to faulting is also examined using the Coulomb criterion. Initial results indicate that local stresses due to topography are a probable cause of these structures, though the possible role of regional tectonic effects cannot be eliminated. The state of the local stress field and the possibility of seismic events have important implications for surface and subsurface design problems. 相似文献
20.
A finite element method is developed for the stiffened multi-layered airfoil/hydrofoil structure for the large deformation and finite strain problem. The kinematics of the airfoil/hydrofoil is set up. The Consistent Orthogonal Basis Function Space is applied for the airfoil/hydrofoil structure. Given the airfoil/hydrofoil configuration and boundary conditions, the basis function space can be uniquely determined, such that the diagonal mass matrix is obtained accurately and the basis functions are very identical with the mode shape functions of the structure. In order to satisfy the displacement compatibility condition between adjacent layers of the airfoil/hydrofoil, the traction degree-of-freedom is also induced.The post buckling analysis is presented for the wing (hydrofoil) structure of the underwater glider. The water pressure is applied on the outer surface and the critical buckling pressure is calculated. The post buckling equilibrium path is also given. The results are verified with ANSYS. The present study of the buckling analysis of the airfoil/hydrofoil under water pressure is helpful to the design of underwater glider. 相似文献