Seismic Response Of Liquid-Filled Thin-Walled Steel Cylindrical Tanks

Seismic response plays an important role in the design of liquid-filled thin-walled steel cylindrical tanks because of the small thicknesses of the walls as compared to their diameter. The liquid-filled thin-walled cylindrical tanks are vulnerable when they are subjected to earthquake accelerations. This dissertation aims to estimate and improve the seismic buckling strength of the liquid-filled thin-walled steel cylindrical tanks under earthquake excitation. The structural response to the base excitation is modeled using the concept of effective earthquake forces. The time steps in numerical analysis are divided to be small enough to accurately capture the periods of oscillations. The finite element method (FEM) is compared with experimental results and theoretical equations available in the literature to ensure the accuracy of the numerical analysis. Based on the extensive parametric study, seismic design equations and design curves representing the interaction effects of the diameter-to thickness (D/t) and height to diameter (H/D) ratios for the liquid-filled thin-walled steel cylindrical tanks of various geometries subjected to different earthquakes are presented and discussed. Results reveal that the D/t ratio is an important parametric factor of the seismic buckling strength of the liquid-filled thin-walled cylindrical tank. The dynamic buckling capacity of the tank decreases significantly when the D/t ratio increases. An increase in the H/D ratio also seems to have a negative effect on the seismic buckling strength; however, its effect is less significant compared to the D/t ratio. The effects of geometrical imperfection on the seismic buckling strength of liquid-filled thin-walled cylindrical tanks. This study discovers that the seismic buckling strength of the tanks decreases significantly as the amplitudes of initial geometric imperfection are included. This study also introduces the improvement of seismic buckling strength of liquid-filled thin-walled cylindrical tanks due to vertical stiffeners. It is concluded that the vertical stiffeners improve the seismic buckling strength of the liquid-filled thin-walled steel cylindrical tanks when they are subjected to horizontal earthquake excitation. This study concludes that vertical stiffeners can improve the seismic buckling strength by at least 10% of the critical peak ground acceleration (PGA) of unstiffened liquid-filled thin-walled steel cylindrical tanks. Finally, this study proposes the new design criterion of the liquid-filled thin-walled steel cylindrical tanks which is the double-skin thin-walled composite tanks (DSTWCTs). The DSTWCT is constructed to have the same diameter (D) and height (H) as a single-skin thin-walled tank (SSTWT) with an equal volume of steel. DSTWCT consists of two skins which are inner and outer walls. The inner wall diameter of DSTWCT is equal to the diameter of SSTWT. The seismic design and numerical finite element models of DSTWCT are proposed. It is concluded that the seismic buckling capacity of DSTWCT substantially improves when the gap between double skins of DSTWCT is filled with concrete up to 50% of the height of the tank. The location of the seismic buckling of DSTWCT occurs at the hollow sections just above the surface of infill concrete and moves to the higher location as the concrete-filled ratio increases which in turn results in improved seismic buckling strength and ductility. Chapter six presents the conclusions and future study

Buckling Of Liquid-Filled Steel Storage Tanks Under Earthquake Loading

The static and dynamic buckling loads of cylindrical liquid storage tanks were studied in this thesis. Finite element analysis was performed using ANSYS computer program. Twelve different geometries of the cylindrical tanks were analyzed with height to diameter (H/D) ratios of 0.5, 1.0, 1.5, and 2.0 and the diameter to thickness (D/t) ratios of 1000, 1500, and 2000 to cover tall and short cylindrical tanks. The transient dynamic analysis was performed to find the dynamic buckling loads. Applied dynamic loads in this study are horizontal earthquake excitations in terms of acceleration (g) due to gravity. Budiansky and Roth procedure was used to find the dynamic buckling load for both empty and tanks filled with water up to 90% of their height. Analysis results show that the dynamic buckling loads in terms of peak ground accelerations (PGA) are very high which are unrealistic for any recorded earthquake. For the cylindrical tanks filled with water up to 90% of their height; on the other hand, the dynamics buckling loads are small, and these dynamic loads are less than some recorded real world earthquakes. The H/D and D/t ratios have the important roles in the design of earthquake stability for the cylindrical liquid storage tanks. Results from the transient dynamic analysis represent that the dynamic buckling loads decrease when the H/D ratios increase, and the dynamic buckling loads decrease when the D/t ratios increase. Furthermore, with different characteristics of the earthquakes, the dynamic buckling behaviors of the cylindrical tank are dissimilar. Design curves for the cylindrical tanks of various geometries subjected to different earthquakes were generated in this thesis

Impact response of high speed rail bridges and riding comfort of rail cars

[[abstract]]The vibration of simple and three-span continuous beams traveled by trains moving at high speeds is studied in this paper. Central to this study is the adoption of a dimensionless speed parameter S, defined as the ratio of the exciting frequency of the moving vehicles to the fundamental frequency of the beam. The numerical studies indicate that the moving load model is generally accurate for simulating the bridge response. However, the use of the sprung mass model is necessary whenever the riding comfort of rail cars is of concern. If the characteristic length, rather than the span length, is used for the continuous beam, then both the simple and continuous beams will reach their peak responses at the same critical speed S, when traveled by wheel loads of constant intervals. The rail irregularity, ballast stiffness, suspension stiffness and suspension damping can drastically affect the riding comfort of rail cars traveling over simple beams. Their effects are comparatively small for continuous beams. In conclusion, the design of a high speed rail bridge is governed primarily by the conditions of serviceability, rather than by strength.[[notice]]補正完畢[[journaltype]]國外[[booktype]]紙本[[countrycodes]]GB