Juan Virella - Profile on Academia.edu (original) (raw)
Papers by Juan Virella
Journal of Sound and Vibration, 2008
The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure d... more The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks.
The damage due to buckling in thin-walled, short cylindrical aboveground tanks is discussed in th... more The damage due to buckling in thin-walled, short cylindrical aboveground tanks is discussed in this paper. Various sources of buckling are considered, including wind, earthquake, support settlement and vacuum during emptying of the tank. In all cases the tanks were modeled using finite elements, and the results include the buckling load and associated buckling mode, and the postbuckling equilibrium path. The results have been obtained using the computer packages ABAQUS and ALGOR. Experiments on flexible small-scale tanks with settlement of the supports on a sector of the foundation were conducted. Also, wind tunnel tests were carried out on rigid tanks with and without a roof to evaluate the pressure distribution due to wind.
Journal of Sound and Vibration, 2008
The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure d... more The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks. r
Engineering Structures, 2003
The influence of a fixed roof on the natural periods of vibrations of thin-walled aboveground ste... more The influence of a fixed roof on the natural periods of vibrations of thin-walled aboveground steel tanks with clamped boundary conditions at the base is studied. Tanks with open-top, self-supported roofs, and roofs supported by rafters are considered, along with different tank aspect ratios. The self-supported roof geometries considered include dome, cone, shallow cone, and flat roofs; whereas the rafters supported roofs geometries study cone, shallow cone, and flat roofs. The effect of the aspect ratio, along with the roof configuration on the natural periods is discussed. It was found that the vibration of empty tanks with a fixed roof is dictated either by cylinder modes or roof modes of vibrations. For self-supported roofs predominant roof modes resulted, whereas for tanks with roofs supported by rafters, cylinder modes dominate the dynamic behavior of the tank. Roof dominant modes had natural periods that remain constant regardless of the aspect ratio considered. Cylinder modes, on the other hand, were characterized by natural periods that showed a linear dependence with the aspect ratio of the tank.
Journal of Vibration and Control, 2005
In this paper we investigate the influence of hydrostatic pressure and self-weight loads (pre-str... more In this paper we investigate the influence of hydrostatic pressure and self-weight loads (pre-stress state) on the natural periods and mode shapes of steel cylindrical tanks and on the response under horizontal motions. The tank structure is modeled with finite elements and added mass models are used to represent the liquid. Only the impulsive component of the hydrodynamic response is considered. The natural periods and mode shapes for tank-liquid systems including and neglecting the effect of the pre-stress state are computed and compared. Three tank-liquid systems with different cylinder height to diameter ratios and slenderness ratios are considered. The numerical results show that the pre-stress state has a significant influence in the natural periods and mode shapes of tank-liquid systems with thinner walls1 however, for thicker shells this effect is reduced. When the pre-stress state is neglected and included, the smaller differences in natural periods occur, for modes characterized by small circumferential wavenumbers. The steady-state response of a tank-liquid system to horizontal harmonic base accelerations was also computed. Large differences were found when the pre-stress state was neglected. A comparison of the frequency response functions shows that the peak responses occur at quite different load periods and they have significantly different amplitudes. 1 12005 Sage Publications 1196 J. C. VIRELLA ET AL.
Engineering Structures, 2006
This paper reports results on the fundamental impulsive modes of vibration of cylindrical tank-li... more This paper reports results on the fundamental impulsive modes of vibration of cylindrical tank-liquid systems anchored to the foundation under horizontal motion. The analyses are performed using a general purpose finite element (FE) program, and the influence of the hydrostatic pressure and the self-weight on the natural periods and modes is considered. The roof and walls are represented with shell elements and the liquid is modeled using two techniques: the added mass formulation and acoustic finite elements. Tank height to diameter ratios from 0.40 to 0.95 were used, with a liquid level at 90% of the height of the cylinder. The effect of the geometry on the fundamental modes for the tank-liquid systems is studied using eigenvalue and harmonic response analyses. Similar fundamental periods and mode shapes were found from these two approaches. The fundamental modes of tank models with aspect ratios (H/D) larger than 0.63 were very similar to the first mode of a cantilever beam. For the shortest tank (H/D = 0.40), the fundamental mode was a bending mode with a circumferential wave n = 1 and an axial half-wave (m) characterized by a bulge formed near the mid-height of the cylinder.
Journal of Earthquake Engineering, 2008
Ground-supported steel tanks experienced extensive damage in past earthquakes. The failure of tan... more Ground-supported steel tanks experienced extensive damage in past earthquakes. The failure of tanks in earthquakes may cause severe environmental damage and economic losses. This study deals with the evaluation of the elastic buckling of above-ground steel tanks anchored to the foundation due to seismic shaking. The proposed nonlinear static procedure is based on the capacity spectrum method (CSM) utilized for the seismic evaluation of buildings. Different from the standard CSM, the results are not the base shear and the maximum displacement of a characteristic point of the structure but the minimum value of the horizontal peak ground acceleration (PGA) that produces buckling in the tank shell. Three detailed finite element models of tank-liquid systems with height to diameter ratios H/D of 0.40, 0.63, and 0.95 are used to verify the methodology. The 1997 UBC design spectrum and response spectra of records of the 1986 El Salvador and 1966 Parkfield earthquakes are used as seismic demand. The estimates of the PGA for the occurrence of first elastic buckling obtained with the proposed nonlinear static procedure were quite accurate compared with those calculated with more elaborate dynamic buckling studies. For all the cases considered, the proposed methodology yielded slightly smaller values of the critical PGA for the first elastic buckling compared to the dynamic buckling results.
Journal of Constructional Steel Research, 2006
We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the... more We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the foundation, subjected to horizontal components of real earthquake records. The study attempts to estimate the critical horizontal peak ground acceleration (Critical PGA), which induces elastic buckling at the top of the cylindrical shell, for the impulsive hydrodynamic response of the tank-liquid system. Finite elements models of three cone roof tanks with height to diameter ratios (H/D) of 0.40, 0.63 and 0.95 and with a liquid level of 90% of the height of the cylinder were used in this study. The tank models were subjected to accelerograms recorded during the 1986 El Salvador and 1966 Parkfield earthquakes, and dynamic buckling computations (including material and geometric non-linearity) were carried out using the finite element package ABAQUS. For the El Salvador accelerogram, the critical PGA for buckling at the top of the cylindrical shell decreased with the H/D ratio of the tank, while similar critical PGAs regardless of the H/D ratio were obtained for the tanks subjected to the Parkfield accelerogram. The elastic buckling at the top occurred as a critical state for the medium height and tallest models regardless of the accelerogram considered, because plasticity was reached for a PGA larger than the critical PGA. For the shortest model (H/D = 0.40), depending on the accelerogram considered, plasticity was reached at the shell before buckling at the top of the shell.
Journal of Sound and Vibration, 2008
The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure d... more The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks.
The damage due to buckling in thin-walled, short cylindrical aboveground tanks is discussed in th... more The damage due to buckling in thin-walled, short cylindrical aboveground tanks is discussed in this paper. Various sources of buckling are considered, including wind, earthquake, support settlement and vacuum during emptying of the tank. In all cases the tanks were modeled using finite elements, and the results include the buckling load and associated buckling mode, and the postbuckling equilibrium path. The results have been obtained using the computer packages ABAQUS and ALGOR. Experiments on flexible small-scale tanks with settlement of the supports on a sector of the foundation were conducted. Also, wind tunnel tests were carried out on rigid tanks with and without a roof to evaluate the pressure distribution due to wind.
Journal of Sound and Vibration, 2008
The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure d... more The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks. r
Engineering Structures, 2003
The influence of a fixed roof on the natural periods of vibrations of thin-walled aboveground ste... more The influence of a fixed roof on the natural periods of vibrations of thin-walled aboveground steel tanks with clamped boundary conditions at the base is studied. Tanks with open-top, self-supported roofs, and roofs supported by rafters are considered, along with different tank aspect ratios. The self-supported roof geometries considered include dome, cone, shallow cone, and flat roofs; whereas the rafters supported roofs geometries study cone, shallow cone, and flat roofs. The effect of the aspect ratio, along with the roof configuration on the natural periods is discussed. It was found that the vibration of empty tanks with a fixed roof is dictated either by cylinder modes or roof modes of vibrations. For self-supported roofs predominant roof modes resulted, whereas for tanks with roofs supported by rafters, cylinder modes dominate the dynamic behavior of the tank. Roof dominant modes had natural periods that remain constant regardless of the aspect ratio considered. Cylinder modes, on the other hand, were characterized by natural periods that showed a linear dependence with the aspect ratio of the tank.
Journal of Vibration and Control, 2005
In this paper we investigate the influence of hydrostatic pressure and self-weight loads (pre-str... more In this paper we investigate the influence of hydrostatic pressure and self-weight loads (pre-stress state) on the natural periods and mode shapes of steel cylindrical tanks and on the response under horizontal motions. The tank structure is modeled with finite elements and added mass models are used to represent the liquid. Only the impulsive component of the hydrodynamic response is considered. The natural periods and mode shapes for tank-liquid systems including and neglecting the effect of the pre-stress state are computed and compared. Three tank-liquid systems with different cylinder height to diameter ratios and slenderness ratios are considered. The numerical results show that the pre-stress state has a significant influence in the natural periods and mode shapes of tank-liquid systems with thinner walls1 however, for thicker shells this effect is reduced. When the pre-stress state is neglected and included, the smaller differences in natural periods occur, for modes characterized by small circumferential wavenumbers. The steady-state response of a tank-liquid system to horizontal harmonic base accelerations was also computed. Large differences were found when the pre-stress state was neglected. A comparison of the frequency response functions shows that the peak responses occur at quite different load periods and they have significantly different amplitudes. 1 12005 Sage Publications 1196 J. C. VIRELLA ET AL.
Engineering Structures, 2006
This paper reports results on the fundamental impulsive modes of vibration of cylindrical tank-li... more This paper reports results on the fundamental impulsive modes of vibration of cylindrical tank-liquid systems anchored to the foundation under horizontal motion. The analyses are performed using a general purpose finite element (FE) program, and the influence of the hydrostatic pressure and the self-weight on the natural periods and modes is considered. The roof and walls are represented with shell elements and the liquid is modeled using two techniques: the added mass formulation and acoustic finite elements. Tank height to diameter ratios from 0.40 to 0.95 were used, with a liquid level at 90% of the height of the cylinder. The effect of the geometry on the fundamental modes for the tank-liquid systems is studied using eigenvalue and harmonic response analyses. Similar fundamental periods and mode shapes were found from these two approaches. The fundamental modes of tank models with aspect ratios (H/D) larger than 0.63 were very similar to the first mode of a cantilever beam. For the shortest tank (H/D = 0.40), the fundamental mode was a bending mode with a circumferential wave n = 1 and an axial half-wave (m) characterized by a bulge formed near the mid-height of the cylinder.
Journal of Earthquake Engineering, 2008
Ground-supported steel tanks experienced extensive damage in past earthquakes. The failure of tan... more Ground-supported steel tanks experienced extensive damage in past earthquakes. The failure of tanks in earthquakes may cause severe environmental damage and economic losses. This study deals with the evaluation of the elastic buckling of above-ground steel tanks anchored to the foundation due to seismic shaking. The proposed nonlinear static procedure is based on the capacity spectrum method (CSM) utilized for the seismic evaluation of buildings. Different from the standard CSM, the results are not the base shear and the maximum displacement of a characteristic point of the structure but the minimum value of the horizontal peak ground acceleration (PGA) that produces buckling in the tank shell. Three detailed finite element models of tank-liquid systems with height to diameter ratios H/D of 0.40, 0.63, and 0.95 are used to verify the methodology. The 1997 UBC design spectrum and response spectra of records of the 1986 El Salvador and 1966 Parkfield earthquakes are used as seismic demand. The estimates of the PGA for the occurrence of first elastic buckling obtained with the proposed nonlinear static procedure were quite accurate compared with those calculated with more elaborate dynamic buckling studies. For all the cases considered, the proposed methodology yielded slightly smaller values of the critical PGA for the first elastic buckling compared to the dynamic buckling results.
Journal of Constructional Steel Research, 2006
We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the... more We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the foundation, subjected to horizontal components of real earthquake records. The study attempts to estimate the critical horizontal peak ground acceleration (Critical PGA), which induces elastic buckling at the top of the cylindrical shell, for the impulsive hydrodynamic response of the tank-liquid system. Finite elements models of three cone roof tanks with height to diameter ratios (H/D) of 0.40, 0.63 and 0.95 and with a liquid level of 90% of the height of the cylinder were used in this study. The tank models were subjected to accelerograms recorded during the 1986 El Salvador and 1966 Parkfield earthquakes, and dynamic buckling computations (including material and geometric non-linearity) were carried out using the finite element package ABAQUS. For the El Salvador accelerogram, the critical PGA for buckling at the top of the cylindrical shell decreased with the H/D ratio of the tank, while similar critical PGAs regardless of the H/D ratio were obtained for the tanks subjected to the Parkfield accelerogram. The elastic buckling at the top occurred as a critical state for the medium height and tallest models regardless of the accelerogram considered, because plasticity was reached for a PGA larger than the critical PGA. For the shortest model (H/D = 0.40), depending on the accelerogram considered, plasticity was reached at the shell before buckling at the top of the shell.