Seismic intensity measures for above‐ground liquid storage tanks          下载免费PDF全文

Konstantinos Bakalis  Mohsen Kohrangi  Dimitrios Vamvatsikos 《地震工程与结构动力学》2018,47(9):1844-1863

A series of scalar and vector intensity measures is examined to determine their suitability within the seismic risk assessment of liquid storage tanks. Using a surrogate modelling approach on a squat tank that is examined under both anchored and unanchored support conditions, incremental dynamic analysis is adopted to generate the distributions of response parameters conditioned on each of the candidate intensity measures. Efficiency and sufficiency metrics are used in order to perform the intensity measure evaluation for individual failure modes, while a comparison in terms of mean annual frequency of exceedance is performed with respect to a damage state that is mutually governed by the impulsive and convective modes of the tank. The results reveal combinations of spectral acceleration ordinates as adequate predictors, among which the average spectral acceleration is singled out as the optimal solution. The sole exception is found for the sloshing‐controlled modes of failure, where mainly the convective period spectral acceleration is deemed adequate to represent the associated response due to their underlying linear relationship. A computationally efficient method in terms of site hazard analysis is finally proposed to serve in place of the vector‐valued intensity measures, providing a good match for the unanchored tank considered and a more conservative one for the corresponding anchored system.  相似文献   

Application of 3D Numerical Model and Intelligent Systems in Discharge Coefficient Estimation of Combined Weir-Gate     

Nima Aein  Najarchi  Mohsen  Hezaveh  Seyyed Mohammad Mirhosseini  Mehdi NajafiZadeh  Mohammad  Zeighami  Ehsanollah 《Water Resources》2020,47(4):537-549

Water Resources - Combined weir-gate structure is one of the important structures which are control the water level, measure discharge and avoid sediment deposition behind the weir. In this study,...  相似文献   

On inversion of the second- and third-order gravitational tensors by Stokes’ integral formula for a regional gravity recovery     

Mohammad A. Sharifi  Mohsen Romeshkani  Robert Tenzer 《Studia Geophysica et Geodaetica》2017,61(3):453-468

A regional recovery of the Earth’s gravity field from satellite observables has become particularly important in various geoscience studies in order to better localize stochastic properties of observed data, while allowing the inversion of a large amount of data, collected with a high spatial resolution only over the area of interest. One way of doing this is to use observables, which have a more localized support. As acquired in recent studies related to a regional inversion of the Gravity field and steady-state Ocean Circulation Explorer (GOCE) data, the satellite gravity-gradient observables have a more localized support than the gravity observations. Following this principle, we compare here the performance of the second- and third-order derivatives of the gravitational potential in context of a regional gravity modeling, namely estimating the gravity anomalies. A functional relation between these two types of observables and the gravity anomalies is formulated by means of the extended Stokes’ integral formula (or more explicitly its second- and third-order derivatives) while the inverse solution is carried out by applying a least-squares technique and the ill-posed inverse problem is stabilized by applying Tikhonov’s regularization. Our results reveal that the third-order radial derivatives of the gravitational potential are the most suitable among investigated input data types for a regional gravity recovery, because these observables preserve more information on a higher-frequency part of the gravitational spectrum compared to the vertical gravitational gradients. We also demonstrate that the higher-order horizontal derivatives of the gravitational potential do not necessary improve the results. We explain this by the fact that most of the gravity signal is comprised in its radial component, while the horizontal components are considerably less sensitive to spatial variations of the gravity field.  相似文献   

Conditional spectrum‐based ground motion record selection using average spectral acceleration          下载免费PDF全文

Mohsen Kohrangi  Paolo Bazzurro  Dimitrios Vamvatsikos  Andrea Spillatura 《地震工程与结构动力学》2017,46(10):1667-1685

The use of a seismic intensity measure (IM) is paramount in decoupling seismic hazard and structural response estimation when assessing the performance of structures. For this to be valid, the IM needs to be sufficient;that is, the engineering demand parameter (EDP) response should be independent of other ground motion characteristics when conditioned on the IM. Whenever non‐trivial dependence is found, such as in the case of the IM being the first‐mode spectral acceleration, ground motion selection must be employed to generate sets of ground motion records that are consistent vis‐à‐vis the hazard conditioned on the IM. Conditional spectrum record selection is such a method for choosing records that are consistent with the site‐dependent spectral shape conditioned on the first‐mode spectral acceleration. Based on a single structural period, however the result may be suboptimal, or insufficient, for EDPs influenced by different period values, for example, peak interstory drifts or peak floor accelerations at different floors, potentially requiring different record suites for each. Recently, the log‐average spectral acceleration over a period range, AvgSA, has emerged as an improved scalar IM for building response estimation whose hazard can be evaluated using existing ground motion prediction equations. Herein, we present a recasting of conditional spectrum record selection that is based on AvgSA over a period range as the conditioning IM. This procedure ensures increased efficiency and sufficiency in simultaneously estimating multiple EDPs by means of a single IM. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Seismic analysis of dam-foundation-reservoir system including the effects of foundation mass and radiation damping     

Mohammadnezhad  Hamid  Ghaemian  Mohsen  Noorzad  Ali 《地震工程与工程振动(英文版)》2019,18(1):203-218

One of the main concerns in using commercial software for finite element analyses of dam-foundation-reservoir systems is that the simplifying assumptions of the massless foundation are unreliable. In this study, an appropriate direct finite element method is introduced for simulating the mass, radiation damping and wave propagation effect in foundations of damfoundation-reservoir systems using commercial software ABAQUS. The free-field boundary condition is used for modeling the semi-infinite foundation and radiation damping, which is not a built-in boundary condition in most of the available commercial software for finite element analysis of structures such as ANSYS or ABAQUS and thus needs to be implemented differently. The different mechanism for modeling of the foundation, earthquake input and far-field boundary condition is described. Implementation of the free-field boundary condition in finite element software is verified by comparing it with analytical results. To investigation the feasibility of the proposed method in dam-foundation-reservoir system analysis, a series of analyses is accomplished in a variety of cases and the obtained results are compared with the substructure method by using the EAGD-84 program. Finally, the massed and massless foundation results are compared and it is concluded that the massless foundation approach leads to the overestimation of the displacements and stresses within the dam body.  相似文献   

Introducing an effective coherence function to generate non-uniform ground motion on topographic site using time-domain boundary element method     

Mohsen Isari  Reza Tarinejad 《地震工程与工程振动(英文版)》2021,20(1):89-100

In this study,a comprehensive parametric analysis was performed on non-uniform excitation of V-shaped topography using the boundary element method in time domain.For this purpose,wave scattering analysis was carried out on a topography subjected to the SV-wave for different predominant frequencies and shape ratios.Based on the numerical results,new coherence and time delay functions are proposed to generate non-uniform ground motion for topographic irregularities.The efficiency and accuracy of the proposed functions for real engineering problems are indicated by comparison with observations reported in previous literature.  相似文献   

Evaluation and forecast of human impacts based on land use changes using multi-temporal satellite imagery and GIS: A case study on Zanjan,Iran     

Mohsen Ahadnejad  Yoshihisa Maruyama  Fumio Yamazaki 《Journal of the Indian Society of Remote Sensing》2009,37(4):659-669

Land use and land cover changes due to human activities in a time sequence. Detection of such changes may help decision makers and planners to understand the factors in land use and land cover change in order to take effective and useful measures. Remote sensing and GIS techniques may be used as efficient tools to detect and assess land use change.  相似文献   

Evidence of the formation of landslide-dammed lakes in the Zagros Mountains range,Iran     

Siyamack SHARAFI  Mojtaba YAMANI  Mohsen EHTESHAMI-MOINABADI 《山地科学学报》2019,(10)

Alternation of high and low resistance sedimentary beds,active tectonics,large rivers,and slope erosion in valleys consequently resulted in landslide in dammed lakes within the Zagros range.This study presents the results in the analysis of geological and topographic data,satellite imageries,morphotectonics and hydrodynamics of drainage networks about the landslide dammed lakes.There are four landslides in central Zagros(Zagros FoldThrust Belt,ZFTB)which have formed five dammed lakes named,Seymareh,Jaidar,Shur,Shimbar,and Godar.According to the results,damming landslides occurred in the active-tectonic regions on the slopes of anticlines and in valleys with undercutting effects of rivers on their slopes consisting of alternations of loose and resistant beds.The studied landslide dams in narrow valleys are formed as a result of blocking river by sliding debris slopes and rock slides.This study also indicates the formation of Jaidar and Godar in one stage and the presence of Lake Terrace sequence in Seymareh,Shur and Shimbar lakes.The observed sequences of terrace formation in these lakes are caused by four Seymareh Landslides followed by the three-stage excavation of Shur andShimbar lakes.  相似文献   

Measuring and Simulating Co(II) Sorption on Waste Calcite,Zeolite and Kaolinite     

Latifi  Zahra  Jalali  Mohsen 《Natural Resources Research》2020,29(2):967-981

Sorption of cobalt (CoII) ions from aqueous solution by waste calcite, kaolinite and zeolite was investigated in a series of batch experiments. The sorption capacity of the sorbents was a function of the initial solution pH, contact time and sorbent/sorbate ratio. For these three sorbents, the kinetic and isotherm experimental data were well fitted to pseudo-second-order and Langmuir equations, respectively. The maximum sorption capacity (mg g^?1) of Co(II) was 4.67, 3.76 and 2.23 for waste calcite, zeolite and kaolinite, respectively. Desorption experiments showed that the desorption capacities were in the order of zeolite?>?kaolinite?>?waste calcite. The equilibrium and kinetic results indicated that waste calcite had the best performance for the removal of Co(II) compared to zeolite and kaolinite. To simulate and predict Co(II) sorption mechanisms, the surface complexation and cation exchange models in PHREEQC program were used. The model results suggested that the main mechanisms of Co(II) sorption on waste calcite and zeolite were surface complexation and cation exchange, respectively. In the case of kaolinite, the model predicted that both mechanisms were involved in the sorption of Co(II), but the surface complexation was the predominant mechanism.

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Matter infall in collapsing molecular cloud cores with an axial magnetic field     

Mohsen Nejad-Asghar 《Astrophysics and Space Science》2011,334(1):27-33

The magnetic fields affect collapse of molecular cloud cores. Here, we consider a collapsing core with an axial magnetic field and investigate its effect on infall of matter and formation of accretion disk. For this purpose, the equations of motion of ions and neutral infalling particles are numerically solved to obtain the streamlines of trajectories. The results show that in a non-steady state of ionization and ion–neutral coupling, which is not unexpected in the case of infall, the radius of accretion disk will be larger as a consequence of axial magnetic field.  相似文献