Sharif Digital Repository

Recorded ground accelerations at various locations of Karun III Dam during November 20, 2007, were recorded by an array of accelerometers located on the dam. In terms of amplitude and phase, these accelerations show non-uniformities in different elevations. In this paper, the effect of these non-uniform ground motions on the seismic response of the dam taking dam-reservoir-foundation interaction into account is investigated. The EACD-3D-2008 finite element program and ABAQUS Software are used for carrying out the seismic analyses. For this purpose, time histories of the earthquake accelerations are interpolated at nodal points located on the dam foundation interface. The analysis has been... 

The effect of Soil-Structure Interaction (SSI) on Park and Ang Damage Index in a Bilinear-SDOF model is investigated under seismic loading. This is done through an extensive parametric study. Two non-dimensional parameters are used as the key parameters which control the severity of SSI: (1) a non-dimensional frequency as the structure-to-soil stiffness ratio index and (2) the aspect ratio of the structure. The soil beneath the structure is considered as a homogeneous elastic half space and is modeled using the concept of Cone Models. The system is then subjected to three different earthquake ground motions as the representative motions recorded on different soil conditions. The analysis is... 

Vertical vibration of structures due to strong near-field earthquakes could culminate in catastrophic consequences. In this article, the optimum patterns of two types of wave barriers with different geometry configurations, buried in the soil domain, are obtained in order to reduce the vertical acceleration of the top of a circular foundation placed on the soil surface. In order to look into the influence of various soil deposits, six soil deposits with diverse material properties and bedrock depths are examined. The topology optimization procedure for finding the optimum position of the wave barriers has been conducted using coupled finite element-genetic algorithm methodology. First, the... 

In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance- based assessment, two typical 40-story tall buildings with different story modules equipped with... 

Using stochastic point source and finite fault modeling, the stochastic stress drop is estimated for 52 large shallow earthquakes listed in the 'Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation of Ground Motions (NGA)' database. The Pseudo Spectral Acceleration (PSA) of 541 accelerograms, recorded at National Earthquake Hazards Reduction Program (NEHRP) C-class sites from 52 earthquakes are simulated and compared with the PSA listed in the PEER NGA database. The magnitude of the analyzed earthquakes ranged from M4:4 to M7:6. The stress drop is calibrated by trial and error and based on the analysis of residuals where the residual is defined as the log of the... 

Tabriz has experienced several large destructive historical earthquakes in the past. Due to the absence of ground motion records in this area, a simulation of future events based on a regional seismicity information and ground motion model is necessary. Based on a maximum likelihood method, earthquake magnitude is estimated for a 10% probability of exceedance within 50 years (475-year return period) and its corresponding strong ground motions have been simulated using stochastic finite fault modeling. Using different stress parameters, suites of ground motions have been simulated for a return period of £75 years and their spectral accelerations have been compared with the corresponding... 

Steel silos are one of the main structures for bulk solids handling and storage in many industries and agricultural sectors. A growing body of research suggests the importance of including the vertical component of earthquake ground motion in seismic analysis and design of certain structures. In the case of steel silos, this may induce additional meridional compression to exacerbate buckling failures in such thin shells. Accordingly, this paper investigates the buckling behavior of three cylindrical steel silos (i.e., a squat, an intermediate slender and a slender silo) with stepped walls subjected to horizontal only (H) and horizontal and vertical (HV) ground accelerations to address this... 

This study proposes a response-based parameter for strong motion duration which is computed for structures and is the total time they are nonlinear during an earthquake. Correlation between structural response and duration for structures, subjected to a set of spectrum matched ground motions, is employed to examine the efficiency of the proposed method. The spectral matching procedure ensures that the influence of amplitude and frequency content of motions on structural response variability is significantly removed. Four concrete building type systems are studied and correlation coefficients of structural response with the proposed duration definition are examined. Comparison of the proposed... 

This study proposes a new approach to incorporate motion duration in incremental dynamic assessments. In the proposed methodology, at each intensity level, a simulation-based approach which is verified with actual data is employed to determine the median duration and the median acceleration spectra of ground motions expected to occur at the site. Afterward, at each intensity level, artificial or spectrally matched motions are produced based on the median acceleration spectra and the median duration, indicating that different intensity levels are directly covered by the generated artificial or adjusted motions rather than just scaling up and down a set of recorded ground motions. In the... 

Endurance time method is a dynamic analysis in which structures are subjected to increasing excitations. These excitations are generated to be compatible with ground motions. Conventional excitation generating processes take into consideration the dynamic characteristics related to intensity and frequency contents of ground motions; however, duration-related characteristics have never been considered directly. In this study, the existing methodology is extended to include Cumulative Absolute Velocity as a duration-related parameter in the generating process. These newly generated excitations are then employed to estimate nonlinear responses of three concrete structures as case studies.... 

In seismic resistant design of moment frames, the structure behavior under earthquakes has to be examined considering various damage criteria. Damage indices can be estimated by Endurance Time (ET) method with minimum computational effort. The quality of this estimation can be improved in different ways. In this paper, the graphs of a certain damage index versus natural period of the structure, called damage spectra, are produced applying intensifying ET records and scaled Ground Motions (GM). Then, the excitation duration of ET acceleration functions (target time) is modified in order to reach acceptable consistency between ET and GM damage spectra. Moreover, various damage indices of a... 

Theoretical and experimental verification of the pipe damper was investigated in Part I of the two companion papers. In this paper, the application of the pipe damper to structures is examined. In particular, single span slab-girder bridges are considered for analytical investigations. A practical detail for the installation of the pipe damper is introduced. Nonlinear dynamic time history analyses are conducted on bridges equipped with the pipe damper and the results are compared with ordinary bridges. Bridge span, ground motion and the pipe length are varied in the analyses. Results show that the pipe damper is a reliable and economical metallic-yielding device that can easily be installed... 

The end diaphragm of bridges are normally designed to resist lateral seismic forces imposed on the superstructure in earthquake prone regions. Using ductile diaphragms with high deformation capacity could reduce the seismic demands on the substructure and prevent costly damage under strong ground motions. The end diaphragms of steel tub girder bridges with high lateral stiffness and dominant shear behavior have a potential to be used as ductile fuse elements. In this study, a steel plate shear diaphragm (SPSD) is introduced as an external end diaphragm of tub girder steel bridges to reduce the seismic demands imposed on the substructure. Quasi static nonlinear analyses were conducted to... 

A new method for seismic analysis of containers in three-dimensional space is introduced in which the effects of both impulsive and convective components and their corresponding damping are accounted for in time domain. A case study is performed to investigate the behaviour of a concrete rectangular container under the effects of horizontal and vertical ground motions using the scaled earthquake components of the 1940 El-Centro earthquake record. Two-dimensional behaviour of the tank is assumed. The results of the study are compared with those obtained using the current practice and those determined from finite element (FE) analysis based on a lumped mass model. The results of the FE... 

This paper studies the effect of soil–structure interaction (SSI) on the seismic risk estimates of buildings. Risk, in this context, denotes the probability distribution of seismic monetary loss due to structural and nonstructural damage. The risk analysis here uncovers the probability that SSI is beneficial, detrimental, or uninfluential on seismic losses. The analyses are conducted for a wide range of buildings with different structural systems, numbers of stories, and foundation sizes on various soil types. A probabilistic approach is employed to account for prevailing sources of uncertainty, i.e., those in ground motion and in the properties of the soil–structure system. In this... 

In this paper, the effects of rocking and fixed base prestressed columns and conventional reinforced concrete columns on the response of frames are investigated. Also, the influence of some selected rocking base prestressed columns on the response of the concrete frame was studied. Three types of a concrete frame with conventional Reinforced Concrete columns, rocking, and fixed base prestressed columns were modeled using the finite element method in Opensees software. The details of the simulation of the rocking and fixed base columns in Opensees are described precisely. The results obtained from the models were compared with those of the literature to evaluate the validity of the results.... 

In this paper, a comprehensive accelerogram database of the Iranian plateau containing 3585 data with all three components is gathered. The raw data are processed by the wavelet-based denoising method, and results are compared with the contaminated data. All the data are classified into mainshock and aftershock categories using the time and spatial window method. Afterward, the data are categorized into the pulse-like and non-pulse-like events based on the detection of velocity pulse in any of horizontal and/or vertical directions. Eventually, among 3585 data, the ones with an average shear wave velocity of top 30 m of subsurface soil profile are selected and their important ground motion... 

This work proposes comprehensive empirical predictive equations for generating stochastic synthetic 3-dimensional accelerograms for the Iranian plateau based on the existing database. First, the databank of Iranian accelerograms is collected, sorted, processed, declustered and categorized into the pulse-like and non-pulse-like data. To simulate the artificial accelerograms, a stochastic model capable of handling both the temporal and spectral non-stationarity of accelerograms is adopted. By implementing nonlinear curve fitting, parameters of the stochastic model are estimated. Then, the recorded events are categorized into eight distinct groups based on the existence of pulse-like... 

This paper presents a simplified Multi-Degree-Of-Freedom (MDOF) model through modification of fish-bone model (or generic frame). Modified Fish-Bone (MFB) model is developed through three enhancements: (i) the moment of inertia for half-beams is reduced slightly to modify the assumption of equal rotation at each story joints, (ii) a number of truss elements are inserted to the fish-bone model to simulate flexural deformation of moment frames due to axial elongation and contraction of columns, and (iii) moment-rotation relationship of representative rotational springs is supposed to be bilinear instead of trilinear in order to consider simultaneous yielding at both ends of the beam in moment... 

This article presents an investigation of multi-mode effect of tall buildings subjected to near-field pulse-like ground motions. Multi-story buildings are modeled as an equivalent continuum structure consisting of a combination of a flexural cantilever beam and a shear cantilever beam. The simplified model is subjected to near-field ground motions and the representative simplified pulses. The maximum interstory drift spectra and its location along the height are calculated on the basis of modal summation approach. So, the method is largely based upon the assumption of linearity of the system. The effects of shear to flexural deformation ratio, structural to input pulse period ratio, and the...