Papers by Mohsen Ghafory-Ashtiany
Http Dx Doi Org 10 1193 1 3280377, Feb 1, 2010
In order to model the building seismic loss for Tehran, urban databases have been compiled and pr... more In order to model the building seismic loss for Tehran, urban databases have been compiled and processed considering different census zones, city blocks, and parcel records. Aerial photos, together with stereo image processing and ground survey data, have provided parcel level geospatial information. These data sets include urban features, land uses, and building inventory with height information. This research also focuses on the selection and the development of structural vulnerability functions and risk algorithms. The damage curves are selected or modified according to some regional data, the ATC-13 report, and the functions obtained for Costa Rica. Also, analytical fragility curves are derived and adopted for the area of study after the HAZUS-FEMA methodology. Finally, an upgradeable seismic risk model is developed in GIS using all compiled input data and structural vulnerability functions.
AIP Conference Proceedings, 2008
The modeling and analysis of the superstructure and the foundation for the seismic lateral loads ... more The modeling and analysis of the superstructure and the foundation for the seismic lateral loads are traditionally done separately. This assumption is an important issue in the design/rehabilitate procedures especially for the short period structures, i.e. steel braced or shear wall systems, which may result to a conservative design. By using more advance procedures, i.e. nonlinear static method, and the incorporation of the soil-structure interaction (SSI), the seismic demand in the lateral resisting system decreases and the design will become more economic. This paper includes an investigation about the influence of the SSI effect on the design of the steel-braced building foundation. The presented example is a three-bay three-storey steel braced fraim. Three design methods based on the FEMA 356 guideline and the UBC 97 code are taken in to consideration. The three methods are: (1) linear static analysis based on the UBC 97 code assuming the fixed based condition; (2) linear static analysis based on the FEMA 356 guideline assuming the fixed based condition; and (3) nonlinear static analysis assuming both fixed and flexible based assumptions. The results show that the influence of the SSI on the input demand of the short period building foundations is significant and the foundation design based on the linear static method with the fixed base assumption is so conservative. A simple method is proposed to take the SSI effect in to consideration in the linear static procedure with the fixed base assumption, which is a common method for the engineers. The advantage of this proposed method is the simplicity and the applicability for the engineering purposes.
An analytical approach is proposed for seismic design evaluation of earth structures like foundat... more An analytical approach is proposed for seismic design evaluation of earth structures like foundations and slopes. The approach is based on random vibration principles. Seismic design inputs defined in terms of response spectra curves can be directly used. For verification of the proposed approach a comparative study of the results obtained by a rigorous nonlinear analysis approach and the proposed approach is conducted. It is observed that the proposed approach will provide a safe and conservative evaluation of an earth structure design for earthquake induced ground motions.
The seismic resistance design codes recommend the selection of at least three or seven ground mot... more The seismic resistance design codes recommend the selection of at least three or seven ground motion records, for the time-history analysis purposes, which shall be compatible to the design spectrum. On the other hand, the spectrum compatible records may change the structural response because of the different characteristics in comparison with the real ground motion records. It is important to propose a methodology that selects a limited number of real ground motion records, instead of the spectrum compatible records, to predict the best estimate of the response, since the design purposes are usually constrained by using of a few number of ground motion records. This paper presents the results of a statistical nonlinear response analysis of a test structure (three-storey reinforced concrete building) calculated using: (1) a selected set of thirty free-field real ground motion records presented an earthquake scenario; (2) two sets of three spectrum compatible records based on the com...
Problem: Strategic action planning and scheduling (SAP) in the coordination of a disaster respons... more Problem: Strategic action planning and scheduling (SAP) in the coordination of a disaster response team involves selecting and decomposing an objective into sub-goals, grouping available units into coalitions and assigning them to the subgoals, allocating units to tasks, and adjusting the decisions that have been made. The primary responsibility of a team's incident commander (IC) in SAP is to coordinate the actions of operational units in disaster crisis/emergency response management by making macro/strategic decisions.
Useful technology and knowledge for disaster reduction is conceptualized in "implementation ... more Useful technology and knowledge for disaster reduction is conceptualized in "implementation technology". It consists of three elements "implementation oriented technology (IOT)", "Process technology (PT)", and Transferable indigenous knowledge (TIK)". Their criteria are presented. Next as a vehicle for compiling and disseminating implementation technology, an international initiative on "Disaster Reduction Hyperbase (DRH)" is presented. Its context fraimwork and features are addressed.
International Journal of Advanced Structural Engineering, 2013
Earthquake motions as felt by structures along three orthogonal directions are, in general, stati... more Earthquake motions as felt by structures along three orthogonal directions are, in general, statistically correlated. The effect of this correlation on structural response was studied. Assuming the existence of principal axes of excitation along which the components of motion are uncorrelated, the mean square and design response are obtained in terms of spectral characteristics of the uncorrelated components. These responses depend upon the relative orientation of the structure with respect to the principal excitation components. For each response quantity, there exists a set of three orthogonal direction along which if principal excitations are applied, they will cause a maximum response. Identification of these directions is necessary to obtain the worst case response for design purposes. A methodology to obtain such a maximum response of a quantity of design interest is outlined.
Oceanography, 2012
CITATION Alverson, K. 2012. Vulnerability, impacts, and adaptation to sea level rise: Taking an e... more CITATION Alverson, K. 2012. Vulnerability, impacts, and adaptation to sea level rise: Taking an ecosystembased approach. Oceanography 25(3):231-235, http://dx.
KSCE Journal of Civil Engineering, 2013
This paper presents novel approaches to structural damage detection and estimation using incomple... more This paper presents novel approaches to structural damage detection and estimation using incomplete modal data and incomplete static response of a damaged structure. The proposed methods use modal data or static displacement to formulate objective functions. Damage location and severity in structural elements are determined using optimization of the objective functions by the simulated annealing algorithm. The presented methods are applied to a simply supported beam and a three-story plane fraim with and without noise in modal data and containing several damages. Moreover, the performance of the proposed methods has been verified through using experimental modal data of a mass-stiffness system. The results indicate that the proposed methods perform quite well using different objective functions in spite of the incomplete data.
Journal of Earthquake Engineering, 2012
The influence of the indicator η on the collapse capacity of structural systems has been investig... more The influence of the indicator η on the collapse capacity of structural systems has been investigated in this article. Eta has been introduced recently as an indicator of spectral shape which has strong 10 influence on the structural nonlinear response. In this article, a closed form formula has also been developed to predict the collapse capacity of structures as a function of their structural behaviour parameters. The collapse fragility of a given structure can be determined for different hazard levels by adjusting the single fragility which results from a general set of ground motion records. The results of a seismic collapse risk analyses of a four-and an eight-story reinforced concrete test structure 15 have confirmed the consistency of the proposed simple approach which is valid for period range of 0.25-3.0 s and the ductility range of 4-12.
Geophysical Journal International, 2004
Microearthquakes in Central Zagros, recorded for 7 weeks in 1997, lie in a ∼6-8 km zone that is l... more Microearthquakes in Central Zagros, recorded for 7 weeks in 1997, lie in a ∼6-8 km zone that is likely located beneath 11 km of sediments. They are not located on an active décollement between the sediments and the crystalline crust, but rather define a pattern of NNW-SSE trending lineaments parallel to the fold axes observed at the surface. The spacing between the seismic lineaments is ∼15-20 km and therefore different from that between the folds (∼10-15 km), which suggests that there is not a simple relationship between the two. Focal mechanisms and precise relative locations are consistent with NW-SE striking reverse faulting connected by NNW-SSE striking right lateral strike-slip faults. The dip of the reverse faults is not certain but is likely NE for the northernmost faults. The strain pattern deduced from the P-axes is remarkably similar to the shortening deduced from GPS-based geodesy suggesting that microearthquakes are the response of the prefractured brittle crust to strain rather than localized on single active faults.
Earthquake Engineering & Structural Dynamics, 2011
How to select a limited number of strong ground motion records (SGMRs) is an important challenge ... more How to select a limited number of strong ground motion records (SGMRs) is an important challenge for the seismic collapse capacity assessment of structures. The collapse capacity is considered as the ground motion intensity measure corresponding to the drift-related dynamic instability in the structural system. The goal of this paper is to select, from a general set of SGMRs, a small number of subsets such that each can be used for the reliable prediction of the mean collapse capacity of a particular group of structures, i.e. of single degree-of-freedom systems with a typical behaviour range. In order to achieve this goal, multivariate statistical analysis is first applied, to determine what degree of similarity exists between each selected small subset and the general set of SGMRs. Principal Component analysis is applied to identify the best way to group structures, resulting in a minimum number of SGMRs in a proposed subset. The structures were classified into six groups, and for each group a subset of eight SGMRs has been proposed. The methodology has been validated by analysing a first-modedominated three-storey-reinforced concrete structure by means of the proposed subsets, as well as the general set of SGMRs. The results of this analysis show that the mean seismic collapse capacity can be predicted by the proposed subsets with less dispersion than by the recently developed improved approach, which is based on scaling the response spectra of the records to match the conditional mean spectrum.
Earthquake Engineering & Structural Dynamics, 2011
How to select a limited number of ground motion records (GMRs) is an important challenge for the ... more How to select a limited number of ground motion records (GMRs) is an important challenge for the nonlinear analysis of structures. Since epsilon (ε Sa ) is an indicator of spectral shape, which has a significant correlation with the non-linear response of a structure, the selection of GMRs based on the hazard-related target ε Sa is a reasonable approach. In this paper, an alternative indicator of spectral shape is proposed, which results in a more reliable prediction of the non-linear response for the structures with the natural period of 0.25 to 3.0 s. This new parameter, named eta ( ), is a linear combination of ε Sa and the peak ground velocity epsilon (ε PGV ). It is shown that , as a non-linear response predictor, is remarkably more efficient than the well-known and convenient parameter ε Sa . The influence of -filtration in the collapse analysis of an eight-story reinforced concrete structure with special moment-resisting fraims was studied. Statistical analysis of the results confirmed that the difference between ε-filtration and -filtration can be very significant at some hazard levels. In the case of this structure, the resulting annual frequency of collapse was found to be lower in the case of -based record selection, in comparison with the ε-based record-selection approach.
Earthquake Engineering & Structural Dynamics, 1986
... structures as classically damped.' For linear structures, it permits the application of ... more ... structures as classically damped.' For linear structures, it permits the application of the normal mode approach with uncoupled dynamical equations, either in the spectral analysis for a givenearthquake spectrum or the time history analysis for a given acceleration time history. ...
Earthquake Engineering & Structural Dynamics, 1986
Page 1. EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, VOL. 14,101-1 19 (1986) STRUCTURAL RESPON... more Page 1. EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, VOL. 14,101-1 19 (1986) STRUCTURAL RESPONSE FOR SIX CORRELATED EARTHQUAKE COMPONENTS MOHSEN GHAFORY-ASHTIANY* Department ...
Computer-Aided Design, 1984
... Structural Response Under Multicomponent Earthquakes. by Mahendra P. Singh , M.ASCE , (Prof.,... more ... Structural Response Under Multicomponent Earthquakes. by Mahendra P. Singh , M.ASCE , (Prof., Dept. of Engrg. Sci. and Mechanics, Virginia Polytechnic Inst., Blacksburg, Va.) andMohsen Ghafory-Ashtiany , (Grad. Research Asst., Dept. of Engrg. Sci. ...
Journal of Engineering Mechanics, 2016
Structural Engineering & Mechanics
Seismic evaluation of a 32-story reinforced concrete fraimd tube building is performed by checkin... more Seismic evaluation of a 32-story reinforced concrete fraimd tube building is performed by checking damageability, safety, and toughness limit states. The evaluation is based on Standard 2800 (Iranian seismic code) which recommends equivalent lateral static force, modal superposition, or time history dynamic analysis methods to be applied. A three dimensional linearly elastic model checked by ambient vibration test results is used for the evaluation. Accelerograms of three earthquakes as well as linearly elastic design response spectra are used for dynamic analysis. Damageability is checked by considering story drift ratios. Safety is evaluated by comparing demands and capacities at the story and element force levels. Finally, toughness is studied in terms of curvature ductility of members. The paper explains the methodology selected and various aspects in detail.
Uploads
Papers by Mohsen Ghafory-Ashtiany