hassan moghaddam | Sharif University of Technology (original) (raw)
Papers by hassan moghaddam
Research Square (Research Square), Nov 3, 2022
Journal of Structural Engineering-asce, Aug 1, 2009
Scientia Iranica, Oct 1, 2005
Structural Design of Tall and Special Buildings, Jun 1, 2008
Journal of Constructional Steel Research, Apr 1, 2006
This paper investigates the potentialities of the pushover analysis to estimate the seismic defor... more This paper investigates the potentialities of the pushover analysis to estimate the seismic deformation demands of concentrically braced steel frames. Reliability of the pushover analysis has been verified by conducting nonlinear dynamic analysis on 5, 10 and 15 story frames subjected to 15 synthetic earthquake records representing a design spectrum. It is shown that pushover analysis with predetermined lateral load pattern provides questionable estimates of inter-story drift. To overcome this inadequacy, a simplified analytical model for seismic response prediction of concentrically braced frames is proposed. In this approach, a multistory frame is reduced to an equivalent shear-building model by performing a pushover analysis. A Conventional shear-building model has been modified by introducing supplementary springs to account for flexural displacements in addition to shear displacements. It is shown that modified shear-building models have a better estimation for the nonlinear dynamic response of real framed structures compare to nonlinear static procedures.
The nonlinear force-displacement curve of RC columns are presented in the current standards for s... more The nonlinear force-displacement curve of RC columns are presented in the current standards for seismic rehabilitation of existing buildings (such as ASCE41) by two displacement-based values of “a” and “b” that correspond to the loss of lateral and axial capacities, respectively. The ASCE41 presents the values of these two parameters as a function of the volumetric ratio of transverse reinforcement. A confinement index is proposed in this paper that accounts for the yield strength and arrangement of the transverse reinforcements as well. This index was used to predict the parameters “a” of 38 tested RC columns and the parameters “b” of 13 ايرد خيرات :هلاقم تف 22 / 5 / 1398 :هلاقم تاحلاصا خيرات 22 / 1 / 1389 1 داتسا :نارمع يسدنهم هدکشناد ،فيرش يتعنص هاگشناد ، hsnmoghaddam@yahoo.com 2 ٭ و لوئسم هدنسيون :نارمع يسدنهم هدکشناد ،فيرش يتعنص هاگشناد ،سناسيل قوف يوجشناد mohammadtafty@gmail.com 3 لاسا دازآ هاگشناد ,رايداتسا دهشم دحاو ,يم
This is a repository copy of Fundamentals of optimum performance-based design for dynamic excitat... more This is a repository copy of Fundamentals of optimum performance-based design for dynamic excitations.
In this paper the goal is to study where, when and how the cracks in the steel connection plate b... more In this paper the goal is to study where, when and how the cracks in the steel connection plate between beam and column initiate and how far would the crack continue before it fails and how to detect crack initiation and prevent the same by utilizing piezoelectric sensors. In this analysis piezoelectric is placed in line of crack propagation for sensing strain and changing it to voltage. A thin plate with edge notch which is an ideal model of typical beam to column connection is assumed. The uniaxial uniform load is applied on it. With the aid of ABAQUS software, the plate is analyzed in both elastic and plastic stages. The strain-stress curve with kinematic hardening part is considered and modeled with multi-linear method. The micromechanical based model Stress Modified Critical Strain (SMCS) model are utilized for prediction of ductile crack initiation. Based on the combined effects of the triaxiality and plastic strain, the model can capture the void growth phenomenon in steel ma...
The Newmark design spectra are commonly adopted in seismic codes to calculate design spectra, whi... more The Newmark design spectra are commonly adopted in seismic codes to calculate design spectra, while these spectra generally differ from the statistically driven ones. This study aims to re-construct the Iranian design spectra by implementing a modified Newmark method on an extensive database of previous earthquakes in Iran. To this end, three sets of earthquakes recorded at three different sites are considered. The effects of parameters such as source-to-site distance, the magnitude of ground motion, and the shear wave velocity are evaluated. Subsequently, the amplification factors are obtained through a statistical approach, and the spectral bounds are calculated for three site categories and two types of earthquake magnitudes. As a result, for the first time, the coefficients of the site design spectrum of Iran are presented as a function of ground motion’s magnitude for the aforementioned site categories. The calculated coefficients can be used to modify the Newmark spectral valu...
This paper discusses about the affective parameters in determining the capacity curve of reinforc... more This paper discusses about the affective parameters in determining the capacity curve of reinforced concrete columns with flexural or flexure-shear failure modes. For this aim, results of the lateral cyclic tests on 54 RC columns with one of these failure modes are studied. An efficient confinement index is proposed that considers all of the important parameters affecting the lateral behavior and shows excellent correlation with the experimentally obtained nonlinear lateral behavior of the studied columns. The general form of the backbone curve of the displacement-controlled structural elements in ASCE 41 is defined by using two key displacements “a” and “b”. By using the proposed confinement index and based on the results of studied columns, a table is presented as an alternative to the tables presented in the ASCE4106 standard for prediction of the lateral nonlinear behavior of RC columns.
International Journal of Poultry Science, 2004
In a 2×3 factorial arrangement, the effects of dietary protein and lysine levels on performance a... more In a 2×3 factorial arrangement, the effects of dietary protein and lysine levels on performance and carcass characteristics of Ross male broiler chickens from 1 to 3 weeks and 4 to 6 weeks of age were tested. Dietary treatments consisted of three levels of L-lysine.HCl in starter and grower period (0.0, 1.5 and 3.0 g/kg) and two levels of protein (208.4, 178.4 in starter and 181.2, 161.2 g/kg in grower period) with 12.12 MJ AME/kg diet. Reducing dietary protein decreased weight gain in starter, grower and total period up to 6.0, 4.6 and 5.6% respectively (P<0.05). It also decreased feed consumption in starter period (P<0.05). Decreasing dietary protein had no significant effect on gain to feed ratio and breast meat yield, but increased abdominal fat percentage significantly (P<0.05). Increasing dietary lysine increased feed consumption in starter and weight gain, feed to gain ratio in grower and total period of the experiment (P<0.05). It also increased breast meat yield and percentage (P<0.05). N excretion reduced significantly by decreasing dietary protein (P<0.05). Dietary treatments had no significant effect on mortality.
Nowadays, RC structural systems are being used in construction industry worldwide. The observed r... more Nowadays, RC structural systems are being used in construction industry worldwide. The observed response of medium rise building, based on post-earthquake damage assessment reports, during the latest earthquakes in the USA, Chile, Mexico and Japan have indicated that buildings including shear walls and dual structural systems behave considerably better during strong shaking. The viewpoint that shear walls are inherently brittle is still held in many countries (correspondingly in the codes) as a consequence of failures in poorly detailed RC walls. In this investigation, several RC frames, with and without shear walls, are designed according to the seismic codes, and then their nonlinear duplicates are exposed to a set of severe quakes. The time history nonlinear analyses results of these prototypes are then used to probe the effect of the existence of shear walls through using performance based design method. It is concluded that in general the existence of shear walls results in a n...
Failure of RC columns under a combination of axial compressional load and seismic moments could r... more Failure of RC columns under a combination of axial compressional load and seismic moments could result in the collapse of RC frames during severe earthquakes. This paper presents a new technique for retrofitting RC columns by wrapping them with pre-stressed steel strips. Previous experimental studies have proved this technique to be effective and promising. A previously introduced stress-strain model is used to obtain moment-curvature diagrams for retrofitted columns using a nonlinear analysis. Subsequently, these diagrams were employed in nonlinear pushover analyses to study the seismic performance of retrofitted RC frames as compared with the normal frames. The results indicate that this retrofitting approach enhances the seismic performance markedly by increasing the ductility of the columns, and hence, reducing the level of damage. In particular, this retrofitting technique replaced the undesirable failure of the columns by the rather more desirable failure of beams. INTRODUCTIO...
International Journal of Solids and Structures, 2006
Journal of Structural Engineering, 2009
In the conventional seismic design methods, height wise distribution of equivalent seismic loads ... more In the conventional seismic design methods, height wise distribution of equivalent seismic loads seems to be related implicitly on the elastic vibration modes. Therefore, the employment of such a load pattern does not guarantee the optimum use of materials in the nonlinear range of behavior. Here a method based on the concept of uniform distribution of deformation is implemented in optimization of the dynamic response of structures subjected to seismic excitation. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. It is shown that the seismic performance of such a structure is better than those designed conventionally. By conducting this algorithm on shear-building models with various dynamic characteristics, the effects of fundamental period, target ductility demand, number of stories, damping ratio, post-yield behavior and seismic excitations on optimum distribution pattern are investigated. Based on the results, a more adequate load pattern is proposed for seismic design of building structures that is a function of fundamental period of the structure and the target ductility demand.
Journal of Earthquake Engineering, 2001
In this paper, the results of recent studies on inelastic seismic response of MDOF shear-building... more In this paper, the results of recent studies on inelastic seismic response of MDOF shear-building structures are presented. In the last few decades, the concept of response modification factor R has been introduced and developed to account for inelastic nonlinear behaviour of structures under earthquakes. In this paper, an attempt has been made to adjust and extend this concept through
Journal of Constructional Steel Research, 2006
This paper investigates the potentialities of the pushover analysis to estimate the seismic defor... more This paper investigates the potentialities of the pushover analysis to estimate the seismic deformation demands of concentrically braced
steel frames. Reliability of the pushover analysis has been verified by conducting nonlinear dynamic analysis on 5, 10 and 15 story frames
subjected to 15 synthetic earthquake records representing a design spectrum. It is shown that pushover analysis with predetermined lateral
load pattern provides questionable estimates of inter-story drift. To overcome this inadequacy, a simplified analytical model for seismic
response prediction of concentrically braced frames is proposed. In this approach, a multistory frame is reduced to an equivalent shearbuilding
model by performing a pushover analysis. A conventional shear-building model has been modified by introducing supplementary
springs to account for flexural displacements in addition to shear displacements. It is shown that modified shear-building models have a better
estimation of the nonlinear dynamic response of real framed structures compared to nonlinear static procedures.
© 2005 Elsevier Ltd. All rights reserved.
Computers & Structures, 2011
A practical optimization method is applied to design nonlinear truss-like structures subjected to... more A practical optimization method is applied to design nonlinear truss-like structures subjected to seismic excitation. To achieve minimum weight design, inefficient material is gradually shifted from strong parts to weak parts of a structure until a state of uniform deformation prevails. By considering different truss structures, effects of seismic excitation, target ductility and buckling of the compression members on optimum topology are investigated. It is shown that the proposed method could lead to 60% less structural weight compared to optimization methods based on elastic behaviour and equivalent static loads, and is efficient at controlling performance parameters under a design earthquake.
Research Square (Research Square), Nov 3, 2022
Journal of Structural Engineering-asce, Aug 1, 2009
Scientia Iranica, Oct 1, 2005
Structural Design of Tall and Special Buildings, Jun 1, 2008
Journal of Constructional Steel Research, Apr 1, 2006
This paper investigates the potentialities of the pushover analysis to estimate the seismic defor... more This paper investigates the potentialities of the pushover analysis to estimate the seismic deformation demands of concentrically braced steel frames. Reliability of the pushover analysis has been verified by conducting nonlinear dynamic analysis on 5, 10 and 15 story frames subjected to 15 synthetic earthquake records representing a design spectrum. It is shown that pushover analysis with predetermined lateral load pattern provides questionable estimates of inter-story drift. To overcome this inadequacy, a simplified analytical model for seismic response prediction of concentrically braced frames is proposed. In this approach, a multistory frame is reduced to an equivalent shear-building model by performing a pushover analysis. A Conventional shear-building model has been modified by introducing supplementary springs to account for flexural displacements in addition to shear displacements. It is shown that modified shear-building models have a better estimation for the nonlinear dynamic response of real framed structures compare to nonlinear static procedures.
The nonlinear force-displacement curve of RC columns are presented in the current standards for s... more The nonlinear force-displacement curve of RC columns are presented in the current standards for seismic rehabilitation of existing buildings (such as ASCE41) by two displacement-based values of “a” and “b” that correspond to the loss of lateral and axial capacities, respectively. The ASCE41 presents the values of these two parameters as a function of the volumetric ratio of transverse reinforcement. A confinement index is proposed in this paper that accounts for the yield strength and arrangement of the transverse reinforcements as well. This index was used to predict the parameters “a” of 38 tested RC columns and the parameters “b” of 13 ايرد خيرات :هلاقم تف 22 / 5 / 1398 :هلاقم تاحلاصا خيرات 22 / 1 / 1389 1 داتسا :نارمع يسدنهم هدکشناد ،فيرش يتعنص هاگشناد ، hsnmoghaddam@yahoo.com 2 ٭ و لوئسم هدنسيون :نارمع يسدنهم هدکشناد ،فيرش يتعنص هاگشناد ،سناسيل قوف يوجشناد mohammadtafty@gmail.com 3 لاسا دازآ هاگشناد ,رايداتسا دهشم دحاو ,يم
This is a repository copy of Fundamentals of optimum performance-based design for dynamic excitat... more This is a repository copy of Fundamentals of optimum performance-based design for dynamic excitations.
In this paper the goal is to study where, when and how the cracks in the steel connection plate b... more In this paper the goal is to study where, when and how the cracks in the steel connection plate between beam and column initiate and how far would the crack continue before it fails and how to detect crack initiation and prevent the same by utilizing piezoelectric sensors. In this analysis piezoelectric is placed in line of crack propagation for sensing strain and changing it to voltage. A thin plate with edge notch which is an ideal model of typical beam to column connection is assumed. The uniaxial uniform load is applied on it. With the aid of ABAQUS software, the plate is analyzed in both elastic and plastic stages. The strain-stress curve with kinematic hardening part is considered and modeled with multi-linear method. The micromechanical based model Stress Modified Critical Strain (SMCS) model are utilized for prediction of ductile crack initiation. Based on the combined effects of the triaxiality and plastic strain, the model can capture the void growth phenomenon in steel ma...
The Newmark design spectra are commonly adopted in seismic codes to calculate design spectra, whi... more The Newmark design spectra are commonly adopted in seismic codes to calculate design spectra, while these spectra generally differ from the statistically driven ones. This study aims to re-construct the Iranian design spectra by implementing a modified Newmark method on an extensive database of previous earthquakes in Iran. To this end, three sets of earthquakes recorded at three different sites are considered. The effects of parameters such as source-to-site distance, the magnitude of ground motion, and the shear wave velocity are evaluated. Subsequently, the amplification factors are obtained through a statistical approach, and the spectral bounds are calculated for three site categories and two types of earthquake magnitudes. As a result, for the first time, the coefficients of the site design spectrum of Iran are presented as a function of ground motion’s magnitude for the aforementioned site categories. The calculated coefficients can be used to modify the Newmark spectral valu...
This paper discusses about the affective parameters in determining the capacity curve of reinforc... more This paper discusses about the affective parameters in determining the capacity curve of reinforced concrete columns with flexural or flexure-shear failure modes. For this aim, results of the lateral cyclic tests on 54 RC columns with one of these failure modes are studied. An efficient confinement index is proposed that considers all of the important parameters affecting the lateral behavior and shows excellent correlation with the experimentally obtained nonlinear lateral behavior of the studied columns. The general form of the backbone curve of the displacement-controlled structural elements in ASCE 41 is defined by using two key displacements “a” and “b”. By using the proposed confinement index and based on the results of studied columns, a table is presented as an alternative to the tables presented in the ASCE4106 standard for prediction of the lateral nonlinear behavior of RC columns.
International Journal of Poultry Science, 2004
In a 2×3 factorial arrangement, the effects of dietary protein and lysine levels on performance a... more In a 2×3 factorial arrangement, the effects of dietary protein and lysine levels on performance and carcass characteristics of Ross male broiler chickens from 1 to 3 weeks and 4 to 6 weeks of age were tested. Dietary treatments consisted of three levels of L-lysine.HCl in starter and grower period (0.0, 1.5 and 3.0 g/kg) and two levels of protein (208.4, 178.4 in starter and 181.2, 161.2 g/kg in grower period) with 12.12 MJ AME/kg diet. Reducing dietary protein decreased weight gain in starter, grower and total period up to 6.0, 4.6 and 5.6% respectively (P<0.05). It also decreased feed consumption in starter period (P<0.05). Decreasing dietary protein had no significant effect on gain to feed ratio and breast meat yield, but increased abdominal fat percentage significantly (P<0.05). Increasing dietary lysine increased feed consumption in starter and weight gain, feed to gain ratio in grower and total period of the experiment (P<0.05). It also increased breast meat yield and percentage (P<0.05). N excretion reduced significantly by decreasing dietary protein (P<0.05). Dietary treatments had no significant effect on mortality.
Nowadays, RC structural systems are being used in construction industry worldwide. The observed r... more Nowadays, RC structural systems are being used in construction industry worldwide. The observed response of medium rise building, based on post-earthquake damage assessment reports, during the latest earthquakes in the USA, Chile, Mexico and Japan have indicated that buildings including shear walls and dual structural systems behave considerably better during strong shaking. The viewpoint that shear walls are inherently brittle is still held in many countries (correspondingly in the codes) as a consequence of failures in poorly detailed RC walls. In this investigation, several RC frames, with and without shear walls, are designed according to the seismic codes, and then their nonlinear duplicates are exposed to a set of severe quakes. The time history nonlinear analyses results of these prototypes are then used to probe the effect of the existence of shear walls through using performance based design method. It is concluded that in general the existence of shear walls results in a n...
Failure of RC columns under a combination of axial compressional load and seismic moments could r... more Failure of RC columns under a combination of axial compressional load and seismic moments could result in the collapse of RC frames during severe earthquakes. This paper presents a new technique for retrofitting RC columns by wrapping them with pre-stressed steel strips. Previous experimental studies have proved this technique to be effective and promising. A previously introduced stress-strain model is used to obtain moment-curvature diagrams for retrofitted columns using a nonlinear analysis. Subsequently, these diagrams were employed in nonlinear pushover analyses to study the seismic performance of retrofitted RC frames as compared with the normal frames. The results indicate that this retrofitting approach enhances the seismic performance markedly by increasing the ductility of the columns, and hence, reducing the level of damage. In particular, this retrofitting technique replaced the undesirable failure of the columns by the rather more desirable failure of beams. INTRODUCTIO...
International Journal of Solids and Structures, 2006
Journal of Structural Engineering, 2009
In the conventional seismic design methods, height wise distribution of equivalent seismic loads ... more In the conventional seismic design methods, height wise distribution of equivalent seismic loads seems to be related implicitly on the elastic vibration modes. Therefore, the employment of such a load pattern does not guarantee the optimum use of materials in the nonlinear range of behavior. Here a method based on the concept of uniform distribution of deformation is implemented in optimization of the dynamic response of structures subjected to seismic excitation. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. It is shown that the seismic performance of such a structure is better than those designed conventionally. By conducting this algorithm on shear-building models with various dynamic characteristics, the effects of fundamental period, target ductility demand, number of stories, damping ratio, post-yield behavior and seismic excitations on optimum distribution pattern are investigated. Based on the results, a more adequate load pattern is proposed for seismic design of building structures that is a function of fundamental period of the structure and the target ductility demand.
Journal of Earthquake Engineering, 2001
In this paper, the results of recent studies on inelastic seismic response of MDOF shear-building... more In this paper, the results of recent studies on inelastic seismic response of MDOF shear-building structures are presented. In the last few decades, the concept of response modification factor R has been introduced and developed to account for inelastic nonlinear behaviour of structures under earthquakes. In this paper, an attempt has been made to adjust and extend this concept through
Journal of Constructional Steel Research, 2006
This paper investigates the potentialities of the pushover analysis to estimate the seismic defor... more This paper investigates the potentialities of the pushover analysis to estimate the seismic deformation demands of concentrically braced
steel frames. Reliability of the pushover analysis has been verified by conducting nonlinear dynamic analysis on 5, 10 and 15 story frames
subjected to 15 synthetic earthquake records representing a design spectrum. It is shown that pushover analysis with predetermined lateral
load pattern provides questionable estimates of inter-story drift. To overcome this inadequacy, a simplified analytical model for seismic
response prediction of concentrically braced frames is proposed. In this approach, a multistory frame is reduced to an equivalent shearbuilding
model by performing a pushover analysis. A conventional shear-building model has been modified by introducing supplementary
springs to account for flexural displacements in addition to shear displacements. It is shown that modified shear-building models have a better
estimation of the nonlinear dynamic response of real framed structures compared to nonlinear static procedures.
© 2005 Elsevier Ltd. All rights reserved.
Computers & Structures, 2011
A practical optimization method is applied to design nonlinear truss-like structures subjected to... more A practical optimization method is applied to design nonlinear truss-like structures subjected to seismic excitation. To achieve minimum weight design, inefficient material is gradually shifted from strong parts to weak parts of a structure until a state of uniform deformation prevails. By considering different truss structures, effects of seismic excitation, target ductility and buckling of the compression members on optimum topology are investigated. It is shown that the proposed method could lead to 60% less structural weight compared to optimization methods based on elastic behaviour and equivalent static loads, and is efficient at controlling performance parameters under a design earthquake.