Papers by Gholamreza Abdollahzadeh
Asian Journal of Civil Engineering
The structural response modification factor (R) is a parameter, which determines the performance ... more The structural response modification factor (R) is a parameter, which determines the performance of a structure in a nonlinear range during strong earthquakes. Hence, in the previous research, the effect of viscose dampers on the coefficient of structural modification has been measured. In this research, the effect of friction dampers on the R factor in steel structures with regard to traditional and advanced methods of nonlinear static analysis has been investigated. With the development of the application of pushover analysis, in recent years, several advanced pushover methods have been proposed to consider the realistic behaviors of structures, including the effect of higher modes or the effect of changes in the structural modal characteristics during the analysis owing to the yielding of members. Therefore, the adaptive pushover analysis was used to consider the impact of near-and far-field records. In general, the factors affecting the R factor are distinguishable from the following two perspectives: strength and ductility. Structural analysis has been carried out by the finite element method and by taking into account the nonlinear method of the members in an extended fiber section method, with and without frictional damper in different places and positions. The results show that in particular the R factor has increased 52.45% on average, under different conditions. Therefore, using the results of numerous cases and the application of dampers with different slip loads and the variable number of dampers in each story, a new equation (R d) is proposed for the R factor of structures along with a friction damper (slip force, number of story, and bay of equipped with damper).
Periodica Polytechnica Civil Engineering
Prediction of target displacement in structural systems plays a significant role in performance-b... more Prediction of target displacement in structural systems plays a significant role in performance-based design and rehabilitation of structures. In this study, the γ factor for different hardening ratios, including 1, 2, 3, 5, 7.5, 10, and 15 percentages, stiffness-strength-deterioration models, and soil type classes is determined to modify the energy balance equation in performance-based plastic design (PBPD). Statistical results indicate that the effect of the hardening ratio, deterioration, and soil type class on the capacity curve is considerable. Therefore, a simple equation based on the period of the vibration and ductility is suggested to estimate the γ factor in different structural systems. Moreover, four 1-, 3-, 7-, and 12-story moment steel structures with various hardening ratios in the material are designed to validate the proposed method. The suggested values for the γ factor show exact results compared to collected displacements from time history analysis, while the err...
Structures Congress 2018, 2018
Past earthquake episodes of moderate-to-high magnitude have shown that strong mainshock trigger u... more Past earthquake episodes of moderate-to-high magnitude have shown that strong mainshock trigger usually strong aftershocks forming, in such a way, the so-called mainshock-aftershock (MSAS) sequences. The latter can normally induce higher seismic losses to structures and infrastructures compared to the single mainshock event. High vulnerability has been also detected for structural systems being subjected to the soft soil earthquake strong ground motions due to the soft soils-driven amplification in structural demand. Along these lines, this study investigates the seismic fragility of an existing reinforced concrete (rc) structure subjected to MSAS sequences recorded on soft soil profiles. To this end, a preliminary selection of 28 and 52 soft-soil mainshocks and aftershocks strong GMs respectively served the basis to generate 36 artificial earthquake sequences. The latter were made of six mainshocks and six aftershocks seismic motions that are representative of the initially formed sets of records in terms of the predominant period, T g , and the strong ground motion duration. An existing seven-story rc building located in Van Nuys, California, was modelled by using the OpenSees finite element code. The measured response of the building during the Northridge (1994) earthquake episode was used to validate the finite element model developed herein. Nonlinear time history analysis was performed and the soft-soil MSAS-induced structural response (i.e., roof drift, maximum interstory drift ratio and maximum residual interstory drift ratio) was comparatively assessed with the response induced by MSAS sequences recorded on firm soil conditions. Fragility analysis was also conducted and the relevant fragility curves were estimated accounting for varying intensity of the aftershocks. Based on the results derived herein, the firm-soil MSAS led to higher structural collapse capacity compared to the one that was calculated by using the soft-soil MSAS, the latter being more profound when the building was subjected to aftershocks with increased intensity.
Nowadays, Engineers have built some tremendous structures all around the world, as a result, engi... more Nowadays, Engineers have built some tremendous structures all around the world, as a result, engineers have confronted with several unknown aspects of design and construction methods. Progressive collapse in structures has always been a serious threat, and historically has caused several vast demolitions of man-made structures and lead to damages and loss of lives. One of the causes of these damages is the failure in a number of elements during ultimate events such as earthquake or severe wind. In these types of failures, earthquake or wind act as primary perturbation factors which propagate the local failure within the structure. Although the structure is designed to resist against the specific earthquake, research reveals that failure of only two elements is capable to cause consequent damages. For this purpose, three earthquake accelerations will be exerted on the structure and simulation of two critical cables failure will be performed simultaneously. The results show that the m...
Civil engineering infrastructures journal, 2017
Steel Plate Shear Wall (SPSW) is an emerging seismic load-resistant system that, compared to othe... more Steel Plate Shear Wall (SPSW) is an emerging seismic load-resistant system that, compared to other systems, enjoys the advantages of stable ductile behavior, fewer detailing requirements, rapid constructability, and economy. American seismic provisions decree that a SPSW should be designed as a moment frame with a web infill plate. Specifically, in case of buildings taller than 160 ft, it decrees that a dual system must be used. This paper presents a method of Performance-Based Plastic Design (PBPD) to design steel moment frame-SPSW as a dual lateral load-resisting system. PBPD method uses pre-selected target drift and yield mechanism as its main criteria. For a specified hazard level, the design base shear is calculated based on energy work balance method, employing pre-selected target drift. Plastic design of dual frame system has been performed to meet the pre-selected yield mechanism. As presented in the paper, design procedure involves solving a system of five equations with fi...
Civil engineering infrastructures journal, 2019
This paper evaluates the effect of slot existence with limited length between flanges and web jun... more This paper evaluates the effect of slot existence with limited length between flanges and web junction of I-shaped beams at the region of moment connections on vertical force and shear stress distribution in beam flanges and web at connection section in comparison with classical theory of stress distribution. The main purpose of this research is to evaluate the efficiency of the slot in connections such as slotted web beam to column connection in modern age. The issue of the slot has many benefits but very little studies have been done on it. Accordingly, one hundred and twenty models with two moment connections under the concentrated static load in mid span have been made for doing parametric study in ANSYS Workbench finite element software. The linear static analysis was done on all constructed models. Variable parameters in these models for parametric study include slot length between flange and web junction in connection region (from 0 to 190 mm), beam length, beam section heigh...
Civil engineering infrastructures journal, 2013
The present research is concerned with the determination of ductility, over- strength and respons... more The present research is concerned with the determination of ductility, over- strength and response modification factors of coupled steel shear wall frames. Three structural models with various numbers of stories, bay width and coupling beam height were analyzed using static pushover and incremental nonlinear dynamic analyses. The ductility, over-strength and response modification factors for the three models are determined. Tentative values of 11.1, 11.6 and 10.6 are suggested for the response modification factor of coupled steel shear wall frames with deep and medium depth coupling beams, and uncoupled steel shear wall frames, respectively in the allowable stress design method.
Global Journal of Research In Engineering, 2016
Connections in steel structures have an important impact on the behavior of the entire structure.... more Connections in steel structures have an important impact on the behavior of the entire structure. One of them existed in the connection of column to base plate. The appropriate understanding of structural connections behavior and the awareness of how transmission of power occurred by their connections and more accurate understanding of their behavior is essential for modeling and structural analysis. In the following study, at first, the connection of the column to base palte was studied under the monotonic loading in laboratory. Then, the finite element method and criteria are used for designing the moment-rotation curve. The results of the study indicated that the moment-rotation curve of in experimental sample and the analytical methods are reasonably close to each other. Therefore, the finite element methods and criteria can be used with reasonable accuracy in the behavior evaluation of this
Integrity and stability of important structures is threatened by terrorist attacks all-over the w... more Integrity and stability of important structures is threatened by terrorist attacks all-over the world. Hence, analysis and design of such structures against blast and impact loads attracts more attention by researchers nowadays. Beam-to-column connections play important role in load-carrying chain in the structure, so that well-designed ones can retain stability of the structure after failure of some structural elements and, hence, prevent overall collapse of the structure. Present research focuses on against-blast behavior of extended end plate beam-tocolumn steel connections. In this way, various configurations of these connections are analyzed by nonlinear dynamic analysis in the finite element software, ABAQUS/Explicit taking into account strain-rate effects. The result of this research indicates that against-blast performance of steel structures with extended end plates is directly influenced by web thickness of beams and columns in the joint zone, and locating stiffeners has i...
Civil engineering infrastructures journal, 2016
Nowadays, as a result of increased terrorist and bomb attacks throughout the globe in the vicinit... more Nowadays, as a result of increased terrorist and bomb attacks throughout the globe in the vicinity of strategic buildings, designing these structures against impact loads, particularly the blast-related ones, has been taken into more consideration. The current procedure for designing the structure against an explosion is a design against the local failure of the current elements in the first step and then, in the next step, against local damage as well as tactful thinking to prevent this damage from spreading to other parts of the structure. The present research investigates the impacts of explosives, derived from probable terror–stricken scenarios inside and outside a strategic four-story steel building with a special moment frame system. Then, the resistive capacity of the damaged building (due to blast) has been evaluated against the progressive collapse, and finally, the rate of the collapse risk and the reliability of the structure have been obtained by presenting a probable me...
Civil engineering infrastructures journal, 2021
Over the previous years, the use of structure roof systems which can be implemented with long col... more Over the previous years, the use of structure roof systems which can be implemented with long column spans has been welcomed by manufacturers. One of the most widely used roofs is the waffle slab system. Therefore, by reviewing previous studies in the field of roof collapse in reinforced concrete structures under blast, the absence of studies on the performance of waffle slab and comparing its behavior with blast affected RC slabs is observed. Laboratory simulation of this problem requires high cost, high accuracy in model building and much time. In this study, after preliminary model validation with experimental research and two numerical studies in LS-DYNA software, the behavior of waffle slab subjected to blast load and compare its performance with RC slab is investigated. It should be noted that because the blast load is applied to the structure in a very short time, it has a high loading rate. Therefore, the strain rate effects on concrete and reinforcement are considered for a...
Developing the structural analysis considering fuzzy performance levels
Applied Soft Computing, 2021
Structural Engineering and Mechanics, 2021
Seismic isolation is one of the best-advanced methods for controlling seismic vibrations in build... more Seismic isolation is one of the best-advanced methods for controlling seismic vibrations in buildings, bridges and nuclear facilities. A new Friction Multi-Layer Elastomeric Seismic Isolator (FMESI) has been modeled, analyzed and investigated by ABAQUS finite element analysis software and then, compared to real models. A number of friction cores have been used instead of the lead core therefore, some of the previous isolator problems have been almost resolved. Moreover, Studies show that the proposed isolator provides suitable initial stiffness and acceptable hysteresis behavior under different vertical and horizontal loading conditions and also internal stresses in different layers are acceptable. Also, as a result, the initial stiffness and overall area of the curves increase, as friction coefficients of the cores increase, although the frictional coefficients must be within a certain range.
Analytical and Experimental Investigation of I Beam-to-CFT Column Connections under Monotonic Loading (RESEARCH NOTE)
International Journal of Engineering, Transactions B: Applications, 2013
In this study, the behavior characteristics of I beam-to-concrete filled tube (CFT) column connec... more In this study, the behavior characteristics of I beam-to-concrete filled tube (CFT) column connection is studied through experiment and finite element models under the monotonic loading. To validate the finite element modeling, at first, an experimental model is made and experimented. After validation of the finite element modeling, different models were created in the software. The studied parameters include the endplate thickness and the connection type. Various types of endplate thickness are studied for bolted and weld connections. For bolted connections, different types of I beam-to-CFT column connections are studied by using the bolts passing and not passing through the CFT section. The Results show that increase in endplate thickness leads to increase in the connection flexural strength and stiffness and decrease in rotation in a specific resistance value.
Civil engineering infrastructures journal, 2020
Two fire accidents took place in the Plasco Tower in Iran and Grenfell Tower of London in 2017. A... more Two fire accidents took place in the Plasco Tower in Iran and Grenfell Tower of London in 2017. Although both of them have led to human tragedies, post-earthquake fire can cause more irreparable damages and catastrophes in larger extents. Engineering structures are subjected to different loads during their lifetime, which may cause damage or secondary loading effects. Evaluation of durability and stability of fired structures and the effects of seismic loading are considered to be significant parameters in fire engineering. The aim of this study is to evaluate and compare durability of reinforced concrete and steel frames during fire loading and post-earthquake fires. In this study, two 7-story steel and reinforced concrete frames are exposed to the fire load. At first, steel and concrete sections are put under various thermal loads in order to compare the method of their heat transfer. Then, the effects of crack on heat transfer of concrete sections are studied. Afterwards, the sel...
افزایش خسارتهای وارده به سازهها در اثر وقوع پسلرزه در گزارشات فنی متعددی به چشم میخورد. به وی... more افزایش خسارتهای وارده به سازهها در اثر وقوع پسلرزه در گزارشات فنی متعددی به چشم میخورد. به ویژه در مورد سازههایی که در زلزله اصلی دچار آسیب شده و وارد حوزه غیرخطی شده باشند. این افزایش در خسارات عموما نتیجه افزایش تغییرمکان جانبی سازه میباشد. لذا اهمیت تخمین دقیق تغییرمکان جانبی سازه در حین ارزیابی لرزهای آن دو چندان میشود. تغییرمکان جانبی هدف در روش تحلیل استاتیکی غیرخطی به کمک روابطی در آییننامههای طراحی عملکردی محاسبه میشود، در حالی که تاثیر رخ دادن پس-لرزه در آنها لحاظ نمیگردد. در این مطالعه نقش وقوع پسلرزه بر ضریب تغییرمکان غیرخطی به عنوان تاثیرگذارترین ضریب در رابطه تعیین تغییرمکان هدف، بررسی شد. نتایج نشان داد که این ضریب، افزایش قابل توجهی در اثر وقوع پسلرزه از خود نشان میدهد. پراکندگی نتایج به دست آمده منجر به بررسی سطوح خطر زلزلههای ورودی و متعاقبا استفاده از روش مقیاس نمودن شتابنگاشتها گردید. به این منظور با مطالعه آماری روی نسبت شتاب ماکزیمم زلزله اصلی و پسلرزه متناظر با آن، طیف هدف پسلرزه تولید شد تا به این وسیله، پسلرزهها به یک طیف شتاب هدف مستقل...
SN Applied Sciences, 2020
The current study presents numerical and experimental approaches in the assessment of fracture be... more The current study presents numerical and experimental approaches in the assessment of fracture behavior of self-consolidating concrete beams strengthened with carbon fiber-reinforced polymer (CFRP) lamina. The failure modes, mid-span displacement, and the load-bearing capacity of specimens with initial notches at mid-span are analyzed by varying the notch length and the beam height. Furthermore, the effects of variations in CFRP and concrete mechanical properties, bond strength, and notch location are examined by using the non-linear finite element analysis. Findings reveal that stress concentration in concrete and CFRP, in the vicinity of initial notch, as well as the failure of specimens occur as a result of CFRP debonding and crack extension. Moreover, it is observed that load-mid-span displacement curves are characterized by two peak load points strength. At the first stage, the applied load increases up to one peak value and then at the second stage there is a drop in the load-caring capacity. The applied load is then improved to another peak value due to the relatively high cohesive effect of the CFRP sheet at the third stage. Among different variables, the second peak load shows higher sensitivity to variations of the elastic modulus of CFRP, and bond strength at interface. As the notch approaches the beam support, and hence the relative distance from mid-span changes from 0 to 2/3, the two peak loads are respectively escalated by 116 and 58%, and thus the inclined crack propagates toward mid-span.
Journal of Mathematics and Computer Science, 2014
The town bridges are among the most important structural elements that decrease the traffic probl... more The town bridges are among the most important structural elements that decrease the traffic problems. The bridge management system is one of the significant components of the transport management system. Allocating appropriate funds for repairing and maintaining the bridges for the governmental institutions is needed. Therefore, in big cities with multiple bridges and limited funds, the need to investigate the bridges for their repair, maintenance, enforcement, resistant making, and substituting the risky ones increase. In this study, for the first time, through using two methods of decision making, the FUZZY aggregate simple weight (FSAW) and the analytical network procedure (ANP), the risk ability of various bridges in Babolsar in a case wise approach was appraised and it became evident that the second bridge of this city has a high risk compared to the other bridges of the city. Also, in this paper, for the first time, the risk appraisal of the bridges in the exploitation mode was investigated. Examining the effective measures on the risk of the bridge along with the findings of prior research showed that earthquake, flood, traffic load, bridge abrasion and the life span of the bridge are the most important measures of appraising the risk of bridges in the exploitation mode. The bridges in Babolsar were investigated through using the two methods of decision making, ANP and FSAW. It was found that the first bridge of this city has the most probability of destruction and should be given more attention.
Seismic-explosion risk-based robustness index of structures
International Journal of Damage Mechanics, 2016
Nowadays public buildings, located in residential areas, are occasionally affected by unwanted an... more Nowadays public buildings, located in residential areas, are occasionally affected by unwanted and unexpected events. Structural robustness makes balance between local damages and comprehensive ones. This study suggests a new method to evaluate the risk-based robustness index in structures. Two critical events, namely earthquake and blast, are considered to evaluate the risk-based robustness index, both of which are regarded as compatible and interdependent so that an earthquake-related blast happens simultaneously or a little after the quake and as a result of gas leak or damage in mechanical and thermal facilities. Based on uncertainty parameters in both critical events, risk-based robustness index (as a result of earthquake and blast) also called "seismic-explosion risk-based robustness index”, is brought up by generating scenarios. Finally, in order to understand this method better, the article gives an example to evaluate this index on a reinforced concrete moment frame bu...
Archives of Civil Engineering, 2015
In this stud y, we attempt to analyse free nonlinear vibrations of buckling in laminated composit... more In this stud y, we attempt to analyse free nonlinear vibrations of buckling in laminated composite beams. Two new methods are applied to obtain the analytical solution of the nonlinear governing equation of the problem. The effects of different parameters on the ratio of nonlinear to linear natural frequencies of the beams are studied. These methods give us an agreement with numerical results for the whole range of the oscillation amplitude.
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Papers by Gholamreza Abdollahzadeh