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  • Open Access Persian
    Authors: 
    Mohsen Gerami; Amirhosein Zarei; Mohsen Ghaderi;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    The moment beam-to-column connections include those connections that can transfer the moment between the beam and the column. Bolted unstiffened and stiffened extended end-plate moment connections are from this category. This type of connection, which was investigated after severe damage to connections in the Northridge earthquake, Due to proper behavior under cyclic loading, was introduced as one of the pre-qualified connections of the AISC code and subsequently by the Iranian Code. Since low cyclic fatigue is another cause of failure in connections under the Northridge earthquake, it is necessary to study the fatigue behavior of this type of connection under the effect of low cycle fatigue. So far little studies have been done on the effect of low cycle fatigue on various types of connections, including end plate connections. In the present study, the S-N fatigue chart (Effective stress to the number of load cycles) that was used to estimate the effect of high cycle fatigue was developed to the low fatigue region for the end plate connections. Then, with using the S-N chart, the effect of low cycle fatigue on a 12-story structure under the influence of various earthquake records was studied to investigate the effect of low-cycle fatigue on structures with end plate moment connections. The analysis of steel structures showed that in end plate moment connections at the plastic hinge position, the effect of the cumulative cyclic fatigue before the plasticization of the connection under severe earthquakes is influential. Since the effects of fatigue are cumulative, it will be significant and destructive for end plate connections of buildings that have experienced several medium and large earthquakes.

  • Open Access Persian
    Authors: 
    Ali Katebi; Fariborz Almassian; Peyman Homami;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    Choosing construction methods and how resources are allocated are important in the project control. The multi-mode resource constrained project scheduling problem (MRCPSP) is a significant subject in project management. The development of the above model for construction projects is an important issue because of uncertainty. Fuzzy logic has been used to display the uncertainty in the duration of activities and the delay between them. This paper examines this problem and schedules project with providing an intelligent algorithm combining fuzzy sets and genetic algorithms (GAs). The Fuzzy MRCPSP problem can be considered as the scheduling of a set of activities with the aim of finding an activity operation mode and the activity operation priority; so that the resource constraints (renewable resources and non-renewable resources) as well as the precedence constraints are met simultaneously and the time for completion of the project is minimal. In the first step, the above problem is modeled mathematically, and then the model is coded using GA-based algorithm in Matlab software and finally the model is solved. The results of the implementation of this algorithm on the standard instances of the PSPLIB site, in comparison with the GAMS software, indicate the successful performance of the combined GA algorithm with fuzzy sets. The approach used in this research can be easily used by project managers. This prevents human errors caused by people who are responsible for controlling the project at resource leveling phase and is a way to the optimized project scheduling.

  • Open Access Persian
    Authors: 
    ramin ehsani; Mohammad Kazem Sharbatdar; Ali Kheyroddin;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    The particular weaknesses of concrete are brittle fracture and lack of material ductility, so using steel reinforcements and discrete fibres are an attempt to overcome this weakness. Strain hardening behaviour under tensile force has made new material HPFRCC as a high performance material with high energy absorption capability and high cracking ability before failure, Therefore the structural application of this composite material in the structural members such as continuous beams to control cracks and improve ductility has come to the believed border. In this paper, the effect of using HPFRCC containing 2% steel fibres on the flexural performance of four large two-span reinforced concrete beams has experimentally been investigated. Two beams were conventional concrete with two different arrangements of stirrups in the central support area and two other beams were companion but made with full HPFRCC composites, all beams with two equal spans of 1800 mm were loaded under concentrated force applied in the middle of the span symmetrical and incrementally. The results indicated that the use of HPFRCC with 2% steel fibre in the specimens increased the ductility, energy absorption, and bearing capacity, as well as an appropriate re-distributing moment in the plastic area of reinforced concrete continuous beam with two spans.

  • Open Access Persian
    Authors: 
    Sina Malekpour; Mohammad Reza Moarefzadeh;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    Parking floors in buildings are of the most likely places for terrorist bombings. While terrorist attacks across the globe have increased remarkably in the last decades, it is important to recognize the behavior of existing structures against explosions and to find appropriate solutions to reduce the resulting damages. In this study, the failure probability of a 10-story reinforced concrete building subject to a vehicle bombing in random locations in the ground floor is evaluated. For this evaluation, reliability analysis of the building structure is conducted using a Monte Carlo simulation method and the results are obtained using a dynamic analysis of a finite element model and LS-DYNA software. The random variables considered herein are the location of the explosion, the time history of the blast loading, the gravity loads and the slab depth. In order to investigate the effect of the explosion location on the probability of failure, the building plan was first divided into three categories including the center, side and corner areas, then by randomly generating the explosion in each area, the probability of different level of damages to the building was calculated. Based on the results obtained in this study, the probability of failure in the central area of the plan is more significantly compared with those of the other areas. Finally, it is shown that by strengthening the central columns, the probability of heavy damages (damages greater than 55%) for blast loadings containing 600, 750 and 900 Kg TNT charge weights is reduced to 52%, 56% and 77%, respectively.

  • Open Access Persian
    Authors: 
    Madjid Gholhaki; Mahdi Karimi; Ghasem Pachideh;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    Steel plate shear wall (SPSW) systems have been used in recent years in highly seismic areas to resist lateral loads. In general, a steel plate shear wall system consists of a steel plate wall, boundary columns, horizental floor beams and optional vertical and horizental stiffener plates. Utilizing stiffener plates causes changing of Steel Plate Shear Wall system behaviour, especially in nonlinear domain. In this paper subpanel size effects have been investigated on such nonlinear behavior. Five cases (one without stiffener and four with stiffener) were considered. A numerical analysis, based on finite element method was performed for each case. These analyses possess a pushover monotonic analysis. Then capacity curvature of system was derived and nonlinear behavior parameters such as “Behaviour Factor” and “Ductility Factor” were calculated by prevailing relationships. Studies show that by reducing of subpanel size, nonlinear characteristics of Steel Plate Shear Wall systems improve considerably. Also some relationships proposed for assessment of nonlinear characteristics of such system. Regarding the structures with high hardness (frequencies greater than about 2 Hz), increase in the behaviour coefficient in negligible, and in general, for this frequency range, it is recommended to use a fixed amount for the behaviour factor ranged from 11 to 13.

  • Open Access Persian
    Authors: 
    reza jome manzari; Farzad Shahabian;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    Functionally Graded Materials (FGMs) are kinds of composite materials which exhibit continuous variation of material properties from one surface to another. With regard to the continuity of mixture of constituent materials, FGMs have more effective mechanical properties compared to laminated composite materials, which leads to eliminate the interlayer stress concentration. The most common usage of such materials is in thin-wall structures, such as plates and shells. Plates due to their extensive surface and low thickness, not only have low resistance against the blast loads, but also experience large displacements. Hence, utilizing FGM plates because of their constituents materials which have a power distribution in the direction of thickness, will lead to resistance improvement and displacement reduction. In this research, ABAQUS finite element software has been used to study geometric nonlinear dynamic response of Stainless steel-Silicon nitride FGM plates against the blast loads. The effect of volume fraction index, plate aspect ratio, plate thickness, the amount of explosive material and its distance and also the effect of Replica scale with Hopkinson scale are investigated in this study. The results show that with rising in the volume fraction index (from zero to infinity), increasing in the distance of explosion center to the plate (from 500mm to 900mm) and plate thickness (from 6mm to 18mm), the maximum amount of displacement of the plate have decreased by %29/1, %43/64 and %87/74 respectively. On the other hand, by expansion of the plate dimensions ratio (from 1 to 2) and increasement in the amount of explosive material (from 5 to 25gr), the maximum displacement of the plate have increased by 1/06 and 3/09 respectively. Also, it has been observed that changes in materials properties along with plate thickness don’t have any effect on scaling.

  • Open Access Persian
    Authors: 
    Mohsen Parviz; Babak Aminnejad; Alireza Fiouz; Mohammad Hadi Alizadeh Elizei;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    In this paper, parametric studies were performed on some pipes buried in soil under blast loadings. The effects of various parameters, such as the physical properties of liquid, air, soil, pipe, and T.N.T were investigated. The Arbitrary Lagrangian-Eulerian (ALE) method was used in the LS-DYNA software. In the following, a compared between liquids. The results show that, the pipe has undergone increased pressure and stress by reducing the fluid density. Also,This indicates that the higher the fluid density is, the less pressure and stress will be impose d on the pipe and vice versa. In general, the result demonstrates that a higher density of soil causes higher pressure and stress transfers on the pipe and explosion in lower soil density result in less damage to the pipe and acts as a damper under waves of explosion. In other words, higher density in the soil causes more pressure and stress transfers on the pipe and lower soil density acts as a damper under the waves of explosion. Now, knowing the soil type performance on the stress and pressure transfers in the buried pipes under explosion, it can be realized that pipes with high resistance should be used in soils with high density due to the transmission of high stress and pressure through the pipes considering the fact that buried pipelines, while in soils with lower density, pipes with lower resistance can be applied due to better soil performance like a damper and transmission of less stress and pressure through them. Therefore, with the correct selection of pipes in terms of resistance according to the regional soil type, a substantial sum can be economically saved for the implementation of oil and gas pipeline projects.

  • Open Access Persian
    Authors: 
    Madjid Gholhaki; Ghasem Pachideh;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    Fibre or recycled material used in the concrete improves resistance, ductility, and durability of concrete. Concrete has fire-resistant properties but the most worrying thing about reinforced concrete structures during the fire is related to rebars. Therefore, there is a suggestion about use of alternative materials such as recycled metal spring in order to reduce above mentioned risks. In this paper, we conduct laboratory study to assess performance of concrete containing recycled metal spring while using volumetric amounts of 0.2, 0.4 and 0.6% at temperatures of 25, 100, 250, 500, 700 and 900 degrees Celsius. Furthermore, compressive strength and tensile strength of the most optimal combination of spring in the concrete are compared with concrete containing steel fibre and polypropylene. The results show that spring used in the concrete improves compressive strength and tensile strength. But the more the spring is used in the concrete, the more the resistance is reduced. Therefore, if the spring with 0.2 volume percent that is considered as the most optimal combination percentage is increased by 3 times, it increases compressive strength and tensile strength. Furthermore, the optimal compressive strength of spring in different temperatures is about 2 – 3 times of steel fibre and polypropylene and its tensile strength is close to strength of steel fibre. Fibre used in concrete reduces width of the cracks created after the test by 3 times.

  • Open Access Persian
    Authors: 
    Mohammad Amir Najafgholipour; Seyed Mehdi Dehghan; Ali Reza Kamrava;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    Several researches have been carried out on seismic behavior and retrofitting of unreinforced masonry (URM) walls. Using an external retrofitting surface layer is the most popular strengthening technique for URM walls. Recently, using fiber reinforced concrete (FRC) overlay as a strengthening technique for URM walls is evaluated though a series of experimental studies. Therefore, in this paper finite element modeling of URM walls strengthened with FRC layer under in-plane actions is considered through a micro modeling approach in finite element software ABAQUS. Concrete Damage Plasticity Model is used for modeling of brick unites and mortar joints. In this article the finite element modeling of the retrofitted walls is explained and is verified with results of a previous experimental study. Results obtained from analyzes show that the finite element model can simulate the in-plane behavior of strengthened URM walls well. In addition, a parametric study is performed and the influence of some parameters such as FRC surface layer thickness, fiber content and retrofitted face of the panel on the in-plane capacity of the strengthened masonry panels is evaluated. Analysis results show that the FRC overlay thickness and retrofitted face of the wall has considerable effects on the in-plane strength of retrofitted URM walls.

  • Open Access Persian
    Authors: 
    Mohammad Esmaeil Nia Omran; Somayeh Mollaei;
    Publisher: Iranian Society of Structrual Engineering (ISSE)

    In most of the structural blast-resistant designs and analysis single degree of freedom (SDOF) method is used. Generally, for this method flexural response of the structural members is considered but in axial loaded members, secondary moments (P-δ effects) are also very important. In the case of columns of building structures, which mostly bear significant axial loads, ignoring P-δ effects under lateral blast loading can be very risky. This paper describes a simple way for taking into account P-δ effects and also the effects of high strain rates (which is very important in severe dynamic loading) in SDOF analysis of reinforced concrete columns under simultaneous axial load and lateral blast loading. The resulting responses are compared with explicit finite element analysis using LS-DYNA hydro-code. Proposed SDOF equation of motion is numerically calculated and secondary moment and high strain rate effects are included within the calculation procedure. Secondary moments due to P-δ effects have been considered as equivalent lateral load and strain effects are introduced to the model by dynamic increasing factors for concrete and steel materials. Based on the main results, estimated response of RC column under blast loading using SDOF method has acceptable accuracy compared to LS-DYNA analysis results.

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