• Publicationsclose
• Research softwareclose
• 2013-2022close
• Open Access close
• Article close
• Persian close
• Journal of Structural and Construction Engineering close

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.

Steel moment system and steel moment with centrically braces are two common systems. Many of regulations related to this structures explained in details to design structures against earthquake loads but they didn’t mention methods about dynamic load such as blast or car crash. However, the mentioned parameters may cause key member fracture such as column that result total or partial damage. Therefore, investigation about these structures seems necessary. This paper presents a numerical study of 20 story steel building with two different lateral systems and two column removal scenarios using Abaqus. Three dimensional modeling, using the finite element method was developed and investigated to understand the progressive collapse of 20 story buildings with composite steel frames. Numerical result verified with experimental results. The response of the building was studied in detail and results are recommended to mitigate progressive collapse in future designs. The results of this study show that corner column case removal is more critical than side case removal from view point of increasing axial force and moment. Also the results indicated that behavior of different structures systems against progressive collapse is NOT remarkable. To avoid potential progressive collapse, it suggests that the columns were designed and controlled for double of service loads.

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.

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.

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.

Previous studies on shape memory alloys often related to one of the most usable type called Ni-Ti. However, many researchers are trying to find alternative alloys because of high cost and complex behavior of this alloy due to the high dependence of strain rate. The present study has been evaluated on properties of new alloy Cu-Al-Mn that has been introduced by Japanese researcher Araki. Also, it has been assessed ability of behavioral models for numerical simulation. The alloy with a superelasticity comparable to Ni–Ti alloys has more suitable cost and low dependence of strain rate. Based on properties of this alloy, the ability of three rate-independent model has been evaluated using; Graesser-Cozzarelli, Fugazza, Self-centering for numerical simulation. Despite the higher complexity of Graesser-Cozzarelli model compared to multilinear Fugazza and Self-centering models, Graesser-Cozzarelli model showed a more detailed description of material behaviour especially in points of transformation of two phases, because of the controller parameters. Also constant parameters of the model were developed to describe the behavior of a bar of 14 mm Cu-Al-Mn by trial and error process in MATLAB. The results of numerical simulation of the behavior of Cu-Al-Mn alloy in tension and pseudo-static test by two models Fugazza and self-centering showed that this model with its simplicity and lack of need for complex laboratory parameters has a good conformity with experimental results.

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.

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.

The steel shear wall is an appropriate resistant system against lateral loads that is been utilized in modern high-rise buildings and upgrading existing buildings because of numerous benefits. This article examined the operation usage of this system in compound reinforced concrete moment frame using suggested connections (additional stirrup). According to this, a steel shear wall three-story reinforced concrete single bay frame (suggested connections) modelled and the plastic behavior and its behavior factor with the reinforced concrete frame, stud connections, and bare reinforced concrete moment frame compared. The result showed that the behavior factor system comparing to bare reinforced concrete frame and reinforced concrete frame contains the steel shear wall with stud connections have increased and about 6.5 (the extent) can be considered.The steel shear wall is an appropriate resistant system against lateral loads that is been utilized in modern high-rise buildings and upgrading existing buildings because of numerous benefits. This article examined the operation usage of this system in compound reinforced concrete moment frame using suggested connections (additional stirrup). According to this, a steel shear wall three-story reinforced concrete single bay frame (suggested connections) modelled and the plastic behavior and its behavior factor with the reinforced concrete frame, stud connections, and bare reinforced concrete moment frame compared. The result showed that the behavior factor system comparing to bare reinforced concrete frame and reinforced concrete frame contains the steel shear wall with stud connections have increased and about 6.5 (the extent) can be considered.

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.