احسان دهقانی

Given the crucial role of cable-stayed bridges and the challenging environmental conditions they often face, monitoring their health is essential. Stay cables, which are the primary load-bearing elements in cable-stayed bridges, are prone to damage due to environmental conditions. This paper investigated the performance of a method for evaluating the cables of a cable-stayed bridge using deck responses, compared to modal parameters. The technique utilized phase space analysis of deck displacement responses in the time domain under a specific moving load. This method was evaluated through a numerical simulation of the Manavgat cable-stayed bridge. Damage scenarios with intensities of 20%, 30%, and 40% were applied to the cross-sections of the cables. Damage identification was carried out by analyzing the changes in phase space topology (CPST) of the responses between the healthy and damaged models, along with two indicators, the modal assurance criterion (MAC) and modal flexibility. The results showed that the CPST index, unlike modal flexibility, identified the damaged cables at all damage levels except for the back-stay cables. The changes in the modal assurance criterion (MAC) at the 40% damage level were also very insignificant. This method can serve as a preliminary approach for fast and continuous monitoring of cables in cable-stayed bridges, minimizing traffic disruption while relying solely on the displacement responses of the deck.

Due to the mechanical behavior of brb braces and concrete frames differing, combining these shows complex behavior in a seismic. It can be used to dual system Brb-Rcf in a concrete moment frame to Improve structural responses. Considering that the behavior of the BRB brace in compression and tension is similar; It can solve the unbalanced force in the Double-K bracing system. The desirability of the Double-K arrangement and its combination with the RCF system as a dual system should be investigated in order to investigate the possibility of using Double-K braces in the RCF system and reducing residual deformations in the case of the dual system. For this purpose, a series of buildings have been analyzed and designed in three structural systems: Rcf, dual frame with brb brace, and bare frame with brb brace according to relevant valid regulations. The pushover and time history analysis have been done, and the capacity curves, base shear, and residual deformation have been investigated and studied. Adding brb braces to the concrete moment frame and dually using them increased the structure's capacity. In the studied structures, from 84% increase capacity in 4-story structure to 94% increase capacity in 12-story structure. This increase is due to the interaction of the concrete moment frame and the brb braces in a dual system. Also, the use of brb braces has made the structure repairable. Because in the concrete structure of the moment frame and the bare frame, the failures were concentrated in the beams and a little in the columns, respectively, but in the structure with Brb-Rcf, the losses were mainly transferred to the braces, which are easily replaceable. Also, the reduction of residual deformation of the structure reduces causes the cost of repair and reconstruction in the structure. Investigations on the formation of hinge showed Due to the Double-K brace that no hinge was formed in the middle of the columns. the losses were mainly transferred to the braces, which are easily replaceable. Also, the reduction of residual deformation of the structure reduces causes the cost of repair and reconstruction in the structure. It was also observed that the structure in combination with the brace in the Brb-Rcf system is designed more economically and with fewer consumables. It is shown in the structure of 8, 4 & 12 story; that the base shear has increased in the frames with brb braces and this increase has been greater in the dual system due to the bending frame and the brb braces. Also, in the hinge, it was observed that the failures of the double structure were less and the types of failures were better according to the replaceability. In general, due to less failure and more base shear that the dual system  structure has, it can be said that the stiffness and resistance due to the interaction of the bending frame and the non-buckling brace has increased, which is the result of the good performance of the dual structure. By comparing the base shear, the suitability of these values ​​with the bearing analysis is clear, so that there also the results showed the increase of the base shear due to the interaction of the frame and the non-buckling brace.

Modification of equivalent acceleration relation of horizontal and vertical earthquakes in ground elliptical tanks was done in the current study. The seismic analysis of the tank is highly important because by investigating the results obtained from this analysis, a useful recognition of the tank behavior quality can be obtained at the time of a real earthquake. The results of the seismic analysis include the impulsive pressure and the wave height of fluid on different points of the tank. In Housner theory, earthquake equivalent acceleration is a key parameter in calculation of impulsive vibration mode parameters such as impulsive pressure and impulsive force. US nuclear reactors and earthquakes code presented a simple relation to calculate earthquake equivalent acceleration. To obtain more calculation accuracy in the ground elliptical tanks, a suitable equation was provided in the current study for the earthquake equivalent acceleration, by the use of principles of statistical regression. Because of less average error, the use of the equation proposed by this study instead of the equation presented by US nuclear reactors and earthquakes code, provides more accuracy in the tank design applications. By the study of the conclusions of this research, it was revealed that the accuracy index of horizontal and vertical earthquake equivalent acceleration relations developed by this research is 16% and 26% more than that of the corresponding relations of US nuclear reactors and earthquakes code, respectively.

Due to developments in the field of fast transportation, increase in permitted speed and load capacity, moving loads can have significant effects on the dynamic forces of bridges. To consider the dynamic effect in the design of the structure, the dynamic impact factor is introduced as ratio of the dynamic response to the static response. Accurate evaluation of these coefficients helps in safe and economic designs for new bridges. However, the evaluation of the dynamic impact factor is difficult due to the vehicle-bridge interaction and the influence of many parameters that affect the dynamic impact factor, including the dynamic characteristics of the bridge and the vehicle, road surface conditions, vehicle speed, traffic conditions,. In this research, by applying live load of vehicles step by step and performing time history analysis, dynamic analysis under moving load has been done. Three different types of cable-stayed bridges with different spans and cable layouts have been investigated in the form of two-dimensional models. This study analyzes the impact coefficient of bending and shear forces of deck components and pylons, as well as the axial forces of cables, and the results are compared with the coefficients proposed in the design regulations. Also, the effect of changes in load passing speed on the dynamic impact factor in cable-stayed bridges has also been evaluated and studied. This research tries to improve and optimize the design and performance of cable-stayed bridges in order to deal with dynamic changes and increase the speed of loads.

The method for retaining the excavated pit could have a significant effect on the soil pressure acting on the retaining walls; For this purpose, since the Top-Down construction method is widely used, In this study, a series of numerical analyses has been conducted to investigate the effect of the excavation method and the distribution of the structural elements on the soil pressure distribution. Generally, for engineering purposes, active and at-rest soil pressure distribution and the Peck apparent pressure distribution (in the case of retained walls) are used for soil pressure determination. The results of the study suggest that in contrast to the at-rest and active soil pressure distribution, the pressure distribution on retaining walls has no similarity with the triangular distribution and the Peck's APD provides an acceptable estimation of soil pressure and its distribution. The results also show that with the increase of deformation due to the construction of the wall, as an example in one case, a 60% increase in ground settlement reduced the soil pressure acting on the walls by up to 15%. It's also noteworthy that this study focuses only on a special type of soil, So the result might be inapplicable to other circum-stances.

Stroke is the third most common cause of death in developed countries and the most common neurologically debilitating disease. The aim of this study was to investigate the 5-year epidemiological prevalence of stroke cases in Ahvaz, Iran.

In this descriptive cross-sectional study, the files of patients admitted to the neurology ward of Golestan Hospital in Ahvaz, Iran who were diagnosed with stroke based on clinical symptoms and CT scan during the years 2015-2019 were reviewed. Relevant data were analyzed by SPSS software and statistical tests.

The mean age of patients was 66.58±14.31 years and 55.2% were male. 22.9% of patients were smoker, 4.4% consumed alcohol and 10.9% consumed opioids. Also, 95.1% of patients lacked regular physical activity. In terms of comorbidities, 68% of patients had hypertension, 42.4% had diabetes, 19% had dyslipidemia and 8.1% had autoimmune diseases. In addition, 26.3% of patients had a previous history of stroke, 34.1% had a history of heart attack and 43.5% of patients had a family history of stroke. Re-stroke was significantly associated with family history of stroke (P<0.05) but was not significantly associated with gender and age.

In patients with stroke, low physical activity, high blood pressure and diabetes were high, which shows the importance of attention and correction of these risk factors to prevent stroke.

The effect of liquid tanks shape on their seismic behavior considering fluid – structure and soil – structure interactions has been investigated in the current study. Basically, the tank is a structure used to store different types of fluid, and it is also widely used in refineries, sewage treatment plants and factories in the form of on ground and elevated tanks made from concrete and steel. Regarding the application of the huge dynamic and hydrodynamic loads on a tank at the time of earthquake and the great importance of the structure’s complete function continuity in the critical situations, it is highly important to study its seismic behavior. Among the different analyses, the seismic analysis of the tank is highly important because by investigating the results obtained from this analysis, a useful recognition of the quality of the tank’s behavior at the time of a real earthquake can be obtained. The equivalent rectangular and diamond and ellipticalburiedliquid tanks have been dinamicallyanalyzedunder Elcentro andManjil and Cape earthquakes simoultaneously in the longitudinal and transverse directions and the variousseismicparametersof the system such as thewave maximum height,wallmaximumdrift,concrete maximum tensile stresses and soil maximum compressive stress have been compared with eachother in above mentioned cases in the current research. By study of the computed results of current research, it was revealed that the liquid tanks shape has a considerable effecton their seismic behavior in the same conditions. It also was revealed that the effecttype of variousshapes is not same on the various seismic parameters.

One of the most important properties of concrete structures is their ductile behavior against earthquakes. The ductility of a structure includes resisting relatively high plastic deflection without significant reduction of structural strength and absorption of earthquake energy through hysteresis behavior. Different design codes have considered requirements for the ductility of various structural elements. The purpose of this study is to investigate the optimal design equation for stirrups used in ductile reinforced concrete columns. In this investigation, stirrups for three types of columns including the circular column with 750 mm diameter and rectangular columns with dimensions 1000×1000 and 500×500 mm in medium and high ductility were studied. Also, two types of concrete strength 30 and 60 MPa were considered to evaluate the effect of concrete strength. The required stirrups obtained from the proposed equations were compared with IR code and ACI. Moreover, numerical simulation using ABAQUS software for the aforementioned situations was performed. Finally, the results obtained from DBA and Vikor methods considering axial and rotational ductility, and cost showed that the proposed equations are the most optimal design equation in medium ductility. Also, the proposed equations are the best in high ductility when they were used to columns with concrete strength of 30 MPa. In concrete strength 60 MPa, the equations suggested by ACI and IR code are the most optimum as they were applied to the circular column and the rectangular column with cross-section 1000×1000 in high ductility, respectively.

The seismicbehavior of the on ground quadroplete elliptical tanks has been investigated in the current study. Basically, the tank is a structure used to store different types of fluid, and it is also widely used in refineries, sewage treatment plants and factories in the form of on ground and elevated tanks made from concrete and steel. Regarding the application of the huge dynamic and hydrodynamic loads on a tank at the time of earthquake and the great importance of the structure’s complete function continuity in the critical situations, it is highly important to study its seismic behavior. Among the different analyses, the seismic analysis of the tank is highly important because by investigating the results obtained from this analysis, a useful recognition of the quality of the tank’s behavior at the time of a real earthquake can be obtained. The monoplete and quadroplete on ground elliptical tanks have been dinamicallyanalyzedunder Cape and Tabas and Manjil earthquakes simoultaneously in the longitudinal and transverse directions in various conditions of prolateness and slenderness of the tankand the maximum impulsive pressure and the maximum wave height parameters of corresponding cases have been compared with eachother in the current research. By study of the concluded diagrams, it was revealed that the reductionpercent of the maximum impulsive pressure and the maximum wave height parameters due to partitioning of the tank is higher in the more slender tanks. It also was revealed that the reductionpercent of the maximum impulsive pressure and the maximum wave height parameters due to partitioning of the tank is lower in the more prolate tanks.

The seismic behavior of the on ground bipartite elliptical tanks has been investigated in the current study. Basically, the tank is a structure used to store different types of fluid, and it is also widely used in refineries, sewage treatment plants and factories in the form of on ground and elevated tanks made from concrete and steel. The monoplete and double on ground elliptical tanks have been dinamically analyzed under Cape and Tabas earthquakes simoultaneously in the longitudinal and transverse directions in various conditions of prolateness and slenderness of the tank and the maximum impulsive pressure and the maximum wave height parameters of corresponding cases have been compared with eachother in the current research. By study of the concluded diagrams, it was revealed that the reduction percent of the maximum impulsive pressure and the maximum wave height parameters due to partitioning of the tank is higher in more slender tanks. It also was revealed that the reduction percent of the maximum impulsive pressure and the maximum wave height parameters due to partitioning of the tank is higher in more prolate tanks.

Increasing the resistance of members or adding constraints to the structure does not jeopardize the overall safety of the structure. This can be proved under certain static loads by the safe theorem which is one of the fundamental theories of plastic analysis. Although this theorem has not proved in the condition of dynamic loads, its results are used in the everyday design under dynamic loads, so this paper attempts to numerically study these results under dynamic loads. Since the concept of mechanism and collapse cannot be investigated under transient loads, the level of ductility demand of structural components is considered to ensure the safety of the structure. For this purpose, the plastic rotation of the members was extracted after a minor variation in resistance and stiffness of the beams in a 2D-five-story steel moment frame by performing dynamic analysis. To compare ductility demand in dynamic analysis with criteria values, the evaluation was surveyed under nonlinear static analysis. The results analysis shows that with the increasing resistance, in most cases the ductility demand decreases, and in some cases the maximum increases by 7.3%. With increasing stiffness, the ductility demand has increased by a maximum of 16%.By comparing the results of dynamic and static analysis, it can be concluded that the required ductility in the dynamic analysis by increasing characteristics has been lower than the corresponding value in static analysis. Therefore, the increase in the partial stiffness and resistance of the beams under dynamic loads has not caused the structural collapse.

According to the basic theorems of plastic analysis of structures, increasing the strength or stiffness of a part of the structure does not weaken it under a specific static load. This result is widely used to simplify the modeling and design of structures, but these theorems have not been proven under dynamic loading like earthquake excitations. This study applies the results of the safe theorem numerically in a two-dimensional steel moment-frame structure with five stories under nonlinear dynamic analysis with 29 different earthquake ground motion records. Under transient dynamic loading conditions, because the mechanism or collapse does not occur in the structure, the safety of the structure is investigated by maximum rotational deformation of the members. By changing the characteristics such as local stiffness and strength of the members in the range of 0.8 to 1.5 times the initial value, the maximum deformation demand of the members has been compared. The results of the dynamic analysis show that upon increasing strength, in most cases, the demand for ductility decreases and with increasing stiffness, in almost all cases, the ductility demand increases. The results of nonlinear static analysis are compared with the nonlinear dynamic analysis in cases where increasing stiffness has increased the ductility demand. From this comparison, it can be concluded that upon increasing the stiffness of the members locally, the demand for ductility in the dynamic analysis is less than its corresponding value in static analysis. As a result, it can be said that by increasing the stiffness of the structure, observing the limitations of the codes for the ductility capacity of members and connections leads to the safety of the structure. Generally, it is concluded that the safety of the structure is not compromised by minor increase in the strength and minor increase in stiffness of some members of the structure under dynamic loading if regular limitations of the codes for the ductility capacity have been observed.

Lateral torsional buckling is one of the important criterion for determining the flexural strength in steel beam design. probability of it increases when laterally unbraced length is long. On one hand, lateral bracing should have sufficient stiffness to provide lateral support for compression flange of beam. On the other hand, this support must has enough strength. Composite beams consist of reinforced concrete slab and steel beam. To join the reinforced concrete and steel beam, stud has been used to transfer the horizontal force from concrete to steel beams. In fact, it plays role of lateral bracing for top flange.  Bottom flange is also under pressure in the case of double curvature bending and there is probability of lateral torsional buckling. Common methods of beam lateral bracing are connecting two adjacent beams to each other and connectig bottom flange to concrete slab. In this study a new detail has been introduced for lateral bracing of the beam-slab composite system. In this study, bottom flange is connected to concrete slab by a pair of transverse web stiffeners and its rotation is prevented by a pair of transverse studs. Finite element analysis results show that this detail can prevent  bottom flange from lateral torsional buckling.

In the present paper, a numerical investigation aimed at determining the significance of temperature distribution, pore pressures, and thermally induced stresses for spalling of concrete under fire conditions is performed. In this paper three types of concrete are evaluated: concrete with quartz aggregate, concrete with limestone aggregate, concrete with basalt aggregate. All of these aggregates are abundant in our country and are used in concrete admixtures. Results show that spalling in Quartz-based concrete is higher than others and this concrete exposes to decreasing in strength under fire in comparison to others, and increasing concrete segment depth or adding the specified amount of polypropylene fiber in concrete mix can improve the fire performance of concrete pieces.

Recently, an increase in the demand of petroleum derivatives has caused to pay particularattention to environmental issues of processes pertaining to its production, distribution andrecovery in addition to the need to manage its supply chain. In this regard, this study has designedand planned a green closed-loop supply chain network for an engine oil product underuncertainty. The proposed model encompasses two objectives in such a way the first objectivefunction aims at minimizing the costs of supply chain and the second one considersenvironmental effects of the related activities. In accordance with the multi objectives of themodel, the ε-constraint method is deployed to solve the concerned model. Likewise, the demandof the main product and the amount of recyclables from the demand markets are presumed to behemmed in by uncertainty. To cope with the considered uncertainty, the Mulvey optimizationmethod is exploited. Meanwhile, new methods for recycling and disposal of non-recyclablematerials are discussed in the proposed model. Eventually, the validation of the proposed modelis evaluated using data from Behran Oil Company.

Concrete is a useful material in today industry that must be known behavior against environmental phenomenon including fire concurrent using this material in various industries. Generally, in concrete two phases being visible, the solid phase includes cement paste with other aggregates and additives, and liquid phase includes water placing in concrete pores. When applying the fire in the concrete segments, in addition to some reactions occur in the solid phase, some changes are seen in the liquid phase and gradually gas phase including vapor in the concrete pores will be built. Usually, evaporation starts in concrete pores water at the 100 °C temperature and since concrete temperature passes 150 °C all of the water in pores changes to vapor and flows in the colder side of concrete and accumulate at this portion. When 100 °C front temperature further progresses in the concrete, evaporation speed increases and flows in the colder side and accumulation zone of water grows until this zone becomes full of vapor and creates a saturated layer in pores that prevents from fluid flowing. After this layer saturated by vapor invasion from the hot side, pore pressure gradually develops and with this event tension stresses at this side of concrete will increase. With continue increasing fire intensity, saturated layer creation speed increases and pore pressure and tension stress increment occur. In the following of this process, if tension stress is becoming bigger than tensile strength, fracturing and loss of material from this layer are caused, i.e. spalling occurs. This paper present an analytical modeling using ABAQUS software to evaluating concrete fire behavior. Modeling and analysis of concrete slab under fire in this study includes some steps. In the first step, heat transfer modeling and analysis of solid part is done. In the following "soils" analysis based on initial heat transfer analysis result is accomplished, that vapor flowing between pores, the saturated layer forming and pore pressure developing occur in this step. Concurrent soils analysis, using USDFLD and UMESHMOTION subroutines that joined to software, pore pressure, and tension stress value are controlled and if spalling occurs in the concrete slab, spalled layer depth and time of spalling are determined and saved. One of the most important issues facing in the fire at structures is elevated temperature patterns subject and especially fire curves types. Because of the importance of this issue, some of these fire curves placed in the famous codes. One of the most popular fire curves in the structure is the ISO834 fire curve that based on cellulose fire. Although many researchers use the ISO834 fire curve in their research, when a fire occurs in structure with petroleum and hydrocarbons products, elevated temperature speed is higher than ISO834. So the fire curve based on low petroleum product in the structure presented, is named hydrocarbon (HC) curve. Results show that applying Hydrocarbon fire in concrete increase pore pressure more than double and accelerate spalling process in comparison to ISO834 fire and by modifying permeability of concrete from 5x10-17m2 to 5x10-16m2, pore pressure decrease less than one tenth even prevent spalling phenomenon.

Concrete core capability of a reinforced concrete columns to withstand compressive strain caused by the confinement pressure increases. In order to ensure proper lateral deformation capacity of reinforced concrete columns enclosing the bars should be increased according to the axial load. On the other hand, the strength and flexibility of each reinforced concrete is enhanced by improving the enclosure of plastic hinge areas. This ensures improved seismic stability during an earthquake. One of the most important characteristics of concrete structures against the forces of earthquake is their ductile behavior. Finding the values for standard plasticity due to the complexity of the structural behavior and the lack of explicit all its influencing factors, is associated with many problems. Also various regulations are expressing the different criteria for ductility. The purpose of the present study is to provide a confinement criterion based on the need for ductility. In this article, we review the various regulations, is extracted relations for design of enclosed transverse reinforcement of two type of columns, with circular and rectangular sections, In the case of medium and high ductility. In order to verify the relations, reinforcement values for designing reinforced concrete columns evaluated with the values obtained from Iranian national regulations relations. The results of the proposed relations show that the values of the design reinforcement of sections for both levels of ductility is reduced .

The presence of the link beam in eccentrically braced frames is primarily responsible for different behavior of this frame with other structural systems. In accordance with the FEMA 356, for the evaluation of the performance of the link beam in all of its behavioral areas, the plastic rotation of the plastic hinges is required. In many studies, for the modeling of the link beam, at two end of an elastic beam, two bending and shear plastic hinge are modeled simultaneously. In this method, it is not possible to model the generalized behavior of the beam and evaluate its performance in accordance with the FEMA 356. In this paper, a new method for modeling the behavior of the link beam is presented. According to this method, at the location of the joint formation, only one flexural joint is modeled and its behavior is determined to be equivalent to the behavior of the link beam. In addition to presenting a new method for link beam modeling, the process of calculating the target displacement for each level of performance is described. OpenSees software has been utilized to model and analyze. Finally, for verifying the process of calculating the target displacement of performance levels and the proposed modeling method, the results of nonlinear static analysis of a 2D eccentrically braced frame are presented and compared with the results of the SAP2000. Comparison of the results confirms the accuracy of the modeling and the process of calculating the target displacement.

Today one of the most common systems for resisting lateral forces (wind and earthquake) is special concentrically braced frames (SCBF). Out of plane buckling in compression causes large inelastic flexural deformations in gusset plate. In order to supply the capacity of inelastic deformations in gusset plate, current design practice recommends a “2t” linear geometric offset to be used. Recent research has been done to improve the seismic behavior of connections for braced frames shown that the use of a clearance by elliptical pattern has better results than linear pattern clearance.
In this paper using the finite element method, a one-story frame under cyclic loads and considering the nonlinear effects of material and geometric has been modeled and verified. The parameters that considered are effect of clearance (linear, elliptical and lack of clearance) at different angles and clearance in an elliptical pattern. The results of the samples, hysteresis curve, compressive and tensile resistance, as well as stress and strain showed that the clearance effect on tensile strength and compressive is between 2.86 to 13.5 percent for different angles of connected braces. Ductility in the case of lack of clearance between angles of 30 to 60 degrees reduced 30 to 60 percent relative to the elliptical clearance

In today`s world urban railway is one of the important transportation systems that should be examined against various environmental phenomena including fire condition to service permanent citizens. Usually construction of concrete segments of the tunnel simultaneous to used high strength concrete (HSC) that have bad reaction under fire in spite of good seismic reaction. When a fire occurs in tunnel surrounding, some interaction occurred in concrete segments of the tunnel that can reduce the thickness and decrease the safety of these segments. Most of the researches in applying heat effect on concrete segments of the tunnel are experimental and under this situation and analytical or numerical researches in this issue are low. This paper presents an analytical model using ABAQUS software based on the finite element for evaluating concrete segments of tunnel behaviour under fire condition. To ensure the safety of results, some fire curves are applied and effect of Polypropylene fiber in the concrete mix is evaluated. Results show that adding minimum 0.9 Kg per cubic meter of concrete mix in concrete segments of tunnel causing loss of spalling and improve fire behavior interaction.

The dynamic characteristics of different structures have led to the development of various analytical methods for analyzing the seismic behavior of structures. The existence of a predominant period in the structure is one of the features that can be used in analytical simplifications. Steel arch bridge is one of the systems for covering relatively long span. Mass distribution of steel arch bridge is the most important reason complexity of their seismic analysis. In this study a 300m span steel arch bridge has been investigated as a sample in the longitudinal direction. A comprehensive study has been carried out on the application of a capacity and demand prediction procedure based on incremental dynamic analysis with 17 seismic records for seismic performance evaluation of that bridge. Also results of IDA have been compared with nonlinear pushover analysis, and incremental dynamic analysis with sinusoidal record. Load pattern of pushover analysis is considered in two cases: inertia force distribution and modal force distribution. Nonlinear material effects are considered in the form of a concentrated plastic joint. The results show that Mass distributions of steel arch bridge due to this structure have not a predominant period and their seismic behavior is different under different accelerations because different mode shapes of structure are incitement. Also, by removing the mass of the arch element of the bridge and creating a model with predominant mode in the longitudinal direction, the results of its incremental dynamical analysis and nonlinear pushover analysis are investigated. Finally, a new approach is used for IDA by selecting harmonic base acceleration functions. This method is able to reduce the calculation cost of IDA with same accuracy of ground motion time histories.

Structural walls are widely used in building structures as the major structural members to provide substantial lateral strength, stiffness and the inelastic deformation capacity needed to withstand earthquake ground motions. In this article the behavior of composite shear walls with continuous boundary elements are compared and contrasted with a state in which the wall’s boundary elements are discontinuous and interrupted and the boundary steel columns are connected to the foundation through the column’s baseplate and bolts; and these are all to assess and appraise some hypotheses by the structural designers in designing these walls. The finite element software is first calibrated and the accuracy of its results is validated through modeling the experimental samples. In this research, the concrete’s nonlinear finite element analysis method and concrete damage plasticity model have been used for the concrete’s behavior modeling. The results of this study indicate that the wall boundary elements’ continuity improve the composite shear walls’ behavior. Meanwhile, this effect increases by an increase in the number of the wall’s floors.

Composite construction in steel and concrete offers significant advantages for use as the primary lateral resistance systems in building structures subjected to seismic loading. While composite construction has been common for over half a century through the use of composite beam and joist floor systems, over the past decade a substantial amount of research has been conducted worldwide on a wide range of composite lateral resistance systems. These systems include unbraced moment frames consisting of steel girders with concrete-filled steel tube (CFT) or steel reinforced concrete (i.e., encased steel sections, or SRC) beam-columns; braced frames having concrete-filled steel tube columns; and a variety of composite and hybrid wall systems.
Structural walls are widely used in building structures as the major structural members to provide substantial lateral strength, stiffness, and the inelastic deformation capacity needed to withstand earthquake ground motions. In recent years, steel reinforced concrete (SRC) walls have gained popularity for use in high-rise buildings in regions of high seismicity. SRC walls have additional structural steel embedded in the boundary elements of the reinforced concrete (RC) walls. Walls with additional shapes referred as composite steel-concrete shear walls, contain one or more encased steel shapes, usually located at the ends of the wall.
Composite shear walls with steel boundary element are known as the structural members able to withstand high in-plane lateral forces at low displacement levels. Reinforced concrete shear walls with steel boundary element being performed in Iran are joined to the foundation, in boundary element section, usually through bolts and base plates. Most reliable codes of the world have nothing to say about the behavior of this type of shear walls, and no experimental studies or analyses have been conducted on the behavior of this type of shear walls. In the past decade, great effort has been devoted to the study of seismic behavior of SRC walls, for Design provisions for SRC walls have also been included in some leading design codes and specifications, for example, AISC 341-10 , Eurocode 8, and JGJ 3-2010
Exposed baseplates together with anchor bolts are the customary method of connection of steel structures to the concrete footings . In this paper, the influence of cross section of base plate’s joint bolts to the foundation and the wall’s longitudinal bars embedding within the area of boundary element in the foundation, on the behavior of this type of shear walls have been investigated. The finite element software is first calibrated and the accuracy of its results is validated through modeling the experimental samples. In this research, the concrete’s nonlinear finite element analysis method and concrete damage plasticity model have been used for the concrete’s behavior modeling. The results show that increasing in the level of bolt’s cross section and also the embedding of longitudinal bars of boundary element in the foundation cause an improvement of the capacity of these walls. However, these walls’ resistance against the normal axial loads is considered to be less than reinforced concrete shear wall.

In most steel frame designs the beam to column connections are assumed to be rigid or pinned but in many steel frames we have beam to column connections with semi-rigid behavior. The structures with semi-rigid connections include systems with the connections in joints which are not completely rigid, but allow, usually, some relative movements in directions of generalized displacements.
Early experimental studies showed the importance of panel shear deformations for stable energy dissipation under cyclic loading. Modeling of the panel is very important for the avoidance of local failure of columns under ultimate limit state.
A substantial effort has been made in recent years to characterize the behavior of semi rigid connections. Recent studies and modern codes, in especially EC3 and EC4, include methods and formulas to resistance and stiffness of panel zone. EC3 proposes a mechanical model for the semi-rigid joint in which each component is modeled by an equivalent linear spring.In these model we have some components that show with springs. These springs are assembled to form a single bilinear (elastic–plastic) rotational spring that models the connection, and is attached at the intersection between beam and column for the global analysis.
Both the stiffness and strength of the springs in EC3 and EC4 depend on β factor that definition of this parameter implies an approximation of the internal forces at the joint, and therefore its use requires an iterative process at the time of performing the global analysis of the structure. So E.Bayo proposed a new component-based method (or cruciform element method) to model internal and external semi-rigid connections that revived and modified EC methods. So a cruciform element (a four-node element) is proposed to avoid β factor, and the inherent initial guessing and iterative process that it requires, and includes the finite size and deformation modes of the joint.
One of main problems that structural engineer deal with is considering End Length Offset in conventional softwares. Extended end plate connection is one of beam-column semi rigid connection that we want to evaluate this behavios by using cruciform connection model and other panel zone models.
In this paper three 2 dimensional frames with extended end plate connections are modeld in MATLAB using Cruciform element method and these result are compared with SAP2000 results in eight cases that in four cases panel zone are modeld and four cases are without panel zone modeling. In which of this End Length Offset considering are once just for beams and the other for beams and columns (in two case of Rigid Zone Factor : 0.5 and 1). The results show that modeling panel zones according to EC method and considering Rigid Zone Factor equal to 1 in columns and beams are best assumption to analysis of 2D frames with extend end plate connections, but if we don’t model panel zones, we must considering Rigid Zone Factor equal to 0.5 in columns and beams to give nearby actual results.