For the construction of railway embankments, geotechnical engineers pay special attention to slope stability studies. The factor of safety values plays a crucial part in assessing the safe design of slopes. The factor of safety values is used to determine how close or far slopes are from failing due to natural or man-made causes. The factor of safety is a numeric value to indicate the relative stability, it doesn’t tell about the actual risk level of any structure, but the reliability index and probability of failure quantify the risk level. The present study discusses the findings of a study to determine the factor of safety of an embankment of height 12.3 m by using Geo-studio 2012 software. In this article, the fragility curve for six different types of cross-sections was also developed i.e. the graph between the probability of failure ( ) and horizontal seismic coefficient ( ), for various values of  (i.e. 0.1, 0.12, 0.144, 0.18, 0.2, 0.3, 0.4 and 0.5). It is observed from the developed fragility curve, as the  value increases  value decreases. A fragility curve can be used to calculate failure probability over a range of seismic zones, and for design purposes, a given seismic zone and probability of failure a unique reliable side slope is selected. Further, two machine learning (ML) models namely, Deep Neural Network (DNN) and Support Vector Regression (SVR) have been developed for the prediction of the factor of safety for different sides slope. Obtained correlation values (R) for SVR and DNN are approximately 0.95 and 0.82 respectively. From the help of the predicted factor of safety fragility curve against horizontal seismic coefficient is drawn for both SVR and DNN models, that for reducing the time of calculation and ease in working best result giving model will be suggested for further analysis of railway embankment.

In this study to determine the reduce beam section effect, on intermediate moment frame system behavior and its results, are discussed. For this purpose, non-linear static analysis is used. Generally, two types of structures have been selected in this study, the first 5, 10 and 15-story moment frame and the second with a cross section reduction in beam structures. Since this research has been done using software Open SEES also to modeling reduce beam section, we used Krawinkler-Ibarra rotational spring model with concentrate plasticity on beams. After verification of RBS for a cantilever beam, this model has been extended to multi degree of freedom buildings. Finally different models have been subjected to incremental dynamic analysis and the results of analyzing the flexural structures of the frame and RBS structures have been used to calculate and extract the fracture curves of the structures and compare them. With respect to the fracture curve graphs of intermediate structures, the probability of colliding the IMF model with the RBS is higher.

Nowadays, according to the global population growth, building and automobile generation are increasing. Hence, the vehicle collision to structures is increasing too, and these events may cause more vulnerability on structures. That's why, these structures need to be re-evaluated for strengthening and rehabilitating, but this issue is usually ignored and neglected. For this reason, in this study has been made an effort to determine, the rate of concrete structure vulnerability under vehicle collision on corner and middle columns with 10, 60 and 100 km/h speeds with19 seismic records simultaneously as incremental dynamic analysis (IDA). Also this speeds may be define as low, medium and high speeds. At initiation, by ETABS software and according to Iran's seismic design code of buildings (4th edition) a concrete structure with intermediate moment frame system was designed. Then to obtain the force-time spectrum, the vehicle collision and a concrete structure was simulated by LSDYNA software. After that this building was analysed under several force-time spectrum and 19 seismic records in near field. After that the fragility curves due to incremental dynamic analysis (IDA) were drawn. Finally, according to failure indicators from HAZUS standard, the probability of damage from vehicle collision and 19 seismic records on corner and middle columns was evaluated. Then it was specified, the collision causes permanent deformations on structural elements and increasing in vehicle speed will increase the horizontal displacement of story and reduces the base shear, as well as increases the rate of damage on structure finally. For instance, the rate of displacement ratio from vehicle collision to concrete structure with 10, 60 and 100 speeds, which indicates the rate of damage, applied on structure is equal 0.00152, 0.00515 and 0.023.

In this study, the probabilistic seismic performance of building frames with non-buckling braces has been investigated using the incremental dynamic analysis method based on the pushover curve obtained from the non-linear static analysis. The incremental dynamic analysis method is known as one of the accurate analysis methods for estimating the lateral seismic collapse capacity of structures, but it is costly due to the need for nonlinear dynamic analyzes in a record-by-record approach. In this article, without performing such time-consuming analyzes of incremental dynamic method, with proper accuracy and using the results of non-linear static analysis and applying an algorithm to extract the summary of incremental dynamic analysis curves from the results of non-linear static analysis, incremental dynamic analysis curves have been extracted in quantiles of 16, 50, and 84%, and in the following, after obtaining the statistical characteristics of the earthquake intensity at the thresholds of the damage parameter such as the relative displacement of the floor, the seismic evaluation of the studied structures at different performance levels has been carried out in a probabilistic approach and with the drawing of fragility curves. The results of the average acceleration in the performance levels of life safety (i.e., in the risk level of earthquakes with a return period of 475 years) 1.30 g, 0.77 g, 0.92 g, and 0.60 g, and the threshold of collapse (i.e., in the risk level Earthquakes with a return period of 2475 years) are 1.56 g, 0.96 g, 1.15 g, and 0.75 g for frames of 4, 8, 12, and 16 floors, respectively. Therefore, the results show that only in the 4-story frame, the intended performance for seismic risk levels has been provided, and other frames have not been able to provide the required performance criteria.

The steel braced frame system is one of the lateral load resisting systems which is used extensively for low-to mid-rise buildings. In this structural system, the braces can be arranged in different forms along the building height due to different reasons such as architectural and structural limitations or design considerations. The bracing arrangement affects the seismic performance of the structural system and each of the elements. In this study, the impact of bracing arrangement along the building height on ultimate failure capacity and collapse fragility curves of steel CBFs is investigated. For this purpose, 4 and 8-story steel CBF buildings with 6 different arrangements of braces were selected and modeled in PERFORM-3D software. The models were then analyzed using the incremental dynamic analysis (IDA) method. Afterwards, the collapse capacity of the models and the uncertainty index were calculated, and the collapse fragility curves were generated. The results show that, by modifying the arrangement of braces without significant changes in lateral stiffness and fundamental period of structure, it is possible to increase the collapse spectral acceleration and decrease the probability of collapse at the maximum considered earthquake intensity.

The containment structure of nuclear reactors is the most crucial barrier to releasing radioactive materials into the environment and protecting the reactor against external hazards such as earthquakes and floods. After the Fukushima nuclear accident, the safety of this structure in the earthquake has received much attention. Iran is also located in a region with high and very high seismic hazards and is essential. In this study, the seismic fragility curve of the containment structure of pressurized water reactors used in Bushehr has been determined by considering different failure modes. For this purpose, a computer model simulated in ABAQUS software and incremental dynamic analysis (IDA) have been used. The finite element model has been validated using a lumped mass model. Different failure modes are defined in terms of critical stresses in concrete, rebar, tendons, and steel plate attached to the containment body. Critical points of containment have been identified in terms of these failures. Concrete materials fail at a lower acceleration than other materials. At peak ground accelerations of less than 0. 2 g, concrete remains elastic, and no cracks are formed,however, at peak ground accelerations of 2. 2 g to 2. 75 g, concrete cracks of more than 2 mm form, which allow the release of radioactive materials into the environment. The parameters of fragility, median acceleration capacity, and logarithmic standard deviation of median acceleration capacity were determined to be 2. 251 and 0. 155, respectively.

Seismic risk assessment of structures is an important and practical tool for seismic safety assessment, earthquake consequence analysis, seismic strengthening planning and post-earthquake crisis management. This assessment consists of various parts including seismic hazard analysis, exposure evaluation, vulnerability analysis, and risk estimation. One of the most important parts of this process is the development of structural fragility functions or curves for undesired performance. Various methods have been used to determine fragility functions. In most of these methods, a general limit state such as maximum relative displacement of the floors is considered as failure mode, while in older buildings, more failure modes such as shear failure mode of structural members are usually prevailing.In this paper, a framework for determining the fragility functions of structural collapse based on different failure modes of structural members using fault tree analysis is presented. This method includes developing the fault tree of the undesired performance of the structure (through possible failure modes in members), preparing a suitable computer model of the structure according to failure modes, selecting earthquake acceleration records for IDA analysis, determining the capacity and limit mode of failure modes based on laboratory results or standards, performing IDA analysis for the structure and forming a fragility table, calculating the fragility parameters using a suitable statistical distribution and plotting the seismic fragility curve for each of the base events in fault tree and quantifying the fault tree, and finally deriving the fragility curve of the structure.This method was applied on a reinforced concrete building frame made in Europe according to the design criteria of the 50s and 60s, and then the results were compared with the conventional method of developing fragility functions, which is based on the general limit state of maximum relative displacement of floors. Because the main reason for the weakness of the frame under study is the weakness in shear of the columns due to the lack of seismic transverse reinforcement details at the time of their design and construction, in next stage, the fragility function of the studied frame is determined by observing the criteria of seismic transverse reinforcement and is compared with the fragility function of the existing frame without observing these criteria. The results show a much lower median estimate of the capacity of the fragility function due to the shear weakness of the old frames in the proposed method compared to the conventional method. The fragility curves derived from conventional methods match very well with the failure mode causing weak-storey on the first floor. This observation is in good agreement with the results presented in the references in which the main collapse mode for this frame is the failure of the weak floor in the first floor. Another observable result in the proposed method is the reduction of the dispersion of the results using this method compared to the conventional method because the fragility curve obtained from this method covers a narrower range than the conventional method.Considering the criteria of transverse reinforcement, it was observed that in many columns, the philosophy of designing new regulations, which is flexural failure before shear failure, has occurred, which shows the high importance of transverse reinforcement in column sections. By observing the criteria of transverse reinforcement of sections, the most vulnerable part of this frame are the columns of row 2 in shear failure mode, due to the significant difference in the cross-sectional height of the columns of this row compared to other rows. This difference in the height of the sections leads to high absorption of shear force in the section, which causes the force to pass through the capacity much faster and as a result, its high vulnerability. Finally, comparing the fragility curves of frame collapse in two cases with considering the seismic shear reinforcement criteria and without considering it shows the significant effect of cross-section reinforcement criteria on the seismic fragility function of structures.

Like any other complex system, cities fragment when they are not properly managed. Thus, the fragility conditions should be understood to calculate the effective strategies in responses. This study aims to explain the factors of fragility in the metropolitan city of Tehran using structural approach. This field study seeks to identify the factors effective in the fragility of Tehran using a descriptive-analytical approach. In order to formulate the theoretical framework, the related literature was reviewed using the documentation method. Then, experimental data were extracted based on the environmental scanning technique. The population included 14 experts and specialists in the field of urban planning, who were selected based on purposive sampling. To this aim, 91 factors were extracted as primary indicators of urban fragility based on the theoretical literature. Then, 51 factors with a lower percentage of consensuses were eliminated and 40 ones remained based on experts’ opinions taken through a questionnaire. In the next step, the answers were analyzed and evaluated applying structural mutual effects analysis in MicMac software, resulting in determining the degree of direct and indirect influence of the factors on each other and on the fragility process of Tehran. According to the results, 20 factors play a significant role in the fragility of Tehran among 40 primary influencing ones. The above-mentioned factors are rapid growth of urbanization, concentrated poverty, widespread financial corruption, social and gender inequality, unemployment rate, political instability, epidemic diseases, informal settlements, urban violence, economic security, people's participation, lack of basic urban services, exposure to natural disasters, social security, income inequality, improper distribution of security-development capacities, sanctions, global economic shocks, real insecurity, and sudden price shocks.

Following a large earthquake, numerous aftershocks can be triggered due to the complex stress interaction between and within tectonic plates. Although aftershocks are normally smaller in magnitude, their ground motion intensity can be large and have different energy contents than the mainshock. Even seemingly, undamaged buildings may be damaged as a result of aftershocks. The mainshock-damaged buildings with deteriorated structural properties are more susceptible to damage. Based on the achievements of structural engineering and earthquake today, design of structures based on performance can be mentioned. Firstly, unlike traditional methods, new structures can be designed based on seismic needs and functional levels; secondly, the possibility of retrofitting existing buildings is provided. There are also famous ATC and FEMA regulations in this field. In this research, the performance of steel structure with eccentric braced frames being affected by sequence earthquakes has been studied. To do so, low-rise buildings of 3, 5, and 7 stories have been analyzed in terms of time history dynamics by nonlinear software of Perform 3D. By drawing the fragility curve of structures at different levels of performance, the seismic vulnerability of structures has been investigated. The results indicate that as the number of stories increases, the seismic vulnerability of the structure decreases, and the probability of failure in Far-field earthquakes is higher than near-fault earthquakes. In a seismic sequence discussion, the second earthquake is often affected by the fact that its PGA is larger than the first earthquake. In other words, when the PGA is the second earthquake smaller than or equal to the first earthquake, its effect on structures is very slight, which can be ignored. With regard to the fragility curves achieved, it can be concluded that the structure at the level of the safety of life (LS), which is the standard 2800 and the topic of the tenth subject of the national building regulations, has a good performance, and the design based on them is reliable.