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Recently, the Iranian code is established for the LRFD design of steel structures that consistent with the Iranian seismic design code (2800-4). This study is aimed to compare the performance of steel moment frames (SMF and IMF) in the Near-faults earthquakes designed with the Allowable Stress Design (ASD) and Load and Resistance Factor Design (LRFD) in a probabilistic framework. After the Static Push over (SPO), new Performance based earthquake engineering (PBEE) approach is incremental dynamic analysis (IDA) that can lead to the probabilistic judgment using fragility curves of the structure under the different types of ground motions at different levels of intensity. For the incremental dynamic analysis a large number of nonlinear time history analysis must be carried out. The evaluated steel moment frames are 4-story and 8-story frames. The nonlinear models of structures are constructed in the Perform-3D software to perform the nonlinear time history analysis. For the nonlinear modelling of beam element, the chord Rotation Model is used that proposed by FEMA and available in the Perform-3D software for the beam elements. This model predict the nonlinear behavior of element in the two end region that plastic hinge may be caused duo to the seismic load of earthquake. For the column elements, the fiber element method was employed. In this method, the cross-section of column element is subdivided into some spring elements. Each spring is subjected to axial load, given by the combination of axial force and bending moment acting on the section. This model sometimes is called multi-axial spring model (MS model). The fiber model represents a section at the structural member-end. This modelling can represent the axial-flexural interaction in the column element that their properties of nonlinear flexural bearing depends on its axial load in each time step. Near-field events due to their pulse-like effect are in the spotlight in the last decay. To evaluate their effects on the steel structures that located in the seismic areas of Iran, a number of near-field earthquakes are used in the probabilistic assessment. In the IDA curves, the roof drift is used as Damage Measure (DM) and the Spectral Pseudo-Acceleration of the first mode of the structure with 5% modal damping ( ) is used as Intensity Measure (IM). Also in the probabilistic fragility curves, the direct method is used. It means that the IM is used directly in the fragility curve. To predict the probabilistic function for the different level of performance of structures, the lognormal distribution was used. The study results show that the structures designed by the ASD method have a better seismic performance than the LRFD frames specially in the performance level of Life Safety (LS) and Collapse Prevention (CP). It can be concluded from comparison of the median of collapse functions. For example for the special moment frame (8-story structure), the use of ASD design (instead of LRFD design) leads to a 11% increase in the median of fragility function in the Life Safety (LS) level and 10% increase in the Collapse Prevention (CP) level.

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One of the applications of composite materials in the oil and gas industry is to repair worn metal pipelines. Calculating the strain energy release rate of the first failure mode is an important criterion for testing the bond strength and predicting the failure of these types of structures. In this paper, the rate of strain energy release during crack growth in bonding a composite patch to a steel substrate is investigated. In this regard, using the theory of elastic beam first, a new method is proposed to calculate the thickness of the metal and composite for Unlike Double Cantilever Beam (UDCB). This is due to the fact that the standard for experimental test procedure of strain energy release rate (ASTM-D5528) is for symmetric double cantilever beams. In this study, samples are fabricated from composite consisting of unidirectional fiberglass/ epoxy resin with harder in the upper and steel in the lower half of the beam. After sample fabrication, the strain energy release rate of UDCB and Asymmetric Unlike Double Cantilever Beam (AUDCB) are calculated experimentally. In addition, for the separation of first and second failure modes in symmetric and asymmetric samples, finite element simulation based on the virtual crack closure technique is presented. This analysis is to qualify the accuracy of the proposed equation for the thickness of unlike beams to achieve the first failure pure mode of symmetric samples. Also, it calculates the contribution of the first and second modes of failure in the strain energy release rate of AUDCB samples.

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History of past earthquakes and the destruction caused by them show that irregular structures have the vulnerability potential more than other structures. Reinforced concrete (RC) walls are commonly used as the primary lateral-force-resisting system for tall buildings, although for buildings over 49 m (160 ft), IBC 2006 requires use of a dual system. Use of nonlinear response history analysis (NRHA) coupled with peer-review has become a common way to assess the expected performance of tall buildings at various hazard levels to avoid the use of a backup Special Moment Frame for tall buildings employing structural walls. Modeling of the load versus deformation behavior of reinforced concrete walls and coupling beams is essential to accurately predict important response quantities for NRHA. The design of tall buildings essentially involves a conceptual design, approximate analysis, preliminary design and optimization, to safely carry gravity and lateral loads. New developments of tall buildings of ever-growing heights have been continuously taking place worldwide. Consequently, many innovations in structural systems have merged. The design criteria are strength, serviceability, stability and human comfort. The strength is satisfied by limit stresses, while serviceability is satisfied by drift limits in the range of H/500 to H/1000. Stability is satisfied by sufficient factor of safety against buckling and P-Delta effects. The factor of safety is around 1.67 to 1.92. The human comfort aspects are satisfied by accelerations in the range of 10 to 25 milli-g, where g=acceleration due to gravity. The aim of the structural engineer is to arrive at suitable structural schemes, to satisfy these criteria, and assess their structural weights in weight/unit area in square feet or square meters. This initiates structural drawings and specifications to enable construction engineers to proceed with fabrication and erection operations. The weight of steel is often a parameter the architects and construction managers are looking for from the structural engineer. This includes the weights of floor system, girders, braces and columns. The premium for wind is optimized to yield drifts in the range of H/500, where H is the height of the tall building. In this paper, the seismic behavior of steel frames with reinforced concrete core in the duplex and common high rise building are investigated. In this research, linear analysis under 3 kind of earthquake loading (equivalent static, spectral dynamic and dynamic time history) and wind load on structures with 20, 40 and 60 stories have been accomplished and different parameters, such as structure’s base shear and effect of increasing height on seismic behavior have been discussed. Based on results, making structures duplex, causes changes in modal shapes and mass participation percentage of modes. For this reason, there is no change in linear static methods and wind load of common structures and duplex structures response but it has seen changes in structure’s response for 12 far and near earthquake records. In some earthquakes, base shear has been increased maximum 32 percent of common structure’s base shear and also there is no change in base shear in some of them. In some structures, base shear has been decreased maximum 16 percent of common structure’s base shear.
 

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Using a Tuned Mass Damper (TMD) in a structure, is a reasonable solution for absorbing its movements caused by external forces. However, when designing a TMD on the grounds of passive control, it is a challenging task as this device can be tuned once and for a specified range of frequency. Employing more than one TMD is another option; although this will lead to higher cost and might increase the base shear of the structure. In this paper, to provide a wide range of frequency and mode shapes in the analysis, nine types of steel structures are designed, having the story number of 4, 8, and 12, respectively, and then subjected to 22 acceleration records of FEMA-P695; These records, are a suitable choice for generating statistical results as they provide a wide range of magnitudes. Three of these structures are uncontrolled, and the remaining are equipped with a TMD on their roof, being of 0.5% and 1% mass ratio and considering the first mode frequency for the TMD design. The design of the TMDs is carried out via Den Hartog's formula.
Using incremental dynamic analysis (IDA), fragility curves are created with constant 0.1g steps for PGA intensity measure. In addition, for considering the uncertainties in the performance of the TMD and the structure due to the changes in frequency, a 10% error is applied for the first mode frequency in the nonlinear design of the structures. The maximum drift ratio is used as a damage measure due to its simplicity and comprehensive coverage. Multiple earthquake recordings and their statistical characteristics, such as mean, median, 16%, and 84% of the recorded amplitudes and their more robust components, are utilized to examine the IDA curves to eliminate any ambiguity about structure response. This paper presents its novelty by applying a statistical method for choosing the mass ratio of TMD, considering the possible real-world quantities for this parameter and a wide range of frequencies for the excitations; therefore, limiting the TMD stroke. Subsequently, verifying the linear and non-linear behavior of the model used in this paper is carried out by modeling a 40-story steel structure equipped with a TMD situated on its roof and tuned based on its first mode under the Kobe Earthquake. Furthermore, the displacement response of the 4, 8, and 12-story structures, being equipped with a single TMD of 0.5% and 1% mass ratio, respectively, are compared to their uncontrolled state by exposing them to the Landers earthquake.
Results show that using TMD reduces the maximum drift ratio of the structures. Considering the first 16% of the acceleration records, as expected, a 12-story steel structure equipped with a TMD of 1% mass ratio on the roof, presents the best results of maximum drift improvement ratio of 2.54%. Moreover, for reducing computational effort, another alternative is applying a limited number of earthquakes to the structure. By using the median for the duration and PGAs of all FEMA-P695 data to estimate this earthquake record, the maximum drift improvement ratio is then 1.61% for the twelve-story structure resulting in decent numbers compared to the first method. Moreover, all types of the 4, 8, and 12-story structures (uncontrolled, controlled with a TMD of 0.5% mass ratio, and controlled with a TMD of 1% mass ratio) were subjected to the Kobe earthquake, and their average roof displacements were compared. Among these three types of structures, the 12-story structure was recorded to have the highest rate of maximum roof displacement compared to its uncontrolled state, being 3.47%.

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Base isolation is an effective technology for reducing seismic damage to structural and non-structural components as well as building contents, allowing buildings to maintain their function during and after a rare, high-intensity earthquake. This makes it an ideal seismic response correction system for importance buildings. The main advantage of isolated structures is that seismic responses can be easily and effectively reduced by prolonging the period and increasing damping. Therefore, the natural period of the structure isolated from the base is longer. In this paper, a new energy balance method is used to design a lead rubber bearing (LRB) isolator. Energy balance method is an analysis method to evaluate seismic resistance based on the balance of seismic energy input to buildings due to ground motion and energy absorbed by the building. In other words, the energy balance method is a response prediction method to approximate the seismic response of buildings isolated from the foundation. This method is effective for determining the relationship between ground motion, seismic isolation period and the effect of reducing the reaction of dampers. In this method, the specifications of the isolation system, including stiffness, yield shear force and viscous damping ratio, are adjusted in such a way that the maximum shear and maximum displacement in the isolation system do not exceed a certain value determined by the designer. This allows the designer to limit the maximum displacement at the isolation level to a certain amount when there is a constraint on the supply of separation distance around the building and the isolated level. Also, by limiting the maximum shear of the isolators, it is possible to use the base isolation system for retrofitting the existing structures that have a certain lateral capacity.
This design method was first proposed and used in Japan. This method has been recently proposed in the Iranian regulations (which is being drafted) and has not been used much in this country so far. Its advantages include no need for trial and error in the design process, the possibility of designing a rubber and frictional type of seismic isolator, the possibility of using a viscous or hysteretic damper, or a combination of both at the isolator installation site. To evaluate the accuracy of this method, three 5, 10 and 15-story steel structures with an ordinary concentric braced frames in both directions for clinic usage have been modeled and under eight near and far-field earthquakes in the by the nonlinear time-history analysis method have been analyzed. The results obtained from the time-history analysis are in good agreement with the estimated results of the energy balance method. The error percentage related to the displacement of isolator compared to the value assumed at the beginning of the design for 5, 10 and 15-story structures is 3.4%, 2.57% and 2.12%, respectively. Also, the percentages of error related to the maximum shear of isolator compared to the value obtained from the performance curve for 5, 10 and 15-story structures are 11.08%, 12.61% and 13.98%, respectively.
 

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Seismic waves of structural vibrations propagating through the soil and transmitting to other structures, and the effect this has on seismic performance, have recently come up due to the result of recent ground movements originating in soft soil zones like Mexico City. In regions with densely built structures, this vibration may have a significant impact on structural responses. The purpose of this research is to evaluate the seismic performance of a single structure on soil (Soil-Structure Interaction, or SSI) vs. that of a pair of similar structures with differing soil conditions (Structure-Soil-Structure Interaction, or SSSI). Recent research suggests that damage risks may increase due to the SSSI impacts. The studied structure is a three-dimensional, six-story steel building with a foundationally sound moment and braced frames lateral force resisting system. To account for the non-linear behavior shown by SSSI and SSI models, a three-dimensional steel structure is presented in OpenSEES. For simulating the soil easily under the foundations and between structures, the nonlinear Beam-on-Nonlinear-Winkler-Foundation (BNWF) model is employed. There is a meter of space between structures. Therefore impact between buildings is prohibited. The SSSI and SSI systems are examined using 11 horizontal components. Ground motion magnitudes ranges from Mw = 5.0 to Mw = 8.5, soil shear velocity varies from Vs30=185 m/s to Vs30=365 m/s, and distance from faults goes from 10 km to 50 km. The two orthogonal horizontal components of selected seismic ground motion stimulate the system. Inter-story drift ratio, roof displacement, and plastic hinge rotations of structural elements are among the reactions of importance. In the SSSI and SSI models, the Park-Ang damage index is utilized to calculate the local and global damage index. This damage indicator is divided into two categories: deformation and energy-based indices. The current study's findings show that the SSSI model increases the roof displacement response by up to 58%. When the SSI and SSSI cases are compared, it is discovered that the SSSI case increases the inter-story drift ratio by 118% in the moment frame and by 53% in the braced frame. In addition to this, it is shown that,  in general, a second structure may have a significant impact on the frequency amplitude of a system that is adjacent to it. According to the data, the amplitude of the power spectrum density in the SSSI model is more than 44.6% higher than that which is found in the SSI model. According to the findings, the damage index predicted by SSSI models is 32% greater than that predicted by SSI models. It is important to keep in mind that constructing a second building next to an existing one is often counterproductive and raises the possibility of damage occurring in both of the structures. As a result of the findings, it is clear that more study into SSSI phenomena and their influence on structural seismic risk is necessary. This is because it has been shown that adjacent buildings may significantly increase a structure's vulnerability to earthquakes.

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In the seismic active areas, strong ground motions usually consist of the numerous successive shocks (Foreshock-mainshock or mainshock-aftershock), which have the significant potential to increase the structural response and cumulative damage. This phenomenon (as called seismic sequence) can affect on the behavior of structures, control the seismic performace of buildings. Multiple earthquakes which have been recorded in all parts of the world are proven that the structures located in the mentioned areas are not only experienced a single event, but also they withstand a series of shocks. Due to the high importance of consecutive earthquakes, application of buckling restrained braces (BRB) and shape memory alloy (SMA) materials as smart materials in engineering sciences in the past decades, this paper tries to evaluate the seismic performance of steel frames equipped with buckling restrained brace by determination of the optimal percentage of shape memory alloy under successive earthquakes. Because SMA has unique advantages and characteristics such as no need to replace after an earthquake, high resistance to corrosion and fatigue, the ability to absorb high energy, the ability to return to the original state by applying temperature, tolerating strain up to about 10% without leaving residual strain after an earthquake, and tolerating multiple cycles of loading and unloading, various applications can be found separately and combined in controlling the behavior of structures. It should be noted that despite the high damage potential of successive earthquakes, they are neglected in the seismic codes and design earthquake is still proposed without successive shocks.
Hence, the acceptance of new methods for improving the seismic performance of structures under consecutive shocks seems necessary by the engineering community. Therefore, in this regard, 4 and 7 story steel frames with diagonal buckling restrained braces representing short and mid rise structures were designed based on Iranian codes in ETABS software and then implemented in OpenSees software. After selecting the reference model, the performance of the studied models is verified for the linear and non-linear region through comparison of periods and pushover curve of reference and implemented model. In the following, different percentages of shape memory alloys including 20, 40, 60, 80 and 100% for the 4 story steel frames and 5, 10, 15, 20 and 25% for 7 story steel structure has been considered. The studied models are analyzed with/without shape memory alloys under seismic scenarios with and without seismic sequence in Opensees software. For this purpose, critical successive shocks are selected based on effective peak acceleration (EPA) from PEER center. For compatibility aspects between the seismic analysis and seismic design, the selected records should be scaled by designing spectrum for each fundamental period of studied structure in order to have identical spectral acceleration. The results of nonlinear dynamic analysis show that with the increase in the percentage of shape memory alloy in the 4 story steel frame, the response ratio of steel frames under single and consecutive earthquakes increased, but in the 7 story steel frame, it almost decreased, and this reduction is better felt in the higher stories under the single earthquake. Finally, the optimal percentage of shape memory alloy among the selected percentages in the present study is suggested to be 20% for 4 story steel frame and 15% for 7 story steel frame.