Nonlinear static & dynamic analysis

The present work concerns the numerical investigation of reinforced concrete frame buildings containing masonry infill panel under seismic loading that are widely used even in high seismicity areas. In seismic zones, these frames with masonry infill panels are generally considered as higher earthquake risk buildings. As a result there is a growing need to evaluate their level of seismic performance. The numerical modelling of infilled frames structures is a complex task, as they exhibit highly nonlinear inelastic behaviour, due to the interaction of the masonry infill panel and the surrounding frame. The available modelling approaches for masonry infill can be grouped into two principal types; Micro models and Macro models. A two dimensional model of the structure is used to carry out non-linear static analysis. Beams and columns are modelled as non-linear with lumped plasticity where the hinges are concentrated at both ends of the beams and the columns. This study is based on structures with design and detailing characteristics typical of Algerian construction model. In this regard, a non-linear pushover analysis has been conducted on three considered structures, of two, four and eight stories. Each structure is analysed as a bare frame and with two different infill configurations (totally infilled, and partially infilled). The main results that can be obtained from a pushover analysis are the capacity curves and the distribution of plastic hinges in structures. The addition of infill walls results in an increase in both the rigidity and strength of the structures. The results indicate that the presence of non-structural masonry infills can significantly modify the seismic response of reinforced concrete "frames". The initial rigidity and strength of the fully filled frame are considerably improved and the patterns of the hinges are influenced by structural elements type depending on the dynamic characteristics of the structures.

The present work concerns a numerical study of the behavior of reinforced masonry (RM) structures under seismic loading. These structures are made of small hollow elements with reinforcements embedded in the horizontal joints. They were dimensioned according to the rules and codes commonly used. They are subject to vertical loads due to their own weight, and to horizontal loads due to seismic forces introduced by the accelerograms. The software used is the non-linear analysis program Drain2D, based on the finite element method, where the shear panel element was introduced. A series of calculations was performed on a number of structures at different levels, excited by three major accelerograms (El Centro, Cherchell, and Kobe). Throughout the study, our main interest is to evaluate the behaviour factor, the ductility, and the failure mode of these structures while increasing the intensity of earthquakes introduced. The results of this present study indicate that the average values of the behaviour factor and the global ductility are of the order of q≈μ≈3.00. The reinforced masonry structures studied have been broken by interstage displacement. The results given by the study are comparable to those given in the literature and in Eurocode 8. The behavior of reinforced masonry under a seismic load is similar to the behavior of reinforced concrete; it is a ductile behavior that allows the dissipation of the energy transmitted by the earthquake. These numerical studies confirm and complete the experimental work carried out by other researchers.

Control algorithms are an essential part of effective semi-active vibration control systems used for the protection of large structures under dynamic loading. Adaptive control algorithms, which are data-driven methods, have recently been developed to replace model-based control algorithms, thus improving efficiency. The dynamic parameters of semi-actively controlled infrastructures will change after significant vibration loading. As a result, these structures require real-time, effective control actions in response to changing conditions, which classical controllers are unable to provide. To improve the efficiency of the semi-active controller, the optimal control algorithm was developed in this study. The algorithm is the integration of the replicator dynamics with an improved non-dominated sorting genetic algorithm (NSGA), which is NSGA-II. The optimal parameters of replicator dynamics (total resources, growth rate, and fitness function), which represent the behavior of the actuators, were obtained through a multi-objective optimization process. The new control system was then used to reduce the vibrations of the isolated highway bridge, which is equipped with semi-active control devices known as MR dampers. Moreover, the current study improved the performance of the structural control system with minimum energy consumption by assigning a specific growth rate to each control device. In order to reduce the vibrations of the highway bridge, the results show that the performance of the optimal replicator controller is better than the performance of the classical control algorithms.

This paper presents a statistical correlation analysis of peak ground acceleration to peak ground velocity ratio (A/V) and other ground motion intensity measures (IMs) for Iran’s data. A/V is an important parameter that can significantly affect nonlinear structural responses. Findings from this study provide beneficial insights into selecting suitable parameters for characterizing earthquake ground motions. The studied database included 2053 strong ground motion records with the moment magnitude from 4.5 to 7.8 MW, rupture distance from 1 to 600 km, and average shear wave velocity from 155 to 1594 m/s. Correlation coefficients between A/V and several IMs were obtained for near-field and far-field records at three A/V levels, low A/V, middle A/V, and high A/V. Regression analyses for predicting A/V from the IMs were also conducted for near-field and far-field records. The results showed that the mean period (Tm) has the highest correlation with A/V at all A/V levels and for both far-field and near-field earthquakes compared to the other IMs. Therefore, this parameter can be employed for record selection as a frequency content-based parameter. Finally, current results showed that the accuracy of the Artificial Neural Network (ANN) models are more than the regression models for predicting A/V.

Recent developments in performance-based seismic design and assessment approaches have emphasised the importance of properly assessing and limiting the residual (permanent) deformations, typically sustained by a structure after a seismic event, even when designed according to current code provisions. Recent investigations have led to a proposed Direct Displacement-Based Design (DDBD) approach which includes an explicit consideration of the expected residual deformations accounting for 2-dimensional and MDOF effects. Having estimated the possible residual deformations in a structure, it remains to implement specific design features to reduce them to an acceptable level. Previous studies have identified post-yield stiffness as being critical to residual deformation behaviour, therefore a series of simple approaches are proposed to increase this element and system parameter. These methods do not utilise re-centring post-tensioned technology. First, the effects of changes in material stress-strain behaviour and section design in the primary seismic-resisting system are considered, and then the design and introduction of a secondary elastic frame to act in parallel with the primary system is demonstrated. Using moment-curvature and non-linear time-history analyses, the proposed approaches are shown to be effective at achieving their intended goal of residual deformation reduction.

The seismic response of special moment-resisting frames (SMRF), buckling restrained braced (BRB) frames and self-centering energy dissipating (SCED) braced frames is compared when used in building structures of 2 to 12 stories in height. The study involves pushover analysis as well as 2D and 3D nonlinear time history analysis for two ground motion hazard levels. The SCED and BRB braced frames generally experienced similar peak interstory drifts. The SMRF system had larger interstory drifts than both braced frames, especially for the shortest structures. The SCED system exhibited a more uniform distribution of the drift demand along the building height and was less prone to the biasing of the response in one direction due to P-Delta effects. The SCED braced frames also had significantly smaller residual lateral deformations. The two braced frame systems experienced similar interstory drift demand when used in torsional irregular structures.

Recent developments in performance-based seismic design and assessment approaches have emphasised the importance of properly assessing and limiting the residual (permanent) deformations, typically sustained by a structure after a seismic event, even when designed according to current code provisions. Recent investigations have led to a proposed Direct Displacement-Based Design (DDBD) approach which includes an explicit consideration of the expected residual deformations accounting for 2-dimensional and MDOF effects. Having estimated the possible residual deformations in a structure, it remains to implement specific design features to reduce them to an acceptable level. Previous studies have identified post-yield stiffness as being critical to residual deformation behaviour, therefore a series of simple approaches are proposed to increase this element and system parameter. These methods do not utilise re-centring post-tensioned technology. First, the effects of changes in material st...

Recent developments in performance-based seismic design and assessment approaches have emphasised the importance of properly assessing and limiting the residual (permanent) deformations, typically sustained by a structure after a seismic event, even when designed according to current code provisions. Recent investigations have led to a proposed Direct Displacement-Based Design (DDBD) approach which includes an explicit consideration of the expected residual deformations accounting for 2-dimensional and MDOF effects. Having estimated the possible residual deformations in a structure, it remains to implement specific design features to reduce them to an acceptable level. Previous studies have identified post-yield stiffness as being critical to residual deformation behaviour, therefore a series of simple approaches are proposed to increase this element and system parameter. These methods do not utilise re-centring post-tensioned technology. First, the effects of changes in material stress-strain behaviour and section design in the primary seismic-resisting system are considered, and then the design and introduction of a secondary elastic frame to act in parallel with the primary system is demonstrated. Using moment-curvature and non-linear time-history analyses, the proposed approaches are shown to be effective at achieving their intended goal of residual deformation reduction.

Origins and development of 3D-BASIS (3-Dimensional BASe Isolated Structures) was initially envisioned by the need for an efficient tool for nonlinear dynamic analysis of three-dimensional base isolated structures, particularly in solving the highly nonlinear bidirectional stick-slip hysteretic response of a collection of sliding isolation bearings and the resulting response of the superstructure, as this was not available at that time. The primary challenge was to solve the stick-slip behavior of friction bearings-modeled using a differential equation (Bouc-Wen Model) due to its efficiency in representing constant Coulomb friction or variable velocity depended friction by using a very small yield displacement during the stick phase resulting in very high tangential stiffness followed by a very small tangential stiffness during the sliding phase-and the resulting stiff differential equations. A challenge that is compounded when biaxial-friction is modeled, wherein even the traditional method of using Gear's method to solve stiff differential equations breaks down-a problem that was vexing the research team at University at Buffalo trying to solve the problem at that time. The answer was the development of the novel pseudo-force solution algorithm along with a semi-implicit Runge-Kutta method to solve the difficult problem. The efficient solution procedure is needed primarily for the nonlinear isolation system consisting of (1) sliding and/or elastomeric bearings, (2) fluid dampers, (3) other energy dissipation devices, while the superstructure is represented by three dimensional superstructure model appropriately condensed (where only master nodes at the center of mass of the floor are retained). This chapter describes the origins, development of 3D-BASIS and its impact.

Iran is one of the most seismically active regions in the world. A major challenge of identifying all high-risk buildings should be embarked in large cities of Iran such as Tehran. Obviously, collapse is the most important performance level of seismic risk assessment of these buildings. This paper focuses on developing a new methodology on the basis of modern seismic guidelines for seismic collapse risk assessment of the existing mid -rise reinforced concrete buildings in Tehran. A new methodology is introduced briefly. Then, it has been implemented for two types of midrise buildings having 7 and 10 stories buildings they are all engineered buildings constructed in Tehran during past 25 years. Two archetypes which made up of ensembles of them were selected for demonstrating the proposed methodology. The archetype buildings are selected in a way that flexural failure mode under seismic loads would be dominant for them. Several nonlinear analyses were performed to evaluate structural responses of this archetype model under moderate and severe earthquakes. All nonlinear analytical models were implemented in the OpenSees ( ) structural analysis software. A simulation model for components and structural system capable of capturing flexural collapse modes are applied. Meanwhile, a lumped plasticity model, developed by Ibarra et al. (2003), is used to detect severe deterioration that precipitates sideway collapse. A number of parameters, as calibrated in FEMA-P695, are used in this model. A collapse drift matrix is developed for each archetype to distinguish between the partial collapse of each story and the conventional collapse detection through IDA curves. The collapse drift matrix affects the collapse capacity of the reinforced concrete buildings strongly. Under the framework of this new methodology, an attempt is made to achieve reliable results for the studied archetype structures. Also, the existing limitations and uncertainties of this proposed methodology are summarized and discussed.

The research compares the structural analyses discussed by mathematical modeling with those addressed by structural approaches. It discusses Eigenvalue Analysis, Static Pushover Analysis, Static Adaptive Pushover Analysis, Static Time-History Analysis, Dynamic Time-History Analysis, Incremental Dynamic Analysis (IDA), Response Spectrum Analysis (RSA), and Buckling Analysis. Structural limitations, brief or extensive information about the structure, as well as the result of the output approach, have a major impact on the selection of the structural analysis method. In this research, by examining each analytical method, their different characteristics are discussed.

In seismic performance based design context, engineers are faced to a difficult task to estimate the response of soil-structure interaction (SSI) systems. To accomplish this task successfully, all sources of random and epistemic uncertainties should be taken into account. However, the uncertain parameters have not the same influence on the model response; a sensitivity analysis is therefore required. This article treats the two following aspects: the first one is to perform a sensitivity analysis on all the parameters in order to study their influence on the structural response. The uncertainties effect is done by studying the sensitivity of the maximum structure displacement towards the used materials parameters variation (fc’, εc0, εcu, Es, fsy, α, εsu, A, ξ) and soil properties (ξg, ν) on the SSI seismic response. This study consists of determining, quantifying and analyzing how the outputs of the N2-SSI model are affected by input variables fluctuations. The second aspect is ana...

Tall and highrise buildings located in seismically vulnerable zones usually need to go through seismic evaluation to check its resilience against cyclic loading produced due to surface waves created by earthquakes. Large seismic waves create undulations in soils which drastically reduces the strength of foundations and ordinary moment resisting frames and the following aftershocks accelerate crack propagation of structural systems and dynamic overloading, leading to a heavy toll on lives. To protect buildings in dynamically active zones, moment resisting frames need seismic detailing alongside seismic testing. These paper deals with nonlinear dynamic analysis(pushover techniques) on a highrise building located in Dhaka city which was originally designed as a simple moment resisting frame, and necessary optimization of structural elements to improve its function against dynamic loading using the help from the BNBC code and the ETABS software.

Since, in the case of plan-eccentric, externally-braced, high-rack storage structures made of steel, damage to the central part of the structure can cause damage to the stored goods, and thus higher earthquakeinduced costs, an investigation has been performed into the seismic performance of such structures. An actual structure was analysed both as a fixed base variant, and as a base-isolated variant. The extended N2 method (pushover analysis) was used, and the results obtained were compared with selected results obtained by nonlinear-dynamic analysis. The response of several different mass-asymmetric structural variants, corresponding to different occupancy levels of the structure, was analysed, and the results obtained are presented as floor plan projection envelopes of the top, relative and base displacements, as well as the storey drifts. An interesting result obtained in the research was that asymmetry can increase the damage in the supporting structure on the flexible side, and that the central part of the rack structure remains in the elastic region only when the eccentricity is small. In fact, from the seismic point of view, full occupancy is not the most critical condition, but rather lower occupancy, which could cause eccentricities ranging up to 10% or 15% of the larger floor plan dimension; this could lead to damage propagation in some of the columns. The application of base isolation has a positive effect on the management of seismic performance, even in the case of higher levels of occupancy and larger mass eccentricities. It is pointed out that an eccentricity of 5%, which is prescribed in Eurocode 8, might not be sufficient in such structural types, and that similar concerns could be present in other types of industrial structures with a similar ratio between live and dead loads.

This article provides a new finite-element procedure based on Reddy's third-order shear deformation plate theory (TSDT) to establish the motion equation of functionally graded porous (FGP) sandwich plates resting on Kerr foundation (KF). Although Reddy's TSDT is attractive, it cannot be exploited as expected in finite-element analysis due to the difficulties in satisfying the zero shear stress boundary condition. In this study, the proposed element has four nodes, each with seven degrees of freedom (DOF). The performance of this element is confirmed by conducting various examples, showing its accuracy and range of applications. Then, some studies are performed to present the effects of input parameters on the vibration of FGP sandwich plates resting on KF.

In rotordynamic simulations, rolling element bearing waviness is often accounted using nonlinear models that are solved with a numerical integration scheme in time domain. This approach generates accurate system response, but the method is limited in terms of computational efficiency. This study proposes two novel methods for solution of the responses caused by the bearing waviness excitation in frequency domain, and compares the result with a previously developed, time domain based numerical simulation. The first method known as Base Excitation Method (BEM) considers the waviness as base excitation whereas the second method, known as Bearing Kinematics Augmented Base Excitation Method (BKA-BEM), utilizes a four degree of freedom, quasi-static model to include the bearing kinematics and refine the base excitations due to waviness. The methods are validated with a test case, in which measured low order waviness components of the bearing inner ring roundness profile were used as source for excitation. The accuracy and robustness of the proposed methods in calculating the subcritical harmonic response frequencies and amplitudes are examined for different roundness profiles. The results show that the proposed methods performed relatively well compared to previously developed, time domain solution based numerical model and experimental results. Furthermore, the frequency domain solutions significantly reduce the computational time which makes them easily applicable to simulation-based transfer learning, iterative inverse problems and optimization solutions.

This work investigates the response of typical RC beam under the column removal scenario and their potential resistance against progressive collapse. This paper analyses different span buildings with typical beam depth. Three different spans were chosen for this study such as 3, 4, 6 m and typical beam depth is 400 mm, obtained from L/D =15 in the case of 6m span. This study focuses buildings with aspect ratio L/B=B/H=L/H=1. Column removal locations are corner, intermediate and perimeter as per GSA and DoD. Load combination and beam reinforcement followed as per progressive collapse guidelines. Nonlinear dynamic analysis carried out in ETABS 17.0.1 software. The conducted study shows that maximum displacement is 50 mm, occurred in 6 m span at corner column removal scenario. Maximum DCR value was obtained for the 6m span building, intermediate ground column removal case.

This paper presents selected problems connected with modelling of multi-layer pavements. Multi-layer pavement models, which utilize solutions such as the one of Boussinesq, Burmister, Kogan, Odemark and others, contain many simplifications, which has a significant influence on the estimated real value of stress, strain, deflection as well as on the coefficient of pavement layers interaction. On the basis of the experiments carried out, layered- pavement models and solutions to them are presented, which can be used mainly in the diagnostics of bearing capacity. The estimation of bearing capacity is conducted on the basis of full time data obtained with the falling weight deflectograph. Moreover, the conclusions implicated by the above mentioned analysis are significant in the design and operation of road and airfield pavements. They pertain not only to the influence of modulus and thickness of particular layers but also to pavement layer interaction, Poisson's coefficient and oth...

This paper quantifies the impact of using different ground motion selection methods to evaluate the seismic performance of steel special moment frames. Two methods are investigated: a "traditional" approach, herein referred to as the Pacific Earthquake Engineering Research (PEER) method, and a newer approach known as the conditional mean spectrum (CMS) method. Amongst other differences, the PEER method uses the risk-based maximum considered earthquake (MCER) as the target spectrum, while the CMS method uses the conditional mean spectrum. Two special moment frames (4-and 8-story) designed in accordance with ASCE/SEI 7-10, are used to represent archetype steel frame buildings on the West Coast of the United States. The seismic performance of these frames are assessed with the nonlinear dynamic procedure prescribed in ASCE/SEI 41-13, using ground motions selected and scaled in accordance with both methods. The performance of the buildings is evaluated at the Collapse Prevention (CP) performance level for a far-field site located in Los Angeles, CA. The two ground motion selection methods lead to different structural response predictions, where the ground motions selected and scaled using CMS can result in a smaller dispersion of the output parameters. These results provide motivation for building standards, such as ASCE/SEI 41, to advocate implementing the CMS method as an alternative ground motions selection approach. The results also shed light on the influence of the ground motion selection method in the design of new buildings using the performance-based seismic design methodology.

The assessment of seismic performance of buildings under future earthquakes is becoming an important problem in earthquake engineering. Some important buildings are considerably old and therefore their strengths and ductilities are less than strength and ductility demands. Such buildings must be strengthened to resist future earthquakes. At first the structural model must be developed and then based on seismic hazard and seismic risk analysis or code quantities, the design (or control) parameters are determined. Other step is defining the damage indices. Then the nonlinear dynamic analysis is carried out. Finally based on numerical results one can determine the amount and how of strengthening. In this paper some damage indices are reviewed and then a formulation is presented for considering the importance of columns and lower stories failure. As an example an existing building is analyzed.

This paper presents the time history response of a sandwich beam with a porous core subjected to two moving harmonic loads with opposite directions. In the modelling, the beam is combined of two isotropic face sheets and a porous core with symmetric porosity distribution. The quasi-3D shear deformation beam theory in conjunction with Hamilton's variational principle is utilized to set up the governing equations of motion. The Navier solution is used to obtain the displacement field. The accuracy of the study is validated by comparing with existing results in the literature for specific cases. Effects of the velocity and excitation frequency of the moving loads on the deflection-time history are investigated and discussed. Numerical results reveal that in the case of the doublemoving harmonic loads in the antiphase, the resonance phenomenon cannot occur when the excitation frequency approaches the natural frequency of the beam.

The ability to predict epileptic seizures well prior to their clinical onset provides promise for new diagnostic applications and novel approaches to seizure control. Several groups of investigators have reported that it may be possible to predict seizures based on the quantitative analysis of EEG signal characteristics. The objective of this chapter is first to report an automated seizure warning algorithm, and second to compare its performance with other, theoretically sound, statistical algorithms. The proposed automated seizure prediction algorithm (ASPA) consists

The solution of nonlinear dynamic equilibrium equations using mode superposition and substructuring is studied. The objective is to design schemes that in some analyses can significantly decrease the computational effort involved when compared to a complete direct integration solution. Specific schemes for mode superposition analysis and substructuring are proposed. These techniques have been implemented in ADINA. The results of a few sample analyses are presented and recommendations are given on the use of these procedures in practical analysis.

A range of lightly-reinforced, poorly-confined RC columns were assessed for seismic safety based on the limit state of collapse in projected earthquake scenarios representative of the average level of seismicity in Australia. The hysteresis model for each of the columns analysed were first calibrated against results from cyclic tests and push over analyses up to the limit of gravity collapse. Inelastic time history analyses employing 40 spectrum compatible accelerograms on class C sites (AS 1170.4) were then conducted on the calibrated models. Fragility curves have also been constructed in accordance with results from incremental dynamic analyses. Results presented provide the basis for realistic seismic collapse assessment of the poorly confined reinforced concrete columns. Importantly, the size effects phenomenon has been revealed in this study.

Incremental Dynamic Analysis (IDA) is a powerful method for evaluating the seismic performance of structural systems. When undertaking IDA, ground motion records are scaled in accordance with a certain seismic intensity level up until the limit of collapse of the structure is reached. Peak ground acceleration (PGA) is often used as intensity measure (IM) for scaling purposes whilst peak ground velocity and response spectral accelerations can also be used as IM parameters. One of the challenges with the IDA methodology is that the performance (IDA) curve obtained for a structural system is non-unique meaning that it can be sensitive to changes in the frequency properties of the input excitations. Thus, there is a practice of holding the frequency content of the excitation unchanged (or constrained to a model design spectrum) when applying the scaling. The shortcomings with this modelling approach is that real conditions can be misrepresented given that frequency contents of the earth...

Nowadays, many buildings around the world exhibit height irregularities. Given that higher vibration modes can significantly influence the responses of irregular frames, it is essential to investigate the seismic behavior of these structures. In this research, making use of nonlinear dynamic analysis, the seismic behavior of irregular moment resisting frames is assessed. Nonlinear dynamic analysis, due to considering the dynamic characteristics and nonlinear behavior of the structure, is one of the most accurate methods for seismic evaluation of structures. Despite its advantages, the complexity, high computational demands, and time-consuming nature of nonlinear dynamic analysis have led to limited attention from engineers in the design process of conventional structures. In recent years, several efforts have been made to enhance this method, including the development of the Endurance Time method. In this method, acceleration functions are generated using optimization algorithms, reducing the need for excessive use of accelerograms. For this purpose, 3-and 9-story frames with different types of height irregularities are considered. These frames are analyzed using accelerations derived from the Endurance Time method. A comparison of the results indicates that setbacks in building frames significantly influence the dynamic responses. Notably, the difference in drift values between the story where the setback occurs and the others is relatively large. This highlights the need for special attention to the irregularities during the design process of such frames. Cite this article: Izadpanah, Mehdi. (2024). Application of the endurance time method in the seismic assessment of momentresisting reinforced concrete frames with setbacks. Advanced Modeling in Civil Engineering, 1(2), 1-12.

The primary goal of major building codes is to protect life safety by designing buildings that have sufficient
integrity and strength to resist collapse in severe earthquakes. The secondary objective of these codes is to control
property damage and maintain function in more moderate but frequent events.
Performance is about going through a process and explicitly looking at the outcome, which is well defined, without
overly focusing on or conforming to implicit standards and predefined procedures. Of course, there are going to be
standards and guidelines and ways to do performance-based design (PBD) itself, but the end focus is on
performance and not literal or generic conformance and that is the basic difference between conventional and
performance-based design. When we do conventional design, our objective is to satisfy the design code. We may
lose the sense of what the structure's performance would be if we do satisfy or do not satisfy the code.
Performance-based design method is a direct design method starting from the pre-quantified performance objectives,
in which plastic design is performed to detail the frame members and connections in order to achieve the intended
yield mechanism and behavior.
In this study we performed the nonlinear static pushover analysis to find the performance of the three building
configurations (i.e. Bare Frame, Bare frame with Peripheral middle walls and Bare frame with corner shear walls)
structures using ETAB 21, taking ASCE 41-17 and FEMA guidelines to find and compare the performance of the
structures. Firstly, the details design of all three buildings has been performed as per IS-456, 2000 and IS-1893 2016
using ETAB 21 software and later their performance is calculated using nonlinear static push over analysis taking
deflection control criteria using ETABs. The building performance is compared in terms of Push over curve, Base
shear, Deflection, Performance point, Stage and number of Plastic hinges formed together with the storey drifts.

Nowadays, many buildings around the world exhibit height irregularities. Given that higher vibration modes can significantly influence the responses of irregular frames, it is essential to investigate the seismic behavior of these structures. In this research, making use of nonlinear dynamic analysis, the seismic behavior of irregular moment resisting frames is assessed. Nonlinear dynamic analysis, due to considering the dynamic characteristics and nonlinear behavior of the structure, is one of the most accurate methods for seismic evaluation of structures. Despite its advantages, the complexity, high computational demands, and time-consuming nature of nonlinear dynamic analysis have led to limited attention from engineers in the design process of conventional structures. In recent years, several efforts have been made to enhance this method, including the development of the Endurance Time method. In this method, acceleration functions are generated using optimization algorithms, reducing the need for excessive use of accelerograms. For this purpose, 3-and 9-story frames with different types of height irregularities are considered. These frames are analyzed using accelerations derived from the Endurance Time method. A comparison of the results indicates that setbacks in building frames significantly influence the dynamic responses. Notably, the difference in drift values between the story where the setback occurs and the others is relatively large. This highlights the need for special attention to the irregularities during the design process of such frames. Cite this article: Izadpanah, Mehdi. (2024). Application of the endurance time method in the seismic assessment of momentresisting reinforced concrete frames with setbacks. Advanced Modeling in Civil Engineering, 1(2), 1-12.

In this paper, the effects of seismic wave propagation characteristics on two 10-story studied structures with Bundled-Tube and Hexagrid systems are investigated based on conducting nonlinear time history analysis. For this purpose, the columns and diagonal members of the studied structures are simulated using finite element meshes composed of single-element to five-element configurations and modeled within the SAP2000 software environment. The identical lateral stiffness parameter has been considered for both studied structures. The ensemble of the selected three-component earthquake records includes six near-field strong ground motions containing forward-directivity effects. One of the most important features of near-fault strong ground motions is the emergence of pulse-like structures in the related time history. The presence of high-amplitude spikes and large long-period pulses in the time history of strong near-field records, significantly affects the seismic response parameters of structures. The corresponding results of this research subject indicate minimal changes in the computed modal characteristics via an increase in the number of finite elements used to simulate the main structural members.
The Bundled-Tube resistant skeleton exhibits behavioral characteristics similar to those of an integrated cantilever structure and has a very high lateral stiffness. Moreover, the Hexagrid structural system benefits from both efficiency and geometric aesthetics in its configuration. The most prominent feature of this structural system is its application in various geometric arrangements and the effective reduction in weight and material consumption in the resistant skeleton. In this study, the structures under investigation are 10-story skeletal systems with regularity in both plan and elevation. The design of the resistant structural system is based on the requirements in the fourth edition of the Iranian building design code for earthquake resistance (i.e. Standard 2800) as well as the sixth and tenth chapters of the Iranian national building regulations. Additionally, the use of finite element meshes with varying lengths would include the effects related to higher frequencies in the spectral content of earthquake records. This view is also related to the range of changes in force results and structural response parameters subjected to strong near-field earthquake records.

Los ingresos de los municipios en el pais estan constituidos especialmente por sus ingresos propios, que son los obtenidos por los impuestos directos e indirectos, contribuciones y creditos y, por las transferencias de la Nacion, de los 1.125 municipios que conforman el pais podria decirse que el 95% de ellos subsisten por las transferencias de la Nacion, fenomeno que se debe a la falta de gestion de los administradores al momento del cobro de sus impuestos y contribuciones, lo que finalmente se refleja en el escaso desarrollo de sus territorios y en el bajo indice de inversion social en su poblacion. Si los municipios y su poblacion comprendieran la importancia del recaudo y pago de los impuestos y contribuciones seguramente tendriamos municipios mas desarrollados y mejores niveles de vida de sus habitantes, es por eso que basados en lo comportamientos de los presupuestos historicos del municipio se pretende, con este trabajo de implementacion del marco fiscal de mediano plazo peri...

This research was conducted on residential buildings with discontinuous walls from the ground floor to the upper floors due to the ground floor being used as parking areas or lobbies, commonly referred to as piloti buildings. Piloti buildings are susceptible to experiencing soft stories because the ground floor is more flexible than the floors above. The presence of the wall on the upper floor designed as confined masonry could detect a soft story. Many studies have been conducted on confined masonry models, but they still need to provide conclusive results and are still quite challenging to apply to complex buildings. This study used a layered shell SAP2000 model to model confined masonry and validated it with experimental test results. The research findings indicate that considering the presence of walls can detect soft story irregularities. Soft story evaluations suggest that the columns and beams on the ground floor should be enlarged to prevent structural collapse. Pushover analysis indicates that confined masonry construction has better stiffness and strength than open frame construction but has lower ductility. Additionally, confined masonry structures are considered more affordable regarding their reinforcement and concrete requirements. These findings can be a foundation for further development in designing confined masonry constructions in Indonesia.

Seismic design codes are prepared for prevent the life lost, damage control and economic design; to do this, generally combination of the strength and ductility are used. The main different between seismic design code and seismic strength is that the design is preformed in the elastic region while the strength is calculated based on plastic behavior, ductility, and the location of plastic hinges. Based on the research in this paper, the pseudo static qualifies for all responses such as displacement, drift and story shears. However, based on the 2800 standard the dynamic analysis is necessary for regular structures with height more than 50m, therefore it must be investigated that the structures designed using the modal dynamic analysis is able to resist earthquakes scaled to 0.35g.In this paper 15, 20 and 25 story 2D-moment resisting frames which are designed based on design spectrum of 2800 Iranian code are studied. The nonlinear acceleration time history analyses are preformed and the story displacements and drifts are extracted and are compared with code allowable amounts. The story ductility demands are also calculated and compared with the capability of story ductility. The local failure of the structural members is controlled. Finally, the damage level of the structures is investigated.

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A numerical model for simulating the nonlinear dynamic response of natural draught cooling towers to wind loading is introduced. Geometrical and physical nonlinearities are considered in the F.E. modeling of the doubly-curved, thin shell structure. An original simulation procedure of the artificial wind loading as used, generating directly the multi-correlated field of the (stochastic) time series of the external pressures. The effective correlation structure of the fluctuating pressure is imposed from the experimental data obtained by wind tunnel tests. Some preliminary analyses, carried out for checking the performance and reliability of the model, as e finally reported.

The scope of this work is the creation of a numerical FE model of an existing prestressed post-tensioned RC box girder ductile ravine bridge and its updating, based on identified modal characteristics (eigenfrequencies). The challenge for this task rose from the fact that the identified modal characteristics were not adequate for the use of one of the advanced automated model updating methods that are available. In particular, the only usable parameters that were identified were some natural frequencies and their corresponding mode types but not eigenvectors. Safely assuming modern building conditions, the absence of localized structural damage and the linear behavior during the identification measurements, an empirical manual updating procedure is implemented for updating standard key parameters of the FE model. During the updating procedure the identified quantities are used to define the models uncertain parameters such as moduli of elasticity and boundary conditions, whilst robu...

Performance seismic evaluation is an important topic in earthquake engineering. In this regard, several methods have previously been developed and used. The main objective of present research is to evaluate two methods including "Capacity Spectrum Method (CSM)" and "Improved Capacity Spectrum Method (ICSM)" in determination of seismic performance of concrete frames. For this purpose, several sample frames are subjected to several different earthquake records, seismic performance of them are evaluated using these two methods. It was demonstrated that CSM and ICSM methods underestimate displacement at seismic performance level. Based on the numerical results of this study, it was concluded that the ICSM method is more accurate than the CSM Method.

Incremental Dynamic Analysis (IDA) is a powerful method for evaluating the seismic performance of structural systems. When undertaking IDA, ground motion records are scaled in accordance with a certain seismic intensity level up until the limit of collapse of the structure is reached. Peak ground acceleration (PGA) is often used as intensity measure (IM) for scaling purposes whilst peak ground velocity and response spectral accelerations can also be used as IM parameters. One of the challenges with the IDA methodology is that the performance (IDA) curve obtained for a structural system is non-unique meaning that it can be sensitive to changes in the frequency properties of the input excitations. Thus, there is a practice of holding the frequency content of the excitation unchanged (or constrained to a model design spectrum) when applying the scaling. The shortcomings with this modelling approach is that real conditions can be misrepresented given that frequency contents of the earth...

Post earthquake studies show that the primary cause of reinforced concrete building collapse during earthquakes is the loss of vertical-load-carrying capacity in critical building components leading to cascading vertical collapse, rather than loss of lateral-load capacity. In cast-in-place beam-column frames, the most common cause of collapse is failure of columns, beam-column joints, or both. This study emphasizes failure of columns using data from laboratory studies. Failure models are incorporated in nonlinear dynamic analysis software, enabling complete dynamic simulations of building response including component failure and progression of collapse. This approach enables more realistic simulation of building collapse than is possible using simplified assessment procedures, and provides insight into the conditions that cause collapse and the variability of collapse as a function of input ground motions.

Buckling-restrained braces (BRBs) are often employed for the seismic retrofit of existing systems and the design of new systems given their significant contribution in terms of stiffness and added damping. However, since BRBs are characterized by a low lateral post-elastic stiffness, their use may lead to excessive residual deformations that may jeopardize the reparability of the building. Moreover, accumulation of plastic deformations in the BRBs may endanger the capability of withstanding multiple earthquakes and aftershocks. The objective of this paper is to provide insight into the performance and residual capacity of dual systems made of BRB frames coupled with moment-resisting frames. This study considers a simplified single degree of freedom model which permits to investigate a wide range of configurations. A non-dimensional formulation of the equation of motion is introduced, the statistic of the normalized peak and residual displacements and cumulative ductility of the syst...

In this paper, the radial and axial vibrations of rigid shaft supported ball bearings are studied. In the analytical formulation the contacts between the balls and the races are considered as nonlinear springs, whose stiffness are obtained by using the Hertzian elastic contact deformation theory. The implicit type numerical integration technique Newmark-β with Newton-Raphson method is used to solve the nonlinear differential equations iteratively. The effect on vibrations of varying preload and the number of balls in the bearings is investigated for prefect bearings. For perfect bearings, vibrations occur at the ball passage frequency. The amplitudes of these vibrations are shown to be considerably reduced if the preload and number of balls are correctly selected. All results are presented in the form of Fast Fourier Transformations (FFT).

In this work, a three-dimensional dynamic simulation model for cylindrical roller bearings is developed based on multi-body-simulation software SIMPACK and programming language FORTRAN. The aim of this work is to build a universal program to calculate the dynamic behavior of cylindrical roller bearings. This simulation model integrates major part of the functionalities according to the state of the art of existing programs which are: the slice model, the mutual influences of neighboring slices, the basic three-dimensional model, the calculation of lubricant film thickness and damping forces, the radial clearance, the roller-pocket clearance, the centrifugal forces and the hysteresis damping forces. The extended functionalities in this work can be summarized as follows: 1) Roller-pocket contact stiffness is taken into account and calculated with the help of finite element analysis. 2) The three types of cage guidance are modeled in details which are roller guidance, inner ring guidan...

Since the late 19th century, with scientific and technological advancements and the increasing population, the construction of tall structures to better utilize urban spaces has flourished. During this period, the close interaction between structure and architecture has led to the invention of innovative structural systems such as the hexagrid structural system. This system has attracted significant attention from structural engineers and architects due to its structural efficiency and appealing appearance. In this study, the seismic behavior of Bundled-Tube and Hexagrid structures in 10-story structures with symmetrical and regular plan have investigated. Therefore, a set of strong ground motion records with forward directivity effects was selected for nonlinear time history analysis. The evaluation of the analytical results and findings of this research has been primarily focused on the variations in three response parameters: relative velocity response, absolute acceleration, and relative lateral displacement (drift) of the stories. It was observed that the Hexagrid is more flexible compared to the Bundled-Tube structure. Additionally, the absolute acceleration response of upper stories and relative displacement of stories in the Hexagrid structure increase.

Given the continuous advancement of science and technology, as well as the aging of many structures, the need for upgrading old structures and utilizing new technologies in new structures is keenly felt. One suitable solution to achieve these goals is the use of energy dissipation devices in buildings, among which Buckling Restrained Braces (BRB) are included. This study focuses on evaluating the seismic performance of a moment-resisting frame with buckling-restrained braces and comparing it with Concentric braced frame. Initially, this paper presents the results of a series of nonlinear time history dynamic analysis, where criteria such as relative lateral displacement, residual lateral displacement at each story, and plastic energy dissipation are assessed. Based on both criteria of relative lateral displacement at each story and plastic energy dissipation, it has been observed that the seismic performance of structures with buckling-restrained braces is better than the structures with moment-resisting frames and concentric braced frames. The structure with a moment-resisting frame has performed better in terms of residual lateral displacement at each story compared to other structures, and to solve this problem, the ability to replace damaged braces in buckling-restrained frames can be utilized.

Vehicle-pavement interaction was studied using the Mathematical Model of Pavement Performance (MMOPP). With MMOPP a length of flexible road is first generated on the computer. Values of layer thicknesses, elastic moduli, plastic parameters, and so forth are generated at points spaced 0.3 m apart in such a way that the pattern of variation is similar to that observed on real pavements. The pavement is then loaded using a quarter car model, and the dynamic load is calculated at each point. The permanent deformation of each layer and the structural deterioration of the asphalt layer resulting from the loads are likewise calculated for each point. The next time increment is then considered, changing the materials characteristics in accordance with climatic changes, applying the loads of that increment, and so on. MMOPP was used on two sections from the AASHO Road Test. The traffic was extended to 20 years, and the effects of varying vehicle characteristics such as spring constant of the...

Using the general purpose finite element package ABAQUS, a 3-D finite element model representing 20 storey buildings were first built in this paper to perform the progressive collapse analysis. Shell elements and beam elements were used to simulate the whole building incorporating non-linear material characteristics and non-linear geometric behavior. The modeling techniques were described in detail. Numerical results are compared with the experimental data and good agreement is obtained. Using this model, the structural behavior of the building under the sudden loss of columns for different structural systems and different scenarios of column removal were assessed in detail. The models accurately displayed the overall behavior of the 20 storey buildings under the sudden loss of columns, which provided important information for the additional design guidance on progressive collapse.

Bangladesh lies well within a vigorous seismic zone and is liable to earthquakes. to see earthquake forces on a structure, static analysis has gained popularity within the country and also in many other countries thanks to the simplicity of the strategy. This concerns the utilization of a longtime and tested code so on make sure the safety of the structure and its occupants against the natural hazard. This paper aims at the comparison of varied provisions for earthquake analysis as given in building codes of various countries. Bangladesh National Building Code, 1993 (BNBC-93) has been studied and compared with National Building code of India 1983 (NBCI-83), Building Standard Law of Japan and International Classification for Standards, Nepal Building Code (NBC-1994). The study revealed that the developed countries have increased the factor of safety against earthquake by suggesting higher values of base shear. A five-story residential building has taken for the analysis considering the same live load and the Dead load where the Variation of the base shear on height, Variation of Building code coefficient and the comparison according to the codes has shown that which code is really efficient for Bangladesh or Indian subcontinent. The graph has shown that which code is efficient for the Subcontinent. But BNBC is that the least conservative as compared to other codes and practices. this might have serious implications just in case of a serious earthquake in Bangladesh or Indian subcontinent.