Seismic Input Energy Research Articles

Influence of pier height and ground motion parameters on seismic response and energy dissipation of isolated railway bridges

The overlap between high-speed railways and earthquake areas makes it necessary to implement isolation design for railway bridges. At present, the variation of seismic energy of railway bridges with structural and ground motion parameters is not clear. In this paper, the finite element models of railway bridges with different pier heights are established and verified by shaking table tests. Then, the nonlinear time history analysis of isolated and non-isolated models is carried out, and the differences in seismic response and energy dissipation between the two models under different parameters are compared. Finally, the isolation effect of hyperbolic friction pendulum bearing (HFPB) is evaluated by using the efficacy coefficient method. Results demonstrate that HFPB can not only reduce the seismic response of the girder and the pier, but also effectively reduce the seismic input energy, structural damping energy, and pier hysteretic energy. In addition, HFPB has a better seismic isolation effect when pier height is 3–15 m, site characteristic period is 0.25–0.45 s, and earthquake PGA is 0.2–0.5 g.

Energy response analysis and seismic isolation strategy optimization of high-speed railway bridge-track system under earthquake action

The formulation and optimization of a seismic isolation strategy is crucial for improving the seismic performance of high-speed railway bridge-track systems (HSRBTS) under earthquake action. In line with this proposition, therefore, this paper studies the seismic isolation strategy optimization of HSRBTS based on an energy response analysis. More specifically, the energy dissipation distribution of common and isolation HSRBTS under different earthquake strength levels is analyzed. The results show that when the peak ground acceleration (PGA) is greater than 0.3g, the seismic input energy of isolation HSRBTS is smaller than common HSRBTS. With the increase of PGA, the total proportion of hysteretic energy dissipation increases while the proportion of damping energy dissipation decreases in common HSRBTS, with the opposite being observed in isolation HSRBTS. Bearings and piers are the main hysteretic energy dissipation components for HSRBTS. Thus, in view of the energy dissipation requirements and structural characteristics of HSRBTS, this paper proposes an energy-based optimization principle. Under the existing isolation HSRBTS, the seismic isolation strategy is optimized to achieve a uniform distribution in hysteretic energy dissipation, while the effectiveness of the optimized seismic isolation strategy is submitted to further verification.

Development and experimental study of a novel rotational metallic damper

As passive control technology advances and building forms become increasingly diversified, traditional axial and shear dampers may no longer meet diverse structural application requirements. This paper introduces a novel rotational metallic damper, i.e. rotational steel rod damper (RSRD), as an alternative engineering solution. The RSRD comprises three steel plates rotating around a central pin and four low yield point steel rods as energy dissipators. The input seismic energy can be dissipated in the form of plastic rotation of the RSRD. Initially, the structural form, working mechanism, and design approach of the RSRD are presented. Subsequent cyclic quasi-static tests on two RSRD specimens under varied loading protocols demonstrated satisfactory energy dissipation capacity, with an equivalent viscous damping ratio exceeding 0.47. The cyclic behavior, rotational strength, and cumulative plastic deformation capacity are discussed following the tests. A finite element (FE) analysis on the RSRD using ABAQUS is conducted to further investigate its performance. A comparison between the hysteretic behavior and failure mode of tested and simulated results is presented to validate the FE model. Additionally, two new structural forms, with linear and arc-shaped weakening on the steel rod, are simulated and compared with the original. FE results indicate that the arc-shaped weakening of the steel rod effectively avoids plastic strain concentration, showcasing superior low-cycle-fatigue performance. Finally, nonlinear time history analyses on two RC frames, with and without RSRD, reveal that structural and non-structural damage can be controlled under the maximum considered earthquake (MCE) by utilizing RSRDs.

Assessment and measurement of ground motion risk levels for structures isolated by double concave friction pendulum system

Determining the risk level of ground motions (GM) for structures is crucial for their damage control and resilience enhancement, while the assessment and measurement criteria of GM risk levels for structures isolated by double concave friction pendulum system (DCFPS) remain unclear. Through statistical analysis of the response distribution of DCFPS with various design parameters under 1013 GM records, this study determines an energy dissipation efficacy of 99 %, a floor velocity of 0.35 m/s, a floor velocity of 0.60 m/s, and the displacement capacity of DCFPS as the response criteria for assessing four performance states of efficacy, habitability, functionality, and safety, respectively. In addition, the value of GM intensity in PGA, PGV, PGD, and the equivalent velocity of seismic input energy (VE) for measuring the four GM risk levels corresponding to the four performance states are obtained. Furthermore, a classification of GMs based on earthquake magnitude and fault distance is proposed according to their risk to DCFPS. It is found that the intensity value of each GM risk level varies for different design parameters of DCFPS but fluctuate within a small range, however, great differences exist when using different intensity measures (IM) in classifying GM risk levels. Therefore, based on the correlation between IMs and DCFPS responses, the conservatism of PGA, PGV, PGD and VE in assessing the risk of GMs for DCFPS are evaluated.

Pseudo‐dynamic testing, repairability, and resilience assessment of a large‐scale steel structure equipped with self‐centering column bases

AbstractRecent destructive seismic events have underlined the need for increasing research efforts devoted to the development of innovative seismic‐resilient structures able to reduce seismic‐induced direct and indirect losses. Regarding steel Moment Resisting Frames (MRFs), the inclusion of Friction Devices (FDs) in Beam‐to‐Column Joints (BCJs) has emerged as an effective solution to dissipate the seismic input energy while ensuring a damage‐free behavior. Additionally, recent studies have demonstrated the benefits of implementing similar damage‐free solutions for Column Bases (CBs). In this context, the authors have recently experimentally investigated a Self‐Centering CB (SC‐CB) aimed at residual drift reduction. Previous experimental tests only focused on the response of isolated SC‐CBs under cyclic loads. Conversely, the present paper advances the research through an experimental campaign on a large‐scale steel structure equipped with the proposed SC‐CBs, providing valuable insights into the global structural response and improved repairability. A set of eight Pseudo‐Dynamic (PsD) tests were conducted considering different records and configurations of the structure. The experimental results highlighted the effectiveness of the SC‐CBs in minimizing the residual interstory drifts and protecting the first‐story columns from damage, thus enhancing the structure's resilience. Moreover, the consecutive PsD tests allowed investigating the effectiveness of the reparation process in restoring the seismic performance of the ‘undamaged’ structure. An advanced numerical model was developed in OpenSees and validated against the global and component‐level experimental results. Incremental Dynamic Analyses were finally performed to investigate the influence of the SC‐CBs on the structure's seismic response while accounting for the record‐to‐record variability.

Investigating the seismic performance and developing the fragility curves of self-centering steel frames with augmented nonlinear viscous damping: A numerical simulation

This paper focuses on investigating the seismic performance of post-tensioned steel frames equipped with nonlinear viscous dampers. The aim is to increase the ductility and seismic energy dissipation capacity of these structures. Finite element (FE) models were created using the Abaqus software and validated against reference experimental data under cyclic loading. Two types of post-tensioned moment-resisting frames (PT-Frames) were developed: a conventional PT-Frame and a PT-Frame with two pairs of nonlinear viscous dampers acting as knee braces (each brace pair, contains two dampers connected in parallel, thus there are 4 dampers used in total). Various analyses, including modal analysis, cyclic loading, and incremental dynamic analysis (IDA), were conducted using earthquake records mentioned in FEMA P-695. Fragility curves were plotted based on the IDA results. The findings indicate that the augmented nonlinear viscous damping significantly increases the natural fundamental period of vibration in PT-Frames (133 % increase observed). It also enhances the absorption and dissipation of input seismic energy (800 % increase in cumulative dissipated seismic energy observed). Moreover, it reduces the probability of damage exceeding the damage index value for different performance levels (collapse prevention, life safety, and immediate occupancy) by average values of 115 %, 61.72 %, and 25.126 %, respectively. These improvements help mitigate damage to the structural components.

Comparison of Various Input Energy Spectra for the February 6th, 2023, Kahramanmaraş Earthquake Sequence

ABSTRACT This study aims to evaluate the success of various seismic input energy spectra equations in capturing the energy content of the ground motion records of the Türkiye earthquakes since the acceleration response spectra of some records exceeded the design spectra. Although most existing spectra had limited success, especially near the corner period, some recent equations yielded accurate results. Based on the obtained results, it is envisaged that the energy-based seismic design concept will have the maturity to be included in the next-generation seismic design codes as a reliable alternative to the current approaches.

Developing a Regression Model for Predicting the Seismic Input Energy of RC Buildings Using 6 February 2023 Kahramanmaraş Earthquake

Energy-based seismic analysis and structural design require understanding the seismic input energy response of reinforced concrete buildings subjected to strong ground motions. Thus, calculating and predicting input energies becomes of great importance. The object of this study is to introduce a regression model for predicting the seismic input energies of reinforced concrete buildings using the 6 February 2023 Kahramanmaraş earthquake. For this purpose, three regular 3, 6 and 9-storey residential reinforced concrete buildings are designed. Input energy response histories of buildings subjected to a set of horizontal acceleration histories of 67 stations of the February 6 Kahramanmaraş earthquake were obtained. Subsequently, the ground motion parameters were used to estimate the input energies. It was revealed that acceleration-based parameters generally had better consequences than velocity-based parameters in low periods, while the opposite was the case in high periods. This study proposed new equations in which multiple ground motion parameters are combined to better reflect input energy from a single parameter. As the height and period of the buildings increase, the multiple linear regression coefficient decreases and the estimation of input energy becomes difficult with the ground motion parameters.

Multi-objective seismic optimization and evaluation of core-damper-frame tall buildings considering SSI effect

To control the seismic response of the core-frame (CF) structure and attenuate the stress level of the core tube, a novel core-damper-frame (CDF) system is proposed by decoupling the perimeter frame and the central core with flexible damper connectors. In this way, the large inertia force of the perimeter frame cannot be fully transmitted to the core, and the stress of the core is mitigated. In the meantime, the damper connectors would absorb a considerable amount of seismic energy, protecting the perimeter frame as the relative displacement between the two subsystems (perimeter frame and core tube) occurs. By incorporating the soil-structure-interaction (SSI) and the filtered Gaussian white-noise excitation model, the "excitation-soil-core-damper-frame" augmented system is established. Combing the augmented system and the genetic algorithm, a stochastic optimization procedure of the CDF considering the SSI effect is proposed. The optimization aims to minimize a series of performance objectives including displacement, acceleration, shear force, and overturning moment of the CDF system. The conflicting relationships between the multiple objectives are discussed; the influence of the SSI effect and the excitation parameters are evaluated. From an illustrative 40-story CDF structural example, the system shows great superiority in controlling the higher mode vibrations, and could significantly reduce the peak core acceleration (by 54.44 %), frame acceleration (by 56.48 %), core drift (by 28.83 %), frame drift (by 39.28 %), core shear (by 83.67 %), and frame moment (by 22.41 %), as compared to its conventional CF counterpart. In special, over 50 % of the input seismic energy is dissipated by the damper connectors in the CDF system.

Probabilistic design procedure for steel moment resisting frames equipped with FREEDAM connections

In this work, the Theory of Plastic Mechanism Control (TPMC) is combined with a probabilistic method to account for the influence of random material variability. Reference is made to steel Moment Resisting Frames (MRFs) equipped with FREEDAM connections. FREEDAM connections are beam-to-column connections equipped with friction dampers to dissipate the seismic input energy. TPMC is used to guarantee that in case of destructive seismic events the structural members such as beams and columns remain undamaged. To this scope, the structure is designed to assure a collapse mechanism characterized by the activation of all the friction dampers of the beam ends and the formation of plastic hinges at the base of the first storey columns only. From the probabilistic point of view, the random uncertainties are given by the static friction coefficient of the contact surfaces and the preloading of the bolts of the friction dampers as well as the yielding resistance of the steel members. The failure domain is related to all the possible failure events, where the term “failure” concerns the development of an undesired mechanism different from the global one. Generally, the design conditions to prevent undesired collapse mechanisms are stochastic events within the framework of the kinematic theorem of plastic collapse. The limit state function corresponding to each event can be represented by a hyperplane in the space of random variables. Consequently, the failure domain is a surface resulting from the intersection of the hyperplanes corresponding to the limit states of each single failure event. Since dissipative zones (member ends or friction dampers) in the frame members are common to many different mechanisms, the single limit state functions are correlated. Therefore, the probability of failure can be evaluated by means of the Bimodal or Ditlevsen bounds by assuming that the failure events are located in series. The output of the work is a simple relationship which provides the overstrength factor of FREEDAM connections to be considered in the column design phase to account for random material variability thus assuring a given level of reliability in the application of TPMC.

Critical pseudo-double impulse analysis evaluating seismic energy input to reinforced concrete buildings with steel damper columns

Steel damper columns (SDCs) are energy-dissipating members that are suitable for reinforced concrete (RC) buildings and are often used for multistory housing. The evaluation of the peak deformation and hysteretic dissipated energy of such building structures is essential for the rational seismic design of RC buildings with SDCs. In a previous study, the authors proposed an energy-based prediction procedure for the peak and cumulative response of an RC frame building with SDCs. In this procedure, the accuracy of the equivalent velocity of the maximum momentary input energy (VΔE1*)–peak equivalent displacement (D1*max) relationship is essential for high quality predictions. In this article, the VΔE1*–D1*max relationships of RC moment-resisting frames with and without SDCs are investigated using a critical pseudo-double impulse (PDI) analysis based on a study by Takewaki and coauthors. The results show that the VΔE1*–D1*max relationship obtained from the critical PDI analysis agrees well with that calculated from the equations proposed in the previous study.

Experimental study on a cable-stayed bridge isolated with the combination of elastoplastic cables and fluid viscous dampers in the transverse direction

It is usually challenging to design an effective transverse isolation strategy that needs both large restoring force and large deformation capacity for cable-stayed bridges to meet the requirements under regular operation and earthquakes. The authors proposed a novel transverse isolation device that combines elastoplastic cables and fluid viscous dampers (FVDs) to address this challenge. The elastoplastic cables are adopted to control the relative displacements at the girder-pylon connections in the transverse direction under both regular operation and earthquakes. FVDs are responsible for dissipating input seismic energy. To further validate the effectiveness of the proposed isolation system under both far and near-fault ground motions, shake table tests were conducted for a cable-stayed bridge with a scale ratio of 1/20. Details of the scaled model for the isolated and fixed systems, including dimensions of the components, additional mass arrangement, instrumentations, and boundary conditions, are briefly described. Seismic responses are recorded for each test case, such as accelerations and displacements of the pylons and girder, hysteretic responses of the combined devices, and strain responses of the pylon rebars. The experimental results indicate that the transverse boundary conditions have significant effects on the seismic responses of the girder, and the high-mode content of ground motions mainly dominates the seismic responses of the pylons. In addition, the isolated system effectively reduces the seismic responses at the bottom of the pylons, and the effectiveness of the isolation is becoming more evident with an increase in the PGA of the ground motions.

Input Energy Reduction‐Oriented Control and Analytical Design of Inerter‐Enabled Isolators for Large‐Span Structures

Seismic isolation technologies for large‐span structures have rapidly developed alongside the popularization of the seismic resilience concept. To produce a high‐efficiency isolation technology with lower energy dissipation demands, this paper proposes a novel inerter‐enabled isolator (IeI) and a tailored input energy reduction‐oriented design method. The inerter‐based damper within the IeI is developed by combining the dashpot, tuning spring, and two inerters to facilitate the optimization of inerter distribution. Assuming the large‐span structure remains linear, the overall seismic input energy of the large‐span structure with IeIs and its allocation in the superstructure and additional damping are quantified using stochastic energy analysis. The advantages of the IeI over the conventional linear viscous damper (LVD) isolator are elucidated through dimensionless parametric analysis. Based on the results of parametric analysis, an input energy reduction‐oriented design method is proposed for the IeI, along with an easy‐to‐follow diagram that helps with preliminary design in practical applications. The effectiveness of the IeI and the proposed design method is validated through a design case study of a benchmark large‐span structure. The results demonstrate that the IeI reduces the seismic response of large‐span structures by simultaneously employing the input energy reduction effect of grounded inerters with the damping‐enhancing effect of inerter‐based dampers. The proposed design method effectively balances the performance of controlling the large‐span structure and the isolator displacement. Under consistent control performance and isolator displacement constraints, the IeI requires much less damping coefficient and energy dissipation capacity than the conventional LVD isolator. Moreover, leveraging the damping enhancement and input energy reduction effects, the IeI achieves comparable control performance to the conventional LVD isolator, even under stricter isolator displacement constraints.

Optimizing the seismic resilience performance of steel truss bridges by maximum energy dissipation via friction dampers

The primary aim of this study is to propose an innovative design methodology for optimizing the seismic resilience performance of steel truss bridges by dissipating the maximum input seismic energy. Maximum seismic energy dissipation is carried out by means of Pall friction dampers (PFDs), popularly categorized among passive energy-damping devices. PFDs distribute input seismic energy with a slip motion along with friction during an earthquake. For that, it is important to determine the optimal slip load value for the PFDs to start working before the structural elements reach the yield point. To determine the optimal slip load values of the PFDs under earthquake effects, the maximum seismic energy distribution is assured by nature-inspired Squirrel Search (SS) and Water Strider (WS) metaheuristic algorithms for steel truss bridges equipped with PFDs. Finally, steel truss bridges on which PFDs with optimal slip load values have been implemented are optimally designed to achieve the minimal structural weight while satisfying ASD-AISC Code of Practice requirements. In order to demonstrate the validity of the proposed design methodology, two design examples of 113-member and 465-member steel truss bridges steel are presented. The optimal slip loads attained with the SS and WS algorithms by conducting the proposed design methodology are 2.45% and 3.75% of the structural weight for the first design example and 2.64% and 2.63% of the structural weight for the second design example, respectively, which are much lower than those considered in practical applications. Moreover, the numerical results show that by 93.5% and 99.48% maximum distribution rates of input seismic energy are accomplished in the bridges. The results indicate that the proposed design methodology exhibit superior performance in optimizing the seismic resilience performance of steel truss bridges by maximum energy dissipation via friction dampers.

Seismic response analysis of super-high-rise building structures with three-layer isolation systems

This paper proposes a triple-layer isolation device based on the single-story isolation and double-layer isolation. By establishing dynamic equilibrium equations and conducting earthquake response comparative analyses on the same super-tall building structure using three different forms of isolation: single-story isolation, double-layer isolation, and triple-layer isolation, it is found that the triple-layer isolation device, which adds an isolation layer on the basis of the double-layer isolation device, exhibits many different characteristics in terms of its damping mechanism, seismic response rules, etc., due to the differences in the position and quantity of the isolation layer. Rare earthquakes are equivalent to ASCE maximum considered earthquake or annual occurrence probability of 2%. The research shows that, under rare earthquake conditions, the isolation effect of the triple-layer isolation device in the super-tall frame-shear structure is better than that of the single-story isolation and double-layer isolation devices. Particularly, as the number of floors increases, the triple-layer isolation device can significantly reduce the seismic isolation support tension and compression stresses, inter-story displacement, single-story shear force, overturning moment, and floor acceleration of the high-rise building structure, and concentrate the lateral displacement of the structure on the three isolation layers, dissipating most of the seismic input energy.

Damage distribution mechanism of common low-rise steel frame structures

In order to research the damage distribution mechanism of common low-rise steel frame structures under dynamic action, this paper took the column-to-beam strength ratio αi and column base form as the main parameters to research the seismic performance of common low-rise steel frames. To achieve this goal, 24 models of common low-rise steel frame structures were designed and analyzed by elasto-plastic time history analysis method; and the predominant periods of seismic waves are similar to the fundamental periods of these models. This paper focuses on the demand performance of each model such as the distribution of maximum inter-story drift ratio (MIDR), the deformation concentration rate of the first floor dR1, the ductility ratio μ and cumulative plastic ductility ratio η of the beams and columns; and clarifies the relationship between the damage mechanism of common low-rise steel frame structures and column-beam strength ratio αi and column base form in the first place. After that, to investigate the effect of each parameter on the structural energy dissipation, the plastic deformation energy distribution of each model was also studied in this paper. Finally, the mathematical equations of the seismic input energy and plastic deformation energy were studied, which can apply to common low-rise steel frame structures in the resonant state. It can provide a reference for engineers to choose the column-to-beam strength ratio αi and the column base form in the design of low-rise steel frame structures.

Quasi-static cyclic loading experiment and analysis of mechanical properties of the Sc-FSB

In order to improve the seismic performance of a continuous bridge, we propose to install self-centering functional separation bearings (Sc-FSB) between the fixed pier and the girder in the bridge. Following the design idea of separating functionalities, the Sc-FSB device is primarily composed of a sliding bearing to bear vertical load, a friction cable to carry horizontal seismic force and dissipate the seismic energy input into the superstructure, and self-centering springs to achieve post-earthquake self-centering effects. In this study, the Sc-FSB device's hysteretic model is established, and its theoretical formula is deduced. The quasi-static cyclic tests of 10 Sc-FSB device specimens were performed to verify their promising mechanical performances, in which we consider parameters of two friction cables with different diameters and three self-centering springs with different stiffnesses. The results show that the Sc-FSB device holds excellent characteristics of a typical friction damper, such as relatively stable outputs, good energy dissipation and deformation capacity under all working conditions, and its fatigue performance meets the requirements of typical specifications. In addition, several unique features of the Sc-FSB are identified as follows. The maximum damping force is independent of the loading frequency, and it increases with the displacement amplitude. The damping force is significantly affected by the pre-tension force of the friction cable and the number of winding coils, and as a result, the energy dissipation performance is promising. The stiffness and pre-tension force of the self-centering spring significantly improve the self-centering ability of the Sc-FSB device. The design of friction cable and self-centering spring effectively separates the functions of bearings. This study can serve as a foundation for the further study of Sc-FSB device and as a reference for the research of other similar friction dampers.

Experimental analysis on the structural seismic behavior of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting

The structural seismic performance of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting is analyzed, and the structural strength of steel frame-precast SRC infill wall with lateral force resisting is improved. The structural seismic performance optimization model of SRC lateral force resisting wall based on buckling restrained brace is proposed. Through the finite element simulation software, the seismic performance and response results of ordinary steel frames, buckling restrained braced steel frames and a relatively new type of sacrificial-energy dissipation braced steel frames under earthquake are compared and analyzed to demonstrate the applicability and performance advantages of sacrificial-energy dissipation braced steel frames in the steel frame braced structure system. Under the action of horizontal earthquake, the supporting members experience reciprocating axial tension and compression cycles, which dissipate a large amount of seismic energy input into the structure. Therefore, the buckling restraint support method can be used in the structure to improve the support strength. Under horizontal reciprocating load action of earthquake, the ability to consume seismic energy through self-hysteresis of the brace is poor. Experimental research shows that, the unbalanced force formed in the beam of the frame beam under seismic action will form a plastic hinge at the beam end at both ends of the frame beam. Especially when the brace is buckling unstable and the stiffness of the frame beam is small, the plastic hinge effect at the beam end is significant. This phenomenon may cause damage to the frame beam or even local floor subsidence. The buckling restraint support has a full hysteresis area under axial tension and compression, and its mechanical performance is excellent. It is obviously superior to ordinary steel bracing in energy dissipation capacity and seismic performance. It can accurately predict the bearing capacity of reinforced concrete under strong earthquake, and the energy dissipation distribution is more in line with the requirements of “energy seismic design method”.

Seismic Behavior of Arch Bridge Abutments under Sandy-Gravel Foundations with Different Grouting Depths: Insights from Shaking Table Tests

For arch bridges built on deep soil sites, significant seismic amplification effects were observed in the overlying soil layer from past earthquake events, and these effects can lead to more serious structural damage. Grouting-strengthening technology has recently been recommended as an innovative geotechnical method for strengthening soils to retain the seismic amplification phenomenon under strong ground motions, and it has exhibited advantages in improving the lateral resistance of soils. However, grouting reliability depends on the soil type, jet pressure, and engineering costs, and there has been little research on the differences in the natural period and seismic capacity caused by grouting behavior. To fill this research gap, based on a practical engineering prototype, shaking table tests were performed for semigrouting and all-grouting cases in sandy-gravel soil with a simple bridge abutment to investigate the difference in the seismic capacity of the two soil–foundation–abutment systems. The acceleration response difference between the grouting zone and the surrounding soil, characteristic periodic variation of the response spectrum of the soil and abutment, grouting depths, and seismic energy dissipation mechanism of the soil were analyzed. The results show that the acceleration amplification factor of the all-grouting foundation was smaller than that of the semigrouting foundation. However, the acceleration amplitude of the all-grouting foundation was larger owing to the higher seismic input energy. Significant differences in the lateral resistance mechanism between semigrouting and all-grouting foundations were observed. The grouting foundation realizes consistent acceleration and displacement through load transmission and soil–structure interaction mechanisms. The results demonstrate the suitability of soil thicknesses for significantly reducing the seismic demands of abutments and provide guidance for foundation treatment methods in relevant engineering projects.

Seismic Upgrading of Existing Steel Buildings Built on Soft Soil Using Passive Damping Systems

In regions prone to seismic activity, buildings constructed on soft soil pose a significant concern due to their inferior seismic performance. This situation often results in considerable structural damage, substantial economic loss, and increased risk to human life. To address this problem, this study focuses on the seismic retrofitting of steel moment-resisting frames using friction and metal-yielding dampers, taking into account the soil-structure interaction. The effectiveness of these retrofit methods was examined through a comprehensive non-linear time history analysis of three prototype structures subjected to a series of intense seismic events. The soil behavior was simulated using a non-linear Bouc-Wen hysteresis model. Various parameters, including lateral displacement, maximum drift ratio, the pattern of plastic hinge formation, base shear distribution, and dissipated hysteretic energy, were used to compare the performance of the two retrofit strategies. The findings from the non-linear analyses revealed that both retrofit methods markedly enhanced the safety and serviceability of the deficient buildings. The retrofitted structures exhibited notable reductions in residual displacements and inter-story drift compared to the original frame structures. In the original frame, primary structural elements absorbed a significant amount of the seismic input energy through deformation. However, in the retrofitted frames, dampers dissipated up to 90% of the total input energy. Additionally, integrating dampers into the original frames effectively transferred the non-linear response of the structural elements to the dampers.