Seismic Analysis Of Structures Research Articles

Multi-layered solid element for seismic analysis of rubber bearings considering stress continuity based on finite particle method

Rubber bearings are crucial components in seismic isolation systems to mitigate the damaging effects of earthquakes on structures. Rubber bearings generally consist of alternate layers of steel and rubber bonded together. Simplified two-point spring models omit this layered construction and have limitations in adaptability and programmability, while refined multiple solid models lead to substantial computational costs. This study presents an effective and efficient approach to simulate rubber bearings by using multi-layered solid element based on the finite particle method (FPM). The traditional “Zigzag” shape function is extended into the 3D situation to reflect the serrated deformation within the layered construction. Based on the simplified assumption of stress continuity, an iterative approach is presented for the deformation gradient to achieve the force continuity between layers in dynamic nonlinear scenarios. The multi-layered solid models for both natural rubber bearings (NRBs) and lead rubber bearings (LRBs) are proposed based on this element. The errors of the hysteresis curves of rubber bearings are below 3.1 % between the numerical results obtained by using the multi-layered solid model and the experimental results. The computational speedup ratio of the proposed multi-layered solid model is verified to be 19 relative to the refined multiple solid model. The proposed method is applied to a base-isolated frame structure to demonstrate its effectiveness in structural seismic analysis.

Review Paper on Seismic Assessment and Analysis of Typical RCC Structure for Retrofitting

Review Paper on Seismic Assessment and Analysis of Typical RCC Structure for Retrofitting

Seismic safety evaluation and resilient analysis of nuclear containment based on failure probability

This paper focuses on addressing seismic safety evaluation and resilience analysis of nuclear containment structure. Through the derivation of fragility formulas and the introduction of a new set of limit states (LSs), this paper accomplishes the fragility analysis and assesses failure probabilities comprehensively. Furthermore, safety evaluation and resilience analysis procedures, specifically for nuclear containment, are proposed alongside relevant determination criteria. In order to further improve the seismic performance of nuclear containment, the periodic foundation is analyzed. Theoretical formula is derived to determine the combination of 2 materials (concrete and rubber). Key findings include the safety demonstration of HUALONG 1 through probabilistic reliability analysis, the safety level (Level-I; basic integrity) and resilience level (Level-I). The effectiveness of periodic foundations is confirmed and supported by the average damping rates of concrete and liner strains, which can reach up to 6.154 % and 11.007 %, respectively. This research provides valuable insights for improving the seismic safety and resilience of containment, crucial for ensuring the integrity and functionality of this critical infrastructure system.

A partial decomposition cutting method with CF-discrepancy for points selection in stochastic seismic analysis of structures

The probability density evolution method is renowned for its effectiveness in conducting stochastic seismic response analyses of structures with uncertain parameters. Within this method, the points selection strategy, particularly in high-dimensional problems, is of paramount importance to achieving a balance between accuracy and efficiency. This paper proposes a novel point selection method designed to capture the probabilistic response of structural dynamic systems. The method starts by generating an initial uniform point set within a unit cube, using an improved number-theoretical method with a large number size. It then employs a partial decomposition cutting method to select a small number of samples from this initial uniform point set, which are subsequently scaled to the unit cube to serve as the representative points. These representative points are then transformed into the original random-variate space, and the corresponding assigned probabilities are computed accordingly. To enhance accuracy, a characteristic function-based discrepancy is proposed and applied to rearrange the representative points in the original random-variate space. The effectiveness of this method is demonstrated through two numerical examples, along with comparisons to results obtained using Monte Carlo Simulation and other comparable point sets.

Seismic Response Analysis of Composite Isolation Structures with Non-classical Damping

Seismic Response Analysis of Composite Isolation Structures with Non-classical Damping

Seismic Analysis of Structure with Self-centering Variable Friction Brace Based on Spectral Method

Seismic Analysis of Structure with Self-centering Variable Friction Brace Based on Spectral Method

Hierarchical and mixed uncertainty quantification for simulation-based structural seismic fragility analysis

Seismic fragility assessments (SFA) encompass significant uncertainties, including ground motions, materials, geometry, boundaries, and modeling, which impart inherent uncertainties to the fragility curve. Quantifying these uncertainties is essential for informed decision-making in earthquake disaster mitigation. This paper presents a hierarchical uncertainty quantification (UQ) framework for simulation-based SFA, which can address mixed aleatory and epistemic uncertainties. The framework comprises two levels: At Level 1, ground motion uncertainties are accounted for through record-to-record variation, while structural parameter uncertainties are captured using well-defined probability distributions. The quantification of uncertainty in seismic fragility is accomplished using mean and quantile fragility curves, representing the average outcome and the dispersion of structural fragility, respectively. Fuzziness is also introduced to enhance the objectivity of failure determination. Level 2 addresses uncertainties in the distribution hyper-parameters of structural variables through evidence theory, facilitating an understanding of their influence on the seismic fragility curve and quantifying uncertainty in mean and quantile fragility curves. This UQ framework builds upon the multivariate seismic fragility analysis method, integrating Kriging regression for seismic demand prediction and logistic regression for generating multivariate seismic fragility functions. The proposed framework is validated numerically on an existing three-span reinforced concrete continuous girder bridge, affirming its practical utility and reliability.

Surrogate models for seismic response analysis of flexible rocking structures

Surrogate models for seismic response analysis of flexible rocking structures

HORIZON PICKING ALGORITHM USING GLOBAL OPTIMIZATION AND COHERENCE MEASUREMENT IN POST-STACKED SEISMIC DATA

Accurate horizon recognition within post-stack seismic sections stands as a pivotal stride in seismic interpretation. Horizon-picking techniques wield importance in diverse seismic structural analyses and inversion methodologies. Despite encountering challenges like computational demands and time constraints, the past years have witnessed the evolution of numerous 2-D and 3-D methods. With the progress of modern computing, more resilient and efficient techniques, harnessing artificial intelligence, have come to the fore. In this context, we propose an innovative, cost-effective algorithm grounded in a global optimization framework. This algorithm amalgamates the Very Fast Simulated Annealing method with a set of stability parameters and coherence measurement of neighboring seismic traces, employed as the objective function. The search is executed on continuous and sequential clusters of seismic traces, with a focus on maximizing coherence amidst the presented events. We evaluate the algorithm's efficacy by applying it to two distinct input data sets—enveloped and non-enveloped seismic traces. The initial application pertains to the time-migrated Marmousi dataset, a synthetic marine dataset originating from a complex geological sedimentary basin situated in Angola, Africa. Subsequently, in the context of land seismic data, we apply the algorithm to depth-migrated field data extracted from a past survey conducted in the Tacutu basin in northern Brazil. Outcomes arising from the application to 2-D synthetic and field data sets underscore the method's viability as a compelling alternative for seismic horizon picking within the time or depth domain.#xD;

Optimal intensity measure for seismic performance assessment of shield tunnels in liquefiable and non-liquefiable soils

Relating the ground motion intensity measure (IM) and the structural engineering demand parameter is a crucial step in the performance-based earthquake engineering framework. This study investigates the selection of IM for development of probabilistic seismic demand model of urban shield tunnels subjected to earthquake ground motions in liquefiable and non-liquefiable soils. Nonlinear dynamic effective stress analyses are conducted to develop a database of the intensity measures and structural seismic responses exposed to ground shaking and soil liquefaction. Two advanced soil constitutive models (i.e., Pressure DependMultiYield03 and PressureIndependMultiYield for liquefiable and non-liquefiable soils, respectively) are employed to capture the nonlinear behavior. A suite of 23ground motion intensity measures is selected and assessed based on the evaluation criteria of correlation, efficiency, practicality and proficiency. Eventually, the multi-level fuzzy comprehensive evaluation method is employed to comprehensively consider the four evaluation criteria and establish the optimal ground motion IM suitable for probabilistic seismic demand analysis of shield tunnel structures. The obtained results show that the sustained maximum acceleration is the optimal IM for evaluating the structural seismic response, followed by the peak ground acceleration in both liquefiable and non-liquefiable soils. Peak pseudo velocity spectrum, displacement square integral and Housner spectral intensity are found to be not suitable for the probabilistic seismic demand analysis of shield tunnel structures.

Seismic fragility analysis of RC frame structures based on IDA analysis and machine learning

This study introduces a machine learning-based methodology designed to rapidly predict the seismic responses of reinforced concrete (RC) frame structures. The research focuses on three types of RC frame structures: low-rise, multi-story, and small high-rise buildings. Ground shaking records are selected according to the conditional mean spectrum (CMS). A sample database, constructed via Incremental Dynamic Analysis (IDA), facilitates the prediction of structural responses using ground shaking intensity and structural details as inputs. Concurrently, the study performs a feature importance analysis of the model. Machine learning algorithms, including integrated learning and neural networks, are utilized to predict the seismic responses of the RC frame structures. This methodology also assists in evaluating the seismic fragility of these structures. The results show that the discrepancy between the neural network-based seismic fragility assessments and the IDA results is minimal, indicating a high degree of accuracy in the proposed methodology. Among the characteristic parameters, Average Spectral Acceleration (AvgSa) is identified as the most significant. This methodology serves as a valuable tool for the rapid prediction of seismic responses in RC frame structures, demonstrating substantial practical value.

Simulation of pulse-like ground motions with directionality effect for the 2001 Mw 7.6 Bhuj, India earthquake and sensitivity analysis of uncertain model input parameters

Ground motions exhibiting pulse-like (PL) features present a distinct and significant threat to the structural integrity of constructed environments, due to intense pulse, large amplitude, and rapid energy release. The lack of recorded PL ground motion data in the Indian region presents a significant challenge for accurate seismic risk assessment of the built environment. In the absence of recorded PL ground motions, the generation of synthetic PL ground motions can provide earthquake acceleration time histories for seismic response analysis of structures and also to evaluate ground motion prediction equations (GMPEs). Within this framework, the modified stochastic finite-fault approach based on the dynamic corner frequency is used to generate the synthetic ground motions for the 2001 Gujarat earthquake. These artificially generated ground motions are validated using available peak ground acceleration data from thirteen stations. After validation, the ground motions are generated at locations equidistant from the fault in all four directions (i.e., east, west, north, south). The expected acceleration time histories at specific sites, the spatial distribution of ground motion characteristics, and the effect of site non-linearity are investigated. Based on the geographical positioning of sites for the 2001 event, it was observed that 65.15 % of ground motions on the western side, relative to the epicenter, exhibited PL characteristics, whereas 23.64 % of ground motions on the eastern side were observed to have PL properties. The effect of uncertainty in the model input parameters on the simulated ground motions is examined by performing a sensitivity analysis. The reliability and validity of the simulated ground motions are assessed by deriving an empirical equation and compared with the results obtained from available GMPEs for the region.

Simulation of Near-Fault Pulse-Like Ground Motion and Investigation of Seismic Response Characteristics in Subway Stations

ABSTRACT The availability of reasonable input ground motions is a prerequisite for investigating the seismic response of near-fault structures. Currently, realistic near-fault pulse-like seismic records are lacking internationally. Moreover, the existing records exhibit distinct regional characteristics, which hardly meet the demand for seismic analysis of various engineering structures. Collecting and analyzing the pulse-like seismic records, a linear attenuation expression is proposed in this study to describe the time-varying frequency amplitude decay over duration. On this basis, a new model compatible with horizontal and vertical components is developed for near-fault ground motions. The model parameters are estimated for 100 near-fault records and regressed against the prediction equations. The variability and correlation of the ground motion in two directions are analyzed through the residual correlation matrix. Finally, taking a subway station as the engineering background, the effects of velocity pulse and vertical seismic motions on the underground structures are addressed through simulated motions and realistic records. Compared with existing approaches, the proposed method not only aligns with the time-frequency distribution characteristics of near-fault ground motions but also considers the correlation between horizontal and vertical components. In addition, consistent with the results from recorded ground motions, the synthetic motions yield enlarged seismic responses of the underground structure, thereby guaranteeing analysis accuracy for the engineered structures subjected to pulse-like ground motions. The inclusion of vertical excitation prominently amplifies the vertical displacement of the slab under pulse-like ground motions.

Seismic mitigation analysis of base-isolated structure with sliding magnetic bearings considering local-site conditions

Base-isolation systems applied in building structures and infrastructures often suffer from damage even failure during strong earthquakes. The adaptability of isolators to local sites is a main concern for the robust design of base-isolation systems. In this study, seismic mitigation analysis of base-isolated structure with newly-developed sliding hydro-magnetic bearing (HMB) and sliding implant-magnetic bearing (IMB) considering local-site conditions is carried out. Extension of modeling of sliding magnetic bearings is first conducted based on the data of shaking-table tests of a reduced-scale base-isolated structure. To assess the instantaneous frequency for quantifying sliding magnetic bearings’ resisting force, the Hilbert–Huang transform (HHT) is applied. The influences of local-site conditions upon mitigation performance of the sliding magnetic bearings are then addressed, including far-field and near-field, ground motions with and without velocity pulses, and hard-soil and soft-soil. For comparison purposes, the seismic mitigation analysis of the base-isolated structure attached with lead rubber bearing (LRB) and curved surface slider (CSS) is carried out as well. Numerical results show that the sliding magnetic bearings outperform the state-of-the-art seismic isolators in both seismic mitigation and deformation constraint, and the IMB has excellent applicability for engineering since its perfect adaptability to local sites. However, the LRB cannot achieve the desired seismic mitigation under near-field pulse-like ground motions.

Seismic mitigation analysis of three-dimensional base-isolated nuclear structures with soil-dependent isolation system under extreme earthquakes

The Fukushima nuclear accident in March 2011 has raised more stringent requirements for the ability of nuclear power plants (NPPs) to withstand extreme disasters such as extreme earthquakes. To address this challenge, this study proposed a new hybrid multi-dimensional passive control system that combines three-dimensional base isolation and geotechnical seismic isolation. In this system, high-damper rubber bearings were employed to isolate horizontal seismic motions, whereas disc springs, accounting for frictional forces, were used to mitigate vertical seismic motions. Additionally, a geotechnical seismic isolation system arranged under the base mat was leveraged to further reduce the seismic response of the superstructure. Taking a large-scale reactor building in complex layered sites as an example, the effectiveness of the hybrid multi-dimensional isolation system was studied using a wave motion method. The research results indicate that when subjected to extreme earthquakes, hybrid multi-dimensional isolation exhibits superior isolation performance compared with three-dimensional base isolation, which can significantly reduce the three-dimensional dynamic response of nuclear structures without increasing the displacement of the isolation bearings. The proposed hybrid multi-dimensional isolation system offers an effective solution to the challenges faced by three-dimensional isolation systems, thereby enhancing the seismic resistance of nuclear structures against extreme earthquakes.

Seismic resistance analysis of a plywood house structure based on ABAQUS fracture mechanics

Plywood is a more affordable material for the residential construction industry due to its lower cost and easy availability. However, earthquakes are the biggest barrier for wood structures to stand for a long time, as the materials can easily deform or collapse when subjected to seismic forces. This paper aims to explore the performance of plywood structures during an active earthquake by conducting a series of tests and simulations. In this study, plywood property was explored in the four-point bending experiment to determine its stress-strain relationship, and the results were used to identify the materials young modulus, a key parameter for designing more resilient structures. In addition, a finite element model of a plywood house structure was developed in the ABAQUS application, and the seismic movements with five different velocity values were applied to determine the stress distribution and deflections of the structure. The results provide insights into the dynamic behavior of plywood structures under different seismic movements.

Research on the Value of Rayleigh Damping Parameter in Explicit and Implicit Integrals for Dynamic Analysis of Large Structures

Rayleigh damping is proportional to the combination of the structural mass matrix and stiffness matrix and is widely used in structural seismic analysis. The accuracy of seismic analysis of nuclear power structures directly depends on the value of the Rayleigh damping parameters. However, the stiffness component of Rayleigh damping is not included in the explicit integral, so the Rayleigh damping in the explicit and implicit integrals needs to be handled differently. LS-DYNA R11.1.0 software provides various calculation methods for the value of the Rayleigh damping parameter in the explicit integral. To investigate the influence of the value of the Rayleigh damping parameter in the explicit and implicit integrals on the results of the dynamic analysis of a nuclear power plant, the AP1000 nuclear island plant is taken as an example, and the explicit and implicit dynamic calculation are carried out respectively for the nuclear power plant, considering the soil–structure interaction. The results show that the Rayleigh damping parameter calculated by different methods in the explicit integral has a large influence on the results of seismic analysis of nuclear power plants. The mass component of Rayleigh damping in the explicit and implicit integrals takes the same value, and the stiffness component of Rayleigh damping in the explicit integrals is taken as the negative of the stiffness component in the implicit integrals. Thus, the results of the two dynamic analyses can be in good agreement. The results provide a reference for the application of Rayleigh damping in the explicit integral for the seismic analysis of nuclear power structures.

Effect of Earthquake-Induced Structural Pounding on the Floor Accelerations and Floor Response Spectra of Adjacent Building Structures

The influence of earthquake-induced structural pounding among buildings is paramount in the seismic analysis and design of structures. The recognition of such a phenomenon has been growing in the last decades. The search for ways to understand and mitigate the consequences of these structural collisions in building structures is the primary goal of the investigation of earthquake-induced building pounding. This phenomenon is known for increasing the floor accelerations, mainly where pounding occurs, implying significant local damage. These collisions cause short-duration acceleration pulses that may compromise the building structure and the non-structural elements within the building’s stories. Non-structural elements supported by the structure’s floors under earthquake-induced pounding instances may present a risk to human lives and/or human activity. Hence, the influence of earthquake-induced pounding in the floor response spectra of two adjacent reinforced concrete structures with inelastic behavior is assessed by varying the number of stories and their separation distance. Pounding greatly influenced the floor acceleration spectra, increasing the spread of accelerations over a broader period range, particularly exciting low to moderate periods of vibration.

Study on seismic fragility of prefabricated columns connected by grouted sleeves based on IDA method

PurposePrefabricated columns connected by grouted sleeves are increasingly used in practical projects. However, seismic fragility analyses of such structures are rarely conducted. Seismic fragility analysis has an important role in seismic hazard evaluation. In this paper, the seismic fragility of sleeve connected prefabricated column is analyzed.Design/methodology/approachA model for predicting the seismic demand on sleeve connected prefabricated columns has been created by incorporating engineering demand parameters (EDP) and probabilities of seismic failure. The incremental dynamics analysis (IDA) curve clusters of this type of column were obtained using finite element analysis. The seismic fragility curve is obtained by regression of Exponential and Logical Function Model.FindingsThe IDA curve cluster gradually increased the dispersion after a peak ground acceleration (PGA) of 0.3 g was reached. For both columns, the relative displacement of the top of the column significantly changed after reaching 50 mm. The seismic fragility of the prefabricated column with the sleeve placed in the cap (SPCA) was inadequate.Originality/valueThe sleeve was placed in the column to overcome the seismic fragility of prefabricated columns effectively. In practical engineering, it is advisable to utilize these columns in regions susceptible to earthquakes and characterized by high seismic intensity levels in order to mitigate the risk of structural damage resulting from ground motion.

Seismic performance analysis of building structures using high damping rubber bearings

Seismic performance analysis of building structures using high damping rubber bearings