Effect Of Seismic Loading Research Articles

Mainshock–aftershock seismic fragility assessment of civil structures: A state‐of‐the‐art review

AbstractSequential seismic events occur worldwide, which impose significant threats to the safety and serviceability of Civil infrastructure, especially buildings and bridges. Fragility functions are imperative to support decision‐making tools for potential seismic risk identification and its impact on structural performance during sequential earthquakes. The increasing number of publications shows a notable increase in interest among researchers and the scientific community in this domain. This study presents a systematic review of available resources and techniques for structural performance and fragility evaluation subjected to mainshock–aftershock seismic loading. Efforts have been made to focus on the salient features of various approaches rather than criticizing the mathematical frameworks and associated analysis approaches. Existing knowledge related to the effect of sequential seismic loading on buildings and bridge infrastructures and their fragility estimates is presented concisely. The paper concludes by detailing the opportunities for future developments in the fragility analysis of Civil infrastructure under sequential seismic hazard. This would encourage stakeholders and decision‐makers to put into practice their applications for risk mitigation, recovery planning, and well‐informed decision‐making.

Seismic Loading and Reinforcement Effects on the Dynamic Behavior of Soil Slopes

Seismic Loading and Reinforcement Effects on the Dynamic Behavior of Soil Slopes

Hypermobility of a Catastrophic Earthquake-Induced Loess Landslide

Landslide mobility refers to how far and fast a landslide can move downslope. It controls landslide impact areas and damage power. Highly mobile landslides are often initiated on slopes steeper than 30°. However, on 18 December 2023, an earthquake-induced landslide (35°52′54″N, 102°51′10″E) exhibited extraordinary mobility, with an overall travel angle of 1.5°, breaking an on-land landslide record. The landslide originated on a gentle slope (3.6°), eroded an earth dam along its travel path, and finally destroyed 51 houses and claimed 20 lives. Remote sensing and field surveys were conducted to provide morphological characteristics of the hazard chain. A numerical program, EDDA (Erosion–Deposition Debris Flow Analysis), was employed to reproduce the flow dynamics and investigate the causes of hypermobility. The findings reveal three primary causes of hypermobility: (1) liquefaction of the saturated silty loess stratum due to the combined effects of irrigation activity and seismic loading, (2) the loose and macro-pore structure of loess, and (3) confined topography and icy channel bed. The mechanisms revealed have broad implications for understanding fluidized mass movements on gentle slopes in seismically active regions.

Stability analysis of an unreinforced concrete gravity dam

This project involved undertaking a stability analysis of an unreinforced concrete gravity dam. The stability assessment considered the 1 in 10 000 year and probable maximum flood events as well as the effects of ice and seismic loading, concluding that the above-ground dam section did not meet modern factors of safety and that further works would be required to stabilise the dam.

Finite element analysis-based blast and seismic performance evaluation for RC frame with retrofitted ENTA damper systems

Blast loading and seismic excitations are widely recognized as the most detrimental occurrences that a building structure may encounter throughout its lifespan. Therefore, this study investigated the retrofitting capacity of external devices (ENTA damper systems) for reinforced concrete (RC) frames in term of enhancing their resistance under the combined effects of blast and seismic loads. This study presents the establishment of finite element (FE) models for retrofitted RC frames with ENTA damper systems through the utilization of the dynamic analysis software LS-DYNA. The investigation involved the validation for blast performance of RC column in order to identify the most effective method for modeling blasts. Additionally, the study aimed to validate the performance of RC frame models through effects of ENTA damper systems under seismic loading. Subsequently, a performance evaluation of RC frame structures was carried out to examine the impact of the ENTA damper systems when subjected to blast loading. The findings of the study indicate that the use of external ENTA damper systems effectively enhanced the rigidity and structural integrity of RC frames, while maintaining their ability to resist deformation. Finally, the damage assessment of blast and seismic performance is investigated based on various parameters such as ductility, drift and energy-based damage limits.

Stability Analysis of Waste Landfills on Potentially Unstable Territory

Abstract The article presents the stability analysis of two adjacent waste landfills located in a potentially unstable territory. One of the waste landfills is reclaimed and consists of ash. Municipal solid waste is actively deposited in the second landfill. In the space between the landfills, the expansion of the municipal solid waste landfill is planned, with a partial overlap of the reclaimed ash landfill. The instability of the area where the landfills are located is due to its susceptibility to the formation of landslides. The article presents the results of experimental verifications of the peak shear strength parameters of the ashes and the peak and residual shear strength of the soils forming the subsoil of both landfills and serve as input for stability analyses. The shear strength parameters of municipal waste are defined on the basis of literature research. The potential instability of both waste landfill territories was taken into account using the parameters of the residual shear strength of the subsoil. The stability analysis of waste landfills is expressed using both the peak and residual shear strength parameters of the subsoil of waste landfills. In addition, the effect of seismic loading on both landfills is considered in the stability analysis.

Performance Optimization Design Study of Box-Type Substations Subjected to the Combined Effects of Wind, Snow, and Seismic Loads

As a pivotal node in both urban and rural power grids, the box-type substation not only serves the functions of power conversion and distribution but also need to provide structural support and environmental adaptability. However, deficiencies in strength, stiffness, or vibration characteristics may lead to vibration and noise issues, and extreme environmental changes can pose risks of structural damage. This study aims to verify and optimize the seismic resistance and environmental adaptability of box-type substations through finite element simulation methods. Using SOLIDWORKS, a three-dimensional model of the box-type substation was constructed, and static and dynamic analyses were conducted using Ansys Workbench to comprehensively evaluate the dynamic response of the box-type substation under wind, snow loads, and seismic action. Through iterative simulations and a comparison of multiple design solutions, the structural optimization of the substation was achieved. The optimized structure balances strength and stiffness, significantly reducing the weight of the substation body, with the wall thickness reduced by 60%. Additionally, the phenomenon of stress concentration on the side walls was eliminated, ensuring that the equivalent stress is below the material yield strength. This research provides methods and empirical results for enhancing the performance and reliability of box-type substations under seismic conditions, confirming the feasibility of a lightweight design, while ensuring structural safety.

Seismic analysis of coastal slope stability considering strength nonlinearity and tension cut-off

Tensile stresses may lead to cracks forming at the crest of coastal slopes and subsequent slope failure, particularly under seismic load conditions. Traditional shear strength failure criteria often overestimate the tensile strength of geomaterials, and in turn the factor of safety against sliding. This paper presents an improved nonlinear analysis method for assessing the stability of slopes, while considering tension cut-off in the failure criterion as well as the detrimental effects of inertial seismic loading and pore water pressure. The method employs the principle of energy consumption to obtain solutions for the geometry of the potential sliding surface and stress distribution, while the critical slope height and the stability factor are determined by means of a particle swarm optimization algorithm. Comparison with existing methods is conducted to validate the effectiveness and accuracy of this method. Results showed that the tensile strength of geomaterials had a significant impact on the stability of the slope and its associated failure mechanism, particularly for the vertical slope. This study could avoid the assumptions of the dilatancy angle on the velocity discontinuity and critical slope sliding surface, and reflect the tensile and nonlinear characteristics of the geomaterials well.

Energy and structural optimization of mid-rise light-frame timber buildings for different climates and seismic zones in Chile

Location determines not only the climatic condition but also the structural loads that the structure must withstand. Given the broad variety of climatic and seismic requirements of Chile, the design of lightweight timber buildings considering both energy and seismic design parameters and boundary conditions becomes a difficult task. The main objective of this research is to analyze and quantify the effect of climates, seismic loads, lateral anchorage, and story number on the optimal energy design solutions, including the seismic behavior in a light-frame timber building. Furthermore, the optimal design was parametrically analyzed considering five Chilean cities that consider different climates, seismic zone, number of stories, and lateral anchorage systems to prevent rocking (overturning) due to lateral seismic forces. The optimal wall insulation thickness, stud spacing, and thermal mass exhibited significant variations depending on the buildings' number of stories, lateral anchorage system, climate, and seismic zone. Therefore, the results of this investigation reinforce the necessity of integrating energy and seismic designs for light-frame timber buildings. The optimal designs obtained in this investigation showed considerable variations depending on the combination of climatic and seismic loads as well as the number of stories and anchoring systems. The article's main contributions are the evidence of the structural and energy design interconnection of light-frame timber buildings and how design variables, such as stud spacing, floor concrete thickness layer, and wall insulation thickness, are related and change according to the different climates, seismic loads, lateral anchorage, and story number.

Beneficial Effects of Infill Walls on the Structure and Foundation Lateral Performance Under the Effect of Seismic Loads

Beneficial Effects of Infill Walls on the Structure and Foundation Lateral Performance Under the Effect of Seismic Loads

Evaluation of clay layer presence on shallow foundation settlement in dry sand under an earthquake

Abstract Seismically, settlement of buildings with shallow foundations lying above dry sand soils has caused severe destruction in recent earthquakes. This study investigated the effect of seismic loads with shallow foundations located above sandy soil containing an intermediate soft clay layer. The impact of a clay layer’s existence with different thickness and closeness to the base of foundation when subjected to El Centro earthquake with 6.9 magnitude. This investigation has been carried out with the help of a three-dimensional PLAXIS 3D, which has been used to solve many geotechnical issues. A database was created for the various dynamic and static parameters of soils in seismically active areas of Iran and Iraq and USA. In this research, important factors are recognized, including relative density. Clay layer thickness and proximity to the foundation, the soil relative density the results of this research indicated that shallow foundation settlement increased on the dry sand and decreased with the presence of clay layer thickness and wave propagation in cohesion soil is less than cohesion-less soil. In addition, it was reached that as close as the clay layer to the foundation the settlement increased.

Effect of Seismic Loading on Porewater Pressure in Clayey Soil under Disconnected Piles-Raft Foundation

The disconnected piled raft foundation (DCPRF) is one of the newly introduced foundations for specialization in geotechnical engineering, which significantly reduces the moment and stress on the pile head. In addition, this type of foundation is an ideal choice in areas with seismic activity due to the presence of cushion material between the raft and the piles. This work aims to present a numerical model in PLAXIS 3D software for connected piled raft and disconnected piled raft foundations under the influence of seismic loads and investigate the effect of pore water pressure on the disconnected foundation compared to the connected foundation. The study will depend on the earthquake that struck Iraq in November 2017 in the Halabja region. Strength was 7.3 on the Richter scale with PGA (0.1g). The results of changing pore water pressure showed the variation of pore water pressure. In the case of a DCPRF, the porewater pressure and excess porewater pressure in the soil are much greater than in the case of a CPRF. The increase in the porewater pressure is due to the weight of the building and the weight of the additional cushion layer on the soil. The mechanism for transferring the load in the case of a DCPRF is carried out by raft, then to the cushion, and then to the soil and piles. The load transferred to the soil in the case of DCPRF is more than that transferred to the soil in the CPRF system.

The Effect of Seismic Load on TBM Structures for Metro Line 3 in Hanoi, Vietnam

Metro line 3 in Hanoi is being constructed using tunnels, which may affect nearby constructions. In addition, Hanoi’s earthquakes also pose risks to this Tunnel Boring Machine (TBM) line. This paper studies the impact of TBM construction on the surrounding houses along the line, as well as the impact of earthquakes on this line. A 3D numerical model was developed to simulate the static and dynamic behavior of TBM at station 9 in Metro Line 3. The results show that the maximum settlement at the ground surface under seismic load is significantly reduced from 4.6 mm to 0.1 mm when using the jet grouting method.

Seismic performance of structure equipped with a new rubber bracing damper system

Nowadays, vibration energy absorption devices are widely implemented in many buildings subjected to severe vibration due to natural hazards, such as earthquakes, strong winds, and typhoons. Recently, viscous dampers have been commonly used in many structures as the most conventional damper type. However, the high maintenance cost resulting from oil leakage from cylinder seals has prompted researchers to seek an alternative system to viscous damper systems. Therefore, the main aim of this research is to develop a new rubber bracing damper (RBD) system by implementing high damping rubber material as a viscoelastic material to be installed in framed structures as diagonal bracing members. This will help dissipate vibration effects on the structure. To achieve this, the initial design for the RBD device has been developed, and finite-element simulation has been conducted to evaluate the behavior of the proposed RBD under various dynamic loading conditions. To define the viscoelastic material properties in finite-element modeling, high damping rubber material has been produced and experimentally tested to determine the numerical model of the material. Subsequently, the test data were utilized to develop the analytical model of the RBD device, and its performance was evaluated by applying cyclic loads and conducting nonlinear analysis. Furthermore, a series of cyclic dynamic tests with various displacement amplitudes and frequencies have been conducted on the prototype of the RBD device based on the finite-element results. Finally, to analyze the dynamic behavior of the structure equipped with RBD, a finite-element model of a three-story reinforced concrete frame structure furnished with RBD dampers has been developed. The response of the structure has been evaluated under seismic loads, and a parametric study has been conducted to investigate the response of the structures with various rubber properties. The numerical analysis results indicated that the implementation of the RBD device leads to a reduction in the occurrence of plastic hinges and lateral displacements of the structure by up to 69%. This demonstrates the efficiency of the RBD device in diminishing the seismic load effect on the structure’s response.

Effect of seismic loading onV-H-M capacity of well foundation

Effect of seismic loading onV-H-M capacity of well foundation

Numerical Simulation of Pile Group Response in Slope Layered Soil under the Effect of Seismic Loading

This work investigates the effect of earthquakes on the stability of a collective pile subjected to seismic loads in the soil layer. Plaxis 3D 2020 finite element software modeled pile behavior in dry soils with sloping layers. The results showed a remarkable fluctuation between the earthquakes, where the three earthquakes (Halabja, El Centro, and Kobe) and the acceleration peak in the Kobe earthquake had a time of about 11 seconds. Different settlement results were shown, as different values were recorded for the three types of earthquakes. Settlement ratios were increased by increasing the seismic intensity; hence the maximum settlement was observed with the model under the effect of the Kobe earthquake (0.58 g), where subsidence values at the three tremors differed between the pile distribution pattern. The highest drop recorded by the results was 60 mm in a distribution pattern 2×3. In general, increasing the size of the cap leads to an additional drop due to the weight of the cap.

A comparative analysis of design and analysis methods for steel connections: contrasting American and European perspectives

Load transmission from one element to another is achieved using steel connections, making them an integral part of any structural design. This article examines the differences between the American Codes (AISC) and Eurocode 3 for the design and analysis of steel connections. Moment connections' stiffness, strength, and ductility as expressed in both codes are the core focus of this research. Each tactic's advantages and disadvantages have been detailed, and the effect of seismic load on steel connection design has been investigated. The feasibility of using techniques like haunches and stiffeners to enhance connection design is also explored. The study focuses on moment connections and how they fare under different loads and conditions like stiffness, strength, and ductility. Additionally, the effect of seismic loading on the development of steel connections is analyzed. Finally, the significance of testing and documentation to guarantee the safety and dependability of steel connections has been evaluated. This research can help engineers select a suitable code and connection typology for their projects for improved performance of the overall structural behaviour.

Experimental Study on Behavior of Precast UHPC Beam-Column Joints Subjected to Cyclic Loading

Ultra-performance concrete (UHPC) is a new material with many outstanding features such as compressive and tensile strength that are both very high compared to conventional concrete. In precast reinforced concrete structures, the beam-column joint is one of the most important parts. In this type of connection, the beam is connected to the column through post-tensioned prestressing steel bars (PC bars), making the connection resistant to bending moments as well as shear forces. This paper presents the behavior of this type of connection under the effect of seismic loads on the following criteria: flexural resistance, moment-rotational relationship, change of PC bars’ prestress during and after cyclic loading.

ASD and LRFD lateral load combinations: Comparison of required strength and reliability for design of structural steel

ASCE 7, Minimum Design Loads for Buildings and Other Structures, provides load combinations for both Load and Resistance Factor Design (LRFD) and for Allowable Stress Design (ASD), defining the required strength of structural members and connections. Similarly, the AISC Specification for Structural Steel Buildings provides resistance factors for LRFD and safety factors for ASD to be applied to the nominal strength for each limit state, permitting design using either method in conjunction with the corresponding load combinations in ASCE 7. Previous publications have demonstrated that similar designs (with similar levels of reliability) result from the application of LRFD and ASD for cases in which the governing load combination has live load as the principal load. This study presents comparison of ASD and LRFD demands, and corresponding reliability indices, from ASCE 7 lateral load combinations, determined with different proportions of dead, live, wind, and seismic load effects and a range of levels of second-order effects. The findings indicate that the generally accepted uniformity between the two design methods established for gravity load combinations does not always extend to lateral load combinations. For a range of conditions, design using ASD load combinations provides significantly lower reliability than using LRFD and does not meet the ASCE 7 reliability target.

Initial stiffness degradation and its effect on seismic capacity of shear wall with high reinforcement volume: An experimental study

Nuclear simulation analyses and field investigations were performed to study the seismic response of the reinforced concrete (RC) walls of the Onagawa NPP Unit 2 reactor building to the Tohoku Region Pacific Coast Earthquake on March 11, 2011 (hereafter referred to as the “March-11 Earthquake”). They indicated that the degree of deformation of the walls remained within the elastic range and did not reach the plastic range. Small residual cracks appeared in the shear walls on some floors, and the observation records of the natural period of the building exhibited stiffness degradation. In addition to the effect of large seismic loads, which are among the factors responsible for such reduced initial stiffness, a correlation between reduced stiffness and deterioration due to aging was recognized in the results of the analyses based on long-term earthquake observation records. The likely factors responsible for deterioration from aging include internal stress and cracks resulting from the drying shrinkage characteristics of concrete. Therefore, we conducted seismic resistance experiment #1, a static load test, to understand the effect of drying shrinkage on the initial stiffness and maximum strength. The results for the specimens subjected to drying showed better agreement with the results of the observation record analysis of the reactor building than those that were not subjected to drying. In addition, because small residual cracks occurred in the reactor building, we conducted seismic resistance experiment #2, a static load test, to understand the effect of such cracks on the ultimate strength and deformation capacity. The test confirmed that the seismic performance of the building after the earthquake was ensured. From the results of these investigations, it is considered that both the drying shrinkage of concrete and large seismic forces from the March-11 Earthquake were factors in the initial stiffness reduction of the Onagawa Unit 2 reactor building. However, there was no significant impact on the seismic performance of the building.