Earthquake Conditions Research Articles

Slope stability and dynamic stability analysis during the process of reservoir water level decline

In order to study the stability of the slope during the reservoir water level decline, the finite element analysis is carried out by using Seep/w, Slope/w and Quake/w modules in Geo-slope software, to analyze a self-designed slope during the process of that under normal conditions and occasional earthquakes. The variation curve of safety factor is obtained in the process under different working conditions. The results show that: (1) Under normal circumstances, during the process of reservoir water level decline, the safety factor of the slope will decrease firstly and then slowly increase. There is one most dangerous water level at the water level slope ratio of 1/2∼1/3; (2) When adjusting the different water level decline rate and keeping the same water level drop elevation, the higher the water level decline rate is, the lower the stability of the bank slope is, and the smaller the minimum safety factor is during the water level drop process; (3) In the case of an earthquake, the seismic load does not change the overall change trend of the slope safety factor during the process of the reservoir water level drop. What goes beyond the normal pattern of cognition is that, the peak acceleration of the earthquake and the minimum safety factor generally do not occur simultaneously. It can be clearly seen that the seismic intensity plays a more important role in affecting the stability of the slope compared to the reservoir water level decline rate. The research results have certain guiding significance for the regulation of reservoir water level and the safety control of slope under earthquake conditions.

Stability Analysis of Aifa Bridge Abutment in Fafurwar District, Bintuni Bay Regency, West Papua Province

In the construction of public works infrastructure, especially road infrastructure works, bridge construction work plays a very important role besides the construction of the road itself. One of the things that deserves the attention of the planners in designing a bridge structure is the design of the substructure, this is because the substructure determines the quality and service life of a bridge. In addition, at present many cases of bridge structure failures are caused by failures of the substructure in holding the load acting on the bridge. The aim of this study was to determine the stability of the abutment to sliding failure and the stability of the abutment to overturning failure on the construction of the Aifa bridge in the Bintuni Bay Regency. From the results of the calculation of the stability of the abutments to sliding failure, when the abutments are in normal conditions was obtained safety factor (SF) values 1,907, in condition of the upper structure load is not working was obtained safety factor (SF) values 1,045 and during earthquake conditions was obtained safety factor (SF) values 1,419. While the results of the calculation of the stability of the abutments to overturning failure, when the abutments are in normal conditions was obtained safety factor (SF) values 4,640, in condition of the the upper structure load is not working was obtained safety factor (SF) values 1,658 and during earthquake conditions was obtained safety factor (SF) values 3,159. Because obtained safety factor (SF) values greater than 1, so that the stability of the abutment is safe to sliding failure and overturning failure.

Development of the Portable Shake Table for Simulating Building Characteristic under Earthquake Condition

Development of the Portable Shake Table for Simulating Building Characteristic under Earthquake Condition

A cross‐scale refined damage evolution analysis of large commercial aircraft crashing into a nuclear power plant

SummarySince the 9/11 attacks, whether nuclear power plants (NPPs) can withstand the malicious impact of large commercial aircraft has become a question that must be considered in the design phase. Refined model and fine‐scale element reflect more accurately the failure procedure and behaviour. However, due to the exceedingly complex structure of NPP, the traditional meshing method requires a substantial number of geometric operations involving point, line, area, and volume, leading to a tedious modelling process and very high computational costs, as well as making it difficult to modify and optimize the model. This paper combines the scaled boundary finite element method with the octree technique to refine nuclear engineering damage evolution analysis and establish a refined numerical model of the Generation III+ NPP, considering the detailed equipment hatch, air intake, and internal steel containment vessel structures. Subsequently, the refined damage evolution analysis of a large commercial aircraft crashing into an NPP was developed. The mesh size sensitivity, impact region shape comparison, and the influence of different impact heights were discussed. The results indicate that the cross‐scale refined meshing and analysis method provides a high‐quality discrete grid with fewer elements. Furthermore, this method is highly flexible, more accurately simulating the damage evolution and gradual destruction process. We recommend future structural optimization for the air intake and conducting detailed analyses at this location. The cross‐scale analysis method presented in this paper enables a rapid, refined simulation of a malicious impact by a large commercial aircraft. Additionally, it provides technical support for future studies of the responses of NPPs' internal structures, systems, and equipment under extreme earthquake and other disaster conditions.

Experimental on the Residential Building of Earthquake Prone Areas using Shake Table Test

This paper highlights the experimental analysis on the Shake Table Test. The Shake Table is an equipment by which real earthquake conditions, forces and vibrations on any structure can be experimented, recorded and studied. When an earthquake occurs over an area it leads to the pause of the normal day to day life, havoc damages, loosing of human lives and failure of the structures. In this study the model is mounted is on the shake table and the vibrations are recorded. The Limit State Design criteria is considered from IS 456:2000 and for Seismic analysis the Load Combination is considered from IS 1893(PART-I):2002.

Analisis Struktur Terowongan Pengelak Pada Bendungan Kualu Kabupaten Toba Samosir Provinsi Sumatra Utara

Diversion structure consists of diversion tunnel and Cofferdam. These two contructions should built in the early construction of the dam, have function to divert the river flow during the period of dam construction. The plans of Kualu dam diversion tunnel designed using horseshoe shape F, upstream of the tunnel at a depth of 41.625 m and upstream elevation + 695.5 m. In this study there was flood routing with Q25th which is 709,331 m 3 /s and obtained using 9 m diameter, then a cofferdam is planned to build as high as 15 m. Based on the calculation of loading and calculated four load combinations, they are : after contruction condition, after contruction under earthquake condition, at the operation time condition, and at the operation time under earthquake condition. From the results of the load combinations, the structure was analyzed using Beggs method and Staad Pro method. These two methods were used to figure the maximum moment of the structure and to determine the needed reinforcement in the tunnel construction. After the analysis, it is noticed that there is a difference position of the maximum moment, this is caused by the support in the Beggs method assumed to be a vertical loads.

“Shock-Eye” - A Beidou-Based Earthquake Monitoring and Early Warning System

China’s earthquake activity is high in frequency, high in intensity, shallow in source and wide in distribution. It is a country with severe earthquake disasters. Earthquake disasters have brought huge losses to people’s lives and property safety in China. Based on this situation, combined with Beidou’s high-precision positioning and two-way communication technology covering millimeter level, supplemented by remote sensing and GIS technology, this paper aims to establish a new Beidou system-based seismic monitoring and early warning system to monitor the crust of earthquake-prone areas. The micro-deformation and motion situation, through the data exchange processing, construct a statistical analysis model, effectively predict the earthquake condition in time, automatically issue an early warning to the estimated area before the earthquake arrives, gain valuable time for personnel and property transfer, and form a simulated earthquake. The post-disaster scene provides technical support for the emergency rescue command after the earthquake. We call it the “shock-eye” system. At the same time, the system can provide services for medium and long-term earthquake prediction through observation and processing of massive continuity data.

Oil damper with variable stiffness for the seismic mitigation of cable-stayed bridge in transverse direction

Stiffness in the transverse direction is a key issue for cable-stayed bridges. Moreover, the stiffness requirements for wind resistance and seismic isolation are in opposition. To solve this problem, a novel oil damper with variable stiffness (ODVS) is developed in this study. The damper consists of a hydraulic cylinder and overflow valves, and can be installed between deck–tower and deck–pier connections in the transverse direction. The ODVS exhibits high stiffness to resist wind load in service conditions, and low stiffness to isolate the deck under earthquake conditions. The ODVS can be designed as a low-stiffness, high-damping damper, and its mechanism is explained. A hysteretic model of the ODVS is developed and validated through sinusoidal excitation tests. The seismic performance of the ODVS is compared with that of triangular-plate added damping and stiffness (TADAS). The numerical results show that the ODVS has better performance in decreasing the transverse displacements at the end of the deck because of its low stiffness.

Reliability Evaluation Model of Power Grid Considering the Structural Reliability of Tower under Earthquake Conditions

The seismic disaster will cause serious damage to the power system. At present, the reliability evaluation of the power grid under earthquake conditions is mainly subjected to the approximate analysis of seismic performance, and the approximate analysis results can not meet the actual needs. In this paper, a reliability evaluation model of Power Grid considering the structural reliability of tower under earthquake conditions is proposed. The structural problems of tower and cable are analyzed directly by finite element simulation. The failure rate of transmission line is calculated by the structural reliability of tower and cable. After obtaining the reliability data of transmission line, the reliability of the power system under various seismic intensities is evaluated. Finally, the influence of the location of seismic source on the reliability of power system is analyzed. The results of the example analysis verify the accuracy and practicability of the proposed model and provide a reference for improving the seismic performance of the power system.

Determining the effective level of outrigger in preventing collapse of tall buildings by IDA with an alternative damage measure

Outrigger and belt truss have been successfully applied in reducing the lateral displacement of tall buildings under wind and earthquake conditions. Limited number of researches that have considered the inelastic seismic behavior of tall buildings with braced core-outrigger system, have just examined outrigger efficiency in reduction of drift or core moment and have not studied its efficiency in preventing “collapse” of tall buildings under severe earthquakes. This paper presents the results of an analytical study on the capability and effective level of outrigger in preventing collapse of tall buildings with braced core system during two sets of far and near field earthquakes. Results of NLTHA showed that tall buildings with braced core consisting of stronger braces, designed in accordance with UBC97, will collapse under severe near-field records as a result of failure of their columns. Similar buildings with either optimized braces, designed according to AISC341-16, or RC shear wall core could survive same earthquakes. Various levels were examined for the outrigger location along building height to prevent their collapse. By performing the incremental dynamic analysis on the studied structural models, the achieved enhancement due to the outrigger addition was investigated. A new damage measure was proposed to be used in IDA that can describe the point of structural collapse, more precisely. It was observed that in order to successfully prevent the collapse of studied structures under severe near-field records, two outriggers must be used, one at the second story and the other at about 0.14 height of structure.

Development Characteristics and Stability Evaluation of Unstable Slopes in Huachi County

This paper divides the unstable slopes in Huachi County into soil and rock. The final deformation evolution of unstable slopes is landslide, collapse and continuous cumulative deformation to maintain an unstable state, in which landslides and collapse disasters may dominate. The typical Donggou unstable slope profile in the county is selected for analysis, The calculation results and numerical simulations shows that the slope is stable under the conditions of self-weight and earthquake; The sections of the slopes 1-1/ and 3-3/ are basically stable under heavy rainfall conditions. The calculation results are basically consistent with the qualitative analysis, indicating that heavy rainfall is the main cause of unstable slope deformation.

Dynamic behaviour of micaceous sand with varying mica content and its association with compactability, compressibility and monotonic shear response

ABSTRACT Cohesionless soils are highly susceptible to liquefaction under dynamic loading with high-strain amplitude simulating earthquake loading conditions. The presence of flaky mica particles among spherical sand influences the microscopic particle level mechanisms due to complex geometric arrangements caused by bridging, ordering and pore filling phenomena. Such variations substantially affect the compactability, compressibility and shear strength behaviour under monotonic and dynamic loading conditions. The current experimental investigations evaluated the effect of mica content on dynamic behaviour of micaceous sand through a series of strain-controlled cyclic triaxial tests at constant frequency and double axial strain amplitude of 0.5 Hz and 0.6% per cycle. The variation in dynamic parameters such as shear modulus and damping was determined at different mica contents along with cyclic stiffness degradation. Cumulative dissipated strain energy was also estimated to understand the contact-force networks of varying sand and mica matrix from sand-sand to mica-mica through sand-mica particle contact.

Seismic behaviour of steel-reinforced ultra-high-strength concrete composite frame: Experimental study

This article provides the results of an experimental study on the seismic behaviour of the steel-reinforced ultra-high-strength concrete frame. A two-bay and three-story one-fourth scale steel-reinforced ultra-high-strength concrete frame specimen was tested under simulated earthquake loading conditions. The seismic behaviours of the specimen, including the failure mode, concrete element cracks development, hysteresis loops, lateral load-carrying capacity, ductility, energy dissipation, strength and stiffness degradation, were investigated under low reversed cyclic lateral loading. The test results showed that the beam hinge failure mechanism of the steel-reinforced ultra-high-strength concrete frame was achieved. The steel-reinforced ultra-high-strength concrete frame would have rich and stable hysteretic loops when subjected to large axial load with an axial load ratio of 0.38. The roof and interstory ductility coefficients of the steel-reinforced ultra-high-strength concrete frame ranged from 5.06 to 6.78. The strength and stiffness degenerated gradually, indicating an excellent seismic behaviour of the steel-reinforced ultra-high-strength concrete frame with sufficient ductility and high energy dissipation capacity. The test and analysis results can be served as a design reference for practical engineering applications.

Mapping the Level of Earthquake Risk of Holtekamp Bridge at Jayapura Region Based on Earthquake Data and Microtremor Measurement

Holtekamp bridge which is located in Jayapura region between Hamadi and Holtekamp Village in the Northern part of Papua Island. The region constitutes an active earthquake zone with the recurrence frequency and magnitude of the earthquake are relatively high. The region is located on an active fault zone. The seismotectonic setting in the region is directly implied to the calculations of the seismic design for engineering and design purposes on building and non-building structures including Holtekamp bridge in Jayapura city. To recognize a characteristic of the earthquake at the site of interest, the historical earthquakes (background) data surrounding the study area. Local microtremor measurements data are analyzed by means of a probabilistic seismic hazard analysis (PSHA). Deterministic seismic hazard analysis (DSHA) using some ground-motion models in attenuation relationship equations. In resulting of seismic hazard parameter as represented by peak ground acceleration (PGA), values in earthquake scenario at operating basis earthquake (OBE), maximum design earthquake (MDE), and maximum credible earthquake (MCE) conditions. These values are used as a reference to evaluate the compliance of the current technical aspects with the new required design facing the updated seismicity parameters.

Seismic response of single piles in liquefiable soil considering P-delta effect

Dynamic analyses of piles subjected to both vertical and horizontal loading under seismic conditions are of great significance to geotechnical and practicing engineers and the numerical methodology proposed in the present study fills the existing research gap. A finite difference based computer program FLAC3D is used to model a single pile and obtain the deflection and bending moment behaviour along the depth of the pile, under earthquake loading conditions in both non-liquefiable and liquefiable soil. The various earthquake motions considered in the current analysis includes 1989 Loma Gilroy, 1995 Kobe, 2001 Bhuj and 2011 Sikkim motions The bending moment is maximum at the interface of the liquefying and non-liquefying soil layers due to shear strain in the soil being discontinuous across the interface of the layers. The free field ground surface displacement is observed to initially increase with time, reaching the maximum at some instant during shaking and thereafter it remains constant with time, due to local failure of the liquefiable soil around the pile foundation. The combination of vertical load and lateral load on the pile top is varied to obtain the P-delta curves under dynamic loading conditions which are important factors for peak pile bending moment, when there is lateral spreading due to liquefaction causing displacement of the pile head, and inertial load from the superstructure is present. Hence a thorough evaluation of both horizontal and vertical inertial interactions and kinematic interactions due to free field motions, is necessary for considering the behaviour of piles in liquefiable soil and under combined loading situations.

Influence of Substructure Levels on the Computed Seismic Performance of Low-Rise Structures

ABSTRACT Numerical simulations are performed to study the behavior of hypothetical one, two, and three-story structures when different earthquake conditions occur in a selected soil profile in the southern California. Computed performance of the low-rise structures is assessed including substructure modeling of basement levels in numerical simulations. The numerical simulations showed the relationship between number of stories, peak ground acceleration, ground surface settlements, and horizontal peak story accelerations induced by the earthquakes and the computed performance of hypothetical structures built on liquefiable soils. The results suggest that the inclusion of basement levels positively influenced the overall seismic performance of low-rise structures.

Influence factors on the seismic behavior and deformation modes of gravity retaining walls

This study investigated the influence factors on the seismic response and deformation modes of retaining walls using large-scale model shaking table tests. Experimental results showed that the distribution of peak seismic earth pressures along the height of a wall was a single peak value curve. The seismic earth pressures on a gravel soil retaining wall were larger than the pressures on the weathered granite and quartz retaining walls. Also, the peak seismic earth pressure increased with increases in the peak ground acceleration and the wall height. The measured seismic active earth pressures on a rock foundation retaining wall were larger than the calculated values, and the action position of resultant seismic pressure was higher than 0.33 H. In the soil foundation retaining wall, the measured seismic earth pressures were much smaller than the calculated values, while the action position was slightly higher than 0.33 H. The soil foundation retaining wall suffered base sliding and overturning under earthquake conditions, while overturning was the main failure mode for the rock foundation retaining walls.

Seismic Design of Bridges against Near‐Fault Ground Motions Using Combined Seismic Isolation and Restraining Systems of LRBs and CDRs

This paper focuses on the seismic isolation design of near‐fault bridges under the seismic excitations of near‐fault ground motions in high‐intensity earthquake zones and proposes a combined control system using lead rubber bearings (LRBs) and cable displacement restrainers (CDRs) along with ductility seismic resistance for the reinforced concrete piers. As part of the performance‐based seismic design framework, this study provides the quantitative design criteria for multilevel performance‐based objectives of a combined control system under conditions of frequent earthquake (E1), design earthquake (medium earthquake), and rare earthquake (E2). Moreover, in this study, a preliminary performance‐based seismic isolation design for a near‐fault actual highway bridge in high‐intensity earthquake zones (basic peak of ground acceleration 0.4 g) was developed. Using nonlinear time‐history analysis of the actual bridge under near‐fault ground motions, the feasibility of a performance‐based design method was validated. Furthermore, to ensure the predicted performance of the isolated bridges during a strong earthquake, a relatively quantitative design in structural details derived from the stirrup ratio of piers, expansion joints gap, supported length of capping beams, and limited vertical displacement response was obtained.

Fluid-structure-soil interaction effect on dynamic behaviour of circular water tanks

To investigate the seismic behaviour of concrete tanks on different soil conditions, fluid-structure-soil interaction system is simulated using finite element analysis software ANSYS. The influence of soil properties on tank's dynamic behaviour is studied by performing modal and transient analyses of cylindrical tanks resting on different soil conditions. Considering four different soil properties, comparisons are made on response parameters such as displacement in radial direction at top of tank wall, maximum hoop force, bending moment and base shear. The effect of frequency content of earthquake on seismic behaviour circular concrete tank is investigated by conducting time history analyses of the tanks under three different earthquakes. All the analyses were performed for half fill and full fill condition. Transient analyses show that the soil property, frequency content of earthquake and water fill condition have significant effect on seismic response of the water tanks.

Three‐Dimensional Nonlinear Seismic Response of Immersed Tunnel in Horizontally Layered Site under Obliquely Incident SV Waves

A three‐dimensional (3D) detailed numerical model of an immersed tunnel in a horizontally layered site is established in this study. The 3D seismic response of the immersed tunnel in a horizontally layered site subjected to obliquely incident waves is analyzed based on the precise dynamic stiffness matrix of the soil layer and half‐space via combined viscous‐spring boundary and equivalent node stress methods. The nonlinear effects of external and internal site conditions on the whole model were determined by equivalent linearization algorithm and Mohr–Coulomb model, respectively. The proposed model was then applied to investigate the nonlinear seismic response of an immersed tunnel in the Haihe River subjected to seismic waves of oblique incidence. The dislocation (opening) of pipe joints in the immersed tunnel were analyzed to determine the response characteristics of the shear keys and overall displacement of the tunnel; the dynamic responses of the immersed tunnel subjected to obliquely incident seismic waves markedly differ from those of vertically incident seismic SV waves. The maximum stress value of shear keys and the maximum dislocation of the pipe joint appear as upon critical angle. The overall displacement of the tunnel increases as incident angle increases. Under severe earthquake conditions, both the pipe corners and midspan section of the roof and floor are likely to produce crack. These areas need careful consideration in the seismic design of immersed tunnel structures.