Earthquake Conditions Research Articles

Methods for the development of an alignment platform for an astronomical instrument with application to the METIS instrument at the ELT

Hexapods are very common in astronomy as a mechanism to provide a stiff mount or a precision alignment tool. Here, we present a lumped model for a general symmetric hexapod that allows us to compute the load distribution under external forces, the hexapod’s resolution, and the identification of singularity loci within the workspace. We also developed a script to analyze this parametric model, which is publicly available. We use this model to develop and design a hexapod for mid-infrared ELT imager and spectrograph, one of the extremely large telescope’s first light instruments. The designed hexapod solution can survive strict earthquake conditions that can go up to 5g, and position and align the 11 ton instrument with submillimetric and arcsecond precisions. Although the model presented is not as precise or as realistic as a finite element (FE) analysis, it provides, in a fraction of a second, a very good first approximation. Therefore, unlike FE methods, the model is able to study many geometries in a short time.

Seismic Response of Mechanically Stabilised Earth Retaining Wall

Mechanically Stabilised Earth retaining wall has become a premier choice of retaining wall design in places where seismic and high vibration loads are frequent. The wall displacement has to be monitored regularly for the safe and economic function of the structure. In the present paper, a numerical study on an MSE wall model under real records of earthquake loading condition using an explicit finite difference program has carried out. A parametric study to scrutinize the influence of strong-motion parameters such as peak ground acceleration and predominant frequency on the permanent displacement of the wall is accomplished. The influence of PGA and frequency of seismic excitation was visible in the results. At higher frequencies, the ground surface is disturbed severely leading to excessive heaving on the surface. The amplification of strong motion along the backfill is observed for low PGA motions, whereas, de-amplification is observed for high PGA motion.

The effect of longitudinal reinforcement ratio on the lateral buckling behavior of R/C walls modelled using prism elements

Studies on buildings subjected to earthquake action have shown that failure due to lateral buckling can cause structures to collapse. Therefore, transverse instability, its characteristics, and the mechanical factors that affect it need to be investigated to ensure the safety of structures. In the current experimental and analytical study, 22 tests were conducted using 11 column specimens constructed at a scale of 1:3 to simulate the boundary edges of structural walls. These specimens had varying ratios of longitudinal reinforcements (from 1.79% to 10.72%). The degree of tensile strain applied before compressive loading was 30‰ for all specimens. The present study examines the influence of the percentage of longitudinal reinforcement on the ultimate compressive capacity, deformation (axial and transverse), failure modes, and out-of-plane behavior of reinforced concrete seismic walls under earthquake loading conditions. It has been found that increasing the reinforcement ratio is not sufficient, by itself, to inhibit transverse instability, although it does affect its characteristics. It has also been discovered that rebar arrangement affects lateral buckling characteristics.

Comparative Study on the Stability of Hydropower Station Slope Under Different Earthquake Conditions

In order to explore the stability characteristics of hydropower station slope under different working conditions under seismic action, the three-dimensional dynamic finite element method was used to analyze the working conditions of the hydropower station slope under the seismic load with a probability of exceeding 5% in 50 years, 2% in 100 years, and 1% in 100 years in the reference period, through comparing the dynamic response characteristics and the stability of the slope under different seismic load were obtained. The results showed that under the influence of different earthquake loads, the ground motion response of the slope would increase with the increase of the peak value of the excited ground motion, and all would be forced to vibrate according to the vibration form of the excited ground motion; compared with the amplification effect of the slope on the displacement, the amplification effect of the slope on the acceleration was more obvious, this phenomenon was more obvious when the slope was under the action of an earthquake load with a probability of exceeding 1% within 100 years of the reference period; with the increase of seismic load, the possibility of bedding sliding and failure of the slope surface would be greater; when the three types of seismic loads act on the slope respectively, the other surfaces of the slope would generate instantaneous tensile stress, but they were less than the tensile strength of the slope rock mass. When the slope was under rare ground motion with a 100-year exceeding probability of 1% and 2%, the maximum relative dynamic displacement was about 5 cm, and the slope was sufficient to withstand the test of strong ground motion; for the other two seismic conditions, when the slope was under the action of an earthquake load with a probability of exceeding 1% within 100 years of the reference period, the damage effect of the slope near the empty surface under the action of the earthquake was more obvious than that of the center of the slope.

Embankment Seismic Fragility Assessment under the Near-Fault Pulse-like Ground Motions by Applying the Response Surface Method

Uncertainties of the ground motions and structural parameters are the main factors that limit the accuracy of embankment seismic fragility assessment. In response to the uncertainties of the ground motions, artificial synthesizing method of the near-fault pulse-like ground motions was proposed, and 15 ground motions with the rupture fault distances ranging from 1 to 15 km were synthesized by taking the Chi-Chi earthquake in Taiwan, China, as an example. The Xi’an-Baoji expressway K1125 + 470 embankment was taken as the research object, and a total of 12 structural parameters were selected as the design variables, namely, the elastic modulus, bulk modulus, shear modulus, density, cohesion force, and internal friction angle of the embankment fill and soil foundation, respectively. In response to the uncertainties of these parameters, 3 principal components with large impacts on the embankment seismic fragility were extracted based on the principal component analysis. Mapping relationships among the principal components and embankment seismic damages were analyzed using the uniform design response surface method, and the seismic fragility assessment was carried out and the fragility curves were plotted. The research results are consistent with the actual embankment seismic damage conditions of the Chi-Chi earthquake, indicating that the proposed method is scientific and reasonable. It also shows that it would obviously overestimate the seismic performance in the embankment seismic fragility assessment without considering the uncertainties of the ground motions and structural parameters.

地震・放射線災害下保育における幼稚園教諭の精神的健康：レジリエンス要因として保育者効力感に着目した検討

地震・放射線災害下保育における幼稚園教諭の精神的健康：レジリエンス要因として保育者効力感に着目した検討

Behaviour and Strengthening Methods of Tall Slender Columns in Earthquake Conditions

Reinforced concrete buildings are normally designed and constructed with well-defined vertical column supports which are able to withstand both vertical and lateral loadings. In the case of high columns there is a risk of instability due to its slenderness caused by the higher apex ratio (measured by its height in relation to the width). This is compounded by having such buildings located at medium to high seismic risk zones, where lateral dynamic loadings can occur. This research paper focused on how such slender reinforced concrete columns will behave under earthquake loading conditions, and highlights some innovative ways to strengthen the column capacity to withstand both vertical and lateral loadings. Besides the conventional ways to provide diagonal or lateral bracings, the use of glass fibre reinforced polymer (GFRP) as an alternative material for retrofitting tall slender reinforced concrete columns are presented here. The new method includes spraying of the GFRP onto the external surfaces of the columns and also incorporate the GFRP bars as additional reinforcement into the concrete columns. Both methods proved to improve the durability and strengthen the tall reinforced concrete column. This study shows the ability of the new method of amelioration of the slender reinforced concrete columns to increase their stability during seismic activity.

Improvement of Evacuation Modeling by Considering Road Blockade in the Case of an Earthquake: A Case Study of Daitoku School District, Kanazawa City, Japan

In disaster management, evacuation modeling is considered a useful visual tool to disaster managers for reviewing current evacuation strategies, estimating the ability of shelters to accommodate all evacuees, and developing evacuation route planning. Though there are several existing studies on evacuation modeling in the case of an earthquake, research that integrates road blockades into evacuation simulations is quite limited. From that viewpoint, this research aims to develop evacuation modeling with consideration of road blockades to simulate how residents move to evacuation centers (hereafter, shelters) through urban areas following an earthquake occurrence. The research also determines difficulties that residents may encounter under earthquake conditions, compared with normal conditions, corresponding to considering or not considering road blockades, respectively, such as having no access to shelters, taking longer routes instead of shortest routes, and so on. Debris from damaged buildings in an urban area is assumed as the main source of debris that would cause a road blockade. The model is applied to a case study of the Daitoku school district in Kanazawa city. According to simulated results, due to road blockades, occupants of many damaged buildings did not have access to shelters, and a lot of evacuees needed to move to shelters with longer routes instead of taking the shortest routes. Furthermore, the research results show the possibility of considering road blockades for improving current evacuation modeling and making evacuation simulations more realistic.

ANALISIS STRUKTUR MOORING DOLPHIN KAPASITAS KAPAL 2000 GT (STUDI KASUS PELABUHAN MUNSE SULAWESI TENGGARA)

Sea transportation is the main transportation used by residents in the islands. The development of marine transportation facilities is expensive to support these activities. Therefore, several alternatives are needed to streamline construction costs, one of which is the construction of a pier using a mooring dolphin. The purpose of this study is to calculate the structural strength of the mooring dolphin with a ship capacity of 2000 GT at Munse Port, Southeast Sulawesi Province. Structural analysis is carried out by analyzing pile capacity and joint displacement analysis. The calculation of the strength of the pile elements at the pier was analyzed using the SAP 2000 program. For soil which is modeled as an elastic support, the ability to support the load depends on the magnitude of the modulus of subgrade reaction from the soil. Embedded pile modeling is modeled with a nonlinear spring force. The results of the analysis by analyzing the capacity of piles with dimensions of 508 mm with a thickness of 12 mm resulted in a capacity ratio of 0.72. The results of the analysis of joint displacement in service or operational conditions are 37.09 mm and in earthquake conditions, they are 13.01 mm.

Transmission of Stresses in Pavement Layers Subjected to Earthquake Excitation

A reinforcement interlayer retards the development of cracks in the asphalt overlay by absorbing the stresses induced by both heavy traffic and underlying cracking in the old pavement. The experimental work in this study used laboratory model tests to developed an understanding of the behaviours of sand used as a subgrade under earthquake condition and the its effects of this on flexible pavement and base course layer. The sand subgrade layer has a thickness of 600 mm and the base course was set to 200 mm; the asphalt layer was prepared as a panel with dimensions of 300 x 300 x 50 mm, representing the surface layer. These layers were then tested under the influence of earthquake loading with different frequencies 0.5, 1 and 1.5 Hz. The tests were performed in two parts without adding a geogrid, and with geogrids in the centre of the base layer and between the base and sand layer. Stresses in all three layers are measured using stress sensors, and the displacements of the asphalt layer were measured using two laser displacement sensors. The results for the tests on pavement layers showed that, the stress recorded in models reinforced with geogrids was higher than that seen in unreinforced models, while the displacement was decreased by adding the geogrid in the layers at all three frequencies. When the geogrid is laid between the base and sand layer, the stress in the subgrade layer also lower than that in the base and asphalt layers.

The unit price of building changes to different design of seismic importance factors

The design of a building needs to accommodate the potential for earthquake risk. The function and utilization of buildings are closely related to the risks caused by earthquakes, especially for people using the building. In the design process, load changes due to utilization are accommodated through an index value called seismic importance factors (SIF). The application of the index will directly affect the structural dimensions of a building. Thus, the amount of building unit price (BUP) needed will also vary according to the function of the building. This research was conducted to analyze changes in BUP on some seismic importance factors in a building structure design. Changes in unit prices were explained by applying the price index approach in the form of the building unit price index (BUPI). This study was applied to a six-story building using reinforced concrete structures and following earthquake load conditions in four seismic zones in Aceh Province. The BUPI was analyzed based on comparing a building unit price (BUP) to the reference BUP that was set from the building designed with the lowest SIF index in the initial seismic zone. The analysis results show that the increase in the SIF indices will potentially increase the BUP to 6 % (IDR. 105,061.25) for SIF 1.00 to 1.25, while the increase in costs for SIF 1.25 to 1.50 was 4 % (IDR. 84,507.32). The BUPI values have clearly explained how the building unit price increases following the SIF indexes increase.

Finite element analysis of a zoned earth dam under earthquake excitation

This paper presents a finite element analysis of a zoned earth dam under the effects of earthquake conditions. GeoStudio software, and in particular the sub-programs SEEP/W and QUAKE/W were used, and the earthquake used in the analysis was an Iraqi earthquake that occurred in Ali Al-Garbi, within the Missan governorate. The Haditha dam section data was used for the hypothetical dam construction. The total length of length of this dam is 9,064 metres, which includes 8,875 metres of earth fill, and the maximum height of the dam is 57 m. The shell is constructed from a mix of sand and gravel, with an average particle diameter ranging from 0.24 to 16.7 mm. Three different properties were used to represent the core material, and each of these properties was analysed under three different heads of water on the upstream side. The results showed that high water levels at the upstream side of the dam heavily influenced the analysis results. The water flux, water conductivity, and peak displacement all increased with the increase in the water level upstream of the dam. For a water level equal to 152 m, the maximum values of water flux, water conductivity, and maximum displacement were 3.951 × 10-3 m2/sec, 6.654 × 10-3, and 2.03 m, respectively, while where the water level was 143 m, these values were equal to 2.023 × 10-3 m2/sec, 3.995 × 10-3, and 1.85 m, respectively. Further analysis showed that the water flux, water conductivity, and peak displacement increased with increases in the void ratio and degree of saturation of the clay core material, moving from 2.023 × 10-3 to 3.951 × 10-3 m2/sec for water flux, from 3.995 × 10-3 to 6.654 × 10-3 for water conductivity, and from 1.85 to 2.03 m for peak displacement.

Solutions for Foundation Systems Subjected to Earthquake Conditions

Soil–structure interaction plays an important role in dynamic behaviour of a foundation under combined static and seismic loadings. This paper describes a few case histories with field studies of deeply embedded bridge foundations to showcase the earthquake induced lateral effects using finite element framework. Rigorous dynamic approach with detailed numerical analysis for large diameter pile foundation and pseudo-static approach for rigid caisson foundation presented in this study demonstrated the functionality of foundation systems in seismic conditions. Efficacy of barrettes over piles as a cost-effective foundation solution in high-rise buildings has also been discussed by obtaining higher resistance under static condition. Finally, an analytical methodology considering three-dimensional passive wedge developed in front of the rigid caissons is presented for estimating the ultimate soil resistance under seismic condition. Closed-form expressions to determine seismic passive earth pressure coefficient and its distribution along caisson length for different embedment ratio have been explained here that can be adopted in practice to analyse foundation systems subjected to earthquake condition.

STUDI ANALISIS PENANGANAN LONGSOR PADA SLOPE TIMBUNAN YANG TEGAK (STUDI KASUS LONGSORAN DI JALAN TOL RUAS SEMARANG – BAWEN KM 426+600)

Heavy rains that flushed most of the Semarang area have resulted in the slope on the edge of the Semarang - Bawen STA.426 + 600 toll road experiencing landslides and eroding part of the shoulder of the road. A slope stability analysis is needed to determine the slope safety factor at the research location which can model it according to the original conditions in the field so that there is an approach condition in the analysis results and makes it easier to model its handling, one of which is by using manual formulas.In this analysis, the input data for soil parameters were used, including: cohesion, c; angle of shear in soil, 𝜑; slope angle, 𝛼; and soil volume weight, 𝛾. From the results of the analysis of slope stability with cantilever wall reinforcement, it is considered safe because the foundation soil stress that occurs is smaller than the allowable stress of the soil, namely (664,556 <1496,219) for normal conditions and (464,951 <1496,219) for earthquake conditions. SF to shear under normal conditions is greater than the required SF (3,738> 1,5). SF to shear earthquake conditions is greater than the required SF (3.036> 1.2). The SF against rolling under normal conditions is greater than the required SF (2,068> 2). SF against rolling earthquake conditions greater than the required SF (1.912> 1.5).Keywords: Semarang - bawen toll road, landslides, slope analysis

The Effect of Key Design Parameters on the Global Performance of Submerged Floating Tunnel under Target Wave and Earthquake Excitations

This study presents a practical design strategy for a large-size Submerged Floating Tunnel (SFT) under different target environments through global-performance simulations. A coupled time-domain simulation model for SFT is established to check hydro-elastic behaviors under the design random wave and earthquake excitations. The tunnel and mooring lines are modeled with a finite-element line model based on a series of lumped masses connected by axial, bending, and torsional springs, and thus the dynamic/structural deformability of the entire SFT is fully considered. The dummy-connection-mass method and constraint boundary conditions are employed to connect the tunnel and mooring lines in a convenient manner. Wave- and earthquake-induced hydrodynamic forces are evaluated by the Morison equation at instantaneous node positions. Several wave and earthquake conditions are selected to evaluate its global performance and sensitivity at different system parameters. Different Buoyancy-Weight Ratios (BWRs), submergence depths, and tunnel lengths (and mooring intervals) are chosen to establish a design strategy for reducing the maximum mooring tension. Both static and dynamic tensions are critical to find an acceptable design depending on the given target environmental condition. BWR plays a crucial role in preventing snap loading, and the corresponding static tension is a primary factor if the environmental condition is mild. The tunnel length can significantly be extended by reducing BWR when environmental force is not that substantial. Dynamic tension becomes important in harsh environmental conditions, for which high BWR and short mooring interval are required. It is underscored that the wet natural frequencies with mooring are located away from the spectral peaks of design waves or earthquakes.

Influence of pore pressure on natural frequency wandering of structures under earthquake conditions

Temporary seismic frequency wandering of buildings during and after seismic events has often been observed and has not yet been investigated, in particular with regards to the effects of the pore pressures generated within the soil mass. This paper investigates the influence of delayed soil response on the observed temporary natural frequency wandering induced by seismic actions. The focus is on the pore pressure generation within the soil mass and its impact on the observed wanderings. Our findings show that the natural frequency of the system is lower shortly after the seismic event, but it returns to its initial value with time, as expected from measurements. The results are shown in terms of generated pore pressure, its dissipation over time, reduced mean effective pressure and nonlinear stress strain behaviour, all of them affecting the temporary changes in natural frequencies. Parametric studies on the influence of soil permeability, soil density and type of input motion are presented. Finally, a time history inclusive of an aftershock is investigated to explore the different soil-structure interaction mechanisms occurring during the main event and the subsequent aftershocks.

A Novel Contact Tunnel Profile Monitoring System: Concept and Application

The displacement of the cross section directly reflects the stress state and stability of the surrounding rock and structure, so the monitoring of it is essential during the construction and operation of the tunnel and underground engineering, particularly under the conditions of earthquake and other geological disasters. This paper introduces a new contact tunnel profile monitoring system (TPMS) in detail that uses a tilt sensor and a displacement sensor as data acquisition devices. According to the relation between the sensing physical quantity and displacement change, the displacement calculation formulas of the tunnel cross section measuring points based on the two-dimensional plane coordinate system were deduced, and in order to eliminate the actual installation and positioning deviation of the monitoring system, the method of obtaining the optimal monitoring plane and converting coordinates of the measuring points was proposed, thus establishing the theoretical basis for the application of the TPMS. With the Beishan exploration tunnel (BET) in China as the test platform, the TPMS was successfully applied for long-term monitoring. The application experience showed that the TPMS can realize continuous monitoring, automatic collection and transmission of the monitoring data, remote access whenever necessary, without affecting the transportation in the tunnel, and high accuracy, which reaches 0.01 mm. This system provides a new simple and effective method with good generality and applicability for the deformation monitoring of the tunnel and underground engineering.

PERFORMANCE OF SEISMICALLY ISOLATED BUILDINGS USING SFP BEARING: AN APPLICATION IN VIETNAM

At present, the use of structural vibration control technology in the design of earthquake resistant in Vietnam is very limited. In this paper, a performance evaluation of using single friction pendulum bearing (SFP) for earthquake resistant buildings with earthquake conditions in Vietnam is presented. A one-dimensional (1-D) model of a 5-storey building subjected to earthquakes was developed for time history analysis. Accordingly, the model is analyzed in two configurations: with and without SFP bearing. The ground acceleration data was selected and scaled to fit the design acceleration in Hanoi determined from TCVN 9386:2012. The dynamic responses of the two configurations was evaluated in detail. It is shown that the seismically isolated configuration can reduce the base shear up to 90%. A significant decrease in the inter-story drift and absolute floor acceleration was also observed.

Seismic Response Time-Frequency Analysis of Bedding Rock Slope

According to the potential disaster points of rock bedding slope with weak structural plane along the Sichuan Tibet railway, the shaking table test of earthquake simulation is designed and carried out. The acceleration response and displacement response of slope under different input earthquake conditions are monitored, and the HHT method is mainly used to analyze the seismic response of slope. The results show that the rock bedding slope shows obvious and under the action of seismic waves of different intensities. With the increase of the amplitude value of the input earthquake, the elevation effect and the surface effect gradually weaken. When the amplitude of seismic wave reaches 0.9g, the movement inconsistency of slope on both sides increases, and the slope is gradually separated from the main body of the slope, resulting in slope instability. The characteristics of the seismic signal in time - frequency domain can be better described by the Hilbert-Huang transform. In the time domain, the energy is mainly concentrated in 2-6s and 12-15s, and excellent frequency band is concentrated between 5hz-20hz and 30-80hz. With the increase of elevation, the former increases and the latter decreases. In addition, the change of the peak value of the marginal spectrum can clearly show the development process of the earthquake damage inside the slope. At the height of 100cm, the inflection point can be seen obviously in the slope. It shows that the damage occurs at the height of 100cm, and the degree of earthquake damage near the slope is stronger than that inside the slope. The recognition results of marginal spectrum are in good agreement with the experimental results.

Time-domain coupled dynamic simulation for SFT-mooring-train interaction in waves and earthquakes

In this study, Submerged Floating Tunnel (SFT)-mooring-train coupled dynamics is solved in the time domain to investigate their dynamic and hydro-elastic interactions under wave and earthquake excitations. The SFT is modeled by the rod-FE (finite element) theory, and it is connected to mooring lines through dummy-connection-mass and linear and rotational springs. A 3D rigid-multi-body dynamic model is developed for train dynamics that consists of seven rigid bodies. The tunnel-train interaction is taken into consideration based on the wheel-rail correspondence assumption and the simplified Kalker linear creep theory. The developed computer simulation program is validated through comparisons with commercial programs and published results when possible. In the case of earthquake-induced dynamics of the coupled system, the effects of soil conditions, tunnel length, mooring interval, seismic-wave propagation, and seaquake are investigated. The magnitudes of the SFT downward motions induced by the moving train are small compared with the motions induced by earthquakes. The earthquake causes transient SFT responses especially at their lowest wet natural frequencies while high-frequency motions are induced by seaquake effect. Structural damping and seismic propagation play an important role in dynamic responses. The interaction of the tunnel and moving train is also evaluated for various train speeds in terms of the derailment and offload factors and riding-comfort criterion. For the given SFT and train designs, the offload factor and riding-comfort criterion can slightly exceed their limits at certain earthquake conditions with the speed as high as 70 m/s, which can be adjusted by reducing train speed.