Earthquake Action Research Articles

Analysis and Application of Double Steel Plate Concrete Composite Shear Wall in the R&D Building of Zhanjiang Bay Laboratory

The R&D Building of Zhanjiang Bay Laboratory is a high-rise structure with multiple irregular items exceeding the specification limit, employing a steel frame-shear wall structural system. The outer frame consists of square steel tube concrete columns and solid-web steel beams, while the core shear wall uses a double steel plate concrete composite shear wall. This paper employs the architectural structural calculation software YJK-EP to perform a dynamic elastic-plastic time-history analysis under rare earthquake action. The shear and bending resistance of the shear wall at the maximum shear force and bending moment are checked to meet the requirements of the “Technical Specifications for Concrete Structures of High-rise Buildings”. The maximum inter-story displacement angle meets the requirements of the “Code for Seismic Design of Buildings”. The double steel plate concrete composite shear wall Wall-1, connected to a large-span and heavy-load transfer truss, was verified under significant seismic action using the ABAQUS software. The results indicate that Wall-1 can meet the design target requirements under major earthquake conditions. Finally, a dynamic nonlinear analysis method was employed using MIDAS-GEN software to study the structure’s anti-progressive collapse performance. The results show that under seven different scenarios, the maximum rotational angle of the remaining structural horizontal members is 2.02°, far less than the limit set by GSA, indicating that a progressive collapse did not occur. In the scenario where the corner column is removed, both the maximum shear and bending moment values for Wall-1 are far below its shear and bending resistance capacities, satisfying the load-bearing requirements. The removal of the corner column has a significant impact on the displacement of the columns on the same level nearby, with the peak displacement change rate reaching 702.65%.

Seismic Behaviors of Prefabricated Reinforced Concrete Shear Walls Assembled with a Cast-in-Place Vertical Joint

The seismic performance of prefabricated reinforced concrete shear walls is a key point in the safety of the whole assembly structure under earthquake actions. In this study, six specimens of reinforced concrete shear walls were assembled with a cast-in-place vertical joint with a straight, L, or convex shape. The specimens were tested using a low cyclic loading test under an axial compression ratio of 0.2 or 0.3. The stress process, failure pattern, and hysteretic curve of each specimen were measured. Combined with a numerical analysis using the finite element method, the variations in the bearing capacity, stiffness degradation, ductility, and energy dissipation capacity of the tested specimens were analyzed. Results showed that all specimens failed in a shear pattern without an obvious failure phenomenon along the vertical joint. The hysteresis curves exhibited an obvious pinch phenomenon and good deformation ability. The seismic behavior decreased in sequence for the shear walls assembled with a cast-in-place vertical joint with a straight, L, or convex shape, while a higher axial compression ratio improved the bearing capacity of the shear walls. The shear wall with an L-shaped vertical joint had similar seismic behavior to that with a straight vertical joint, but the shear wall with a convex vertical joint exhibited a decrease of 8.5% and 10.9% in bearing capacity, 18.2% and 1.2% in ductility, and 13.1% and 20.6% in energy dissipation, respectively, under an axial compression ratio of 0.2 and 0.3. The bearing mechanisms of shear walls with different vertical joints are explained with the numerical analysis of the stress vector maps of concrete and the stress cloud maps of reinforcements at different stress levels.

Cyclic behavior and numerical study of PRC coupling beam with steel truss floor slab

The coupling beam with small span-to-depth ratio is prone to brittle shear failure under the action of earthquake, so it can not play its role as the first line of defense against earthquake. Therefore, this paper proposes a method for calculating the shear bearing capacity of PRC-connected beams with reinforced truss floor plates. A more rational calculation model should be adopted based on its mechanical mechanism. In this study, ABAQUS finite element software is utilized to explore the parameters of PRC-connected beams with steel truss plates, including the span-to-height ratio, reinforcement ratio of the internal steel plate, diameter of upper and lower chord bars, and diameter of abdominal bars. The analysis shows that the span-to-height ratio, steel plate ratio and concrete compressive strength have a significant effect on the seismic behavior of PRC coupling beams with steel truss floor slab. Based on the softened tension-compression bar model combined with the multi-strip model, the theoretical calculation method of the shear capacity of PRC connected beams with steel truss bearing plates is derived. The results of comparison test and simulation verify the accuracy of the calculation results, and provide a design basis for the engineering application of PRC connected beams with steel truss floor plates.

Failure probability of a liquid storage tank with three-dimensional base-isolation under earthquake action

Liquid storage tanks are widely used in the petrochemical industry, but the fixed-base liquid storage tanks have a high probability of earthquake damage, therefore, the research on isolation and damping control of liquid storage tank has attracted wide attention. Based on the dual control requirements of the seismic response of the liquid storage tank itself and the liquid sloshing wave height, a new type three-dimensional isolation bearing suitable for the liquid storage tank has been obtained. Taking into account the material nonlinearity, the liquid-solid coupling, and the liquid sloshing characteristics, a numerical calculation model of the new type three-dimensional isolated liquid storage tanks is established by ADINA. The seismic vulnerability of the fixed-base and the new type three-dimensional isolated liquid storage tanks are investigated, the failure probability of liquid storage tank under different limit states is discussed, and the annual average failure probability and design life failure probability of the liquid storage tank are finally analyzed. The results show that, the probability of fully damaged wave height and axial stress of fixed-base liquid storage tank is 72.0% and 49.6% respectively, under the 9 degree rare earthquake. Compared to the fixed-base liquid storage tank, the failure probability of the axial compressive stress, hoop stress, and liquid sloshing wave height of the isolated liquid storage tank is significantly reduced, but the displacement of the isolation layer becomes the most easily damaged dynamic response. Besides, the new type three-dimensional isolation can significantly reduce the annual average failure probability and the design life failure probability of the liquid storage tank.

Estimation of wave velocity and analysis of dispersion characteristics based on wavelet decomposition

Due to the complexity of the crustal medium and stratigraphic boundaries, seismic waves typically exhibit attenuation and dispersion after propagation through the medium. By studying the regularity of seismic wave dispersion, soil layer information can be extracted. Current spectral decomposition techniques take less account of signal filtering processing of seismic waves, and the complexity of the stratigraphy tends to reduce the accuracy of dispersion analysis. Based on the above, a new method for calculating the dispersion characteristics of a site from surface and downhole ground vibration recordings is proposed, which is simpler than the spectra analysis of surface waves (SASW) method and eliminates the need for multiple pickups and additional equipment. This method is based on wavelet decomposition and seismic wave filtering, and a numerical simulation example is established to verify the effectiveness of the method. Then, the records of the Tohoku earthquake on March 11, 2011 are used as actual strong earthquake examples for filtering and dispersion analysis. Finally, it is concluded that the seismic wave dispersion analysis method based on wavelet decomposition can effectively filter and analyze seismic waves in specific frequency bands.

A new seismic input method for layered soil and its application in dynamic response analysis of underground structure

With the acceleration of urbanization, the seismic problem of underground engineering is getting more and more attention. In actual projects, foundation soils often show a complex layered distribution. In terms of layered ground motion input, this study propose a new layered ground motion input method based on infinite element boundary, which avoids the application of spring and damping elements on the boundary nodes of layered soil, simplifies the ground motion input process and has high accuracy at the same time. To reasonably simulate the nonlinear seismic response of layered soil, the equivalent linear model of soil is nested to Mohr-Coulomb (MC) model to establish the viscoelastic-plastic model. The seismic response analysis procedure of the soil-structure monolithic model considering the nonlinearity of the layered soil is given. On this basis, the soil-structure nonlinear seismic response analysis is carried out to study the effect of burial depth on the seismic performance of underground structures, taking a project as an example. The results show that with the increase of the burial depth of the structure, the top–bottom displacement difference shows a change law of first increasing and then decreasing under the action of earthquake; From the internal force response, the most unfavorable burial depth exists due to the joint influence of the burial depth of the structure and the characteristics of the layered soil; For the same burial depth condition, the dynamic bending moment caused by the seismic load action is larger compared to the shear response.

A predictive model for determination of sand liquefaction potential based on energy method

The prediction of liquefaction potential of sand under earthquake action is a complicated problem in civil engineering. In this study, gene expression programming (GEP) was used to establish the relationship between the capacity energy required to trigger sand liquefaction and several major parameters. By collecting 85 experimental data and six main parameters, a GEP model was established and the empirical prediction equation was obtained. Three statistical indices were used to evaluate the performance of the GEP model and 11 other existing capacity energy models. The results show that the coefficient of determination (R2), mean absolute error (MAE) and root mean squared error (RMSE) values of all datasets predicted by the GEP model are 0.924, 0.061 and 0.087, respectively. While the R2, MAE and RMSE values of all datasets of the 11 existing capacity energy models are 0.510–0.777, 0.149–0.468 and 0.196–0.653, respectively. It can be concluded that the proposed GEP model has the potential to accurately predict the capacity energy required to trigger sand liquefaction.

An Analytical Approach to the Traces of Settlement of the City of Sakarya from Antiquity to the Present

According to the known history of the world, the first communities generally chose natural cave environments on the edges of sea, lake and stream for settlement and spread towards the interior of the land over time. These communities have learned to move to higher elevations in order to be protected from phenomena such as water rises and ground movements in the natural flow of the earth. It is an ironic situation that these natural phenomena that shape the earth are called disasters today. In this context, the aim of the study is to question Sakarya River, which was formed as a result of an earthquake action, and along this river, the settlement decisions of the cultures that established living spaces within the borders of the city of Sakarya by mapping them chronologically from the Paleolithic period to the present day with an analytical approach. Within the scope of the study, the effect of the earthquake phenomenon in the city, from the ancient times to the present, while the settlement decisions are taken, will be discussed and the effect of this information on the current settlement decisions of the city will be questioned. Types of analysis specific to the method developed within the scope of the study are; systematic literature review, epigraphic documents, aerial and archive photographs, maps. While reading the traces of settlement in the historical process, the study makes the structural constructs created by the cultures visible through the icons created within the scope of the study.

A three-dimensional numerical simulation method for seismic nonlinear response of underground structure in liquefiable site and analysis of structural damage

Considering the effect of dynamic interaction between liquefiable soil and underground structure, simulating the nonlinear seismic response of underground structures through simple, convenient, and reliable 3D numerical model is still a great challenge at present. A three-dimensional numerical simulation method for dynamic response of underground structure in liquefiable site is proposed based on the centrifuge shaking table test designed for a subway station buried in liquefiable interlayer site carried out in the previous period. The numerical model takes into account the characteristics of sand prone to large deformation after liquefaction and the nonlinear characteristics of the contact between saturated soil and structure. The typical numerical calculation results are compared with the experimental results to verify the correctness of the numerical model, and the extended analysis of the structural damage is carried out, which visually shows the damage distribution of structure under different functional states after earthquake. The analysis of structural damage shows that the junction position of middle column and longitudinal beam is more prone to tensile damage under the horizontal earthquake action; while after considering the horizontal-vertical seismic effect, the middle column will produce additional compressive damage due to the vertical inertia force, and the end of middle column should be paid attention to in seismic design.

Research on Vibration Damping Analysis of UHV Suspended Converter Valve Model

The UHV (ultra high voltage) suspended converter valve is hinged to the top of the valve hall, so the equipment has a long structural period, the suspended converter valve is displaced under the action of earthquakes, and the valve tower is susceptible to damage due to interaction with the important equipment connected to it. The high cost, large size, and weight of the real type of UHV suspended converter valve make it difficult to carry out shaking table test studies of the real type of equipment. In this paper, a numerical model of a UHV-suspended converter valve scaling device and its damping structure model are established, and a damping analysis study with damping at the top of the converter valve model is carried out. The analysis showed that the maximum displacement of the converter tower was 136.3 mm under the action of a 0.4 g El-Centro earthquake. With horizontal damping at the top, the maximum displacement of the converter tower is 62.9 mm, a reduction of 53.9% compared to the undamped case. This study proposes a vibration damping design for UHV suspended converter valve, laying the foundation for subsequent shaker test studies of the scaled-down model vibration damping structure of the UHV suspended converter valve and the productization of vibration dampers for the equipment.

Structural health monitoring with UAV

In recent years, the use of drones to monitor various types of smart constructions has attracted more attention. Unmanned Aerial Vehicles (UAV) have a number of potential benefits over manual methods for Analyzing construction due to their permit scalable, quick, and affordable solutions to tasks that would otherwise be unsuitable for individuals who are subject to fatigue and measurement uncertainty. In order to better understand how drones can be used in dam monitoring and construction for situation assessment, early warning, and image processing, the current study is studying this topics. High resolution Ierial images that captured by UAV is used to detect the cracks in the dam body structure. Drone-shot images are analyzed by using MATLAB software in order to assess the crack in the dam body and make the correct maintenance.The finite element program Geostudio is undertaken to evaluate a complete numerical analysis of the dam to find out the cause of cracks in the dam body and give solutions to prevent these cracks from happening again depending on the outcome results. This study is applied under two cases seismic and static condition. The results of FEM model concluded that cracks starts to appear at slope change point at downstream and in upstream at dam heel during earthquake action. The current work shows that using drones in dam monitoring is a very effective and fast way to detect cracks in the dam body.

Ảnh hưởng của điều kiện biên tới phản ứng địa chấn của cẩu hàng container

Container crane structure plays a crucial role in loading and unloading goods from a container ship to harbors. In any case, a breakdown of the container crane would harm the economy of a country. The modern crane is bigger to satisfy the demand of the owner; therefore, it is less stable under seismic excitation. Engineers often encounter an issue for choosing the boundary condition of the simulated model of the container crane as the legs can be uplifted or derailed under strong earthquakes. In this case, the simple work of pinned boundary condition can be replaced by the elastic-no-tension element between the structure and the ground. In this way, the leg base is free to move in vertical direction, and its vertical reaction reduces to zero. The objective of this paper is to evaluate the seismic performance of a container crane by the time history acceleration analysis using two different base supports, i.e., pin and elasticno-tension supports. Firstly, horizontal response spectra of actual earthquakes are adjusted by scaling the amplitude of each ground motion to coincides with a specific target spectral acceleration at the fundamental period of the container crane and then determined the scale factor. Afterwards, the ground motions are generated based on the scale factor, and they are used as input data for dynamic analysis by time history method. Two cases of target spectral accelerations will be determined to evaluate the dynamic responses of structure for uplift and no uplift phenomenon. Some response characteristics, i.e., total base shear and portal drift, are investigated. From that, the results show that the elastic-no-tensions supports are suitable for simulating the real behavior of the container crane when it is analyzed under high seismic excitation.

Evolution of excess pore water pressures around monopiles subjected to moderate seismic loading

The sustained growth of the offshore wind sector is leading to the construction of offshore wind farms in highly seismic regions of the world. Hence, a large proportion of the potential sites may be exposed to liquefaction risk. Monopiles are directly affected by this phenomenon given their preference as a support system for offshore wind turbines over other foundation types. This paper includes a comprehensive study of the lateral response of monopiles against the combined action of earthquake induced liquefaction and environmental loading using centrifuge modelling. The experimental setup was designed to compare the amount of excess pore pressure generated within the soil adjacent to the monopile with and without operational wind/wave loading. The results revealed higher accumulation of excess pore pressure in the non-laterally loaded case, and significant differences in the amount of excess pore pressure recorded in the windward and leeward sides of the monopile in the laterally loaded scenario. In addition, the study provides data on the rotation experienced by monopile supported offshore wind turbines in liquefiable soils.

Application of improved genetic algorithm in the optimal design of seismic parameters of rail vehicle

Abstract This paper first considers the seismic parameter model of rail vehicles with rail constraints and investigates the mechanism of beam-rail interaction under earthquake action. The computational parameters of rails, main girders, and piers are optimized using analytical and finite element methods during earthquake action. Finally, the NSGA-II genetic algorithm is improved and applied to optimize the seismic parameters of rail vehicles, and seismic damage indexes evaluate the damage to rails and vehicles. The results show that by optimizing the seismic parameters of rail vehicles, the track damage is lower than the median value of μ [μ 1 = 1.03404, μ 2= 1.2013] under the same earthquake intensity, and the probability of lateral damage to vehicles is reduced by 0.15. Applying the improved genetic algorithm proposed in this paper can effectively improve the seismic performance of rail vehicles and provide some theoretical support for the design and safety of rail vehicles.

Research on the design of ballastless track in the subgrade section of high-speed railway in high earthquake-intensity area

According to the characteristics of complex terrain and bad geological conditions in the southwest mountainous area of China, it is proposed that cast-in situ double-block ballastless track with layers and blocks structure should be adopted preferentially in the subgrade section of high-speed railway, which is conducive to the construction, prolongation of service life and maintenance of the ballastless track. Based on the finite element model, the dynamic performance, structural strength and stability of double-block ballastless track under high earthquake-intensity action are analyzed. The analysis shows that the relative displacement between the base slab of ballastless track and the subgrade may occur under 9 degree earthquake action. A new CRTS double-block ballastless track structure with a concave-convex structure between the base slab and the subgrade is proposed in the subgrade section, and its additional stress and relative displacement under earthquake are analyzed. The results show that the additional stress and relative displacement of the new ballastless track structure and the subgrade under 9- degree earthquake actions are small, which meet the high stability requirements of high-speed railway.

Seismic Performance and Calculation Method of Precast Reduced Beam Section Connection

To prevent brittle damage and improve the post-earthquake rapid repair capability of beam–column connections, a precast reduced beam section (PRBS) connection joint that can be rapidly repaired under earthquake action was proposed in this study. Four specimens, including a repaired specimen, were subjected to a quasi-static test to investigate the seismic performance and repair ability of the connection. Seismic performance indices such as the failure mode, hysteresis curve, skeleton curve, strain distribution, and ductility were obtained through observations and analyses. The results indicated that the novel connection exhibited superior load-bearing, energy dissipation, and rotation capacities, compared to the welded flange-bolted web and traditional bone-weakened connections. This novel connection effectively relocated the plastic hinge to alter the failure mode and prevent brittle damage. Additionally, rapid post-earthquake repair was achieved by replacing the dog-bone-style splice section, maintaining a high load-bearing capacity and seismic performance. Finite element (FE) models were established to analyze the mechanical behavior of the specimens, and a parametric analysis was conducted to study the influence of different parameters on the load-bearing capacity of the connection. Based on the experimental and FE analysis results, the possible yield and failure modes of the connection were analyzed, and a calculation method for the bearing capacity of the PRBS connection was proposed. A comparative result demonstrates that the proposed calculation method can accurately predict the load-carrying capacity of a connection.

Augmenting the seismic performance of unreinforced masonry loess - Cave with composite materials through shaking table testing

To improve the seismic performance level of existing masonry buildings, a composite reinforcement method of polypropylene packaging strap (PP) and cement was used to design unreinforced masonry loess-cave (URML) structural models with a scale ratio of 1:4, and shaking table tests were conducted on these models. Reinforcement measures were used to reinforce the earthquake-damaged URML structure, and vibration table tests were conducted again on the reinforced URML structure using the same loading procedure. A comparative analysis was conducted on the failure modes, acceleration response, displacement response, torsional effect, and energy dissipation capacity of two model structures under earthquake action, and their seismic performance was evaluated. The experimental results show that the overall seismic performance of the URML structure is poor, with a low natural frequency, large displacement response, and obvious torsional effect. It is close to collapse under the PGA = 0.8 g earthquake action; the model (RML) structure strengthened with PP strap and cement combination has an increased natural frequency, smaller displacement response compared to the unreinforced model, and it has a significantly controlled crack propagation. The destructive effect of the structural torsion effect is significantly reduced. Under the PGA = 0.8 g earthquake, only slight damage occurs to the water mud surface layer. The combination of the PP strap and cement reinforcement method can effectively delay the stiffness degradation of URML structures under strong earthquake action, increase the damage resistance of the structure, and effectively improve the overall seismic resistance of such masonry structures.

Effect of Biaxial Loading Path on Seismic Performance of RC Bridge Piers with Corrosion Damage

In recent years, the deterioration of seismic behavior for reinforced concrete (RC) bridges due to reinforcement corrosion has received increasing attention. Many studies have been performed to explore the seismic capacity of corroded piers by applying uniaxial cyclic loading. However, the uniaxial seismic responses of corroded piers cannot accurately reflect the true structural response influenced by corrosion condition and real multidimensional earthquake action. Pointing at this problem, in this study, the seismic performance of corroded pier columns suffering biaxial lateral cyclic loadings is investigated by conducting comprehensive numerical analyses. First, a fiber-based numerical model is built and verified by the cyclic experiment results of two RC pier columns under different displacement loading patterns and corrosion levels. Then, three corrosion levels and five uniaxial and biaxial displacement protocols are used in the verified numerical models. The simulation results show that the ultimate force, deformation capacity, and dissipated energy of the piers are significantly influenced by corrosion degrees and biaxial loading patterns compared with the uniaxially loaded uncorroded piers. The phase lag between the biaxial displacement trajectory and biaxial force trajectory has three stages: a small-range fluctuation stage, a wide-range fluctuating and rise stage, and a wide-range fluctuating and decrease stage. The RE pattern is the most detrimental pattern, which leads to the fastest damage accumulation of the same-level corroded bridge piers.

Analytical solution for dynamic responses of offshore wind turbines supported by pipe pile in radially heterogeneous soil

Offshore wind turbines (OWTs) are subject to the combined action of dynamic environmental loads including wind, waves, and earthquake loads. This paper proposes an analytical solution for the dynamic response of OWTs supported by pipe pile in heterogeneous viscoelastic soil. The analytical model accounts for various interactions that affect OWTs dynamic response. The pipe pile-internal soil is calculated by utilizing the Helmholtz method, the pipe pile-external soil is calculated by utilizing the transfer matrix method, the pipe pile-wave is evaluated by utilizing the diffraction wave theory, and the tower drum-wind is calculated by utilizing the Bernoulli method. The dynamic responses of the pipe pile and tower are established by enforcing the boundary conditions of the displacement continuity and stress equilibrium. The developed analytical solution is degenerated into simplified analytical solutions under various conditions, which was validated by comparing its predictions with the results of available numerical and analytical solutions. The validated simplified solution is then utilized investigate the effects of some critical parameters on OWTs response. The results show that the OWTs response under the combined action of earthquake, wave and wind loads is strongly affected by the presence of water and soil inside the pipe pile, soil radial heterogeneity.

Dynamic characteristics of deposit slope under coupled action of earthquake and rainfall

Earthquakes and rainfall both have great influence on the stability of slopes. However, their coupled effects on slope stability are rarely investigated in detail. In this paper, large scale shaking table tests were carried out to investigate the dynamic characteristics and instability mechanism of slope subjected to the coupled action of rainfall and earthquakes. Results of the analyses show that rainfall significantly affects the slip surface within the slope subjected to a subsequent earthquake. It is hypothesized that as the soil effective stresses depend on the pore pressures, the suctions within the slope are reduced when rainfall infiltrates the slopes. When the shaking occurred first, cracks due to ground motion promote subsequent rainfall seepage, reducing the suctions and consequent reduction in the slope stability. The results obtained in this study can provide a theoretical basis for the stability evaluation and design of slope in the areas, which are greatly influenced by earthquakes and rainfall.