Vertical Earthquake Research Articles

Quantification and parametric analysis of large overhang RC planar frames subjected to horizontal and combined horizontal–vertical earthquake loading

Quantification and parametric analysis of large overhang RC planar frames subjected to horizontal and combined horizontal–vertical earthquake loading

Analyzing Vertical Earthquake Vibrations and Moving Vehicle Loads for Structural Health Monitoring and Vibration Suppression in Bridges

The design of bridges often overlooks the vertical component of earthquakes or considers it of secondary importance, despite compelling evidence indicating specific structural damage caused by primary earthquake waves. Conversely, during the operational phase, the combined influence of ground motion and moving loads from vehicles can significantly impact the structural health monitoring (SHM) of bridges. This study aims to evaluate the simultaneous effect of vertical earthquake vibrations and moving vehicle loads on simply supported bridges. The research employs a practical methodology based on the eigenfunction expansion method to analyze change of deflection due to the effect of these concurrent forces under seven different earthquake records. It is shown that within a realistic range of vehicle mass and velocity, the average of changing the maximum deflection at the mid-span of the main beam (denoted as M_n) reaches up to 163% under various scenarios. Subsequently, the seismic parameters influencing this phenomenon are identified through a statistical analysis of set of 100 different earthquake records with unique features. A linear regression equation is presented to predict the M_n based on the earthquake specific properties. Additionally, to control the vertical vibration of bridge systems, a novel vibration suppression system utilizing steel pipe dampers is introduced, and its reliability is examined across a broad spectrum of bridge flexural rigidity. The results indicate that the system's efficiency depends on M_n and the soil type of the bridge construction, enabling a reduction in structural sections (up to 27%) while achieving the same maximum target deflection in the initial state. This efficiency leads to a more economical design solution, emphasizing the potential benefits of the proposed system for practical application.

Effects of wind-wave-current-earthquake interaction on the wave height and hydrodynamic pressure based on CFD method

Wind-wave-current interaction is a phenomenon which is present in many practical engineering situations and vertical earthquakes may have significant influence on the hydrodynamic pressure of seawater in regions of active seismicity. This study is devoted to probe the wave height and hydrodynamic pressure of seawater caused by the joint wind, wave, current and earthquake action based on computational fluid dynamics (CFD) method, where a homogeneous multiphase model based on the noncompressible Reynolds Averaged Navier-Stokes (RANS) equation and the k-ε turbulence model implemented in ANSYS-Fluent code was used. First, a two-dimensional (2D) numerical flume excited by wind, wave, current and earthquake loadings was established through the secondary development of a user-defined function (UDF). Subsequent, effects of wind-wave interaction and wind-wave-current interaction on the wave height and hydrodynamic pressure of seawater were investigated. Finally, effects of wave-earthquake interaction and wave-current-earthquake interaction on the wave height and hydrodynamic pressure of seawater were investigated. The nonlinearity of seawater under joint wind, wave, current and earthquake action was also studied.

Farklı Zemin Sınıfına Göre Elde Edilmiş Düşey Elastik Tasarım Spektrumlarının Yapı Davranışına Etkisi ve K.Maraş Deprem Verileri ile Karşılaştırılması

In practice and theory, many types of reinforced concrete slabs are used, such as beamed, beamless, and ribbed slabs. Beamed floors are connected to the columns by means of beams, and their vertical and horizontal loads are transferred to the columns through these beams. Therefore, beams are accepted as an important structural element by earthquake experts and many formulas and approaches have been developed in terms of horizontal and vertical load effects that occur in order to transfer the load transfer to the elements as desired. In this study, beam shear forces that occur under the influence of vertical earthquakes at the i and j ends of the beams of a fictional building whose floors are modeled according to the rigid diaphragm assumption in the ETABS were investigated. In this study, the shear forces that occur in the beams of a fictionally designed building under the effect of vertical earthquakes, and the floors carried by the beams are examined by designing with the assumption of a rigid diaphragm. The structure is designed with 3 openings in the X and Y directions and each opening is equal and 5 m. The 5-storey building has been designed to have equal floor heights of 3 m. The structure was obtained by using parameters belonging to 5 different soil classes as ZA, ZB, ZC, ZD, ZE, and 5 different vertical elastic design spectrums represented by the abbreviations EZ_ZA, EZ_ZB, EZ_ZC, EZ_ZD were activated in the ETABS. Seismic station coordinates numbered 4631 in K.Maras/Elbistan were used to obtain the parameters to be used in obtaining the vertical elastic design spectral of the structure. These coordinates were selected in order to compare the i and j end shear forces of the beam with the previously obtained beam i and j ends shear forces by influencing the Mw:7.6 Elbistan earthquake recorded by the seismic station to the building. Since the structure is symmetrical in both X and Y directions, the results obtained from beams B2, B3, B5, B19 represent the beam shear forces occurring at the i and j ends of all beams of the structure. As a result, it has been seen that the highest values of beam i and j end shear forces, obtained by affecting both the vertical elastic design spectral and the data of the vertical component of the Elbistan Mw:7.6 earthquake, were obtained on the 5th floor, which is the top floor of the building. The structure showed similar behavior among the different vertical elastic design spectral, and the highest value was obtained for each vertical elastic design spectrum at the 5th floor. Among these vertical elastic design spectral, the EZ_ZC spectrum gave the highest value at the 5th floor of the building. When the EZ_ZC vertical elastic design spectrum beam i and j end shear forces are compared with the beam i and j end shear forces of the vertical component data of the Elbistan Mw:7.6 earthquake, it is seen that the difference is not significant. It has been seen that the beam i and j end shear force value of the spectrum is higher than the shear force value.

Vehicle–Bridge Interaction Dynamic Analysis of Continuous Rigid Frame Composite Box Girder Bridge with Corrugated Steel Webs under Seismic Excitation

To study the vehicle–bridge interaction (VBI) of highway bridges under seismic excitation, a vehicle–bridge couple analysis method based on Ansys is proposed. The 1/2 vehicle model and space beam element model were established to analyze the VBI response of Lanzhou Xiaoshagou bridge. The self-excited excitation of the system is represented by road surface irregularity randomness, while the external excitation is represented by an earthquake. The impact of seismic types, seismic direction, seismic intensity, vehicle speed, and road surface irregularity on the bridge vibration under the vehicle–bridge coupling during an earthquake is thoroughly analyzed. The results reveal that the type of earthquake significantly influences the dynamic response of the bridge, showing a minimum difference of 31.4%. The intensity of the earthquake is positively correlated with the dynamic response of the bridge. Longitudinal and vertical earthquakes have a more noticeable effect on the bridge’s vertical vibration compared to lateral earthquakes. The ratio of the bridge response under vertical or longitudinal seismic excitation to the response of lateral earthquakes ranges from 1.50 to 26.61. Vehicle speed, road irregularity grade, and randomness have a negligible impact on the dynamic response of vehicle–bridge interaction under an earthquake, accounting for less than 3%. These findings indicate that the analysis of earthquake-bridge vibration can simplify the VBI analysis for continuous rigid frame composite box girder bridges with corrugated steel webs under seismic conditions.

Seismic Response Analysis of Multi Span Hyperbolic Brick Arch Thin Shell Structure

The research objective is to investigate the multi-span hyperbolic brick arch thin-shell structure located in Changleyuan, Baoji City, Shaanxi Province. The study utilizes on-site dynamic testing and finite element numerical simulation methods to analyze the dynamic characteristics of the thin-shell structure and its seismic response under various seismic waves and directions. The simulation results indicate the following findings: Vertical earthquakes cause more severe damage to structures compared to horizontal earthquakes. Bidirectional seismic excitation has a greater impact on the structure than unidirectional and three-dimensional seismic excitation. The obtained results provide a scientific basis for the seismic protection, reinforcement, and repair of this multi-span double-curved brick arch thin-shell structure.

The effect of high-speed railway train on the seismic response of bridge under earthquakes

This study aims to discuss the effect of high-speed railway train on the seismic response of bridge girder under earthquakes especially pay attention to the possible response reduction to the bridge caused by vehicle, utilizing experimental and simulation methods. A 1:10 scale model for the train-track-bridge system was built and a high-speed train running test platform based on shaking table array was constructed for the seismic loading test at varying running speed. To account the effects of different earthquake characteristics, earthquakes under the four types of site soil in the far-field and near-field were selected. The vehicle was modeled in two kinds of ways to distinguish the effects of spring-mass vehicle and additional mass which means a vehicle was set with spring suspension and mass, while another with additional mass only. Through a large amount of numerical simulation dates to determine the distribution interval of specific reduction value caused by the vehicle under the earthquake. Results in running tests and numerical simulation indicate that the lateral acceleration of the bridge girder can be effectively reduced when the train is stationary. The reduced ratios were about 4%− 8% compared without train on bridges. As the speed increases, the response of bridge is generally intense and the reduction is also weakened. Similar reduction was not observed in the response of vertical earthquake excitations, and high-frequency earthquakes have adversely affected this kind of reduction. The main reason for the reduction of lateral seismic response of bridge girder in the presence of static vehicle can be attributed to the phase difference between vehicle and bridge caused by a mass damper-like action, and the additional mass cannot cause similar changes alone.

Evaluation of Steel Diagrid Structural System Under Near-Fault Earthquakes

ABSTRACTThe diagrid structural system has become popular in the construction of high-rise buildings in light of significant advantages over other structural systems. The present study explores the effects of the vertical near-fault earthquake component on the axial forces of diagonal elements in steel diagrid structures. Nonlinear time-history analysis was carried out using 11 near-fault earthquake records. A total of nine three-dimensional models of 12, 18, and 24 stories, each with diagonal angles of 45, 63.4, and 71.5 degrees, were designed and analyzed. Due to the three-dimensional modeling complexities of diagrid structures, a method was developed to transform three-dimensional models into two-dimensional ones. Finally, the scenarios with and without the vertical earthquake component were compared. It was found that the incorporation of the vertical earthquake component into the analysis of diagrid structures substantially influenced the axial forces of diagonal elements. This can affect the design load estimation of diagonal elements as the main components of a diagrid structure.

Evaluation of the effect of the vertical component of an earthquake on the seismic response of container cranes using the shake table test

In this study, the effect of the vertical component of earthquakes on the seismic response of a container crane was investigated by using the shake table test on a 1/20 scale container crane. The effect was investigated by comparing the seismic response of the container crane when subjected to the horizontal component of earthquakes versus the horizontal and vertical components of earthquakes. The seismic responses of the container crane were compared based on acceleration responses, displacements, and internal forces. The main findings of this study are as follows: (1) Vertical acceleration response increased when the vertical and horizontal components of earthquakes were used simultaneously. A maximum increase of 79% was observed for the vertical acceleration response at the trolley-boom girder. The horizontal acceleration response either increased or decreased. The maximum difference was 24% when the container crane was subjected to horizontal component earthquakes versus horizontal and vertical component earthquakes. (2) The horizontal displacements of the container crane increased or decreased under the simultaneous action of the horizontal and vertical components of the earthquakes. The maximum difference was 278% with regard to the derailment of the seaside legs. (3) The internal forces at the top of the lower legs were affected by adding the vertical component of the earthquakes. The maximum difference in the axial force response was 100%, while that of the bending moment was 24%. Therefore, the seismic response of container cranes should be analyzed with and without the vertical component of earthquakes to determine the most extreme case of the seismic response.

Numerical investigation of a proposed multidimensional isolator applied to large-scale domes subjected to earthquakes

A three-dimensional seismic isolation device that is effective in isolating both horizontal and vertical earthquake components has drawn the interest of researchers in recent years. This paper proposes a new three-dimensional isolator for large-scale dome structures, which is composed of a quintuple friction pendulum component and a stacked disc spring component in series in the vertical direction. The complex working characteristics of these components are investigated in detail. Numerical modeling methods are proposed to simulate this isolator for engineering application purposes, and the model accuracy is validated based on theory and experiments. Thus, the isolator is applied to a large-scale dome structure subjected to near- and far-fault ground motions. Numerical analysis shows that the proposed modeling methods can efficiently analyze the isolation performance of the isolator in a large-scale structure. The numerical results demonstrate that the isolator has excellent isolation performance not only for displacement and axial force demands but also for velocity and acceleration demands in all three directions. In addition, according to the comparative study of this paper, the isolation performance of the proposed isolator is better than that of other types of isolators under major earthquakes due to the adaptive sliding characteristics of the quintuple friction pendulum component and the flexibility of the stacked disc spring component prolonging the structural periods.

Seismic design and performance analysis of perforated rubber buffer layer in tunnel

Tunnels may be damaged under earthquakes, which has been observed by many earthquake events, and the buffer layer is proposed and widely investigated as a damping measure. The rubber is considered as a qualified buffer layer material because of its small elastic modulus and super elasticity, but its high price makes it difficult to apply in practical engineering. Therefore, four types of rubber buffer layers are proposed in this study, including the common rubber buffer layer and three types of perforated rubber buffer layers (PRBL), which can reduce the seismic damage and cost of tunnels. A pseudo-static method for calculating the seismic response of tunnels under horizontal and vertical earthquake motions is proposed and verified. Based on proposed pseudo-static method, a seismic design method for the buffer layer is present, and the proposed seismic design process is used to study the seismic mitigation performance of buffer layers. The initial design of the buffer layer under earthquake action E1 is carried out by pseudo-static method, and then the seismic mitigation performance is verified through dynamic time history analysis method under earthquake action E2. The earthquake action E1 and earthquake action E2 are the earthquake actions with short and long return periods of the engineering site, respectively. The results show that the common rubber buffer layer has almost no seismic mitigation performance, and the three types of PRBLs have good seismic mitigation performance. The type IV buffer layer is strip-shaped PRBL and the holes are along the longitudinal direction of the tunnel, and it has optimal seismic mitigation performance. The effects of vertical earthquake motion and peak ground acceleration (PGA) on the seismic mitigation performance of the buffer layer are studied. The results show that vertical earthquake motion has little effect on the seismic mitigation performance of different types of buffer layers. For different PGAs, the type IV buffer layer is able to efficiently decrease the peak internal force of secondary lining. The results also prove the validity of design method.

Stable node-based smoothed finite element method for seismic stability analysis of a square tunnel in cohesive-frictional soils

This paper presents a stable node-based smoothed finite element method (SNS-FEM) based on the upper theorem for stability analysis of a square tunnel in cohesive-frictional soils subjected to seismic forces and surcharge loading. The soil behavior is considered homogeneous Mohr-Coulomb with cohesion c, friction angle ϕ and unit weight γ. Using the pseudo-static approach, the horizontal kh and vertical earthquake acceleration coefficients kv are applied to the entire soil mass. Then, the square tunnel is subjected to horizontal and vertical surcharge loadings on the ground surface. The variations of the seismic stability numbers with the change coefficients kh have been investigated for different values of the cover depth-to-width ratio of the tunnel H/B, soil properties γB/c, and internal friction angle ϕ. Several numerical results of square tunnels have been investigated, showing that the SNS-FEM approach can demonstrate accuracy and efficient solutions. The seismic stability numbers results are presented in design tables and charts for engineers to use in the preliminary design stage of the square tunnel. Finally, the article investigates the effect of horizontal and vertical seismic acceleration components on the corrective coefficients of a square tunnel.

Seismic evaluation cylindrical concrete shells

Abstract The reasons for concrete roof shells’ apparent seismic resistance have been subject to limited research but they have been shown to be inherently resilient to earthquakes. Shells constructed of concrete exhibit high structural efficiency and can therefore be made very thin. As a result of their relatively lightweight nature, thin shell structures are implicitly resistant to earthquake forces. The shell structure is typically designed so that it performs optimally under gravity loads, which are carried mainly by membrane action over the shell surface. As earthquakes induce unexpected horizontal forces, concrete shell structures can be damaged by bending stresses. By studying 8 cm-thick concrete roof shells using parametric analysis, this research shows that small and midsized (span <30 m) thin concrete roof shells can indeed be intrinsically earthquake resistant. These structures have high geometric stiffness and low mass, which results in fundamental frequencies far higher than those of realistic seismic events. Under earthquake excitation, these characteristics result in elastic shell behavior, without exceeding the maximum concrete strength. A shallow shell exhibits greater stress in response to earthquake vibrations caused by the vertical components than by horizontal components. Further, by increasing the rise and curvature of large shells, the fundamental frequency increases and the damaging effect of vertical earthquake vibration is reduced. The aim of this study in general is to show the analysis and the effect of earthquakes on cylindrical concrete shells.

Dynamic Response Law and Failure Mechanism of Slope with Weak Interlayer under Combined Action of Reservoir Water and Seismic Force

The southwestern region of China is close to the Eurasian earthquake zone. Many engineering areas in southwestern China are affected by earthquakes and are close to the epicenter of earthquakes that occur in this region. During earthquakes, slopes with weak interlayers are more likely to cause large-scale landslides. In response to the low stability of slopes with weak interlayers in reservoir dam areas, the dynamic response law and failure mechanism of weak interlayered slopes under the combined action of reservoir water and seismic forces were studied through shaking table model tests and finite element numerical simulation software. The height of the water level and the size of the seismic waves were changed during these tests. The research results indicate that seismic waves are influenced by weak interlayers and are repeatedly superimposed between the weak interlayers and the slope surface, resulting in an acceleration amplification effect that increases by approximately 1.8 times compared to homogeneous slopes. Vertical earthquakes have a significant impact on the dynamic response of slopes, and their peak acceleration amplification coefficient can reach 0.83 times the horizontal peak acceleration. The stability of weak interlayers during earthquakes is the worst within the range of the direct action of reservoir water. The failure mode of a slope is as follows: earthquake action causes cracking in the upper part of the slope, and as the earthquake increases in intensity, and the infiltration of reservoir water intensifies, the cracks expand. The soft and muddy interlayer in the front section of the slope forms a sliding surface, and ultimately, the sliding failure forms an accumulation body at the foot of the slope. In reservoir dam areas, the stability of a slope is closely related to the engineering safety of the reservoir dam. Therefore, when a strong earthquake and the water level in a reservoir jointly affect a weak-interlayer slope, the slope is in the stage of plastic deformation and instability. The stability of the slope may be overestimated, and the slope is likely vulnerable to sliding instability, which needs to be monitored and treated.

Seismic damage characteristics of large-diameter shield tunnel lining under extreme-intensity earthquake

This paper investigates the damage pattern of the concrete lining in a large-diameter subsea shield tunnel under different seismic loading intensities. Based on the Shantou Bay (STB) Tunnel, a refined finite element (FE) model consisting of “1/2 + 1+1/2” liner-rings is established in the study. In addition, another FE model considering both the strata and lining is created to obtain the seismic displacement-time history, which is employed as the boundary conditions on the “1/2 + 1+1/2” liner-rings model. A whole-ring model is thereafter generated considering the segment details, adopting the Concrete Damage Plastic (CDP) constitutive assumption and artificial viscoelastic boundary. An improved reaction-displacement method based on the concept of the “equivalent layer” is proposed to consider stratum-structure interaction. Finally, two types of seismic intensities and three work conditions are employed to investigate the influence on lining segments and joint openings. The results show that: (i) the damage to the segment of the shield tunnel is mainly concentrated in the top and bottom of the arch and the outer area of the waist under seismic loading; (ii) the moment of a sudden change in the damage development trend and the joint opening is related to the peak response of seismic time history; (iii) the segments of the shield tunnel are dominated by vertical oval shape deformation under a horizontal earthquake, and dominated by horizontal oval shape deformation under a vertical earthquake; (iv) the area and level of lining damage increase with the development of the earthquake intensity.

Tectonics of the Solomon Sea Basin from Vertical Gravity Gradient and Seismic Data

AbstractThe Solomon Sea Basin is a Cenozoic back‐arc spreading basin within the convergence system of the Pacific and Indo‐Australian plates. Against the background of subduction polarity reversal, the current Solomon Sea Basin gradually formed a rhombic morphology with the subduction of the basin along the New Britain Trench and the Trobriand Trough. By analyzing the vertical gravity gradient, natural earthquake and seismic reflection data, this study determines the structural characteristics of the Solomon Sea Basin. It was found that the tectonics of the basin are characterized by the original expansion structure within the central part in addition to the structure induced by the latest subduction along the basin margin. The original spreading structure of the basin presented an east–west linear graben and horst controlled by normal faults during the basin expansion period. As a result of the subduction and slab‐pull of the Solomon Sea Basin, extensional structure belts parallel to the New Britain Trench formed along the basin margin.

Vehicle-bridge interaction and the tuned-mass damper effect on bridges during vertical earthquake excitation

Vehicle-bridge interaction and the tuned-mass damper effect on bridges during vertical earthquake excitation

Shaking table tests of base-isolated reinforced concrete frame by double friction pendulum bearings

The effectiveness of seismic isolation by friction pendulum bearings (FPBs) in protecting structural and non-structural components from damage was evaluated by shaking table tests. A base-isolated reinforced concrete frame model by double friction pendulum bearings (DFPBs) with 1/5 scale was considered in the experimental program. A non-isolated model was also tested for comparison. The models were subjected to ground motions with incremental earthquake intensities. This paper presents a comprehensive overview of the test results in terms of peak inter-story drifts, peak floor accelerations, floor acceleration response spectra, hysteretic behaviors, seismic responses of the DFPBs and damage mechanisms of the structures. The results demonstrated that the base-isolated system can effectively protect both structural and non-structural components even under earthquakes larger than maximum considered intensities. The residual displacements of DFPBs remained small after multiple inputs and showed no direct correlation with the maximum sliding displacement and earthquake intensities. The effects of vertical earthquake shaking on the displacement responses of DFPBs were negligible for the test model.

Dynamic stability of single-layer spherical reticulated shell structures under earthquake action

In past decade, earthquake disasters have seriously damaged nonstructural components, so it is very important to study their dynamic stability. However, the existing researches mainly focus on the dynamic stability of multistory and high-rise buildings, and there are still deficiencies in the analysis of dynamic stability of reticulated shell structures under earthquake action. This paper takes the 40 m span K8 single-layer spherical reticulated shell structure with practical engineering significance as the research object, we study its dynamic instability characteristics under earthquake action, and propose a dynamic stability judgment method. The influence of various parameters on the critical loads of emotional stability of reticulated shell structures is systematically analyzed, including the impact of horizontal seismic action, the vertical seismic activity, and the three-dimensional seismic movement, considering the influence of material elastoplasticity; the result of different seismic inputs, the effects of initial geometric imperfections; the effects of varying rise span-ratio. In this paper, to investigate the nonlinear time-history response analysis, we uses the finite-element package ABAQUS. We first analyze the rise-span ratio as the dynamic stability of 1/3 single-layer reticulated shell structure under the action of the El Centro (1940) earthquake to reveal the dynamic loss of reticulated shell structure under earthquake action stable feature. The practical method for determining the proposed dynamic stability has a clear physical meaning and a range of applications. Our findings highlight that the critical load for dynamic stability under horizontal earthquake action is significantly lower than vertical earthquake action, and the critical load is the lowest under three-dimensional earthquake action. Material elastoplasticity influences the critical loads for dynamic stability of reticulated shell structures under different ground motions. The critical load of dynamic stability of single-layer structures with a larger rise-span ratio is lower, while those with a smaller one is higher. The initial geometric defects of the structure should be considered in practical engineering applications. The reticulated shell structure with a larger rise-span ratio needs to consider the dynamic stability problem in the strong earthquake area.

Performance evaluation of a nonlinear energy sink with quasi-zero stiffness property for vertical vibration control

The advantages of nonlinear energy sink (NES) have been proven to effectively reduce vibrations in the horizontal direction. The application of NES devices to suppress vertical vibration is still at an early stage. In this study, a new type of NES that works in the vertical direction, where disc springs and viscous dampers are utilized to connect an additional mass with the primary structure, is proposed. The NES device can provide a cubic restoring force characterized by the quasi-zero stiffness (QZS) property. Initially, the equations of motion of the primary structure supplemented with NES were established. Then, the force and displacement transmissibility curves were obtained via the steady-state analysis for the NES-controlled, tuned mass damper (TMD)-controlled, and uncontrolled systems. Analytical results revealed that the targeted energy transfer (TET) property of the NES can absorb the kinetic energy within the operating range without amplifying the response in the lower and higher frequency ranges. In contrast, TMD is more efficient within the operating range. Finally, a practical large-span floor structure was adopted to compare the operating performance of NES and TMD. External vibration includes track-induced vibration, vertical earthquake, and human-induced vibration. Numerical results show that the NES performs better than traditional TMD in controlling the vertical response. Moreover, the addition of a NES device will not potentially amplify the response on some occasions.