Multi-dimensional Earthquake Research Articles

Horizontal shaking table tests on a four-story prototype structure using multi-dimensional earthquake isolation and mitigation devices

Three-dimensional isolation system (3DIS) has been increasingly applied to civil structures with small height-width ratios, but is rarely employed in the multistory and high-rise buildings due to the lack of efficient control strategy for the rocking effect. In this paper, a simplified analysis model of 3DIS was established firstly to bring insights into the coupled motion mode caused by the rocking effect, and the influence of damping ratio and height-width ratio on the modal frequency was revealed. Then, aimed at weakening rocking motion and improving the seismic isolation efficiency, a novel multi-dimensional earthquake isolation and mitigation device (MEIMD) was proposed, and both the design composition and design principle were given in detail. To validate the effectiveness of MEIMDs, a full-scale four-story frame with a height of 13.05 m and a weight of 70 tons was produced for horizontal shaking table tests. The experimental results indicated that after adopting MEIMDs, the first-order modal frequency was 1.7 Hz, with 68% decrease compared with that of the prototype structure, and the first-order modal damping ratio was above 0.23, about eight times that of the prototype structure. Moreover, the horizontal peak acceleration was significantly decreased for each floor with a maximum reduction of 49%, while the maximum horizontal displacement and rocking response were obviously lower than the limit value specified by building codes. Therefore, the MEIMDs can not only efficiently isolate the earthquake energy, but also ensure the sufficient dynamic stability of the system. This study sheds light on the real coupled horizontal-rocking response of the base isolation system with MEIMDs, and can promote the development and application of 3DIS in multistory and high-rise buildings.

Shaking table tests on seismic performance of a five-story reinforced concrete frame structure with MoS2 sliding bearings and steel dampers

The seismic performance of friction isolated structure is greatly affected by the friction coefficient, and the combination of low friction material and limit device is an available option. Via the Motion State module simulating the friction conditions and the Bouc Wen model describing the restoring characteristic of the steel dampers, a single-degree-of-freedom model was established to investigate the influence of the friction coefficient and limit stiffness on the isolation effect. Then, for the evaluation of the seismic performance of the proposed isolation system with molybdenum disulfide (MoS2) sliding bearings and steel dampers, the shaking table tests of a 1/5 scaled five-story reinforced concrete frame structure model, subjected to three ground motions with different peak ground acceleration, were implemented to obtain the isolation layer drift, absolute acceleration, inter-story shear and damage energy of the structure under the testing conditions of free sliding, limited sliding, multi-dimensional seismic excitation, and top additional layer sliding. It is found that the ideal friction coefficient for sliding isolated structure is 0.03–0.07, and the corresponding reasonable elastic stiffness of steel dampers is (0.2–0.5) Ks that is the stiffness of the structural standard story, and the proposed MoS2 sliding bearing presents remarkable low-friction characteristic with a friction coefficient of 0.04–0.05. The appropriate steel dampers can reduce the isolation layer drift without obviously increasing the acceleration. The low-frequency components in the ground motion significantly increase the isolation layer drift, while the high-frequency components cause the superstructure acceleration to show a K-shaped distribution along the height. Moreover, the proposed isolated system can be effectively used for structural protection under multi-dimensional earthquakes, the sliding additional layer on the roof can be considered as the second defense line in the structural seismic design, and the seismic energy the superstructure bears can directly estimate the seismic isolation effect that is consistent with the analysis result of dynamic response.

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.

Cyclic Behavior of Rectangular Bridge Piers Subjected to the Coupling Effects of Chloride Corrosion and Bidirectional Loading

The degradation of seismic performance for RC bridge piers induced by chloride corrosion has previously been studied by treating the earthquake as a unilateral cyclic loading. Such studies do not consider the true response of the pier under the joint effect of corrosion damage and real multi-dimensional earthquake action. Thus, in the present study, the cyclic behavior of rectangular bridge piers subjected to the coupling effects of chloride corrosion and bidirectional loading was numerically investigated. First, the corrosion-induced deterioration of material mechanical properties is introduced. Second, the numerical model of two corroded piers is built and validated with the test results in the literature. Then, the time-dependent biaxial seismic performance of a rectangular bridge pier under the circular-shaped (CS) biaxial displacement pattern, square-shaped (SS) biaxial displacement pattern, uniaxial displacement in the X-direction (UX) pattern, and uniaxial displacement in the Y-direction (UY) pattern is analyzed using the validated model. The simulation results conclude that the trajectory of biaxial loading paths and corrosion levels significantly influence the peak force, deformation capacity, and dissipated energy of the piers. The biaxial loading path effect for the corrosive pier includes two stages with different biaxial force trajectory characteristics. Compared with the uncorroded pier, the corrosion level of 13.7% and biaxial loading induces up to a 40% reduction in strength and a 54% decrease in the residual ultimate displacement of the corroded pier. For the same corrosion degree, the dissipated energy under the SS biaxial displacement path is the largest among the four loading paths.

Dynamic analysis of three-directional vibration isolation and mitigation for long-span grid structure

With the rapid development of the long-span space structures, some seismic isolation methods of ordinary buildings are also gradually applied in these structures. The special feature of the long-span space structure is that the vertical seismic property cannot be ignored, in addition to considering the horizontal property under multi-dimensional earthquake action. This study proposes a novel multi-dimensional earthquake isolation and mitigation device (MEIMD) consisted of viscoelastic core bearing and viscoelastic damper. This device provides certain stiffness that can satisfy the load-bearing capacity requirement of the structure and strong energy dissipation ability in the horizontal and vertical seismic directions. A mathematical model is presented to characterize the mechanical behavior of the MEIMD. The device is installed at the top of the support column, which creates a seismic isolation layer between the column and the upper grid model. The shaking table tests of the long-span grid structure with and without MEIMD under horizontal seismic excitations of various intensities were carried out. The experimental results showed that the acceleration response peak value on the isolation structure was significantly reduced. The novel device has a good horizontal isolation effect on the grid structure. To determine the vertical and three-direction seismic isolation properties of the MEIMD on the grid structure, finite element models of the long-span grid structure with MIEMD and without MEIMD were established for dynamic time history analysis. The numerical results revealed that the dynamic responses of the isolation grid in horizontal and vertical directions have been decreased compared to the non-isolated structure.

Seismic response of a mid-story-isolated structure considering soil–Structure interaction in sloping ground under three-dimensional earthquakes

A mid-story-isolated structure is developed from a base-isolated structure. Mid-story-isolated structures located in sloping ground have become a research hotspot in recent years. It is important to consider the soil–structure interaction (SSI) effects and multi-dimensional earthquakes on these structures. This paper established a model of the mid-story-isolated structure considering SSI in sloping ground. An elastic–plastic time history analysis was carried out under the one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) earthquakes. Under 3D earthquakes, the traditional 2D isolated bearing has limited damping capacity. Therefore, two kinds of 3D isolated bearings were designed. Results show that the seismic response of the mid-story-isolated structure considering SSI in sloping ground can be amplified compared with that of the mid-story-isolated structure without considering SSI. The seismic response of the structure under 3D earthquakes is more significant than that under 2D earthquakes and 1D earthquakes. For the two kinds of 3D isolated bearings, the minimum reduction rate of tensile and compressive stress is about 46% compared with that of the traditional 2D isolated bearings. When the 3D isolated bearings are used, the stress of the soil foundation decreases, which is more conducive to the stability of the soil foundation.

Nonlinear dynamic analysis of the deep-water bridge piers under combined earthquakes and wave actions

When the Stokes fifth-order wave is utilized to study the wave force of large-diameter bridge piers, the iterative method is usually utilized to solve the transcendental equations and then solve the wave parameter wavelength, coefficient and wave number. The solving process is particularly complicated, and the ratio of water depth and wavelength is generally assumed to be 0.1–0.15, which is suitable for shallow water depths and has not been investigated for deep water depths. In this study, the wave force and action point of the large-diameter rectangular section bridge pier under Stokes fifth-order wave action are derived, and the range of Stokes wave number is derived when the deep water level is constant. Combined with the functional analysis of transcendental equations, a program for calculating the Stokes fifth-order wave parameters is derived, and the approximate solution of the coefficient and wavelength of the Stokes wave is accurately and quickly solved. The dynamic nonlinear analysis of super deep-water large-diameter bridge pier under combined multi-dimensional earthquake and nonlinear wave action is investigated. It is found that nonlinear waves can significantly increase the dynamic response of deep-water bridge pier structure, but under combined wave and earthquake loadings on the deep-water bridge pier structure, and earthquakes play a dominant role. The influence of resonant waves and common linear waves on the dynamic response of large-diameter bridge piers in deep water depth is quite different. Resonant waves have a significant influence on the displacement response and stress response of deep-water bridge piers. When under two-dimensional earthquake and resonant wave independent loadings, the influence on the dynamic response of deep-water bridge pier structures is insignificant. When under combined earthquakes and waves loadings on the deep-water bridge pier structure, earthquakes play a significant role.

Development and Application of a Platform for Multidimensional Urban Earthquake Impact Simulation

Earthquakes can be devastating to cities. Therefore, accurate and efficient simulation of the potential seismic damage to buildings has become an indispensable part of worldwide efforts to mitigate earthquake hazards. Precise simulation results can highlight potential seismic damage and serve as a reference in urban development and for planning post-earthquake rescue operations. In urban areas, simulation of the structural dynamic response during an earthquake is key for planning an appropriate emergency response. Multidimensional visualization of the effects of earthquakes is a popular technique in current earthquake simulation research. In the present study, a dynamic multidimensional simulation method was developed for analyzing the impact of an earthquake on buildings. This method involved conducting three-dimensional (3D) dynamic analysis of data from a seismic capacity database. Polygonal models and seismic capacity data were used in a high-performance computing process to calculate the seismic response of each building in an urban environment. On the basis of the calculations, a platform was developed for multidimensional urban earthquake impact simulation (MDUES). The developed MDUES platform enables analysis of the impact of long-period earthquakes, simulation of the 3D seismic responses of buildings, and visualization of the disaster risk and earthquake impact in a specified area. In summary, simulation of structural seismic responses in an urban setting necessitates a careful examination of the characteristics of ground and building motion, and the results of this simulation can provide a crucial reference for city planning, post-earthquake rescue operations, and seismic damage assessments.

Performance-based global reliability assessment of a high-rise frame-core tube structure subjected to multi-dimensional stochastic earthquakes

Performance-based global reliability assessment of a high-rise frame-core tube structure subjected to multi-dimensional stochastic earthquakes

Simulation analysis on continuous collapse resistance of assembled building structure under multi-dimensional earthquake

Under the multi-dimensional earthquake, the random damage of the building column structure is large, and the analysis of the continuous anti collapse performance of the building structure is limited. Therefore, the simulation analysis of continuous anti collapse of assembled building structure under multi-dimensional earthquake is proposed. Through the analysis of the undamaged structure of the building, it is found that under the action of multi-dimensional earthquake, if the long side column, corner column and inner column of the building structure are damaged, it may lead to the collapse of the assembled building structure. The test results show that the continuous collapse caused by inner column demolition is the strongest, followed by long central column, corner column demolition will not cause the continuous collapse of the building structure.

Applications and Evaluation of the IRIS Earthquake Browser: A Web-Based Tool That Enables Multidimensional Earthquake Visualization

Abstract The Incorporated Research Institutions for Seismology Earthquake Browser (IEB; see Data and Resources) is a web-based tool that enables anyone to query an earthquake database composed of over five million events recorded over the past 50 yr. The IEB visitor can query on earthquake magnitude, depth, timing, and location and can visually display the results in 2D map view or as an interactive pseudo 3D view. The user can toggle features such as plate tectonic boundaries, terrain or satellite mapping, and zoom to place the results in a geologic or geopolitical context and add visual appeal. To better understand who visits the IEB and why, to include information on demographics and how users perceive the IEB functionality and ability to meet their needs, we conducted a pop-up user survey on the IEB from 25 January to 21 February 2018. We received 495 useable responses from 58 countries, with 40% of the total respondents from the United States. The largest demographic consists of interested citizens who are 55 yr of age or older and have a high school education. We also find that visitors come to the IEB to learn about earthquakes for two main reasons: for their own personal knowledge or because expanding their knowledge is important to their research or work in a professional context. We also find a dramatic increase in survey respondent activity following the 16 February 2018 M 7.2 Oaxaca, Mexico, earthquake, with many respondents interested in finding more information about recent earthquake events that affect them or their family. Our observations indicate that users are successful and satisfied with the ease of use and amount of time spent on the IEB to find answers to their questions about earthquakes. The most beneficial feature of the IEB as identified by survey respondents is the spatiotemporal visual display of real earthquake data.

Collision in the expansion joint effects on the seismic behavior of large-scale aqueduct

ABSTRACT Under earthquake, two beams of the aqueduct’s expansion joint may collide; thus, this will endanger the safety of the structure and even lead to girder falling accident. Quite a few studies of this issue use the simple one-dimensional model, but little takes the collision phenomenon under the action of multi-dimensional earthquake into account. According to the Contact-Impact Problems of large-scale aqueduct under earthquake action between the adjacent beam segments, a three-dimensional contact analysis model has been used to simulate the collision phenomenon. And the response of aqueduct structure collision one-dimensional seismic and multidimensional earthquake is compared; the results reveal that the three-dimensional frictional contact impact finite element model can simulate the real aqueduct structure under seismic pounding effect.

Simulation Analysis On Continuous Collapse Resistance Of Assembled Building Structure Under Multi-Dimensional Earthquake

Under the multi-dimensional earthquake, the random damage of the building column structure is large, and the analysis of the continuous anti collapse performance of the building structure is limited. Therefore, the simulation analysis of continuous anti collapse of assembled building structure under multi-dimensional earthquake is proposed. Through the analysis of the undamaged structure of the building, it is found that under the action of multi-dimensional earthquake, if the long side column, corner column and inner column of the building structure are damaged, it may lead to the collapse of the assembled building structure. The test results show that the continuous collapse caused by inner column demolition is the strongest, followed by long central column, corner column demolition will not cause the continuous collapse of the building structure.

Dynamic Performance and Anti-earthquake Analysis of Cable-stayed Arch Bridge

The strength, stiffness, and stability check calculations and the effect of earthquakes should be considered in the design of cable-stayed arch bridges with collaborative systems. This study aims to investigate the dynamic performance and structural response of cable-stayed arch bridges under seismic action. The space analysis model is enhanced of the Xiang Feng River Bridge using finite element software Midas Civil, whose lower foundation considers the effects of piles and soil. Firstly the vibration period, vibration frequency, and modal characteristics are computed, thus the dynamic performance is summarized of the bridge. Then, a proper seismic wave is selected according to engineering conditions and in terms of three orthogonal directions: inputting the adjusted El Centro seismic wave, considering Rayleigh damping, and calculating via the Newmark method. Furthermore, a time-history response analysis under the action of one-dimensional and multidimensional earthquake is performed. Lastly, the results of the response analysis is compared and the behavior characteristics of arch bridge is summarized under seismic action. The results show that the transverse stability problem of bridges is prominent and should be the focus of antiearthquake fortification, the inclined cable tower of this bridge is not conducive to the earthquake resistance of the structure in comparison with the vertical cable tower. and the influence of horizontal and vertical earthquake actions should be considered in antiearthquake designs.

An improved multidimensional modal pushover analysis procedure for seismic evaluation of latticed arch‐type structures under lateral and vertical earthquakes

SummaryPushover methods for seismic assessment of buildings under multidimensional earthquakes have been studied and retrofitted. However, these current methods are not suitable when applied to widely adopted arch‐type structures characterized by strong geometrical nonlinearity and coupling effects. An improved multidimensional modal pushover procedure with two‐stage analyses is proposed for seismic evaluation of latticed arches. Taking overall multidimensional response into consideration, modal stiffness of the equivalent single‐degree‐of‐freedom system is derived, and its capacity curve is determined during the first‐stage analysis. To provide a deformation profile with algebraic signs of response retained, the second‐stage analysis is conducted using the pushover load pattern derived from modal displacement superposition. The objective of the improved procedure is to overcome the drawback of the conventional modal pushover method, which describes the capacity curve resorting to base shear and roof displacement, and that of quadratic combination rules which eliminate the sign reversals of response. To validate its serviceability, nodal displacements and element stresses, as well as the yielding members, of two typical latticed arches are calculated. Through comparative analysis, the results by the improved procedure exhibit good agreement with those by response history analysis. Additionally, this procedure demonstrates great superiority over the conventional method for its satisfying accuracy.

Seismic Damage Model of Bridge Piers Subjected to Biaxial Loading Considering the Impact of Energy Dissipation

The large degradation of the mechanical performance of hollow reinforced concrete (RC) bridge piers subjected to multi-dimensional earthquakes has not been thoroughly assessed. This paper aims to improve the existing seismic damage model to assess the seismic properties of tall, hollow RC piers subjected to pseudo-static, biaxial loading. Cyclic bilateral loading tests on fourteen 1/14-scale pier specimens with different slenderness ratios, axial load ratios, and transverse reinforcement ratios were carried out to investigate the damage propagation and the cumulative dissipated energy with displacement loads. By considering the influence of energy dissipation on structural damage, a new damage model (M-Usami model) was developed to assess the damage characteristics of hollow RC piers. The results present four consecutive damage stages during the loading process: (a) cracking on concrete surface, (b) yielding of longitudinal reinforcements; (c) spalling of concrete, and (d) collapsing of pier after the concrete crushed and the longitudinal bars ruptured due to the flexural failure. The damage level caused by the seismic waves can be reduced by designing specimens with a good seismic energy dissipation capacity. The theoretical damage index values calculated by the M-Usami model agreed well with the experimental observations. The developed M-Usami model can provide insights into the approaches to assessing the seismic damage of hollow RC piers subjected to bilateral seismic excitations.

Study on the performance of lead rubber bearing considering vertical force correlation

To study the vertical force correlation of the lead rubber bearing, the pseudo static test of the bearing has been carried out, and the test shows that when the vertical force is small, the pre-yield stiffness and the yield shearing force of the bearing are increased with the increase of vertical force, while the post-yield stiffness is decreased with the increase of vertical force. When the vertical force is increased to a certain extent, the bearing parameters may be stable. The bearing parameter has been identified by the least square method, and then, the quantitative relation between the bearing parameter and the vertical force could be obtained. The calculation model and the motion equation of the isolation structure under the multi-dimensional earthquake excitation have been established, and the parameter iteration of bearing obtained from the test has been used for solving the motion equation, from which the seismic response of an isolation structure has been made available when the vertical force of the bearing is considered. The calculation of engineering examples shows that the displacement of the isolation layer will increase after the consideration of the vertical force correlation of the bearing, and the displacement of the upper structure will have a larger overall shifting.

Seismic performance of a two-story unsymmetrical reinforced concrete building under reversed cyclic bi-directional loading

Abstract Reinforced Concrete (RC) buildings are often subjected to multi-directional loadings under earthquake ground motions due to the structural configuration and inherent multi-dimensional earthquake motions. Previous researches have been focused on individual components with a few bi-directional tests. Essentially no research data, including experiment and simulation, exists for an entire unsymmetrical building under reserved cyclic bi-directional loading conditions. To provide a context for this complex problem, a test on a two-story reinforced concrete building subjected to bi-directional reversed cyclic loadings was performed at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan to examine the torsional effect caused by the eccentricity of the building plan layout. The study was undertaken as part of an international collaboration project between the National Center for Research on Earthquake Engineering (NCREE), Taipei, Taiwan and the University of Houston (UH), Houston, Texas, USA. This paper presents the experiment and simulation of the building specimen. First, the test program is summarized including the descriptions of the test specimens, the test setup, the loading method and the experimental results. Then the numerical analyses conducted using a finite element analysis (FEA) program Simulation of Concrete Structure (SCS) developed at UH are presented. The predicted results turned out to agree very well with the experimental data. The results obtained from this research can be used to correlate analytical tools, new design methodologies and the capacity of design codes of such complex structures.

Experimental and theoretical study on a building structure controlled by multi-dimensional earthquake isolation and mitigation devices

Multi-dimensional earthquake isolation and mitigation device (MEIMD) is a newly developed structural vibration control device. First, the horizontal and vertical property tests are performed to study the influences of excitation frequency and displacement amplitude on the dynamic properties of the MEIMD. In order to accurately describe the nonlinear characteristics of the device caused by the complex viscoelasticity, an integrated mathematical model based on fractional-derivative equivalent standard solid model is then proposed. Next, the horizontal and vertical shaking table tests on a 1/5-scale three-story steel frame structure equipped with and without the MEIMDs are presented, respectively. Finally, a dynamic response analysis method considering the nonlinearity of the MEIMD is proposed to analyze the dynamic responses of the controlled structure. The analysis results show that the MEIMD can provide excellent horizontal isolation ability, and good vertical isolation performance can be achieved through selecting reasonable pre-pressure value of the springs. The proposed mathematical model and dynamic response analysis method can effectively describe the nonlinearity of the MEIMDs and the structure with MEIMDs.

Multidimensional Seismic Control by Tuned Mass Damper with Poles and Torsional Pendulums

Due to the eccentric characteristics and the torsional excitation of multidimensional earthquakes, the dynamic response of asymmetry structure involves the translation-torsion coupling vibration and it is adverse to structural performance. Although the traditional tuned mass damper (TMD) is effective for decreasing the translational vibration when the structure is subjected to earthquake, its translation-torsion coupled damping capacity is still deficient. In order to simultaneously control the translational responses and the torsional angle of asymmetry structures, a new type of tuned mass damper with tuned mass blocks, orthogonal poles, and torsional pendulums (TMDPP) is proposed. The translation-torsion coupled vibration is tuned by the movement of the mass blocks and the torsional pendulums. According to the composition and the motion mechanism of the TMDPP, the dynamic equation for the total system considering eccentric torsion effect is established. The damping capacity of the TMDPP is verified by the time history analysis of an eccentric structure, and multidimensional earthquake excitations are considered. The damping effect of the traditional TMD and the TMDPP is compared, and the results show that the performance of TMDPP is superior to the traditional TMD. Moreover, the occasional amplitude amplification in TMD control does not appear in the TMDPP control. The main design parameters which affect the damping performance of TMDPP are analyzed.