Dynamic Seismic Response Research Articles

Analysis on seismic dynamic response and liquefaction area of tailings dam

Taking a tailings dam in Hebei as the research object, the dynamic response of the dam under action of flood and earthquake is simulated by using a finite element software, and the seismic dynamic responses of the dam with respect to acceleration, stress, displacement, liquefaction area and stability are analysed. The results show that the vertical acceleration increases with the height of the dam, the horizontal acceleration is gradually increasing from outside to inside. A larger horizontal and vertical displacement occurs at the 3/4 height of tailings dam. After considering the relative density of the tailings dam and drainage condition, all the three kinds of seismic waves cause a small range of liquefaction area. The stability of the tailings dam is calculated with Sweden Arc Method, showing dynamic stability safety factor is 1.257 when considering drainage, which is larger than code value, indicating the tailings dam is stable in the case of earthquake.

Seismic Damage Detection of Moment Resisting Frame Structures Using Time‐Frequency Features

To detect seismic damage of moment resisting frame (MRF) structures, a data‐driven method using the fractal dimension (FD) of time‐frequency feature (TFF) of structural seismic dynamic responses at measured stories is extended and refined. The TFF is defined as the real part of Gabor wavelet transform of translational interstory displacement, and FD is used to give a quantitative value to describe the calculated TFF. Static condensation method is first used to reduce the degrees‐of‐freedom (DOFs) of MRF and to express the rotational displacements using translational displacements. For linear MRF, the FDs of TFFs at all stories are the same using the definition of TFF and modal superposition principle. For damaged MRF with plastic hinges at the ends of beams and columns, the force analogy method is implemented to establish transformation matrix from plastic hinge rotations to translational interstory inelastic displacements. Due to the sparseness of the transformation matrix, plastic hinges only generate interstory inelastic displacements, which are low‐frequency contents, in the vicinity of plastic hinges. Correspondingly, the FDs of TFFs of interstory displacements with inelastic component are different from the FDs of TFFs of the interstory displacements that do not contain inelastic component. A numerical simulation on a 16‐story MRF was conducted. The simulation included 10 cases such as no damage or linear structure, plastic hinges in single‐story beams, plastic hinges in single‐story columns, plastic hinges in single‐story beams and columns, and plastic hinges in multiple story beams and columns. The robustness to measurement noise was also investigated. The seismic damage detection results demonstrated that the proposed method was capable of locating the stories where the plastic hinges occurred.

Large-Scale Shake Table Test on Behavior of Underground Structure with the Curved Portion During an Earthquake

Underground structures are generally considered to have high seismic performance and expected to play an important role as a base for reconstruction even after a destructive earthquake. Rigidity changing points, such as jointed and curved portions of underground structure, where localized deformation and stress is supposed to be generated, are ones of the most critical portions in terms of seismic performance of underground structure. Because the underground structure in a mega-city functions as a network, local damage could lead to fatal dysfunction. Accordingly, rigidity changing points and their surrounding area could significantly influence the resiliency of urban functions, and it is indispensable to evaluate their seismic performance and dynamic responses during earthquakes. The responses of rigidity changing points and their surrounding area to earthquakes have been tried evaluating by using large-scale numerical analyses, there is no case available where the responses have been measured in detail. For this reason, it is difficult to verify the validity of the results of such evaluations.In light of the above, the shake table test was conducted at E-Defense using a coupled specimen of soil and underground structures to obtain detailed data, especially on the localized responses around rigidity changing points during the earthquake. Based on the data obtained, the behavior of the underground structure with a curved portion at the time of an earthquake was analyzed comprehensively. As a result of the analysis on the test data, it is found that there is a strong correlation between the localized deformation of the curved portion of the tunnel and the displacement of the surrounding ground. In addition, it is necessary to conduct a three-dimensional seismic response analysis not only around the rigidity changing point but also in wider area.

Time-Frequency Analysis of Seismic Wave Propagation across a Rock Mass Using the Discontinuous Deformation Analysis Method

To investigate the wave (including P-wave and S-wave) propagation across a rock mass, the seismic discontinuous deformation analysis (DDA) method is used, and a time-frequency analysis of the DDA simulation results is performed in this paper. First, compared with the theoretical solution, the correctness of the DDA to simulate the seismic wave propagation across both the interlayer and interface is validated. Second, the propagation effects of the seismic wave across the jointed rock mass are studied, showing that the joint stiffness, joint spacing, and joint number have different effects on the attenuation of seismic waves. Last, to analyze seismic wave propagation across a rock mass, the engineering site of the underground cavern complex of the Dagangshan hydropower station in southwest China is used as a typical case study. A number of valuable results are obtained by time-frequency analysis; an obvious topographic amplification effect and a joint abnormal area are found. From the analysis of the time-space effect, it may be concluded that the relative displacement of the rock mass is easily encountered under earthquake, which adversely affects the stability of the engineering site. The spectrum characteristics of the seismic dynamic responses at different locations are significantly different, and a weak area of the peak acceleration may be caused by the joint attenuation effect. Based on the joint time-frequency analysis, it is suggested that adjustments for both the peak acceleration and spectrum be made before taking the ground motion record as the incident wave.

Stress-strain behavior of soil-rock mixture at medium strain rates – Response to seismic dynamic loading

This paper aims to investigate the seismic dynamic responses of soil-rock mixtures (SRM) at medium loading strain rates. A total of 130 SRM specimens with four rock block percentage (RBP) of 20%, 30%, 40% and 50% were produced to conduct the uniaxial compressive strength test, at strain rates of 1×10−5s−1, 5×10−4s−1, 1×10−3s−1, 5×10−3s−1, and 1×10−2s−1. From the experimental results, SRM presents particular rate-dependence characteristics that are different from each soil and rock material, the peak stress and peak strain first increase and then decrease with the increase of strain rate. The inflection points of rate-dependence are different for specimens with different RBP. The rate-dependence characteristic of SRM is strongly influenced by the rock blocks in the SRM specimen. In addition, crack initiation stress level σci/σf and crack damage stress level σcd/σf do not change with the increases of strain rate. What is more, the experimental results also show that the failure pattern of SRM performs as a spitting failure, shear failure, and conical failure at various strain rates. All the test results proved the particular seismic dynamic responses of SRM, and the interactions between the rock blocks and the soil matrix are the primary factor determining the dynamic response.

Dynamic Analysis and Seismic Response of Planar Circular Arches with Variable Cross-Section

The aim of this paper is to investigate the dynamic response of planar circular arches with variable cross-section subjected to seismic ground motions. Arches have a wide range of application (e.g. bridges, roofs) thanks to their capacity to span large areas by resolving vertical actions into compressive stresses and confining tensile stresses. The full understanding of their dynamic response is a challenging technical and computational problem, especially when seismic loading is considered. For example, the assumption of axial inextensibility simplifies the differential equations but overestimates the vibration frequencies, especially those of shallow arches since axial forces are of paramount importance (as opposed to beams). In lieu of the above, our formulation incorporates the effect of axial extension, and the arches are modeled using a new generic curved beam model that includes both axial (tangential) and transverse (normal) to the arch centerline deformations, and is able to account for variable mass and stiffness properties, as well as elastic support or restraint. The resulting dynamic governing equations of the circular arch are formulated in terms of the displacements, and solved using an efficient integral equation method. Three circular arches with variable rectangular cross-section are analyzed in order to investigate their dynamic properties and seismic performance. Using both time history and modal analysis useful conclusions are drawn with regard to the contribution of each mode on the calculation of different response quantities.

Study on Dynamic Characteristic and Seismic Response of Long-Span Suspension Bridge with 1960 MPa Cable Wire

In order to break through the limitation of the width of river, depth of water, channel and etc., it is an optimal choice to construct a long-span suspension bridge. In a suspension bridge, the main cable is the major bearing member; and the use of super high strength cable wire can lighten the dead weight and obtain an economical design. 1960 Mpa cable wire is adopted by an under-construction suspension bridge, namely Ni-Zhou Channel Bridge, for the first time in China. In this paper, taking the Ni-Zhou Channel Bridge as a case-study, comparative analyses on dynamic characteristic and seismic response of long-span suspension bridge with 1960 Mpa cable wire are performed. Firstly, dynamic calculating model for Ni-Zhou Channel Bridge is built and its dynamic characteristics are studied; then by using response spectrum and time history analysis method, seismic response of Ni-Zhou Channel Bridge is investigated on the basis of design response spectrum and artificial seismic ground motions; finally, the energy dissipation performances of a seismic protection devices (viscous damper) are also discussed. The results show that long-span suspension bridge with 1960 Mpa cable wire has a longer natural vibration period; the use of viscous damper can effectively reduce the peak value of bending moment in stiffening girder. This paper can provide references for the project’s construction.

Seismic dynamic response of ground surface above goaf of coal mine

Chinese coal mines are mostly located in the region with seismic intensity of 7 or higher. The vast tridimensional mined-out spaces formed in the strata of mine goaf have been increasing due to large-scale coal mining exploitation. Especially some underground mines are located in the industrial and residential areas. The study analyzed the seismic response at the ground surface transferred from the mine goaf by using FLAC3D numerical models for various conditions. The results show that the peak values of the ground surface wave (PGA) for an earthquake SH wave are affected by existing underground spaces of the goaf. These effects have been analyzed and evaluated at monitoring positions on the ground surface with different depth and filling conditions of the goaf.

Dynamic seismic response of a stable intraplate region to a megathrust earthquake

The 2011 M9.0 Tohoku-Oki megathrust earthquake produced strong ground motions with a peak ground acceleration of 1.52cm/s2 in the Korean Peninsula, inducing large dynamic-stress changes in the crust. Sixty-one triggered earthquakes with magnitudes of 0.5–2.5 including 17 unusual, spatially-clustered events were identified from continuous seismic record sections of dense seismic networks for 18h following the megathrust earthquake. The triggered earthquakes occurred in regions of high seismicity. The earthquake occurrence frequency increased after the megathrust earthquake, keeping the Gutenberg-Richter b value invariant. The seismic occurrence rates decreased with time following a modified Omori law. The focal mechanism solutions of triggered earthquakes are consistent with those observed before the megathrust earthquake. An unusual earthquake swarm displays apparent migration with a speed of 28.6±4.4m/h. The changes in pore fluid pressure induced by strong seismic waves may have caused the triggering of earthquakes. The duration and strength of dynamic triggering may be highly dependent on the magnitude and distance of megathrust earthquake.

Dynamic Shake-Table Testing and Analytical Investigation of Self-Centering Steel Plate Shear Walls

AbstractRecent research has shown that self-centering steel plate shear walls (SC-SPSWs) offer an enhanced seismic performance over conventional steel plate shear walls by providing an additional self-centering capability using steel frames detailed with posttensioned (PT) beam-to-column rocking connections. As with other previously proposed self-centering frames detailed with similar beam-to-column connections, this detailing facilitates the incorporation of replaceable energy dissipation components, as part of the lateral force resisting system (LFRS). In doing so, by design, the gravity frame components of the LFRS are also protected from damage during an earthquake. To investigate the dynamic seismic response of this proposed structural system, one-third scaled SC-SPSW specimens were subjected to ground motions during a series of dynamic shake-table tests. The experimental investigation results presented in this paper are the first shake-table tests conducted on SC-SPSWs. This test program was compose...

PDEM-Based Perspective to Probabilistic Seismic Response Analysis and Design of Earthquake-Resistant Engineering Structures

AbstractA perspective based on the probability density evolution method (PDEM) to the probabilistic seismic response analysis and design of earthquake-resistant engineering structures is provided in this paper. The development of characterization of randomness in seismic ground motions and nonlinear seismic dynamic response analysis of engineering structures are first reviewed and found to be almost independent, which hinders rapid adoption of refined methods for seismic design. The approaches for stochastic dynamics, which is expected to bridge the above gap, in earthquake engineering are revisited, which results in the statement that more physically based methodology is in urgent need for nonlinear stochastic dynamic response analysis of structures. This is the role that the PDEM will play, and thus the theoretical basis and some new advances of PDEM, including the ensemble evolution form of the generalized density evolution equation, ensemble evolution–based dimension reduction of Fokker-Planck-Kolmogo...

Dynamic seismic response of a rubble-mound breakwater with fluid-structure interaction

The purpose of this paper is to understand the dynamic response of rubble-mound breakwater with seawater-breakwater-foundation interaction after a real earthquake shock. This study employs the Arbitrary Lagrangian Eulerian approach and dynamic finite element method, in which the seawater and the foundation of rubble-mound breakwater are considered;then the dynamic response of rubble-mound breakwater during earthquake is simulated. It is found that the seawater-breakwater-foundation interaction does have considerable effect on residual displacements of the rubble-mound breakwater. The difference in horizontal residual displacement due to the effect of seawater-breakwater interaction is greater than that of vertical residual displacement. The vertical component of earthquake has a considerable effect on the hydrodynamic pressure on breakwater face. According to the results presented in this study, it is necessary to consider the effect of interaction for rubble-mound breakwaters seismic safety evaluation. The present research provides some guidance for the seismic design of rubble-mound breakwater. ©2016, Engineering Mechanics Press. All right reserved.

Effect of Different Groundwater Levels on Seismic Dynamic Response and Failure Mode of Sandy Slope.

Heavy seismic damage tends to occur in slopes when groundwater is present. The main objectives of this paper are to determine the dynamic response and failure mode of sandy slope subjected simultaneously to seismic forces and variable groundwater conditions. This paper applies the finite element method, which is a fast and efficient design tool in modern engineering analysis, to evaluate dynamic response of the slope subjected simultaneously to seismic forces and variable groundwater conditions. Shaking table test is conducted to analyze the failure mode and verify the accuracy of the finite element method results. The research results show that dynamic response values of the slope have different variation rules under near and far field earthquakes. And the damage location and pattern of the slope are different in varying groundwater conditions. The destruction starts at the top of the slope when the slope is in no groundwater, which shows that the slope appears obvious whipping effect under the earthquake. The destruction starts at the toe of the slope when the slope is in the high groundwater levels. Meanwhile, the top of the slope shows obvious seismic subsidence phenomenon after earthquake. Furthermore, the existence of the groundwater has a certain effect of damping.

Inelastic Dynamic Seismic Response of 15-Story and 25-Story RC Buildings with and without Shear Walls Designed with the Mexico City Building Code

The inelastic seismic behavior of two reinforced concrete buildings of 15-story and 25-story is compared with and without shear-walls. The resistance-seismic design and vertical loads is made according to the requirements of the Mexico City Building Code, RCDF-2004, satisfying the limit states of service and resistance: compressible seismic area, group B. Inelastic dynamic seismic responses are determined with step-by-step analysis under SCT-EW-85 record with the nominal resistance and over-resistance effects. Results show the importance of the participation of the shear-walls to help to reduction of the magnitude of structural damages during severe seismic future events. The shear walls located in adequate form inside the structure provide an excellent additional lateral stiffness to solve the common flexibility problems in the soft soil zone of the Valley of Mexico and therefore to avoid severe additional torsion problems. In the shear wall constructions we should pay special attention to the foundation design. It was verified that the shear strengths of the structural elements selected were higher than the seismic demands. In the cases of over-strengths considered, it can be concluded that had a minor incursion in the interval of inelastic performance compared with the inelastic performance presented in the cases of nominal strengths.

Ground motion selection for simulation‐based seismic hazard and structural reliability assessment

SummaryThis paper examines four methods by which ground motions can be selected for dynamic seismic response analyses of engineered systems when the underlying seismic hazard is quantified via ground motion simulation rather than empirical ground motion prediction equations. Even with simulation‐based seismic hazard, a ground motion selection process is still required in order to extract a small number of time series from the much larger set developed as part of the hazard calculation. Four specific methods are presented for ground motion selection from simulation‐based seismic hazard analyses, and pros and cons of each are discussed via a simple and reproducible illustrative example. One of the four methods (method 1 ‘direct analysis’) provides a ‘benchmark’ result (i.e., using all simulated ground motions), enabling the consistency of the other three more efficient selection methods to be addressed. Method 2 (‘stratified sampling’) is a relatively simple way to achieve a significant reduction in the number of ground motions required through selecting subsets of ground motions binned based on an intensity measure, IM. Method 3 (‘simple multiple stripes’) has the benefit of being consistent with conventional seismic assessment practice using as‐recorded ground motions, but both methods 2 and 3 are strongly dependent on the efficiency of the conditioning IM to predict the seismic responses of interest. Method 4 (‘generalized conditional intensity measure‐based selection’) is consistent with ‘advanced’ selection methods used for as‐recorded ground motions and selects subsets of ground motions based on multiple IMs, thus overcoming this limitation in methods 2 and 3. Copyright © 2015 John Wiley & Sons, Ltd.

Boundary setting method for the seismic dynamic response analysis of engineering rock mass structures using the discontinuous deformation analysis method

Summary Large deformations and discontinuous problems can be calculated using the discontinuous deformation analysis (DDA) method by solving time steps, and this method is suitable for simulating the seismic dynamic response of engineering rock mass structures. However, the boundary setting must be carefully analyzed. In this paper, four boundary settings for the DDA method are investigated. First, the contributions to the DDA equations for nonreflecting boundaries (including the viscous boundary and the viscoelastic boundary) are deduced based on the Newmark method. Second, a free-field boundary is introduced in the DDA method with boundary grid generation and coupling calculation algorithms to accurately simulate external source wave motion, such as earthquakes. Third, seismic input boundary treatments are intensively examined, and the force input method is introduced based on nonreflecting boundaries. Finally, the static-dynamic unified boundary is implemented to ensure consistent boundary transformation. The boundary setting method in the DDA method is discussed, and the suggested treatments are used to analyze the seismic dynamic response of underground caverns. Copyright © 2015 John Wiley & Sons, Ltd.

Elastic-Plastic Seismic Response Analysis on the Special-Shaped Chimney

Based on one 240-meter-high special-shaped RC chimney, the structure’s dynamic performance and elastic-plastic seismic response analysis has been studied in detail. From the analysis, it demonstrates the weak areas in the chimney. The interlayer displacement angle about corresponding performance points under four kinds of loading mode were also acuired, and the response of four loading patterns were analyzed.

Shaking table tests of an arch-pillars system and design of strengthening by the use of tie-rods

In arches and vaults, tie-rods play a decisive role in counterbalancing horizontal thrusts produced by both permanent and seismic loadings. In this paper, the effectiveness of flexible tie-rods to improve the seismic response of arch-pillars system is assessed by means of shaking table tests and simple analytical models, developed in the framework of displacement-based design. The reduced scale model, made of rigid blocks with dry joints, has been tested without tie-rod and considering different configurations of strengthening. Both experimental and theoretical results have proved the importance, in particular for this kind of flexible masonry structure, of improving displacement capacity rather then strength, because in this latter case other brittle mechanisms could be activated. The paper shows the possibility of describing the dynamic seismic response of rocking masonry structures, characterized by complex mechanisms made of many blocks and hinges, by an equivalent nonlinear SDOF system.

Dynamic Monitoring and Seismic Response of a Historic Masonry Tower

After the Italian earthquakes of May 2012, an extensive research program had been performed to assess the state of preservation of the tallest historic tower in Mantua, Italy. Subsequently, a continuous dynamic monitoring system was installed in the tower, with seismic and structural health monitoring purposes. After a brief description of the investigated tower and its state of preservation, the paper summarizes some results of the long-term dynamic monitoring.

Effects of Curvature Radius on Seismic Response of Curved Box-Girders Bridge

Taking an engineering design case about a three-span uniform section continuous curved box-girders bridge of city viaduct,this paper sets up a finite element calculating model for the curved box-girders bridge by means of finite element analysis program ANSYS and researchs the influence of dynamic characteristic and seismic response on curved box-girders bridge with the different curvature radius under the same span. The analysis results show that in the same span of curved beam , the low-level frequency impact of changes in different curvature radius of the curved beam bridge is larger,the curvature radius is an importance parameter which influence on dynamic characteristic, and have significant influence on tangential stiffness、radial stiffness and seismic response of curved box-girders bridge.