Earthquake Response Analysis Research Articles

2D dynamic and earthquake response analysis of base isolation systems using a convex optimization framework

A formulation is presented for the 2D dynamic analysis and earthquake response simulation of base isolation systems. The approach is force-based and consists of casting the computation in each time increment as a convex optimization problem. Interaction between the two horizontal components of response is considered in an elegant and simple way through yield functions appearing as constraints of the optimization problem. Numerical examples are carried out to illustrate the approach. These comprise bidirectional shearing of a high damping rubber bearing and earthquake simulations of a real-world base isolation system.

青山咸康著「2次元フィルダム地震応答解析における地盤-堤体相互作用の再考」に対する討議

青山咸康著「2次元フィルダム地震応答解析における地盤-堤体相互作用の再考」に対する討議

Evaluation of Seismic Design Force by Earthquake Response Analysis of Water Tanks Installed in RC Buildings

Evaluation of Seismic Design Force by Earthquake Response Analysis of Water Tanks Installed in RC Buildings

Loading tests of a brace-type multi-unit friction damper using coned disc springs and numerical assessment of its seismic response control effects

In this paper, the performance of a multi-unit friction damper with high-tension bolts tightened via coned disc springs was experimentally investigated, and the response control effects achieved by the friction damper were numerically assessed. Elemental tests were performed to obtain the basic characteristics of dampers composed of two friction units. The dampers exhibited a stable rigid-plastic restoring force characteristic without significant degradation of the frictional force even under repetitive loading operations. In full-scale tests, the performance of a brace-type damper composed of eight or 10 friction units and incorporated into a steel frame was investigated. The brace-type damper demonstrated stable performance and showed no remarkable decrease in the sliding force, even under repeated loading. The damper was shown to produce a total frictional force approximately proportional to the number of the friction units. Thus, the total frictional force of the damper can be estimated as the sum of the contributions of the friction units. Moreover, adopting multiple friction units and assembling them permit the damper to achieve a high total frictional force capacity. Earthquake response analysis was conducted using a 30-story high-rise building model incorporating the brace-type dampers to assess their performance against various earthquake motions, including long-period, long-duration motions and pulse-like motions. By installing the high-capacity brace-type dampers into the two spans out of 12 spans for each floor of the main frame, a response reduction effect was obtained in most analytical cases compared to the model without dampers.

An example of three dimensional ground model development for earthquake response analysis by using a simple ground modeling system

An example of three dimensional ground model development for earthquake response analysis by using a simple ground modeling system

Importance of coherence between geophysical and geotechnical data in dynamic response analysis

The demand for a precise evaluation of shear wave velocity Vs, is gaining interest in the field of geotechnical engineering due to its importance as a key parameter required to properly evaluate typical characteristics of soils. Nowadays, Vsmeasurements are performed on the field using different methods, such as SCPT tests and various geophysical methods. However, the effectiveness of these field measurements is not guaranteed and rather depends on how they are analyzed. Furthermore, a proper analysis is critical since the collected data may be used in liquefaction evaluation or earthquake ground response analyses. In these situations, it is recommended to verify the coherence between the obtained geophysical (Vs) and geotechnical (N-SPT, qc-CPT) measurements using alternative methods (e.g., Vs-correlations, H/V method, etc...). In some situations, the correlation between the different measurements makes it easier to unambiguously define seismic wave profiles. In other cases, geophysical and geotechnical tests would provide different resolutions for Vsmeasurements, an issue that complicates the decision of the practitioner. In this paper, we first demonstrate the importance of the shear-wave velocity in liquefaction potential analysis. A case study performed in eastern Canada is also presented where we show the importance of the method used to calculate Vsprofiles (MASW, MMASW).

Stress path dependent small strain stiffness of Shanghai clay

The soil small strain stiffness plays an important role in many geotechnical applications such as machine foundations, deep excavations and earthquake ground response analysis. In this study, the small strain stiffness of saturated intact Shanghai clay specimen is measured in a hollow cylinder apparatus. The lateral earth pressure coefficient at rest is measured first during the one-dimensional consolidation. After consolidation, the very small strain stiffness is obtained by shear wave measurement using bender elements, while the degradation of small strain stiffness with strain is investigated by quasi-static loading with high resolution linear variable displacement transducers (LVDT). The effect of stress path on the small strain stiffness is also investigated. The results show that the small strain stiffness is nonlinear and significantly depends on the stress path.

Effects of compaction on soil undrained shear strength deteriorating during undrained cyclic loading and controlling seismic stability of embankment

Effects of compaction on the undrained shear strength of saturated earth-fill dam materials are presented. Poorly and well compacted saturated soils may exhibit undrained shear strengths, respectively, significantly lower and higher than corresponding drained shear strength and this trend is amplified as the undrained strength deteriorates by preceding undrained cyclic loading. These features are implemented in a new simplified seismic analysis to evaluate residual deformation of earth-fill dams. The analysis consists of: 1) a modified Newmark sliding block analysis; and 2) a pseudo-static non-linear FEM analysis, both formulated in a unified framework based on the cumulative damage concept, total stress earthquake response analysis and a direct total stress modelling of undrained monotonic and cyclic stress-strain behaviours obtained by triaxial tests. The analysis simulates very well the collapse of an earth-fill dam by the 2011 Off the Pacific Coast of Tohoku Earthquake, Japan, and indicates a substantially higher seismic stability under the same conditions of the newly restored dam completed in 2017. Paramount effects of soil compaction on the seismic stability of earth-filled dam are demonstrated.

Horizontal Bi-Axial Shake Table Test of Multi-Supported Piping System with a Damaged Support Structure and Earthquake Response Analysis of the Shake Table Test

Horizontal Bi-Axial Shake Table Test of Multi-Supported Piping System with a Damaged Support Structure and Earthquake Response Analysis of the Shake Table Test

Seismic Performance Evaluation of a Multistory RC Building in Padang City

Since a long time ago, Padang City has been recognized as one in most-earthquake and tsunami prone city in the world. The successive significant earthquakes that have struck western coast of Sumatra Island from 2004 to 2010 seems to warn the city about its prone condition. The last major Padang-Pariaman earthquake on September 30, 2009, for instance, has caused hundreds of death and lousy damage to thousands of houses and buildings in city. Recently, several new multistory reinforced concrete (RC) buildings have been established in this area. Its include such buildings as government office, mosques, hotels, school and university. The city government plans to use these buildings as vertical evacuation facilities if an earthquake followed by a tsunami hit the city in the near-future. As a consequence, of course, these infrastructures should be well designed and constructed to resist the future earthquakes motion. This paper discusses an evaluation of the seismic performance of an existing multistory RC building in Padang city. The building was a ten-story of hotel RC building located near the coastline of Padang city. A series Pushover and Time History Analyses were conducted to examine the seismic performance of the target R/C building. It uses STructural Earthquake Response Analysis (STERA-3D), a computer software based on the nonlinear finite element method. The Pushover analysis was conducted for maximum drift ratio 1/200 in X and Y directions, respectively. The input ground motion in a maximum acceleration of about 400 gals and 600 gals for 60 seconds’ excitation were used for the Time History Analysis. These input ground motions were generated from the recorded ground motion of 2009 Padang-Pariaman earthquake. The result of the analyses suggest that the current target multistory RC building has outstanding seismic performance. The result is based on the level of damage of the structural components, base shear, inter-story drift, lateral displacement, dynamic responses and the seismic capacity spectrum of the analytical model.

Study on the small strain shear modulus of saturated sand-fines mixtures by bender element test

The small strain shear modulus Gmax is an important parameter in geodynamic calculation and earthquake response analysis of site. To have a better fundamental understanding of the deformation behaviour of sand-fines mixtures, a total of 105 bender element tests have been performed. It is found that the Gmax is significantly dependent on fines content FC, initial effective confining pressure σ′3c and void ratio e. Furthermore, FC has an obvious influence on the trend of Gmax – e curve, but the impact decreases as σ′3c increases. According to Hardin’s equation, a modified model and an evaluation method of Gmax of sand-fines mixture are proposed and verified. Tests results and example of application indicate that the modified equation accounting for the influence of FC can predict the Gmax of sand-fines mixture satisfactorily.

Earthquake response analysis of yielding structures coupled with vertically restrained rocking walls

SummaryThis paper investigates the inelastic response of a yielding structure coupled with a vertically restrained rocking wall. The paper first derives the nonlinear equations of motion of a yielding oscillator coupled with a vertically restrained rocking wall, and the dependability of the one‐degree of freedom idealization is validated against the nonlinear time‐history response analysis of a well‐known nine‐story moment‐resisting steel frame that is coupled with a stepping, vertically restrained rocking wall. While, the coupling of weak building frames with rocking walls is an efficient strategy that controls inelastic deformations by enforcing a uniform interstory‐drift distribution, therefore, avoiding mid‐story failures, the paper shows that even for medium‐rise buildings the effect of vertical tendons on the inelastic structural response is marginal, with the exception of increasing the vertical reactions at the pivoting points of the rocking wall. Accordingly, the paper concludes that for medium‐rise to high‐rise buildings, vertical tendons in rocking walls are not beneficial.

Earthquake Response Analysis for Seismic Isolation System of Single Layer Lattice Domes With 300m Span

Earthquake Response Analysis for Seismic Isolation System of Single Layer Lattice Domes With 300m Span

Earthquake Response Analysis of the Historic Reinforced Concrete Temple Otaniha Hakodate Betsuin after Seismic Retrofitting with Friction Dampers

ABSTRACT The main hall of Otaniha Hakodate Betsuin completed in 1915 is a historic reinforced concrete temple located in Hakodate, Japan. This temple was designated as an Important Cultural Property of Japan in 2007. Seismic retrofitting using supplemental vibration control devices, such as friction dampers, may be an effective approach for upgrading the aseismic performance of the temple. In the present study, nonlinear response analysis using two numerical three-dimensional frame models subjected to strong input motions was conducted to predict the aseismic performance of the temple without retrofitting and after retrofitting with friction dampers. The results indicate that the installation of the friction dampers would enhance the aseismic performance of the temple by improving the energy dissipation, stiffness, and seismic capacity of the temple. However, the increase in the seismic capacity of the main story achieved by incorporating the dampers would increase the response acceleration at the roof level.

Earthquake response and isolation effect analysis for separation type three-dimensional isolated structure

This study proposes a design method for separation type three-dimensional isolated structure in which the horizontal and vertical isolation layers are separated for decoupling purpose. In this system, multiple guide rails are used vertically to limit the lateral displacements of upper structure while providing adequate overturning moment resistance. In this paper, a general formulation was proposed firstly to define two critical parameters, i.e., the rotation coefficient and the rotational displacement coefficient, the latter of which correlates the rotation-induced displacement and the total horizontal displacement. Subsequently, a separation type three-dimensional isolated structure model using the proposed method was established to evaluate its isolation effect through shaking table test, and a similar non-isolated structure model was also tested for comparison purpose. An analytical model was established for comparison to the experimental results. Experimental results show that the acceleration responses of the separation type three-dimensional isolated structure model are much less than the non-isolated model in both horizontal and vertical direction, demonstrating a desirable isolation effect for the isolated structure. In the meantime, the vertical guide rails benefits significantly to the overturning moment resistance.

Simplified evaluation of earthquake-induced hydrodynamic pressure on circular tapered cylinders surrounded by water

Dynamic response of offshore structures can be influenced due to the water-structure interaction. The water-structure interaction can be simply represented by added mass in earthquake response analysis. The added mass for a circular cylinder can be obtained by analytical method. However, the added mass for an arbitrary shape of structure is rather difficult to be solved by analytical method. In this study, a substructure method for analysis of the seismic response of an arbitrary shape of structure is presented. The finite element technique incorporating the exact artificial boundary condition presented for simulating the far field of the infinite water is applied to the evaluation of added mass for offshore structures, where the exact added mass matrix is fully populated and symmetrical. The structure is idealized as a three-dimensional finite element model system. Firstly, the presented method is to investigate the seismic response of circular tapered cylinder vibrating in water. Secondly, a lumped added mass matrix is adopted to replace the exact added mass matrix. Thirdly, a simplified formula is presented to evaluate the added mass of the circular tapered cylinder.

Study on the Mechanism of the Peculiar Behaviors of the Aratozawa Dam During the 2008 Earthquake

During the Iwate-Miyagi Nairiku Earthquake (M7.2) of June 14, 2008, seismic motions with a maximum acceleration of 1,024 cm/s2in the stream direction were recorded at the foundation bedrock of Aratozawa Dam, a rockfill dam located approximately 16 km from the epicenter. However, the maximum response acceleration in the same direction near the center of the dam crest was 525 cm/s2, and the acceleration amplification ratio of the dam body was far lower than that normally considered for a rockfill dam. Furthermore, it was measured that the crest settled down 19.8 cm after the earthquake. In this study, the dynamic properties of the embankment materials were identified using reproduction analysis of past earthquakes, and the recorded behaviors of the dam body during the mentioned strong earthquake were simulated. The generating mechanism of the peculiar earthquake behavior was investigated based on the results of the earthquake response analysis. Furthermore, in order to understand the deformation mechanism, sliding stability analysis and cumulative damage analysis were performed. According to the results, the residual deformation of the dam body after the strong earthquake is inferred to be caused by the shaking settlement of the embankment materials.

Required Column Overdesign Factor of 3D Steel Moment Frames with Square Tube Columns

Steel moment frames are designed to ensure sufficient energy absorption capacity by achieving an entire beam-hinging collapse mechanism against severe earthquakes. Therefore, the column overdesign factor is stipulated in seismic design codes in some countries. For example in Japanese seismic design code, the specified column overdesign factor is 1.5 or more for steel moment frames with square tube columns. And this paper describes seismic response by 3D analysis of steel moment frames, and presents seismic demand for the column overdesign factor to keep the damage of square tube columns below the specified limit of plastic deformation. The major parameters are column overdesign factor, horizontal load bearing capacity, shape of frames and input direction of ground motion. In order to investigate 3D behavior of frames and correlation between plastic deformation of columns and column over design factor, apparent column overdesign factor, which is defined as the ratio of full plastic moment of the column (s) to the full plastic moment of the beam (s) projected in the input direction of the ground motion, is introduced. From the earthquake response analysis, it is clarified that the profile of maximum value of cumulative plastic deformation of columns to apparent column overdesign factor, with the similar horizontal load bearing capacity, are nearly identical regardless of number of stories, floor plan, and input direction of ground motion. As a result, the required column overdesign factor to keep the damage of columns below the limit of plastic deformation is proposed under the reliability index of 2.

Earthquake Response Analysis of Sites in State of Haryana using DEEPSOIL Software

Earthquake response analysis has been carried out for various locations in the State of Haryana (India) adopting the equivalent linear approach. For this purpose, geotechnical data have been collected from different government and private organizations. Based on the provisions of National Earthquake Hazards Reduction Program (NEHRP), all the sites have been classified using average N-value (N30) for the soil profile. The shear modulus (Gmax) values of the layers in a soil profile have been estimated using standard correlations. Cyclic Response has been accounted for using the standard shear modulus degradation and damping curves. Time histories from Himalayan Thrust System have been used as an input and soil amplification has been estimated at the surface using DEEPSOIL software. The results of the study have been formulated in terms of soil amplification map, response spectra, PGA along the depth, surface time histories and strain along the depth. These results can be used for dynamic analyses and design of structures, planning of advanced dynamic lab test etc. Moreover, it has been observed that sites in Haryana can significantly amplify ground motions and hence a site-specific design approach must be adopted for important structures.

MODELING FOR LATERAL RESISTANCE CHARACTERISTICS OF RETAINING WALL IN COLLISION OF BASE-ISOLATED BUILDING

When extra-large earthquake which exceeds the input level of designing occurs, a base-isolated building may collide with surrounding retaining wall. To evaluate accurately the acceleration of superstructure and the deformation of base isolator at that time, restoring force characteristics of the retaining wall including the back soil should be clarified. In this study, the collision analyses of base-isolated building using 3D-FEM are carried out, and the restoring force characteristics of retaining wall are investigated. Simple modeling of the collision spring which have the initial rigidity and the maximum strength are proposed as for parameters of height and length of retaining wall, collision speed of building, collision height, and the shear wave velocity of back ground. The obtained results are summarized as follows. 1) By collision analysis and evaluation of restoring force characteristics of a real base-isolated building model, retaining wall thickness, height and length greatly affect retaining wall restoring force characteristics. Initial stiffness and maximum load stress of retaining wall portion increase when the retaining wall thickness, height and length are increased. On the other hand, the weight of building and the ground at the bottom of the foundation board have little influence on the restoring force characteristic of retaining wall. In addition, the collision speed of the building exerts a large influence on the restoring force characteristic, and the initial stiffness increases as the collision speed increases, but when it reaches a certain collision speed or more, it reaches a certain limit and becomes constant. The maximum load increases with the square root of collision speed. Since the collision speed varies with the assumed input seismic motion, it is important to perform the earthquake response analysis on the building in advance and to use the speed at the time of displacement by the clearance between the building and the retaining wall. The initial stiffness and Maximum load increases as shear wave velocity increases. 2) We propose Equation 7 for initial rigidity and Equation 8 for maximum load as a simplified retaining wall collision evaluation formula. By this formula, it is possible to install the collision phenomenon of the retaining wall of the base-isolated building in parallel with the spring of the base isolation device as a collision spring, by changing the shape (thickness, height, length) of the retaining wall and collision condition (Height, impact velocity), and the surrounding ground (shear wave velocity).