Earthquake Response Analysis Research Articles

Analysis of Elastic-Plastic Lateral-Torsional Coupled Earthquake Response of Multilayer Bidirectional Stiffness Eccentric Frame Structure

Analysis of Elastic-Plastic Lateral-Torsional Coupled Earthquake Response of Multilayer Bidirectional Stiffness Eccentric Frame Structure

Surrogate models for seismic response analysis of flexible rocking structures

AbstractSeismic design tools are based on surrogate models of the designed structure and the responses of those surrogates to earthquake ground motions. To design symmetric flexible rocking structures, a surrogate model that includes rocking and flexure is needed. In this paper, we derive the equation of motion of a flexible multi‐degree‐of‐freedom (MDOF) structure rocking on its base in modal coordinates. Then, we introduce a set of two‐degree‐of‐freedom (2DOF) surrogate models that accounts only for the first elastic vibration mode of the multimass structure and its rotation about the base pivot points. We investigate the surrogates' ability to represent the dynamics of an elastic MDOF structure that uplifts and rocks and the interaction between rocking and flexure. Therein, we detail the simplifications for the equations of motion of the 2DOF surrogate models and the adopted rocking impact model, and develop and check the sliding initiation condition. We show that the simplified 2DOF surrogate model responses compare well to experimental results. Then we assess the 2DOF surrogate model accuracy in representing the earthquake response of the MDOF model using Cloud Analysis and the coefficient of determination approach. We find that simplified 2DOF surrogate of the MDOF model is quite accurate () in estimating its maximum relative top displacement and acceptably accurate () in estimating its maximum base rotation based on a thousand randomly generated flexible rocking structure earthquake response analyses. Lastly, we discuss using the simplified 2DOF surrogate model of symmetric flexible rocking structures in preliminary seismic design, and give examples featuring a continuous elastic hollow semi‐conical chimney and an inelastic flexible MDOF structure, both with a base that may uplift.

Earthquake Response Analysis of Pond Ash Deposit with Geocell Reinforcement

Earthquake Response Analysis of Pond Ash Deposit with Geocell Reinforcement

Reproduction of Liquefaction Characteristics of Pleistocene Sand Using Artificial Materials and Modeling in Earthquake Response Analysis

Reproduction of Liquefaction Characteristics of Pleistocene Sand Using Artificial Materials and Modeling in Earthquake Response Analysis

Earthquake Response and Damage Analysis of Tianning Temple Pagoda

Earthquake Response and Damage Analysis of Tianning Temple Pagoda

Simplified earthquake response analysis of rectangular liquid storage tanks considering fluid-structure interactions

A simplified model of a rectangular liquid storage tank is proposed to estimate the earthquake responses of the system while considering the effects of fluid-structure interactions. The complicated three-dimensional structural behavior of a rectangular tank is represented by the simple combination of the fundamental modes of a rectangular-ring-shaped frame structure and a cantilever beam. The governing equation for the system is derived from Lagrange’s equation. The earthquake responses of deflection, hydrodynamic pressure and its resultant force and moment, base shear and overturning moment due to the structural deformation are obtained from the solution of the governing equation. The effective masses of the system and their heights are presented with the effective added masses and their heights from the hydrodynamic effects. The total earthquake responses are obtained with the convective earthquake responses taken into consideration. The proposed simplified model is applied to example rectangular liquid storage tanks with various aspect ratios, and the accuracy of the model is demonstrated. The proposed simplified model can be employed for the seismic design of a rectangular liquid storage tank, and reliable estimations for earthquake responses of the considered fluid-structure interaction system are obtained without sophisticated and/or complicated dynamic analysis.

Structural concept and analysis of the 16- and 14-story base isolated apartment buildings constructed on one stylobate in the multifunctional complex “Arami”

Seismic isolation strategies were developed in Armenia due to the efforts of the author of this paper. Many medium and high-rise base isolated buildings were constructed in different regions of the country. Among them there are multi-story residential and business center complexes with parking floors and with floors envisaged for offices, shopping centers, fitness clubs, etc. Some complexes are briefly mentioned in the paper. However, the main information in this paper is given to describe the 16- and 14-story base isolated apartment buildings constructed on one stylobate in the multifunctional complex “Arami” in the city of Yerevan. The complex has unique structural concept, including the suggested by the author approach on installation by clusters of seismic isolation laminated rubber-steel bearings (SILRSBs) in seismic isolation interfaces of these buildings. Some details of the suggested concepts and construction peculiarities are described. Also, some results of the earthquake response analyses are given. The building was analyzed using several time histories and also according to the requirements of the Armenian Seismic Code.

Soil-Structure Interaction of Retaining Walls under Earthquake Loads

The study is devoted to both static and earthquake response analysis of retaining structures acted upon by lateral earth pressure. Two main approaches were implemented in the analysis, namely, the Mononobe-Okabe analytical method and the numerical Finite element procedure as provided in the ready software ABAQUS with explicit dynamic method. A basic case study considered in the present work is the bridge approach retaining walls as a part of AL-Jadiriya bridge intersection to obtain the effects of the backfill and the ground water on the retaining wall response including displacement of the retaining structure in addition to the behavior of the fill material. Parametric studies were carried out to evaluate the effects of several factors such as vertical and horizontal components of the earthquake, maximum peak acceleration, angle of friction, damping ratio, height of the wall and groundwater level within the medium of fill. Three heights of retaining walls were considered for those above mentioned factors, these are (2.9m, 4.7m and6.7m). A comparison is made between the responses obtained on the basis of finite element analysis with those obtained using the Mononobe-Okabe method. It is found that the lateral wall responses obtained using the FE were larger than those calculated by the Mononobe-Okabe method for all heights of the retaining wall, it was also found that pore pressure of the ground water depends on the water flow through the backfill during the earthquake. The distribution of the dynamic earth pressure on the wall is nonlinear and depends on the earthquake ground acceleration in addition to the wall height and soil properties. Based on the numerical analysis and the results obtained from the parametric studies carried out, two expressions are proposed to evaluate the maximum lateral wall response in terms of wall height, soil properties and earthquake base excitation acceleration, and hence the dynamic earth pressure acting on the retaining structure.

Nonlinear earthquake responses of unanchored cylindrical liquid storage tanks on flexible soil

A sophisticated and versatile finite-element model of the nonlinear behavior of unanchored cylindrical liquid storage tanks on flexible soil is proposed and applied for nonlinear earthquake response analysis of the system. The tank is modeled using shell finite elements with material and geometric nonlinearities. The hydrodynamic pressure is represented by acoustic finite elements. The effects of the base uplift are considered by nonlinear springs with negligible and large stiffness coefficients in tension and compression, respectively. The flexible soil is modeled using mechanical springs and dashpots. The effects of base uplift and soil flexibility are examined for typical unanchored tall and broad tanks on flexible soil with various shear-wave velocities. It is observed that the structural responses and hydrodynamic pressure, including the convective pressure of an unanchored tall tank on rigid/flexible soil, are significantly influenced by the base uplift. Although the base uplift in a broad tank is not as large as that in a tall tank, the structural responses and hydrodynamic pressure of an unanchored broad tank can be different from those of an anchored system. However, the convective pressure of the broad tank is not significantly affected by the base uplift. The earthquake responses of the system are principally influenced by the horizontal component of the earthquake ground motion rather than the vertical component.

Effect of Numerous Small Deformations Due to Moderate Earthquakes on Seismic Response of Wooden Houses

In order to confirm the effect of multiple moderate earthquakes on the response deformation of wooden houses at the time of a major earthquake, an earthquake response analysis, considering performance deterioration due to repeated small deformations, was conducted. As a result, it was found that the effect of multiple moderate earthquakes on the mean response deformation during a major earthquake was small. On the other hand, in some cases, the response deformation was up to 1.2 times larger than that of the sound case. In the case of a house where the response deformation was near the criteria of continuous use and/or collapse, the influence of the response magnification was large. This shows the importance of giving higher seismic performance compared to the standard. The response deformation during repeated medium earthquakes may increase for houses with considerably low seismic performance. However, for the houses that meet current standards, little to no increase in response deformation was seen.

A site-specific earthquake ground response analysis using a fault-based approach and nonlinear modeling: The Case Pente site (Sulmona, Italy)

In this paper we present the ground response analyses (GRA) of a site where an industrial facility is planned. Due to its location on an active normal fault system known as a relevant seismic gap, the Mt. Morrone Fault system (MMF), and at the edge of a basin filled with slow velocity continental deposits, a inter-disciplinary and non-standard approach has been applied to assess the seismic input of the dynamic numerical analyses. It includes geological, seismological, geotechnical and engineering contributions. Two fault scenarios, MMF1 and MMF2, were considered and scenario-based (SSHA) and probabilistic (time-dependent, TD, and time-independent, TI) seismic hazard (PSHA) analyses were implemented. Comparison among the spectra corresponding to the 90th percentile of the SSHA statistical distribution and the PSHA average ones shows that the SSHA MMF2 has values similar to the PSHA TD model. The SSHA 90th percentile distribution was selected as target spectra to retrieve the seismic input for GRA. Nonlinear numerical simulations of seismic wave propagation were implemented to derive surface ground motion parameters. GRA acceleration response spectra and their PGA are notably higher, and thus on the side of safety, than those obtained following the Italian code approach for seismic resistant buildings. These results confirm that a scenario-based methodology can better capture the shaking effect in near-field conditions, avoiding possibly unconservative underestimations of the seismic actions and in view of a more robust performance-based approach used by engineers for either new design and/or assessment/retrofit purposes of the built environment.

Structural system design and earthquake response analysis of prefabricated pile-plate bridge

ABSTRACT With the advancement of building technology, the pile-plate structure, which originated in railway engineering, has been adopted into highway engineering. This study presents a new pile-plate structure connecting node. The addition of energy-dissipating components at the nodes and the use of non-shrinkage concrete at the joints demonstrate its novelty. The node’s ability to enter the plastic stage is enhanced, resulting in increased seismic performance. In this study, the seismic performance and energy consumption capacity of the pile plate joint were studied by numerical model, and the results showed that the stagnation curve of the pipe pile under low cycle reciprocating load was full and had good energy consumption capacity. Under the action of random seismic vibration, the displacement of the pile plate structure in one direction is up to 0.023 m, which meets the requirements of the specification. The innovative pile-plate joints are used in a nonlinear dynamic time-history analysis of the constructed bridge structure.

Cross-story installation of viscous dampers in timber frame houses for earthquake damage reduction

Timber frame structures are commonly used in housing construction that use squared-off timber beams, columns, and walls as lateral load-bearing members. A small-size viscous damper can be applied to timber frame houses to reduce damage caused by major earthquakes. Dampers are normally installed inter-story (between adjacent floors) to absorb vibration energy and reduce seismic response. Another method is the cross-story installation wherein a damper is installed between the rooftop and base of the structure across intermediate floors. This study investigated the effectiveness of cross-story installation of a viscous damper by conducting eigenvalue analyses of 2DOF models and earthquake response analyses of a two-story timber frame house subjected to the 2016 Kumamoto earthquake and other major earthquakes. We compared the damping factors and response reduction effects of the cross-story installation with those of conventional inter-story installations. The results showed that the cross-story installation of dampers was more effective than the inter-story installation in terms of reducing story drift. Furthermore, the cross-story installation reduced the number of dampers required for preventing severe damage by half. Finally, the cross-story installation allowed the viscous damper in the first story to absorb vibration energy nearly twice as much as that of the inter-story installation. Therefore, while the cross-story damper is typically installed on an outer frame fixed to the house, our results conclude that it can be applied to an existing house as a seismic retrofitting measure.

Ground response analysis and liquefaction for Kalyani region, Kolkata.

The main focus of this research is the ground response analysis and liquefaction potential analysis of AIIMS Kolkata based on SPT-N values at six different locations. The analyses are performed for the earthquake magnitude Mw = 7.0 and peak ground acceleration of 0.170g. For this, Equivalent-linear Earthquake Response Analysis (EERA), Nonlinear Earthquake Response Analysis (NERA), and PLAXIS-2D software are utilized. In ground response analysis, various parameters such as shear stress, peak ground acceleration, relative displacement, and amplification ratio are evaluated. In liquefaction potential analysis, the factor of safety against liquefaction is calculated from different methods, such as the simplified method, EERA, and NERA, and their results have been compared. Further liquefaction potential index is also evaluated for the same earthquake magnitude and PGA using the factor of safety value evaluated from liquefaction potential analysis and ground response analysis for all the borehole locations. It is observed from the results that the equivalent linear analysis gives conservative results when compared with those obtained from the nonlinear analysis. Moreover, the simplified method too fails to predict the liquefaction susceptibility of certain regions that are found to be prone to liquefaction from the EERA and NERA analyses.

Matrix equations models for nonlinear dynamic analysis of two-dimensional and three-dimensional RC structures with lateral load resisting cantilever elements

In control engineering and structural dynamics, mathematical models such as the state-space representation, equation of motion, and the phase plane are matrix equations describing the system equilibrium. This paper develops novel matrix equations models for linear/nonlinear dynamic analysis of reinforced concrete (RC) buildings with cantilever elements lateral load resisting systems (e.g., RC shear wall, RC core). The models offer a new approach for introducing two-dimensional and three-dimensional cantilever structures to control the theory’s state-space representation and structural dynamics’ equation of motion. The development primarily addresses the stiffness and mass matrices. The proposed displacement-related stiffness matrix of cantilever elements satisfies the necessary conditions of symmetricity and elemental boundary conditions. The nonlinear matrix structural analysis employs a smooth hysteretic model for deteriorating inelastic structures, referring to the relation between the bending moment and the bending curvature through the bending stiffness. The parameters controlling the cyclic behavior regard a composite RC cross section subject to gravitational load and bending simultaneously. The paper includes four examples that exemplify the practical utilization of the matrix equations models in analyzing two-dimensional and three-dimensional structures of linearly elastic and inelastic properties. The four examples demonstrated the idealized applicability of the matrix equations models for modal analysis, pushover analysis, and inelastic earthquake response analysis.

Earthquake response analysis of nuclear facilities subjected to incoherent seismic waves based on the random-vibration-theory methodology

In this study, based on the random-vibration-theory (RVT) methodology, an earthquake response analysis of a nuclear facility with a rigid foundation on rock/soil sites is considered when incoherent seismic waves are incident on the system. Using the coherency function of seismic waves, the power spectral density (PSD) matrix for six-degree-of-freedom motions of the rigid foundation is calculated. The stochastic earthquake responses of the soil–structure interaction system are obtained, and the PSD function for the pseudo-acceleration of equipment on one floor of the structure is derived. Peak factors of random vibrations are employed to estimate the spectral acceleration or in-structure response spectrum (ISRS) of the equipment. The accuracy of the proposed RVT methodology is verified for nuclear power plant structures on hard rock, soft rock, and layered soil acted upon by coherent and incoherent seismic waves. Because the ISRS outcomes are found to decline at high frequencies, reduction factors due to incoherency are obtained from the proposed RVT methodology. These factors can be applied to earthquake responses to coherent ground motions to consider the effects of incoherent seismic waves.

Experimental Investigation and Earthquake Response Analysis of an Oblique 3D Isolator with Rotational Mechanism

ABSTRACT This paper presents a nonlinear model of a novel three-dimensional oblique rotating friction seismic isolator (3D ORFSI). A quasistatic test of the device was conducted, and the results showed that devices processed a plump hysteretic loop in the vertical isolation direction, which agreed with the theoretical prediction. The effects of different parameters were evaluated using a mathematical model. The proposed mathematical model was then applied to assess the seismic response of an 8-story concrete-frame building with horizontal isolators and the 3D ORFSI.

MatNERApor—A Matlab Package for Numerical Modeling of Nonlinear Response of Porous Saturated Soil Deposits to P- and SH-Waves Propagation

The paper is devoted to the problem of numerical modeling of earthquake response of porous saturated soil deposits to seismic waves propagation. Site-specific earthquake response analysis is a necessary and important component of seismic hazard assessment. Accounting for the complex structure of porous saturated soils, i.e., the content in them, in addition to the solid matrix, pore water, gas mixture and ice, is especially important for the water areas in the zones of continuous or sparse permafrost, as well as the massive release of bubble gas from bottom sediments. The purpose of this study is to introduce an algorithm and its Matlab implementation for numerical modeling of the nonlinear response of porous saturated soil deposits to vertical P- and SH-waves propagation. The presented MatNERApor package consists of a set of Matlab scripts and functions. The package was tested and verified using the records of vertical seismic arrays of the Kik-net network. In addition, the records of local earthquakes obtained by ocean bottom seismographs in the Laptev Sea in 2019–2020 were used to demonstrate the effect of the water layer above the seabed sites on the reduction of vertical motions spectra. The results of the calculations showed good agreement with the data obtained from real seismic records, which justifies the correctness of the theoretical basis of the presented algorithm and its software implementation.

Statically equivalent seismic loads based on two-mode-based approach for single layer reticulated shells

The present study discusses a method to express statically equivalent seismic loads based on the two dominants modes with emphasis on single-layer reticulated shells encompassing spherical, cylindrical, and free-form shells. The shells investigated are shallow roofs of three-way member arrangement. For the earthquake response analysis, a set of twelve artificial earthquake motions are introduced compatibly with the design response spectrum specified in the building code of Japan. First, to analyze the response behavior and to find the relationship between the shell geometries and their vibrational properties, a vibration database is set up based on the response spectrum method using the results obtained from eigenvalue analysis. Second, an analysis of pseudo-seismic energy and mass ratios of free vibration modes is performed to discuss what have important roles in estimating the equivalent seismic loads. Third, from a viewpoint of the two-mode-based aaproach, the importance of the pseudo-seismic energy is discussed, then followed by a proposal of the equivalent seismic loads for the reticulated shell roofs. Finally, the validity of the proposed formation is confirmed under a certain restraint to its application.

Effect of Mean Grain Size on the Small‐Strain Dynamic Properties of Calcareous Sand

Calcareous sand was selected as the prior material for island reclamation in many coastal regions. The mechanical properties of the granular materials are greatly affected by their grain size distribution conditions. The shear modulus and damping ratio are two important parameters for earthquake ground response analysis and liquefaction evaluation. A series of resonant column tests had been performed on calcareous sands with varying median grain diameter and uniform coefficient. The dependence of the shear modulus and damping ratio of the calcareous sand on grain size has been confirmed in this examination. The test results reveal that the shear modulus decreases with a rise in shear strain for calcareous sand samples at a given confining pressure and relative density. The maximum shear modulus tends to increase with confining pressure and relative density. On the maximum shear modulus and void ratio plane, the trend lines of the measured results shift toward up and right position with a rise in grain diameter. The measured results indicate that the influence of uniform coefficient on the maximum shear modulus is neglectable. A revised empirical equation based on the Hardin model had been proposed considering the influence of grain diameter to estimate the maximum shear modulus of calcareous sand. The predicted values show satisfactory agreement with the measured results. The results manifest that the effect of grading condition on small‐strain dynamic properties of calcareous sands cannot be neglected for the evaluation of seismic safety for reclamation engineering sites.