Rocking Blocks Stability under Critical Pulses from Near-Fault Earthquakes Using a Novel Energy Based Approach

Following the seminal work of Housner, a novel energy based critical pulse theoretical model is derived to assess the seismic stability of rocking rigid blocks under single pulses from near-fault earthquakes. It is shown that overturning is conditional on the availability of sufficient kinetic energy in the exciting pulse and on the inception of rocking. The theoretical model is shown to be in good agreement with discrete element method numerical simulations for similar blocks of sizes 0.5, 1, and 20 m. Similitude rules are established to scale between block sizes and pulse types and tested successfully. The results agree with available experimental data. The proposed stability chart approach provides a practical and simple alternative to the presentation and study of the stability and overturning of blocks published by others in the frequency spectrum domain. For any given rigid block or inverted pendulum structure the model or normalized stability charts provide a method to determine the characteristic period and peak acceleration required for overturning and by extension to identify the critical content of the dominant pulse of a given earthquake signal. Alternatively, the approach could be used in archaeoseismology to identify the characteristics of the dominant pulse content of past earthquakes based on their impacts on various historical and heritage structures.

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Influence of Elastomeric Bearings in Tension on the Seismic Performance of Base-Isolated r.c. Buildings

Applied Sciences ◽

10.3390/app11010082 ◽

2020 ◽

Vol 11 (1) ◽

pp. 82

Author(s):

Fabio Mazza ◽

Mirko Mazza

Keyword(s):

Base Isolation ◽

Nonlinear Models ◽

Vertical Component ◽

Computer Code ◽

Nonlinear Phenomena ◽

Isolation System ◽

Elastomeric Bearings ◽

Near Fault ◽

Base Isolation System ◽

Near Fault Earthquakes

Elastomeric bearings are commonly used in base-isolation systems to protect the structures from earthquake damages. Their design is usually developed by using nonlinear models where only the effects of shear and compressive loads are considered, but uncertainties still remain about consequences of the tensile loads produced by severe earthquakes like the near-fault ones. The present work aims to highlight the relapses of tension on the response of bearings and superstructure. To this end, three-, seven- and ten-storey r.c. framed buildings are designed in line with the current Italian seismic code, with a base-isolation system constituted of High-Damping-Rubber Bearings (HDRBs) designed for three values of the ratio between the vertical and horizontal stiffnesses. Experimental and analytical results available in literature are used to propose a unified nonlinear model of the HDRBs, including cavitation and post-cavitation of the elastomer. Nonlinear incremental dynamic analyses of the test structures are carried out using a homemade computer code, where other models of HDRBs considering only some nonlinear phenomena are implemented. Near-fault earthquakes with comparable horizontal and vertical components, prevailing horizontal component and prevailing vertical component are considered as seismic input. Numerical results highlight that a precautionary estimation of response parameters of the HDRBs is attained referring to the proposed model, while its effects on the nonlinear response of the superstructure are less conservative.

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Seismic Response of RC Frames with a Soft First Story Retrofitted with Hysteretic Dampers under Near-Fault Earthquakes

Applied Sciences ◽

10.3390/app11031290 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1290

Author(s):

Santiago Mota-Páez ◽

David Escolano-Margarit ◽

Amadeo Benavent-Climent

Keyword(s):

Cost Effective ◽

Far Field ◽

Soft Story ◽

Near Fault ◽

Rc Frames ◽

Story Drift ◽

Number Of Cycles ◽

Rc Frame Structures ◽

Near Fault Earthquakes ◽

Hysteretic Dampers

Reinforced concrete (RC) frame structures with open first stories and masonry infill walls at the upper stories are very common in seismic areas. Under strong earthquakes, most of the energy dissipation demand imposed by the earthquake concentrates in the first story, and this eventually leads the building to collapse. A very efficient and cost-effective solution for the seismic upgrading of this type of structure consists of installing hysteretic dampers in the first story. This paper investigates the response of RC soft-story frames retrofitted with hysteretic dampers subjected to near-fault ground motions in terms of maximum displacements and lateral seismic forces and compares them with those obtained by far-field earthquakes. It is found that for similar levels of total seismic input energy, the maximum displacements in the first story caused by near-fault earthquakes are about 1.3 times larger than those under far-field earthquakes, while the maximum inter-story drift in the upper stories and the distribution and values of the lateral forces are scarcely affected. It is concluded that the maximum displacements can be easily predicted from the energy balance of the structure by using appropriate values for the parameter that reflects the influence of the impulsivity of the ground motion: the so-called equivalent number of cycles.

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Performance limits of base-isolated liquid storage tanks with/without supplemental dampers under near-fault earthquakes

Structures ◽

10.1016/j.istruc.2021.04.023 ◽

2021 ◽

Vol 33 ◽

pp. 355-367

Author(s):

Elif Güler ◽

Cenk Alhan

Keyword(s):

Storage Tanks ◽

Performance Limits ◽

Near Fault ◽

Liquid Storage ◽

Supplemental Dampers ◽

Near Fault Earthquakes

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Stability of a Rigid Body With an Oscillating Particle: An Application of MACSYMA

Journal of Applied Mechanics ◽

10.1115/1.3169122 ◽

1985 ◽

Vol 52 (3) ◽

pp. 686-692 ◽

Cited By ~ 4

Author(s):

L. A. Month ◽

R. H. Rand

Keyword(s):

Angular Velocity ◽

Rigid Body ◽

Classical Problem ◽

Moment Of Inertia ◽

Model Parameters ◽

Stability Chart ◽

The Stability ◽

Transition Curves ◽

Minimum Moment ◽

Small Angular Velocity

This problem is a generalization of the classical problem of the stability of a spinning rigid body. We obtain the stability chart by using: (i) the computer algebra system MACSYMA in conjunction with a perturbation method, and (ii) numerical integration based on Floquet theory. We show that the form of the stability chart is different for each of the three cases in which the spin axis is the minimum, maximum, or middle principal moment of inertia axis. In particular, a rotation with arbitrarily small angular velocity about the maximum moment of inertia axis can be made unstable by appropriately choosing the model parameters. In contrast, a rotation about the minimum moment of inertia axis is always stable for a sufficiently small angular velocity. The MACSYMA program, which we used to obtain the transition curves, is included in the Appendix.

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OPTIMAL VELOCITY MODEL WITH RELATIVE VELOCITY

International Journal of Modern Physics C ◽

10.1142/s0129183106009084 ◽

2006 ◽

Vol 17 (01) ◽

pp. 65-73 ◽

Cited By ~ 5

Author(s):

SHIRO SAWADA

Keyword(s):

Nonlinear Analysis ◽

Relative Velocity ◽

Velocity Model ◽

Fundamental Diagram ◽

Optimal Velocity ◽

Traffic Jam ◽

Optimal Velocity Model ◽

Linear And Nonlinear ◽

The Stability ◽

Good Agreement

The optimal velocity model which depends not only on the headway but also on the relative velocity is analyzed in detail. We investigate the effect of considering the relative velocity based on the linear and nonlinear analysis of the model. The linear stability analysis shows that the improvement in the stability of the traffic flow is obtained by taking into account the relative velocity. From the nonlinear analysis, the relative velocity dependence of the propagating kink solution for traffic jam is obtained. The relation between the headway and the velocity and the fundamental diagram are examined by numerical simulation. We find that the results by the linear and nonlinear analysis of the model are in good agreement with the numerical results.

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Global Stability Analysis of the Wake behind a Circular Cylinder Based on the POD-Chiba Method

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.137.72 ◽

2011 ◽

Vol 137 ◽

pp. 72-76

Author(s):

Wei Zhang ◽

Xian Wen ◽

Yan Qun Jiang

Keyword(s):

Stability Analysis ◽

Circular Cylinder ◽

Global Stability ◽

Dimensional Model ◽

Global Stability Analysis ◽

The Stability ◽

Low Dimensional ◽

Proper Orthogonal ◽

Calculated Amount ◽

Good Agreement

A proper orthogonal decomposition (POD) method is applied to study the global stability analysis for flow past a stationary circular cylinder. The flow database at Re=100 is obtained by CFD software, i.e. FLUENT, with which POD bases are constructed by a snapshot method. Based on the POD bases, a low-dimensional model is established for solving the two-dimensional incompressible NS equations. The stability of the flow solution is evaluated by a POD-Chiba method in the way of the eigensystem analysis for the velocity disturbance. The linear stability analysis shows that the first Hopf bifurcation takes place at Re=46.9, which is in good agreement with available results by other high-order accurate stability analysis methods. However, the calculated amount of POD is little, which shows the availability and advantage of the POD method.

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Seismic performance of steel mega braced frames equipped with shape-memory alloy braces under near-fault earthquakes

The Structural Design of Tall and Special Buildings ◽

10.1002/tal.1225 ◽

2015 ◽

Vol 25 (1) ◽

pp. 3-21 ◽

Cited By ~ 12

Author(s):

Davoud Vafaei ◽

Reyhaneh Eskandari

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Seismic Performance ◽

Braced Frames ◽

Near Fault ◽

Near Fault Earthquakes

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Experimental and Theoretical Investigation of the Supersonic Boundary Layer Stability on the Swept Wing

Siberian Journal of Physics ◽

10.54362/1818-7919-2008-3-3-34-38 ◽

2008 ◽

Vol 3 (3) ◽

pp. 34-38

Author(s):

Sergey A. Gaponov ◽

Yuri G. Yermolaev ◽

Aleksandr D. Kosinov ◽

Nikolay V. Semionov ◽

Boris V. Smorodsky

Keyword(s):

Boundary Layer ◽

Three Dimensional ◽

Leading Edge ◽

Supersonic Boundary Layer ◽

Mean Flow ◽

Swept Wing ◽

Wing Model ◽

Dimensional Boundary ◽

The Stability ◽

Good Agreement

Theoretical and an experimental research results of the disturbances development in a swept wing boundary layer are presented at Mach number М = 2. In experiments development of natural and small amplitude controllable disturbances downstream was studied. Experiments were carried out on a swept wing model with a lenticular profile at a zero attack angle. The swept angle of a leading edge was 40°. Wave parameters of moving disturbances were determined. In frames of the linear theory and an approach of the local self-similar mean flow the stability of a compressible three-dimensional boundary layer is studied. Good agreement of the theory with experimental results for transversal scales of unstable vertices of the secondary flow was obtained. However the calculated amplification rates differ from measured values considerably. This disagreement is explained by the nonlinear processes observed in experiment

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The structure of the Cincinnati arch as determined by short period Rayleigh waves

Bulletin of the Seismological Society of America ◽

10.1785/bssa0590010399 ◽

1969 ◽

Vol 59 (1) ◽

pp. 399-407

Author(s):

Robert B. Herrmann

Keyword(s):

Experimental Data ◽

Theoretical Model ◽

Layer Thickness ◽

Rayleigh Waves ◽

Layer Model ◽

Depth Data ◽

Short Period ◽

Best Fitting ◽

Good Agreement

Abstract The propagation of Rayleigh waves with periods of 0.4 to 2.0 seconds across the Cincinnati arch is investigated. The region of investigation includes southern Indiana and Ohio and northern Kentucky. The experimental data for all paths are fitted by a three-layer model of varying layer thickness but of fixed velocity in each layer. The resulting inferred structural picture is in good agreement with the known basement trends of the region. The velocities of the best fitting theoretical model agree well with velocity-depth data from a well in southern Indiana.

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