Rotational Components of Earthquake Motion

1975 ◽  
Vol 2 (4) ◽  
pp. 430-436 ◽  
Author(s):  
N. D. Nathan ◽  
J. R. MacKenzie
Keyword(s):  
Ground Motion ◽  
Earthquake Motion ◽  
Rotational Components ◽  
Earthquake Record ◽  
Code Provisions ◽  
Torsional Ground Motion

Following the ideas of Newmark, a complete record of torsional ground motion is generated from the two translational components of an earthquake record. The approximate spectra developed by Newmark are generally confirmed. The assumptions and the limits of validity are discussed. Code provisions for this phenomenon are commented upon.

scholarly journals Seismic rocking effects on a mine tower under induced and natural earthquakes

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Piotr Adam Bońkowski ◽  
Juliusz Kuś ◽  
Zbigniew Zembaty
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Ground Surface ◽  
Tall Buildings ◽  
Earthquake Ground Motion ◽  
Seismic Action ◽  
Seismic Effects ◽  
Copper Ore ◽  
Rotational Components ◽  
Natural Earthquakes

AbstractRecent research in engineering seismology demonstrated that in addition to three translational seismic excitations along x, y and z axes, one should also consider rotational components about these axes when calculating design seismic loads for structures. The objective of this paper is to present the results of a seismic response numerical analysis of a mine tower (also called in the literature a headframe or a pit frame). These structures are used in deep mining on the ground surface to hoist output (e.g. copper ore or coal). The mine towers belong to the tall, slender structures, for which rocking excitations may be important. In the numerical example, a typical steel headframe 64 m high is analysed under two records of simultaneous rocking and horizontal seismic action of an induced mine shock and a natural earthquake. As a result, a complicated interaction of rocking seismic effects with horizontal excitations is observed. The contribution of the rocking component may sometimes reduce the overall seismic response, but in most cases, it substantially increases the seismic response of the analysed headframe. It is concluded that in the analysed case of the 64 m mining tower, the seismic response, including the rocking ground motion effects, may increase up to 31% (for natural earthquake ground motion) or even up to 135% (for mining-induced, rockburst seismic effects). This means that not only in the case of the design of very tall buildings or industrial chimneys but also for specific yet very common structures like mine towers, including the rotational seismic effects may play an important role.

scholarly journals Geophysical and geotechnical factors in urban planing: Bursa (Nilüfer, Osmangazi, and Yildirim) cases

2020 ◽  
Author(s):  
Ferhat Özçep ◽  
Guldane Boyraz ◽  
Okan Tezel ◽  
Hakan Alp ◽  
Nuray Alpaslan ◽  
...  
Keyword(s):  
Ground Motion ◽  
Hazard Analysis ◽  
Earthquake Hazard ◽  
Cyclic Stress ◽  
Soil Liquefaction ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Earthquake Motion ◽  
Potential Index ◽  
Earthquake Hazard Analysis

Abstract. The study area covers the Central of Bursa, Osmangazi, Yildirim, Gürsü, Kestel and Nilüfer District boundaries in Bursa. The seismic process deals with the occurrence of an earthquake event and the process of wave propagation from the source to the site. Local amplification caused by surficial soft soils is a significant factor in destructive earthquake motion. In the first phase of this study, it is investigated the ground motion level and soil amplifications for Bursa city. For his aim, probabilistic and deterministic earthquake hazard analysis (including acceleration estimations) will be carried out for the region. Local amplification caused by surficial soft soils is a significant factor in destructive earthquake motion. In the first phase of this study, it is investigated the ground motion level and soil acharacterization for the region. For his aim, probabilistic earthquake hazard analysis (including acceleration estimations) was carried out for the region. Then, soil shear wave velocities were estimated from data obtained by MASW measurements. Soil liquefaction is a natural event in which the strength and stiffness of a soil are reduced by earthquake vibrations or other dynamic loadings. As it is known, liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. One of liquefaction evaluation methods is based on the cyclic stress approach. In this method, a safety factor is defined as CRR/CSR. CRR is a cyclic resistance ratio that represents soil liquefaction susceptibility, and CSR is the cyclic stress ratio that represents the earthquake effect. In the second phase of this study, possible soil potential index (PL) and ground induced settlements were estimated by using Isihara ve Yoshimine (1990) approach. All results on liquefaction potential index (Pl), liquefaction induced settlements and soil shear wave velocities in Bursa (Turkey) City were compared with each other. Finally, a seismic microzonation map was prepared by the integration of geophysical and geotechnical data for urban planning purposes.

Some methods for determining acceleration and tilt by use of pendulums and accelerometers

1973 ◽  
Vol 63 (1) ◽  
pp. 1-7
Author(s):  
Hugh Bradner ◽  
Michael Reichle
Keyword(s):  
Ground Motion ◽  
Fourth Order ◽  
Horizontal Displacement ◽  
Natural Period ◽  
Rotational Components ◽  
Fourth Order Equations ◽  
Special Case

abstract We consider the use of a system of horizontal and vertical pendulums to determine linear and rotational components of ground motion. Accelerometers can be viewed as a special case of pendulums. Fourth-order equations are always required for determining horizontal displacement unless the natural period of at least one sensor lies far below the passband of interest. Applications to guidance and to seismology are mentioned briefly.

Acceleration amplification due to rotational components of near-fault earthquakes in triple concave friction pendulum base-isolated structures

2018 ◽  
Vol 45 (4) ◽  
pp. 314-327
Author(s):  
Hamed Tajammolian ◽  
Faramarz Khoshnoudian
Keyword(s):  
Dynamic Analysis ◽  
Ground Motion ◽  
Nonlinear Dynamic Analysis ◽  
Maximum Acceleration ◽  
Nonstructural Components ◽  
Geometrical Properties ◽  
Near Fault ◽  
Rotational Components ◽  
Seismic Force ◽  
Friction Pendulum

Recent studies show that rotational components of earthquakes can amplify the floor acceleration in a base-isolated structure. As a result, the seismic force of nonstructural components could be significantly increased. In this paper, a simple rectangular deck with various geometrical properties mounted on triple concave friction pendulum (TCFP) bearings is examined. At first a set of three translational components from 25 near-fault ground motion records are considered. Then, three rotational components, i.e., torsional and two rocking motions are computed for each earthquake. The results of nonlinear dynamic analysis in a rectangular structure with an aspect ratio in plan equal to 3, demonstrate that the acceleration approximately intensifies 3.4 times in presence of all six ground motion components compared to three translational ones. Finally, a new formula is proposed to determine the maximum acceleration of base-isolated structure without performing the dynamic analysis due to rotational components of ground motions.

Effects of Site Classification on Platform Value of Response Spectrum

2011 ◽  
Vol 378-379 ◽  
pp. 306-309
Author(s):  
Ping Li ◽  
Jing Shan Bo ◽  
Xiao Yun Guo ◽  
You Wei Sun ◽  
Yu Dong Zhang
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
Wave Motion ◽  
Response Spectrum ◽  
Equivalent Linearization ◽  
Earthquake Response ◽  
Response Analysis ◽  
Site Classification ◽  
Earthquake Motion ◽  
Design Response Spectrum

Regarding the design response spectrum in the code for seismic design of buildings as target spectra，the 28 acceleration histories are formed artificially．They are used as the inputs ground motion in earthquake response analysis．Four site classifications profiles were selected or constructed from practical site profiles．With the use of 1-D equivalent linearization wave motion method that is wildly used at present in site seismic response analysis, the platform values of surface response spectrum for different profiles under different ground motion inputs were calculated．Different platform values of the response spectrum and relational expression which is seven input earthquake motion intensity and site classifications have been given by statistical analysis.

Design for seismic torsional forces

1984 ◽  
Vol 11 (2) ◽  
pp. 150-163 ◽  
Author(s):  
J. L. Humar
Keyword(s):  
Ground Motion ◽  
Analytical Study ◽  
Critical Evaluation ◽  
Building Code ◽  
Rotational Ground Motion ◽  
Building Model ◽  
Design Basis ◽  
Building Models ◽  
Adequate Design ◽  
Code Provisions

An analytical study of the responses of a single storey and a multistorey building model to a combined translational and rotational ground motion is presented. The models, which are assumed to be elastic, are eccentric about one plan direction but are symmetric about the perpendicular direction. The ground excitations are represented by idealized spectra.A critical evaluation is made of the torsion provisions of the National Building Code of Canada. It is shown that the code provisions, while not necessarily nonconservative, are somewhat difficult to apply for multistorey buildings. An alternative provision for design eccentricity is proposed. The forces obtained by the use of the proposed method are compared with the analytical results of single storey and multistorey building models and are shown to provide an adequate design basis.

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