Horizontal Vertical Coupling Research Articles

Effect of Horizontal-Vertical Coupling on the Seismic Performance of Unanchored Nonstructural Components in a Triple Friction Pendulum Base-Isolated Building

Effect of Horizontal-Vertical Coupling on the Seismic Performance of Unanchored Nonstructural Components in a Triple Friction Pendulum Base-Isolated Building

Shaking table tests on the multi-dimensional seismic response of long-span grid structure with base-isolation

Seismic isolation technology is being applied in large long-span-structured public buildings more and more often worldwide. Aimed to investigate the horizontal and vertical dynamic response of long-span gird structure, the shaking table tests of 1/20 scale long-span grid structures with and without base-isolation considering horizontal two-dimensional (2D) and three-dimensional (3D) seismic excitations were conducted. The test model was designed as ordinary long-span spatial grid structure, but with lead rubber bearings. Data on the acceleration, displacement, strain, and shear force of the base-isolation model and fixed-base model were collected and compared. The dynamic responses of the structure subjected to the horizontal and vertical ground motions with different intensities were studied. The experimental results showed that compared with the fixed-base model, the horizontal period and damping ratio of the base-isolation model can be significantly improved, reducing the horizontal dynamic response of the superstructure, and the horizontal isolation effect was improved with the increase of the seismic excitation intensity. The horizontal acceleration of the roof layer for the base-isolation model was amplified in 3D excitation compared to horizontal input due to horizontal-vertical coupling. Meanwhile, significant vertical acceleration and displacement responses of long-span roof for fixed-base structure were induced by horizontal seismic excitation. Although base isolation could not provide protection against vertical excitation, vertical isolation effect under 3D input could be achieved by effectively suppressing the vertical dynamic response of grid roof induced by the horizontal seismic component.

Slab Vibration and Horizontal–Vertical Coupling in the Seismic Response of Low-rise Irregular Base-isolated and Conventional Buildings

ABSTRACTThis paper evaluates factors that may influence slab vibration and/or induce a horizontal–vertical (H-V) coupled response of buildings with mass irregularities. Responses are investigated through computational simulation of a hypothetical three-story building with base isolation and conventionally configured. Induced mass eccentricities are observed to influence, in an unpredictable way, the vertical slab acceleration and the H-V coupled response, which is identified through modal analysis and floor spectral analysis. The implications of vertical slab vibrations and H-V coupling behavior on the design forces for nonstructural components and systems (NCSs) are evaluated, and modifications are proposed for consideration.

Influence of Vertical Ground Shaking on Horizontal Response of Seismically Isolated Buildings with Friction Bearings

This paper focuses on a horizontal-vertical coupling effect observed in a full-scale shake table experiment of a 5-story moment frame building isolated with triple pendulum bearings. A significant increase or amplification of the horizontal floor accelerations was observed during three-dimensional (3D) shaking compared to XY (horizontal only) shaking with comparable input motions. The coupling phenomenon is explained by analytical and numerical simulation of a single degree-of-freedom (rigid mass) structure and multistory cantilever structure subjected to simplified sinusoidal motions, both isolated with triple pendulum bearings. The results of the simplified numerical study are extended to explain the horizontal-vertical coupling in the full-scale experiment, which are also validated by numerical modeling of the test structure. The vertical component of ground acceleration is shown to introduce a high-frequency component into the base shear that can excite higher modes of the base-isolated structure. The phenomenon is possible in any multistory structure isolated with friction bearings, and should be evaluated on a case-by-case basis.

Dynamical core model intercomparison project: Tracer transport test cases

AbstractThree‐dimensional advection tests are required to assess the ability of transport schemes of dynamical cores to model tracer transport on the sphere accurately. A set of three tracer‐transport test cases for three‐dimensional flow is presented. The tests focus on the physical and numerical issues that are relevant to three‐dimensional tracer transport: positivity preservation, inter‐tracer correlations, horizontal–vertical coupling, order of accuracy and choice of vertical coordinate. The first test is a three‐dimensional deformational flow. The second test is a Hadley‐like global circulation. The final test is a solid‐body rotation test in the presence of rapidly varying orography. A variety of assessment metrics, such as error norms, convergence rates and mixing diagnostics, are used. The tests are designed for easy implementation within existing and developing dynamical cores and have been a cornerstone of the 2012 Dynamical Core Model Intercomparison Project (DCMIP). Example results are shown using the transport schemes in two dynamical cores: the Community Atmosphere Model finite‐volume dynamical core (CAM‐FV) and the cubed‐sphere finite‐volume MCore dynamical core.

Matrix formalism of synchrobetatron coupling

In this paper we present a complete linear synchrobetatron coupling formalism by studying the transfer matrix which describes linear horizontal and longitudinal motions. With the technique established in the linear horizontal-vertical coupling study [D. Sagan and D. Rubin, Phys. Rev. ST Accel. Beams {\bf 2}, 074001 (1999)], we found a transformation to block diagonalize the transfer matrix and decouple the betatron motion and the synchrotron motion. By separating the usual dispersion term from the horizontal coordinate first, we were able to obtain analytic expressions of the transformation under reasonable approximations. We also obtained the perturbations to the betatron tune and the Courant-Snyder functions. The closed orbit changes due to finite energy gains at rf cavities and radiation energy losses were also studied by the 5$\times$5 extended transfer matrix with the fifth column describing kicks in the 4-dimension phase space.

Existence of a twist angle intrinsic to the reference orbit in circular accelerators

In a circular accelerator, a horizontal-vertical coupling can occur as a purely geometrical effect, in the absence of any coupling device (skew-quadrupole magnets, etc.). The coupling between horizontal and vertical coordinates (and momenta) is represented by a rotation [SO(2)]. The rotation angle is called the twist angle. It comes from the geometry of the reference orbit, and is related to the possible nonintegrability of parallel transport on it. We give an analytic expression of the twist and discuss some simple dynamical consequences of the twist on betatron tune.

Betatron phase and coupling correction at the Cornell Electron/Positron Storage Ring

The presence of quadrupole errors in a storage ring will lead to errors in the Twiss parameters and/or errors in the horizontal-vertical coupling. This in turn can lead to degradation of machine performance, such as a decrease in the luminosity. At the Cornell Electron/Positron Storage Ring, the measurement of the betatron phase along with the horizontal-vertical coupling has led to the ability to locate the position of any quadrupole errors and to calculate its strength. This is analogous to using orbit data to locate the source of a kick. Once the source of the error is known, steps can be taken to remove it or to nullify its effect.

Betatron phase and coupling measurements at the Cornell Electron/Positron Storage Ring

Measurement of the betatron phase in the vertical and horizontal planes as well as the transverse horizontal-vertical coupling is a standard procedure now used at the Cornell Electron/Positron Storage Ring. The measurement is made by shaking the beam and observing the phase of oscillation at detectors located around the ring. The measurements allow quadrupolar errors to be corrected.