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Single-degree-of-freedom (SDOF) elastic models are commonly used for gaining an understanding of the response of structures to earthquake ground motions. The standard SDOF model used does not account for the effect of gravity or the combined effect of horizontal and vertical excitations on horizontal response. The purpose of this paper is to review previous work on this topic and to investigate a series of SDOF models that do incorporate these effects and to compare their response to the response of the standard model using 186 strong-motion records of near-field earthquake ground motions. It is found that for most realistic SDOF models and most earthquake ground motions the effect of vertical excitation on horizontal response is small.

The vibration of pedestrian overbridges due to train-induced wind loads (TIWLs) during the passage of a high-speed train threatens the overbridge safety and causes pedestrian discomfort. To incorporate the structural dynamic magnification effect on overbridges under TIWLs in the design process, a framework to calculate the structural dynamic response, equivalent static TIWLs and response spectra of overbridges is established. A new simplified TIWL model with a “three-segment” wind pressure time history described by harmonic functions is proposed. This model facilitates the acquisition of analytical solutions for the structural dynamic response, streamlining the analysis process. The dynamic response and equivalent static TIWLs based on dynamic magnification factors (DMFs) of overbridges are obtained from the analytical method. The DMFs are primarily affected by the structural natural frequency and the characteristic frequency of TIWLs. Furthermore, based on the analytical solution of the overbridge dynamic response, parametric analysis is performed, and the response spectra representing the dynamic displacement and acceleration of overbridges are developed. The response spectra can be used to quickly calculate the displacement, internal force, and acceleration of the overbridges during engineering applications, which is more convenient but slightly less accurate than the analytical method.

The effects of spatial variability of soil properties on the behaviour of a cohesive and a cohesionless soil profile subjected to seismic excitation are analysed. The input data for the random fields are derived from existing, extensive soil investigations, and Monte Carlo simulation technique, combining digital generation of non-Gaussian stochastic vector fields with dynamic, equivalent linear and nonlinear finite element analyses, is used for this purpose. It is found that the variability of shear wave velocity has small effect on the ground surface response spectrum. The motion intensity and the variation of soil properties in the deterministic description of the profile considerably affect the standard deviation of the surface spectral acceleration, which is successively compared to the uncertainty introduced in attenuation relationships, used for the construction of hazard-consistent design spectra.

Peak ground velocity (PGV) has received much less attention in the technical literature than more widely-used parameters such as peak ground acceleration (PGA) and response spectral ordinates. However, there are many examples of the use of PGV in engineering seismology and earthquake engineering, including as a parameter from which to estimate macroseismic intensity and structural damage. PGV is also employed in some methods for the assessment of liquefaction potential and, because of its relationship to ground strains, in the seismic design and assessment of buried pipelines. One of the most important uses of PGV has been in the construction of elastic response spectra. There are relatively few predictive equations for PGV, compared to those for PGA and spectral ordinates, but 25 such equations are reviewed and summarised. The issue of scaling PGV from response spectral ordinates is explored and it is shown that the common practice of scaling PGV from spectral accelerations at 1.0 second should not be continued because the ratio of the two quantities is highly variable. A more stable relationship exists between PGV and the spectral acceleration at 0.5 second response period; however, it is clearly preferable to estimate peak velocities directly and PGV equations should be derived together with equations for spectral ordinates in the same way as PGA.

In the current Korean code, the site classification and the corresponding site coefficients were determined similar to the UBC 1997, which were revised based on the results from the investigation of the 1989 Loma Prieta earthquakes in the western United States. Since the site effects are directly dependent on the local site conditions, the use of site coefficients derived from earthquake records which occurred in different site conditions may mislead the earthquake ground motion. Therefore, it is important to compare the local site conditions in Korea to those in the western United States and assess their effects on site coefficients, for the reliable estimation of earthquake ground motions in Korea. In this paper, site response analyses were performed based on equivalent linear technique using the shear wave velocity profiles of 162 sites collected around the Korean peninsula. The site characteristics, particularly the shear wave velocities and the depth to the bedrock, are compared to those in western United States. The results showed that the site-response coefficients based on the mean shear velocity of the top 30 m (V_S30) suggested in the current code underestimates the motion in short-period ranges and overestimates the motion in mid-period ranges. Also the current Korean code based on UBC is required to be modified considering site characteristics in Korea for the reliable estimation of site amplification. From the results of numerical estimations, new regression curves were derived between site coefficients (F_a and F_v) and the fundamental site periods, and site coefficients were grouped based on site period. The standard deviations of the proposed method were reasonable compared to site classification based on V_S30. Finally, new site classification system was tentatively recommended based on site periods for regions of shallow bedrock depth in Korea.

We compare four methods, all based on Bayesian regressions, to predict response spectra at instrumented sites, located at the hill and lakebed zones in Mexico City, that have recorded several recent earthquakes. The regressions are built as functions of magnitude and closest distance to the rupture area of the earthquake, using more than 20 subduction earthquakes (thrust-faulting mechanism) recorded since 1964. The four methods are: (1) a regression on observed response spectra; (2) a regression on observed Fourier amplitude spectra and use of random vibration theory to estimate the response spectra, (3) a regression on observed response spectra at the reference hill-zone station multiplied by response spectral ratios; and (4) a regression on Fourier amplitude spectra at the reference hill zone, multiplied by Fourier spectral ratios and use of the random vibration theory to estimate response spectra.

This paper examines the seismic response of clay pile-raft system with flexible and stiff piles using centrifuge and numerical studies. Centrifuge studies showed that interaction between pile-raft and clay will cause a significant softening in the clay adjacent to the pile-raft which produced a lengthening of resonance period in near-field soil compared to the far-field soil. The difference of response among the raft and the soil at both near- and far-field indicates that ground motion at both near- and far-field cannot be representative of raft motion. There is also significant difference between flexible and stiff pile response. It has been shown in a previous study that, for stiff pile, the soft clay acts as an inertial loading medium rather than a supporting medium. For this reasons, the bending moment diagram extends deep into the soft soil stratum. However, for flexible pile, the supporting effect of the surrounding clay is much more significant than in stiff pile. As a result, the bending moment envelope for flexible pile under earthquake shaking is very similar to the head-loaded test results, with an active length of pile below which no significant bending moment occurs.

In seismic design, excitations are usually considered separately in two perpendicular directions of structures. In fact, the two components of ground motions occur simultaneously. This paper clarifies the effects of bi-directional excitations on structures and proposes the response spectra called “bi-directional pseudo-acceleration response spectra”. A simplified analytical model of a two-degree-of-freedom system was employed. The effect of directivity of ground motions was taken into account by applying strong motion records in all directions. The analytical results were presented in the form of the acceleration ratio response spectrum defined as the bi-directional pseudo-acceleration response spectrum normalized by a pseudo-acceleration response spectrum.

North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0–480km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended.

The new generation of X-ray photon counting pixel detectors like the Medipix2 and the Medipix3 opens a new field of applications in medical X-ray imaging. These detectors work with one or more energy windows, which makes energy information available in addition to the intensity. A detailled understanding of the detector response of such detectors is important. Results will be presented for Si and CdTe as sensor material. With this knowledge two methods called spectrum reconstruction and material reconstruction can be applied to energy resolved images in absorption radiography and computed tomography. Another new application is the measurement of the phase information in computed tomography in addition to the absorption information. The potential of phase contrast imaging will be discussed.