Correlations Between Frequency Content Indicators of Strong Ground Motions and PGV

The frequency content of ground motions seems to be one of the most important parameters to explain the structural damage experienced during worldwide strong earthquakes. The frequency content of ground motions can be characterized by various stochastic and/or deterministic indicators: the frequency bandwidth indicator ? (Cartwright & Longuet-Higgins) related to the power spectral density function and, respectively, the control (corner) period T_c of the structural response spectra or the mean period T_M . Peak ground velocity (PGV) and the ratio PGA/PGV can be used as either damage potential parameters or frequency content indicators. A comparative analysis of stochastic and deterministic frequency content indicators and of PGV is applied to a set of 30 strong ground motion records having peak ground acceleration (PGA) from 0.2–0.8 g and recorded on 4 continents during the last 70 years.     

Dynamic Interaction between Rigid Foundations on Multi-layered Stratum

This article concerns the cross-interaction problem among multi-foundations on a linearly viscoelastic medium at very small shear strains. In the analysis, the foundations are discretized into a number of sub square-elements. The dynamic response within each sub-element is described by the Green’s function, which is obtained by the Fourier-Bessel transform and the precise integration method. Incorporating the displacement boundary condition and the force equilibrium of the foundations, it obtains the dynamic impedance and compliance functions of the foundations. Extensive results for two rigid circular foundations placed at different separations are presented. Parametric studies are carried out on the dynamic interaction among adjacent foundations. Illustrative results for several closely spaced foundations are also illustrated.     

The Influence of Soil Moisture,Temperature and Oxygen on the Oxic Decay of Organic Archaeological Deposits

The sensitivity of organic‐rich archaeological layers at Bryggen in Bergen, Norway, to changes in soil temperatures, water contents and oxygen concentrations is investigated. This is done by linking measurements of oxic decay at varying temperatures and water contents with on‐site monitoring data using a one‐pool decomposition model. The results show that the model can be used to elucidate the current in situ decay and to evaluate where and when the decay takes place. Future investigations need to include long‐term incubation experiments and decay studies at zero or very low oxygen contents in order to improve the robustness of predictions.     

《三国志》注译匡误一则

本研讨的是东汉末年东郡太守臧洪给当时豪陈琳一封复信中的几句话。献帝兴平二年(公元195年)十二月至次年建安元年夏,臧洪被大军阀袁绍围困于郡治东武阳。绍令洪邑人陈琳写信劝洪投降,洪不从。复信说明与绍友好初衷是共尊王室,今日对立是绍不尊王室,其中有些重要的话被今人误注误译。追根溯源,多少与史家陈寿、范晔的误解有关。甚至《资治通鉴》等大部头作也沿袭了这些误解。故从复信主旨着眼,依据史实和词义匡正这些错误。     

Impact of Modification on Ground Motion Characteristics and Geotechnical Seismic Analyses for a California Site

The impact of different modification techniques on ground motion characteristics and results of seismic geotechnical analyses is investigated for a site in California. Twenty-eight motions were selected and scaled and also modified using both time domain (TD) and frequency domain (FD) techniques. PGV and PGD of the TD-modified motions are found to be larger than their FD-modified counterparts, but slightly less than the scaled ground motion characteristics. Cyclic stress ratios and amplification factors are similar for all sets of motions. Newmark-type slope displacements caused by the scaled and modified ground motions are similar (within 25%) for a variety of sliding masses.     

中国居民消费增长波动多尺度变化及趋势研究

采用经验模态分解(EMD)方法对1953-2009年中国居民消费增长率波动进行分解,得到其IMF分量及趋势分量RES,运用方差贡献率及相关性检验其周期变化,并利用Mann-Kendall非参数统计检验方法对增长趋势进行研究。结果表明:中国居民消费增长波动存在3年、8年和12.4年的准周期,以准8年周期为主,准3年周期次之;56年来居民消费呈波动增长趋势,1978年是其突变点,当年对外开放政策的提出极大促进了居民消费增长,1983年居民消费增长率超过临界直线,此后呈显著上升趋势。经济因素、居民收入水平和消费结构是影响中国居民消费增长波动的主要因素。     

Effect of Cyclic Loading Frequency on the Behavior of External RC Beam-Column Connections

Reduced-scale external RC beam-column specimens with three typical deficiencies as beam weak in flexure (BWF), beam weak in shear (BWS) and column weak in shear (CWS) were tested under cyclic excitations of different frequencies, varying from 0.025–2.0 Hz. Parameters like load carrying capacity, stiffness degradation, energy dissipation, principal tensile stress were monitored for exploring the effect of rate of loading on different types of deficient beam-column connections in a holistic manner. Test results showed that the rate effect is significant in beam-column connection with BWF, while the same is not so significant in BWS and CWS specimens.     

Source Effects on the Spectral Characteristics of Strong Ground Motions Recorded in Bucharest Area During Vrancea Earthquakes of 1986 and 1990

The August 30, 1986 (M_W ?=?7.1) and May 30, 1990 (M_W ?=?6.9) Vrancea intermediate-depth earthquakes, despite their almost similar magnitudes, have produced very different spectral contents as shown by the strong ground motions recorded in Bucharest and its surroundings. The differences can be attributed to different epicentral distances and to different values of the stress drop. The characteristics of the seismic ground motions recorded in Bucharest area in the 1986 and 1990 seismic events are discussed in the context of (a) the source characteristics of the two earthquakes and (b) the local soil conditions in Bucharest. Furthermore, an attempt is made to determine the soil factors S defined in EN 1998-1 EN 1998-1. 2004. Design of Structures for Earthquake Resistance – Part 1: General Rules, Seismic Actions and Rules for Buildings, CEN.  [Google Scholar] for the Bucharest area, based on the strong ground motion dataset recorded during the two seismic events.     

Seismic Microzonation and Damage Assessment of Bam City,Southeastern Iran

This article aims to study the dynamic characteristics of soil in Bam, southeastern Iran. Fundamental frequency and amplification factor of soil sediment were estimated by microtremor measurement. This procedure was performed at 49 sites in the city. Two 120-second data were recorded at each site. Segmental cross spectra were applied to calculate spectrum, Nakamura's method (H/V) was used for analyzing data and fundamental frequency and amplification factor values were derived. Iso-frequency and iso-amplification maps of the city were prepared. Results show that soil type in Bam city is mainly stiff, although amplification factor is relatively large. There is a short period zone in northwest to southeast direction. Sediment depth was estimated using a correlation between fundamental frequency and sediment thickness. Results obtained from microtremors were compared to the geotechnical boreholes and it was shown that microtremors can be used for a rough estimation of sediment thickness. Damage distribution map of Bam due to the Bam earthquake on December 26, 2003 was prepared by both field and aerial investigation. Quality of buildings in Bam was evaluated, as a result a crude zoning map on the building quality was prepared. Finally, it was concluded that several factors have contributed to damage intensity variation; earthquake characteristics, local site effect, and buildings' quality. All mentioned parameters affected the damage variation.     

A Microscale Approach for the Seismic Response of MDOF Structures Including Soil-Foundation-Structure Interaction

In this article, a three-dimensional microscale computational framework utilizing the discrete element method is presented to analyze the seismic response of soil-foundation- MDOF structure systems. The proposed approach is used to explore the response of MDOF structures on a square embedded footing founded on a dry granular deposit. Computational simulations were conducted to investigate the response of the system to several base excitations. The impact of replacing a MDOF structure with its equivalent single degree of freedom (ESDOF) structure while accounting for soil-foundation-structure interaction (SFSI) is investigated. Detrimental or beneficial effect of SFSI on the response is also examined.