Modification of Dynamic Foundation Response Due to Soil-Structure Interaction

This paper presents the results from extensive parametric dynamic analyses of soil-structure systems that focus on the clear modification (increase or decrease) of the acceleration amplitude at the foundation with respect to the free-field, especially for squatty structures. Properties of the systems are selected such as to cover a wide range of meaningful geometries and materials for engineering practice. The results are presented in terms of weighted modification factors of the maximum foundation acceleration amplitude with reference to the corresponding maximum acceleration amplitude at free-field, for squatty and more slender structures. For the large majority of the studied systems, foundation acceleration decreases from the free-field by 10–15% on average. Nevertheless, acceleration demand at the foundation increases compared to the free-field, for 30% of squatty and for 15% of the more slender structures. Modification of the foundation acceleration amplitude is also correlated with the ratio of the predominant period of the input motion to the flexible-base system period. Finally, the findings of this study are compared with sparse available recorded data from the Seismic Hazard Harmonization in Europe database.     

从“■”同“苟”说起

“苟”与“苟”本是两个形、音、义皆不同的字。由于隶定之后,字形相近,而“苟”字又在传世典籍中鲜有用例,故二字混而不别。“”本是“苟”的古文异体,亦被误认为是“苟”的异体,并因此由不同角度讹变出不同的字形。本文力图阐明“苟”、“苟”混而不别及相关异体产生的原因由来。     

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.     

An Analytical Study on the Seismic Vulnerability of Masonry Buildings in India

Two analytical models for unreinforced masonry (URM) buildings are proposed with the aim to simulate their seismic response and to estimate corresponding vulnerability functions. The proposed models are implemented in SAP 2000 nonlinear software to obtain capacity curve parameters for representative Indian URM buildings, based on a field survey and statistical analysis. Vulnerability functions are estimated using the obtained capacity curves. Damage Probability Matrices (DPMs) are obtained using the approximate PGA-intensity correlation relationship as per Indian seismic building code and are compared with the commonly used intensity scales and empirical damage data observed after the 2001 Bhuj earthquake.     

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.     

《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.     

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.     

改性MDI型聚氨酯文物保护材料耐光性能研究

为了提高文物保护材料PU（一种MDI型聚氨酯）的耐光老化性能,采用紫外线吸收剂UV531、UV328和UVP对其进行改性。使用傅立叶变换红外光谱、反射光谱、光老化失重等手段表征改性材料的耐光老化性能。通过对表征结果的比较,得出了UV531改性MDI型聚氨酯比未改性MDI型聚氨酯及其它二种改性材料具有更优异的耐光老化能力,其对彩绘漆器文物样品也能起到更好的保护作用。     

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.