Evaluation of residual drift demands in regular multi‐storey frames for performance‐based seismic assessment

This paper summarizes results of a comprehensive analytical study aimed at evaluating the amplitude and heightwise distribution of residual drift demands in multi‐storey moment‐resisting frames after earthquake excitation. For that purpose, a family of 12 one‐bay two‐dimensional generic frame models was subjected to an ensemble of 40 ground motions scaled to different intensities. In this investigation, an inelastic ground motion intensity measure was employed to scale each record, which allowed reducing the record‐to‐record variability in the estimation of residual drift demands. The results were statistically processed in order to evaluate the influence of ground motion intensity, number of stories, period of vibration, frame mechanism, system overstrength, and hysteretic behaviour on central tendency of residual drift demands. In addition, a special emphasis was given to evaluate the uncertainty in the estimation of residual drift demands. Results of incremental dynamic analyses indicate that the amplitude and heightwise distribution of residual drift demands strongly depends on the frame mechanism, the heightwise system structural overstrength and the component hysteretic behaviour. An important conclusion for performance‐based assessment is that the evaluation of residual drift demands involves significantly larger levels of uncertainty (i.e. record‐to‐record variability) than that of maximum drift demands, which suggests that this variability and corresponding uncertainty should be explicitly taken into account when estimating residual drift demands during performance‐based seismic assessment of frame buildings. Copyright © 2006 John Wiley & Sons, Ltd.     

Seismic Hazard Assessment in Armenia

An evaluation of seismic hazard assessment in the territory of Armenia is presented in this work. The catastrophic M = 7.0 Spitak earthquake in 1988 revealed the drawbacks of the acting seismic zoning map. Two seismic hazard maps have been compiled in NSSP RA during 1991–1996. The deterministic approach was applied in the first one and the probabilistic in the second one. Both maps were compiled on the basis of the same database. Comparison between the maps shows good correlation. This revised version was published online in June 2006 with corrections to the Cover Date.     

概率天气预报的兴起及其社会经济意义

作者试图从辨证法观点分析概率天气预报之所以兴起的认识论动机和社会经济动机，指出了概率天气预报的产生既是人对天气气候变化同时具有确定性和随机性的认识不断深化的结果，也是社会经济发展到一定阶段，经济决策日益定量经和精细化客观需要，阐述了气象－经济决策这一跨学科领域与概率天气预报之间的相互关系，并有一个简单的气象经济决策模式从理论上和实例计算结果证明了概率天气预报比传统的天气预报更高的经济价值。     

日本数值预报产品降水预报准确性检验

作者对日本部分数值预报产品对上海市市区的降水预报准确性作了初步检验。检验结果表明，它们的降水预报正确率仅为６０％左右，且月际变化较大，无明显规律。使用数值预报产品时必须结合本地区当时的实际情况，根据多种工具结合预报经验综合运用，不能盲目照搬。     

ON THE SENSITIVITY OF PRECIPITATION FORECASTS TO THE MOIST PHYSICS AND THE HORIZONTAL RESOLUTION OF NUMERICAL MODEL

The impacts of the enhanced model's moist physics and horizontal resolution upon the QPFs(quantitative precipitation forecasts)are investigated by applying the HIRLAM(high resolutionlimited area model)to the summer heavy-rain cases in China.The performance of the control run,for which a 0.5°×0.5°grid spacing and a traditional“grid-box supersaturation removal+Kuo typeconvective paramerization”are used as the moist physics,is compared with that of the sensitivityruns with an enhanced model's moist physics(Sundqvist scheme)and an increased horizontalresolution(0.25°×0.25°),respectively.The results show:(1)The enhanced moist physics scheme(Sundqvist scheme),by introducing the cloud watercontent as an additional prognostic variable and taking into account briefly of the microphysicsinvolved in the cloud-rain conversion,does bring improvements in the model's QPFs.Althoughthe deteriorated QPFs also occur occasionally,the improvements are found in the majority of thecases,indicating the great potential for the improvement of QPFs by enhancing the model's moistphysics.(2)By increasing the model's horizontal resolution from 0.5°×0.5°,which is already quitehigh compared with that of the conventional atmospheric soundings,to 0.25°×0.25°without thesimultaneous enhancement in model physics and objective analysis,the improvements in QPFs arevery limited.With higher resolution,although slight amelioration in locating the rainfall centersand in resolving some finer structures of precipitation pattern are made,the number of the mis-predicted fine structures in rainfall field increases with the enhanced model resolution as well.     

The design storm concept in flood control design and planning

The design storm approach, where the subject criterion variable is evaluated by using a synthetic storm pattern composed of identical return frequencies of storm pattern input, is shown to be an effective approximation to a considerably more complex probabilistic model. The single area unit hydrograph technique is shown to be an accurate mathematical model of a highly discretized catchment with linear routing for channel flow approximation, and effective rainfalls in subareas which are linear with respect to effective rainfall output for a selected “loss” function. The use of a simple “loss” function which directly equates to the distribution of rainfall depth-duration statistics (such as a constant fraction of rainfall, or a ?-index model) is shown to allow the pooling of data and thereby provide a higher level of statistical significance (in estimating T-year outputs for a hydrologic criterion variable) than use of an arbitrary “loss” function. The above design storm unit hydrograph approach is shown to provide the T-year estimate of a criterion variable when using rainfall data to estimate runoff.     

岩体结构随机模型模拟方法

本文论述利用勘探平硐资料研究岩体结构面分布规律及进行岩体结构面随机模型模拟方法。文中首先论述了描述结构面空间分布规律的五个几何参数,即产状、形态、规模、密度和张开度及其相应的概率分布型式;其次简单的介绍了 Monte-Carlo 方法在模拟结构面分布中的应用;最后结合三峡工程实例,论述了利用坝基勘探平硐编录图及现场记录估计结构面产状、迹线长度、中点密度分布参数的方法,并且给出了在参数估计基础上进行 Monte-Carlo模拟的部分结果。本文为岩体结构力学分析提供了一个定量的结构模型。     

Probabilistic approach to short- and intermediate-term earthquake forecasting: II test application to southern California

A method is proposed for assessing the modifying effects of precursory observations on long-term probabilities of strong earthquakes (M6). Estimated short-and intermediate-term probabilities so estimated rely on the mean precursory time and its uncertainty as a function of the mainshock magnitude and epicentral position. Short-and intermediate-term modification of long-term probabilities within a 120,000 km² circular area covering most of Southern California are estimated for one or more observations of strain, resistivity, and ground water anomalies centered near Palmdale in the central Transverse Ranges. The principal assumptions employed are log normal distribution of globally reported waiting periods and assumed predictive reliability of precursory phenomena. As expected, the significance of short-and intermediate-term modifications scale with the reliability of precursory observations, and are particularly enhanced within window lengths of a precursory characteristic time.     

A generalized probabilistic approach for slope analysis

Summary A new probabilistic approach is introduced for slope stability analysis, which is general in types of variable distributions and correlations or dependency between variables, and flexible enough to include any adverse impact analysis for blasting vibrations and groundwater conditions.The material strength within a slope area, given in terms of the internal friction angle (ø) and cohesion (c), is randomized in the bivariate joint probability analysis. To be a completely general engineering method, the new probabilistic approach employs the random variable transformation technique: the Hermite model of the Gaussian transformation function, which transforms the experimental histogram of shear strength parameters to the standard Gaussian distribution (=0, ²=1.0).Because a binormal joint probability is analysed on the true probability region projected on the plane of the Gaussian transformed variables, it is an exact solution of slope stability based on the available sample data. No assumption on the shape of the experimental histogram or independency between two random variables is made as in the current probability methods of slope analysis.