Floor Spectra of Inelastic RC Frame Buildings Considering Ground Motion Characteristics

A range of reinforced concrete frame buildings with different levels of inelasticity as well as periods of vibration is analyzed to study the floor response. The derived floor acceleration response spectra are normalized by peak ground acceleration, peak floor acceleration, and ground response spectrum. The normalization with respect to ground response spectrum leads to the lowest coefficients of variation. Based on this observation as well as previous studies, an amplification function is proposed that can be used to develop design floor spectra from the ground motion spectrum, considering the building’s dynamic characteristics and level of inelasticity.     

从光谱角度研究博物馆照明对染色丝绸的影响

光照是引起染色丝绸褪色的主要环境因素之一。为评价博物馆照明对染色丝绸的褪色影响,实验研究了博物馆常用照明LED灯、荧光灯、卤素灯对茜草、苏木、栀子、黄檗、紫草、槐米、靛蓝七种植物染料染色丝绸样品的褪色影响,从灯光的发射光谱结合染色样品的光反射率曲线角度尝试进行了分析。研究结果显示由于卤素灯在低波段的能量较低,对各种染色丝绸样品的褪色影响最小,低于常见的LED灯与荧光灯;3000K色温的灯光对褪色的影响基本上低于4000K色温的灯光。由于染料的不同,其褪色敏感波段不同,造成各种照明对其褪色影响程度有差异。因此为了更好地保护文物,博物馆照明应结合文物的特质,从照明发射光谱角度综合考虑,研发博物馆专用的照明灯具。     

Wild lentil and chickpea harvest in Israel: bearing on the origins of Near Eastern farming

Several small seeded plants were domesticated as grain crops in the Near East and other domestication centers. In this study we investigate the potential of small seeded wild lentils, and chickpea as a food source for hunters-gatherers. The yield potential and the return in terms of grams of seeds per hour of collection time were evaluated in several wild populations in Israel. The yield figures never exceeded 50 g/h, and in most cases were below 20 g/h. These data reaffirm Ladizinsky's claim that wild lentils are unlikely to have been a staple resource for hunter-gatherers prior to plant domestication. The result presented herein may be significant vis-a-vis the role attributed to small seeded (‘inefficient’) plants in the Broad Spectrum hypothesis concerning late Paleolithic, pre-agricultural societies. It may also contribute to a more careful interpretation of plant remains recovered from pre-agricultural sites.     

Considering Soil-Nonlinearity Effect on Seismic Performance Evaluation of Structures based on Pushover Analysis

According to the most of current seismic codes, nonlinear soil behavior is commonly ignored in seismic evaluation procedure of the structures. To contribute on this matter, a pushover analysis method incorporating the probabilistic seismic hazard analysis (PSHA) is proposed to evaluate the effect of nonlinear soil response on seismic performance of a structure. The PSHA outcomes considering soil nonlinearity effect is involved in the analysis procedures by modifying the site-specific response spectrum. Results showed that incorporation of nonlinear soil behavior leads to an increase in displacement demand of structures which should accurately be considered in seismic design/assessment procedure. Results of implemented procedure are confirmed with the estimated displacement demand including soil-structure interaction (SSI).     

An Improved Algorithm for Selecting Ground Motions to Match a Conditional Spectrum

This paper describes an algorithm to efficiently select ground motions from a database while matching a target mean, variance, and correlations of response spectral values at a range of periods. The approach improves an earlier algorithm by Jayaram et al. [2011]. Key steps in the process are to screen a ground motion database for suitable motions, statistically simulate response spectra from a target distribution, find motions whose spectra match each statistically simulated response spectrum, and then perform an optimization to further improve the consistency of the selected motions with the target distribution. These steps are discussed in detail, and the computational expense of the algorithm is evaluated. A brief example selection exercise is performed, to illustrate the type of results that can be obtained. Source code for the algorithm has been provided, along with metadata for several popular databases of recorded and simulated ground motions, which should facilitate a variety of exploratory and research studies.