The distribution of algae and insects in hot spring thermal gradients at Waimangu,New Zealand

The distribution of algae and insects was examined in two hot spring outflow channels at Waimangu in the Rotorua thermal district. The upper temperature limit for algal growth was 68°c, with maximum biomass occurring at 59–62°c. Two species of Diptera were present on the algal mat, Ephydrella thermarum Dumbleton at 34–43°c and Chironomus cylindricus Freeman at 39–41°c. The composition and temperature relations of the community are similar to those found in thermal regions in other parts of the world.     

Identification of yield drift deformations and evaluation of the degree of damage through the direct sensing of drift displacements

Inter‐story drift displacement data can provide useful information for story damage assessment. The authors' research group has developed photonic‐based sensors for the direct measurement of inter‐story drift displacements. This paper proposes a scheme for evaluating the degree of damage in a building structure based on drift displacement sensing. The scheme requires only measured inter‐story drift displacements without any additional finite element analysis. A method for estimating yield drift deformation is proposed, and then, the degree of beam end damage is evaluated based on the plastic deformation ratios derived with the yield drift deformation values estimated by the proposed method. The validity and effectiveness of the presented scheme are demonstrated via experimental data from a large‐scale shaking table test of a one‐third‐scale model of an 18‐story steel building structure conducted at E‐Defense. Copyright © 2016 John Wiley & Sons, Ltd.     

Probabilistic collapse resistance and residual drift assessment of buildings with fluidic self‐centering systems

The seismic performance of three‐ and six‐story buildings with fluidic self‐centering system is probabilistically assessed. The fluidic self‐centering systems consist of devices that are based on the technology of fluid viscous dampers but built in a way that pressurization of the devices results in preload that is explored to reduce or eliminate residual drift. The design of these buildings followed a procedure that parallels the design for structures with damping systems in ASCE 7 but modified to include the preload effect. Reference conventional buildings were also designed per ASCE 7 for comparison. These buildings were then analyzed to examine and compare their seismic collapse resistance and residual drift, where the residual drift limits of 0.2, 0.5, 1.0 and 2.0% of story height were selected as important thresholds. The study further calculated the mean annual frequency of collapse and corresponding exceedance probability over 50 years, and the mean annual frequency of exceeding the threshold residual story drift limits and the corresponding exceedance probability over 50 years. Variations in the design procedures by considering increased displacement capacity or damping or preload of the devices, different types of damping, increased ultimate strength of the self‐centering device–brace systems and increased frame strength were considered. It was found that increasing either the ultimate force capacity of the self‐centering device–brace system or the frame strength results in important improvements in the collapse resistance and in minimizing residual drift, whereas the variation of other design parameters has minor effects. Copyright © 2016 John Wiley & Sons, Ltd.     

Shaking table comparative test and associated study of a stepped wall-frame structure

A new structural system called a stepped wall-frame structure is proposed in this study to solve the bottom yielding problem of RC frames, which widely occurred during previous earthquakes such as the Wenchuan and Yushu earthquakes in China. A 1/5 scale ordinary RC frame model and a stepped wall-frame model were subjected to shake table motions together to study the seismic behavior of the new structural system. This paper presents the dynamic characteristics, the seismic responses and the failure and collapse mechanism of the two models under low, moderate and high intensity shaking. The test results and further analysis demonstrate that the seismic performance of stepped wall-frame structures is superior to ordinary RC frames in terms of the well-controlled deformation pattern and more uniformly distributed damage. The stepped wall can effectively suppress the bottom yielding mechanism, and is simple, economical and practical for engineering practice.     

Loss estimation for non‐ductile reinforced concrete building in Victoria,British Columbia,Canada: effects of mega‐thrust Mw9‐class subduction earthquakes and aftershocks

This paper presents, within the performance‐based earthquake engineering framework, a comprehensive probabilistic seismic loss estimation method that accounts for main sources of uncertainty related to hazard, vulnerability, and loss. The loss assessment rigorously integrates multiple engineering demand parameters (maximum and residual inter‐story drift ratio and peak floor acceleration) with consideration of mainshock–aftershock sequences. A 4‐story non‐ductile reinforced concrete building located in Victoria, British Colombia, Canada, is considered as a case study. For 100 mainshock and mainshock–aftershock earthquake records, incremental dynamic analysis is performed, and the three engineering demand parameters are fitted with a probability distribution and corresponding dependence computed. Finally, with consideration of different demolition limit states, loss assessment is performed. From the results, it can be shown that when seismic vulnerability models are integrated with seismic hazard, the aftershock effects are relatively minor in terms of overall seismic loss (1–4% increase). Moreover, demolition limit state parameters, uncertainties of collapse fragility, and non‐collapse seismic demand prediction models have showed significant contribution to the loss assessment. The seismic loss curves for the reference case and for cases with the varied parameters can differ by as large as about 150%. Copyright © 2015 John Wiley & Sons, Ltd.     

Seismic behavior of steel buildings with out‐of‐plumb

A structure that has a permanent offset from a true vertical line is commonly referred to as being ‘out‐of‐plumb’. Out‐of‐plumb may result from construction tolerances or post‐earthquake permanent deformations in steel buildings. This paper quantifies the displacements of buildings with out‐of‐plumb in subsequent seismic events by means of inelastic dynamic time history analysis. Structures considered have different structural heights, force design reduction factors (R), and target inter‐story drifts. It is shown that buildings with greater out of plumb and force design reduction factor have larger normalized peak inter‐story drift ratio and ratio of residual‐to‐peak drift. Also, the ratio of residual‐to‐peak drift was not strongly dependent on structural height or design drift. A design procedure and example provided, based on the results obtained, show how peak and residual inter‐story drift ratio can be estimated. Copyright © 2015 John Wiley & Sons, Ltd.     

Generalized force vectors for multi‐mode pushover analysis of torsionally coupled systems

A generalized multi‐mode pushover analysis procedure was developed for estimating the maximum inelastic seismic response of symmetrical plan structures under earthquake ground excitations. Pushover analyses are conducted with story‐specific generalized force vectors in this procedure, with contributions from all effective modes. Generalized pushover analysis procedure is extended to three‐dimensional torsionally coupled systems in the presented study. Generalized force distributions are expressed as the combination of modal forces to simulate the instantaneous force distribution acting on the system when the interstory drift at a story reaches its maximum value during seismic response. Modal contributions to the generalized force vectors are calculated by a modal scaling rule, which is based on the complete quadratic combination. Generalized forces are applied to the mass centers of each story incrementally for producing nonlinear static response. Maximum response quantities are obtained when the individual frames attain their own target interstory drift values in each story. The developed procedure is tested on an eight‐story frame under 15 ground motions, and assessed by comparing the results obtained from nonlinear time history analysis. The method is successful in predicting the torsionally coupled inelastic response of frames responding to large interstory drift demands. Copyright © 2014 John Wiley & Sons, Ltd.     

非偶极子磁场西向漂移的频散特征

根据第8代国际参考地磁场的资料,本文采用Briggs方法对1900～2000年期间m=1～10次谐波的磁位的全球平均西向漂移速度进行了计算和分析,得出了与Hide的理论预测完全不同的频散特征,即地磁场西向漂移呈现出负频散特征.本文还就Briggs方法得到的结果与采用Malin纬度剖面法的结果进行了比较和讨论,结果表明,正是由于非偶极子磁场的某些谐波分量及其漂移速度的全球分布存在着纬度依赖性,导致了两种方法计算出的个别谐波的漂移速度存在着较大的差异.     

塔克拉玛干沙漠风况特征研究

通过17个站1996-2000年风资料的统计和计算,对塔克拉玛干沙漠风况特征进行研究,结果发现：(1)塔克拉玛干沙漠作用风系以东北风和西北风为主,在纵向和横向上主风向都呈现出明显变化规律;(2)输沙势计算结果表明,除若羌地区外整个塔克拉玛干沙漠处于低风能环境;(3)大多数区域RDP／DP值都大于0．5,呈现单峰或锐双峰特征。     

青海湖东克土沙区风沙运动规律及防治对策

起沙风况、输沙势和输沙量是反映风沙活动强度的3个重要指标。以青海湖东克土流沙区的风况资料为依据,结合实地风沙观测数据,分析了区域的风沙活动特征。结果表明:(1)3\,4\,5月(主要风沙活动期)起沙风出现的比率分别是0.40、0.47\,0.53,起沙风速集中于6~16 m·s^-1,占统计时段的91%,高能起沙风速(达到16 m·s^-1及其以上的风速)集中在16:00-20:00。(2)研究区域总体上属于高能风况环境,3月和5月输沙势的风向变率都小于0.3,表明风向变幅大,风能不集中,对于沙区周围公路和草原的危害从不同的方向推进。(3)观测期间各方位输沙量总和为503.67 kg,NE、ENE、E和ESE 4个方位的输沙量最大,占总输沙量的43.56%。