Seismic performance of wood‐frame houses in south‐western British Columbia     

Katsuichiro Goda  Gail M. Atkinson 《地震工程与结构动力学》2011,40(8):903-924

The seismic performance of conventional wood‐frame structures in south‐western British Columbia is analytically investigated through incremental dynamic analysis by utilizing available UBC‐SAWS models, which were calibrated based on experimental test results. To define an adequate target response spectrum that is consistent with information from national seismic hazard maps, record selection/scaling based on the conditional mean spectrum (CMS) is implemented. Furthermore, to reflect complex seismic hazard contributions from different earthquake sources (i.e. crustal events, interface events, and inslab events), we construct CMS for three earthquake types, and use them to select and scale an adequate set of ground motion records for the seismic performance evaluation. We focus on the impacts of adopting different record selection criteria and of using different shear‐wall types (Houses 1–4; in terms of seismic resistance, House 1>House 2>House 3>House 4) on the nonlinear structural response. The results indicate that the record selection procedures have significant influence on the probabilistic relationship between spectral acceleration at the fundamental vibration period and maximum inter‐story drift ratio, highlighting the importance of taking into account response spectral shapes in selecting and scaling ground motion records. Subjected to ground motions corresponding to the return period of 2500 years, House 1 is expected to experience very limited extent of damage; Houses 2 and 3 may be disturbed by minor damage; whereas House 4 may suffer from major damage occasionally. Finally, we develop statistical models of the maximum inter‐story drift ratio conditioned on a seismic intensity level for wood‐frame houses, which is useful for seismic vulnerability assessment. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

细胞小片处理对马氏珠母贝育珠效果影响   总被引：1，自引：0，他引：1  

邓岳文  邓陈茂  杜晓东  符韶  王庆恒 《海洋湖沼通报》2011,(3):46-50

以马氏珠母贝选系F2为实验材料,按照马氏珠母贝常规技术进行插核手术,并经过池塘休养和海区养殖过程,比较了细胞小片黏液处理和保养对马氏珠母贝育珠效果影响.实验设为4组:细胞小片黏液处理组(A)、细胞小片保养组(B)、同时进行细胞小片黏液处理和保养组(C),对照组(D),同时利用H E染色观察比较A和D组细胞小片显微结构的...  相似文献   

Radiocarbon constraints on the Holocene flood deposits of the Ning‐Zhen Mountains,lower Yangtze River area of China     

Shi‐Yong Yu  Cheng Zhu  Fubao Wang 《第四纪科学杂志》2003,18(6):521-525

Lying athwart both the temperate and subtropical zones, the Ning‐Zhen Mountains are particularly prone to extreme floods in the summer months when cold fronts collide with the subtropics‐derived warm airmasses. The Holocene flood deposits in the region may provide a long‐term perspective on hydrographical change and its palaeoclimatic implications. Radiocarbon dates on carbonised wood preserved in flooding sediments reveal that the region has experienced a number of catastrophic floods throughout the middle Holocene. These extreme flooding events cluster into three periods: (i) 9200–8200 cal. yr BP, (ii) 7600–5800 cal. yr BP and (iii) 5200–4000 cal. yr BP, corresponding to the times when the East Asian monsoon has been intensified under warm conditions. The significant falls in flooding frequency around 8200 cal. yr BP, 5800 cal. yr BP and 4000 cal. yr BP may have resulted from substantial reduction in regional precipitation, probably associated with meridional displacement of the planetary frontal system. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Video monitoring of in-channel wood: From flux characterization and prediction to recommendations to equip stations     

Zhi Zhang  Hossein Ghaffarian  Bruce MacVicar  Lise Vaudor  Aurélie Antonio  Kristell Michel  Hervé Piégay 《地球表面变化过程与地形》2021,46(4):822-836

Wood flux (piece number per time interval) is a key parameter for understanding wood budgeting, determining the controlling factors, and managing flood risk in a river basin. Quantitative wood flux data is critically needed to improve the understanding of wood dynamics and estimate wood discharge in rivers. In this study, the streamside videography technique was applied to detect wood passage and measure instantaneous rates of wood transport. The goal was to better understand how wood flux responds to flood and wind events and then predict wood flux. In total, one exceptional wind and seven flood events were monitored on the Ain River, France, and around 24,000 wood pieces were detected visually. It is confirmed that, in general, there is a threshold of wood motion in the river equal to 60% of bankfull discharge. However, in a flood following a windy day, no obvious threshold for wood motion was observed, which confirms that wind is important for the preparation of wood for transport between floods. In two multi-peak floods, around two-thirds of the total amount of wood was delivered on the first peak, which confirms the importance of the time between floods for predicting wood fluxes. Moreover, we found an empirical relation between wood frequency and wood discharge, which is used to estimate the total wood amount produced by each of the floods. The data set is then used to develop a random forest regression model to predict wood frequency as a function of three input variables that are derived from the flow hydrograph. The model calculates the total wood volume either during day or night based on the video monitoring technique for the first time, which expands its utility for wood budgeting in a watershed. A one-to-one link is then established between the fraction of detected pieces of wood and the dimensionless parameter “passing time × frame rate ”, which provides a general guideline for the design of monitoring stations.  相似文献   

Remote sensing of large wood in high-resolution satellite imagery: Design of an automated classification work-flow for multiple wood deposit types     

Alicia Sendrowski  Ellen Wohl 《地球表面变化过程与地形》2021,46(12):2333-2348

Wood researchers increasingly rely on remote-sensing products to augment field information about wood deposits in river corridors. The availability of very high-resolution (<1 m) satellite imagery makes capturing wood over greater spatial extents possible, but previous studies have found difficulty in automatically extracting wood deposits due to the challenge in distinguishing wood from spectrally similar corridor features such as sand. We also lack knowledge on the spectral properties of different wood deposit types in multiple depositional environments. In this work, we explore image classification work-flows for four wood deposit types in three North American environments: in-channel jams deposited in the Tatshenshini River in Alaska, USA; a wood raft on the Slave River in Northwest Territories, Canada; and wood deposited along a lakeshore and coastal embayment in the Mackenzie River Delta in Northwest Territories, Canada. We compare classification results of object-based and pixel-based image analysis with supervised [support vector machine (SVM)] and unsupervised (ISO clustering) classifiers. We evaluate several accuracy assessment parameters and achieve overall classification accuracies of 65–99%, showing automated image classification is a possible approach for analysing wood across larger areas. We also find that wood sensitivity in the classification ranged from 0 to 95%, indicating that some techniques are better suited to wood capture than others. We find that supervised classification produced more accurate wood maps, though there is large variation in classification outcomes across environments related to spatial arrangement of wood in the landscape. We discuss the influence of depositional environment on classification and provide recommendations for designing a wood classification work-flow.  相似文献   

内蒙古银根-额济纳旗盆地白垩系中硅化木化石及其沉积环境     

张明震  戴霜  陈世强  张文防  张永全  赵杰  张莉莉  张瑞 《地质学报》2013,87(8)

内蒙古银根额济纳旗盆地是我国北方重要的中一新生代陆内含油气盆地,主要出露白垩系冲洪积-河湖相碎屑岩及火山岩夹层.本文描述了在盆地东南部下白垩统巴音戈壁组下段(1号)和苏红图组二段底部(2号)发现的上、下两处原始埋藏的硅化木化石,并探讨了早白垩世时期盆地沉积时的气候环境.两处化石均保存完好,表面结构较为完整.巴音戈壁组上部和苏红图组下部泥岩段孢粉分析结果显示地层时代为早白垩世中晚期.同时,孢粉植物群揭示该时期银根-额济纳旗盆地气候环境温暖湿润,植被茂盛.根据化石保存特征和产出位置的地层岩性,初步推测1号硅化木化石点系冲洪积物快速堆积所致,2号硅化木化石点系火山喷发物瞬间埋藏所致,其埋藏时代大致为早白垩世晚期.  相似文献   

浙江宁海早上新世枫香树属和栎属化石木及其古环境意义^*          下载免费PDF全文

程业明  扆铁梅  李承森 《古地理学报》2013,15(1):105-112

对发现于浙江省宁海县茶园乡道士桥村附近的上新统嵊县群中的多个化石木材料进行了解剖研究,并对其分类和系统位置进行了讨论。根据解剖特征鉴定出2种化石木。一种为久内枫香树（Liquidambar hisauchi）,属于金缕梅科枫香树属,其组合特征为：生长轮明显;散孔材;梯状穿孔板具横隔10～23条;螺纹加厚仅出现在导管末端;导管直径在50～100μm之间;射线宽1～3列。另一种为岛仓栎（Quercus shimakurae）,属于壳斗科栎属,其组合特征为：生长轮极明显;环孔材;单管孔;晚材管孔火焰状径列;早材管孔直径最大达300μm,明显比晚材管孔大;单穿孔;轴向薄壁组织星散聚合状和离管带状;射线具单列和极宽2种类型。本研究从大化石角度进一步证明栎属和枫香树属为当时植被的重要组成成分。  相似文献   

Implementation and validation of video monitoring for wood budgeting in a wandering piedmont river,the Ain River (France)     

Bruce MacVicar  Hervé Piégay 《地球表面变化过程与地形》2012,37(12):1272-1289

The transport of wood in rivers during floods is an important process that underlies differences in habitat and morphology between water courses and regions. Quantitative data are needed to properly address management objectives and balance wood budgets. In this study we use a streamside video camera to detect wood passage and measure quasi‐instantaneous rates of wood transport in the Ain River, France. The objectives are to verify the procedure, describe the relation between wood transport and discharge, and construct and validate a wood budget for the reach upstream of the camera. Verification of the procedure includes tests of detection frequency, wood velocity, and piece size. A log base two transformation is proposed to classify wood by piece length. It was found that a wood transport threshold occurs at approximately two thirds of the bankfull discharge. Wood transport follows a positive linear relation with discharge up to the bankfull discharge but is both more variable and less sensitive to discharge when the floodplain is inundated. Transport rates are approximately four times higher on the rising limb of the hydrograph than on the falling limb. Wood transport estimates from a three‐stage rating curve are two to 10 times higher than those from a wood budget using local and aerial surveys of upstream dynamics. Future work should address uncertainties related to wood diameter measurements, sampling length and frequency, and antecedent floods. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Forest biodiversity assessment in Peruvian Andean Montane cloud forest     

Alicia Ledo  Sonia Condés  Iciar Alberdi 《山地科学学报》2012,9(3):372-384

Cloud forests are unusual and fragile habitats, being one of the least studied and least understood ecosystems. The tropical Andean dominion is considered one of the most significant places in the world as regards biological diversity, with a very high level of endemism. The biodiversity was analysed in an isolated remnant area of a tropical montane cloud forest known as the "Bosque de Neblina de Cuyas", in the North of the Peruvian Andean range. Composition, structure and dead wood were measured or estimated. The values obtained were compared with other cloud forests. The study revealed a high level of forest biodiversity, although the level of biodiversity differs from one area to another: in the inner areas, where human pressure is almost inexistent, the biodiversity values increase. The high species richness and the low dominance among species bear testimony to this montane cloud forest as a real enclave of biodiversity.  相似文献   

Modelling the time course of shade,temperature, and wood recovery in streams with riparian forest restoration     

Robert J. Davies‐Colley  Mark A. Meleason  Raeme M.J. Hall  J. Christopher Rutherford 《新西兰海洋与淡水研究杂志》2013,47(3):673-688

Action is increasingly being taken in New Zealand and elsewhere to restore ecological function to streams through planting of riparian zones. We used simulation modelling to explore the relative performance of three strategies to restore the riparian zone of a pastoral stream to native forest by: (1) passive regeneration; (2) planting then abandonment of a Pinus radiata plantation; and (3) active restoration by planting selected native trees. We linked the forest model LINKNZ with a shade and temperature model (sWAIORA), and a wood model (OSU_STREAMWOOD) to simulate recovery trajectories for key forest stream attributes in hypothetical streams (1.3–14.0 m channel width) in the central North Island, New Zealand. Both active restoration strategies outperformed passive regeneration in shade, temperature and stream wood volume for most of the simulation time (800 years). Although the abandoned pine plantation provided greatest shade initially (<100 years), active native planting provided the greatest benefits overall. In general, recovery of stream shade (and temperature) is expected within decades, is accelerated by deliberate planting, and is fastest in small streams in which thermal stress from sunlight exposure is greatest. However, full recovery of stream and riparian function may take centuries, being dependent on large trees providing wood to structure the channel.  相似文献