Field test of an intelligent stiffener for bridges at the I-35 Walnut Creek bridge     

William Neff Patten  Jinghui Sun  Guangjun Li  Jeff Kuehn  Gang Song 《地震工程与结构动力学》1999,28(2):109-126

The addition of controllable hardware to structures to mitigate vibration that results from dynamic loads is an emerging area of technological development. The paper describes the results of a research project that was conducted to test a relatively new approach to structural control: an adjustable semi-active hydraulic actuation system that was attached to an in service interstate bridge. The system, which is powered by a 12-volt automative battery, has been tested over a 2- year period. Data indicates that the system reduces truck induced peak stresses by over 50 per cent, and calculations, per NCHRP 299, indicate that the safe life of the structure is increased by approximately 50 yr. The installed cost of the system represents less than 10 per cent of the cost to replace the bridge. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

The Loess/Paleosol record and the nature of the younger Dryas climate in central China     

David B. Madsen  Li Jingzen  Robert G. Elston  Xu Cheng  Robert L. Bettinger  Geng Kan  P. Jeff Brantingham  Zhong Kan 《Geoarchaeology》1998,13(8):847-869

The use of latest Pleistocene-Holocene paleosols in defining Chinese climatic sequences is plagued by poor chronological controls caused primarily by the use of radiocarbon dates derived from bulk soil carbon. Dating of a post-glacial aeolian/paleosol sequence in the Pigeon Mountain basin of north-central China, using culturally deposited charcoal, support a wide array of other data suggesting the Younger Dryas was a period of cooler dryer conditions marked by wide-spread aeolian deposition. Periods of soil formation and higher lake levels bracket this climatic event. Climatic variability immediately before, during and immediately after the Younger Dryas interval is associated with rapid technological elaboration and innovation in the production and use of chipped stone tools, and perhaps, ground stone. © 1998 John Wiley & Sons, Inc.  相似文献   

Origin of post‐Minoan caves and volcaniclastic cave fill,Thera (Santorini), Greece     

Joan M. Ramage  George H. Shaw  Jeff A. Hoffman  Sarah A. Johnston 《Geoarchaeology》2003,18(5):523-539

The Aegean island of Thera (Santorini) was covered by tephra from its cataclysmic Late Bronze Age (ca. 3600 yr B.P.) eruption. Vertical exposures of the eruptive sequence show secondary, nonvolcanic, circular (in cross section) features composed of stratified sediment. Many are inaccessible from the floors of modern quarries and appear to be caves filled with younger sediment, but show no connection to the land surface. A filled cave was found in the wall of a modern gully outside the modern quarries, and a filled cave was found in a terrace scarp, well above the modern gully. Natural (and probably rapid) incision by gullies into the thick tephra deposit left many locations with lateral access to tephra. Inhabitants from post‐Minoan to recent times excavated tephra for materials and buildings, and caves were subsequently filled by sporadic (possibly seasonal) flood events that deposited sediment. These gullies may have provided access for modern tephra removal that isolated the filled caves high on the modern quarry walls. © 2003 Wiley Periodicals, Inc.  相似文献