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post-fire cyclic behavior of reinforced concrete shear walls

Journal of Central South University 2010年第5期17卷 1103-1108页

作者：刘桂荣宋玉普曲福来 State Key Laboratory of Costal and Offshore Engineering Dalian University of Technology School of Civil Engineering and Communication North China Institute of Water Conservancy and Electric Power

The effects of fire exposure,reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete(RC) shear walls were *** RC shear walls were tested under low cyclic *** to the cyclic test,three specimens were exposed to fire and two of them were also subjected to a constant axial *** results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8%after exposure to elevated *** the reductions in the energy dissipation and initial stiffness are 59.2%and 51.8%,respectively,which are much higher than those in the ultimate ***,this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after *** addition,the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

关键词： shear wall reinforced concrete post-fire seismic behavior low cyclic loading

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Salvage logging versus natural regeneration post-fire practices in a forest: Soil chemical and microbial aspects

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Open Journal of Ecology 2012年第1期2卷 29-37页

作者： Orit Ginzburg Yosef Steinberger The Mina & Everard Goodman Faculty of Life Sciences Bar-Ilan University Ramat-Gan Israel

The increase in forest-wildfire events around the world has revived the old debate regarding the practice of salvage logging and its effectiveness in comparison to the unlogged, natural regeneration of burned forests. Since the logging of burned trees may have undesirable outcomes in soil systems, such as soil compaction and nutrient losses, these changes could further cause disturbances to soil microbial-community activity. The aim of this study was to examine chemical and biological changes in soil under two post-fire practices: salvage logging and unlogged, natural regeneration of burned areas, in the recently burned Byria Forest in Israel. Results indicated that salvage logging had a short- lived effect on soil chemical and biological properties that was confined mostly to the first year after logging. Soil moisture was greatly affected by salvage logging, and drier conditions were found in the logged compared to the unlogged burned areas. Moreover, logging had a negative effect on microbial biomass, with reduced biomass in the logged compared to unlogged areas, which was more evident during the first year after fire. These findings support the recommendations in the literature to postpone post-fire practices such as logging or, in turn, to combine the two practices in order to create a mosaic of burned-logged and burned-naturally regenerated areas.

关键词： Microbial community Natural regeneration post-fire practice Salvage logging Wildfire

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Vegetation regrowth trends in post forest fire ecosystems across North America from 2000 to 2010

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Natural Science 2012年第10期4卷 755-770页

作者： Shuang Li Christopher Potter NASA Ames Research Center Moffett Field USA

The goal of this study was to determine whether climate has affected vegetation regrowth over the past decade (2000 to 2010) in post-fire forest ecosystems of the United States and Canada. Our methodology detected trends in the monthly MODerate resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) timeseries within forest areas that burned between 1984 and 1999. The trends in summed growing season EVI (composited to 8 km spatial resolution) within all burned area perimeters showed that nearly 1.6% post-fire forest area declined in vegetation greenness cover significantly (p post-fire forest area showed a non significant EVI regrowth trend from 2000 to 2010. Regression results detected numerous significantly negative trend pixels in post-fire areas from 1994-1999 to indicate that forest regrowth has not yet occurred to any measurable level in many recent wildfire areas across the continent. We found several noteworthy relationships between annual temperature and precipitation patterns and negative post-fire forest EVI trends across North America. Change patterns in the climate moisture index (CMI), growing degree days (GDD), and the standardized precipitation index (SPI) were associated with post-fire forest EVI trends. We conclude that temperature warming-induced change and variability of precipitation at local and regional scales may have altered the trends of large post-fire forest regrowth and could be impacting the resilience of post-fire forest ecosystems in North America.

关键词： MODIS EVI post-fire Forest Regrowth Climate Change North America

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Influence of vegetation cover and other sources of variability on sediment and runoff response in a burned forest in South Korea

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Journal of Mountain Science 2017年第2期14卷 296-315页

作者： EWANE Basil Ewane LEE Heon-Ho Department of Forest Resources College of Natural ResourcesYeungnam University280 Daehak-roGyeongsan-siGyeongsangbuk-do712-749South Korea

post-fire field measurements of sediment and run off yield were undertaken in natural rainfall event-basis during five rainy months in Korea on a total of 15 small plots: four replica burned unseeded plots, six replica burned seeded plots, and five replica unburned plots. The main aim was to evaluate the effects of vegetation recovery and spatial distribution patterns on sediment and runoff response between and within the treatment replica erosion plots. Sixyears after the wildfire, total sediment and runoff yield in the burned unseeded plots with 20%-30%vegetation cover was still 120.8 and 20.6 times higher than in the unburned treatment plots with 100%ground cover, 8.3 and 6.7 times higher than in the burned seeded plots with 70%-80% vegetation cover,while only 1.6 and 2.0 times higher than in the burned seeded plots with 50%-60% vegetation cover,respectively. The differences in sediment and runoff yield between the treatment plots was proportional to total vegetation cover, distance of bare soil to vegetation cover, magnitude of rainfall characteristics and changes in soil properties, but not slope *** out of the six within-treatment pairs of two replica plots showed large differences in sediment and runoff yield of up to 6.0 and 4.2 times and mean CV of up to 99.1% and 62.2%, respectively. This was due to differences in the spatial distribution patterns of surface cover features, including aggregation of vegetation and litter covers, the distance of bare soil exposed to vegetation cover closer to the plot sediment collector and micro topographic mounds and sinks between pairs of replica plots. Small differences in sediment and runoff of only 0.9-1.4folds and mean CV of 8.6%-25% were observed where the within-treatment pairs of replica plots had similar slope, total surface cover components and comparable spatial distribution pattern of vegetation and bare soil exposed surface covers. The results indicated that post-fire hillslopes undergoing effective

关键词： Bare soil exposed Vegetation cover post-fire Soil erosion Spatial distribution patterns Replica erosion plots

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Mechanical Behavior of Tubular T-joint after fire

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Journal of Shanghai Jiaotong university(Science) 2011年第1期16卷 97-104页

作者：靳猛赵金城常静刘明路 School of Naval Architecture Ocean and Civil EngineeringShanghai Jiaotong University Construction and Infrastructure Department Shandong Jiaotong University

This paper presents experimental results of the post-fire behavior of tubular *** research aims at the failure modes and the residual strengths of the T-joints after *** tests of full-scale tubular T-joints are *** first one is carried out to study the mechanical behavior of T-joints under ambient *** other two tests are performed to study the influence of pre-load,heating and cooling phase on residual load-bearing capacity of the tubular *** test results show that the sustained axial load on the brace has remarkable influence on the residual deflection of the T-joints which is cooled down to room *** results of the experiments also indicate that the axial load level and heating and cooling history have more significant effects on the compressive stiffness of the T-joints than the residual *** the numerical study,the result of finite element model agrees well with the test *** work in this paper provides a basis for further parametric analysis and theoretical study on the structural evaluation after fire.

关键词： T-joints post-fire residual strength numerical analysis

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