海岸带防护林4种树木的风压应力分析

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1、海岸带防护林4种树木的风压应力分析李国旗　安树青　张纪林　吕跃凯　陈兴龙　程晓莉　季永华　沈邦勤摘　要　依据4种主要的海岸带防护林树种的调查数据，计算了各树种不同高度处和不同风压下的应力分布，分析了各树种遭受台风袭击时所受到的弯曲应力。结果发现树种的受害程度与其树冠形状密切相关。杨树和水杉的枝下高和树高之比（L/H)均小于0.22，树冠宽度和树冠高度的比值(Wc/Hc)均小于0.36；刺槐和泡桐枝下高和树高的比值（L/H)均大于0.43，树冠宽度和树冠高度的比值(Wc/Hc)均大于0.54，这是形成杨树和水杉有两个

2、受力点，而刺槐和泡桐只有一个受力点的根本原因。在相同的风压下，无论在树干的任何部位，杨树所受应力超过水杉、刺槐和泡桐2.3、5.0和5.3倍以上，因而杨树的受损程度也最为严重。关键词　海岸带；防护林；台风；弯曲应力中图分类号　S718　　　文献标识码　A　　　　文章编号　1000-2006(1999)04-0076-05TheBendingStressAnalysisof4SpeciesofWoodsCausedbyWindPressureinCoastalShelterForestLiGuoqi　AnShuqin

3、g(DepartmentofBiologicalScienceandTechnologyNanjingUniversity　Nanjing　210093)ZhangJilin　(ForestResearchInstituteofJiangsuProvince)LuYuekai　ChenXinlong　ChengXiaoli(DepartmentofBiologicalScienceandTechnologyNanjingUniversity)JiYonghua　(ForestResearchInstituteofJ

4、iangsuProvince)ShengBangqing　(DongtaiForestFarmofJiangsuProvince)Abstract　Basedonthecollecteddataof4kindsoftreedamagedonAugust19,1997,thebendingstressanditsdistributioninvariousheightofstemandundervariouswindpressurearecalculatedinthispaper.Theresultsindicatet

5、hatthereisacloserelationshipbetweenthedamagedegreesofspeciesandtheircrownshapes.Itcanbereflectedbytworatiosasfollows:oneistheratio(L/H)ofheightatthebottomofcrown(L)totheirindividualheight(H),theotheristheratio(Wc/Hc)ofcrownwidth(Wc)tocrownheight(Hc).ForPopulus

6、deltoidesandMetasequoiaglyptostroboides,bothoftheformerindexarelessthan0.22andbothofthelatterindexarelessthan0.36.Tothecontrary,forRobiniapseudoacaciaandPaulowniafortunei,bothoftheformerindexaremorethan0.43,andbothofthelatterindexaremorethan0.54.Thedifferences

7、ofL/HandWc/Hcamongthe4speciesbringaboutthattherearetwopointsofbendingstressforPopulusdeltoidesandMetasequoiaglyptostroboides,andthereisonepointforRobiniapseudoacaciaandPaulowniafortunei.Undercertainwindpressure,thebendingstressofpoplaristhebiggestoneamongthe4k

8、indsoftreeineverypositionofitstrunk,thestressatanyheightismorethan2.3timesofMetasequoiaglyptostroboides,5.0timesofRobiniapseudoacacia,and5.3timesofPaulowniafortuneirespectively.The