【作者】 张苏俊；

【导师】 华毓坤； 卢晓宁；

【作者基本信息】 南京林业大学 ， 木材科学与技术， 2017， 博士

【摘要】 木结构建筑因其舒适性仍是世界各国人们心目中理想的生活和工作场所。速生木材由于其自身性质的缺陷,一般无法直接作为主要结构构件。本文首先对速生杉木和杨木进行改性并进行了相关的试验和研究,然后研究了其在三角屋架屋盖体系、轻型木框架结构以及装配式密排小柱距轻质木框架建筑中的应用。采用低分子酚醛树脂对速生杉木、杨木进行浸渍处理,并对素材和浸渍材进行顺纹抗拉强度、顺纹抗压强度、抗弯弹性模量和抗弯强度测试;对胶合木梁进行抗弯强度和胶合木柱进行轴心受力性能试验,结果表明:(1)浸渍材的力学性能都要优于杉木素材,顺纹抗拉强度提高了14%,顺纹抗压强度提高了10%,抗弯弹性模量提高了13%,抗弯强度提高了11%。同时浸渍材各项力学性能的标准差都相应的减小,有利于杉木应用于结构构件;(2)经过表面浸渍增强材贴面后,速生材胶合木的力学性能有所改善,抗弯强度增加了14%,抗弯弹性模量增加了7%。试验中胶合梁的抗弯破坏都是在两点加载处,表现为断裂和胶层破坏,符合标准中的破坏形式;(3)杉木柱试件在试验加载后期,可以看到柱中有明显的弯曲,杉木柱出现失稳破坏;4根试件的极限荷载均大于理论值,说明规范中稳定系数取值趋于保守。将改性速生材应用于三角形屋架屋盖体系中。首先根据《木结构设计规范》要求对速生杨木檩条、改性速生杨木胶合木三角桁架进行了强度和变形验算;其次采用制图软件UG NX5对屋架进行绘图,并导入有限元软件ANSYS对屋架进行了有限元分析,分析结果显示:(1)檩条采用速生杨木LVL,经计算强度、刚度均满足现行规范要求;(2)屋架弦杆、腹杆均采用改性速生杨木胶合木,经计算强度、刚度均满足现行规范要求;(3)有限元分析结果显示,屋架迎风面弦杆位移最大,对最大位移杆件计算其扰度为3.6mm,小于允许最大挠度5.744mm。利用第二强度理论,可以判断速生改性杨木的最大伸长线应变在极限范围内,屋架结构及截面尺寸满足要求;(4)屋架构件的强度和刚度均满足《木结构设计规范》GB50005-2003要求,速生杨木和改性杨木胶合木能够应用于三角形屋架屋盖体系,并已建试验用房。研究了轻型木框架结构房屋在水平风荷载下扭转性能,并利用改性速生杉木建造了轻型木框架房屋。首先研究了轻型木框架结构房屋剪力墙在水平风荷载作用时内力的计算方法,同时通过有限元软件ANSYS模拟剪力墙对称结构和不对称结构房屋在水平风荷载作用时,由于偏心产生扭矩对房屋剪力墙受力的影响。通过具体实例房屋的有限元分析,研究轻型木框架结构房屋在水平风荷载作用时房屋受力及变形情况。研究表明:(1)当(剪力)墙群重心偏离房屋平面形心较远且风荷载较大时,由于房屋受扭会在各剪力墙中产生较大的水平力,距离剪力墙群重心越远受力越大;(2)当(剪力)墙群重心与房屋平面形心重合时,在水平风荷载作用下,房屋中平行于风向的墙体起到主要的抗剪切作用,且各墙体中的剪力大小与其剪力墙的刚度大小成正比,每片墙体中剪应力分布随着与风荷载作用面距离增大而减小。垂直于风向的墙体中只有风荷载直接作用墙体可以承担少许剪力,其他墙体抗剪作用可以忽略不计;(3)偏心水平风荷载作用下房屋产生扭转变形,墙体中扭转应力的分布规律是距离重心位置越远的墙体扭转应力越大,同一片墙体上扭转应力分布情况是两端扭转应力很小,中间各点扭转应力增大趋于相等,部分剪力墙中应力峰值相比无扭矩时成倍增长;(4)风荷载作用下轻型木框架房屋处于剪切和扭转状态,墙体的破坏不同于一般的剪切破坏。内部平行风向的墙体、风荷载直接作用的墙体、距离房屋形心较远的墙体均为薄弱环节,必须对这些墙体进行抗剪切强度验算;(5)根据当地主频风向,在房屋内部多设置与风向平行的墙体(纵墙),纵墙上应尽量减少开洞,从而避免墙体剪力过大发生剪切破坏;保证楼盖具有足够的刚度以确保有效传递水平荷载;洞口上方与楼盖之间的墙体可以承担和传递剪力,应尽量保留,使剪力墙体现完整性;(6)在轻型木框架房屋设计的时候,尽量使房屋中墙体布置规则,重心与形心重合。在房屋内部多布置与该地区常年主频风向平行的墙体,在平行主频风向墙体的1/3长度范围内多布置垂直于主频风向墙体增强抗剪墙体的整体稳定性。利用改性速生杉木设计建造了装配式密排小柱距轻质木框架房屋并进行有限元分析。首先进行设计计算,再通过有限元分析,探讨了木框架结构在风荷载作用下的受力及位移响应,同时分析了在顺风方向加入横墙之后风荷载作用下结构的内力情况,探讨了顺风横墙对整体结构刚度的影响,得到如下结论:(1)在风荷载作用下横墙的加入明显提高了轻型木框架结构顺风方向的刚度,同时对于垂直风向方向的位移也有显著的抵抗作用,这是由于横墙的加入使得结构更趋于一个整体,横墙与木框架共同作用,故对结构刚度横向及纵向刚度有明显提高;(2)横墙的引入明显降低了风荷载作用下木材的最大应力,横墙引入使得结构形成整体受力,结构的整体性更好;(3)垂直横墙方向的吸力对木框架结构的X方向的位移几乎没有影响,这就更加验证了现场试验加载模拟风荷载而不考虑横向水平作用力的正确性;(4)在垂直横墙的吸力作用下,木框架的应力较无垂直横墙的吸力的框架要稍大,但所求应力结果明显小于材料的承载力。通过对试验房屋施加侧向荷载,测试了房屋的变形能力及受力状况。试验结果表明:(1)结构在侧向荷载作用下,二层楼面处的最大变形仅10.3mm,屋面处最大变形仅5.8mm,卸载后变形能在短时间内基本恢复,基本属于弹性变形,且房屋的层间位移较小。装配式轻质木结构房屋在水平荷载作用下,当侧向位移最大值小于《木结构设计规范》(GB 5005—2003)H/500时,侧向变形基本处于弹性范围之内;(2)由于房屋竖向受力构件上下层之间采用钢连接件现场安装,节点刚性不足,致使房屋整体在受力的分配和传递过程都属于柔性模式;(3)横向墙体在侧向荷载作用下起到了抗侧移的主要作用;(4)因施加的侧向荷载与房屋的形心位置不重合,房屋发生了少许扭转变形;(5)试验过程中未发现主要受力构件出现裂缝或破坏现象,说明采用速生改性杉木建造装配式轻质木结构房屋是可行的,能够满足房屋的正常使用要求。更多还原

【Abstract】 The wooden structure buildings are still the ideal living and working place in people’s mind because of its comfort.The fast-growing wood can not be directly used as structural component due to the defects in its nature.This paper begins with the modification of fast-growing china-fir and poplar,and applies them to the Triangular roof and fabricated lightweight wood frame building.Impregnation treatment on fast-growing china-fir and poplar with phenol-formaldehyde resin of low molecular weight and test the tensile strength parallel to grain,compression strength parallel to grain,bending modulus of elasticity,bending strength of primal wood and soaked wood.Experimental studies on bending resistance properties of glued laminated timber beams and the axially load bearing capacity of glued laminated timber columns were carried out.Tests shown that:(1)The mechanical property of soaked wood are better than primal wood,the tensile strength parallel to grain was increased by 14%,the compression strength parallel to grain was increased by 10%,the bending modulus of elasticity was increased by 13%,the bending strength was increased by 11%.At the same time,the standard deviation of the mechanical properties of the soaked wood is reduced accordingly,which is beneficial to the application of China fir in structural members.(2)The mechanical properties of glued laminated wood has been improved after the surface with impregnated reinforced wood,the bending strength was increased by 14%,the bending modulus of elasticity was increased by 7%,in the test,the bending failure of the glued laminated timber beams is at two loaded points,the beams were fracture destruction and adhesive layer destruction,the failure mode in accordance with the standard.(3)The glued laminated timber columns have obvious bending and the unstable failure occurred during the later loading period,the ultimate load of 4 columns are larger than the theoretical value,it illustrated that the stability coefficient of the specification is still conservative.Apply the modified fast-growing to the Triangular roof engineering,firstly,checking the strength and deformation of the fast-growing poplar purlin and the modified fast-growing poplar triangle truss according to the code for design of timber structures,secondly,the drawing software NX5 UG is used to draw the wooden truss and the finite element analysis was carried out,the analysis results shown:(1)The purlines are adopted with fast-growing poplar and the calculated strength and stiffness meet the requirements of the current specification.(2)The truss chord and web members are adopted with modified fast-growing poplar and the calculated strength and stiffness meet the requirements of the current specification.(3)The maximum displacement of the timber truss in the chord members of windward side,the maximum immunity is 3.6mm is less than the allowable value 5.744 mm.These determine the maximum elongation of the material is in the limit range and the truss structure and section size are meet the requirements according to the second strength theory.(4)The strength and stiffness of timber truss members are meet the requirements of the code for design of timber structures,the fast-growing poplar and the modified fast-growing poplar can be used in the Triangular roof engineering.Apply the modified fast-growing to light wood frame,the calculation method of the internal force of the shear wall of the light wood frame structure in the horizontal wind load is studied.Using finite element software ANSYS to simulate the effect of eccentric torque on housing when symmetrical and asymmetric structure of shear wall under horizontal wind load at the same time.Based on the finite element analysis of specific house,the stress and deformation of the house in the horizontal wind load are studied.(1)When the barycenter of the shear wall group is far from the centroids of the house and under the action of strong wind load,will produce large horizontal force in the shear wall,the longer the distance is,the greater the force will be.(2)Under the action of axial horizontal wind load,the wall parallel to the direction of the wind plays a major role in shearing,the magnitude of the shear force in the wall is in proportion to the stiffness of the shear wall,the shear stress distribution in the wall increase with the decrease of the wind load action surface.Only the wall which under the directly action of wind load and perpendicular to the wind direction can bear the shearing force,and the shear resistance of other walls can be negligible.(3)Under the action of eccentric horizontal wind load,torsional deflection occurred in the house,the regularity of torsional stress distribution is the farther from the barycenter of the wall,the stress is larger,the regularity of torsional stress distribution in the same wall is the torsional stress at two ends is very small,the torsional stress at the middle points increases and tends to be equal,the stress grown exponentially compared to no torque effect.(4)Under the action of wind load,the light wood frame house is in a state of shear and torsion,and the failure of the wall is different from the normal shear failure.Internal parallel wind walls,walls of direct action of wind load,walls far from the housing center are the weak links.It is necessary to check the shear strength of these walls.(5)According to the local frequency of wind direction,in the interior of the structure set more walls parallel to the direction of wind(longitudinal wall)and longitudinal wall should minimize openings to avoid shear failure of wall shear wall.Thirdly,make sure that the floor has enough stiffness to ensure transfer effective horizontal load.Lastly,as far as possible to retain wall between the top of the hole and the floor,the shear walls embody completeness and play a role in bearing and transferring load.(6)When designing the light wood frame houses,we should try to make the wall arrangement regular and center of gravity and centroid coincident.Multi layout walls perpendicular to the main frequency of wind direction in the area of length of the 1/3 wall with parallel main frequency wind direction wall enhance the overall stability of shear wall.In this paper,we build frame with small column span house made of modified fast-growth Chinese fir.First,it was designed and analyzed through the finite element analysis.We discussed the wood frame structure’s force and displacement response under wind load;and the structure internal force under the effect of wind load are also analyzed in the paper when the transverse wall was joined in the downwind direction.The influence of the lateral wall on the overall structural stiffness is discussed,and the conclusions are as followed:(1)The light wood frame structure’s stiffness of the wind direction under wind load is improved significantly when the the side wall along the wind load’s direction was joined in,and also has a significant resistance to the displacement of the vertical wind direction.This is due to the addition of the side wall which makes the structure more tend to a whole,the side wall and the wood framework as a whole,so the structural stiffness of the wind and the lateral stiffness increased significantly.(2)The stress of downwind and crosswind direction under the action of wind load is lower when the downwind side is joined in.The structure form resist the force as a whole,the structure integrity is better when it was introduced into.(3)The suction of the vertical side wall has little effect on the displacement of the wind direction of the wood frame structure,which verifies the correctness of the load simulation wind load without considering the lateral horizontal force.(4)The horizontal stress of the wood frame is slightly larger than that of the horizontal force under the horizontal force of the vertical wall,but the stress result is obviously smaller than the strength of the material.The deformation capacity and stress state of the house was tested when the lateral load was applied to.The detrimental situation is that the load was applied to the house as a point load which is equal to the maximum uniform wind load.Under this case,the maximum deformation of the two floor is only 10.3mm,the maximum deformation of the roof is only 5.8mm.The deformation can be recovered in a short time after unloading,so it is elastic deformation.And the layer displacement of the house is small.(1)Test results showed that the lateral deformation is in elastic range when assembly of light wood structure buildings is under horizontal load and the lateral displacement of the maximum value is less than H/500 which is provided in the code for design of timber structures(GB 5005-2003);(2)Due to the lower and upper layer of the vertical component of the building,the steel connection piece is installed on the spot,and the joint rigidity is insufficient,so that the whole distribution and the transferring process of the house are flexible mode;(3)The lateral wall plays a major role in resisting lateral displacement under lateral loads;(4)The houses had a little torsional deformation because the site where the lateral load applied to is not coincident with the house’s center position;(5)In the course of the experiment,there was no crack or damage in the main stress components.As a result,it is feasible to use the fast growing Chinese fir to build the assembly light beam structure,which can meet the requirement of the normal use of the house.更多还原