斜螺钉连接胶合木梁柱节点抗侧性能研究

设计了一种适用于装配式胶合木建筑的新型梁柱斜螺钉连接节点。采用全螺纹自攻螺钉将金属钢板和梁、柱分别连接,通过高强度螺栓完成梁和柱的基础连接。试验表明:3组斜螺钉连接胶合木梁柱节点低周反复试验得到的弯矩-转角滞回曲线,在拉向和压向加载循环中基本对称,呈"反S形",转角较大时,表现出一定的"捏缩"现象,随着循环次数的增加,骨架曲线的斜率逐渐减小,出现了刚度退化,表明节点在反复荷载作用下因累积吸收的能量而产生损伤;全螺纹自攻螺钉可以有效地将胶合木梁柱节点处的荷载传递到胶合柱的内部,具有较强的抗侧承载性能;节点在变形角1/100循环前,耗能能力处于较低水平,随着转角的增大,耗能能力明显增强,直至最后循环,节点仍保持较强的耗能能力。     

水青冈木-自攻螺钉复合榫连接节点单剪性能

对比研究自攻螺钉、水青冈木榫和水青冈木-自攻螺钉复合榫3种连接节点的单剪承载性能,采用特征值分析法对单剪力-位移进行分析,获得最大荷载、极限荷载、屈服荷载、初始刚度、延性系数、能耗和最终位移等七个参数。结果表明:1)除了初始刚度,采用自攻螺钉的连接节点承载性能优于水青冈木榫连接节点;2)复合榫连接节点的承载力呈现两个极大值峰,第一个极大值高于水青冈木榫连接节点最大值2 kN,第二个极大值高于自攻螺钉连接节点最大值0.7 kN;3)复合榫连接节点的最终位移介于水青冈木榫连接节点和自攻螺钉连接节点之间,耗能能力和自攻螺钉连接节点相当,其他参数均优于自攻螺钉连接节点和水青冈木榫连接节点。综合参数分析,水青冈木-自攻螺钉复合榫能够有效结合自攻螺钉和水青冈木榫的优良特性     

斜螺钉2种角度不同组合形式对钢板-正交胶合木剪切性能的影响

【目的】制作一种采用自攻螺钉连接的钢板-正交胶合木节点，探究螺钉不同钉入角度不同组合形式对节点力学性能的影响，并依据现有的理论计算模型与试验值比较对计算模型进行优化，为新型连接件的开发和应用提供理论模型和参考。【方法】参考美国标准（ASTM D1761-12）以1 mm·min^-1的速度匀速加载，对夹角为45°和90°2种自攻螺钉钉入角度进行6种不同组合形式的抗剪试验，记录分析受剪切节点的破坏形态并对比各组试件的荷载-位移曲线、承载力、刚度和能量耗散。【结果】试件主要破坏模式包括2颗钉同时被剪断、钉未被剪断但产生塑性铰和钉未被剪断但同时被拔出。6组试件均出现一侧钉被剪断的破坏模式，组J-Cross45°T和S-Double45°T出现钉未被剪断而被拔出、组S-45°T-45°C出现钉未被剪断而产生塑性铰的破坏模式。组J-Cross45°T、J-Double45°T、S-Double45°T的承载力和刚度均远高于组S-45°T-45°C、S-90°-45°C、S-90°-45°T,组S-90°-45°C的能量耗散和承载力对应位移最大。【结论】对于承载力、刚度、能量耗...     

自攻螺钉连接正交胶合木抗剪承载力研究

采用自攻螺钉(Self-tapping screw,STS)连接正交胶合木(Cross-laminated timber,CLT),对5种不同参数的连接试件进行单调加载和分级加载试验,测试其抗剪承载力。结果表明,增加STS长度、直径,可明显提高CLT连接试件的抗剪承载力;钉入角度为45°比钉入角度30°时的抗剪承载力提高了28.3%;主侧材对接、STS左右双向斜钉是一种较优的连接形式,比搭接的抗剪承载力提高了50.7%。     

钢夹板—螺栓连接胶合木抗剪性能试验研究

为了研究钢夹板—螺栓连接胶合木的抗剪性能,以东北落叶松胶合木—钢夹板螺栓连接件为研究对象,共设计12组(36个)钢夹板—螺栓连接胶合木进行剪切静载试验,结合理论分析和试验结果表明:材料规格和螺栓数目相同时,螺栓错列布置的抗剪能力明显高于并列布置;随着螺栓列数的增加,屈服荷载与极限荷载明显提高,且螺栓列数与剪切荷载呈非线性关系;在多螺栓连接件中,随着螺栓间距的增大,连接件的初始刚度与屈服后刚度呈减小趋势,极限荷载与屈服荷载呈增大趋势。     

日本柳杉木构件内嵌钢填板销连接横纹承载性能

【目的】研究日本柳杉木构件内嵌钢填板销连接在横纹荷载作用下的破坏机制和承载性能,为木结构梁、柱构件金属件连接时梁端销连接设计提供依据。【方法】在梁端部开槽钻孔后将单个钢销连接到内嵌钢填板,分别对日本柳杉锯材梁和胶合木梁进行横纹荷载作用下的弯曲剪切加载试验,按照日本通行数据分析方法确定销连接短期承载力标准值,并与5个不同国家标准规定的屈服荷载计算值进行比较。【结果】加载初期,荷载-位移曲线呈线性关系,构件处于线弹性阶段,随着位移增加曲线呈非线性,构件进入弹塑性阶段,当位移增加到一定数值,梁端出现初始脆性开裂,荷载瞬间急速减小,随后荷载又随位移增加再次上升,加载至极限状态时,梁构件产生劈裂破坏丧失承载力;最终的破坏形态为梁构件沿销孔水平剪切面开裂、销连接屈服模式Ⅲ型;通过足尺试验得到断面尺寸120 mm×240 mm锯材梁和胶合木梁的钢填板单个销连接短期承载力标准值取决于屈服荷载,分别为8.6和13.7 k N,初始开裂对应的荷载平均值分别为15.0和21.1 k N,屈服荷载平均值分别为14.50和15.00 k N,最大荷载平均值分别为27.0和30.8 k N。【结论】胶合木梁钢填板销连接的最大荷载和屈服荷载平均值均大于锯材梁,且变异系数明显小于锯材梁,含水率低而变异小,从而导致试验获得胶合木梁销连接的短期承载力标准值明显高于锯材梁,当销连接作为中小断面梁柱构件的主要连接方式时,宜选用强度等级确定、质量合格的胶合木作为木构件,比锯材具有更高的连接承载力。梁端销连接节点承载力与单个销连接承载力和销数量具有良好的相关性,可作为梁柱节点梁端销连接设计依据。销连接部位发生销屈服后木材开裂,初始开裂取决于木材抗剪强度、横纹抗拉强度和销所在的梁高部位以及销孔到梁端的距离,发生初始开裂后钢销仍能起到支撑作用,连接节点延性较好;锯材梁和胶合木梁短期承载力标准值与标准中规定的屈服荷载公式计算值吻合度较好。各国标准中关于脆性破坏计算公式均能较好预测销连接木材的脆性破坏,与试验值比较,日本标准对于劈裂破坏的计算值最为接近,欧洲和加拿大标准的计算结果更趋于保守,我国现行标准在销连接设计中尚未考虑木材的脆性破坏,今后应进一步研究完善销连接计算公式和参数,更好地保证木构件连接安全可靠度。     

单调荷载下三层正交胶合木企口节点的剪切性能

为了研究3层正交胶合木(CLT)企口连接的连接性能,对3种不同榫头长度的正交胶合木企口连接试件和传统半搭接连接试件进行准静态单调加载剪切测试。分析企口试件的破坏模式,比较企口试件与半搭接试件在承载能力、刚度以及延性方面的改变,并对比3种不同榫头长度对CLT企口节点抗剪性能的影响。测试使用全螺纹自攻螺钉,垂直CLT板宽面单侧打入,企口连接的榫头长度分别为35,50和65 mm,半搭接连接的搭接长度为50 mm。参照欧洲标准EN 26891-1991进行准静态单调加载。结合试验现象和数据进行了分析比较,结果表明:企口试件的主要破坏现象为STS屈服、钉帽拉穿和木材销槽承压破坏,同时,得益于企口连接的剖面形状,试件在整个加载过程中保持了良好的完整性,未发生面外偏转。半搭接试件易发生面外偏转、钉尖拔出、构件分离。3种榫头长度的企口连接相较半搭接连接在最大承载力、初始刚度和延性方面都有提升。榫头最长的TG-65组试件力学性能相对较好,较半搭接HL-50组试件承载力提升23%、初始刚度提升200%、延性系数提升206%。     

冷弯薄壁型钢-稻草板组合墙体抗剪性能研究

为研究冷弯薄壁型钢-纸面稻草板组合墙体力学性能,对4面冷弯薄壁型钢-纸面稻草板组合墙体试件进行了单调水平抗剪性能试验。分析了各试件破坏形态和破坏过程,得到组合墙体的屈服荷载、极限荷载及延性系数、抗侧移刚度等性能指标。研究结果表明:冷弯薄壁型钢与纸面稻草板通过自攻螺钉连接组合方式合理,组合效应良好;组合墙体经历弹性、弹塑性、破坏三个阶段,其主要破坏模式为边立柱底部局压屈曲,部分纸面稻草板在螺钉孔处被撕裂;组合墙体具有较大的抗剪承载力,延性系数和抗侧移刚度等指标表现良好;施加上部竖向荷载使组合墙体抗剪承载力降低,带有斜撑的组合墙体能够显著提高抗剪承载力。该组合墙体抗剪承载力和抗侧移刚度对于实际工程具有参考意义。     

典型直榫梁柱节点在现代木结构中的应用研究

基于Abaqus有限元分析,对不同榫长的实木榫卯连接梁柱节点和榫长为75 mm的不同层数的正交胶合木(CLT)榫卯连接梁柱节点进行数值模拟,分析其受力状态并提取荷载-位移曲线,与使用金属连接件连接的梁柱节点承载力进行对比,探究将榫卯连接应用在现代木结构中的理论依据。研究表明:竖向荷载作用下,榫长75 mm的榫卯连接梁柱节点承载能力处于M8和M10螺栓连接梁柱节点的理论承载力之间;当榫长增大时,节点的最大承载力逐渐提高,榫长150 mm的榫卯节点承载力已经略微超过M12螺栓连接时的理论承载强度,说明榫卯连接梁柱节点在承载能力上可以满足现代木结构建筑的使用要求。由于榫卯节点的承载力主要受到顺纹抗压强度的影响,因此相比于实木连接榫卯节点,CLT榫卯节点的承载力无显著提高。     

基于有限元的板式家具滑轨连接强度分析研究北大核心

为确定板式家具安装重载滑轨时所需自攻螺钉的数量及其安装位置的最优排布方案,采用有限元法对滑轨连接强度进行数值模拟,探讨在滑轨关闭和完全打开两种状态下使用不同数量自攻螺钉和不同孔位安装方案节点的连接强度,并以理论计算值验证其结果。结果表明:以2个螺钉在1、9孔位固定滑轨两端,在滑轨关闭时节点结构可满足要求,在滑轨完全打开时旁板螺钉孔处发生破坏;以3个螺钉固定滑轨,对比不同安装位置的4种方案,以1-2-9安装方案即在距离前端1孔位32 mm处用自攻螺钉加固连接节点的强度为最优,与2个螺钉安装方案相比旁板螺钉孔处的最大等效应力减小50.9%。该研究为板式家具滑轨安装时螺钉数量及其位置的选择、孔位的设计提供参考。     

Investigation of the structural performance of glulam beam connections using self-tapping screws

The characteristic strength properties of structural glulam connections assembled with self-tapping screws were examined following the ASTM testing procedure in the study. Four screw types with various numbers were designated at each connection of the beam–girder structure with different nailing schedules. The results indicated that the maximum load capacity and dissipated energy of a connection fastened with 10-mm self-tapping screws were higher than those with 8-mm screws. And, the screws with both double-threaded sections and fully threaded shanks were higher than those of single-threaded screws. An improvement on the initial stiffness of a connection was found when the number of self-tapping screws increased. The connections assembled with the toe-nailing approach from the beam’s bottom surface provided higher maximum loading capacity, medium initial stiffness, and a larger ductility factor, resulting in higher dissipated energy with less fragile failure. The derived allowable loading values for a beam–girder connection fastened with self-tapping screws using the face-nailing approach were close to the code values for bolted and pinned connections. And, a toe-nailing approach provided higher allowable loads for connections than using a face-nail approach.     

角钢⁃集成材L形组合柱的受压性能研究

为提高装配式木结构中异形柱的力学性能,设计了一种用热压等边角钢和SPF集成材为原料,环氧树脂胶黏剂连接制作的角钢-集成材L形组合柱,作为框架结构或框架剪力墙结构的角柱。以角钢边宽度对L形柱正截面承载力的影响进行了轴压试验研究,并进行ANSYS有限元模拟,以判断模拟预测的准确性。结果表明:角钢-集成材L形组合柱相对于同截面面积的木柱而言承载能力上升37.0%~51.4%,刚度上升36.5%~72.8%,同时L形柱有良好的延性;适当增加L形柱中的角钢边宽度可以使承载能力有效提高,但是其短边处的集成材易产生破裂,增加试件的脆性破坏;集成材之间的环氧树脂胶合界面在破坏前后都性能良好,在材料弹性阶段钢材和木材有效共同受力,承载力计算时需要考虑钢材的塑形增强作用;ANSYS有限元模拟的角钢-集成材L形组合柱弹性模量结果和试验结果一致,误差在10%以内,模拟结果基本可靠。研究成果对于预测角钢-集成材L形组合柱在实际预制装配时的安全可靠性提供了理论依据。     

钢-竹组合楼板受弯试验及变形分析

为了探讨界面滑移效应对钢-竹组合楼板变形的影响,进行6块组合楼板受弯性能试验.试件共分为2组,一组为冷弯薄壁型钢与竹胶板界面仅周结构胶复合,另一组则在胶粘基础上用自攻螺钉强化,对组合楼板破坏形态、承载能力、跨中变形、界面相对滑移等进行研究.分析表明：第一组试件考虑滑移效应的跨中变形计算值与实测值吻合较好,因考虑了跨中附加挠度的影响,理论计算结果与换算截面法相比,其精度大约提高5％,更符合实际情况;第二组由于自攻螺钉的强化作用,整体性能提高很多,材料进入塑形阶段,所建理论模型不符合试验情况,有待进一步研究.     

Measurement of the shearing properties of wood by in-plane shear test using a thin specimen

In this research, in-plane shear tests were conducted for obtaining the shearing properties of wood. Thin strips of western hemlock (Tsuga heterophylla Sarg.) were used for the specimens. Two circular holes were cut along the axial centerline of the wider surface (longitudinal-tangential plane), and then two slots were cut from the holes asymmetrically to each other by varying the inclined angle of the slot with respect to the axial centerline. Shear stress was induced in the area between the holes, which is called the shear zone, by applying a tension load along the long axis of the specimen; the shear modulus, shear strength, and principal strain angle were measured from the shear stress/shear strain relation obtained. Independently of the in-plane shear tests, Iosipescu shear tests were conducted, and the validity of the in-plane shear tests was examined by comparing the test results with those obtained by the Iosipescu shear tests. In addition to the tests, stress distribution in the in-plane shear test was calculated by the finite element method, and the results were compared with those obtained by the actual in-plane shear tests. The following three results were obtained. First, the shear moduli obtained by the in-plane shear tests were close enough to those obtained by the Iosipescu shear tests throughout the range of inclined angle examined here. Additionally, the calculated result of the finite element method also verified the validity of the in-plane shear test for measuring the shear modulus. Thus, the in-plane shear test method examined was effective for measuring the shear modulus. Second, a failure was initiated at the hole edge because of the stress concentration, which was also confirmed by the finite element calculation, and it immediately propagated along the grain in the early stage of the test. Thus, it was difficult to obtain the proportional limit stress and realistic shear strength by the in-plane shear test because of the catastrophic failure in the early stage of the test. Third, since it is desirable that the stress field in the shear zone is close to the pure shear stress condition, we recommend that the slot runs outward from the hole when conducting the in-plane shear test in spite of the independence of the shear strength on the inclined angle.     

Load-carrying capacity of steel-to-timber joints with a pretensioned bolt

Previous experimental studies reported that bolt pretensioning greatly increases the initial stiffness and load-carrying capacity of bolted joints. It is also a matter of great importance to structural designers to understand the effect of pretension on the load-carrying capacities of bolted joints, and this study presents an extended yield model that considers the fastener’s pretension force. In the extended yield model, the load-carrying capacity was defined as the load at a slip of 15 mm. The ultimate fastener bending angle at the yielded cross section equivalent to this joint slip, which was affected by the fastener’s axial force, was iteratively evaluated in numerical analyses. The introduction of bolt pretensioning largely increased the joint slip resistance at initial loading, but it decreased the ultimate fastener bending angle. This decrease of fastener bending angle resulted in a relatively low stiffness hardening (or secondary stiffness), which is caused by secondary axial forces associated with embedment of steel plates into the wood member. Prediction was verified by the tests of 36 steel-to-timber joints under three different pretension forces and two loading directions relative to the grain. Some of the observed load-carrying capacities of the joints, particularly in loading perpendicular to the grain, however, were not as high as those expected by the numerical analyses considering the given pretension forces.     

Sensitivity study of the finite element model for wood-framed shear walls

A sensitivity study was performed with a nonlinear elastic finite element model for monotonie analyses of wood-framed shear walls. The objective was to provide information about simplifying a model of wood-framed shear walls with no significant loss in accuracy. The simplifications concern features such as slips in joints between frame members, slips in hold-down connections, and bearing between adjacent sheathing panels. The results from analyses of a shear wall with an opening of window shape show that the effect of constraint by the bearing between sheathing panels and slips in frame joints on the overall stiffness of the wall is limited. Thus, there are great possibilities for reducing the calculation time by not taking these phenomena into account, avoiding an excessive number of degrees of freedom and iterations. The influence of the simplifications on the distribution of vertical reaction forces along the wall is more significant. Furthermore, if each simplification is introduced separately, the effect on the overall stiffness is greater. The difference, however, is less than 10%. The failing pattern of the nail connections is also clearly influenced by the simplifications when they are introduced separately. The results from the analyses show that slips in frame joints can be sufficiently represented by those in connection with the opening.     

定向刨花板剪切模量和弹性模量动态测试

【目的】研究定向刨花板(OSB)的各向异性,探讨OSB面内剪切模量动态和静态测试方法,以提供一种快速、简便、重复性好、精度高的动态测试方法测量和分析OSB弹性常数。【方法】应用ANSYS程序计算OSB自由板和悬臂板试件的振形系数,给出振形系数依赖于板长宽比和宽厚比的关系式,通过仿真计算、动态试验和方板静态扭转试验验证其正确性。动态试验测试OSB剪切模量试件从一块整张OSB上下料制作,分为3个方向,即沿整板纵向下料制作的试件(0°或x向)、横向方向下料制作的试件(90°或y向)和沿与纵向呈45°方向下料制作的试件;方板扭转试验测试OSB剪切模量试件沿整板纵向或横向下料制作;动态测试OSB纵向、横向和45°方向弹性模量以及面内剪切模量和45°方向剪切模量。【结果】OSB实测纵向弹性模量是横向弹性模量的2.89倍,45°方向剪切模量小于面内剪切模量。正交各向异性材料方板扭转试验测试剪切模量推算公式需用±45°方向应变测量值的差值进行推算,将其用于OSB,测得的静态剪切模量与动态测试的剪切模量相当吻合。【结论】OSB弹性模量具有方向性,纵向最大,横向最小,45°方向介于二者之间;自由板扭转振形法和悬臂板扭转模态法适用于动态测试OSB面内剪切模量,其正确性得到方板扭转试验验证;0°和90°OSB动态测得的剪切模量几乎相等,可作为OSB面内剪切模量Gxy的估计值;OSB不宜按单向复合材料处理,在理论分析时宜按正交各向异性处理,OSB45°方向的剪切模量G45°相似文献   

基于换算长细比的正交胶合木稳定系数计算方法

正交胶合木(CLT)纵横向层板交叉组坯,纵向层板强度和模量较高,横向层板强度和模量较低,其截面呈强弱相间的条带状结构.当轴心受压构件失稳时,截面剪切变形对CLT稳定承载力的影响不可忽略,故不能采用一般木产品的稳定承载力计算方法.目前我国相关标准中尚无CLT轴心受压构件稳定承载力计算方法.鉴于此,从CLT产品的截面构成特...     

微米木纤维模压制品握钉结合部弹性变形与载荷分布系数的解析

微米木纤维模压制品握钉结合部的承栽能力与其受力时的弹性变形及螺纹牙栽荷分布情况有关,弹性变形由螺纹牙受弯曲、剪切和挤压情况进行分析和求解,进而结合弹性变形和有关几何参数、物理参数间的关系,推导出微米木纤维模压制品握钉结合部载荷分布系数的计算方法,为承载能力计算和结构设计提供理论依据.