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采用自攻螺钉对胶合木梁侧进行横纹增强,并开展4组(含未增强组)胶合木梁侧横纹承压试验。结果表明,3种增强方式对胶合木梁侧的横纹承压性能均有不同程度提高,单侧通长贯入螺钉组试件最终发生了局部屈曲破坏,而其他组螺钉变形不明显;相比于未增强组试件,单侧通长贯入螺钉、双面贯入螺钉和双侧斜交螺钉组试件的横纹承压荷载分别提高了25.9%、34.5%和44.8%;单侧通长贯入螺钉组试件表现出了最高的等效横纹承压弹性模量,为333.6N/mm2,而其他两种增强方式的等效横纹承压弹性模量略低于未增强组试件。荷载-应变关系表明,自攻螺钉的引入能有效改善承压面下木材应变的分布。采用欧洲标准EN 408与ISO 13910标准获得的横纹承压强度较为接近,而按照《木结构试验方法标准》(GB/T 50329—2012)获得的结果偏于保守;有限元模型总体上能有效预测自攻螺钉增强后的胶合木梁侧横纹承压性能。 相似文献
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为研究带裂纹钢框架梁柱节点在地震过程中的抗震性能,设计制造了5个梁柱节点局部试件进行拉卸循环加载试验,研究初始裂纹缺陷位置对局部试件力学性能的影响.试验结果表明:带初始裂纹缺陷的加强型节点局部试件的承载力和延性性能均有所降低;初始裂纹缺陷位置不同会对试件产生不同程度的影响,缺陷位于加强板端部角焊缝中间时所造成的影响更为突出. 相似文献
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为研究内嵌CFRP筋加固木梁在长期荷载作用下的受力性能,设计并制作了3个木梁试件,开展了6年的持荷试验,持续测试了木梁的跨中挠度变化和纯弯段木材的蠕变发展,并记录了环境温湿度变化对木材中和轴位置应变增量的影响。结果表明,对比木梁和加固木梁的初始缺陷均对其长期性能有重要影响,跨中不存在初始缺陷的加固木梁的挠度小于未加固对比木梁;而跨中存在明显初始缺陷的加固木梁的挠度高于未加固对比木梁,并在跨中木节周围出现了明显裂缝。根据试验结果对经典蠕变模型中的材料参数进行了拟合,拟合后的模型预测的木梁跨中挠度与试验结果比较吻合。 相似文献
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对36个Q460高强钢试件进行单调拉伸与循环拉伸下的力学性能试验,探讨开孔数量、开孔位置和加载制度对Q460高强钢试件破坏特征、极限抗拉强度、应力循环特征和耗能能力的影响规律.结果表明:孔洞对Q460高强钢试件的力学性能具有显著影响;开孔试件在孔洞周围出现明显的应力集中现象;未开孔试件的应力-应变曲线更为饱满,且未开孔试件的耗能能力和断后伸长率远大于开孔试件;相较于沿试件长轴方向的孔洞,沿试件短轴方向的孔洞对试件力学性能的影响更为显著;对于相同开孔数量和开孔位置的试件,其耗能能力随加载应变幅值增量的增大而减小. 相似文献
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传统地仗层既可作为传统木结构建筑油漆工艺的基层,又能有效防止木构件腐朽和虫蛀,但地仗处理对木构件防火能力影响的研究还很少.通过4组12根木梁受火后力学性能的对比试验,研究了一麻五灰传统地仗工艺对三面受火木梁耐火性能的影响,分析了是否采用一麻五灰、受火时间等参数对木梁极限承载力、初始刚度和炭化速度变化规律的影响.结果 表明,一麻五灰传统地仗处理试件在相同受火时间后的极限承载力和初始刚度均明显高于未做表面处理的试件;一麻五灰传统地仗处理和表面无处理木梁试件受火后剩余截面仍基本符合平截面假定;一麻五灰传统地仗处理木梁的炭化速度显著小于未做表面处理的试件,一麻五灰传统地仗处理能有效推迟木梁开始炭化的时间,延缓木梁受火后力学性能的劣化速度. 相似文献
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为了研究双肢开孔冷弯薄壁型钢拼合箱形截面立柱的轴向受力性能,采用有限元方法对拼合箱形截面立柱长细比、腹板宽度、试件厚度、开洞情况及孔洞间距等参数进行了非线性分析,并将有限元结果与《冷弯薄壁型钢结构技术规范》(GB 50018—2002)"有效宽度法"计算未开孔试件承载力进行对比。综合考虑腹板孔洞影响,对构件轴压承载力进行折减,提出了适合双肢开孔冷弯薄壁型钢拼合箱形截面开孔试件轴压承载力计算的建议修正公式。分析结果表明:试件轴压承载力会随长细比增大及腹板孔洞的出现而减小;腹板位置处开孔洞会对试件极限承载力和破坏位置产生较大影响;开洞间距的大小不能明显改变多孔试件的极限承载力,也不会改变多孔试件的屈曲失效模式。 相似文献
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共选择了186根尺寸为38 mm×89 mm×3 658 mm的加拿大针叶树商品材云杉-松-冷杉(SPF)的建筑结构材作为试验材料,探讨采用一种横向振动技术来评估这些规格材的静态抗弯、抗拉和抗压强度的可行性.所有试材均根据ASTM D4761的三分点加载方法测量其抗弯弹性模量,然后按照抗弯弹性模量再将它们均匀分成3组.3组试材在采用横向振动方法获得它们的动态弹性模量Etv后,再分别进行抗弯弹性模量和抗弯强度(ASTM D4761)、抗拉强度(ASTM D4761)和抗压强度(ASTMD198)的测试.试验数据表明,采用横向振动方法得到的动态弹性模量Etv与抗弯弹性模量的相关系数(R2)为0.766,与抗压强度的相关系数R2为0.651,均在0.01水平上呈显著相关.但是,动态弹性模量Etv与抗拉强度之间没有显著的线性关系.本研究结果说明,横向振动方法能够用于预测建筑结构材的静态抗弯、抗压强度. 相似文献
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《Construction and Building Materials》2007,21(8):1647-1655
The aim of this study was to investigate the impacts of impregnation with Imersol-aqua on the modulus of elasticity in bending (MOE) of some laminated wood materials. For this aim, oriental beech (Fagus orientalis Lipsky), oak (Quercus petrea Liebl.), Scotch pine (Pinus sylvestris Lipsky), oriental spruce (Picea orientalis Lipsky) and Uludağ fir (Abies bornmülleriana Lipsky) wood materials impregnated with Imersol-aqua according to ASTM D 1413-99 and producers’ definition. Laminated wood samples were produced from impregnated wood materials according to TS EN 386 in the five ply form (4 mm each) from oriental beech, oak, Scotch pine, Uludağ fir and oriental spruce wood by using Desmodur-VTKA adhesive. The MOE values were measured according to TS EN 408. Consequently, the MOE of impregnated + laminated (I + LW) softwoods, pine, spruce and fir increased, respectively by 8.07%, 2.62% and 2.45% whereas the MOE of laminated + laminated hardwoods, beech and oak decreased, respectively by 5.06% and 4.37% with respect to laminated control samples (LW). Considering the interaction of wood type and process, the MOE was obtained from laminated oriental beech, whereas the lowest was found for impregnated Uludağ fir. In consequence, in the massive construction and furniture elements that the MOE after the impregnation and lamination (I + LW) is of great concern, oriental beech and Scotch pine materials could be recommended. 相似文献
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《Construction and Building Materials》2007,21(9):1879-1885
Wood polymer composite (WPC) was obtained by vinyl monomers such as styrene (ST), methylmethacrylate (MMA), and their mixture (50:50; volume:volume) of treated sapwood of Scots pine (Pinus sylvestris L.). Boric acid (BA) and borax (BX) mixture was impregnated into wood at 1% concentration prior to monomer treatment. Wood polymer composite with and without BA and BX mixture pretreatment was evaluated in terms of some physical, biological, mechanical, and fire properties.Vinyl monomers considerably improved physical properties of wood such as increased antiswelling efficiency (ASE), specific gravity (SG), and reduced water absorption (WA) levels of wood. Modulus of elasticity (MOE) and modulus of rupture (MOR) were also higher than that of untreated control specimens. The treated wood proved to be resistant against decay fungi, Tyromycetes palustris and Coriolus versicolor. Boric acid and borax mixture pretreatment imparted WPC total resistance against both decay fungi. Although, ASE, MOE, and MOR levels of WPC pretreated with BA and BX mixture were reduced in some extent, it improved fire resistance of wood. 相似文献
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Behbood Mohebby Maryam Gorbani-Kokandeh Mojtaba Soltani 《Construction and Building Materials》2009,23(9):3103-3106
Reasons of the strength loss of the acetylated wood based composites were still under question. This research was considered to study springback in the acetylated particleboard and the medium density fibreboard. Chips and fibres were acetylated by using the acetic anhydride to gain different percentages of the weights (WPG). The boards were made based on the target thicknesses. Thickness of the boards as well as the modulus of elasticity (MOE) and the modulus of rupture (MOR) were determined after conditioning based on three point static bending test.Results showed that the moisture content and the thickness swelling of the boards were reduced as the WPG was increased. However, increase of the springback and reduction of the MOE and the MOR were revealed as the WPG increased in the test boards after condition. It was also revealed that the springback was correlated with the weight gain and increased as the WPG was raised in the test boards. Reduction of the MOE and the MOR was also correlated with the springback in the test boards. 相似文献
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地震波CT技术探测煤层上覆岩层破坏规律 总被引:15,自引:6,他引:15
利用地震波CT技术进行煤层上覆岩层破坏规律探测,从测试原理、工作方法及资料解释等方面阐述了孔一巷间地震波CT探测技术,并通过煤矿上提工作面观测实例,进一步说明该方法进行上覆岩层破坏观测及判定的准确性和可行性。研究表明,与传统方法相比,地震波CT技术观测成果具动态性,且经济、直观,达到高精度和高分辨的精细要求,其结果实用可靠。 相似文献
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兴安落叶松结构用规格材强度特征值的研究 总被引:1,自引:0,他引:1
以截面尺寸为40mm×65mm,40mm×90mm和40mm×140mm国产兴安落叶松结构用规格材为研究对象,参照GB 50005—2003《木结构设计规范》的目测分等规则,将其分为Ⅰc,Ⅱc,Ⅲc和Ⅳc这4个等级.根据ASTM D4761-02a对其进行抗弯弹性模量、抗弯强度、顺纹抗拉强度和顺纹抗压强度测试.参照ASTM D2915-03,利用非参数法估计得到国产兴安落叶松结构用规格材的不同强度特征值,结果表明,其强度特征值高于进口云杉松冷杉(S-P-F)结构用规格材.通过足尺测试获得结构用规格材强度特征值,改变了GB 50005—2003现有强度特征值由无疵小试样推导而得的历史,同时为获得其他国内树种结构用规格材强度特征值提供了科学方法. 相似文献
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Among the geotechnical in situ tests,the dynamic penetration test(DPT)is commonly used around the world.However,DPT remains a rough technique and provides only one failure parameter:blow count or cone resistance.This paper presents an improvement of the dynamic cone penetration test(DCPT)for soil characterisation based on the wave equation theory.Implemented on an instrumented lightweight dynamic penetrometer driving with variable energy,the main process of the test involves the separation and reconstruction of the waves propagating in the rods after each blow and provides a dynamic cone load-penetration(DCLT)curve.An analytical methodology is used to analyse this curve and to estimate additional strength and deformation parameters of the soil:dynamic and pseudo-static cone resistances,deformation modulus and wave velocity.Tests carried out in the laboratory on different specimens(wood,concrete,sand and clay)in an experimental sand pit and in the field demonstrated that the resulting DCLT curve is reproducible,sensitive and reliable to the test conditions(rod length,driving energy,etc.)as well as to the soil properties(nature,density,etc.).Obtained results also showed that the method based on shock polar analysis makes it possible to evaluate mechanical impedance and wave velocity of soils,as demonstrated by the comparisons with cone penetration test(CPT)and shear wave velocity measurements made in the field.This technique improves the method and interpretation of DPT and provides reliable data for shallow foundation design. 相似文献
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从一维波动方程的有限差分解,导出了变截面的应力波传播公式和桩身完整性的表达式;结合工程实例,采用高应变动力试验分析了预应力高强混凝土管桩(以下简称PHC桩)的桩身断裂、接桩缺陷和桩尖破碎等缺陷以及桩身多缺陷情况;讨论了高应变动力试验结果的可靠性. 相似文献
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In this study, effects of specific gravity (SG), shelling ratio, wood species, and pressure on the formaldehyde content, physical (SG and thickness swelling (TS)), and mechanical properties (modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) strength) of particleboard were examined. The best manufacturing parameters were determined for E1 grade particleboard manufacturing from urea formaldehyde (UF) adhesive. Based on the findings of this study, increasing of SG, shelling ratio, and pressure increased the formaldehyde content. Particleboard made from particles consisting higher amount of beech particles had lower formaldehyde content than that of panel from particles consisting higher amount of pine particles. 相似文献