Influence of Dowel Center Spacing on Chamfered-Joint Components Made byCupressus funebris Wood

The traditional tenon and mortise joint has low processing efficiency and a weak theoretical basis,making the structure easy to deform and damage,reducing the safety,and increasing waste of resources.This study aims to determine the optimum dowel center spacing parameter for chamfered-joint components and the maximum value of the strength of joints loaded into bending strength and tensile strength.In this study,an integrated opti-mization method combining the single-factor test and one-way ANOVA analysis was proposed to study the influ-ence of the dowel center spacing on the bending strength and the tensile strength of chamfered-joint components made by Cupressus funebris wood.The results revealed that the bending strength of chamfered-joint components decreases linearly with the increase of the dowel center spacing.In addition,the tensile strength of chamfered-joint components increases first and then decreases with the increase of the dowel center spacing,showing para-bola change.The relational expression between dowel center spacing,the bending strength,dowel center spacing and the tensile strength were obtained.

Study of the Single Shear Performance of a Joint with a New Beech and Self-Tapping Screw Composite Dowel

A new beech and self-tapping screw composite dowel is proposed and studied,its performance being compared with that of beech dowels and self-tapping screws alone.The single shear performance of components connected by composite dowels was tested.Results show that the dowels are a good choice for components requiring high stiffness.Screws remain a good choice for components requiring excellent seismic performance.Combination group presents similar maximum load stiffness to those of composite dowels,but other ductility parameters are superior for composite dowels.The best connection mode was provided by two composite dowels.Based on connecting two points,structural elements with two composite dowels showed much better load bearing ability than when joined by two beech dowels or by two self-tapping screws separately.The structural element with two composite dowels not only presented better initial stiffness,but also exhibited a better ductility coeffi-cient and less energy consumption.So,the composite dowels can be used for beam column connection,dowel laminated timber,and restoration or enhancement of ancient buildings.

Bending moment resistance of dowel corner joints in case-type furniture under diagonal compression load

We investigated bending moment resistance under diagonal compression load of comer doweled joints with plywood members. Joint members were made of ll-ply hardwood plywood of 19 mm thickness. Dowels were fabricated of Beech and Hornbeam species. Their diameters （6, 8 and 10 mm） and depths of penetration （9, 13 and 17 ram） in joint members were chosen variables in our experiment. By increasing the connector＇s diameter from 6 to 8 mm, the bending moment resistance under diagonal compressive load was increased, while it decreased when the diameter was increased from 8 to 10 mm. The bending moment re- sistance under diagonal compressive load was increased by increasing the dowel＇s depth of penetration. Joints made with dowels of Beech had higher resistance than dowels of Hornbeam. Highest resisting moment （45.18 N.m） was recorded for joints assembled with 8 mm Beech dowels penetrating 17 mm into joint members Lowest resisting moment （13.35 N.m） was recorded for joints assembled with 6 mm Hornbeam dowels and penetrating 9 mm into joint members.

Ion-Beam Surface Modification of Strut Dowel Used in ITER PF Support

In this paper, surface modification of the strut dowel used in ITER PF support is reported. Different ions （nitrogen/titanium） with different doses are implanted into the surface of strut dowel. The result of Auger Electron Spectroscopy （AES） indicates that nitrogen can be implanted more deeply than titanium under the implantation condition of 60 kV accelerating voltage and a dose of 8×10^17/cm2 nitrogen. Surface Micro Hardness （SMH） and wear resistance are improved remarkably. Further SEM observation shows that there are no obvious scratches and damages after wear test.

Numerical simulation of stress behavior of dowel–brick structures in TMSR

As essential elements of the graphite reflector in thorium-based molten salt reactor,dowel–brick structures are used to withstand complex working loads in the reactor core and their failure may lead to serious damage of the graphite reactor core.It is crucial to investigate the stress behavior of dowel–brick structures for safe operation of the graphite reactor.In this study,three groups of finite element analyses and a strain test were carried out to investigate how the geometric parameters of the dowels affect the stress behavior of the dowel–brick structure.The numerical results indicate that the stress behavior of a dowel–brick structure is significantly affected by the diameter,length,and aspect ratio of the dowels.The maximum stress in the lower and upper bricks decreases with an increase in the dowel length.The location of maximum stress on both lower and upper bricks shifts from the root of the socket to the edge of that socket beside the contact region,as the length of the dowel increases.The shift of the maximum stress location occurs earlier for the upper bricks than for the lower bricks.The results of strain tests show good agreement with those of numerical analyses.

Development of a Hybrid Pin Joint with a Compressed Wooden Dowel and Metal Pipe

A newly developed hybrid pin (HP), composed of a compressed wooden dowel inserted into a stainless steel pipe is suggested in this research. This configuration is expected to grant high stiffness by bending performance of the metal pipe and rich ductility through shear deformation of compressed wooden dowel without brittle split of the joint member. Experimental tests were performed in order to verify your assumptions and pursue an optimum design. Double shear test perpendicular to the grain of HP was conducted with parameter of thickness and loading direction for base member for pin’s diameter. Rotational test for mortise and tenon joint inserted with HP was performed in order to evaluate the moment resisting performance. Consequently, the hybrid pin showed satisfactory performance as shear type fastener by virtues of not only relatively high stiffness but also rich ductility originated from the properties of each component, stain less steel pipe and compressed wood.

Dowell压裂防砂有新点子

Dowell公司是著名的斯伦贝谢公司设在美国洛杉矶市的一个专业服务性子公司,主要从事固井、酸化、压裂现场施工,同时也开展一些油藏监测、油层增产技术的研究工作,类似于我们国内油田企业的井下作业公司.2001年3月19-23日,我们一行7人访问了这家公司.Dowell公司有9个固井队、3个压裂队,3个酸化队,有员工150多人,象这样的专业服务公司据说斯伦贝谢有5个.它是其中之一.

Design of Bridge Expansion Joints with Perforated Dowels Under Impact Loading

The expansion joints are expected to have movement capacity, bearing capacity for static and dynamic loading, water-tightness, low noise emission and traffic safety. In particular, the failure due to impact loading is the main reason for the observed damages. The problem of dynamic behavior of the expansion joints is so complex that we shall focus our attention on the impact factor for vehicle load that is governed by traffic impact. In order to overcome this difficulty, the cantilever-toothed aluminum joint (finger joint) is one of the promising joints under impact loading. In this study, from the viewpoint of design methodology, numerical studies for impact behavior were conducted for aluminum alloy expansion joints with perforated dowels. The design impact factor for the expansion joints with the perforated dowels against traffic impact loading was examined by using numerical simulations.

层板销合木的界面滑移与木梁受弯性能

层板销合木(简称销合木)是一种由规格材通过销组合而成的新型结构用木材,与胶合木相比具有加工快捷、成本低且更加绿色环保等优点。为研究销合木梁的弯曲性能,设计了8组木梁的四点弯试验,试验参数包括销的种类(木销和竹销)、销间距(70、100和140 mm)和层板的数量(3、4和6层)。此外,为揭示层积材界面销连接抗剪性能对销合木梁受弯性能的贡献,开展了木销和竹销连接销合木推出试验研究。研究结果表明:与木销连接相比,竹销连接的抗滑移刚度更高且延性更好;销合木梁的受弯性能介于无销接叠合木梁和胶合木梁之间,其组合效率为0.11~0.15;随层板数量的增加,梁截面的增高使销合木梁的抗弯性能显著上升;减小销间距对销合木梁的抗弯承载力与刚度均有一定的提升作用。采用欧洲规范5中的γ法预测销合木梁的抗弯刚度时结果偏大,因此认为对销合木梁的抗弯刚度进行计算时须对销连接的滑移刚度进行折减。

装配式水泥路面夹环连接式传力杆接缝设计及验证

面向可拆卸装配式水泥路面,提出了一种夹环连接式传力杆接缝,在阐述其特征和基本参数的基础上,选取挠度传荷系数和弯沉差作为指标,使用有限元方法分析了下开口槽、传力杆、夹环构件等参数对夹环连接式传力杆接缝传荷能力的影响,同时分析了夹环连接式传力杆接缝的构件及界面应力的变化规律,得到了合理的接缝参数;此外,通过室内足尺试验评价了夹环连接式传力杆接缝的传荷性能。结果表明,提出的夹环连接式传力杆接缝的传荷能力满足要求,具有一定的工程应用价值。

不同构造尺寸下山毛榉木榫旋转焊接SPF基材连接节点的抗剪性能

【目的】为明确构造尺寸对木榫旋转焊接节点抗剪性能的影响,并初步探究节点的群栓组合效应。【方法】采用山毛榉木榫旋转焊接SPF(spruce-pine-fir)基材,通过单剪试验,首先研究了端距、间距和行距对节点抗剪承载性能的影响规律,其次研究了不同直径下的单木榫和双木榫连接节点的抗剪承载性能。【结果】节点的抗剪承载性能主要取决于端距和间距,行距的影响较小。木榫剪切是最主要的节点破坏模式,但当端距≤4d(d为焊接后木榫直径)、间距≤3d时,基材发生了块剪和开裂,承载力大幅降低。随着端距、间距和行距尺寸的增大,节点的峰值荷载先增大后减小。当端距6d、间距5d、行距3d时,木榫旋转焊接节点的抗剪承载性能最优,其峰值荷载分别为3.36、6.68、6.97 kN。木榫旋转焊接连接节点中会存在明显的群栓组合效应,随着木榫直径的增加,节点的群栓组合系数呈现先减小后增大的趋势,当木榫直径≤10 mm时,群栓组合系数大于1.00。【结论】当选用山毛榉木榫旋转焊接SPF基材时,为保证节点的抗剪性能,节点的端距应不小于5d,间距应不小于4d,行距应不小于2d。推荐节点设计时参考端距6d、间距5d、行距3d。木榫旋转焊接节点的群栓组合系数受直径的影响明显,直径范围8~10 mm节点的群栓组合系数更大。

卧式加工中心转台回转夹具定位销连线的数学建模及实例应用研究分析

卧式加工中心转台回转夹具的典型结构是通过在卧式加工中心工作台上配置转台、尾座和夹具体,进而构成摇篮式转台,该种方式可以使加工工序集中化,进一步提高零件的加工质量和加工效率。在基于摇篮式转台回转夹具构成型式分析的基础上,以定位销连线为研究对象,通过讨论定位销连线与转台回转轴线及机床坐标系三者之间平行关系的几种情况,进而建立数学模型,并通过实例的方式解决生产过程中遇到的实际问题。

微型钢管桩内接于灌注桩围护结构计算方法探讨

针对土岩结合二元地层深基坑工程中“吊脚桩”围护结构存在的问题,提出了灌注桩内接微型钢管桩围护结构。考虑微型钢管桩与桩间岩土的“纽结效应”和开挖后桩间岩石与带裂缝混凝土相似性,将该结构等效为上部灌注桩+下部带裂缝的钢筋混凝土无腹筋等效梁阶梯变截面桩(梁)模型,下部等效梁中微型钢管为纵向钢筋,桩间岩石为带裂缝混凝土。用侧向刚度折减来定量表征围护结构截面减少和岩体裂缝对围护结构刚度影响,提出基于侧向刚度折减的弹性支点法来计算围护结构内力,并考虑纵筋销栓作用计算等效梁抗剪承载力。工程实例计算表明,侧向刚度折减系数β由0.85减至0.12,上部灌注桩弯矩增大55.8%,下部等效梁弯矩减少48.7%,上部灌注桩剪力减少13.6%,下部等效梁剪力减少22.0%,桩顶水平位移增加39.5%。开挖至土岩结合面处该结构相对于“吊脚桩”围护结构,桩顶水平位移、竖向沉降没有明显突增,桩顶最终水平位移、竖向沉降仅为“吊脚桩”围护结构的43%、69%。桩顶水平位移监测值为5.5mm,仅为计算包络值的35%,说明刚度折减系数可适当提高。本研究可为土岩结合二元地层深基坑支护提供参考。

振动压入式托架在道面混凝土工程中的应用

振动压入式托架是一种在道面混凝土工程中广泛应用的创新工具,通过振动和压力的结合,可以有效地将混凝土压入道面,从而确保道路表面的均匀性和耐久性。文章以江四路项目道路混凝土试验段施工为研究对象,详细阐述了振动压入式托架的应用要点。首先,全面阐述振动压入式托架的工艺原理,然后围绕该工艺在道面混凝土施工中的应用流程,总结了操作要点,最后通过实践检测,明确振动压入式托架的应用优势。通过分析,进一步了解振动压入式托架在道面混凝土工程中的应用价值,为同类型工程施工应用提供更多参考。

配筋齿槽装配式剪力墙拼缝水平相对滑移研究

装配式剪力墙拼缝界面的水平相对滑移对构件的力学性能有很大影响,以一片普通预制剪力墙为参照,开展新型配筋齿槽装配式剪力墙拼缝水平相对滑移研究.通过对两个装配式剪力墙试件进行低周反复加载试验,分析其裂缝分布情况、拼缝水平相对滑移曲线、荷载-位移曲线和钢筋应变等试验现象和数据,得到配筋齿槽装配式剪力墙拼缝水平相对滑移性能.最后通过分析配筋齿槽装配式剪力墙边缘约束构件区的纵向连接钢筋销键剪切应力与拼缝水平滑移以及竖向位移的关系,对边缘约束构件区的纵向连接钢筋销键剪切应力的影响因素和性能进行了总结.研究结果表明,配筋齿槽拼缝连接形式具有良好的抗剪切能力和抗滑移能力,配筋齿槽装配式剪力墙构件具备更良好的塑性变形能力和耗能能力;纵向连接钢筋销键剪切应力受水平滑移比和竖向位移比的影响,对装配式构件塑性发展、抗震性能以及内力传递造成不良影响.

薄层UHPC中MCL形组合榫连接件力学性能研究

抗剪连接件正常使用阶段的力学性能是影响钢-混组合梁桥结构变形的关键因素。针对薄层超高性能混凝土(Ultra-high Performance Concrete,UHPC)及改进螺旋线(Modified Clothoide,MCL)形组合榫连接件组合形式中组合榫连接件力学性能研究不足的问题,研究UHPC对MCL形组合榫连接件抗剪刚度的影响,探索适用于薄层UHPC中MCL形组合榫连接件的抗剪刚度计算方法。设计并开展薄层普通混凝土(Normal Concrete,NC)以及薄层UHPC中的MCL形组合榫连接件推出试验;建立精细化的ABAQUS有限元数值模型,并通过试件试验结果验证所建立的有限元数值模型的适用性和有效性;基于推出试验数据及有限元数值模拟结果,采用组合榫三弹簧刚度模型,推导出薄层UHPC中MCL形组合榫连接件的抗剪刚度计算公式。研究结果表明:1)UHPC试件中的组合榫连接件抗剪刚度较NC试件有大幅提高;2)MCL形钢榫厚度的增加将使组合榫连接件抗剪刚度显著增大;3)提出的抗剪刚度计算公式能够准确计算薄层UHPC中MCL形组合榫连接件的抗剪刚度。研究成果可为带有MCL形组合榫连接件的UHPC组合结构的推广和应用提供理论支持。

红层泥岩路基上拱无砟轨道传力杆性能研究

在川中红层泥岩地区CRTS Ⅲ型板式无砟轨道会设置传力杆限制沿线路纵向路基上拱变形,但传力杆对上拱地区无砟轨道的影响规律尚不明确。为了探究传力杆的性能,建立无砟轨道-路基上拱-传力杆有限元模型,在路基底部施加余弦型上拱波形位移作为外部条件,同时在底座板接缝处设置传力杆。将传力杆布置方式、直径、间距作为影响因子,设置无传力杆对照组进行对比分析。针对红层泥岩路基上拱,研究结果表明:1)设置传力杆与不设置传力杆复合板与底座板最大离缝分别为1.14 mm和4.82 mm,底座板与路基最大离缝分别为3.16 mm和5.29 mm,表明传力杆的设置能较好降低最大层间离缝,尤其是复合板与底座板轨道结构之间的层间离缝。2)传力杆布置方式1(中性层均匀布置1排)下底座板板端应力为1.13 MPa,为传力杆布置方式2(上下2层、交错布置)下底座板板端应力2.98 MPa的37.9%,底座板板端应力较小,应力分布均匀。3)复合板与底座板最大离缝、底座板与路基最大离缝及底座板应力在传力杆直径为30 mm时分别为0.82 mm、1.66 mm、3.16 MPa,达到相对较小值。4)随着传力杆布置间距减小、传力杆数目增多,轨道结构应力几乎没有变化,轨道结构竖向位移明显减小,说明传力杆布置间距减小对轨道结构应力的影响可以忽略不计,但对轨道结构位移的限制效果越好。

暗销直榫节点受弯性能试验与参数化研究

传统民居木结构建筑中的节点主要采用直榫连接,暗销直榫节点是其常用形式。为了研究暗销直榫节点的受弯性能,对圆形暗销直榫节点进行单调加载试验,得到弯矩-转角、拔榫量-转角、弯矩-应变关系曲线及破坏模式,试件失效主要以节点榫头破坏为主。运用有限元软件对试件进行了数值模拟,并与试验结果对比验证。基于验证后的数值模拟方法,分析了暗销截面形式、枋高、枋宽、摩擦系数对暗销直榫节点受弯性能的影响。结果表明:圆形截面会转动,应力分布相对均匀,而方形截面会扭曲,棱角处会出现应力集中。增大枋高、枋宽及摩擦系数均会提高节点的转动刚度和抗弯承载力。

层板销接木性能研究进展

层板销接木(DLT)是仅由木销和层板组成的一种无胶无钉、近似全实木的工程木产品,可用于制作梁、墙体和楼板,具有用材经济、绿色低碳和预制化程度高等特点.从构造和分类两方面对DLT进行简要概述,系统梳理了近些年DLT在木销、木销节点及构件方面的性能研究成果,包括木销-层板销槽承压性能、木销节点抗剪性能、DLT木梁抗弯性能及DLT板振动特性等.在此基础上,介绍了DLT在性能研究中存在的不足,并提出了DLT研究亟需解决的关键问题.