Structural Carpentry in Qing Dynasty-A Framework for the Hierarchically Modularized Chinese Timber Structural Design

This article, by using mathematical expressions, offers a scientific framework for understanding how the grading system of Qing′s structural carpentry determines the design and construction in the grand style timber architecture.The Qing′s grand style timber structure, which is ready for prefabrication and assembly, is extremely hierarchical oriented and significantly standardized. The general procedure in designing a grand style timber structure is to start with the grade that defines the basic module (dou kou); next comes with the number of bracket set (cuan), the number of longitudinal bays and the number of purlins which affect its plan and cross section; thirdly choose a roof type that determines its longitudinal section and the facade as well. A series of formulae are conducted to help depict the layout, cross sectional roof curvature and special longitudinal treatments in 4 sloped and 9 spined roofs respectively.

Application of Modern Wood Product Glulam in Timber Frame With Tenon- Mortise Joints and Its Structural Behavior

Tenon-mortise joint is widely used in traditional timber structures around the world.This paper summarizes the results of an experimental study of the structural behavior of tenon-mortise joints made with glulam and CNC technology instead of traditional material and manual work.30 full-scale tenonmortise joints were manufactured and tested under monotonic loading,and the effects of dimension,shape,processing error and adhesive were evaluated.It was found that the round rectangular shaped tenon-mortise joints were comparable with traditional joints in terms of structural performance,but were time and labor saving.The variability of the proposed tenon-mortise joints was lower,which would benefit the design value.Applying adhesive between tenon and mortise increased the average stiffness by 4.3 times and average moment capacity by 27.4%,respectively.The gaps between wood members had little effect on the capacity and stiffness in monotonic bending but may influence the energy dissipation ability in cyclic bending.This study showed the feasibility of combining the traditional joinery method with modern wood products and manufacturing technology,which may promote the application of tenon-mortise joints in modern timber structures.

Tree-Shaped Timber Structural System

This paper lbcuses on the main characteristics of a tree-shaped timber structural system or simply tree-shaped. One of them is the complexity of its steel connections, responsible for the joint of bar elements, compounding a complex structural system, which requires the application of the CYPECAD software version 2007 to solve the calculations problems. Its efficiency was confirmed by a variety of laboratory tests carried out with the whole structure. The tree-shaped is a timber structure that can be used in a large number of destinations, including residences, malls, sheds, hangars, etc.. Originally, it was conceived based on the well-known masterpiece ＂Sagrada Familia＂, whose author was Architect Antoni Gaudi I Cornet （1852-1926） in Barcelona/Spain. It was designed at the end of 19th century and its construction is still not finished. Gaudi inverted the logical order of the gothic concepts, i.e., light weights below and heavy weights above. Based on this concept, he always had in mind the figure of a tree in nature. The tree-shaped follows the same idea, using timber pieces connected by steel plates. Theoretical and numerical analyses have shown its efficiency and lightness for use in timber structures.

Test and Analysis of the Sound Insulation Performance of Four Types of Timber Structure Floors under Jumping Excitation

To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,BGL insulation sound insulation foam board,and EPP polypropylene plastic foam board,are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor.This study uses the transfer function method and transient excitation method to measure the sound insulation,damping ratio,and elastic modulus of materials,as well as the sound insulation of the floor under the jumping excitation method of daily behavior.Through comparative analysis,the results and factors of improving the sound insulation performance of the floor are obtained,according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance.Among them,the overall sound insulation performance of BGL board floor is the highest,followed by EPP board and cork board floor,and ordinary OSB floor is the lowest.Under the jumping excitation method,three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.

Mechanical Characterisation of Densified Hardwood with Regard to Structural Applications

The demand for high-performance,yet eco-friendly materials is increasing on all scales from small applications in the car industry,instrument or furniture manufacturing to greater dimensions like floorings,balcony furnishings and even construction.Wood offers a good choice on all of these scales and can be modified and improved in many different ways.In this study,two common European hardwood species,Beech(Fagus sylvatica L.)and Ash(Fraxinus excelsior L.)were densified in radial direction by thermo-mechanical treatment and the densified product was investigated in an extensive characterisation series to determine all relevant mechanical properties.Compression in the three main directions(longitudinal,tangential,radial)and tension perpendicular to the grain(tangential,radial)were tested and compared to reference specimens with native density.Strength and modulus of elasticity were determined in all tests.In addition,a Life Cycle Assessment was carried out to evaluate the environmental impact associated to the densification process.The experimental investigations showed that strength and stiffness of hardwood in the longitudinal and tangential directions improve significantly by radial densification,whereas some properties in the radial direction decrease.The Life Cycle Assessment showed that artificial wood drying has higher impact than wood densification.Furthermore,the transport distance of the raw material highly influences the environmental impact of the final densified product.The paper then also offers an overview of possible applications in structural timber construction.Densified hardwood is a viable option as local reinforcement,where high compressive or tensile strength is needed.The wood densification process offers an alternative to the use of carbon-intense steel components or hardwoods from tropical forests.

The Use of Glued-in Rods for the Reinfororcement of Timber Structures in European Countries

The woody structural elements represent a significant portion of old works and historical buildings,and the need for retrofit and strengthening them increases.Glued-in rods are an efficient way of providing stiff,high-capacity connections in timber structures.Those flexible joint systems have the advantages of high load transition,appropriate behavior in case of fire,easy application combined with a high level of prefabrication for fast installation.Besides,the aesthetic appearance of the finished joint also plays an important role.Many experiments were undertaken on this subject in Europe,but a common database about the designing instructions of glued-in rods was never encouraged.This paper aims at summarizing the different factors that can affect repairs made with glued-in rods and their influence on said repairs.

Experimental Investigation on the Strength and Ductility Performance of Steel-Timber-Steel Joints with Screw and Steel-Tube Fasteners

This article presents experimental results of steel-timber-steel(STS)joints loaded parallel to grain.Eight groups of specimens were designed,and tensile tests were performed.The fastener types and fastener numbers were considered to evaluate the tensile strengths and ductility performances of the STS joints.The screws with 6 mm diameter and the innovative steel-tubes with 18 mm diameter were adopted as connecting fasteners.The experimental results were discussed in terms of yielding and ultimate strengths,slip stiffness,and ductility factors.The ductility classification and failure mechanisms of each group of specimens were analyzed.It was demonstrated that the STS joint with large diameter steel-tubes showed acceptable ductility,which was close to the ductility of the STS joint with small diameter screws,thanks to the hollow structure of the steel-tube.The theoretical strengths of various failure modes for the joints with small diameter screws or large diameter steel-tubes were calculated and compared with the experimental results.The ductile performance of the STS joint was discussed by comparing the theoretical strengths of various failure modes.The effective number of the STS joint with multifasteners was also analyzed by considering the failure mechanisms in aspects of tensile strength and slip stiffness.

Novel Proposal of Bio-based Sewing Timber Joint:Learning from Diatoms

The twenty-first century is one of the most complex in the history of humanity,mainly due to the ecological crisis it is going through.The construction sector generates about 40%of CO2 emissions into the environment;the foregoing should motivate this sector to seek new alternatives to develop new building practices.Taking these current needs into account,this document classifies and presents a multidisciplinary solution that integrates biology,engineering and architecture to develop a new and innovative lightweight timber structure;it divides with a main structure made of timber and an innovative joint system made of bio-polymers connecting all the panels.Through the study of diatoms,it was able to analyze the bio-morphology of the structure,joints and in particular the geometry since they were the inspiration for the design of this structure that presents an innovative and novel design of structural optimization.Through parametric design and digital fabrication,it was able to create a complex geometry that obtains excellent structural behavior.This research discusses and explores how materials,geometry led to the optimization of a structure and how new structures can arise,thanks to biology new solutions can be obtained that are completely sustainable,being a clear example of how to combat the effects of the climate change and in a precise way it highlights the advantages of the bio-design in the architectural design.

Use of Irregular Wood Components to Design Non-Standard Structures

This project deals with architecture and engineering involved in the process of architectural design.Based on native irregular components,it aims at developing an innovative approach in the conception and rationalization of non-standard structures.Contemporary architecture and its non-classical structures require the design of customized pieces.This process which is highly energy and resources consumptive does not always take into account the inherent material properties.This project develops a way of optimizing,in architectural structures,the use of native wood pieces that are not industrially transformed(e.g.boughs)or of reused pieces of carpentry.As a consequence,the ecological footprint of the structures would be reduced.

高立地指数下杉木生长量及材种结构的立地及密度效应

[目的]探讨立地质量和林分密度对杉木人工林生长量及材种结构的影响,为杉木大径材培育提供理论依据。[方法]以林龄28~36年生的杉木人工林为研究对象,按上、中、下不同坡位以及不同坡向设置63块标准样地,调查林分生长量及林分基本情况,通过相关性分析和回归拟合分析进行数据处理和分析。[结果]当林分密度相近时,立地指数越高,培育相同年限所获得的单株材积、蓄积量和大径材出材率越高;同一立地条件下,在一定的密度范围内林分树高、胸径、单株材积和大径材出材率随密度增加而减小,蓄积量随密度增加而增大;立地指数相同时,密度对胸径生长分化的影响大于树高,立地指数不同时林分密度对树高和胸径生长分化的影响程度也不同。[结论]在立地指数达22及以上的立地条件下培育杉木大径材,可通过3次间伐进行密度控制,林分最终保留密度宜为650~1000株·hm^(−2)。

增设角部阻尼器箍头榫木节点的抗震性能

为了给广府木结构的修复提供理论依据,采用菠萝格木材设计制作了5个箍头榫节点试件。考虑到榫卯构造尺寸的影响,首先进行了未加固无损节点的拟静力试验。然后,采用对原有外观影响较小的雀替型阻尼器对上述节点损坏试件进行加固,以尽可能保留建筑的原始风貌。最后,对加固节点进行拟静力试验,以研究节点的抗震性能变化以及阻尼器的加固效果。结果表明:采用阻尼器加固后的节点试件在加载至破坏时,榫卯处压痕明显,梁外榫外侧劈裂、脱榫现象明显,阻尼器脚部的橡胶与钢板有一定的脱离现象;对节点增设阻尼器能够弥补节点初期损伤导致的受力性能下降,为残损榫卯节点提供较好的后期刚度,提高节点的承载能力和耗能能力;与未加固试件相比,增设阻尼器后,试件的后期刚度、极限承载力、总滞回耗能均有所增加,分别提高18%、19%、20%以上。文中还在已有简化力学模型的基础上,结合OpenSees,提出了一种应用于箍头榫木结构的宏观模型建模方法。采用该方法得到的节点滞回曲线与试验结果吻合良好,可以有效模拟阻尼器加固的箍头榫木节点的滞回耗能特性。

某高层木混合结构抗震分析与性能测试

木混凝土混合结构在多高层木结构建筑中应用广泛,但此类结构的整体抗震性能以及楼盖动力特性有待研究。本文以江苏省康复医院医技楼为例,应用反应谱法与弹性时程分析法分别开展木混合结构的抗震性能分析,并对局部正交胶合木(CLT)楼盖通过原位测试,开展力学性能、动力特性以及人致振动研究。结果表明:结构抗震指标符合规范要求;CLT楼盖荷载位移关系呈双折线,挠度、应力理论计算时,建议板两端按简支考虑;CLT楼盖竖向自振频率均值约15.49 Hz,满足建筑楼盖限值要求,但在单人快走、单人小跑以及多人随机人致振动工况下,楼盖的峰值加速度偏大,应考虑增加现浇建筑面层,改善纯CLT楼盖舒适度不足的问题。可见,木混合结构通过设计可满足抗震要求,但轻质楼盖应注意舒适度构造措施。

木构架古建筑基本周期的分析方法

针对现行规范近似公式存在的不足,结合单层、两层砖围护墙木构架古建筑的构造特征,构建了设有集中质量和连续分布质量的悬臂杆分析模型,以考虑屋顶、楼盖的质量和位置,以及围护墙、木构架的质量和刚度分布规律。依据结构动力学原理,采用等效质量法将分析模型等效为单质点悬臂杆模型,推导了中部集中质量和连续分布质量的等效公式,以及基本自振周期的计算公式。所研制的分析模型较好地反映了古建筑的大屋顶、楼盖及围护墙对结构自振周期的影响,相应的计算公式可以得出结构的横向和纵向基本周期。结合3座典型古建筑的动力特性试验研究,介绍了计算公式的运用方法,并将基本周期的计算值与实测值进行了对比,表明提供的分析方法适用于围护墙在横向、纵向不同布置的木构架古建筑的基本周期分析。

足尺宋式摇摆木构架恢复性拟静力试验研究

摇摆木构架是中国传统木结构的主要承载体系。对足尺单跨木构架模型施加3级竖向荷载进行拟静力试验,观察试验时木构架的位移和变形特点,得到木构架在低周水平循环加载下的滞回曲线和骨架曲线,探究其在不同竖向荷载和低周水平循环加载下的结构特性。加载过程中,木柱刚体转动行为明显、柱架层变形集中,卸载阶段木构架能自主回到初始位置。试验结果表明:各级滞回环狭长且重叠,结构构件呈现出刚体运动的特征,结构整体具有一定位移恢复能力;残余位移介于0.28~2.53 mm间,两组位移恢复系数均大于87.1%,随控制位移的增加未出现显著降低,木构架的位移恢复能力良好;初始刚度在控制位移超过屈服位移后趋于稳定;柱架层变形是斗拱层变形的2.95~86.47倍,层间位移集中系数介于1.22~2.03间,且随控制位移的增加先增后降。

安装偏差对胶合木梁柱植筋节点受弯承载力的影响

胶合木植筋节点在加工和安装时通常会存在些许缺陷和误差,且植筋节点的设计和施工目前尚无标准可循。为了研究含加工缺陷在内的安装偏差对该类节点受弯承载力的影响,明确安装偏差的允许范围,基于理论计算方法初步校核所设计节点的梁端抗弯承载力,然后进行有、无安装偏差节点的有限元分析,并与有安装偏差的试验结果进行对比,运用考虑胶层开裂的有限元分析方法确定安装偏差限值。结果表明:有安装偏差节点的梁端抗弯承载力有所下降;试验中试件的破坏形态主要为植入钢筋屈服、植筋孔洞周围木材破坏及木柱顺纹方向开裂;有限元分析时考虑安装偏差和胶层开裂,则分析结果与试验吻合度较高;相对于通常预留间隙10 mm的节点模型,安装偏差控制在10~25 mm以内时,受弯承载力的降低幅度低于5%。

西南地区穿斗式木结构民居构造特点及震害特征分析——以贵州山区为例

为了深入了解穿斗式木结构的抗震能力,从该结构的建筑构造特点出发对其进行详细介绍。基于对贵州黔西南州、黔南州的乡镇村落的实地调查,对穿斗式木结构的建筑特点和构造特点进行了分类归纳;根据2021年四川泸县6.0级、2022年泸定6.8级地震震中的现场震害调查结果以及自2013以来西南地区6.0级以上典型地震的震害资料,总结了穿斗式木结构房屋的典型震害,包括屋面破坏、围护墙破坏、木构架破坏等,并分析了其震损原因。结果表明:穿斗式木结构独特的榫卯连接形式,使其木构架在地震作用下表现出良好的抗震能力,而填充墙抗震性能相对较差。

CFRP-木结构波纹钢填板螺栓节点力学性能正交试验研究

为了明确异型截面钢填板对节点性能的影响,为木结构异型钢填板螺栓节点提供安全性的设计经验,提出CFRP-木结构波纹钢填板螺栓节点,在正交试验设计条件下开展单轴顺纹拉伸试验研究.试验发现,节点具有多种受力特征,包括木构件剪切破坏、顺纹向张开型断裂(TL断裂)、端部顺纹压溃、CFRP断裂和螺栓弯折等形式;节点在受力过程中没有明显屈服阶段,主要经历线弹性阶段、断裂失效过渡阶段和断裂失效阶段.通过正交参数分析得到不同因素对所提节点主要力学性能的影响程度及规律.结果表明:各因素对极限强度和延性的影响比对弹性刚度的影响显著,且波角和波高为主要影响因素.极限强度与波角负相关且随着波高的增大呈波动变化,延性与波角和波高负相关.

基于无损检测的残损古建筑木结构受力性能研究

硬山式是中国古建筑中最常见的形式。古建筑木结构在历经上百年之后存在不同程度的残损,为了建立更接近实际残损现状的有限元模型,并研究残损对古建筑木结构整体受力性能的影响,选取了北京某四合院民居中的硬山式古建筑木结构为研究对象。通过无损检测,确定了结构的残损类型和残损状况。基于无损检测结果,分别建立了结构的完好和残损有限元模型,对其进行了模态分析、静力计算和地震响应计算。最后,对影响结构频率的各残损参数进行了敏感性分析。研究结果表明:材料的老化、构件和节点的残损降低了结构的刚度和自振频率;在静力作用下,残损结构中构件的最大应力大于完好结构;在地震作用下,残损结构的最大加速度、最大位移和最大位移角均大于完好结构;各残损参数中材料弹性模量对结构频率的影响最大,榫卯拉压刚度的影响最小。

华北地区古建筑木构件开裂类型与特征分析

木构件开裂是木结构古建筑中主要残损类型之一,影响古建筑安全性能。为研究古建筑木构件的开裂类型与特征,通过现场勘查对我国华北地区8处木结构古建筑的关键木构件开裂情况进行检测,获得古建筑木构件开裂残损的类型与形态、数量、尺寸等特征,并与自然干燥的现代材开裂情况进行比较,观察木材裂缝长时间的变化情况。研究结果表明:古建筑木构件开裂率约85%,裂缝按其形态与开裂原因可分为干缩裂缝与受力裂缝,干缩裂缝为主要类型;多数干缩裂缝开裂深度未至髓心,比例为78.16%;木构件干缩开裂特征受其形态影响,自然干燥现代材与古建筑木材开裂特征相同,达到平衡含水率后开裂特征基本不发生变化。

现代木结构抗火研究进展

现代木结构抗火性能研究因其材质的易燃性、火灾预测的复杂性以及影响因素的多样性而极具挑战性。本文以火灾作用下木材热性能为出发点,再到构件和节点分析,进而扩展到结构,对整个现代木结构抗火所涉及的相关研究成果进行较为全面的回顾。主要内容包括:木材着火、热解以及炭化,木构件和节点抗火,木结构抗火。已有研究结果表明:对于火灾作用下木材燃烧机制、构件抗火性能、节点连接性能以及结构火灾性能方面已有较为清晰的认识,也开发了木材着火、热解及炭化预测模型,明确了结构设计与消防安全的基本概念。为满足现代木结构整体火灾安全设计需求,应致力于发展精确的火灾模型、先进的热模型及结构模型,重点关注自然火灾下建筑全过程结构行为;未来尚应在研究内容上聚焦高大型空间木结构火灾温度效应与结构整体受火性能,在研究方法上以性能化火灾安全设计为目标,从而推动现代木结构向高层、大空间及大跨度方向发展。