马口铁加固古建筑榫卯节点抗震试验

为保护古建筑,采用试验方法,研究了马口铁加固古建筑榫卯节点后对节点抗震性能的影响.基于故宫太和殿三次间结构原型,制作了1:8缩尺比例的木结构空间框架模型,并考虑梁柱连接为燕尾榫形式,进行了低周反复加载试验,其中未加固构架和马口铁加固构架试验各做了3组.基于试验相关数据,获得了节点的弯矩-转角滞回曲线和骨架曲线,并对比分析了节点加固前后的耗能能力,刚度退化和延性等抗震指标.结果表明:马口铁加固榫卯节点后,虽然节点耗能能力略有下降,但节点拔榫量减小,抗弯承载力提高,刚度退化不明显,且节点仍具有较好的变形能力.因此,马口铁具有较好的加固效果.     

不同方法加固古建筑榫卯构架抗震试验

为保护古建筑,采用试验方法,研究了不同方法加固榫卯节点后木构架的抗震性能。基于故宫太和殿某开间梁柱节点的具体尺寸,制作了1:8比例的4梁4柱木结构空间框架模型,其中梁和柱考虑为燕尾榫形式连接。采用人工加载方式,进行了低周反复加载试验,研究了马口铁、CFRP布和钢构件加固榫卯节点后对木构架抗震性能的影响。基于试验结果,获得了加固前后构架的力-侧移滞回曲线和骨架曲线,分析了构架耗能能力、刚度退化规律及变形能力,对不同方法加固木构架的抗震效果进行了对比,对其工程应用提出了建议。     

南方地区古建筑木结构的整体性残损点指标研究

古建筑木结构的残损点指标是对古建筑木结构进行结构安全评估和加固修缮设计的重要指标,目前主要依据1992年制定的《古建筑木结构维护与加固技术规范》(GB 50165—92)中的规定,为了对该规范中的构架整体性残损点指标进行验证和补充,本研究通过对南方地区传统的穿斗木构体系和抬梁木构体系的典型榫卯节点和构架的试验研究,得出两种木构体系结构的整体性关键残损点指标,并与GB 50165—92规范进行比较分析。结果表明:规范规定的抬梁式木构架和穿斗式木构架的局部倾斜残损点比试验结果小,规范值偏于安全。规范中规定的抬梁式木构架梁柱榫卯连接残损点略小于试验结果,规范值偏于安全;而规范中规定的穿斗式木构架梁柱榫卯连接残损点对于燕尾榫穿斗木构而言是安全的,但对于透榫穿斗木构而言,则是不安全的。     

南京长江大桥桥头堡抗震加固受力性能研究

为研究南京长江大桥桥头堡填充墙加固对结构抗震性能的影响,提出考虑较高填充墙开裂的双斜撑模型,用于罕遇地震工况下桥头堡的抗震性能计算,同时提出考虑填充墙加固后刚度增强效应的建模方法。利用SAP2000建立了加固前后用于多遇地震工况、设防地震工况及罕遇地震工况的分析模型,并选取了桥头堡在1974年经历的实际地震激励时程及El-Centro地震激励时程作为激励进行了加固前后结构的抗震性能分析比较。研究发现,填充墙加固后桥头堡的抗震性能有了明显提升,其位移响应峰值约下降8%~23%,层间位移角响应峰值约下降12%~22%,而且桥头堡结构在设防地震情况下2个方向的层间位移角均满足了规范要求。另外,在罕遇地震工况下,未加固的填充墙开裂会使结构的扭转刚度下降,而填充墙加固可有效提升结构的扭转刚度,降低桥头堡在地震时发生扭转振动的概率。这2种地震荷载激励的分析结果差异约在3%~21%不等,且响应峰值出现的位置也有一些不同,故对桥头堡进行抗震时程分析时建议选取多条地震波输入综合分析。研究成果可为同类型的钢筋混凝土建筑遗产的抗震加固提供借鉴和参考。     

宁波保国寺大殿北倾原因浅析

宁波保国寺是浙东现存最古老的宋代木结构建筑,自清乾隆时期起,大殿结构发生北倾,后对4号转角檐柱进行修缮并加固至今,通过跟踪测试没有发现新的倾斜趋势。然而,探讨大殿曾经北倾原因以及经修缮后现今大殿的可靠性无疑仍是必要的。古木结构的特点是梁柱的榫卯连接具有半刚性性质。采用有限单元法对大殿结构进行力学分析时,榫卯连接可采用空间二节点虚拟弹簧元进行模拟,单元刚度矩阵中相应的刚度特性系数可由接触有限单元法近似求得。这样,大殿结构可离散为杆、梁、壳、体元和上述虚拟弹簧元等的组合,在屋面荷载、雪荷载和风荷载作用下采用有限元法可求得各节点的位移和相应应力。通过计算表明,不计4号柱时产生的向北位移比考虑该柱参加受力时要大得多,可见北倾原因确系4号柱年久失效而引起。计算结果也表明,现今大殿结构由受力来看是安全的。同时预示了可能出现的最危险部位。保国寺大殿结构的力学分析结果,为物保护工作提供了科学依据。     

故宫太和殿结构现状数值模拟研究

为保护故宫太和殿,采用数值模拟方法,研究了太和殿的结构现状特征。采用ANSYS有限元程序,考虑榫卯节点、斗拱连接等构造,建立了太和殿有限元模型。分别对模型进行自重作用、风荷载作用下的静力分析及8度常遇地震作用下的时程响应分析,获得了太和殿在不同荷载作用下的内力及变形分布特征,评价了太和殿的结构安全现状。结果表明:重力及风荷载作用下,太和殿结构的内力、变形均在容许范围内;地震作用下,结构保持稳定状态,且榫卯节点及斗拱构造有利于减震。因此,太和殿结构现状是安全的。     

明清古建筑木结构典型抗震构造问题研究

为保护古建筑,采用分类统计方法,研究了我国明清古建筑木结构的典型抗震构造问题。基于大量工程现场勘查结果,对古建筑木结构的典型抗震构造问题进行了归纳汇总,分析了原因,提出了加固建议;基于典型算例,对古建筑木结构加固方法进行了深入论证。结果表明:我国古建筑木结构的柱子、斗棋、榫卯节点、梁架、屋顶等各部位都容易产生开裂、糟朽、变形、拔榫等抗震构造问题并影响结构的抗震性能,而这些问题的产生原因主要与木结构的构造特征、木材材料性质及施工保养等因素有关;对这些抗震构造问题及时采取合理有效的加固措施,可减轻或避免结构产生的震害。     

明代石拱桥永昌桥的加固修缮技术研究

为明晰明代石拱桥的结构性能,并提出适宜的加固修缮方法,以典型的明代石拱桥永昌桥为例进行研究。首先对其进行精确测绘,获得其准确可靠的几何信息;然后对其建筑形制、构造工艺及残损状况进行研究,为结构性能分析提供依据;接着利用ANSYS软件建立永昌桥主体结构的有限元模型,进行包括荷载影响分析、重要度分析和裂缝分析的结构性能研究;最后基于现状分析和结构性能研究,通过对比拱背套钢筋混凝土拱加固法和拱背粘贴碳纤维布加固法对石拱桥的结构性能的影响,提出了明代石拱桥永昌桥的加固修缮方法。研究成果可为同类型石拱桥的加固修缮提供参考。     

故宫古建筑结构可靠性问题研究

为保护故宫古建筑,采用归类汇总与理论分析相结合的方法,研究了故宫古建筑木结构的典型残损问题。基于大量现场勘查及理论分析结果,对故宫古建筑存在的典型可靠性问题进行了分类汇总,分析了产生这些问题的原因,提出了可行性加固建议。通过典型算例,对古建筑木结构加固方法进行了深入论证。结果表明:故宫古建筑木结构的柱子、斗栱、榫卯节点、梁架、屋顶、墙体等各部位都容易产生开裂、糟朽、变形、拔榫等可靠性问题并影响结构整体的稳定性能,而这些问题的产生原因主要与木结构的构造特征、木材材料性质及施工保养等因素有关;针对不同的可靠性问题,采取合理有效的加固方法,可提高古建筑结构整体的稳定性能。     

基于脱榫状态的古建筑木结构燕尾榫节点试验研究

为对古建筑木构架的安全性评价提供依据,通过对脱榫状态下的燕尾榫进行静力试验研究,分析得到残损状态下的木构架力学性能。按照预加载-加载的试验方案对构架进行试验。通过对试验数据的分析,得出了节点主要破坏形式、脱榫量对构架破坏的影响、极限承载力及极限荷载的取值方法并结合理论分析试验数据。     

Experimental Investigation on the Seismic Behavior of the Semi-Rigid One-Way Straight Mortise-Tenon Joint of a Historical Timber Building

ABSTRACT

This article aims to disclose that the deformation and damages of the one-way straight mortise-tenon (OWSMT) joint, the key force transmission connection of traditional wood buildings, lead to a significant reduction in structural safety of ancient timber structure. For this purpose, the damage of mortise joint in practical engineering wassimulated by controlling the gap and width between mortise and tenon. A total of 23 groups of scaled 1:2 OWSMT joint specimens were fabricated and tested subjected to cyclic loadings, and the hysteretic curves of OWSMT joint with different damage degrees were obtained. Through skeleton curves, stiffness degradation curves, and equivalent viscous damping curves of the OWSMT joint, the seismic performance of damaged wood joints was quantitatively analyzed. The results show that, with the increase in the gap between the tenon and the mortise, the slip between them became increasingly obvious, the fullness and peak of the hysteresis curve gradually decreased, the gradient of the skeleton curve also dropped, and both the stiffness degradation curve and the equivalent viscous damping curve are gradually reduced. The research findings shed new light on the seismic assessment of aging timber buildings.     

Rotational behavior of degraded traditional mortise-tenon joints: experimental tests and hysteretic model

This article presents the results of an experimental study on the rotational behavior of degraded Chinese traditional mortise-tenon joints with different degradation types and different degradation degrees. Six joint specimens degraded through artificially simulated method, were tested by reversed cyclic loading, from which the moment-rotation curves were obtained. The results indicated that the rotational behavior of these joints is semi-rigid, the hysteretic curve shapes of degraded joints are same to that of joint without degradation. The maximum moment, yield moment, and initial rotational stiffness of degraded joints decreases as the degraded degree increases, whose empirical degradation relationships were obtained based on the test data. A hysteretic model for degraded traditional mortise tenon joints was proposed. Experimental results were used to validate the proposed hysteretic model. Good agreement between predictions and tests was observed.     

Experimental Study on Seismic Performance of Through-Tenon Joints with Looseness in Ancient Timber Structures

ABSTRACT

In order to study the influence of looseness on seismic performance of through-tenon joints, six through-tenon joints specimens in 1:3.2 scale, including one tight-fitted joint and five loose joints, were fabricated according to the Engineering Fabrication Methods of Qing dynasty. The failure modes, mechanical behaviors such as the hysteresis and envelope curves, strength and stiffness degradations, energy dissipation, and deformation of the specimens under low cyclic reversed loading tests were analyzed. Results show that the failure modes of theses joints under positive and negative loadings are bending damage on the big tenon head and tearing damage on the variable cross-section, respectively. The hysteresis curves of joints appear to be anti-Z shape and present typical pinching effect. The greater the degree of looseness is, the more obvious the slippage is. The bending moment, stiffness and energy dissipation of loose joints are lower than those of the tight-fitted joint under the same rotation angle, and the increase in the loose degree cause them to gradually decrease. Meanwhile, the behavior of the through-tenon joints is further simulated by the nonlinear finite element analysis program, and the test results agree well with the numerical analysis results.     

Flexural Performance of Small Fir and Pine Timber Beams Strengthened With Near-Surface Mounted Carbon-Fiber-Reinforced Polymer (NSM CFRP) Plates and Rods

In order to study the flexural performance of fir and pine timber beams strengthened with near-surface mounted carbon-fiber-reinforced polymer (CFRP) plates and rods, bending tests on 20 specimens are carried out, including four unstrengthened specimens, four specimens strengthened with CFRP plate with the dimension of 1.4 mm × 30 mm, four specimens strengthened with CFRP plate with the dimension of 2.8 mm × 30 mm, four specimens strengthened with one Φ6 mm CFRP rod, and four specimens strengthened with one Φ8 mm CFRP rod. The proportions of fir specimens and pine specimens are 50% and 50%. The results show that compared with the unstrengthened specimens, there is an improvement in flexural capacity and stiffness of the specimens strengthened with near-surface mounted CFRP plates and rods respectively. Finally, the calculation formulas of the flexural capacity of fir and pine timber beams strengthened with near-surface mounted CFRP plates and rods are presented.     

The Byzantine‐Period Dor 2006 Shipwreck,Israel: preliminary hull construction report

The Dor 2006 shipwreck was discovered in 2006, 100 m offshore, 800 m south of Dor (Tantura) lagoon. The wooden hull remains included sections of large frames, stringers and ceiling planks, a large number of strakes and wales, some with unpegged mortise‐and‐tenon joints. Among the finds were ceramic sherds, wooden objects, matting, ropes, food remains, and coins. The shipwreck was dated to between the second half of the 6th and the first quarter of the 7th centuries AD. The wooden components of the hull indicate a large ship compared with other shipwrecks of the period, and the largest ever excavated in the Dor area.     

The 5th‐Century BC Shipwreck at Tektaş Burnu,Turkey: evidence for the ship's hull from nail concretions

The Tekta? Burnu ship (440–425 BC) sank along a rough and desolate stretch of the Turkish Aegean coast. Archaeological excavation of the shipwreck site by the Institute of Nautical Archaeology at Texas A&M University resulted in the retrieval of hundreds of small fragments from the ship's wooden hull and its metal fasteners. Recent study of this artefact assemblage suggests that the coastal trader was built with pine planks and made‐frames, and assembled by a shell‐based construction method. Fasteners include pegged mortise‐and‐tenon joints and double‐clenched copper nails, and the ship may have had laced extremities consistent with other contemporaneous shipwrecks.     

New Data on Egyptian Construction Methods in the Khufu I Vessel (c.2566 BC) from the Paul Lipke Collection

A review of the Lipke collection raises new questions concerning Egyptian boatbuilding methods for the Khufu I vessel, including the shaping of planking, the purpose, fitting, and spacing of cross‐grain mortise‐and‐tenon joints and the crafting and securing of hook‐scarfs in girders. New data supports the author's contention that the construction of this vessel was abruptly terminated, but contradicts his suggestion that the central girder had no hook‐scarf—it does, but it is unique. Furthermore, detailed plans show how the hood‐ends, sleeves, and papyriform decorations were crafted and joined. A planking‐plan with scale does not always agree with published data. © 2010 The Author     

汶川地震导致的壁画文物震害研究——以广元市觉苑寺大雄宝殿壁画为例

为保护壁画文物,以四川省广元市剑阁县大雄宝殿为例,对汶川地震作用下殿内壁画的震害进行了研究.根据震后勘查结果,讨论了大雄宝殿壁画的典型震害症状,分析了古建筑侧脚构造对壁画抗震的有利影响.根据大雄宝殿壁画加固工艺作法及古建筑榫卯连接特点,建立了大雄宗殿的震前有限元模型.为研究汶川地震作用下壁画的震害特征,首先对其进行了模态分析,然后将模拟汶川地震波进行调幅,然后作用于大雄宝殿进行地震反应分析.通过采用时程分析法,获得了地震作用下不同时刻壁画整体的内力与变形响应峰值,并获得了典型节点的地震响应曲线.结果表明:大雄宝殿壁画开裂与空鼓的主要原因是面层与墙体粘结不牢导致的受拉破坏;地震作用下壁画保持稳定的振动状态;为提高壁画的抗震性能,壁画木框与外墙板间应加强连接,并在空隙处填塞隔震材料,同时应加强壁画本身保养工作.