【摘要】：木材作為一種建筑材料曾普遍運(yùn)用于歷史傳統(tǒng)建筑中,現(xiàn)存的古建聚落絕大部分是木結(jié)構(gòu)建筑。然而,木材因其獨(dú)特的各向異性特征,使得木結(jié)構(gòu)受溫濕度的影響非常明顯,主要表現(xiàn)為產(chǎn)生順紋干縮裂縫,而歷史建筑中的木構(gòu)件歷經(jīng)歲月,干縮開裂現(xiàn)象更是嚴(yán)重。因此,在評(píng)定歷史建筑聚落殘存木結(jié)構(gòu)的安全性時(shí)應(yīng)該考慮干縮裂縫對(duì)木構(gòu)件承載力的影響。為了確定縱向干縮裂縫的存在對(duì)木構(gòu)件受力性能的影響,本文通過設(shè)置人工扇形縫模擬自然干縮裂縫的方法,設(shè)計(jì)了4組共8根帶有不同裂縫尺寸的圓形截面杉木長柱的軸心受壓試驗(yàn)和4組共8根帶有不同裂縫尺寸的方形截面杉木長梁的三分點(diǎn)抗彎試驗(yàn),研究縱向裂縫對(duì)木柱軸壓承載力和木梁抗彎承載力的影響。試驗(yàn)結(jié)果表明：在構(gòu)件尺寸、試驗(yàn)條件相同的情況下,設(shè)有縱向扇形縫的試驗(yàn)柱軸壓極限承載力較未開縫參照柱軸壓極限承載力有所降低,且裂縫深度較淺時(shí)承載力降低程度可忽略不計(jì),隨著裂縫深度的增加木柱軸壓極限承載力下降程度會(huì)更加明顯,當(dāng)縱向干裂木柱的裂縫深度達(dá)到木柱柱徑64%左右時(shí)構(gòu)件軸壓極限承載力較完整木柱構(gòu)件下降程度可達(dá)20%；設(shè)有縱向扇形縫的試驗(yàn)?zāi)玖嚎箯潣O限承載力較未開縫參照木梁抗彎極限承載力有所降低,且裂縫深度較淺時(shí)承載力降低程度可忽略不計(jì),隨著裂縫深度的增加木梁抗彎極限承載力下降程度會(huì)更加明顯,縱向干縮裂縫對(duì)木梁受彎承載力的影響在于改變了承載力驗(yàn)算控制條件。由于裂縫削弱了木梁順紋抗剪截面面積,隨著裂縫深度的增加,木梁受彎承載力驗(yàn)算條件將由抗彎控制轉(zhuǎn)變?yōu)榭辜艨刂?本文通過提出裂縫開展界限指標(biāo)的計(jì)算方法來考慮縱向干縮裂縫對(duì)木梁受彎承載力的影響。當(dāng)裂縫深度等于界限值時(shí),木梁的抗彎強(qiáng)度和抗剪強(qiáng)度同時(shí)耗盡；當(dāng)裂縫深度小于界限值時(shí),木梁受彎控制條件為抗彎承載力,裂縫的影響可忽略不計(jì)；當(dāng)裂縫深度大于界限值時(shí),木梁受彎控制條件為抗剪承載力,應(yīng)考慮裂縫的影響。借助ABAQUS有限元軟件建立木柱、木梁的有限元模型進(jìn)行數(shù)值模擬,將有限元計(jì)算結(jié)果與試驗(yàn)實(shí)測值對(duì)比分析,驗(yàn)證了ABAQUS數(shù)值模擬木結(jié)構(gòu)構(gòu)件受力性能的可行性及可靠性。在此基礎(chǔ)上,利用有限元軟件進(jìn)行復(fù)雜裂縫參數(shù)變化分析,根據(jù)數(shù)值模擬結(jié)果對(duì)考慮縱向干縮裂縫影響的木構(gòu)件受力性能進(jìn)行理論分析,提出考慮縱向干縮裂縫影響的木構(gòu)件承載力折減系數(shù)的計(jì)算公式。數(shù)值模擬結(jié)果表明：構(gòu)件承載力折減系數(shù)與裂縫相對(duì)深度、裂縫相對(duì)長度均呈二次多項(xiàng)式關(guān)系,與裂縫寬度呈線性相關(guān),且裂縫寬度對(duì)木柱構(gòu)件承載力影響程度較小,對(duì)于寬度小于3mm的縱向干縮裂縫其影響可忽略不計(jì)。將公式計(jì)算結(jié)果與試驗(yàn)所測值進(jìn)行對(duì)比,驗(yàn)證本文計(jì)算方法的正確性。
[Abstract]:Wood, as a kind of building material, was widely used in the historical and traditional buildings, and the majority of the existing ancient buildings and settlements are wooden structures. However, because of its unique anisotropic characteristics, wood structure is obviously affected by temperature and humidity, which is mainly manifested in the formation of dry-shrinkage cracks along grain, while in historical buildings, the phenomenon of dry-shrinkage cracking is even more serious. Therefore, the influence of shrinkage cracks on the bearing capacity of wood members should be considered in evaluating the safety of the remaining wood structures in the settlement of historical buildings. In order to determine the influence of longitudinal dry shrinkage cracks on the mechanical properties of wood members, this paper simulates the natural dry shrinkage cracks by setting artificial fan-shaped joints. The axial compression tests of four groups of round section Chinese fir columns with different crack sizes and four groups of eight square cross-section Chinese fir beams with different crack sizes were designed. The effects of longitudinal cracks on axial compression capacity and bending capacity of wood beams are studied. The test results show that the ultimate bearing capacity of the test column with longitudinal sector joints is lower than that of the unslotted reference column under the same member size and test conditions. When the crack depth is shallow, the reduction of bearing capacity is negligible, and with the increase of crack depth, the decreasing degree of ultimate bearing capacity of wood column under axial compression will be more obvious. When the crack depth of the longitudinal dry split column reaches about 64% of the diameter of the column, the ultimate bearing capacity of the members under axial compression is 20% lower than that of the complete column member. The ultimate flexural capacity of the test beams with longitudinal sector joints is lower than that of the unjointed reference beams, and the reduction of the ultimate flexural capacity of the beams with shallow crack depth is negligible. With the increase of crack depth, the decrease of ultimate bearing capacity of wood beam will be more obvious. The influence of longitudinal shrinkage crack on flexural bearing capacity of wood beam depends on changing the control condition of checking calculation of bearing capacity. With the increase of crack depth, the checking condition of bending capacity of wood beam will be changed from bending control to shearing control. In this paper, the influence of longitudinal dry shrinkage crack on flexural bearing capacity of wood beam is considered by means of calculating the limit index of crack development. When the crack depth is equal to the limit value, the bending strength and shear strength of the wood beam are depleted simultaneously, and when the crack depth is less than the limit value, the bending bearing capacity of the wood beam is controlled, and the influence of the crack can be neglected. When the crack depth is greater than the limit value, the bending control condition of wood beam is shear bearing capacity, and the influence of crack should be considered. The finite element model of wood column and beam is established by ABAQUS software. The feasibility and reliability of ABAQUS numerical simulation of the mechanical behavior of wood structure members are verified by comparing the results of finite element calculation with the experimental results. On this basis, the finite element software is used to analyze the variation of complex fracture parameters. According to the results of numerical simulation, the mechanical behavior of wood members considering the effect of longitudinal dry-shrinkage cracks is theoretically analyzed. A formula for calculating the reduction coefficient of the bearing capacity of wood members considering the effect of longitudinal shrinkage cracks is presented. The results of numerical simulation show that the reduction coefficient of bearing capacity of members is quadratic polynomial relation with the relative depth of crack and the relative length of crack, and it is linearly related to the width of crack, and the influence of crack width on the bearing capacity of timber column member is small. The effect of longitudinal shrinkage crack with width less than 3mm is negligible. The calculation results of the formula are compared with the experimental values to verify the correctness of the calculation method in this paper.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU366.2

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