A Review of Basic Mechanical Properties of Bamboo Scrimber Based on Small-Scale Specimens

This review summarizes the existing knowledge about the mechanical properties of bamboo scrimber(BS)in literature.According to literature reviews,the strength of BS under different load modes is affected by a series of factors,such as the type of original bamboo,growth position,resin content,treatment method and density.Therefore,different production processes can be adopted according to different requirements,and bamboo scrimbers can also be classified accordingly.In addition,this review summarizes the changes in different factors considered by scholars in the research on the mechanical properties of BS,so that readers can have an overall understanding of the existing research and make more innovative and valuable research on this basis.This review provides and discusses the conclusive observations,the current research gaps and future research directions on the mechanical properties of BS.

Experimental Study on the Axial Compression Performance of Bamboo Scrimber Columns Embedded with Steel Reinforcing Bars

In this paper,a new type of bamboo scrimber column embedded with steel bars(rebars)was proposed,and the compression performance was improved by pre-embedding rebars during the preparation of the columns.The effects of the slenderness ratio and the reinforcement ratio on the axial compression performance of reinforced bamboo scrimber columns were studied by axial compression tests on 28 specimens.The results showed that the increase in the slenderness ratio had a significant negative effect on the axial compression performance of the columns.When the slenderness ratio increased from 19.63 to 51.96,the failure mode changed from strength failure to buckling failure,and the maximum bearing capacity decreased by 43.03%.The axial compression performance of the reinforced bamboo scrimber columns did not significantly improve at a slenderness ratio of 19.63,but the opposite was true at slenderness ratios of 36.95 and 51.96.When the reinforcement ratio increased from 0%to 4.52%,the bearing capacity of those with a slenderness ratio of 51.96 increased by up to 16.99%,and the stiffness and ductility were also improved.Finally,based on existing specifications,two modification parameters,the overall elastic modulus Ec and the combined strength fcc,were introduced to establish a calculation method for the bearing capacity of the reinforced bamboo scrimber columns.The calculation results were compared with the test results,and the results showed that the proposed calculation models can more accurately predict the bearing capacity.

Mechanical Properties and Stress Strain Relationship Models for Bamboo Scrimber

In order to investigate the basic mechanical properties and stress strain relationship model for bamboo scrimber manufactured based on a new technique,a large quantities of experiments have been carried out.Based on the analysis of the test results,the following conclusions can be drawn.Two main typical failure modes were classified for bamboo scrimber specimens both under tension parallel to grain and tension perpendicular to grain.Brittle failure happened for all tensile tests.The slope values for the elastic stages have bigger discreteness compared with those for the specimens under tensile parallel to grain.The failure modes for bamboo scrimber specimens under compression parallel to grain could be divided into four.Only one main failure mode happened both for the bending specimens and the shear specimens.With the COV values of 28.64 and 25.72 respectively,the values for the strength and elastic modulus under tensile perpendicular to grain have the largest discreteness for bamboo scrimber.From the point of CHV values,the relationship among the mechanical parameters for bamboo scrimber were proposed based on the test results.Compared with other green building materials,bamboo scrimber manufactured based on a new technique has better mechanical performance and could be used in construction area.Three stress strain relationship models which are four-linear model,quadratic function model,and cubic function model were proposed for bamboo scrimber specimens manufactured based on a new technique.The latter two models gives better prediction for stress strain relationship in elastic plastic stage.

Flexural Performance of CFRP-Bamboo Scrimber Composite Beams

This study presents a new structure made up of bamboo scrimber and carbon fiber reinforced polymer(CFRP)to address the low stiffness and strength of bamboo scrimbers.Three-point bending test and finite element model were conducted to study the failure mode,strain-displacement relationship,load-displacement relationship and relationships between strain distribution,contact pressure and deflection,and adhesive debonding.The results indicated that the flexural modulus and static flexural strength of the composite beams were effectively increased thanks to the CFRP sheets.The flexural modulus of the composite specimens were 2.33-2.94 times that of bamboo scrimber beams,and the flexural strength were 1.49-1.58 times that of bamboo scrimber beams.Adhesive debonding had a great influence on the strain distribution and deflection of the composite specimens.It was an important factor for the failure of the CFRP-bamboo scrimber composite specimens.According to the finite element simulation,the strain distribution,contact pressure and deflection also greatly changed with the adhesive debonding.After complete peeling,the deflection of the specimen was 3.09 times that of the unpeeled because it was no longer an integral beam.

Experimental and Theoretical Study on Bonding Properties between Steel Bar and Bamboo Scrimber

To further verify the feasibility of newly designed reinforced bamboo scrimber composite(RBSC)beams used in building construction,the bonding properties between steel bar and bamboo scrimber were investigated by anti-pulling tests.Results indicated that the anti-pulling mechanical properties were significantly correlated to the diameter,thread form and buried depth of steel bar,forming density of bamboo scrimber as well as the heat treatment of bamboo bundle.There were two failure modes for anti-pulling tests:the tensile fracture and pulling out of steel bar.Both the ultimate load and average shear strength of anti-pulling specimen could be increased greatly with the ribbed bar,high forming density of bamboo scrimber and un-heated bamboo bundle.Furthermore,a theoretical calculation model of the bonding interface between steel bar and bamboo scrimber was developed.Based on the theoretical calculation model,the change laws of normal stress of bamboo scrimber,and shear stress of glue layer along the buried depth of steel bar were revealed.This study is beneficial for the safety application of RBSC beams in building construction.

Dynamic Testing of Elastic Modulus,Shear Modulus,and Poisson’s Ratio of Bamboo Scrimber

The bamboo scrimber is an anisotropic material.The elastic constant values of the bamboo scrimber specimens measured by the dynamic and static methods are consistent,and the dynamic test method has the advantages of rapidity,simplicity,good repeatability,and high precision.Bamboo scrimber has strong potential as a building material,and its elastic constant is an important index to measure its mechanical properties.To quickly,simply,non-destructively,and accurately detect the elastic constant of the bamboo scrimber,they were dynamically tested by the free plate transient excitation method and cantilever plate torsional vibration method.The static four-point bending method was used to verify the accuracy and reliability of the dynamic elastic modulus,shear modulus,and Poisson’s ratio of the bamboo scrimber.The mechanism analysis and evaluation of the quality grade,homogeneity,and size effect of the bamboo scrimber whole board were carried out.The main results show that the dynamic elastic modulus,shear modulus,and Poisson’s ratio of the bamboo scrimber are 12 GPa,1500 MPa,and 0.31,respectively,which meet the requirements of GB/T 40247-2021 for structural bamboo scrimber.

Theoretical Analysis on Deflection and Bearing Capacity of Prestressed Bamboo-Steel Composite Beams

A theoretical analysis of upward deflection and midspan deflection of prestressed bamboo-steel composite beams is presented in this study.The deflection analysis considers the influences of interface slippage and shear deformation.Furthermore,the calculation model for flexural capacity is proposed considering the two stages of loading.The theoretical results are verified with 8 specimens considering different prestressed load levels,load schemes,and prestress schemes.The results indicate that the proposed theoretical analysis provides a feasible prediction of the deflection and bearing capacity of bamboo-steel composite beams.For deflection analysis,the method considering the slippage and shear deformation provides better accuracy.The theoretical method for bearing capacity matches well with the test results,and the relative errors in the serviceability limit state and ultimate limit state are 4.95%and 5.85%,respectively,which meet the accuracy requirements of the engineered application.

Review on the Application of Bamboo-Based Materials in Construction Engineering

Due to the continuously increasing demand for building materials across the world,it is necessary to use renewable materials in place of the existing nonrenewable materials in construction projects.Bamboo is a fast-growing flowering plant that may be used as a renewable material in construction.The use of bamboo in the construction of buildings can improve its long-term carbon fixation capacity and economic benefits.Although bamboo has the advantages of superior performance,low carbon content,high energy-saving and emission-reducing capacity,bamboo is an anisotropic material,which has many factors affecting its material performance,large variability of material performance,lack of systematic research,and the use of bamboo as the main building material is not always limited.This paper systematically summarizes the research status of bamboo as a building material from the aspects of bamboo composition,gradation,material properties,bamboo building components,connection nodes,and use of artificial boards.On this basis,some constructive suggestions are put forward for the further study of bamboo in the field of architecture.

Acoustic Emission Characteristics of Different Bamboo and Wood Materials in Bending Failure Process

The acoustic emission(AE)technique can perform non-destructive monitoring of the internal damage development of bamboo and wood materials.In this experiment,the mechanical properties of different bamboo and wood(bamboo scrimber,bamboo plywood and SPF(Spruce-pine-fir)dimension lumber)during four-point loading tests were compared.The AE activities caused by loadings were investigated through the single parameter analysis and K-means cluster analysis.Results showed that the bending strength of bamboo scrimber was 3.6 times that of bam-boo plywood and 2.7 times that of SPF dimension lumber,respectively.Due to the high strength and toughness of bamboo,the AE signals of the two bamboo products were more abundant than those of SPF dimension lumber.However,the AE evolution trend of the three materials was similar,which all experienced three stages,including gentle period,steady period and steep period,and the area of rupture precursor characteristics could be recognized before the specimen destroyed.Due to the bottom layer was first tensile failure,the main structure of bamboo plywood was destroyed after the stress redistribution.The rupture precursor characteristics could be observed before each peak.Findings put in evidence a good correlation between AE clusters of two bamboo products,while the amplitude and energy of wood signals were lower than those of bamboo.The amplitude and energy from the propagation and aggregation of cracks were greater than those related to micro-cracks initiation.

Mechanical Properties and Constitutive Relationship of the High-Durable Parallel Strand Bamboo

Engineered bamboo has recently received lots of attention of civil engineers and professional researchers due to its better mechanical performance than that of softwood timber.Parallel strand bamboo is one important part of engineered bamboo for its excellent durable performance compared to the laminated veneer bamboo.The required curing temperature in hot-pressing process is usually higher than 120°C to reduce the content of nutri-tional ingredients and hemy cellulose,and to avoid the decay from the environment and insects.Nonetheless,the appearance of engineered bamboo gets darker with the increase of temperature during the hot-pressing process.In order to minimize the color deepening while maintaining the durability,a high-durable parallel strand bamboo(HPSB)with relative high hot-pressing temperature(140°C)was produced and tested.The present study inves-tigates the mechanical performance through tension,compression,shear and bending tests.The experimental behavior of the specimens was identified,including the failure mode and load-displacement relationship.It was demonstrated that the HPSB material had better mechanical performance parallel to grain,making it as a considerable structural material.The average elastic modulus parallel to grain was 14.1 GPa,and the tensile and compressive strengths were 120.7 MPa and 121.0 MPa,respectively.The tension perpendicular to grain should be avoided in the practical application due to the lower strength and elastic modulus.Two stress-strain relationships of tension and compression parallel to grain,including three-linear and quadratic function models,were proposed and compared with the experimental results.The three-linear model was then applied to the finite element model.The finite element analysis using ANSYS software was conducted to validate the feasibility of the constitutive relationship.The quadratic function model showed better agreement with the experimental results,but the three-linear relationship was also precise enough to analyze the bending tests of HPSB material,whereas being less accurate to describe the elastic-plastic compression behavior.

建筑建材领域“以竹代塑”工程材料研究现状与发展趋势

随着全球对可持续发展的关注,建筑行业面临着传统建材带来的环境问题。塑料作为一种广泛使用的建筑材料,虽然具备良好的物理特性,但其不可降解性对环境造成了重大影响。竹材作为一种快速再生资源,具有优良的力学性能和环境友好特性,以竹材为基础的“以竹代塑”工程材料逐渐成为研究和应用的热点,展现出良好的环保性能与经济价值。聚焦于“以竹代塑”工程材料作为传统塑料替代品的优势和潜力,综述了当前建筑建材领域“以竹代塑”工程材料的研究现状,包括材料分类、制备工艺、改性技术和实际应用,系统分析了“以竹代塑”工程材料在建筑建材领域的应用必要性,探讨了“以竹代塑”工程材料的制备工艺与改进方向,并通过国内外研究现状分析,提出“以竹代塑”工程材料目前存在的主要问题及发展建议。研究表明,“以竹代塑”工程材料在强度、耐久性等方面展现出良好性能,不仅能够有效替代传统塑料建材,还可以降低建筑行业的碳排放,推动绿色建筑发展,目前已成功应用于生态建筑等领域。然而,现阶段相关标准和规范尚不完善,市场推广不足。对“以竹代塑”工程材料在建筑建材领域的应用研究现状进行系统综述,旨在为竹材在工程结构行业的推广应用提供理论支持。未来,随着技术创新、市场需求的增加以及政策支持的强化,“以竹代塑”工程材料有望在建筑建材领域中获得更广泛的应用。

重组竹内置钢筋后受弯性能有限元分析

重组竹是通过将竹束热压胶合而成的新型工程材料,具有强度高、韧性好以及固碳能力强等优点,为提高重组竹的受弯性能,通过热压工艺在重组竹中内置钢筋形成增强重组竹受弯构件。在四点弯曲试验的基础上,通过ABAQUS有限元模拟研究配筋率及配筋形式对重组竹受弯性能的影响。分析结果表明,与纯重组竹相比,内置钢筋后重组竹的受弯力学性能得到明显提高;当配筋形式相同时,随配筋率的增加,重组竹的承载力及抗弯刚度逐渐提高,与纯重组竹相比,配筋率为1.0%~8.2%的单筋重组竹承载力和抗弯刚度分别提高5.6%~48.36%和10.57%~71.81%;当钢筋直径相同时,重组竹顶部和底部同时配筋的双筋重组竹与重组竹底部配筋的单筋重组竹相比,其承载力及抗弯刚度分别提高21.78%和95.98%。

新型CFRP网格-重组竹复合板力学试验研究

为提高重组竹的力学性能并减轻其各向异性缺陷,设计了一种新型CFRP网格-重组竹复合板(CBCP).分别对8组CBCP拉伸试样和18组CBCP拉拔试样进行单轴拉伸试验和拉拔试验,以分析其力学行为并评估复合方法的影响.选择3个相似的构成模型对拉拔试样的黏结应力-滑移曲线进行拟合,根据试验结果确定CFRP网格和重组竹的临界锚固长度及计算方法,并分析讨论了CFRP层数、横向CFRP束特性和锚固长度对CFRP网格与重组竹黏结性能的影响.结果表明,复合CFRP网格可使重组竹的顺纹和横纹抗拉强度分别提高35.77%和135.20%,从而改善了重组竹的各向异性缺陷.增加网格层数和间距可提高CBCP的拉伸性能.随着锚固长度的增加,平均界面黏结强度呈幂函数递减,而峰值载荷滑移则线性递减.

环保型家具用重组竹的制备及性能研究

本研究采用低温固化环保型酚醛树脂为胶黏剂制备重组竹板材,探索热压温度、施胶量和板材密度对重组竹物理力学性能的影响。结果表明:当热压温度为125℃时,板材芯层温度即能达到胶黏剂的固化温度范围,且此条件下的板材密度均匀性、理化力学性能以及各项性能的稳定性更优。然而,热压温度升高对性能的改善不明显。当施胶量达到8.6%以上时,重组竹的密度可达到1.00 g/cm^(3),物理力学性能较优。

高密度重组竹的物理力学性能研究

分析了高密度重组竹的孔隙率、微观结构、耐水性和力学性能,并通过构建性能参数与密度的关系,探究密度对物理力学性能的影响规律。结果表明:随着密度的增大,孔隙率逐渐降低。当密度为1.37 g/cm3时,孔隙率仅为5.52%,竹材细胞基本实现了密实化;薄壁细胞和导管细胞发生严重变形,但纤维细胞的形态几乎未受影响。经4 h水煮-20 h 60℃干燥-4 h水煮处理后,吸水率、厚度膨胀率和宽度膨胀率均随密度的增大而下降,分别低至9.67%、7.62%和1.47%。水平剪切强度、顺纹抗压强度、静曲强度(MOR)和弹性模量(MOE)则随密度的增大而增大,分别高达28.83、215.53、354.00 MPa和28.75 GPa。所有重组竹的性能参数均达到了户外用重组竹的性能要求,且部分参数远超国标中规定的最高等级要求。此研究结果可为重组竹性能的调控与应用提供理论依据和数据参考。

疏解工艺对簕竹重组材力学性能及尺寸稳定性的影响

本文以簕竹为原料制备重组材,研究了不同疏解工艺对簕竹重组材力学性能和尺寸稳定性的影响,并通过与毛竹重组材对比,探讨其利用价值。结果表明:随着疏解程度的增加,竹束的载胶量增大,竹青竹黄的存在使竹束对胶黏剂的吸附能力下降;相同条件下,簕竹重组材与毛竹重组材水平剪切强度相当,弹性模量及静曲强度约为毛竹的2倍左右,经28 h循环水处理吸水厚度膨胀率约为毛竹的1/2;带青带黄疏解有利于提高簕竹重组材的抗弯性能,制备的重组竹静曲强度达215 MPa,弹性模量达28 GPa,分别高于常规疏解的8.64%和12.92%,但其水平剪切强度略有下降。竹青的存在可以提高簕竹表面的耐水性,簕竹青黄宽疏解在60 s时接触角仍能达到60°,较其余条件耐水性高。以簕竹开发制备重组材在工程应用上具有较大潜力。

密度和含水率对重组竹顺纹抗拉强度的影响

【目的】探究不同密度和含水率下重组竹顺纹抗拉强度的变化规律,提出重组竹顺纹抗拉强度与密度、含水率的相关模型,为推进重组竹在工程中的应用提供依据。【方法】参考ASTM D143—14《木材无疵小试样的标准试验方法》,选取不同密度(1.1、1.2、1.3 g·cm^(-3))和含水率(4%、8%、12%、16%、20%)的重组竹试件进行正交抗拉试验,分析重组竹顺纹抗拉的主要破坏形态;采用线性模型和抛物线模型拟合重组竹顺纹抗拉强度随密度的变化规律,采用线性模型和ASTM模型拟合重组竹顺纹抗拉强度随含水率的变化规律,提出重组竹顺纹抗拉强度在密度和含水率双因素影响下的耦合模型。【结果】重组竹顺纹抗拉的主要破坏形态为平口破坏和斜口破坏,重组竹密度越大,平口破坏概率越大;重组竹含水率越大,斜口破坏概率越大。基于试验研究和数据拟合提出重组竹顺纹抗拉强度的单因素影响模型和双因素耦合模型,理论结果与试验结果吻合良好。【结论】在本研究密度范围内,重组竹顺纹抗拉强度随密度增加而增大、随含水率升高而减小。线性组合模型和ASTM组合模型均能较好预测重组竹顺纹抗拉强度在密度和含水率双因素影响下的理论值,线性组合模型计算更为简便,在实际预测中建议直接使用线性组合模型。

高密度重组竹的漆膜附着性能研究

为阐明高密度重组竹的表面涂饰性能,分析了不同密度重组竹的表面形貌、粗糙度、润湿性和漆膜附着力,考察了密度对漆膜附着力的影响。结果表明:重组竹的密度越高,其表面越光滑,粗糙度越小,Ra最低仅为1.71μm。同时,随着重组竹密度的增大,蒸馏水、甲酰胺和二碘甲烷三种极性不同的液体的接触角变大,表面自由能也随之降低。受表面粗糙度和润湿性的影响,低密度的重组竹与高密度的相比,具有更高的漆膜附着性能。然而,根据GB/T4893.4—2013对漆膜附着力的分级,所有重组竹对水性和油性木器底漆的表面漆膜附着力均为2级,表明密度对重组竹表面的漆膜附着力无显著影响。研究结果可为高密度重组竹的表面涂饰处理提供理论支持。

重组竹方销对正交胶合木力学与声学特性的影响

为提升正交胶合木(CLT)的中低频隔声性能,设计了一种以重组竹方销为声散射体的二维声子晶体结构的CLT,探究对嵌入重组竹方销的杉木CLT力学和声学特性的影响。采用短梁剪切法,研究了跨中面外开孔的CLT短梁和嵌入重组竹方销的CLT短梁层间剪切强度、最大正应力和静态韧性系数;采用阻抗管测试法,研究了周期性排布的重组竹方销对CLT隔声量的影响规律。短梁剪切试验表明:与未开孔CLT相比,开孔使CLT的层间剪切强度下降了13.0%~16.5%;与开孔CLT相比,方孔中嵌入重组竹方销可使开孔CLT的层间剪切强度提升8.5%~12.7%,从而与未开孔CLT的层间剪切强度差异不显著,其最大正应力分别与开孔和未开孔的CLT最大正应力差异不显著,为24.52~29.45 MPa;方孔中嵌入重组竹方销的CLT在静态韧性系数上相比未开孔的CLT上升了13.9%~19.1%。隔声量测试结果表明:嵌入重组竹方销的CLT属局域共振型声子晶体结构,在1 400 Hz出现吻合效应的隔声量谷值约33.41 dB;以重组竹方销为声散射体的二维声子晶体结构随重组竹方销边长的增加,提高了CLT的密度和中低频的隔声量,其中,600 Hz以下的隔声量可提升约20.22%。在不改变CLT厚度、密度增量小于20%且力学性能差异不显著的前提下,以重组竹方销增强CLT隔声性能是可行的。

密度与含水率双因素作用下重组竹顺纹弹性模量的预测与分析

本研究选取3组不同密度(1.10、1.20、1.30 g/cm^(3))和5组不同含水率(4%,8%,12%,16%,20%)的重组竹试件进行顺纹抗拉、抗压试验,分析不同密度和含水率作用下重组竹顺纹抗拉、抗压弹性模量的变化规律。结果发现,重组竹顺纹抗拉、抗压弹性模量随密度的增大而增大,随含水率的升高而减小并趋于平衡;通过试验研究和数据拟合提出重组竹顺纹抗拉、抗压弹性模量的双参数耦合模型,线性组合模型和ASTM组合模型均能较好地预测重组竹顺纹抗拉、抗压弹性模量随密度和含水率变化后的理论值,顺纹抗拉弹性模量的实测值与线性组合模型和ASTM组合模型预测值之间最大误差为5.28%和8.20%;顺纹抗压弹性模量的实测值与线性组合模型和ASTM组合模型预测值之间最大误差为8.91%和8.67%,因线性组合模型计算更为简便,建议在实际应用中优先选用。