Glulam wood is growing frequently employed in modern wood structure engineering due to its great physical and mechanical qualities. In practical engineering, due to the anisotropic properties of wood materials, the bearing capacity will steadily drop under repeating cycle loads, which will eventually lead to fatigue damage. Therefore, how to strengthen the fatigue resistance of glued laminated wood beams has been the subject of study in the engineering domain. The goal of this research is to evaluate the impact of carbon fibre (CFRP) reinforcement on the fatigue performance and durability of glued laminated wood beams. In this work, variable amplitude fatigue tests were done on eight test beams with four separate loading modes. The test data demonstrate that the fatigue performance and fatigue life of CFRP reinforced glued laminated timber beams are considerably increased compared with those of standard glued laminated timber beams. The Delta S-e-N curves of glued laminated timber beams under variable amplitude fatigue loading were obtained by the equivalent stress amplitude method, and the fatigue limit strengths of ordinary glued laminated timber beams and CFRP reinforced glued laminated timber beams were determined to be 0.53 sigma(bu) and 0.58 sigma(bu), respectively. In this study, through systematic variable amplitude fatigue tests and theoretical analyses, the performance and damage mechanisms of glued laminated timber beams under variable amplitude fatigue loading have been revealed to provide a good basis for the design and application of high-performance timber structures. The design and application of high-performance wood structures provide innovative ideas and approaches.

ObjectiveIn order to solve the problem that the glued laminated wood beam web shear damage occurs when the glued laminated wood beam is loaded in bending because of the low shear strength of the web, without giving full play to the tensile and compressive capacity of the wood.MethodIn this paper, a new steel-wood combination I-beam with the web being an I-beam and the upper and lower wood plates bolted together was designed and subjected to three-equal point bending loading comparison tests together with glued laminated wood beams to observe the damage modes, mid-span deflection changes, section height and strain development of the wing plates of the steel-wood combination beam and glued laminated wood beam, respectively, to study the cross-sectional load capacity of the two structural beams.ResultThe test results showed that the damage mode of the glued woodworking beam was brittle with plain shear damage; the damage of the timber-steel combination I-beam was yielding of the steel web and plain shear damage of the wood flange; the ultimate load, initial stiffness and strength reserve of the timber-steel combination I-beam were 79.7%, 3.2% and 140.1% higher than those of the glued woodworking beam; the maximum longitudinal compressive strain of the wood flange of the top plate of the wood-steel combination I-beam was 2.08 times higher than that of the glued woodworking beam when the ultimate load was reached, and the longitudinal tensile strain of the timber flange of the bottom plate was 2.75 times that of the glued laminated timber beam.ConclusionThe wood-steel composite I-beam is a scientific and reasonable combination form, which not only effectively solves the problem of shear damage of glued laminated wood beams under bending loading due to low longitudinal shear strength, but also provides a reference for the structural study of wood-steel composite I-beams in beam units with large spans. The shear strength of the glued laminated timber I-beam obtained by using Rammer's formula has an error of 4.49% from the test. The research results also enable the tensile and compressive strength of I-beam timbers to be well developed.

【Objective】This article aimed to explore the eccentric compressive performance of larch glulam hollow columns.【Method】Oneway eccentric compressive bearing tests were conducted on seven groups of the specimen with different eccentric distances to study the failure mode, failure mechanism, bearing capacity, load-strain relationship, and load-deflection relationship of glulam hollow columns,and to compare the eccentric compressive columns with the axial compressive columns. By considering the lateral deflection in the column to increase the bending moment generated by the eccentric pressure, the calculation formula of the eccentric compressive bearing capacity of glulam hollow columns was proposed.【Result】The failure mode of the small eccentric compressive columns was that the timber on the curved concave side was compressed, resulting in longitudinal cracks, and the timber on the curved convex side had no obvious failure. The failure mode of large eccentric compressive columns was that the timber on the curved concave side was compressed and cracked longitudinally, and tensile failure was observed on the timber on the curved convex side. The ultimate bearing capacity of the specimens with an eccentric distance of 30-100 mm decreased from 61.51% to 31.16% of the bearing capacity of the axially compressed specimens. The difference between the calculation results of the improved formula of bearing capacity of the eccentric compressive column and the test value was within 10%, which was more accurate than the calculation of the current Standard for design of timber structures and the formula of the Technical code of glued laminated timber structures in China.【Conclusion】The eccentricity of the hollow column is about 0.6 for the limit of dimension eccentric. Differences between the large eccentric compressive failure and small eccentric compressive failure: the obvious failure observed on the curved convex side, the sudden failure of the curved convex side, the rapid decrease of the specimen bearing capacity, and the large flexural deformation. With the increase of eccentricity distance, the bearing capacity of the wooden column gradually decreases, but the declining range decreases. According to the load-strain relationship and load-deflection relationship curves, it is observed that the hollow glulam timber column has a certain plastic deformation capacity that meets the requirements of engineering materials. The research results provide theoretical references for engineering design.

The FRP-wood column elements are lightweight and high performance, meeting the social demand for sustainable construction. In this study, a basalt fiber reinforced polymer (BFRP) reinforced glued laminated wood hollow round column structure is proposed. Small eccentricity compressive tests and numerical simulations were carried out on glued wood hollow columns strengthened with BFRP to study the effect of BFRP arrangement on the mechanical properties of glued wood hollow columns with constant material, size and eccentricity. All samples are compression side of the wood first yielded, and then some samples tensile side of the end of the wood fracture or the central section of the wood was pulled off, which belongs to the typical compression bending failure and conforms to the characteristics of small eccentric compression. The compressive load capacity of the wood column after BFRP pasting was increased by 3.4%∼30.54%, and the lateral flexural stiffness was increased by 1.44%∼23.86%. Meanwhile, pasting BFRP at the end and middle of the wood column can effectively restrain the compression deformation at the end and bending deformation at the middle, and obtain higher load capacity and lateral flexural stiffness. The numerical simulation results agree well with the experimental results and can effectively characterize the mechanical properties of BFRP-reinforced glued laminated wood hollow round column under eccentric loading conditions.

To promote the development of timber–steel composite (TSC) structures, this paper proposes a TSC I-beam with an I-beam as the webs, covered with a timber board on its upper and lower surfaces and bolted together; the effect of varying the ratio of the timber board thickness to I-beam on the bending performance of the TSC I-beam was investigated. Considering the same total height of the beam cross-section and the variation of timber board thickness and I-beam height, three groups of six TSC beam specimens were designed and fabricated to carry out bending load failure tests, and the effects of the variation of timber board thickness with respect to I-beam height on the failure mode, flexural load capacity, ductility, and composite degree of TSC beams were analyzed. In addition, a model for predicting the elastic ultimate bending capacity and mid-span deflection of TSC I-beams was proposed on the basis of the composite coefficient method, which avoids the need to test the joints, and the theoretical calculation results were in good agreement with the test results, which can provide a reference for the design of TSC I-beams.

为探讨钢夹板螺栓连接胶合木梁的抗弯性能,针对采用钢夹板螺栓连接进行接长的胶合木梁的构造特点,考虑拼接的两段梁是否来源于同一根胶合木、螺栓顺纹间距及螺栓并列、错列布置3个影响因素,设计制作13组共39根试验梁,进行抗弯性能试验.采用有限元数值模拟方法,探讨钢夹板螺栓连接胶合木梁的破坏机理及螺栓端距和直径、钢夹板和胶合木厚度等影响参数对其抗弯性能和承载力的影响规律.试验与计算结果表明:螺栓顺纹间距对钢夹板螺栓连接胶合木梁的抗弯性能影响显著,而螺栓并、错列布置方式与拼接的两段梁是否来源于同一根胶合木对钢夹板螺栓连接胶合木梁的抗弯性能影响较小.随着螺栓顺纹间距的增大,试件的初始抗弯刚度和抗弯承载力明显提高.采用钢夹板螺栓连接方式可以实现胶合木梁的接长,在一定范围内增大螺栓端距和直径、钢夹板和胶合木的厚度还能提高钢夹板螺栓连接胶合木梁的抗弯承载力.装配式木结构中可以采用钢夹板螺栓连接方式对胶合木梁进行接长,其抗弯性能受螺栓顺纹间距的影响较大.对螺栓端距、螺栓直径、钢夹板厚度、胶合木厚度的参数研究可为装配式木结构的设计与应用提供参考.

为探讨胶合木连续梁的抗弯性能.以国产速生东北落叶松为基材,加工并制作了4组12根两跨胶合木连续梁,分别开展跨中集中荷载试验,并与相同设计参数的胶合木简支梁进行对比试验.通过实测各组梁的极限承载力与极限位移、荷载-跨中竖向位移曲线,定量分析胶合木连续梁在跨中荷载作用下的抗弯性能;并以梁的截面高度、梁的结构类型为参变量,研究其对胶合木梁抗弯刚度的影响.验证胶合木梁基本符合平截面假定后对比计算了胶合木连续梁、简支梁的弯矩-曲率曲线和跨中挠度.试验与计算结果表明:胶合木连续梁破坏形态为,中支点上缘发生受拉破坏,下缘发生局部受压破坏.相同条件下胶合木连续梁的极限承载力较简支梁提升了10.47％～22.48％,极限位移降低7.41％～24.37％,胶合木连续梁的抗弯刚度明显大于简支梁.胶合木连续梁和简支梁的弯矩?曲率曲线理论值与试验值基本吻合,连续梁弯矩?曲率曲线斜率明显大于简支梁.胶合木梁的跨中挠度计算值与试验值吻合较好.胶合木梁从简支梁过渡到连续梁,抗弯极限承载力与抗弯刚度大幅提升.理论分析结果表明,胶合木连续梁较简支梁在相同变形条件下所承受的截面弯矩更大,抗弯性能更好.

The present paper investigates the impact of basalt fiber reinforced polymer (BFRP) on the axial compression performance of glued wood hollow cylinders. This study aims to facilitate the application of BFRP in the field of structural reinforcement of glued wood hollow columns. Ten glued laminated wood hollow columns of the same size were designed and placed into five groups (ZC1 and ZRC2 to ZRC5), of which one group (ZC1), with a total of two pure wooden columns, was not arranged with BFRP, and the remaining two wooden columns in each group were arranged with BFRP at different distances. The destruction mode, ultimate load capacity, load–displacement curve, load–strain curve, and ultimate load capacity–total area of the BFRP paste curve of each specimen were obtained by conducting axial compression tests on five groups of wood columns reinforced with different basalt fiber cloths, which revealed the damage mechanism, the relationship between the ultimate load capacity and total area of BFRP paste, and pointed out the most effective area ratio. The test results show that the destruction mode of axially pressed, glued, laminated wood hollow columns is typical compression buckling damage, mainly manifested as follows: the wood at the middle or end of the specimen under pressure first buckles; then, with the increase in load, the specimen is crushed; at this time, the maximum ultimate bearing capacity of each specimen is in the range of 296.77~375.85 kN, the maximum longitudinal displacement is in the range of 2.77~3.38 mm, and longitudinal cracks appear at the end. It is worth noting that the growth rate of the ultimate bearing capacity varies with the increase in the total area of the BFRP paste. When the total area of the BFRP paste is less than a 3.2 × 105 mm2 range value, the growth rate of the ultimate bearing capacity is faster, and then, the growth rate gradually becomes slower. The optimum BFRP paste area ratio can be taken as k = 0.59. The ultimate bearing capacity after reinforcement increases from 11.06% to 26.65% compared with the pure wood column. According to GB50005-2017, “wood structure design standards” improve the hollow wood column bearing capacity calculation method and fit the BFRP reinforced hollow wood column’s ultimate bearing capacity calculation formula; the errors are within ±10%, which can provide a reference for the practical application of BFRP in the field of reinforcing glued wood hollow cylindrical structures.

The present paper investigates the impact of bolt distance, bolt diameter, and the number of bolt rows on the bending performance of timber–steel composite (TSC) beams. This study aims to facilitate the application of bolt connections in assembled TSC structures. Composite steel I-beams were designed with timber boards connected in the upper section with bolts. Three-point static bending tests were conducted on nine timber–steel composite beams divided into four groups (L1, L2, L3, and L4) with varying bolt arrangements. The destruction mode, ultimate bearing capacity, ductility coefficient, load–midspan deflection curve, and load–midspan strain curve of each specimen were obtained. In addition, the destruction mechanism, the quantitative relationship between the bolt area ratio and interfacial slip, and the ideal bolt area ratio were identified. It was found that when the midspan deflection of the timber–steel composite beam approached the prescribed limit, the main failure mode can be explained as follows: The top surface of the boards of all the specimens had longitudinal local splitting, except L1, which had fewer bolts and no obvious damage. Moreover, due to compression and because the stress at the lower edge of the I-beam entered the flow amplitude stage, some of the specimens were crushed but were not pulled off. The composite beams had high flexural load capacity and ductility coefficient, and the maximum relative slips of the timber–steel interfaces were in the range of 2–6 mm. It was also found that the maximum slip of the interface and the ductility coefficient decreased steadily as the bolt area ratio increased, while the specimen’s flexural bearing capacity increased. The optimal bolt area ratio was determined to be 8 × 10−3. Using the total bolt area, we designed the arrangement of the bolts on the board. For convenience, multiple bolt variables were converted into one bolt variable. The longitudinal distance of the bolts had a greater impact on the slip, and the bolt diameter had a smaller impact. The theoretical values of total relative slip were found to be in good agreement with the experimental results, which were based on the superposition of the relative slip equations with varying bolt distances. The effective bolt area ratio and the formula of the relative slip of each segment can provide instructions for the arrangement of bolts and the control of the relative slip of intersections in engineering practices.

为了提高木柱的承载力,提出了一种以兴安落叶松锯材为原材料、使用结构胶粘接形成的胶合木空心截面柱构件.制作了4组共12根胶合木柱试件,通过模型试验分析空心柱在偏心受压状态下的破坏过程、破坏模式与机理,以及承载力、应变、挠度变化规律,并采用实心胶合木柱做对比试验.研究结果表明:同体积材料、同柱高且偏心率相等时,空心柱相比实心柱,其承载力平均提高了20.02％,抗侧移刚度明显增加;偏心受压空心截面柱的破坏模式为首先受压侧木材屈服出现褶皱、然后柱子中部侧面出现竖向裂缝,最终被压溃;实心截面柱首先受压侧木材屈服出现褶皱,然后受拉侧开裂、木材被拉断,发生弯曲拉压破坏.研究成果可为胶合木空心截面柱设计提供理论依据.

Temperature acting on the structure can directly influence the mechanical property of a jointless bridg, so the length of jointless bridge is limited.This study proposed the novel seamless abutment bridge (SAB) as a supplement to expand the length of a jointless bridge and performed long-term field monitoring of the instrumented bridge Dayankeng Bridge to investigate the performance of the SAB under temperature effect.The finite element model was established, and analysis was performed to observe the mechanical performance of the bridge under temperature decrease.The parameters analysis was also carried out by considering the different materials of the base.Results demonstrate that structure temperatures closely track measured ambient temperatures, and the time-lag between ambient and structure temperatures is small because of the thermal inertia of the concrete structure.Thus, ambient temperature can be employed to represent structure temperature, the earth pressures around the sleeper beam increase with the increase of temperature difference, and the pressure is greater than one that is closer to the abutment.Approximately 20%-40% thermal displacement is absorbed by the structure behind the seamless abutment (such as pavement).With the increase of temperature difference, more deformation is absorbed by the pavement.The influence of the additional force acting on the girder induced by accessory structures behind the abutment is small.Furthermore, the impact of different materials of the base on the mechanical performance of SAB is minimal.Some suggestions can be provided to optimize the design of the SAB.

为深入研究装配式双肢钢拱塔在竖转吊装过程中的力学性能以及非线性稳定性,以一座双肢钢拱塔斜拉桥为工程背景,考虑几何非线性与材料非线性,采用ANSYS软件建立整个竖转吊装体系的有限元分析模型,并以竖转角度为唯一控制变量,定量地将整个竖转吊装过程划分成15个施工工况,通过分析各施工工况下竖转吊装体系的内力、变形以及非线性稳定系数的变化趋势来评定竖转吊装的安全性与可行性.研究结果表明,在整个竖转吊装过程中,起重门式塔架的跨中位移、应力峰值以及牵引索的应力均随竖转角度的增加而基本呈线性递减趋势;竖转角度的增加会导致钢拱塔主要的受弯区域由其顶部向腹部逐步转移,因此需要合理地上调中下部牵引索在吊装之前的预张力,从而优化钢拱塔吊装时的内力分布;整个竖转吊装体系的非线性稳定性系数均极大程度上地满足规范要求.

为研究钢-超高性能混凝土(Ultra-high Performance Concrete,UHPC)连续组合梁的抗弯承载能力,完成了2根大比例缩尺模型的静载试验,包括1根钢-UHPC连续组合梁和1根预应力钢-普通混凝土(Normal Strength Concrete,NC)连续组合梁,对其挠度、应力分布、裂缝发生发展模式及承载能力进行分析,并研究了钢-UHPC连续组合梁的弯矩重分布性能.同时,采用ABAQUS软件中的塑性损伤模型(CDP)进行数值模拟.结果 表明:钢-UHPC连续组合梁UHPC板的名义开裂强度为普通组合梁预应力NC板的2.2倍,钢-UHPC连续组合梁的极限承载力约为普通组合梁的1.2倍;UHPC板开裂后裂缝密集、间距小,且以长度较小的微裂纹为主;UHPC板/NC板与钢梁均采用群钉连接,二者相对滑移较小,可有效形成整体共同工作;采用塑性理论计算钢-UHPC连续组合梁的抗弯承载能力,应考虑UHPC的抗拉强度,与现有组合结构规范公式相比,根据所提出方法计算得到的负弯矩区截面抗弯承载力与试验值吻合较好;考虑UHPC抗拉强度后,钢-UHPC连续组合梁负弯矩区塑性铰转动能力降低,弯矩调幅需求及有效弯矩重分布能力均明显下降.

As a common engineering timber member used in the construction of timber bridges, a glulam T-beam has good mechanical properties.However, the low shear strength and various natural defects of timber cause the glulam T-beam to be prone to shear failure under load, and its shear performance is affected by web width and shear span ratio.To reveal the influences of web width and shear span ratio on the shear performance of glulam T-beams, five groups (10 in total) of glulam T-beam components and one group (2 in total) of glulam rectangular beam components were designed and manufactured with Larix gmelinii as a raw material.The deflection, strain, and ultimate bearing capacity of each component were measured using the mid-span concentrated force loading method.The failure mode of the component was observed, and its failure mechanism was discussed.The strain, deflection, and ultimate bearing capacity of each component were compared and analyzed.The calculation formula of the shear bearing capacity of a plywood T-beam was proposed.Results show that the failure mode of glued timber T-beam is shear failure along the grain.Compared with a rectangular beam, the ultimate bearing capacity of a glulam T-beam is increased by 71.36% on average, and the bending stiffness is increased by 131.28% on average.The shear capacity and bending rigidity of the glulam T-beam increase with the increase in web width and decrease with the increase in shear span ratio.The formula presented in this paper is reasonable and reliable, and the theoretical calculation value agrees well with the test value.This study can provide a reference for the engineering application and design of glulam T-beams.

The mechanical properties of timber, a traditional green engineering material, are greatly affected by timber grain, thus limiting the application of timber structures in modern engineering. This study aimed to broaden the engineering application of timber structures and fully exploit the tensile and compressive properties of timber along the grain by proposing a box-section timber-steel composite beam with larch plywood as the upper and lower flanges and welding cold-formed thin-wall channel as the web, and these materials were connected using bolts. Three timber-steel composite box beams and one plywood box beam were separately subjected to bending loading tests by stepwise loading. For the composite and plywood box beams, mechanical properties such as ultimate bending capacity and flexural stiffness were analyzed by observing the strain variation, deflection evolution, failure process, and shape of their flanges and webs under load effect. The shear lag coefficient and effective distribution width of the timber-steel composite box beam flanges were calculated according to the lateral flange strain distribution. Further, based on the computational formula of steel-concrete composite beams and considering the slip effect, the mid-span deflection and ultimate bearing capacity of the timber-steel composite box beams were quantitatively analyzed. Results show that the flanges and web of the composite box beams have good combination performance, and all the specimens undergo typical tensile and compressive failures accompanied by local buckling of steel and local splitting of timber. Plywood box beams are damaged via shear web failure along the grain. Steel web of composite box beams has better shear resistance than timber, subsequently, the ultimate bending capacity of the composite box beams increase with an average of 30.3% compared to the plywood box beams, although the initial stiffness decrease by 34.8% on average. The calculations of the bearing capacity are in good agreement with the experimental results and meet the requirements of practical engineering applications. This study provides significantly references and new insights into widening the modern engineering application of timber structures.

[目的]为探明胶合木-钢夹板螺栓连接的动力性能和抗震性能,确保连接件在车辆、机械振动等动力荷载下的可靠性.[方法]针对胶合木-钢夹板螺栓连接的构造特点,考虑胶合木厚度和螺栓直径之比(厚径比)、螺栓顺纹间距、螺栓并列和错列布置方式等参数的影响,设计制作了4类13组共39个胶合木-钢夹板螺栓连接件,在低周反复荷载作用下进行滞回性能试验.[结果]试验结果表明:在单螺栓连接中,连接部位的破坏模式逐渐由"螺栓刚直"向"双铰"转化,胶合木销槽破坏模式逐渐由销槽整体承压破坏向两端部挤压破坏转变,试件滞回曲线基本都呈现饱满的弓形和棱形,具有良好的耗能能力和抗震性能,但其承载能力较低.在多螺栓连接中,螺栓和胶合木的破坏模式分别以"双铰"破坏和销槽端部挤压破坏为主,试件滞回曲线均呈现饱满棱形,该类试件在承载能力、抗震性能和耗能能力上均有大幅提升;随着螺栓顺纹间距的增大,试件的承载能力不断增大,但螺栓顺纹间距在200 mm时,极限荷载增幅趋于平缓,初始刚度增涨大幅放缓,且整体刚度退化与螺栓顺纹间距为250 mm时基本相同;螺栓并列布置滞回曲线饱满程度好于错列布置;螺栓双排布置承载能力比单排布置的承载能力更高,刚度退化更小.[结论]胶合木-钢夹板螺栓连接具有较好的耗能能力、抗震性能及延性性能;螺栓顺纹间距在200 mm时,抗震性能最佳;螺栓错列布置的抗震性能比并列要好,螺栓双排布置的抗震性能更优越.

[目的]近年来,随着国家在节能减排方面的要求提高,以及大力倡导使用新型绿色材料,木材作为一种传统绿色环保的建材逐渐受到人们的青睐.正交胶合木(CLT)板是近年来兴起的一种建造现代木结构建筑的新型构件,具有良好的整体性、稳定性以及较高的强度.为了研究组坯方式对正交胶合木(CLT)双向板的弯曲性能,本研究采用2种组坯方式(三层交叉和四层交叉)制作了2组厚度相同的胶合木双向板试件,研究其静力弯曲性能.[方法]用于制作试件的原材料为兴安落叶松板材与聚氨酯结构胶粘剂,制作2组、每组2个共4个正交胶合木双向板试件,通过千斤顶在板的跨中施加单点集中荷载,同时测试和分析应变、挠度和极限荷载等数据,观察裂缝开展及破坏形态,研究胶合木双向板的弯曲性能,探讨其最终破坏特征和破坏机理;运用正交各向异性弹性薄板理论对CLT双向板进行了挠度分析,并与试验结果进行了比较.[结果]正交胶合木(CLT)双向板的破坏形态主要是板底横纹受拉破坏,当加载至极限荷载80％ 左右时,承载能力快速下降.对于相同厚度的CLT板,四层组坯与三层组坯相比,受弯承载力提高了22.7％.[结论]对两组胶合木双向板构件的结构力学性能(平均值)进行比较,三层正交胶合木双向板与四层正交胶合木双向板相比,厚度相同的双向板在四边简支的情况下增加板的胶合层数能提高双向板的整体承载能力.正交各向异性弹性薄板理论计算正交胶合木双向板弹性阶段的挠度值与试验值吻合较好,表明提出的方法合理、可靠.

This article proposes a new kind of continuous composite beam that consists of steel box-girder and ultra-high-performance concrete waffle slab. The ultra-high-performance concrete helps increase the ultimate capacity and span of structure while reducing the risk of cracking that occurs with ordinary concrete. In order to investigate the mechanical properties of this new type of composite structure, two scaled specimens were designed and tested. One was a steel–ultra-high-performance concrete continuous composite beam, whereas the other, as a control specimen, was a prestressed steel-concrete continuous composite beam. The test results indicate that the bending capacity of steel–ultra-high-performance concrete continuous composite beam is 1.2 times that of steel-concrete continuous composite beam; the cracking strength of steel–ultra-high-performance concrete continuous composite beam is larger than 20 MPa, much higher than the conventional one; the crack development pattern of steel–ultra-high-performance concrete continuous composite beam has its own characteristics, and the cracks appeared in ultra-high-performance concrete slab dominated by micro-cracks with smaller length are numerous and intensive. A finite element model was developed to predict the behavior of steel–ultra-high-performance concrete continuous composite beam. Comparing the numerical and experimental results indicates that, generally, the numerical model can simulate the structural behavior of steel–ultra-high-performance concrete continuous composite beam reasonably. Based on the numerical model, a series of parameter analyses were performed, which indicate that the strength grade of steel, web, and bottom plate thickness play an important role in improving the bending capacity of steel–ultra-high-performance concrete continuous composite beam; the axial tensile strength of ultra-high-performance concrete, rib, and top plate height of ultra-high-performance concrete slab can enhance the bending capacity to a certain extent.

[目的]探讨胶合木T梁的负弯曲性能,观察极限状态下构件的破坏形式,解析极限状态下构件的破坏机理,推导极限承载能力计算模型,以期为工程实际应用提供理论参考依据.[方法]采用跨中荷载试验与理论计算对比方式进行研究,实测分析了两组试件的应变、挠度、抗弯刚度、极限承载力及延性结果,观察分析了胶合木梁的破坏形态与破坏机理,基于Rammer剪切强度公式将弯剪强度理论值和试验值进行了对比.用兴安落叶松作为原材料,以剪跨比、跨高比为参数,设计制作2组即A组3根(高跨比1/12,剪跨比5.2)、B组3根(高跨比1/14,剪跨比6.1),共计6根平行胶合木T梁试件.将T梁反转成倒T梁,在两端简支条件下跨中加载产生正弯矩,使肋板受压、翼板受拉,模拟连续T梁跨中支承截面的受力性能.[结果]1)两组构件整体工作性能良好,受弯时极限破坏形态均为中部顺纹剪切破坏.2)两组构件相比,B组较于A组试件,屈服荷载降低9.7％,跨中屈服位移提高27.5％,极限抗弯承载力降低10.4％,跨中极限位移提高42.7％,抗弯刚度降低36％,延性系数提高22.4％.3)两组构件的荷载应变曲线在达到屈服点之前呈比例关系,满足平截面假定.4)受剪力滞效应影响,两组构件的跨中截面翼缘板正应力横向分布不均匀,呈现随距离肋板中心位置越远而越小的关系,最大差值比率达30％.5)构建了弯剪承载力计算模型,理论值与试验值最大相差3.1％,匹配度较高.[结论]总结了胶合木连续T梁在跨中支承截面的受力变形规律,揭示了其破坏机理,构建了极限弯剪承载力计算模型,经验证,具有一定的可靠性.

Cross-laminated timber (CLT) plates are new components in modern wooden building structures and have good integrity, stability, and high strength.However, the bending performance of CLT plate is affected by the stacking method of laminates.This study adopted two different stacking methods (three-layer cross and four-layer cross) to make four CLT two-way slabs by using Larix gmelinii slab and polyurethane structural adhesive as raw materials.The slabs were divided into two groups to reveal the effects of stacking method on the bending performance of CLT two-way plates.A jack was used to apply concentrated load on a single point of the middle span of slabs, and the strain, deflection, and ultimate load data were measured.The crack development and failure mode were observed.The ultimate failure characteristics and failure mechanism were discussed, and the finite element model of CLT two-way slab was established using structural analysis software.The influence of elastic-plastic and plywood layers on the bending properties of CLT two-way slab was analyzed, and the results were compared with the experimental results.Results show that the failure modes of CLT two-way slabs are mainly from the transverse grain tensile failure of the slab bottom, and the bearing capacity decreases rapidly when the load reaches to approximately 80% of the ultimate load.For the same thickness of CLT plate, the flexural capacity of four-layer plate is increased by 14.08%, and the elastic bending stiffness is increased by 13.63% compared with three-layer plate.The overall bearing capacity and flexural stiffness of a two-way CLT slab with the same thickness can be improved by increasing the number of laminates when four sides are simply supported.The optimal number of laminates is five.The result of finite element simulation aligns with the test, showing that the test results and analysis are reliable.This study can provide references for future engineering design.