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.

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.

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.

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.