Bakalarz Michał Marcin, Kossakowski Paweł Grzegorz
Department of Theory of Structures and Building Information Modeling (BIM), Faculty of Civil Engineering and Architecture, Kielce University of Technology, Al. Tysiaclecia Panstwa Polskiego 7, 25-314 Kielce, Poland.
Materials (Basel). 2024 Dec 27;18(1):71. doi: 10.3390/ma18010071.
The bending stiffness of beams represents a pivotal parameter influencing both the dimensions of the elements during their design and their subsequent utilisation. It is evident that excessive deflections can cause discomfort to users and contribute to further structural degradation. The objective of this study was to enhance the bending stiffness of timber beams by bonding a composite sheet to their external surfaces. A carbon sheet exhibiting an ultra-high modulus of elasticity and low elongation at rupture was employed. Two variables of analysis can be distinguished including whether the reinforcement was applied or not and the number of reinforcement layers. The beams, with nominal dimensions of 80 × 80 × 1600 mm, were subjected to a four-point bending test in order to ascertain their mechanical properties. In total, 15 beams were tested (5 unreinforced and 10 reinforced). The reinforcement had no appreciable impact on the increase in flexural load capacity, with the maximum average increase recorded at 9%. Nevertheless, an increase in stiffness of 34% was observed. Additionally, significant increases were observed in ductility up to 248%. However, the ductile behaviour of the beam occurred after the rupture of the reinforcement. In all instances, the failure was attributed to the fracturing of the wooden components or the UHM CFRP (ultra-high-modulus-carbon-fibre-reinforced polymer) sheet. The numerical analysis proved to be a valuable tool for predicting the stiffness of the wood-composite system, with a relatively low error margin of a few percentage points. The modified approach, based on the equivalent cross-section method, permits the determination of a bilinear load deflection relationship for reinforced beams. The aforementioned curve is indicative of the actual behaviour. Given the propensity for the sudden rupture of reinforcement, the described method of reinforcement is recommended for beams subjected to lower levels of stress.
梁的抗弯刚度是一个关键参数，在其设计阶段及后续使用过程中都会影响构件的尺寸。显然，过大的挠度会给使用者带来不适，并加速结构的进一步退化。本研究的目的是通过在木梁外表面粘贴复合板来提高其抗弯刚度。采用了一种具有超高弹性模量和低断裂伸长率的碳板。分析中有两个变量，包括是否进行加固以及加固层数。梁的标称尺寸为80×80×1600毫米，通过四点弯曲试验来确定其力学性能。总共测试了15根梁（5根未加固，10根加固）。加固对弯曲承载能力的增加没有明显影响，最大平均增幅为9%。然而，观察到刚度增加了34%。此外，延性显著增加，最高可达248%。不过，梁的延性行为发生在加固材料断裂之后。在所有情况下，破坏都归因于木质部件或超高分子量碳纤维增强聚合物（UHM CFRP）板的断裂。数值分析被证明是预测木复合系统刚度的一个有价值的工具，误差幅度相对较低，在几个百分点以内。基于等效截面法的改进方法，可以确定加固梁的双线性荷载-挠度关系。上述曲线反映了实际行为。鉴于加固材料有突然断裂的倾向，建议对承受较低应力水平的梁采用上述加固方法。
