无黏结预应力胶合木T梁受弯性能

Bending Performance of Unbonded Prestressed Gulam T Beam

胶合木梁刚度小、承载力低且易发生脆性受拉破坏,为了改善其短期受弯性能,提出了一种胶合木T梁和无黏结预应力相结合的新型构件。通过对4根落叶松胶合木T梁的四点弯曲试验,包括1组未增强试件和1组无黏结预应力筋增强试件,对比分析了两组试件的破坏形态和破坏机理,探讨了无黏结预应力对其受弯性能的影响。结果表明:施加0.25fptk(fptk为钢绞线抗拉强度标准值)预应力后,胶合木T梁未产生受拉破坏,而为腹板剪切破坏;相比未增强试件,无黏结预应力筋增强试件的受弯极限承载力提高了38.2%,抗弯刚度提高了22.5%,延性提高了45.8%;施加预应力还能有效减小木材缺陷对胶合木梁受弯性能的影响。

The glulam beam has characteristics of small stiffness,low bearing capacity,and prone to brittle tensile failure.To improve the short-term bending performance of glulam beams,a new type of component combining glulam T beam and unbonded prestress was proposed in this paper.Through the four-point bending tests of four larch glulam T-beams,covering one group of unreinforced specimens and one group of unbonded prestressed rib-reinforced specimens,the failure morphology and failure mechanism of the two were achieved and analyzed.Besides,the influence of unbonded prestress on their flexural performance was discussed.The test results show that after applying 0.25%fptk(fptk is the standard value of tensile strength for steel strands)prestress,the glulam T beam presents web shear failure instead of tensile failure.Compared with the unreinforced specimens,the bending ultimate bearing capacity of the unbonded prestressed rib-reinforced specimens was increased by 38.2%,the bending stiffness was increased by about 22.5%,and the ductility was increased by 45.8%.In addition,the application of prestress can effectively reduce the wood defects'impacts on the bending performance of glulam beams.