古建筑墙体木柱缺陷对其安全性影响数值模拟研究

Numerical simulation on the influence of wall wood column defects on the safety of ancient building

【目的】墙体木柱作为木结构古建筑最重要的承重构件之一,容易出现裂纹、腐朽等缺陷,而各类缺陷会影响墙体木柱顺纹压应力的分布,导致其承载力降低,进而影响其安全性,直接威胁整个建筑的稳定性。因此,研究不同类型的缺陷对古建筑墙体木柱安全性影响是很有必要的。【方法】首先建立了墙体木柱裂纹缺陷、腐朽缺陷以及复合缺陷几何模型,并定义了墙体木柱的受压安全性系数k_(c),然后使用Abaqus有限元软件分别模拟分析了裂纹缺陷模型、单侧腐朽缺陷模型、环形腐朽缺陷模型和复合缺陷模型最大顺纹压应力的大小和位置,探究了不同尺寸的缺陷对墙体木柱安全性的影响,并进行了实例验证。【结果】单侧腐朽缺陷以及复合缺陷会使墙体木柱在径向上出现较大偏移,对木柱的稳定性产生较大影响,而裂纹缺陷和环形腐朽缺陷在径向、顺纹方向和切向上偏移较小;裂纹缺陷、单侧腐朽缺陷、环形腐朽缺陷和复合缺陷都对墙体木柱最大顺纹压应力和安全性有较大影响,最大顺纹压应力总是出现在有效截面面积最小处,且均随各缺陷程度的增大呈指数增加,而安全性系数呈指数下降,同时复合缺陷对墙体木柱安全性的影响要大于单一缺陷对墙体木柱的安全性影响。半露明柱与暗柱在腐朽深度相同时,安全性相差不大,在腐朽面积相同时,半露明柱的安全性要远低于暗柱。【结论】裂纹缺陷和腐朽缺陷会降低墙体木柱的安全性,而有限元数值模拟能够计算出墙体木柱的顺纹压应力最大值,进而量化墙体木柱的安全性,其结果可以为墙体木柱的修缮提供依据。

[Objective]As one of the most important load-bearing components of wooden structure ancient buildings,the wall wood columns are prone to occur the defects such as cracks and decay.All kinds of defects will affect the distribution of longitudinal compressive stress of wall wood columns,leading to a reduction in its bearing capacity,which then affects its safety and directly threatens the stability of the whole building.Therefore,it is necessary to study the influence of different types of defects on the safety of wall wood columns of ancient buildings.[Method]Firstly,in this paper,the geometric models of wall wood columns with crack,decay defects and composite defects were established,and the compression safety factor k_(c) of wall wood column was defined.Then,the magnitude and location of the maximum longitudinal compressive stress were simulated and analyzed using Abaqus finite element software for the crack defect model,the unilateral decay defect model,the ring decay defect model and the composite defect model,respectively.The influence of defects of different sizes on the safety of wall wood columns was investigated and verified by an example.[Result]The unilateral decay defects and composite defects caused large deflections in the radial direction of the wall wood columns,which had a greater influence on the stability of wood columns,while wall wood columns with crack defects and ring decay defects had smaller deflections in the radial direction,longitudinal direction and tangent direction.Crack defects,unilateral decay defects,ring decay defects and composite defects had a significant influence on the maximum longitudinal compressive stress and the safety of wall wood columns.The maximum longitudinal compressive stress always occurred at the minimum effective sectional area.The longitudinal compressive stress in wall wood columns increased exponentially with the increase of defect degree and the safety factor decreased exponentially with the increase of defect degree,while the impact of composite defects on the safety of wall wood columns was greater than that of a single defect on the wall wood column safety impact.The difference in safety between semi-exposed columns and concealed columns was not much when the decay depth was same,and the safety of semi-exposed columns was much lower than that of concealed columns when the decay area was same.[Conclusion]The crack defects and decay defects can reduce the safety of wall wood columns,and the finite element numerical simulation can calculate the maximum longitudinal compressive stress of wall wood columns,and then quantify the safety of wall wood columns,and the results can provide a basis for the repair of wall wood columns.