应县木塔结构变形现状及分析

Present Structural Deformations and Analysis of Yingxian Wooden Pagoda

为了解应县木塔的构件变形和整体变形现状,对其圆柱的柱头和柱脚坐标、阑额和乳栿的挠度、楼板的相对高程进行了现场测量和分析,得到了圆柱倾斜水平投影值和柱脚高程、内外槽高差、阑额和乳栿的挠曲程度和整体变形等几何参数和力学特征。结果表明:在构件变形层面,应县木塔二层明层和三层的圆柱倾斜最严重,四层平坐层和五层平坐层外槽南侧、西南侧和北侧的圆柱倾斜水平投影值较大,木塔向东北向的倾斜仍在加剧;柱脚呈现出南高北低的规律,内、外槽高差从二层明层往上依次减小;除四层明层和五层明层外,其他各层均有25%～35%的阑额挠度过大,需要进行替换或加固,乳栿挠度相对较小;木塔的整体变形在东西向和南北向存在显著差异,从二层平坐层至五层明层,东西向各层中心偏移值先增大后减小,南北向各层中心偏移值逐层递增;二层明层到三层明层外槽柱向东的中心偏移量占木塔在该方向整体倾斜偏移量的75%,二层明层外槽柱向北的层位移占木塔在该方向整体倾斜偏移量的42%,各层中心偏移方向也存在差异。

In order to acquire the present deformations of components and overall Yingxian Wooden Pagoda,the coordinate values of heads and bases of columns,deflections of architraves and beam ties and relative elevations of floors were measured,and the geometric parameters and mechanical characteristics including horizontal projection values of the oblique columns,elevations of column bases,altitude difference between the inside and outside,distributions of architraves’and beam ties’deflections and overall deformation were obtained.The results show that as for component deformations,the timber columns’inclinations in the second bright floor and the third floor are the most severe in the Yingxian Wooden Pagoda,and the external columns’inclinations on the south,southwest,and north sides in the fourth dark floor and the fifth dark floor are more serious than other corresponding columns in all dark floors.The tower’s inclination to the northeast is still aggravating.Column bases are higher in the south and lower in the north.Altitude difference between the inside and outside becomes larger from the second bright floor.Except for the fourth bright floor and fifth bright floor,25%-35% of architraves in each floor have large deflections,which need reinforcement,while beam ties’deflections aresmall.There is a significant discrepancy in the overall deformation of the wooden pagoda between the east-west and the north-south directions.From the second dark floor to the fifth bright floor,the center deviation values in the east-west direction firstly increase and then decrease,while those in the north-south direction rise floor by floor.The eastward center deviation value of the external columns from the second bright floor to the third bright floor accounts for 75% of the overall deviation value of the tower in this direction,and the northward value of the second bright floor is 42%in the direction.There are also different center azimuth angles of each floor.