应县木塔斗栱模型试验研究

Experimental research on bracket set models of Yingxian Timber Pagoda

以应县木塔中的代表性斗栱为研究对象,采用实体模型试验方法,确定斗栱传递荷载的机理和抵抗变形的特性,提供适用于构建斗栱简化模型的力学参数。试验研究选取三种典型斗栱:柱头铺作、补间铺作和转角铺作,按照1∶3的比例制作成模型;通过竖向荷载试验,得到斗栱的竖向荷载-竖向变形曲线和材料开裂前的抗压刚度;进行了竖向荷载作用下的水平低周反复荷载试验,得到斗栱在竖向荷载和水平低周反复荷载共同作用下的荷载-水平位移曲线和骨架曲线,确定斗栱侧向变形的特征和耗散能量的能力。研究结果表明:斗栱的竖向抗压刚度取决于沿轴心连接构件的承压面积以及材料的弹性模量,其失效特征主要为栌斗在剪压状态下的竖向劈裂;斗栱在水平反复荷载作用下的失效特征表现为泥道栱薄弱内槽面的水平劈裂,斗栱的抗侧移刚度随着竖向荷载的增加而增加,摩擦剪切耗能是斗栱耗散能量的主要方式。

This research selected the representative bracket sets（Dougong） of Yingxian Timber Pagoda as the investigating object and adopted physical model testing method to examine the load transferring mechanism and deformation characteristic of the bracket sets.Appropriate mechanical parameters for the construction of the simplified bracket model were proposed.In this experimental research,three typical bracket sets at the key positions of the pagoda,which were the bracket set on column,bracket set between columns,and bracket set at corner,were made into the archetypal models by the scale of 1∶3.By means of vertical loading test,the N-ΔV curve and compress stiffness of the bracket sets before split of the timber were obtained.Furthermore,horizontal low cyclic loading tests under the vertical loading action were carried out to obtain the N-P-ΔH curve and skeleton curve of the bracket sets,and to study the lateral displacement characteristic and energy dissipation capability of the bracket sets.The research results indicated that the vertical compressive stiffness of the bracket sets depends on the bearing area and elasticity modulus of members located on central axis.The main failure pattern is the vertical split of cap block under shear and compression.The horizontal split at the weak internal groove of axial bracket arm is the failure pattern of the bracket set under horizontal cyclic loading.The lateral displacement stiffness is increased along with the vertical load increases.The friction and shear of interfaces between members is a primary means to energy dissipation of the bracket set.