桁式钢拱架在AutoCAD中的自动化绘制方法

Automatic Drawing Method of Truss Steel Arch Centering in AutoCAD

为提高钢拱架的设计效率,针对桁式钢拱架构造设计,先计算出包含施工预拱度的拱圈拱腹坐标,后根据混凝土拱腹与拱架下弦杆中心之间的距离,计算出钢拱架下弦中心线的坐标和长度,据此求出标准段数量和拱顶非标准段长度,再以标准段下弦杆销轴中心长度为半径,运用几何方法求出各标准段与钢拱架下弦中心线的交点,得到各标准段销轴中心坐标及在Auto CAD中的插入点坐标和旋转角,将该算法编制在钢拱架设计程序中。为实现钢拱架在Auto CAD中的自动化绘制,将拱脚段和标准段事先定义为块,基于Active X Automation技术的VBA程序语言编制了钢拱架自动绘制程序。通过对不同跨径与矢高混凝土拱桥的钢拱架试设计,结果表明,利用开发的2个程序均实现了钢拱架的设计与制图,为钢拱架的快速设计创造了条件,本文方法也可为其他类型钢拱架设计提供参考。

To improve the design efficiency of steel arch centering,aiming at the truss steel arch centering structure,the arch ring soffit coordinates including construction camber were firstly calculated,then the coordinates and length of the center line of the lower chord of the steel arch centering were gained according to the distance between the concrete soffit and the center of the lower chord of the arch centering,Finally,the number of standard segments and the length of non-standard segments of the arch crown were solved.Taking the pin center length of the lower chord of the standard segment as the radius,the intersection point between each standard segment and the center line of the lower chord of the steel arch centering was calculated by using the geometric method,and the pin center coordinates of each standard segment,the insertion point coordinates and rotation angle in AutoCAD were obtained.The algorithm was compiled in design program of the steel arch centering.In order to realize the automatic drawing of steel arch centering in AutoCAD,both springing segment and standard segments were defined as blocks in advance,and the automatic drawing program of steel arch centering was compiled based on VBA of ActiveX Automation Technology.Trial design of steel arch centering of concrete arch bridge with different span and rise was performed.The results show that the design and drawing of steel arch centering has been realized by using the two developed programs successively,which creates conditions for the rapid design of steel arch centering.The method could also provide reference as the design for other types of steel arch centering.