结构力学第六章-2[力法举例].ppt

§6-4 力法解超静定结构 (1) 确定结构的超静定次数和基本结构(体系) (2) 建立力法典型方程 (7) 根据叠加原理作超静定结构的内力图 (8) 对计算结果进行校核 力法的解题步骤如下: Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例 1. 求解图示两端固支梁。 解：取简支梁为基本体系 力法典型方程为： EI Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 两端固支梁在竖向荷载作用下没有水平反力 典型方程改写为 图乘求得位移系数为 代入并求解可得 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. EA为常数 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 各杆最后内力由 叠加法得到： 由计算知，在荷载作用下，超静定桁架的内力与杆件的绝对刚度EA无关，只与各杆刚度比值有关。 问题：若用拆除上弦杆的静定结构作为基本结构，本题应如何考虑？ 问题?在荷载作用下，超静定桁架的内力与杆件的绝对刚度EA关系是什么? Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 解： 自乘求δ11 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 解：选取基本体系 建立典型方程 EI常数 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 弯矩图为： 进一步求D点竖向位移 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 解：取基本体系如图(b) Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 有无下部链杆时梁内最大弯矩之比： Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.