推荐回答(4个)
作为一名又土又木的工程师,在实际工作中,有时候要对软件(midas、
sap2000、pkpm的计算结果有个判断)就要对结构的弯矩和剪力图有个大概的判断。下面总结了各种结构弯矩图的绘制及图例:
一、 方法步骤
1、确定支反力的大小和方向(一般情况心算即可计算出支反力)
●悬臂式刚架不必先求支反力;
●简支式刚架取整体为分离体求反力;
●求三铰式刚架的水平反力以中间铰C的某一边为分离体;
●对于主从结构的复杂式刚架,注意“先从后主”的计算顺序;
●对于复杂的组合结构,注意寻找求出支反力的突破口。
2、对于悬臂式刚架,从自由端开始,按照分段叠加法,逐段求作M图(M图画在受拉一侧);对于其它形式的刚架,从支座端开始,按照分段叠加法,逐段求作M图(M图画在受拉一侧)。
二、 观察检验M图的正确性
1、观察各个关键点和梁段的M图特点是否相符
●铰心的弯矩一定为零;
●集中力偶作用点的弯矩有突变,突变值与集中力偶相等;
●集中力作用点的弯矩有折角;
●均布荷载作用段的M图是抛物线,其凹凸方向与荷载方向要符合“弓箭法则”;
2、结构中的链杆(二力杆)没有弯矩;
3、结构中所有结点的杆端弯矩必须符合平衡特点。
各种结构弯矩图例如下:
word 弯矩图的画法及具体步骤如下,以WPS2019中的WORD为例做演示。
1、在电脑wps中打开需要操作的word文档,如下图所示。
2、将鼠标放在需要画弯矩图的位置,在文档上方菜单选项栏中选择插入选项栏中的“形状”点击进入下一页面,如下图所示。
3、在弹出的设置选项对话框中选择“星与旗帜”中的需要的弯矩形,点击进入下一步,如下图所示。
4、当鼠标在文档上呈现十字花型时就可以画弯矩形了,如下图所示,是画好的弯矩形,就完成了在WORD中画弯矩形的全部操作。
弯矩图绘制方法
1、基本方法: 采用“截面法”,运用静力平衡方程式 (ΣX=0、ΣY=0、ΣM=0等)求解控制截面的内力(弯矩、剪力)。控制截面的内力求解后再勾绘弯矩图。
1)确定内力符号的规律为:“左上剪力正、左顺弯矩正”;“右下剪力正、右逆弯矩正”。
2)确定内力数值的规律为:剪力Q等于截面任意一侧所有外力沿梁轴垂直方向所作投影的代数和;弯矩M等于截面任意一侧所有外力对该截面形心的力矩的代数和。
2、勾绘弯矩图时线型处理:
除构件受“均布荷载”作用、其弯矩图是曲线外,其余均为直线。
3、弯矩图所画位置:
1)正弯矩画在杆件的下方,负弯矩画在杆件的上方。
2)使杆件下部受拉的弯矩为正,上部受拉的弯矩为负。
3)弯矩图画在杆件纤维受拉的一侧。
4、剪力图所画位置:
1)正剪力画在杆件的上方;
2)负剪力画在杆件的下方;
3)使杆件截面顺时针方向转动的剪力为正剪力;
4)使杆件截面逆时针方向转动的剪力为负剪力;
5)一般情况下,剪力与杆件所受外力的方向相反。
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