刚性梁由圆杆悬挂在点,如图, ,已知杆的横截面积,许用应力,试(1)校核杆的强度;(2)结构的许用载荷。

<p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋体;mso-ascii-font-family:'Times New Roman';mso-hansi-font-family:'Times New Roman';mso-bidi-font-family:'Times New Roman';font-size:10.5000pt;mso-font-kerning:1.0000pt;"><font face="宋体">刚性梁</font></span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1545184633423ea40e3261cba47a9b4b12bb1dc8d185e.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">的受力图如下（</font></span><span style="font-family: 宋体; font-size: 10.5pt;">3</span><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">分）：（</font></span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1545184643776025a493f34704a688c2cc35ac5fc57ec.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">表示</font></span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15451846528020612915046c54a0fb9072f704e3e7f66.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;">杆的轴力）</span></p><p class="MsoNormal" align="center" style="text-autospace:ideograph-numeric;mso-pagination:none;text-align:center;"><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15451846604666752a1bf51c5445aa9e024439a9d63e7.png" alt="上传图片"><span style="mso-spacerun:'yes';font-family:宋体;mso-ascii-font-family:'Times New Roman';mso-hansi-font-family:'Times New Roman';mso-bidi-font-family:'Times New Roman';font-size:10.5000pt;mso-font-kerning:1.0000pt;"><o:p>&nbsp;</o:p></span></p><p class="MsoNormal"><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1545184669506f2d683ea549e46f2819908b2429f1500.png" alt="上传图片"><span style="mso-spacerun:'yes';font-family:宋体;mso-ascii-font-family:'Times New Roman';mso-hansi-font-family:'Times New Roman';mso-bidi-font-family:'Times New Roman';font-size:10.5000pt;mso-font-kerning:1.0000pt;"><font face="宋体">（</font>2<font face="宋体">分）</font></span><span style="mso-spacerun:'yes';font-family:宋体;mso-ascii-font-family:'Times New Roman';mso-hansi-font-family:'Times New Roman';mso-bidi-font-family:'Times New Roman';font-size:10.5000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p><p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋体;mso-ascii-font-family:'Times New Roman';mso-hansi-font-family:'Times New Roman';mso-bidi-font-family:'Times New Roman';font-size:10.5000pt;mso-font-kerning:1.0000pt;">(1)&nbsp;</span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1545184691591e6fe9a91062a4dbaa5c5b2be897bf290.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">杆应力</font></span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/154518468156460f1c26bd145487281c80574160c0395.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">；</font></span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15451847008407ac20293021e41d38828e0a5baa7c404.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">，</font></span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15451847104997c7a49daf93f4fe7b2e9d075df40a563.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">杆强度够。</font> <font face="宋体">（</font></span><span style="font-family: 宋体; font-size: 10.5pt;">3</span><span style="font-family: 宋体; font-size: 10.5pt;"><font face="宋体">分）</font></span></p><p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋体;mso-ascii-font-family:'Times New Roman';mso-hansi-font-family:'Times New Roman';mso-bidi-font-family:'Times New Roman';font-size:10.5000pt;mso-font-kerning:1.0000pt;">(2)</span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15451847188055200a00309e140f8b532b992154f2307.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;">&nbsp;&nbsp;</span><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/154518472727169f86964d7c34397bc7848594af2a343.png" alt="上传图片"><span style="font-family: 宋体; font-size: 10.5pt;">&nbsp;</span><font face="宋体" style="font-family: 宋体; font-size: 10.5pt;">（</font><span style="font-family: 宋体; font-size: 10.5pt;">2</span><font face="宋体" style="font-family: 宋体; font-size: 10.5pt;">分）</font></p>