【正文】 莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 The stress resultants N, V and M will be assumed to be positive when they act in the directions shown in (b). This sign convention is only useful, however, when we are discussing the equilibrium of the lefthand part of the beam. If the righthand part of the beam is considered, we will find that the stress resultants have the same magnitudes, but opposite directions[see (c)]. Therefore, we must recognize that the algebraic sign of a stress resultant does not depend upon its direction in space, such as to the left or to the right, but rather it depends upon its direction with respect to the material against which it acts. To illustrate this fact, the sign conventions for N, V and M are repeated in , where the stress resultants are shown acting on an element of the 裝控 091 專業(yè)英語翻譯 uni t 1Static Analysis of BeamsA bar that i s ubj ect ed to f orces act ing trasverse to its axis i s caled a beam. In this section we Wil consi der only a f ew of the simpl est types of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 We see that a positive axial force is directed away from the surface upon which it acts (tension), a positive shear force acts clockwise about the surface upon which it acts, and a positive bending moment is one that presses the upper part of the 裝控 091 專業(yè)英語翻譯 unit 1St atic Anal ysi s of BeamsA bar t hat issubjected to for ces acting tr asver se t o i ts axis iscal led a beam. In t his section we Wi l consider only a few of the simplest ypes of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 Example 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 uni t 1Staic Analysis of BeamsA bar that i s ubjected t o f orces act ing trasverse to its axis i s caled a beam. In this ect ion we Wil consi der only a few of the simpl est types of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 A simple beam AB carries two loads, a concentrated force P and a couple Mo,acting as shown in (a). Find the shear force and bending moment in the beam at cross sections located as follows: (a) a small distance to the left of the middle of the beam and (b) a small distance to the right of the middle of the 英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1Staic Analysis of BeamsA bar that is subjected t o f orces acti ng trasverse to its axis i s caled a beam. In this ect ion we Wil consi der only a few of t he simpl est types of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬 阻便兌扔雜減綻醚蛆馱虛掃 Solution 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 uni t 1Static Analysis of BeamsA bar that is ubj ect ed to f orces act ing trasverse to its axis is cal ed a beam. I n this section we Wil l consider only a f ew of the simplest types of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇 嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 The first step in the analysis of this beam is to find the reactions RAand RB. Taking moments about ends A and B gives two equations of equilibrium, from which we find 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1Static Analysis of BeamsA bar that is ubjected to for ces acting tr asverse to it s axis is cal ed a beam. I n t his section we Wil l consider only a f ew of the simplest ypes of beam s, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡 泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 LMoPR A ?? 43 LMoPRB ?? 4 Next, the beam is cut at a cross section just to the left of the middle, and a freebody diagram is drawn of either half of the beam. In this example we choose the lefthand half of the beam, and the corresponding diagram is shown in (b). The force P and the reaction RA appear in this diagram, as also do the unknown shear force V and bending moment M, both of which are shown in their positive directions. The couple Mo does not appear in the figure because the beam is cut to the left of the point where Mo is applied. A summation of forces in the vertical direction gives 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1Stai c Analysis of BeamsA bar that isubjected to for ces acting tr asverse t o it s axis iscal ed a beam. I n t his section we Wi l consider only a few of the simplest ypes of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 LMoPPV R A ????? 4 which shows that the shear force is negative。注意假如計(jì)算如上那么計(jì)算過程中的驗(yàn)證是有效的。但是如果有更多的反應(yīng)力存在支撐結(jié)構(gòu)中，問題成了靜不定。由于 B 端滾動(dòng)，其他在只可能在垂直作用力上。大部分情況下，這種制約對(duì)橫梁的效果很小，可以被忽略。 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1St ati c Anal ysi s of BeamsA bar t hat issubjected to forces acting t rasver se to i ts axis is cal led a beam. Inthis secti on we Wil consider onl y a few of the simplest ypes of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 之前的例子說明了靜定橫梁的作用效果可以通過方程計(jì)算靜不定的橫梁作用效果需要考慮到橫梁的形變效果，此處這種研究方法教材以后會(huì)討論。 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1Staic Analysis of BeamsA bar that is subjected t o forces acti ng trasverse toits axi s i caled a beam. In this ect ion we Wil consi der only a few of t he simplest types of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌 甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 例 中的橫梁是靜定的，因?yàn)樗械牧Χ伎梢酝ㄟ^平衡方程求出。 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1St atic Anal ysi s of BeamsA bar t hat issubjected to for ces acting tr asver se t o it s axis iscal led a beam. In t his section we Wi l consider only a few of the simplest ypes of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔 雜減綻醚蛆馱虛掃 圖 b 中的一端固定，一端自由運(yùn)動(dòng)的橫梁，稱為懸臂支撐橫梁，固定 端 懸臂支撐不能旋轉(zhuǎn)和轉(zhuǎn)化 ，但是自由端可以。假設(shè)每一個(gè)橫梁都有水平面對(duì)稱，和自身的線平行對(duì)稱，因此，橫梁的橫截面又垂直的對(duì)稱性。 裝控 091 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 uni t 1Static Analysis of BeamsA bar that i s ubj ect ed to f orces act ing trasverse to its axis i s caled a beam. In this section we Wil l consi der only a f ew of the simpl est types of beams, 遮名型苗臥淑繁鎢詐敞步剩岸馳封肇嬌甥邵尖顆歡泌重塌淀仇奮炙肇礦痞掃莉彭摯嚇訴叭牌合斬偏夢(mèng)怠妝算佳卸惹琺彬阻便兌扔雜減綻醚蛆馱虛掃 專業(yè)英語翻譯 unit 1 過程裝備與控制工程課后材料專業(yè)英語翻譯 裝控 091 專業(yè)英語翻譯 unit 1Stai c Analysis of BeamsA bar that i