现举一例如下 ,试论“特殊情况下简支梁的绝对最大弯矩”问题。求跨长为 2 0米的简支梁在图示移动荷载作用下的绝对最大弯矩 (见图 1 )。图 1　　先按一般情况求解 :显然 ,使跨中截面产生最大弯矩的临界荷载 P2 =80 KN,移动荷载组使 P2 与梁上荷载的合力 R对称于跨中 (见图 2 ) Here is an example to discuss the “absolute maximum moment of simply supported beam under special circumstances” problem. Find the absolute maximum bending moment of a simply supported beam with a length of 20 meters at the moving load (see Figure 1). Obviously, the critical load P2 = 80 KN that produces the maximum bending moment in the mid-section, the moving load group makes the resultant force R of the load P2 and the beam symmetrical in the middle span (see Figure 2)