【正文】 38．同一結構選不同的力法基本體 系，所得到的力法方程代表的位移條件相同。 （ ） 設直桿的軸向變形不計，圖示體系的動力自由度為 4。（ ） 超靜定次數一般不等于多余約束的個數。 A、 1 B、 0 C、 1/2 D、 1 專業(yè)好文檔 2 1如下圖所示，若要增大其自然振頻率 w 值，可以采取的措施是（ B ）。 A、 ij? 恒大于零 B、 ii? 恒大于零 C、 ji? 恒大于零 D、 ip? 恒大于零 位移法典型方程實質上是（ A ）。 l。（ ） 靜定結構和超靜定結構的內力影響線均為折線組成。（ ） B 圖 a 圖 b 專業(yè)好文檔 11 2圖示為剛架的虛設力系，按此力系及位移計算公式可求出桿 AC 的轉角。 26 lEIEA? 。 EI=常數 。 用位移法計算圖 26 示結構，并做彎矩圖。 專業(yè)好文檔 45 判斷所示體系的動力自由度。d miss this. 專業(yè)好文檔 48 If we don39。ll be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end. Skydiver preps for the big jump When he jumps, he is expected to reach the speed of sound 690 mph (1,110 kph) in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him pletely. If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes it39。s like the set for a Gee Lucas movie floating to the edge of space. You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space live. The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch. I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith the feeling of pushing the envelope into uncharted territory. The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40 acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over. How claustrophobia almost grounded supersonic skydiver With each twist, you could see the wrinkles of disappointment on the face of the current record holder and cap (capsule munications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted. The supersonic descent could happen as early as Sunday. The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule 專業(yè)好文檔 47 attached, will move through the lower level of the atmosphere (the troposphere) where our daytoday weather lives. It will climb higher than the tip of Mount Everest ( miles/ kilometers), drifting even higher than the cruising altitude of mercial airliners ( miles/ kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence. The balloon will slowly drift to the edge of space at 120,000 feet ( miles/ kilometers). Here, Fearless Felix will unclip. He will roll back the door. Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform. Below, the Earth bees the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, he39。 專業(yè)好文檔 40 解： 只有一個結點角位移，基本結構如圖所示 列位移法方程 01111 ??? pFk 圖作 p，MM1 求 11k 、 pF1 ，并求 1? 專業(yè)好文檔 41 ik 711? 4251 ??pF i28251 ?? 作 M 圖 PMMM ??? 11 ，畫 M 圖 。 1） 如圖 14 所示，繪彎矩圖。 解： 二次超靜定，基本結構如圖： 列力法方程 ????? ???? ???? 0022221211212111pp???? ???? 圖作 p，MM，M 21 專業(yè)好文檔 23 求 11? 、 12? 、 22? 、 21? 、 p1? 、 p2? EIEI 366323621111 ???????? EIEI 10 86662112112 ??????? ?? EIEI 28866646621122 ??????? ???????? EIEIP 45023602133602111 ???????? ?????????? EIEIP 54 063602112 ???????? ?????? 求得144572521?????? 作 M 圖 pMxMxMM ??? 2211 專業(yè)好文檔 24 方程 。（ ） 力法計算舉例 專業(yè)好文檔 14 圖示為力法基本體系，求力法方程中的系數 ?11 和自由。（ √ ） 2支座移動對超靜定結構的極限荷載沒有影響。（ ）