【正文】 s game by recognizing it as an Olympic event in 1976. Again, television coverage of the Olympics has been exceptionally important in drawing attention to interna。s game changed radically in 1971 when separate rules for women were modified to more closely resemble the men39。 its construction and size of 30 in (76 cm) were ruled official in 1949. The rulesetters came from several groups early in the 1900s. Colleges and universities established their rules mittees in 1905, the YMCA and the Amateur Athletic Union (AAU) created a set of rules jointly, state militia groups abided by a shared set of rules, and there were two professional sets of rules. A Joint Rules Committee for colleges, the AAU, and the YMCA was created in 1915, and, under the name the National Basketball Committee (NBC) made rules for amateur play until 1979. In that year, the National Federation of State High School Associations began governing the sport at the high school level, and the NCAA Rules Committee assumed rulemaking responsibilities for junior colleges, colleges, and the Armed Forces, with a similar mittee holding jurisdiction over women39。 Australia, China, and India between 1895 and 1900。s original players were Canadians, and the game spread to Canada immediately. It was played in France by 1893。 the ball was the objective. To score, the ball had to be shot through a horizontal, elevated goal. The team with the most points at the end of an allotted time period wins. Early in the history of basketball, the local YMCAs provided the gymnasiums, and membership in the anization grew rapidly. The size of the local gym dictated the number of players。s Christian Association (YMCA), which later became Springfield College. Naismith (18611939) was a physical education teacher who was seeking a team sport with limited physical contact but a lot of running, jumping, shooting, and the handeye coordination required in handling a ball. The peach baskets he hung as goals gave the sport the name of basketball. His students were excited about the game, and Christmas vacation gave them the chance to tell their friends and people at their local YMCAs about the game. The association leaders wrote to Naismith asking for copies of the rules, and they were published in the Triangle, the school newspaper, on January 15,1892. Naismith39。s ball is in (7274 cm) in circumference. The covering of the ball is leather, rubber, position, or synthetic, although leather covers only are dictated by rules for college play, unless the teams agree otherwise. Orange is the regulation color. At all levels of play, the home team provides the ball. Inflation of the ball is based on the height of the ball39。s National Basketball Association (WNBA) playoffs. And it has also made American heroes out of its player and coach legends like Michael Jordan, Larry Bird, Earvin Magic Johnson, Sheryl Swoopes, and other great players. At the heart of the game is the playing space and the equipment. The space is a rectangular, indoor court. The principal pieces of equipment are the two elevated baskets, one at each end (in the long direction) of the court, and the basketball itself. The ball is spherical in shape and is inflated. Basketballs range in size from in (7276 cm) in circumference, and in weight from 1822 oz (510624 g). For players below the high school level, a smaller ball is used, but the ball in men39。0 1900310 mmf AfbhfAysycs ????????? ?NVNVhfSAbhfVdcsyvsvccs144000147378480210200 00?????????????? （三）已知 As′ =1140mm2求 As ? ? ? ? 48025010 2620 039。??? ???????????? bhf ahAfMcsyds?? ???????? s?? ξ ho= 480=186＞ 2a’ 4. 計算 As 選配 5 根直徑 22 受拉鋼筋 21901mmAs ? （二）計算箍筋 mmhhm 4800 ?? ， ???bh m Nbhf c 3 0 0 0 0 0 ????? NVd 1 4 4 0 0 01 2 ???? bhfV cd ?? ，所以截面尺寸滿足抗剪要求 NVNbhfV dcc 1 4 4 0 0 08 4 0 0 04 8 02 5 0 ???????? ? 所以應(yīng)由計算確定箍筋用量 ： 300 ??? ????????? hf bhfVSAyvcdsv ? 查得 mmS 250max ? ，取 mmS 200? 0 04 7 mmA sv ??? 采用雙肢箍筋， svsv naA ? ， n=2， mmnAa svsv ??? 一根直徑 8 的鋼筋面積為 所以選箍筋為 ?8200 239。sA 作已知 代入公式求 ?? ?s )35180()(2620039。 402mmAs ? 3. 因?qū)嵟?39。2039。 2. 令 b??? ， 查得： mma 45?? ，計算 39。 Ф 16Ф 22Ф 22 解答： mmhb 550250 ??? 查得： mma 70? ， mmahh 480705500 ????? 查得：材料強度設(shè)計值 2/10 mmNf c ? ； 2/310 mmNf y ? ； ?b? ； ?sb? 。承受均布荷載，跨中截面承受彎矩設(shè)計值 M=，支座邊緣承受 剪力設(shè)計值 V=120KN；混凝土為 C20，受力鋼筋采用Ⅱ級鋼筋，箍筋采用Ⅰ級鋼筋；結(jié)構(gòu)系數(shù) γ d=。39。s39。 760mmAs ? ， 0e? ， e 同前 1. 由 39。s39。 308mmAs ? 2. 已知 39。 ??? ???????????? ahf bhfNeA y sbcds ?? 39。sA 0)40460(310 )( 23039。 （ 1） 計算縱向受力鋼筋 As′ 、 As 并配筋（選配受力筋的直徑與根數(shù)，箍筋直徑與間距的選用），繪制配筋圖； （ 2） 已配有 2 根直徑 22 的受壓鋼筋， As′ 試計算受拉鋼筋 As 的數(shù)量并配筋。（ 3）繪制截面配筋圖（標(biāo)注截面尺寸、鋼筋直徑、根數(shù)或間距） 。試求：（ 1）縱向受力鋼筋的面積 As。并按構(gòu)造要求配置箍筋，并繪制截面配筋圖（標(biāo)注截面尺寸、鋼筋直徑、根數(shù)或間距）。 有矩形截面一偏心受壓柱，截面尺寸 bh = 400 600mm（一類環(huán)境條件），由延性要求已配 3 根直徑為 14 的受壓鋼筋（ As=462mm2）。 m，取 a=a’ =40mm，采用 C20 混凝土，縱筋為 Ⅱ 級鋼筋，箍筋為Ⅰ級鋼筋。如果該截面已配置 2 根直徑為 20 的受壓鋼筋，試配置該截面的受拉鋼筋（不畫配筋圖） 。截面承受軸向壓力設(shè)計值 N =480KN，彎矩設(shè)計值 M = 。試復(fù)核截面是否安全?？缰薪孛娉惺軓澗卦O(shè)計值 M=， 配有 2 根直徑為 16 的受壓鋼筋。 （ 3）已知 As′ 計算得出ξ＞ξ b 時說明 As′ 配少了，按 As′ 、 As 均未知進行計算； 當(dāng) 2a′ /h0 ＜ ξ ＜ξ b 符合基本公式的適用條件，代入公式： yd39。因二個構(gòu)件的承載能力均由鋼筋達到屈服強度為準(zhǔn)， Nu=Asfy=Apfpy 有腹筋梁的斜截面破壞形 式有那些？應(yīng)該采取什么措施來防止這些破壞？ 預(yù)應(yīng)力混凝土與普通混凝土之間的主要異同點是什么？ 在計算大偏心受壓構(gòu)件截面配筋時： ⑴ 什么情況下要假定ξ =ξ b？為什么？ ⑵ 當(dāng)求得的 As’ ≤ 0或 As ≤ 0 時應(yīng)如何處理？ ⑶ 在已知 As′ 計算得出 ξ＞ξ b ； 2a′ /h0 ＜ ξ ＜ξ b ； ξ ＜ 2a′ /h0 應(yīng)分別如何計算（可 用公式表示）？ （ 1）當(dāng) As′ 、 A 均未知時，二個基本公式三個未知數(shù)，可得到無數(shù)個解，假定ξ =ξ b ，充分利用了混凝土受壓，使鋼筋的總用量最小。為了克服普通鋼筋混凝土結(jié)構(gòu)這一缺點，構(gòu)件在受荷前，先對受拉區(qū)混凝土施加預(yù)應(yīng)力，受拉區(qū)混凝土由荷載產(chǎn)生的拉應(yīng)力先抵消預(yù)壓力，然后受拉，大大提高了混凝土的抗裂能力。 為什么要對混凝土施加預(yù)應(yīng)力？預(yù)應(yīng)力混凝土與普通鋼筋混凝土軸心受拉構(gòu)件二者承載力有何關(guān)系？為什么？ 普通鋼筋混凝土結(jié)構(gòu)的主要缺點是抗裂性能差，混凝土的受拉極限拉應(yīng)變?yōu)? （ ～ ） 103左右，此時鋼筋的拉應(yīng)力只有 20～ 30N/mm2；當(dāng)構(gòu)件要求限制裂縫寬度時，鋼筋的拉應(yīng)力約在 200～ 300N/mm2。 （ 2）彎破鋼筋應(yīng)滿足抗剪強度的 要求及相應(yīng)的構(gòu)造規(guī)定。 什么是梁的抵抗彎矩圖（ MR圖）？縱向鋼筋彎起時有什么要