【正文】 ，但很快受壓區(qū)混凝土達 到極限壓應(yīng)變，承載力急劇下降而破壞 )。 5．鋼筋混凝土梁的斜拉破壞一般發(fā)生在 (剪跨比較大且箍筋數(shù)量較少時 )。 (√) 4．鋼筋混凝土少筋梁的破壞是始于受拉區(qū)，故其破壞形式屬于脆性破壞。 (x) 6．箍筋，般采用 HPB235， HRB335級鋼筋，其形式有封閉式 和開口式兩種。 ( ) 3．鋼筋混凝土梁的混凝土保護層厚度是指箍筋外表面到梁表面的距離。 ( ) 10．鋼結(jié)構(gòu)對鋼材的性能要求包括：強度、塑性、韌性、冷彎性能、耐久性和可焊性。 ( √ ) 6．斜截面抗剪基本公式是半經(jīng)驗半理論公式，使用時必須采用規(guī)定單 位的數(shù)值。 ( √ ) 1 ( ) 4公式的 限 制條件 是為了防止發(fā)生斜拉破壞。 ( ) 4．鋼結(jié)構(gòu)可換性強，因此易于維修養(yǎng)護。 ( √ ) 三、簡答題（每小題 5分，共 25分） 1．影響砌體抗壓強度的因素有哪些？ 答： (1)塊材強度； (2)砂漿的物理力學(xué)性能； (3)砌縫厚度； (4)塊材的尺寸與形狀。 4．什么是后張法？在后張法構(gòu)件配筋上有什么特點？ 答：后張法是先澆筑構(gòu)件混凝土，待混凝土結(jié)硬后，再在梁體上張拉并錨固預(yù)應(yīng)力筋束的方法。 (2)超筋梁破壞；混凝土先被壓碎，鋼筋不屈服，屬脆性破壞。由塊材 (石材、預(yù)制塊 )和膠結(jié)材料 (砂漿 )按一定的砌筑規(guī)則組成的受力整體稱為砌體結(jié)構(gòu)。由于該現(xiàn)象的影響，卸載后，鋼筋受壓而混凝土受拉，因此，當(dāng)配有較多數(shù)量的縱向鋼筋時，可能導(dǎo)致混凝土拉應(yīng)力過大而開裂，所以，鋼筋混凝土受壓柱中不應(yīng)采用過大的配筋率。梁截面會產(chǎn)生較大的塑性變形，因而有明顯的破壞預(yù)兆，屬于塑性破壞。 斜拉破壞特征：破壞過程急速且突然，彎曲裂縫一旦出現(xiàn)，就迅速向受壓區(qū)斜向伸展，直至荷載板邊緣，使混凝土裂通，梁被撕裂成兩部分，而喪失承載能力。 4．軸心受壓構(gòu)件的截面破壞特點是什么 (分短柱和長柱 )?答：對配有中等強度鋼筋 (1～ Ⅱ 級 )的短柱在破壞時，總是縱向鋼筋先達到 屈服點，繼而混凝土達到最大壓力破壞。 (3)縱筋配筋率口：梁的抗剪能力，隨縱向配筋率的增大而提高。 1．簡述影響鋼筋混凝土受彎構(gòu)件斜截面強度的主要因素有哪些 ?這些因素是怎樣影響 (1)剪跨比 m：隨著剪跨比 m的增加，梁的破壞形態(tài)按斜壓 (m1)、剪壓 (1m3)和斜拉 (m3)的順序演變，而抗剪承載力逐步降低。因此，砌體結(jié)構(gòu)以承受壓力為主。s long history of fine ceramics lures followers from across the world, report Peng Yining and Hu Kaiyong in Jingdezhen, Jiangxi province. Dressed in paintstained coveralls, China De La Vega easily navigated the maze of alleyways running alongside a ceramics factory in Jingdezhen, Jiangxi province. The 31yearold Australian potter and painter wound her way through armies of onemeterhigh ceramic Buddhas and piles of porcelain shards while nodding greetings to the workers and residents. She said the locals are used to seeing foreigners in Jingdezhen, China39。s cooperation with Central Asian countries, a senior official said. Shaanxi Governor Lou Qinjian said the province is fresh, rich and unique, as it was when it anchored one end of the ancient Silk Road. It is the best option for acmodating industrial transfers from East China or the w orld at large, he said on Wednesday in Xi39。an, the starting point of the ancient Silk Road, a trade channel established more than 2,000 years ago linking China, Central Asia and Europe. The pursuit of beauty is a mon goal for most women, whether they live in the modern world today or in the modest times of the past. The pursuit of beauty is also a lifelong journey, something that demands pe rseverance and mitment. Summer is here, and so are the hot temperatures, humid air and harmful UV rays. Most Chinese women perfer fairer plexions, which means they have to do more work to stay beautiful during the hottest time of the year. However, without SPF50 sunscreens and air conditioned rooms, how did women in ancient China cope with the heat and remain beautyconscious? In this article, you39。s 72hour visafree policy has attracted wide attention from both Chinese and foreign experts and businessmen since it took effect on Sept 1 last year. The program permits citizens from 51 countries and regions including the United States, Australia, Canada and Japan who have valid visas and flight tickets to a third country to spend three days in the city. The capital of Sichuan province is the first city in the western region of China to offer foreign tourists a threeday visa and the fourth nationwide to adopt the policy following Shanghai, Beijing and Guangzhou. Li Zhiyong, deputy dean of the tourism institute at Sichuan University, said the move contributes to a large increase in the number of overseas tourists and raises the city39。s 39。 (3)縱筋配筋率弘：梁的抗剪能力，隨縱向配筋率的增大而提高。與箍筋強度 R非的乘積越大，則梁抗剪能力越強。 對長柱，其破壞是由于構(gòu)件喪失縱向穩(wěn)定所造成。斜壓破壞特征：首先混凝土在加載點與支座間被斜裂縫分割成若干個斜向短柱，當(dāng)混凝土中的 壓應(yīng)力超過其抗壓強度時，混凝土即被壓壞。超筋梁的破壞無明顯的預(yù)兆，屬于脆性破壞。先張法的特點是所用的預(yù)應(yīng)力筋束，一般用高強鋼絲、鋼 絞線，自錨型 (通過預(yù)應(yīng)力筋與混凝土粘結(jié)力實現(xiàn)錨固 )，不專設(shè)永久錨具。例如拱橋的主拱圈、橋梁的墩臺及基礎(chǔ)、擋土墻、涵洞及隧道的襯砌與洞門建筑等。 3．在什么情況下采用雙筋梁 ?答：采用雙筋梁的情況：當(dāng)構(gòu)件承擔(dān)的 彎矩過大，而截面尺寸受建筑凈空限制不能增大，混凝土強度等級也不宜再提高，采用單筋截面將無法滿足 2≤ 氕 _71。預(yù)應(yīng)力筋通常采用曲線配筋，不同截面的預(yù)加力作用點隨使用荷載彎矩的變化而調(diào)整，因而，后張法適用于大跨徑受彎構(gòu)件。這三種形態(tài)，在設(shè)計中都應(yīng)避免。