【正文】 地震帶民用建筑由磚混向框架發(fā)展的必要趨勢 【摘要】 地震是不可避免的自然災(zāi)害，但建筑結(jié)構(gòu)的選擇可以有效的減少它帶來的損失，目前地震帶民用建筑，尤其經(jīng)濟(jì)不發(fā)達(dá)地區(qū)的建 筑結(jié)構(gòu)多為磚混結(jié)構(gòu)，其較差的抗震能力反而助長了地震的威風(fēng)，而框架結(jié)構(gòu)在地震中的優(yōu)勢就顯得尤為明顯，價格雖然高些，但與磚混結(jié)構(gòu) 相比，性價比更高。另一種觀點(diǎn)認(rèn)為，汶川地區(qū)欠發(fā)達(dá)，建筑房屋多以傳統(tǒng)的磚混結(jié)構(gòu)為主，且年久失修，已無法應(yīng)對7 級以上的地震，其實(shí)磚混結(jié)構(gòu)房屋大量倒塌，并造成慘重人員傷亡的現(xiàn)象，早已在 1976 年唐山大地震上出現(xiàn)過。抗壓性能好是其一大優(yōu)點(diǎn)，但其缺點(diǎn)同樣突出：自重大，強(qiáng)度低，使砌體結(jié)構(gòu)承受的地震力也相對增大；砌筑工程繁重，基本采用人工方式砌筑，勞動量大，效率低下；黏土用量大，往往占用農(nóng)田，影響農(nóng)業(yè)生產(chǎn)；由于砌筑砂漿和磚石、砌塊間的粘結(jié)力差，無筋砌體的抗拉、抗彎及抗剪強(qiáng)度低，抗震及抗裂性能差且施工質(zhì)量難控制，很容易對結(jié)構(gòu)破壞，是剛性結(jié)構(gòu)，為此地震多發(fā)區(qū)應(yīng)慎用這種建筑結(jié)構(gòu)。該結(jié)構(gòu)房屋因限于砌體材料本身的特性（延性差），加上結(jié)構(gòu)整體性也比較差，在地震作用下極易出現(xiàn)開裂、破壞甚至倒塌現(xiàn)象。當(dāng)按一級抗震設(shè)計(jì)時，現(xiàn)澆框架混凝土強(qiáng)度等級不宜低于 c30；按二 ~四級設(shè)計(jì)時不低于 c20。其實(shí)在許多大城市根據(jù)相關(guān)規(guī)定，從2020年以后就不再允許使用磚混結(jié)構(gòu)設(shè)計(jì)了，這也是提高防震級別的一種措施，但事實(shí)上有多 少地方落實(shí)了這一政策，尤其像汶川這種曾名不見經(jīng)傳的小地方，為此我們要在全國尤其是地震帶的建筑由磚混向框架等結(jié)構(gòu)轉(zhuǎn)變上多下些力氣。如實(shí)際地震是 10 度，雖然超過了極限強(qiáng)度，但當(dāng)結(jié)構(gòu)有裂縫后，剛度迅速降低，結(jié)構(gòu)變軟，共振不復(fù)存在，地震力也變小了。再者，抗震驗(yàn)算時不同的樓蓋及布置 (整體性 )決定了采用剛性、剛?cè)?、柔性理論?jì)算?？蚣芙Y(jié)構(gòu)的側(cè)向剛度較小，屬于柔性結(jié)構(gòu)，側(cè)向位移大，在水平荷載作用下，變形曲線為剪切型。當(dāng)與水平地震作用方向平行的墻肢截面高寬比接近 1 時，墻體以剪切變形為主；在剪力和豎向壓力共同作用下，墻內(nèi)主拉應(yīng)力超出砌體強(qiáng)度，墻體出現(xiàn)斜裂縫；由于地震的反復(fù)作用，兩方向斜裂縫交叉成 X 形；當(dāng)墻肢高寬比較小時，則在墻體中間部位出現(xiàn)水平裂縫。在四川省僑務(wù)部門對地處重災(zāi)區(qū)的 69 所 “僑心學(xué)校 ”的調(diào)查中發(fā)現(xiàn)。 【關(guān)鍵詞】 磚混；框架；選擇；性價比 我國地處世界上兩個最活躍的地震帶中間，東瀕環(huán)太平洋地震帶，西部和西南部是歐亞地震帶經(jīng)過 的地區(qū)，是世界上多地震國家之一，為此我們必須加強(qiáng)地震研究和預(yù)防工作。 as mortar and brick, block the cohesive force between the poor unreinforced tensile, bending and shear strength is low, seismic and crack resistance of poor construction quality and difficult to control, it is easy to structural damage, a rigid structure, this earthquakeprone areas should be used with caution such structures. The brick structure has the following damage of housing characteristics: (1) wall damage, the level of earthquake to masonry shear walls in bending. When the direction and level of seismic crosssection parallel to the wall for high aspect ratio close to 1, wall to shear deformation of the main。s strength is especially evident, although the price higher, but with the masonry to more cost effective. As more seismic capacity frame shear wall structure, its high price and low popularity is difficult to build largescale. 【 Key words】 masonry。 cost China is located in the world39。 parison of height to width when the wall for hours, then in the middle of a horizontal wall cracks. (2) vertical and horizontal wall joints damaged. Vertical and horizontal wall joints are a weak link in masonry, earthquake interaction between vertical and horizontal walls, cracks in the transition out of, resulting in vertical wall outward tilt or collapse. (3) to highlight a subsidiary of the roof structural damage. Prominent roof between the roof, parapets and other ancillary structures, due to earthquakes, whipside effect effect, the horizontal displacement is large, and the structure of the lack of a reliable connection, often collapsed damage. Damage statistics show that in the strong earthquake, the multistorey masonry wall is mainly connected with the destruction of ponents, and housingstorey big, thick layers, a relatively more serious damage. The structure of housing limited to masonry materials due to their characteristics (poor ductility), coupled with structural integrity is relatively poor, under t