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(中國(guó)建筑設(shè)計(jì)研究院 北京 100044)
【提要】 首都博物館新館上部大跨度鋼結(jié)構(gòu)受力復(fù)雜。利用風(fēng)洞模擬大氣邊界層氣流，對(duì)屋蓋上、下表面和建筑外墻在各種風(fēng)向角下的風(fēng)壓分布情況、風(fēng)環(huán)境等進(jìn)行了測(cè)試。在屋蓋挑檐的端部設(shè)置百葉，有效地減小了長(zhǎng)懸臂結(jié)構(gòu)的風(fēng)荷載效應(yīng)。從多自由度體系在脈動(dòng)風(fēng)荷載作用下的運(yùn)動(dòng)方程出發(fā)，根據(jù)隨機(jī)振動(dòng)理論推導(dǎo)出了用于大跨度結(jié)構(gòu)計(jì)算的風(fēng)振系數(shù)公式，并考慮了場(chǎng)地類別、結(jié)構(gòu)阻尼比對(duì)脈動(dòng)增大系數(shù)ξ的影響。在國(guó)內(nèi)首次采用熱完成工藝成型方管作為主桁架的弦桿與腹桿，桁架的腹桿與弦桿直接相貫焊接，為了使設(shè)計(jì)經(jīng)濟(jì)合理，采用了多種方式提高節(jié)點(diǎn)的承載力。針對(duì)傳統(tǒng)柱間預(yù)應(yīng)力支撐體系存在的張拉過(guò)程復(fù)雜、柱頂偏移不易控制、在柱間桁架下弦桿引起附加軸力等問(wèn)題，提出在中柱兩側(cè)布置人字形拉桿的支撐形式，大大簡(jiǎn)化了預(yù)應(yīng)力張拉過(guò)程，有效避免了柱頂?shù)钠疲瑴p小了柱間桁架下弦的附加軸力。
【關(guān)鍵詞】 大跨度結(jié)構(gòu) 長(zhǎng)懸臂 風(fēng)洞試驗(yàn) 方管桁架 節(jié)點(diǎn) 風(fēng)振系數(shù) 預(yù)應(yīng)力 高強(qiáng)鋼材
Largespan Roof Design of Capital Museums New Building/Fan Zhong,Li Ming,Fan Yuchen,Ren Qingying(China Architecture Design & Research Group,Beijing 100044,China)
Abstract:The largespan roof of the Capital Museums New Building is very complicated. The wind pressure on outer and inner surfaces of the roof,the outside walls of the building and the wind environment at different wind directions are determined by the boundarylayer wind tunnel test.The persiennes set at the roof end can reduce upliftwind load significantly.Based on the multifreedom motion equation of pulsatile wind loads,the calculating equations for the windvibrating factor of the largespan roof are deduced based on the random vibrating theory.The effect of terrain type and damping ratio of the structure to the pulsatile amplifying coefficient are also taken into consideration.Hot finished square tubes are used as chord members and diagonals the first time in China.The chord members and diagonals are welded together directly.Several methods are introduced to increase the bearing capacity of the connections for minimizing the steel tonnage.According to the problems in the traditional tension bracing systems,a new method that the tensioning bars are arranged on the two sides of the middle column symmetrically,is presented.In this way,the procedure of prestressed tension can be easily controlled,the sway of column tops can be avoided,and the additional axial forces in the bottom chord of the trusses can be reduced.
Keywords:largespan structure;long cantilever;wind tunnel test;square tube truss;truss connection;wind vibrating factor;prestressed;highstrength steel