爆炸下鋼柱破壞時(shí)間及殘余承載力對(duì)鋼框架連續(xù)倒塌的影響

李國(guó)強(qiáng)+楊濤春+陸勇+陳素文

摘 要：建立鋼框架連續(xù)倒塌單自由度（SDOF）分析模型，研究鋼柱破壞時(shí)間及其殘余承載力對(duì)鋼框架連續(xù)倒塌的影響規(guī)律，發(fā)現(xiàn)鋼柱破壞時(shí)間越長(zhǎng)、殘余承載力越大，結(jié)構(gòu)位移響應(yīng)越小.以SDOF模型響應(yīng)的理論解為基礎(chǔ)，得出在鋼框架倒塌計(jì)算中是否考慮鋼柱破壞時(shí)間的界限標(biāo)準(zhǔn)：當(dāng)鋼柱破壞時(shí)間與連續(xù)倒塌的SDOF模型周期比τ<0.2時(shí)，可忽略破壞時(shí)間的影響；當(dāng)τ>3.0時(shí)，可采用靜力方法計(jì)算結(jié)構(gòu)響應(yīng)；當(dāng)0.2<τ<3.0時(shí)，需考慮破壞時(shí)間對(duì)結(jié)構(gòu)連續(xù)倒塌的影響.通過(guò)對(duì)鋼柱等效SDOF模型的理論分析，當(dāng)其抗力模型分別為理想彈塑性和剛塑性條件時(shí)，求得柱子破壞時(shí)間的近似計(jì)算方法，并以爆炸作用后柱子變形為初始狀態(tài)，結(jié)合數(shù)值方法給出鋼柱殘余承載力計(jì)算過(guò)程.通過(guò)對(duì)鋼柱的破壞時(shí)間和殘余承載力對(duì)結(jié)構(gòu)倒塌影響的算例分析，表明鋼柱的破壞時(shí)間（越長(zhǎng)）和殘余承載力（越大）對(duì)結(jié)構(gòu)抗倒塌起有利作用，在結(jié)構(gòu)抗倒塌計(jì)算時(shí)不可忽略.

關(guān)鍵詞：鋼框架； 連續(xù)倒塌； 破壞時(shí)間； 殘余承載力； 單自由度模型

中圖分類號(hào)：TU312.3 文獻(xiàn)標(biāo)識(shí)碼：A

文章編號(hào)：1674-2974（2016）05-0001-08

Abstract：The influence law of failure time and residual bearing capacity of the steel columns on progressive collapse of steel frames was studied by using a single degree of freedom （SDOF） model. The displacement of the steel frames decreases as the failure time and residual bearing capacity of the steel columns increase. On the basis of the theoretical solution of the SDOF model， boundary condition of the model was determined to consider the failure time effect. τ was defined as the ratio of the failure time to natural period of the SDOF model. For τ<0.2， the failure time can be ignored. For τ>3.0， a static method can be used to estimate the structure behavior. However， for 0.2<τ<3.0， the failure time should be considered in the progressive collapse analysis. When the resistance model is ideal elastic-plastic and rigid-plastic， the equivalent SDOF model of the steel columns can be theoretically analyzed to determine the calculation method of the failure time. Considering the deformation of the steel columns after explosion as the initial state， the calculation process for the residual bearing capacity of the steel columns is gained by combining with numerical calculations. The results show that the failure time and residual bearing capacity significantly influence on the progressive collapse of the steel frames， and those effects should be considered in the progressive collapse analysis.

Key words：steel frame； progressive collapse； failure time； residual bearing capabicity； single degree of freedom model

在爆炸作用下，構(gòu)件破壞雖然持續(xù)時(shí)間很短，但并非均可簡(jiǎn)化為瞬間發(fā)生，同時(shí)，破壞構(gòu)件或具有一定殘余承載力.事實(shí)上破壞時(shí)間及殘余承載力的存在將直接影響個(gè)別構(gòu)件破壞后整體結(jié)構(gòu)的響應(yīng)形式.由于拆除構(gòu)件法假定構(gòu)件在瞬間被移除[[1-3]，忽略了破壞時(shí)間和殘余承載力的影響，從而影響到構(gòu)件破壞后整體結(jié)構(gòu)響應(yīng)計(jì)算結(jié)果的準(zhǔn)確度[4-5].為提高評(píng)估鋼柱損傷后鋼框架抗連續(xù)性倒塌能力的準(zhǔn)確性和可靠性，需要考慮鋼柱破壞時(shí)間和殘余承載力的影響.

鋼柱的破壞時(shí)間是爆炸作用后柱軸力快速下降的反應(yīng)時(shí)間，它主要影響結(jié)構(gòu)的動(dòng)力效應(yīng)，破壞時(shí)間越短動(dòng)力效應(yīng)將越大.柱殘余承載力指柱受爆炸破壞后殘余的軸向承載力，在爆炸作用后，有關(guān)柱子殘余承載力的研究相對(duì)較少，僅國(guó)外對(duì)混凝土柱有少量研究.Wu[[6-7]，Bao[[8]等對(duì)爆炸作用后混凝土柱的殘余承載力進(jìn)行了數(shù)值研究，并試驗(yàn)驗(yàn)證了結(jié)果的合理性，同時(shí)，通過(guò)參數(shù)化分析擬合出了RC柱的殘余承載力計(jì)算公式.

通過(guò)建立框架結(jié)構(gòu)連續(xù)倒塌的單自由度分析模型，研究柱子破壞時(shí)間和殘余承載力對(duì)結(jié)構(gòu)連續(xù)倒塌的影響，給出是否考慮破壞時(shí)間的界限標(biāo)準(zhǔn)；通過(guò)對(duì)鋼柱的等效單自由度模型的理論分析， 根據(jù)其抗力模型分別為理想彈塑性和剛塑性條件，給出柱子破壞時(shí)間近似計(jì)算方法，并以爆炸作用后柱子變形為初始狀態(tài)，給出鋼柱殘余承載力計(jì)算方法.