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济南大学毕业设计外文资料翻译毕业设计外文资料翻译 题 目 建筑结构在冲击负载作用下的 连续倒塌分析方法 学 院 土木建筑学院 专 业 土木工程 班 级 土木 1107 学 生 陈浩 学 号 20110622014 指导教师 林明强 二一 五 年 三 月 一 日TRANSACTIONS OF TIANJIN UNIVERSITY, 2008,14(5)Methods for Progressive Collapse Analysis of Building Structures Under Blast and Impact LoadsLI Zhongxian(李忠献)，SHI Yanchao(师燕超)(School of Civil Engineering，Tianjin University，Tianjin 300072，China)Abstract： Progressive collapse of building structures under blast and impact loads has attracted great attention all over the worldProgressive collapse analysis is essential for an economic and safe design of building structures against progressive collapse to blast and impact loads. Because of the catastrophic nature of progressive collapse and the potentially high cost of constructing or retrofitting buildings to resist it，it is imperative that the progressive collapse analysis methods be reliable1. For engineers their methodology to carry out progressive collapse evaluation need not only be accurate and concise，but also be easily used and works fastThus，many researchers have been spending lots of effort in developing reliable，efficient and straightforward progressive collapse analysis methods recently. In the present paper，current progressive collapse analysis methods available in the literature are reviewedTheir suitability applicability and reliability are discussedOur recent proposed new method for progressive collapse analysis of reinforced concrete frames under blast loads is also introducedKeywords： progressive collapse analysis;building structures;blast load;impact load Progressive collapse is defined as“the spread of an initial local failure from element to element resulting in the collapse of an entire structure or a disproportionately large part of it”1. It refers to the failure of one or a group of key structural loadcarrying members that give rise to a more widespread failure of the surrounding members and partial or complete structural collapse2Progressive collapse of building structures might be induced by a series of accidental and intentional events such as false construction order，local failure due to accidental overload，damage of critical component by explosion and earthquakeThis paper only focuses on progressive collapse analysis of building structures induced by abnormal loads，such as blast and impactWith the recent progressive collapse of Alfred P.Murrah Federal Building and world Trade Center (WTC)researches are more focused than ever on constructing buildings safer from progressive collapse induced by blast and impact loadsProgressive collapse analysis is essential for an economic and safe design of building structures against progressive collapse to blast and impact loadsBecause of the catastrophic nature of progressive collapse and the potentially high cost of constructing or retrofitting buildings to resist it，it is imperative that the progressive collapse analysis methods be reliable3For engineers，their methodology to carry out progressive collapse evaluation need not only to be accurate and concise，but also be easily used and works fastThus，many researchers have been spending lots of effort in developing reliable，efficient and straightforward progressive collapse analysis methods recentlyThe current available methods in analyzing structural progressive collapse could be classified into two major categories，namely the direct simulation method，in which the blast loading effects on structural damage and building collapse are directly simulated，and uncoupled alternative load path method with analysis of the structure by simulating various levels of damage by the removal of key loadcarrying members4In the present paper，the available progressive collapse analysis methods in the literature are reviewed according to their categoriesBoth advantages and disadvantages of each method are listedTheir suitability，applicability and reliability are also discussedOur recently proposed new method for progressive collapse analysis of reinforced concrete frames under blast 1oads is also introduced1. Progressive collapse analysis methods for building structures. In this section，the current methods for analyzing structural progressive collapse available in the literature are presented in two major categories，namely the direct simulation method and the alternative load path method1.1 Direct simulation method For the direct simulation method，the building structures，air，and explosive are all modeled in detailExplosion，blast wave propagation and its interaction with structures all need to be simulated，if not，blast and impact loads acting on the building structure should be derived and directly applied to structural component5sThe material nonlinear behavior and dynamic effects and damage due to blast or impact are mostly included in the simulationThis section will list typical applications of direct simulation method in progressive collapse analysis of building structures recently，each with its own characteristic.1.1.1 Direct simulation of building collapse under blast loads Luccioni et al6 carried out an analysis of structural collapse of an actual building，the AMIA (Israels Mutual Society of Argentina)building，which had suffered a terrorist attack and collapsedIn the analysis，the building was modeled using 3一dimensional solid elements， including the reinforced concrete columns，beams and masonry wallsFig1 gives the configuration of the building model and the location of the explosion. The analysis of the structural collapse of the building was performed in two stagesThe first part of the analysis consisted of the simulation of the explosion itself from the detonation instant and the second part consisted of the analysis of the effect and interaction with the building of the blast wave generated by the explosion7Only the load produced by the air blast wave was considered in the analysisThe ground motion generated by the explosion was not taken into account Fig2 shows the numerical results of the collapsed buildingThe comparison of numerical results with photographs taken after the terrorist attack showed that the numerical analysis accurately reproduced the collapse of the building under the blast loadThe good agreement between actual damage and that one numerically obtained proves that the detailed simulation of the structure，materials and blast effects are needed for this type of analysis and nowadays represent the only way to successfully run a complete collapse analysis of an entire building This case represents a good example of using direct simulation method to carry out the progressive collapse analysis of structuresThat is，the method could successfully predict the progressive collapse process of the structure under blast and impact loadsHowever，this accuracy is achieved at great costIn order to derive the accurate material parameters，experiments should be carried out firstThe building structures，air，and，explosive should be modeled in detail，which need thousands of elementsSpecial algorithms and software were also needed to calculate the blast wave-structure interaction and to catch the damage and collapse behavior of the building structureTherefore，it is extremely time consuming，and requires a profound knowledge of structural dynamics，damage mechanics，dynamic material properties and computational skills112 Collapse analysis of the World Trade Center Quan and Brinbaum8 carried out a 3-dimensiona1 computer simulation of impact and collapse of the WTC North Tower using AUT0DYN 3D computer program to numerically reproduce the entire event of impact and collapse of the North Tower of WTC on September l1. Their model included the entire building of the WTC North Tower and a Boeing 767 passenger jetThe threedimensional finite element model used in the simulation contained a total of 270 000 beam and shell elementsAll the columns on the perimeter wall as well as inside the central core were simplified，being modeled by beam elements instead of using solid elements or shell elementsFloors and roof were modeled by the AUTODYN shell solverThe Boeing 767 airplane was also modeled in detail using AUTODYN shell solver and Lagrange solverFig3 gives the AUTODYN-generated 3一dimensional finite element model of the WTC North Tower and the Boeing 767 airplane The complete simulation consists of four stages：static equilibrium calculation to get the initial stresses and strains from gravity；simulation of a Boeing 767 airplane impacting the tower；the reduction of the strength and stiffness of the tower resulting from the post-impact fuel fire；and finally，the progressive collapse of the Tower driven by gravity Fig4 gives one of the typical results，which presents the material location of the tower at 65 s after the impactAs can be seen，the building had already collapsed to half of its heightThe numerical results showed that a scientifically substantiated plausible scenario for the impact and collapse event of the North Tower could be obtained through the numerical simulationIn the progressive analysis，a reasonable simplification in the modeling such as using simple elements to represent complex behavior of structural members will not affect the accuracy of the results，while this might dramatically reduce the size of the mode1This could save lots of computer memories and computing time，especially for the complex structures，such as tall buildings9Of course certain finite elements are still needed to be developed. 1.1.3 DYN method in progressive analysis of RC flame Hao et al10 proposed a DYN method based on the continuum damage mechanics theoryThe main difference between this method and other direct simulation methods is that the explosion initialization and blast wave propagation were not directly modeledInstead， blast loads acting on the structure were calculated first using the formulae given in TM5130011 and Ref. Then they are directly applied on front，side，roof and rear of the building structure This method was used to analyze structural progressive collapse of a three-storey and two-span reinforced concrete (RC）frame structure12Computer software LSDYNA with userdefined subroutines was used to perform the analysesFig5 gives the configuration of the RC frame and the explosive locationIn the analysis，the blast was assumed to be detonated on ground surfaceThe blast weight was chosen to be 1 000kg equivalent of TNT，while the scaled distance used was 17 mkg1/3 ，at which only the first floor middle column would collapse due to blast effects Fig6 shows the numerical results of the structural progressive collapse obtained from DYN method analysisAs can be seen，DYN method gives reasonable prediction of the RC frame collapse under critical blast loadIn their study，comparisons were also made between results from DYN method，GSA and DoD guidelines based alternative load path methods13It was found both the GSA and DoD based alternative load path methods may not give reliable prediction of structural progressive collapse and usually underestimate the stress and strain response at the supporting joint above the blast damaged columns15. As mentioned above，the great improvement of the DYN method is that，interaction between the blast wave and building structure14，blast initial and blast wave propagation are not needed to be directly simulatedIt uses the profound knowledge of blas