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September 11th Testimony
MSC.Software Corp has provided simulation software tools MSC.Dytran and MSC.Marc to a US Congressional Committee to simulate and understand the collapse of the World Trade Center buildings.
On March 6, 2002, Dr. Abolhassan Astaneh-Asl, PhD., professor of Civil and Environmental engineering at the University of California, Berkeley, testified before the Committee on Science of the U.S. House of Representatives regarding his investigation of the WTC collapsed structures. His testimony included a series of simulations, developed in conjunction with MSC.Software using MSC.Dytran, of a 747 jetliner crashing into a steel structure.
"The tragic events of September 11th prompted us all to ask what we could do to help," said Frank Perna, chairman and chief executive officer of MSC.Software. "MSC.Software has a long history of working with researchers and governmental entities around the world to recreate complex engineering problems, including those dealing with forensics, in the hope of preventing tragedies like the World Trade Center collapse in the future. We are proud to have played a small part in the efforts up to this point and hope more governmental agencies will take up our offer to provide our software and services free of charge to any government entity investigating the attacks."
"Understanding how and why the World Trade Center buildings collapsed will help us prevent this type of building collapse in the future", said Dr. Astaneh-Asl, "To simulate the very complex issues and non-linearities involved in analysing the impact of an airplane and the ensuing fire you need the most powerful and advanced software, such as MSC.Software's simulation tools. The contributions of MSC.Software to our research program have been invaluable. We will continue to use these tools in our investigation to gain insight to what might have caused the collapse and to learn valuable lessons that can be applied in the future to prevent such catastrophic collapses."
The images accompanying this article show an analysis of the performance of a generic steel high-rise structure subjected to the impact of a 747 jetliner and the ensuing fire. The example demonstrates the power of advanced technology developed in aerospace and mechanical engineering that can be brought to bear on such a problem. Professor Astaneh has suggested during the investigation (which is still ongoing, with a fuller report due out in September this year) that a possible cause of the collapse was the buckling of the exterior columns of the WTC towers after being subjected to intense heat. He also investigated fracturing of the steel columns and the break up of the plane that occurred during the dynamic impact.
MSC.Dytran helps engineers predict how structures respond to real-world, high-speed events such as crashes. Typical applications include airbag deployment and occupant interaction in vehicle crashes, sheet metal forming, bird strikes on aircraft, explosive containment within aircraft structures, ship collision and grounding, projectile impact and penetration, drop tests, sheet metal forging and fluid-sloshing effects on structures. MSC.Marc is a nonlinear analysis tool for advanced engineering simulation. It can be used to simulate temperature effects such as during fires.?
Professor Astaneh's investigation, whilst focusing on the events surrounding the tragic collapse of the WTC due to terrorist activity, was put into sharper focus by more recent events in Milan, where a small aircraft crashed accidentally into the Pirelli building in the center of the city. Being able to forecast the damage that would be caused by deliberate, accidental or environmental events on high-rise buildings enables civil engineers to mitigate the potentially catastrophic results by modifying designs. Whilst not wishing to pre-empt the final results of the investigation it would appear that although considerable damage from such an action could not have been avoided, the eventual collapse of the building was entirely unforeseen.?
A comparison was also made about the efforts made, 30 or 40 years ago, by the National Science Foundation, funded by Congress, regarding the hazards of other 'extreme events' such as earthquakes and their effect on buildings and the subsequent loss of life. Research and engineering communities have been able to develop more efficient and economical technologies to mitigate seismic hazards. Professor Astaneh has been the Principal Investigator in conducting research on damage and collapse of several major buildings and bridges in the aftermath of earthquakes. The approach taken in earthquake engineering can equally be applied to investigation of damage due to terrorist attacks, as well as to minimising the consequences of such attacks. He argues that similar efforts are needed to counter the equally devastating effects of terrorism against the built environment.
Other comparisons with earthquake studies were made by committee member Dr W Gene Corley, the Senior Vice president of CTL Engineering, representing the American Society of Civil Engineers. ASCE has been involved in five recent studies, in El Salvador, India, Seattle and Peru, and, in 1995, examined the Murrah Federal Office Building collapse in Oklahoma City.?
Among the important points made, he stated that one of the main difficulties was in establishing, as accurately as possible, the physical attributes of the buildings prior to the collapse. Doing this, he said, was a monumental task. The construction of the building was documented by literally thousands of engineering drawings. In addition, there were numerous changes to them over their lives. Such data has to be used to construct detailed computer models of the structures. Besides the hard work involved in scouring libraries and other data repositories for the information, ACSE ran briefings for the investigation team using the principal designers to explain how the buildings were constructed.
A principal cause of the collapse of the Twin Towers has been attributed to Progressive Collapse. Dr Corley explained that the likelihood of such an occurrence is dependent upon two inter-related though separate behaviours - the event or load to which the subject is subjected, and the strength or redundancy of the structure. At present there is no rational technical basis to specify either the initiating event or to evaluate the effectiveness of alternative mitigating strategies, and there is a need to develop engineering-based tools to guide the profession in the future.
Dr Corley added, also, that while events like September are rare, fires in buildings are not rare. To improve the performance of structures in a fire environment will also require the development of new tools and design methods through collaboration between fire engineering and structural engineering communities for application to both new and existing buildings.
Further testimony by Dr. Arden L Bement Jr, of the National Institute of Standards and Technology (NIST), discussed progressive collapse as well, regarding it as the spread of failure by a chain reaction that is disproportionate to the triggering event - responsible, besides the WTC, for the large number of deaths in the bombing of the Federal Building in Oklahama City.?
He admitted that the United States has not yet developed standards and practices to assess and reduce this vulnerability. He also stated that the problem for modern buildings is their smaller margin of safety - and the reserve capacity to accommodate abnormal loads - due to increased efficiency in the use of building materials and refinements in analysis techniques. Professor Astaneh's, and others, testimony before the Committee on Science as well as a video of the entire hearing can be found atwww.house.gov/science/welcome.htm. CU?http://www.msc.software.com/
9月11日 聲明
MSC軟件公司通過仿真軟件工具MSC.DYTRAN和MSC.MARC向美國國會委員會模擬，了解世界貿(mào)易中心大樓倒塌的情況。
2002年3月6日，ASL Abolhassan Astaneh博士（加州大學(xué)伯克利分校土木與環(huán)境工程教授），在美國國會眾議院科學(xué)委員會，發(fā)表關(guān)于世貿(mào)中心的調(diào)查倒塌。他的證詞，包括一系列使用MSC.Dytran MSC.Software公司開發(fā)的軟件來模擬波音747客機撞擊成鋼結(jié)構(gòu)模擬。
“MSC.Software公司董事長兼首席執(zhí)行官弗蘭克說：“9月11日發(fā)生的悲慘事件，促使我們?nèi)ピ儐栕约何覀兛梢宰鲂┦裁磥韼椭?。MSC.Software公司有著一段和與世界各地的研究人員和政府機構(gòu)的一起工作，研究復(fù)雜的工程問題的歷史，其中包括處理與取證，防止像在未來類似世界貿(mào)易中心倒塌的悲劇的發(fā)生。我們很榮幸能在努力防止此類事件發(fā)生起到小小的作用，并希望更多的政府機構(gòu)將采用我們提供的免費軟件和服務(wù)來調(diào)查攻擊任何政府實體的事件?！?
“分析了解世界貿(mào)易中心大廈為什么倒塌，將有助于我們防止這種類型的建筑在未來的崩潰”，Astaneh-Asl博士說，“為了模擬非常復(fù)雜飛機的沖擊以及隨后火災(zāi)的問題，你需要最強大和最先進的軟件，比如MSC.Software公司提供的仿真工具。對于我們的研究方案MSC.Software公司的貢獻是非常重要的。我們將繼續(xù)使用這些工具，并通過我們調(diào)查，了解崩潰的誘因，學(xué)習(xí)寶貴的經(jīng)驗，以便在未來防止這種災(zāi)難的發(fā)生?！?
本文附帶的圖片為一個通用鋼鐵高層建筑受到波音747客機的撞擊以及隨后的火災(zāi)影響而發(fā)生的變化，演示了航空航天機械工程的先進技術(shù)在帶來這類問題上所能承受的能力。Astaneh教授在調(diào)查期間（今年九月將進行更全面的報告目前調(diào)查工作還在進行中）發(fā)表崩潰的原因可能是因為世貿(mào)中心雙塔的外部受強烈的熱而彎曲，他還研究了斷裂的鋼柱和飛機解體過程中發(fā)生動態(tài)影響。
MSC.Dytran幫助工程師預(yù)測結(jié)構(gòu)在已知情況下發(fā)生的變化如崩潰以及如何應(yīng)對。典型的應(yīng)用如在車輛碰撞時安全氣囊和乘員的相互作用，金屬板材成形，飛機上的鳥擊，飛機結(jié)構(gòu)內(nèi)爆炸的遏制，船舶碰撞和擱淺，彈丸的影響力和滲透力，跌落試驗，板材鍛造和結(jié)構(gòu)上的液體晃動的影響。MSC.Marc是一個先進的工程模擬的非線性分析工具。它還可以用來模擬溫度的影響比如用在火災(zāi)。
Astaneh教授在調(diào)查由于恐怖活動而造成在世貿(mào)中心悲劇倒塌事件的周邊因素，同時更加關(guān)注在米蘭一架小型飛機墜毀到城市中心Pirelli building的事件。能夠預(yù)測將由高層建筑上的意外或環(huán)境事件造成的損害，使民間的工程師通過修改設(shè)計以減輕可能帶來的災(zāi)難性的結(jié)果。雖然不希望搶先調(diào)查的最終結(jié)果會出現(xiàn)，但是相當(dāng)大的破壞，已經(jīng)不能避免的，建設(shè)的最終崩潰也是完全不可預(yù)見的。
一個比較，30年或40年前由美國國會資助的，通過國家科學(xué)基金會的努力取得了有關(guān)的危害如地震及其對建筑物的影響和隨后的生命損失等研究成果。其后研究和工程社區(qū)已經(jīng)開發(fā)出更有效和經(jīng)濟的技術(shù)，以減輕地震災(zāi)害。Astaneh教授已經(jīng)在幾個主要研究建筑物和橋梁在地震后的破壞和崩潰的團隊擔(dān)任首席研究員。地震工程所采取的方法同樣可以用于調(diào)查恐怖襲擊造成的損害，以及減少這類攻擊的后果。他認為對抗同樣由于恐怖主義而造成對建筑以及環(huán)境毀滅性的打擊需要類似的努力。
煤制油工程的高級副總裁，美國土木工程師學(xué)會代表委員博士W Gene Corley也就地震與ASCE五個最近的研究在西雅圖和秘魯，薩爾瓦多，印度，以及1995年在審查默拉聯(lián)邦辦公室在俄克拉何馬城的建筑物倒塌等進行了比較。
在重要幾點中，他指出，建立以及可能準確描述崩潰前建筑物的物理屬性變化是主要困難之一。他說建立以及可能準確描述崩潰前建筑物的物理屬性變化是一項艱巨的任務(wù)。建筑物的結(jié)構(gòu)是由數(shù)千個工程圖紙描述的。此外，在建筑物生命周期內(nèi)還有許多變化。利用這些數(shù)據(jù)來構(gòu)造詳細的計算機模型結(jié)構(gòu)。除了淘圖書館和其他數(shù)據(jù)信息庫所涉及的辛勤工作，ACSE的跑簡報調(diào)查隊還要找主要設(shè)計師來了解如何建造此建筑物。
雙塔倒塌的主要根源是由于其慢慢倒塌?？评┦拷忉屨f，這種情況發(fā)生的可能是因為兩個相互獨立又相互依賴的事件或主題受到的負荷，結(jié)構(gòu)強度或冗余。目前還沒有合理的技術(shù)基礎(chǔ)去描述開始發(fā)生的事件又或去評估緩解戰(zhàn)略的成效，所以有必要開發(fā)以工程為基礎(chǔ)的工具來指導(dǎo)今后的工作。
科利博士補充，而像九月的事件是罕見的，但建筑物中火災(zāi)并不少見。需要新的工具和設(shè)計方法以及通過與消防工程和應(yīng)用新的和現(xiàn)有的建筑結(jié)構(gòu)工程社區(qū)之間的協(xié)作來改善火災(zāi)環(huán)境中的結(jié)構(gòu)顯示。
國家標準與技術(shù)研究院（NIST）的Dr. Arden L Bement Jr提出的證據(jù)，進一步證明連續(xù)倒塌以及，關(guān)于失敗的蔓延是不相稱的觸發(fā)事件 - 負責(zé)連鎖反應(yīng)，除了世貿(mào)中心，為大量的Oklahama市聯(lián)邦大樓爆炸案的死亡。
他承認，美國尚未制定標準和慣例，以評估和減少此漏洞。他還指出，現(xiàn)代建筑的問題在于安全余量較小儲備能力也較低難以適應(yīng)由于頻繁使用建筑材料和分析技術(shù)的改進以增加效率而造成的異常負載。Dr.Astaneh以及其他人的在聽證會發(fā)表的調(diào)查以及整個聽證會視頻委員會的證詞都可以在www.house.gov/science/welcome.htm以及http://www.msc.software.com/找到。
Solid Views
Version 16 of Cimmetry's Autovue enables user to view solid models over the web and provides a faster and more secure method of transferring model data from servers to clients.
Autovue is one of the most popular visualisation and collaboration tools available. Cimmetry's latest version, AutoVue 16, introduces numerous enhancements - the two most significant using Java to enable designers to download and work on solid models directly over the web, and producing 3D metafiles to speed up the transferral of solid model data to clients, reducing the size of files to the minimum required to view the model.
The new version supports a number of new formats, including EAI/HP DirectModel .JT format and Microstation, and enhances existing support for the major Solid Modelling applications. AutoVue 16 also introduces visualisation for the electronics industry, supporting EDA formats, and there are considerable enhancements to markup, including a Markup Navigation Tree. This enables users to navigate through the markups of collaborators, shown in a list of entities in a markup file, making sure that none are overlooked.
AutoVue SolidModel for Java Cimmetry uses the web's own language, Java, to provide a native, thin-client, 3D visualisation solution, with which design engineers can view and collaborate on 3D CAD designs directly within their web browsers. This simple, out-of-the-box solution relies on straightforward administration of access on the server, no admin for the client, and transparent visualisation of metafile copies of original documents, reducing security issues to a minimum.
Similar to AutoVue's Windows based product, users have access to native 3D CAD assemblies, parts and 2D drafts from all major software suppliers, and can single-click through entire assemblies and family trees, explode assemblies into component parts, manipulate 3D views, view multiple rendering modes and cross-section assemblies. Autovue 16 enables users to switch between 3D assemblies and corresponding draft views, and produce precise measurements of distances, angles, arcs and mass properties.?
Cimmetrys believe that, writing the software in Java 1.1, provides users with a complete 3D visualisation solution on the most widely known platform available - and does not require the thin-client user to have to download Java upgrades before he begins to use the software. Besides being the simplest method of collaborating through web browsers, the software is also integrated with EDM/PDM and supply chain solutions via Cimmetry's Document Management API (DMAPI).
Server Based Metafile?Rendering?
Autovue's SolidModel solution can also be used to optimise performance levels and speed up data delivery. Using Metafiles, it can reduce the amount of data being transferred between the server and the client by a significant amount. After the initial viewing session, when the model is delivered to the client, a 3D Metafile, from 5 to 15% the size of the original solid model file, is generated by Autovue (3D CMF) for subsequent streaming of data. The CMF Metafile, transferring data to and from the server in a continuous stream, has two methods of transmission - to accommodate fast and slow connections. As it is used to gradually build up 3D models on the client's screen, it can be interrupted in full flow - essential, should the client decide to change the view he requires.?
When bandwidth is not an issue, the algorithm cycles through parts in an assembly and requests data from the server via the CMF in 'chunks' - usually about 10% of the original file size, until the full 3D model of the part being viewed reaches full resolution on the screen. Initial views are in coarse resolution, which is improved as more data is received. If the CMF is about 10% of the original model size, and the chunks are 10% of that, only 1% of the original data needs to be transmitted for the client to see the initial view of the complete assembly, and only 0.01% to see the initial view of the first part (given a model with an average of 100 parts).?
The second method is more complex, and looks at the view parameters to compute the level of detail required on a part-by-part basis, only transferring enough data to accurately visually represent the assembly. If a part is completely off the screen, it doesn't need to be updated, and the data will not be sent. If the user zooms in on a part, a higher level of detail will be required. AutoVue uses a number of algorithms to achieve such a high level of interactivity, but the advantage is that only the amount of data needed to view a model is transferred, making considerable savings on the bandwidth and memory required.
Cimmetry say that Version 16 of AutoVue constitutes a significant enhancement over earlier releases, enabling them to offer, now, powerful visualisation and collaboration solutions for both Windows and Java platforms.
http://www.cimmetry.com/
可靠的意見
Cimmetry的AutoVue 16版使用戶在網(wǎng)上查看實體模型，并提供了從服務(wù)器到客戶端傳輸模型數(shù)據(jù)的速度更快，更安全的方法。
AutoVue的是最流行的可視化和協(xié)作工具之一。 AutoVue 16,Cimmetry公司的最新版本介紹了許多增強功能 - 兩種具有重大意義是設(shè)計師能使用Java下載和直接在網(wǎng)絡(luò)中的建立實體模型，并制作三維圖元文件加快了堅實的模型數(shù)據(jù)到客戶端傳輸，減少了文件查看模型所需的最低要求。
新版本支持一些新的格式，包括EAI/HP DirectModel.JT格式和Microstation格式，并提高對現(xiàn)有的主要固體建模應(yīng)用的支持。 AutoVue 16還引入了電子行業(yè)的可視化，支持的EDA格式，并有增強標記的功能，包括標記導(dǎo)航樹。這使用戶能夠瀏覽通過合作者的標記，對照標記文件中的實體名單，確定沒有東西被忽略。
Cimmetry公司的AutoVue Solid java模型使用自己的網(wǎng)上語言，提供本機，客戶機，三維可視化解決方案，設(shè)計工程師可以在瀏覽器中查看和協(xié)作三維CAD設(shè)計。這個簡單的創(chuàng)新解決方案依賴于直接訪問服務(wù)器上，沒有為客戶的管理，透明的可視化圖元文件拷貝原始文件的安全問題減少到最低限度，管理。
相似的對于Windows AutoVue基于產(chǎn)品，用戶訪問原始的3D CAD組件，部件和所有主要的軟件供應(yīng)商的2D草稿，并可以通過整個集會和家庭樹單，點擊，爆炸制成零部件裝配，操縱3D視圖，查看多個渲染模??式和橫截面組件。 AutoVue 16使用戶之間能夠交換3D組件和相應(yīng)的草案的意見，并產(chǎn)生精確的測量距離，角度，弧和質(zhì)量特性。
Cimmetrys相信，在Java 1.1編寫的軟件，為用戶在最廣為人知的平臺上提供一個完整的三維可視化解決方案 - 不需要受客戶機的限制，就開始使用該軟件下載進行Java升級。除了最簡單通過網(wǎng)頁瀏覽器的的方法的合作合作，這個軟件也能夠通過EDM/PDM 得到協(xié)調(diào)和通過Cimmetry的DMAP理論提供鏈的解決方法。
基于服務(wù)器的Metafile渲染
AutoVue的SolidModel解決方案也可以用于優(yōu)化性能水平，加快數(shù)據(jù)傳輸。使用圖元文件，它可以減少相當(dāng)數(shù)量的服務(wù)器和客戶端之間傳輸?shù)臄?shù)據(jù)量。初始觀看會議后，當(dāng)模型被傳遞到客戶端，一個三維圖元文件只有原來的實體模型文件的大小的5％到15％，之后由AutoVue（3D CMF）后續(xù)生成。 CMF的圖元文件，連續(xù)傳輸有兩種方法 - 適應(yīng)快速和慢速連接。當(dāng)它用來逐步建立客戶端的屏幕上的三維模型，用戶可以在全流中斷以防客戶決定改變他的看法。
當(dāng)帶寬是不是一個問題，在裝配零件和通過CMF的“塊”的服務(wù)器請求數(shù)據(jù)通過算法周期 - 通常大約10％的原始文件的大小，直到正在觀看的部分達到全三維模型全分辨率的屏幕上。原來的觀點是一種比較粗糙的解決方法，但是它隨著更多的數(shù)據(jù)被提供而得到改進。如果CMF大約是原始模型尺寸的10%，并且大塊只是它的10%，那么只需要將原始數(shù)據(jù)的1%傳遞給客戶以看到整個集成的最初觀點，另外只有0.01%用于看到第一部分的最初觀點（特定的一個模型平均100部分）。第二方法更復(fù)雜的，觀視圖參數(shù)計算細致的程度要求在一個part-by-part基礎(chǔ)，只有傳輸足夠的數(shù)據(jù)才能準確表現(xiàn)。如果數(shù)據(jù)完全不在屏幕上顯示，它不需要進行更新，數(shù)據(jù)也不會被發(fā)送。如果用戶縮放一部分，那么一個需要提供更高的細節(jié)水平。 AutoVue的算法可以實現(xiàn)這樣一個高層次的互動，只需要傳輸少量模型的數(shù)據(jù)量，需要的帶寬和內(nèi)存大大減少。
Cimmetry公司說AutoVue的16版本，相對于早期版本的有著顯著增強，為Windows和Java的平臺提供強大的可視化和協(xié)作解決方案。
http://www.cimmetry.com/