Develop a validated high fidelity physics based computational method to evaluate building performance and collapse under blast loading with the capability to show the resulting damage and debris fly-out in a realistic fashion. Key requirements for the developed method are: 1) sufficient fidelity to capture critical phenomena in building collapse and 2) an intelligent user friendly interface to allow practicing engineers to obtain accurate results faster than the current traditional high fidelity computational methods. DESCRIPTION: The Defense Threat Reduction Agency (DTRA) seeks proposals for development of a high fidelity model for analysis of building collapse under blast loading. Realistic visualization of the damage and debris is an important aspect of the requirements in order to assess damage to Weapons of Mass Destruction (WMD) containers in a targeted building or to assess vulnerability of personnel and mission critical equipment in a protected facility. Structural collapse under blast conditions involves an initially stable structure acted upon by gravity loads, followed by the imposition of blast loads (a relatively short duration event) which induce material and structural damage. The latter in turn, may lead to global structural instabilities which can result to the collapse of the original structure. Computational modeling of collapse entails three dimensional (3D) geometry, non-linear material and geometry, and highly dynamic events such as material breakup and ejection. In the past several decades the Finite Element Method (FEM) has been used successfully to model complex dynamic events including building collapse. FEM formulations have incorporated implicit, explicit or hybrid integration techniques to accurately model various phenomena in building collapse. To capture the results for visual presentations the FEM models typically run over the entire collapse event which may take several weeks to months of computer run time. Sophisticated mathematical formulations have been developed for more efficient computations and for fracture and breakup of materials. However, their proper implementation requires a highly educated and experienced scientist or engineer. Often times the results generated by the FEM model differ depending on the experience of the user with the FEM model of interest. The extensive computation time and high level of expertise required to use existing FEM models for building collapse are barriers to wide use of the technology. To overcome these barriers an innovative computational method is sought that a practicing engineer can install on a single or dual processor personal computer and use it to model a collapse event within a couple of days of computer run-time. The ideal methodology should combine robust and time proven FEM formulations with more efficient integration methods and algorithms to keep track of material break up, flight and contact. To reduce the level of user expertise with the new computational method an intelligent and user friendly interface is sought that can generate the required models and process the results for video-like presentations within a short timeframe. The new method has to be able to model framed structures made of reinforced concrete and steel with curtain or in-fill walls and load bearing structures made of masonry, wood and steel with punched windows. Presets of models for structural framing connections should be made available for users to speed up the building model creation process. PHASE I: The successful Phase I project should develop the outline for the proposed methodology in sufficient mathematical detail to show technical competency. If the methodology is already developed for other highly dynamic applications like vehicle crashes or building demolition the Phase I project should also include limited validation of the methodology against full-scale blast tests of building components like walls or columns. PHASE II: The successful Phase II project will result in a blast test validated user friendly and fast running computational method for collapse analysis of buildings subjected to blast loading. PHASE III: Dual use applications. Analysis for building collapse is a requirement for new construction within the government and increasingly in the commercial sector. ASCE 7-02, Minimum Design Loads for Buildings and Other Structures, added commentary on design alternatives for resistance to progressive collapse. Building code writing organizations, such as ASCE, SEI, ACI, IBC, ANSI, PCI, etc., have committees reviewing design for progressive collapse resistance, which will likely lead to national standards. Dual use applications would include a more robust, yet fast method for complying with emerging building codes analysis requirements, building and bridge demolition, and forensic studies in support of accident investigations. A Phase III project would develop an end to end product with licensing for software releases, user manuals and training materials and worked out examples. REFERENCES: 1. Kimiro Meguro and Hatem Tagel-Din, Applied Element Simulation of RC Structures under Cyclic Loading, ASCE, November 2001, Vol. 127, Issue 11, pp. 1295-1305. 2. Ante Munjiza, The Combined Finite-Discrete Element Method, John Wiley and Sons Ltd., 2004. 3. T. Belytschko, J. S. Chen, Meshfree and Particle Methods, John Wiley and Sons Ltd., 2007. 4. Klaus-Jurgen Bathe, Finite Element Procedures, Prentice Hall, 1996. 5. "Flex Template System for Blast Modeling of Structures," by Vaughan, Nikodym, Xie and Ettouney, Sixth Asia-Pacific Conference on Shock and Impact Loads on Structures, 2005.
Keywords: Structural Collapse, Blast, Computational Methods, Material Models, High Fidelity Techniques.
