The research objective of this Faculty Early Career Development (CAREER) Program project is to develop a fracture-constitutive multi-scale model which is able to simulate dynamic fracture in concrete subjected to extreme loadings. The non-linear and fracture behavior of concrete when subjected to dynamic loads such as blast and impact is an increasingly important consideration when designing critical protective structures. To validate the model to be developed, test data collected from a drop tower impact test and blast response data obtained from a shock tube test on reinforced concrete panels will be used. The impact and blast loading tests will be conducted at the US Army Corps of Engineers-Engineering Research and Development Center at Vicksburg, Mississippi. The numerical model will be able to simulate discrete crack initiation without any pre-specifications about the crack path. The numerical model will be implemented in the popular commercial finite element programs ABAQUS and LSDYNA and verified using the project data and other available experimental test data. The behavior of a seven story reinforced concrete structure subjected to blast loading will be simulated and studied. The enhancements to the numerical model will also be utilized in the PI's current study of the mechanical behavior of nano-sized particles such as minerals and collagen fibrils present in dentin and bone.
For broader impact and dissemination of the results, the project will develop educational materials for designers and educators. Examples given in Federal Emergency Management Agency Publication 451 will be augmented to include the blast loading case, as specified in ASCE 7 commentary. The research results will also be made available to code writing bodies such as ACI 318 to incorporate the strain rate effects in design provisions. Besides the graduate students, the undergraduate students will also be involved in the project through NSF and the university programs such as SEARCH. Outreach activities with High School students will be incorporated through the NSF funded project ARROWS.
The National Science Foundation (NSF) funded a study by University of Missouri Kansas City (UMKC) to study the behavior of reinforced concrete slabs subjected to blast loading (Award # CMMI 0748085, PI: Ganesh Thiagarajan). Through Project FRANCES, the PI has addressed the non-linear analysis of concrete structures subjected to extreme loadings, a problem of critical importance that currently lacks a comprehensive solution. The work was completed using a combination of controlled experiments, numerical simulations to develop verifiable models and the development of new graduate level courses in this new and upcoming area of high importance. The PI research goal has been achieved through the development of a fracture-constitutive framework, along with an experimental investigation of the dynamic fracture behavior of reinforced concrete panels. Both normal strength and high strength concrete and steel material were studied experimentally. The experimental component part of FRANCES was performed at the Engineering Research and Development Center (ERDC) located at Vicksburg, MS. The experimental data has provided valuable insights into the behavior of reinforced concrete slabs subjected to controlled blast enviroments, thereby enhancing our understading of the fundamental behavior of these components as protective structures. The experimental results were disseminated to the community in the form a Blast Blind Prediction Contest which was held during 2012-2013 and the winners were announced in October 2013. The contest was developed in collaboration with American Concrete Institute (ACI) Committees 447 (Finite Element of Reinforced Concrete Structures) and 370 (Blast and Impact Load Effects), and the University of Missouri Kansas City School of Computing and Engineering. The goal of the contest was to predict, using simulation methods, the response of reinforced concrete slabs subjected to a blast load. The blast response was simulated using a Shock Tube (Blast Loading Simulator) located at the Engineering Research and Design Center, U.S. Army Corps of Engineers at Vicksburg, Mississippi. The data from the experiments have been distributed to many authors peer reviewed Special Publication documents have been developed under the aegis of American Concrete Institute (ACI). The development of the graduate course titled Design of Structures for Blast and Fire has provided several engineers working in the local community to understand design aspects related to this area. As many or most Government and Military buildings are designed to withstand blast, the course has helped train young engineers in the local Kansas City area - a city which has one of the largest per capital concentration of engineers in the United States of America. Several graduate and undergraduate students have actively worked on this project and have used the research experience gained from the project to develop their own successful careers in structural engineering - thereby enhacing the quality of the workforce in the local economy. Many of them are working in the Kansas City metro area.
