Abstract:  During seismic response, redistribution of load carried by damaged or failed structural members to adjacent members may lead to overstress or exceeding load resistant capacity of the other members resulting in spread or propagation of damage until development of collapse mechanisms in seismic progressive collapse of structures. To study the progressive collapse phenomenon of structures during earthquakes, nonlinear analyses of reinforced concrete bridges have been done carried out by the Applied Element Method (AEM). The simplicity of the AEM procedures which take into account fracture separation of structural components and the inertial impact load effects of falling debris makes it attractive for progressive collapse analysis of structures. The results show the detailed failure sequence and propagation of damage in the seismic progressive collapse of the analyzed bridges.

D. Lau and H. Wibowo: Seismic Progressive Collapse Analysis of Reinforced Concrete Bridges by Applied Element Method, Proceedings of the 12th International Conference on Engineering, Science, Construction, and Operations in Challenging Environments, March 2010.

I. Mohamed, R. Seracino, and S.T. Smith: Analysis of FRP-to-Concrete Joint Assemblies with FRP Spike Anchors using the Applied Element Method, The Second Official Interntational Conference of International Institute for ERP in Construction for Asia-Pacific Region, December 2009.

Abstract: The numerical simulation of a progressive collapse of structures is a very actual concern. Engineers are more and more interested in structures integrity estimation and collapse theory finding, in order to develop strategies for increasing or decreasing the progressive failure. A new method has been developed, for the last years, called Applied Element Method that has a large practicability for failure modeling. This method is used by "Extreme Loading for Structures” software.

This paper has two main goals: (i) a short presentation of the Applied Element Method in regard to the Finite Element Method and (ii) the presentation of the case study both as mathematical modeling and as demolition of structure. The results show a good correlation between numerical simulation and real demolition of the structure.

Marin Lupoae, Carmen Bucur: Use of Applied Element Method to Simulate the Collapse of Buildings, SISOM 2009 and Session of the Commission of Acoustics, Bucharest, 28-29 May 2009.

Abstract: The research on progressive collapse of structures generally focuses on gravity and blast loadings and the design objective is to increase the redundancy and robustness of structures to prevent progressive collapse. Studies of bridges damaged by earthquake in past major earthquakes have shown that better methodology for earthquake resistant design of new bridges can be developed. Moreover, effective retrofit and strengthening strategies can be devised to enhance the performance and safety of existing deficient bridges if progression of damage from initial failure to ultimate collapse, and its impact on the failure mechanisms of structures, is better understood. This paper presents the modelling and analysis of progressive collapse behaviour of bridges during earthquakes using the Applied Element Method that can take into account separation of structural components resulting from fracture failure and contact or impact forces of falling debris. The results show significant influence of the progressive collapse phenomena on the performance of bridges during major earthquakes. These also demonstrate the need to consider progressive collapse mechanisms in seismic design performance assessment and evaluation of bridges that would lead not only to a safer and more reliable earthquake resistant design for new structures but also more effective retrofit and strengthening strategies for older structures.

Hartanto Wibowo, S.M.CSCE; Silvena S. Reshotkina; and David T. Lau, F.CSCE: Modeling Progressive Collapse of RC Bridges during Earthquakes, CSCE Annual General Conference 2009: On the Leading Edge, May 2009.

Abstract:  As an approach to the problem of seismic vulnerability evaluation of existing buildings through the predicted vulnerability method, analytical models can be applied to define the capacity curves of typical buildings which represent different building classes. These curves are then combined with the seismic demands to produce the vulnerability curves for each of the building classes according to the damage states definition. For some buildings types, mainly the masonry structures, the development of the capacity curve is complicated and time consuming if a finite element based method is used because the model has to represent the structural geometry and relationships between different structural elements through element connectivity. Moreover, the FEM is not able to properly represent large displacements and separations for progressive collapse simulations. Therefore, the Applied Element Method which combines the advantages of FEM with that of the Discrete Element Method in terms of accurately modeling a deformable continuum of discrete materials is used here to calculate the capacity curves for those challenging building classes. This leads to a better estimation of the lateral capacity of building classes under study. In order to overcome the uncertainty in the construction material properties for existing buildings, each model is run for a vast range of material properties and the Monte Carlo method is applied to obtain the capacity curves for each building class. These curves can then be used to compare the seismic response of different building classes with a specific seismic demand or to develop scores which correlate potential structural deficiencies with structural characteristics for different classes.

Karbassi A. and Nollet MJ.: Application of the Applied Element Method to the Seismic Vulnerability Evaluation of Existing Buildings, 6th Structural Specialty Conference, Canadian Society for Civil Engineering, Quebec City, QC, paper ST-401, June 2008.

Y. Tokal, H. Najm: Protecting Bridges Against Blast Loads, 4TH New York City Bridge Conference Program, August 2007.

Many trials have been made to numerically simulate the Alfred P. Murrah Building bombing event using Finite Element Method. These trials were based on removal of one of the main supporting columns to investigate the generated internal forces and the possible deformations in other elements. However, these trials could not simulate real bomb explosion and automatic detection of the failed columns and floor slabs. Furthermore, the finite element analysis could not continue to model separation of failed elements, collision between structural elements till complete collapse. In this paper, a new technique, Applied Element Method (AEM), is used to simulate the collapse process of the Murrah Building. The bomb weight and location are considered in the simulation. Free-Field blast wave was assumed. The building dimensions, reinforcement and material properties were taken into account. The simulation shows real time analysis of the building performance since the blast occurs, failure of one of the supporting columns, and the failure of the supporting transfer girder till partial collapse of the structure. Two more cases were studied; the bomb was moved to the corner of the building and increasing reinforcement of the transfer girder to check building performance during these events. Results indicate that design firms, engineers, and insurance companies now can judge the safety of existing structures when subjected to extreme loads and to study the safety of proposed structures prior to their construction.

Hatem Tagel-Din and Nabil Rahman: Simulation of the Alfred P. Murrah Federal Building Collapse Due to Blast Loads, Architectural Engineering National Concerence, Omaha, Nebraska, March29-April 1, 2006.

Hatem Tagel-Din: Collision of Structures During Earthquakes, Proceedings of the 12^th European Conference on Earthquake Engineering, London, UK, September 9^th - September 13^th, 2002 .

Hatem Tagel-Din and Kimiro Meguro: Analysis of a Small Scale RC Building Subjected to Shaking Table Tests using Applied Element Method, Proceedings of the 12^th World Conference on Earthquake Engineering, New Zealand, January 30^th -February 4^th, 2000.

Kimiro Meguro and Hatem Tagel-Din: A New Simplified and Efficient Technique for Fracture Behavior Analysis of Concrete Structures, Proceedings of the Third International Conference on Fracture Mechanics of Concrete and Concrete Structures (FRAMCOS-3), Gifu , Japan, Oct. 1998.