Keywords: demolition using controlled explosives, structural collapse, multibody dynamics, collapse simulation, multi-level simulation.

The demolition of structures using controlled explosives is an efficient technology considering laborsaving, security and cost-effectiveness. However, failures of various explosive demolitions in the past indicate the requirements for reliable predictions within the planning process of structural demolitions. Many computer simulation efforts have been carried out to examine the dynamic behavior of the structural collapse. Nevertheless, the simulation models based on conventional finite element approaches are highly computationally expensive or impossible in some complex cases. Therefore, an efficient computer model which requires less computational effort but still maintains a reasonable degree of fidelity in representing the structural collapse process is mandatory.

For this reason, this contribution presents extensions of the approved multi-level concept presented in [1], in order to model the failure of even highly complex structures. Hence, the simulation model is composed of three levels, namely the local, the near field and the global level. The failure effects of the local and the near field failure, as well as the relevant fracture processes of the structural parts are realistically approximated by means of tailor-made multibody subsystems. The subsystems employ specific kinematics as well as force elements representing nonlinear characteristics in terms of force-displacement relationships so-called nonlinear resistance forces. The physical core of the simulation model on the global level is based on a so-called "special multibody system" (special MBS). Assumed rigid parts of the structure and the distribution of the multibody subsystem in the special MBS, are assured by a numerical analysis of a building collapse as given in [2].

The determination of the nonlinear resistance forces in the subsystems is done in advance using the reinforced concrete design approach. Hence, the resistance force of each of the six different directions is obtained from the analytical calculation of the reinforced concrete section according to the corresponding load type e.g. axial load, moments, shears and torsion. Consequently, a generalized six-directional nonlinear force element in the multibody subsystem can be generated by combining all the six resistance forces. This force element can be used to describe a reinforced concrete structure under tension-compression, shear, torsion and bending moments.

A dilapidated ten-story building is given as an example model. The paper demonstrates the efficiency of using a multibody model for the collapse simulation of large scale complex structures due to controlled explosives. The nonlinear resistance forces are calculated from the analysis of the given reinforced concrete section. The simulation result of the multibody model applied by taking into account these nonlinear force elements shows satisfying agreement with the results obtained from the finite element analysis.

1

D. Hartmann, M. Breidt, V.V. Nguyen, F. Stangenberg, S. Höhler, K. Schweizerhof, S. Mattern, G. Blankenhorn, B. Möller, M. Liebscher, "Structural collapse simulation under consideration of uncertainty - Fundamental concept and results", Computers and Structures, 86, 2064-2078, 2008. doi:10.1016/j.compstruc.2008.03.004

2

S. Mattern, G. Blankenhorn, K. Schweizerhof, "Computer-aided destruction of complex structures by blasting", in W.E. Nagel, W. Jäger, M. Resch, (Editors), "High Performance Computing in Science and Engineering '06", Springer, 449-457, 2006. doi:10.1007/978-3-540-36183-1_33

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