PSI - Issue 84

Ahmed Amir Khalil et al. / Procedia Structural Integrity 84 (2026) 1031–1038

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review under responsibility of the scientific committee of the Conference Keywords: Applied Element Method, Industrial facilities, hung boilers, High fidelity modeling, Deconstruction analysis, Safer decommission methodology.

1. Introduction This work focuses on the modeling and analysis of two structures in a 1.7-gigawatt coal power plant: a steel frame boiler unit and a reinforced concrete stack. The boiler unit is a typical braced steel frame with the principal equipment such as boiler and air heater hung from the roof steel frame. The deconstruction procedure provides the weakening of the structure through strategic removal of girder and bracings at the lower level and hinge, flat or double V cut in the columns. The building collapse is triggered by shaped charges causing the removal of specific columns. In the following, the 3D AEM numerical model with all the crucial structural details implemented is presented. The AEM model reproduces the effective strength and stiffness of the weakened elements and load redistribution in the configuration immediately prior to the blast event. Thanks to the simulation results, the cut in specific columns is optimized to reduce the risk of unexpected or excessive deformations. Finally, the collapse sequence and the debris spread is presented in comparison with the real case. The reinforced concrete stack consists of a reinforced concrete outer shell with three internal FRP liners supported by steel platforms at two different levels. The numerical model with all the structural details such as explicit model of supporting steel platforms and FRP liners is presented. The demolition strategy provides the saw cut of part of the stack flush to the ground and then the blast of the front portion towards to the fall direction. The 3D AEM model reproduces the collapse sequence, allowing the evaluation of vertical drop and consequently the risk of possible squat and uncontrolled fall direction. The simulations show a significant vertical drop and possible deviation from the desired fall direction; therefore, an optimization of the demolition plan is designed thought the reduction of blast area and reinforcing of openings at the base of the outer shell. All the mitigation measures are explicitly implemented in the model leading to an improvement of the collapse behaviors. Through nonlinear dynamic simulations, the study demonstrates how AEM can efficiently model crucial structural details and consequently assist engineers in optimizing demolition strategies improving the safety and efficiency of decommissioning operations. 2. Description of the structures 2.1. Boiler unit The boiler structure analyzed consists of a typical braced steel frame, mainly constituted by single diagonal bracing and concentric braced frames. The entire structure presents considerable size with a 56 m x 56 m footprint and an elevation of about 65 m with fourteen levels. Figure 1 shows a plan and elevation view of the boiler unit. Between axis L & G and 12c & 15d the boiler and air heater are located. This equipment are hung from the top, determining a specific design of the roof steel frame with very large beams resting on massive steel columns. The principal steel frames on these axes from L to G between 12c and 15d are composed of 14WF730 imperial size columns (width: 46 cm and depth 57 cm with flange and web thickness of 12.4 and 7.7 cm respectively) and nonstandard girders up to a depth of 5.0 m. A relevant structural detail is represented by the strengthening of the steel columns on axis K and J at the lower level. Here additional 3 cm thickness steel plates are welded at both the flanges. On top of the building roof an electric tower (typical steel truss structure) was erected with a height of 42 m. 2.2. Reinforced concrete stack The reinforced concrete stack has a height of 158 m for the reinforced concrete shell with 25.91m outside diameter and 63.5 cm thickness at the base. The thickness of the reinforced concrete varies with the height. Three FRP liners

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