PSI - Issue 84

A.A. Khalil et al. / Procedia Structural Integrity 84 (2026) 983–990

986

Despite these measures, retrofits could only partly compensate for tendon loss and concrete degradation. Residual capacity remained sensitive to the state of original prestressing, thus accurate damage modeling was essential for safe deconstruction planning. 3. Numerical Modeling Approach All three methodologies were analyzed using the Applied Element Method (AEM), Tagel-Din & Meguro (2000), within the ELS software environment, Applied Science International LLC (2004). This approach discretizes structural components into small elements connected by springs, enabling simulation of nonlinear phenomena such as cracking, separation, and progressive collapse, which are critical for evaluating demolition safety, Grunwald, et al. (2018). The model reproduced the geometry of precast girders, cast‑in‑ place slabs, and diaphragms. Internal tendons were represented with initial prestress and long‑term losses. External cables (PTE/PTE2) were modeled as link elements with assigned prestress; CFRP strips were modeled as 3D components with manufacturer properties and interface springs to account for bond behavior. The steel platform designed for the uplift operation was modeled including principal longitudinal beams, end beams, transverse diaphragms, and pedestals (Figure 5).

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Fig. 5. Steel platform numerical model: (a) frame and pedestals; (b) connection details.

Boundary conditions were tailored to each demolition method. For Method 1, jack-up towers and steel platform stiffness were modeled explicitly, including connection details such as steel plates and bolts, included as implicit springs. For Methods 2, attention focused on bearing pads represented by 3D non-linear springs to capture sliding and rotations, enabling realistic deck/support interaction during sequential removal. Method 3 extended the model to include piers, foundations, and soil layers for lateral load and ground‑interaction assessment. Damage states were integrated by deactivating inactive tendons and reducing spring’s stiffness in degraded areas. Cold joints between precast and cast‑in‑place elements were represented by compression‑only interface s, preventing tensile force transfer across diaphragms and girders (Figure 6).

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