PSI - Issue 84

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

985

These girders are post- tensioned with 24 parabolic tendons (Figure 3). Longitudinal deck post‑tensioning passes through the slabs and the girder top flanges. Five tendons post‑tension the intermediate diaphragms and one tendon post‑tensions each end diaphr agm.

Fig. 3. Numerical model: ordinary reinforcement (red) and post-tensioning tendons (blue).

2.1. Damage state Over decades of service, the Champlain Bridge experienced significant deterioration due to harsh environmental exposure and the use of de-icing salts. Inspection campaigns revealed progressive losses of tendon strands and widespread cracking, particularly concentrated in the edge girders, which were more vulnerable to chloride penetration and freeze-thaw cycles. In several spans, the degradation was severe enough to compromise the continuity of prestressing forces, reducing the deck’s stiffness and overall load-carrying capacity. These findings identified certain spans as critical, requiring detailed structural analysis to ensure their integrity during demolition operations, especially under complex scenarios such as uplift or induced collapse. To maintain safety during service life, several retrofits were installed: • External post-tensioning systems (PTE and PTE2) installed along selected girders to supplement lost prestress and improve load capacity (Figure 4, a). • Carbon Fiber Reinforced Polymer (CFRP) strips bonded to diaphragms and girders for local flexural reinforcement and crack mitigation (Figure 4, b). • Steel truss assemblies, such as the Modular Truss (TM) and Queen Post (QP) systems, introduced to share loads and reduce stresses in degraded girders. • Localized slab supports and diaphragm strengthening, aimed at improving transverse load distribution and prevent premature failure. 2.2. External Strengthening

(a)

(b)

Fig. 4. External strengthening in the numerical model: (a) External post‑tensioning cable layout and anchorage zones; (b) CFRP strips on diaphragms/girders and modeled interfaces.