Performance Assessment of Deck Link Slabs in Multi-Span Bridges: A Case Study of the Plott Creek Bridge

Sandra Villamizar^1*Osama Abdelaleim²Daniel Gomez³Julio Ramirez²Ghadir Haikal^4*

• ¹University of Santiago de Cali, Cali, Colombia
• ²Purdue University, West Lafayette, United States
• ³Universidad del Valle, Cali, Colombia
• ⁴NC State University, Raleigh, United States

The use of link-slab connections in simply supported multi-span bridge decks is a widely adopted strategy to minimize expansion joints, reducing long-term maintenance issues and improving roadway surface quality. Current design practice for debonded link slabs primarily focuses on live loads, assuming the girders behave as simple spans while neglecting the influence of support conditions. The link slab is typically considered in pure bending and designed to accommodate girder end rotation. A bond-breaker material is employed between the top of the girders and the bottom of the link slab to reduce induced stresses and control cracking at the connection region. Within the debonded length, typically set at 5% of each span, the stirrups and shear connectors are removed. Adequate reinforcement is provided to satisfy crack width control at service limit states. Despite these measures, field observations indicate persistent cracking and leakage in link slabs early in service life. Several investigations suggest that temperature gradients and shrinkage effects are primary contributors. Studies have shown that link slabs experience both axial tension and bending, challenging the pure bending assumption. The novelty of this study lies in quantifying the effects of thermal gradients within the simplified design framework, thereby providing engineers with practical metrics to adapt the method for improved accuracy. A numerical evaluation of link slab response is performed using finite element analysis to model the combined effects of traffic loads and vertical temperature gradients. The slabs are analyzed under HL-93 loading and temperature gradients following AASHTO LRFD Bridge Design Specifications. A parametric study examines the influence of girder support conditions and debonded length on link slab performance. The computational results highlight the significant role of temperature gradients and girder support conditions in inducing elevated stresses and promoting cracking at the link slab. The findings emphasize the need to account for these parameters in design to enhance durability and structural performance. Moreover, the applicability of the simplified rotation-based design approach is reaffirmed, with proposed modifications enabling it to capture combined effects of live load and thermal gradients.