# Transition Effects in Bridge Structures and Their Possible Reduction Using Recycled Materials
## 5 Detailed Overview
### Engineering Aspect
The fundamental structural solutions for these bridges are decks integrated with abutments based on shallow direct foundations, solid abutments, or partially integrated ones. An integral bridge is a specific type of bridge structure designed to collaborate with an embankment in a way that minimizes the negative effects of the transition effect. Figure 5 shows an example of an integral bridge. In such cases, the embankment soil is often reinforced. The longitudinal forces arising from the thermal expansion or contraction of the bridge deck are transmitted to the abutments and to the soil behind the abutment [94]. In the design assumption, the abutment does not necessarily have to absorb the entire horizontal forces due to thermal effects, as part of them will be transferred to the embankment, which will be integrated into the cooperation [94]. When calculating the ground reactions behind the abutment, the total length of the bridge is significant, determining the extent of its expansion or contraction due to temperature changes. However, the number of intermediate supports has no effect on the magnitude of the bridge's expansion or contraction, and it does not influence the size of the ground reaction [62]. In integral bridges, forming a slip plane to stimulate movements in the upper layers of the embankment soil is essential to minimize vertical displacements that affect the magnitude of the transition effect [62]. Intermediate supports, typically reinforced concrete, can be articulated on the foundation or based on one or several rows of piles. Spans for structures with integrated supports are usually around 60 m, sometimes reaching 80-100 m. The number of pairs can vary, and the lengths of the longest integral bridges can exceed 350 m (Happy Hollow Bridge, Hickman County, TN, USA). The challenge in evaluating existing structures and applying them lies in the interaction between the bridge and embankment soil. In many cases, this interaction is misunderstood due to the inherent nonlinear behavior of soil during what is known as operational interaction, significantly altering stresses in the embankment soil due to abutment displacements [87]. A step toward a better understanding this phenomenon involves interpreting the support and embankment soil state at the beginning of dynamic excitation based on earlier interactions during operation and assessing the stiffness and strength of the existing cushioning properties of the supports under dynamic loads [87]. The typical geometry of an integral support and typical embankment soil are studied using fully constrained simulations, assuming a viscoelastic-plastic stress model for the soil (coupled approach) under static and dynamic loads [87]. Integral bridges are designed with the assumption that only minor settlements of the end supports of the structure and embankments are permissible for using this solution in a given location. It is essential to note that this assumption significantly restricts the application of integral bridges. The connection of the bridge structure with the embankment, depending on the length of the structure, the shape of the space under the structure, the type of obstacle, and the terrain conditions may be made through different solutions. For example, these may be: massive integral abutments (Figure 6a), integral wall abutments (Figure 6b,f), integral box frame walls abutment (Figure 6c) or pillars support (Figure 6d,e). A semi-integral solution can also  
Figure 5: Three-dimensional model of an example integral bridge. be used with span overhang and placement in the embankment (Figure 6e,f) [21, 48]. The stability of mutual interactions should be ensured, especially in bridge structures where elastic deformations of supports are used to accommodate the elongation of load-bearing structures [21, 22]. When entering a bridge, a vehicle must cross a transition zone. During its design, engineers must consider that the road or rail and the bridge itself may have different mechanical properties, such as stiffness, density, and Young's modulus.