# Transition Effects in Bridge Structures and Their Possible Reduction Using Recycled Materials
## 5 Detailed Overview  
### Outline  
Bridge construction history dates back several thousand years [10]. Bridges are an integral part of infrastructure and have played a pivotal role in civilization's development. With technological advancements and heightened demands for durability and safety, engineers increasingly seek for superior solutions and construction materials. Bridges stand among the most significant engineering structures, serving as essential components of transportation infrastructure, facilitating access across natural obstacles like rivers, valleys, and artificial barriers, ensuring convenient and safe passage to human settlements. They form a fundamental factor in societal development by enabling the transportation of goods and people [10; 11; 12; 13; 14; 15].  
Bridge structures must have stability and the necessary load-bearing capacity to meet traffic intensity and load requirements. They must also be durable and safe for users [16; 17]. Hence, the construction materials used must meet stringent strength requirements, including resistance to variable and dynamic loads, corrosion, and weather conditions [16; 17].  
Since the late twentieth century, experts have debated how to repair, renew, and modernize transportation infrastructure in Central Europe [18]. Over the past 25 years, there has been a focus on utilizing modern engineering technologies and decision-making processes to solve typical and regional environmental problems in land transport, especially roads and bridges.  
The transition effect occurs at points where different types of permanent way or pavements are connected, laid on various substrates (e.g., soil subgrade, engineering structures) [19; 20]. This effect is a complex phenomenon, as illustrated in Figure 2, showing the most significant causes of its occurrence, including permanent settlements at abutments \(\delta_{\text{a}}\) (usually smaller) and embankments \(\delta_{\text{e}}\) (usually larger), progressing over time with unequal values for individual elements and with momentary deformations from live loads \(\delta_{\text{s}}\) (deflection of girders, rails, and substrate deformations), causing the rotation of the span \(\varphi_{\text{s}}\). Among the surface-related causes, differences in stiffness between the ballast and ballastless tracks, as well as varying stiffness parameters across the transverse direction, can be listed. They also include the primary geometric irregularities of rails and the inaccurate alignment of the gradeline on and outside the facility. Structural causes include primary geometric irregularities, deformations, settlement, and increased stiffness. Causes related to the substrate involve poor sub-ballast compaction, excessive stiffness differences between sub-ballast and substrate, sub-ballast contamination, and improperly chosen geotextiles. Due to different settlement values at the abutment and embankment, a so-called \"threshold\" is formed, which leads, among other reasons, to additional dynamic loads on the structure and excessive permanent deformations of the surface, amplifying dynamic effects and causing increased wear and tear and damage to pavements, track superstructures, substrates, and structures.  
In order to determine the impact of this effect, the so-called transition zone is distinguished. It is the area where the embankment meets the bridge structure, also referred to as the embankment-abutment interaction zone [21; 22]. It is one of the most critical locations along a road or railway line. Due to the fact that the unit stresses acting on the ground beneath the embankment base are usually smaller than those under the abutment foundation slab of the bridge, the settlements of the abutment will be larger, causing unevenness in the grade line [23]. It is impractical to ensure the same settling for the entire embankment over many kilometers as for the rigid bridge abutment. Hence, a limited zone is defined, where a change in stiffness must occur.