# Conceptual Design of Composite Bridge Sandwich Structure
## 1 Introduction  
Fiber Reinforced Polymers (FRPs) have been widely used in marine, industrial, chemical and civil infrastructure as reinforcing and structural materials with the advantages of being lightweight, high strength, and possessing design flexibility and exceptional corrosion resistance [1, 2, 3]. Modern engineering systems, especially in the areas related to wind turbines [4], space [5], artery bridges [6], and marine atmospheres [7, 8], gradually highlighted the importance of functional necessities. Implementing these functional requirements with materials such as concrete, conventional steel, and other similar materials possess some design challenges. Work on fiber composites with multifunctional, extraordinary-performance, and structural acclimation systems are, therefore, imperative. A sandwich structure is a composite material structure, composed of layers and formed into a dense, lightweight core by adding two rigid, thin skins [9]. Its properties, such as a high strength-to-mass ratio and a high rigidity-to-mass bending ratio, are the most important benefits of these configurations. Due to their extraordinary resistance to corrosion, these are significantly used in aerospace and maritime systems [10, 11, 12]. To examine the flexural and shear behavior of layered sandwich beams (LSB), eight LSB beams made up from GFRP skins and phenolic cores were developed and tested for four-point bending and beam shear. It was examined from the FEA model that the LSBhas increased sectional stability by preventing wrinkling and buckling of the composite skins and indentation failure [13]. [PERSON] and [PERSON] [14] worked on precast concrete sandwich wall panel's flexural behavior with basalt FRP and steel reinforcement. The effect of core density had great importance on the overall behavior of the sandwich structure. [PERSON] worked on the flexural and axial behavior of sandwiched panels with bio-based flax fiber-reinforced polymer skins and various foam core densities [15]. Bridge structures made of GFRP and CFRP composites offer promising features such as exceptional fatigue performance, high strength per unit weight, corrosion resistance, rapid field installation with reduced traffic distractions, and extended bridge live load rankings for bridge substitution [16; 17]. A new survey which was held in 2018 in America shows that FRP composites for infrastructure projects are generally satisfactory and promising [18]. There are two elementary conceptions of bridge structures. Firstly, orthotropic systems consist of pultruded shapes with adhesive bonding and secondly sandwich erections. These are utilized as extension floors in deck-support spans or used as slabs on account of slab bridges. Both the slabs and decks have the advantage, among others, of adaptable thickness in spite of slabs or pultruded decks and would thus be able to be utilized for a lot bigger ranges. They are currently made up of face sheets of GFRP and foam cores or honeycomb. The first case has extra GFRP webs, and these are usually necessary to provide the adequate shear limit of the central core [19]. The inner GFRP webs and honeycomb walls in the core, however, for the upper face sheet provide non-uniform stiffness support, and this is responsible for the debonding of the upper sheet layer from the core under frequent wheel loads. Balsa wood was used as the core in the new Avancon Bridge in Bex, Switzerland, to triumph this disadvantage, i.e., by applying the core with such a material, which is good in shear stress and will provide support to the upper face sheet [20]. The use of fiber-transverse balsa to the face sheets and, therefore, in line with the wheel load direction no longer required internal web reinforcements and provided a high resistance to concentrated wheel loads. In recent years, many existing bridges in the United States are in urgent need of repairing and upgrading. In [21], a new FRP-wrapped balsa wood bridge deck was adopted to replace the damaged steel deck of a bridge in Louisiana.