# Assessment of Modal Characteristics of Steel-Concrete Composite Grider Bridge with V-Shaped Piers
## 1 Introduction  
With the improvements in bridge construction, the level of infrastructure construction has also made great progress. A variety of beautiful and unique bridge structures have beencreated. The aesthetic requirements of the public with regard to bridges have prompted the use of the special structure of a steel-concrete composite continuous beam with V-shaped piers on a continuous rigid bridge. The superstructure of the bridge adopts a steel-concrete composite structure in which the reinforced concrete slab is under pressure at the top and the steel beam is under tension at the bottom, making full use of the material properties. At the same time, this structure can be constructed quickly, has a low building height, is light, has good structural ductility, can be built in the city without erecting supports, and generates less noise during construction; it not only meets the design specifications, but also has the advantages of both steel and concrete bridges. These benefits fully meet the current social development requirements for building environmental protection [1]. Reinforced concrete structures, on the other hand, continue to predominate in small and medium-span bridges. Research on the adoption of steel bridges for small and medium spans has received a positive response and has important practical significance. The bridge substructure in this paper is a composite of vertical piers and V-shaped piers, with supports at the vertical piers and bolts between the V-shaped piers and the main girder thus forming a unique continuous beam-V-shaped pier continuous rigid structure. It makes the superstructure look slimmer, thus making the shape more beautiful [2]. Steel-concrete composite bridges appeared as early as the last century. In early composite structures, no shear connectors existed, and the concrete slabs were connected to the steel beams mainly by friction and bonding [3]. This design made the steel-concrete composite interface susceptible to slip effects, resulting in damage to the overall structure [4]. Since the 1930s, more and more research has been conducted on steel-concrete composite structures, and many bridges with steel-concrete composite structures have been built in Europe, the United States, and other developed countries. Steel-concrete bridges were rapidly developed in the 1960s, and not only did plasticity theory emerge as the theoretical foundation, but research methods also advanced to the nonlinear spatial level. From small- and medium-span bridges to large-span cable-stayed bridges, steel-concrete composite structures developed significantly in the 1990s [5]. The spacing of traditional steel main girders was increased in France, and the Hopital Bridge was built with only two steel main girders. The structure was easy to build, allowing its material properties to be fully utilized and greatly reducing construction and maintenance costs. This bridge has since become a model for the use of combined steel and concrete structures in the design and construction of short- and medium-span bridges. Many experts and scholars have conducted studies on the slip action of steel-concrete composite structures, and many constructive conclusions have been reached. Several equations are proposed to determine the critical point at which a compressed bottom flange may buckle laterally in an unstable manner, i.e., lateral torsional buckling ([PERSON], [PERSON] et al. [6]). Closed-form solutions for stress, deflection, and slip of box beams under lateral loading were obtained, and the comparison of the analytical results and the experimental results for steel-concrete composite box beams under concentrated loading or uniform loading verified the closed-form solution ([PERSON] et al. [7]).