# Influence of Lower Lateral Bracing on the Seismic Pounding Damage to Slab-On-Girder Steel Bridges
## 1 Introduction
Therefore, it is necessary to further clarify the influence of lower lateral bracing on the seismic pounding damage to slab-on-girder steel bridges. Especially after the Kumamoto earthquake, the seismic performance of and damage to the lower lateral bracing of the slab-on-girder steel bridges have been paid attention to by scholars. [PERSON] et al. [14], for example, studied the seismic-induced pounding effect on bridge beams and piers by analyzing the dynamic response of a three-span simply supported steel girder bridge. [PERSON] et al. [15] evaluated the pounding interaction between bridge abutments and steel beams under nonuniform seismic excitation. [PERSON] et al. [16] discussed the damage survey of the Tawarayama Bridge affected by the Kumamoto earthquake, especially about its lower lateral bracing's severe damage by the earthquake. [PERSON] and [PERSON] [17] found that the bottom plate of the end steel beam will rotate inward under the action of an earthquake and damage will occur at the connection with lower lateral bracing. These studies considered the lower lateral bracing member in the bridge models. However, none of these studies focused on the details exhibited by the steel bridges' seismic damage. The above seismic pounding studies of steel bridges are insufficient, especially ignoring the precise geometric dimensions and connection relationship between steel beams and lower lateral bracings, which makes it difficult to explain the seismic damage to steel bridges and to clarify the control effect of the lower lateral bracings on the damage to the steel beams. Therefore, some challenges remain for slab-on-girder steel bridges: (1) special seismic damage to steel bridges needs to be studied, such as steel beam webs' lateral deformation and lower lateral bracings' vertical failure, according to lessons learned from the Kumamoto earthquake; (2) the transverse stiffness of steel beams is low and uneven along the beam height; thus, their lateral damage may be serious under seismic bounding, and the damage scope is not clear; (3) the effectiveness of the lateral bracings has not been clarified for steel beams, especially considering their encounter plastic and buckling deformation; (4) since the seismic-induced bounding process of steel bridges involves the elastoplastic of steel, buckling of steel components, and contact of keys (i.e., material, geometry, and boundary nonlinearity), multiscale refined numerical simulation methods must be adopted. Therefore, it is necessary to further study the seismic response and influence of lower lateral bracing for slab-on-girder steel bridges. To solve the above problems, the influence of lower lateral bracing on the seismic bounding damage to slab-on-girder steel bridges is studied in detail by using a refined finite element model. The main differences between the aim of this paper and other studies are as follows: (1) the role of lower lateral bracing in the case of the seismic bounding of slab-on-girder steel bridge is analyzed, which has been ignored or oversimplified in previous studies; (2) possible failure modes and engineering design recommendations for the lower lateral bracing are further proposed. This paper is organized as follows. Section 1 introduces the background and motivations. Section 2 illustrates the modeling method of the bridge's numerical model and the selection of the ground motions. In Section 3, the simulation results of the seismic-induced bounding failure of the steel bridge are presented and discussed in detail. The contribution of lower lateral bracing to the seismic performance of steel beams is discussed in Section 4. Finally, in Section 5, the main conclusions are drawn.