## 1 Introduction  
Under the influence of vehicle load and natural environmental erosion, structural damages inevitably occur, which can seriously affect the safety and durability of bridges. Therefore, structural damage identification has become an important part of bridge maintenance and reinforcement. Prefabricated reinforced concrete (RC) bridges have become widely used because of their advantages such as higher quality and shorter construction period, etc. As a typical prefabricated RC bridge, most hinged-slab bridges were built decades ago. According to the structural features of a hinged-slab bridge, hinge joints are the relative weak parts, which are prone to cracks (as shown in Figure 1). According to the investigations of more than 500 bridges for expressways in Jilin Province, the maximum proportion of hinge joint damage was 83.3% on the Changchun-Siping Expressway (in operation since 1996) and the minimum was 11.8% for the Jilin-Jiangmifeng Expressway (in operation since 2011). Hingejoint damage in reinforced concrete bridges widely exists, which will cause single slab bearings and aggravate the overall damage status of the structure. Therefore, it is significant to propose an efficient and accurate damage evaluation method for hinge joints for hinged-slab bridges. In recent decades, structural health monitoring and damage identification, which are based on the dynamic properties of bridges, have been rapidly developed. To measure the dynamic response for structural health monitoring (SHM) accurately and efficiently, [PERSON] et al. [1] developed an intelligent data acquisition system to evaluate the dynamic response performance of bridges using wireless sensor networks in real-time. With the appearance of damage, some changes will take place in modal parameters such as natural frequencies, mode shapes, damping ratios, etc. This feature can be utilized as indicators to identify the location and degree of damage [2; 3; 4; 5]. Researchers also studied damage identification methods based on other identification indicators. For instance, [PERSON] et al. [6] proposed a damage localization approach by axial strain accelerations for truss bridges, and [PERSON] et al. [7] developed a damage detection method through [PERSON]'s [7] damage indicator which was demonstrated superior to the modal parameters. Nevertheless, it cannot effectively analyze the damage of transverse connection components for hinged-slab bridges. In addition, hinge joint damage will lead to the redistribution of lateral load, which has an adverse effect on the bearing capacity of bridges. Some researchers have studied the relationship between lateral load distribution (LLD) and the damage condition of hinge joints. [PERSON] et al. [8] performed a series of diagnostic load tests on damaged westbound and undamaged eastbound prestressed concrete bridges to determine the effects of hinge joint damage on load distribution. Test results showed that westbound bridges were somewhat flexible. Change in load distribution occurred when isolated damage was present. [PERSON] et al. [9] investigated the effect of secondary elements and deck cracking on the LLD of girder bridges. Longitudinal cracking was found to increase the load distribution factor up to 17%, while the influence of transverse cracking was not significant. [PERSON] et al. [10] researched the effect of girder damage on overall load distribution of a typical short-span composite bridge using a grillage method. [PERSON] et al. [11] discovered that live loads were redistributed among the girders due to prestressed CFRP sheets. [PERSON] et al. [12] studied live load distribution factors of an AASHTO Type 3 precast-prestressed girder, which was calculated through finite element method (FEM) and compared with the simplified method prescribed by other codes. Although great achievements have been obtained in the study of LLD under damage conditions of hinge joints, it is limited in qualitative analysis.