## 1 Introduction  
In the design of bridge structures, the function of expansion joints is to provide a good connection between the bridge deck and pavement or bridge deck and bridge deck during free expansion [1; 2]. The expansion joint is the weak part of a bridge structure [3]. For steel box girder bridges, the concrete in the transition strips of expansion joints bears the worst wheel load shear load along the layered points between the pavement and the steel deck under a driving load, especially under acceleration/braking loads [4].  
Cracking occurs in most of the concrete in the transition zone of expansion joints in operating bridges, which has a negative impact on the service life of bridges [5; 6]. [PERSON] et al. [7] investigated bridge expansion joints in northeastern Massachusetts, USA, and evaluated their performances. It was found that most expansion joints had service lives of less than four years, and the concrete cracking in the transition zone was severe. The Su-Tong Yangtze River Highway Bridge in China was completed and opened to traffic in May 2008. During the past 10 years, its expansion joints have been repaired many times. In July 2015, due to the damage of the expansion joint of the north-south approach bridge, its maintenance and construction period was 40 days, which was the longest construction period since the bridge was opened to traffic. [PERSON] et al. [8] investigated the damage of expansion joints of bridges in Australia. The conclusion was that the cracking of expansion joint concrete was severe. The cracking problem of bridge expansion joints has become one of the most significant structural defects of these systems [9; 10].  
To solve the problem of frequent cracking of the expansion joint concrete, the feasibility of applying different kinds of high-performance concretes in expansion joints from the perspective of the material properties was studied by researchers [11]. [PERSON] et al. [12] studied the feasibility of the application of a polymer-modified asphalt mixture in expansion joints. Four polymer-modified asphalt mixture expansion joints were installed in two bridges. Ultra-high performance concrete, with high compressive strengths, high tensile strengths, low creep, and good durability, provided one of the solutions for the connection design and construction of prefabricated bridge systems. [PERSON] et al. [13] reported the engineering application of ultra-high performance concrete in bridge expansion joints in the United States, Canada, and other countries.  
These studies provide some choices for improving the damage of bridge expansion joints. However, the occurrence of cracks cannot be fundamentally eliminated, and the problem of premature occurrence of diseases of the concrete in transition zones still exists [14].  
Engineered cementitious composite (ECC) possesses a tensile strain capacity of more than 3% (300-500-fold higher than that of ordinary concrete) during the uniaxial tension phase due to closely spaced multiple cracks with crack widths that are usually no more than 100 \(\upmu\)m. Under severe flexural loading, the deformation capacity of ECC plates is similar to that of metal material. It exhibits excellent application potential [15; 16]. At present, ECC has been initially applied to bridge deck repairs, steel deck pavements, and bridge reinforcement engineering with good results [17; 18].  
Based on the excellent performance of ECC and the previous research of our team, ECC was used as the material of the expansion joint transition zone in this study. Considering the worst-case-scenario shear action, the shear behavior of the ECC in the transition zone was studied. This study will promote the research results of new ECC materials in practical engineering applications.