# Evaluation of Horizontal Shear Performance of Composite Girders Using Separable Shear Connectors
## 1 Introduction  
The increased traffic volume of heavy vehicles, combined with the use of de-icing agents on bridge structures during winters, considerably accelerates the deterioration and aging of concrete decks. Considering the maintenance and life cycle costs (LCC) of bridges, adopting modular construction techniques to replace these aged decks efficiently is imperative. Prefabricated bridges have attracted considerable attention. Most studies on precast concrete decks have focused on addressing usability problems, such as cracking and leakage at longitudinal joints (e.g., prestressing or loop joints) between decks. However, limited studies have focused on applying prefabricated concepts to horizontal shear connections between concrete girders and decks. In composite bridges featuring concrete decks, shear connectors resist the horizontal shear caused by bending moments, which is essential for the composite action between the girder and the deck. Generally, girder bridges incorporate U-shaped shear reinforcements as shear connectors. However, the rapid aging of and damage to these structures necessitate replacing the deck before the girders. In particular, if complications arise during deck replacement, then the entire bridge is to be demolished and reconstructed, including girders with a sufficient remaining lifespan. Addressing the recurring replacement of damaged and aged decks throughout the service life of girders can considerably extend the lifespan of bridges and enhance their economic efficiency. Replacing an aged cast-in-place concrete deck with a precast deck is a common approach for bridge repair or renovation (Figure 1). Figure 1a depicts a photograph of cutting a deteriorated concrete deck with a wheel saw, Figure 1b illustrates the removal of existing rebar shear connectors by using an oxygen cutter, Figure 1c depicts the installation of new rebar shear connectors using chemical anchors on the girder and placement of a precast deck, and finally, Figure 1d displays the completion of the replacement with a new precast deck by casting and curing non-shrink mortar in shear pockets. The first step in the removal process involves cutting and removing the deck between girders using wheel saws or diamond wire saws. Subsequently, the composite deck atop the girders, which is bonded by shear connectors, is dismantled using breakers or waterjet equipment. The demolition process is more challenging for precast decks integrated using high-strength non-shrink mortar through shear pockets than that for cast-in-place decks. Furthermore, the use of breakers to demolish concrete decks generates considerable noise and fine dust, exacerbating the environmental damage in urban settings. The extended duration required for construction work prolongs the period of traffic control until reinstallation is complete, causing considerable inconvenience and economic losses to the public. In this process, shear connectors are frequently bent by the impact of breakers, rendering their reuse complex. Consequently, all rebar shear connectors should be cut and new connectors should be installed atop the girders by using chemical anchors. Damage to the shear connectors can be minimized by using waterjet equipment for the deck demolition. However, this method is time-consuming, expensive, and results in environmental pollution because of the substantial volume of concrete sludge produced by extensive water use. Therefore, the development of separable shear connectors that facilitate the easy separation and replacement of the deck from the girder is critical for enhancing the reconstructability of aged decks. Numerous researchers, including [PERSON] and [PERSON] [1], have evaluated the horizontal shear strength of composite concrete beams and decks. Based on the results of composite beam tests, [PERSON] and [PERSON] [1] developed horizontal shear-strength equations for both normal and lightweight concrete.