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The increased volume of heavy vehicles and use of de-icing agents on concrete bridge decks accelerates the deterioration of these structures. Therefore, the rapid replacement of these structures has attracted considerable attention, with prefabricated bridges being the preferred option. Conventionally, horizontal shear connections between girders and precast decks have incorporated rebar stirrup shear connectors. Although effective for initial construction, this method renders dismantling of aged decks complex, because rebar connectors are fully embedded within girders. This study introduced an embedded separable shear connector that minimizes deck-breaking and facilitates easy reinstallation by the simple separation of the deck from the girder. Horizontal shear and flexural tests on composite girders and comparisons with various design codes were conducted to evaluate this connector. The results of horizontal shear tests confirmed that securing sufficient embedment depth is necessary to prevent the pull-out failure of shear connectors. Additionally, prestressed concrete composite girder flexural tests with improved design verified that the detachable shear connectors exhibited an approximately 60% improvement in flexural performance compared with conventional reinforcement shear connectors. Full article

The construction industry is a challenging field for the application of robots. In particular, bridge construction, which involves many tasks at great heights, makes it difficult to implement robots. To construct a bridge, it is necessary to build numerous piers that can support the bridge deck. Pier construction involves a series of tasks including rebar connection, formwork installation, concrete pouring, formwork dismantling, and formwork reinstallation. These activities require working at heights, presenting a significant risk of falls. If bridge construction could be performed remotely using robots instead of relying on human labor, it would greatly contribute to the safety of bridge construction. This paper proposes a multi-robot system capable of remote operation and automation for rebar structure connection, concrete pouring, and concrete vibrating tasks in pier construction. The proposed multi-robot system for pier construction is composed of three robot systems. Each robot system consists of a robot arm mounted on a mobile robot that can move along rails. And to apply the proposed system to a construction site, it is essential to implement a compliance control algorithm that adapts to external forces. In this paper, we propose an admittance control that takes into account the weight of the tool for the compliance control of the proposed robot, which performs tasks by switching between various construction tools of different weights. Furthermore, we propose a synchronization control method for the multi-robot system to connect reinforcing structures. We validated the proposed algorithm through simulation. Furthermore, we developed a prototype of the proposed system to verify the feasibility of the suggested hardware design and control. Full article