Experimental Study on the Behavior of Bolted Joints for UHPC Panels

Abstract

Recently, as the technology of freeform design is developing, the interest in construction techniques and material application are rising up. Typically, metal or concrete are used to fabricate the freeform façade. However, the application of these materials to freeform architecture requires complicated construction process and fabrication. As a result, it cause enormous cost problem. To improve current construction technology and process using conventional materials, ultra-high performance concrete (UHPC) can be effective alternative materials for freeform architects due to the high level of flow at placing time. Moreover, UHPC has high compressive strength, tensile strength with fibers, and outstanding impact resistance. However, material cost of UHPC is very expensive to be constructed in comparison with typical material. High construction cost can be compensated by other applications such as architectural finishing rather than structural components. By using precast panel, cost of fabrication will be decreased in comparison with cast-in-place. Also, precast UHPC requires efficient assemblage method by bolted connections. Therefore, cost of placement can be decreased by simple bolted joints. However, research on the bolted joints for UHPC panels is not enough yet. This paper investigates structural behavior of single bolted connections and multi bolted connections to identify main failure mechanisms of bolted joints of UHPC panels. This paper performed a series of experimental program of the bolted joints for UHPC panels through direct tensile tests, especially focused on the relationship between the failure modes, strengths and stress distribution with the variables of the specimen thickness, width and edge distance. Based on the analysis results, some design procedure for predicting ultimate load are proposed by using stress concentration factor and work method. The proposed design procedure is capable of predicting the ultimate load and failure modes of joint well.