Experimental study of a three-storey concrete frame structure with smooth bars under cyclic lateral loading
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Experimental study of a three‑storey concrete frame structure with smooth bars under cyclic lateral loading X. Palios1 · E. Strepelias1 · N. Stathas1 · M. N. Fardis1 · S. Bousias1 · C. Z. Chrysostomou2 · N. Kyriakides2 Received: 24 March 2019 / Accepted: 29 June 2020 © Springer Nature B.V. 2020
Abstract Past lateral cyclic or seismic tests of concrete frames with smooth bars in columns are very few and limited as far as the test structure’s size and geometry are concerned; moreover, they have not focused on the effect of detailing and lap-splicing of such bars on local and global behaviour. To help fill this knowledge gap with new data, the paper presents the cyclic lateral load test of a 2:3-scale three-storey, one-by-two-bay, strong beam-weak column RC frame, focusing on the effects of the column’s smooth bars and of their detailing on local and global behaviour. Slippage of bars caused concentration of column deformations in flexural cracks at the top and base sections and gave to the global hysteresis loops a shape typical of bond-slip behaviour, but without cyclic strength decay. Despite chord rotation demands of up to 0.055 rads and storey drifts of almost 5%, damage was limited and had nothing to do with the use of smooth bars in the columns. Despite the important role of bar slippage for the response, bar strains show that wherever the surrounding concrete was in compression, column bars were in compression as well. Lap splices at and/or FRP wrapping of column end regions did not have systematic effects on column behaviour. Overall, no adverse effect of the use of smooth bars was identified. Keywords Plain bars · Existing structures · Cyclic loading · Retrofitting reinforced concrete structures
1 Introduction Smooth (plain) bars are not used anymore as primary reinforcement of new concrete structures. The codes of most countries have banned them from such a use long since. Nonetheless, being common in old structures which are assessed for retrofitting, they enjoy the renewed interest of the structural engineering community. However, still little is known about the performance of structures with smooth bars in strong earthquakes. Lack of knowledge is not only due to the rarity of such extreme events. In the heyday of smooth bars, systematic research of the modern type and scale was unknown to * S. Bousias [email protected] Extended author information available on the last page of the article
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Bulletin of Earthquake Engineering
structural engineering. Early works by Bach and Graf (1909, 1910, 1911a, b) and Scheit and Wawrziniok (1912) seem today trivial demonstrations of the effectiveness of hooked smooth bars. Later studies (Wernisch (1937), Mylrea (1948), Rehm (1969), Edwards and Yannopoulos (1979)) were motivated by the emergence of ribbed (deformed) bars as a more advanced alternative; smooth bars were studied just to show that they were inferior to ribbed bars. The gap in knowledge is to a good extent being filled nowadays, thanks to the renewed interest in smooth bars b
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