Pullout tests on the connection to an existing foundation of a steel warehouse rebuilt after the 2012 Emilia (Italy) earthquakes

Fabio Minghini,Nerio Tullini,Francesco Lippi,Walter Salvatore

doi:10.1007/s10518-021-01127-8

Fabio Minghini, Nerio Tullini + Show 2 more

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https://doi.org/10.1007/s10518-021-01127-8

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Abstract

The tests described in this paper were aimed at evaluating the tensile capacity of the anchorages connecting an automated pallet warehouse with an existing RC foundation. The warehouse is a new steel structure erected in the place of a previous warehouse collapsed due to the Emilia earthquake, but whose foundation remained undamaged. The investigated fastening consists of 10 post-installed, bonded threaded rods with diameter (d) and embedment depth (hef) of 20 and 500 mm, respectively. Neither anchor arrangement nor embedment depth (hef > 20d) was covered by current standards for fastening design. To reproduce the in-situ actual conditions of the fastening, an unconfined test configuration was used. The maximum loads achieved were more than 3 times greater than the seismic demand for the fastening. The tests highlighted the crucial role played by the reinforcing steel which was present in the foundation. Concrete-related failure mechanisms, such as the combined pullout and concrete cone failure mechanism typical of bonded anchors, were not activated. The observed crack patterns rather suggest the onset of a flexural failure mechanism of the concrete slab. This feature is confirmed by analytical calculations showing that, at the maximum loads achieved in the tests, the top reinforcement was likely to be yielded. In six preliminary unconfined tension tests on single anchors, steel rod failure was achieved, associated with limited cracking of the concrete surface in proximity of the anchor.

Highlights

1.1 Problem statementIn Italy, a strong impulse to use heavy-load anchors in concrete came immediately after the 2012 Emilia seismic sequence
Structural interventions were massively aimed at preventing relative displacements between the various monolithic elements using more traditional and cheaper techniques. These techniques were generally based on steel plates or profiles fastened to concrete by mechanical or adhesively bonded anchors. This led to an extensive use of post-installed anchors throughout a large part of Northern Italy (Minghini and Tullini 2021) and raised the issue of investigating their response in precast Reinforced Concrete (RC) structures subjected to cyclic loads (Dal Lago et al 2017)
The main results of tests on single anchors and anchor groups are presented in Sects. 4.1 and 4.2, respectively

Summary

Introduction

In Italy, a strong impulse to use heavy-load anchors in concrete came immediately after the 2012 Emilia seismic sequence Those earthquake events draw attention to the serious deficiencies of precast Reinforced Concrete (RC) buildings not conceived to resist seismic loads (Bournas et al 2014; Braga et al 2014; Minghini et al 2016; Buratti et al 2017). Structural interventions were massively aimed at preventing relative displacements between the various monolithic elements using more traditional and cheaper techniques These techniques were generally based on steel plates or profiles fastened to concrete by mechanical or adhesively bonded anchors. This led to an extensive use of post-installed anchors throughout a large part of Northern Italy (Minghini and Tullini 2021) and raised the issue of investigating their response in precast RC structures subjected to cyclic loads (Dal Lago et al 2017)

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