Iron based shape memory alloys (Fe-SMA) have recently been used as active flexural strengthening material for reinforced concrete (RC) beams. Fe-SMAs are characterized by a shape memory effect (SME) which allows the recovery of previously induced plastic deformations through heating. If these deformations are restrained a recovery stress is generated by the SME. This recovery stress can be used to prestress a SMA applied as a strengthening material. This paper investigates the performance and the load deformation behavior of RC beams strengthened with mechanical end anchored unbonded Fe-SMA strips activated by sequentially infrared heating. The performance of a single loop loaded and a double loop loaded SMA strengthened RC beam are compared to an un-strengthened beam and a reference beam strengthened with commercially available structural steel. In these tests the SMA strengthened beam had the highest cracking load and the highest ultimate load. It is shown that the serviceability behavior of a concrete beam can be improved by a second thermal activation. The sequential heating procedure causes different temperature and stress states during activation along the SMA strip that have not been researched previously. The possible effect of this different temperature and stress states on metal lattice phase transformation is modeled and discussed. Moreover the role of the martensitic transformation during the cooling process on leveling the inhomogeneity of phase state in the overheated section is pointed out.

Post‐installed fastening systems are essential in structural engineering nowadays. Triggered by the increasing popularity of high strength concrete (HSC) and ultra‐high performance concrete (UHPC), fastening in these basements is more and more frequently applied. This inevitably leads to the question of the applicability of conventional fastening systems and the corresponding design concepts with concrete showing a compressive strength of up to 200 N/mm². According to EAD 330232‐00‐0601, mechanical fasteners have to be placed in predrilled holes in compacted reinforced or unreinforced concrete without fibers with strength classes in the range of C20/25 to C50/60 in compliance with EN 206. This means that concrete strength class C50/60 also provides the reference for higher concrete strength; the impact of fibers and accompanying increase of concrete ductility is also excluded. Within the framework of this contribution it is intended to analyze the following aspects: (a) proof of applicability of various fastening systems in unreinforced and fiber‐reinforced high strength concrete via experimental investigations and (b) making a statement regarding the currently valid European Assessment Document and provide experimental background for this issue.

Innovative drilling methods gain importance in the field of post‐installed fasteners. For this reason, users, customers and manufacturers demand methods other than the standard drilling procedure of hammer drilling, as they are hollow drilling with included cleaning and diamond drilling without emitting drill dust. One open question regarding these drilling methods is the equivalence of the behavior under the conditions of cracked concrete over the entire lifetime. These conditions are typically tested in the crack movement test, which simulates the real behavior of a fastener in cracked concrete over a designed lifetime of 50 years. In this contribution, the example of a post‐installed mechanical bolt anchor is used to explain how a difference in the behavior is a consequence of different drilling methods in noncracked concrete, in cracked concrete and in cracked concrete in which the crack is cycled. Additionally, it is observed that the behavior in the crack cycling test is significantly influenced by the drilling method.