ABSTRACT
In this paper, the applicability of the constant life diagram (CLD) methodology for fatigue strengthening of metallic members is examined. The CLD methodology is a method that uses the combined effect of alternating stress, mean stress and material properties to predict the material life-time under high-cycle fatigue loading. The method could be used most efficiently to improve resistance to crack initiation in ‘safe-life’ members, which is, in fact, a preventive fatigue strengthening approach (Ghafoori et al. 2015a). Furthermore, an innovative pre-stressed un-bonded reinforcement (PUR) system is presented. The advantages of the developed PUR system are: applicable to unsmooth surfaces (e.g., riveted or corroded), fast on-site installation (i.e., no glue and no surface preparation), no damage on metallic member (no weld, hole or grinding) and adjustable carbon fiber-reinforced polymer (CFRP) pre-stress level, as shown in Figure 1. Different components of the retrofit system: (a) the pre-stressing chair includes a saddle that pushes the CFRP away from the beam and (b) once the required eccentricity is reached, two column plates are placed between the CFRP plates and the saddle. More details about the design of the trapezoidal PUR system are described in (<xref ref-type="bibr" rid="ref61_1">Ghafoori and Motavalli 2015</xref>). https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig61_1.tif"/>
The system can be easily disassembled and removed, if necessary, which makes it suitable for historical bridges as a temporary or permanent retrofit technique. Lastly, this paper presents details about fatigue strengthening of riveted girders in a 120-year-old railway (wrought iron) bridge using the PUR system (see Fig. 2) such that the requirements of the CLD approach are fulfilled. A strengthened crossbeam of Münchenstein Railway Bridge. A strain gauge is glued to each CFRP plate and is connected to the wireless sensor network (WSN) system for long-term monitoring of the pre-stress level (<xref ref-type="bibr" rid="ref61_3">Ghafoori et al. 2015b</xref>). https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig61_2.jpg"/>
