Influence of Materials Knowledge Level on the Assessment of the Characteristic Value of the Shear Strength of Existing RC Beams
This study deals with the assessment of the shear strength characteristic value (V rck ) limited by the concrete strut crushing for existing reinforced concrete (RC) beams on the base of the available material data. A procedure to determine V rck is presented and applied to two existing RC beams extracted from an old structure built in the early 1900s. This procedure requires: (i) an analytical or numerical model for the beam shear strength, (ii) mean and standard deviation values for each uncertain basic variable and (iii) a proper formulation for the tolerance factor depending on amount of data, assumed fractile and given confidence level. The shear strength model adopted in this study is the one proposed by the Italian Code NTC 2008 for beams with transversal steel reinforcement. Several non-destructive tests (namely, rebound and sonic tests) and destructive tests on concrete were performed, and the experimental outcomes showed a great variability of the compressive strength along the same beam, as usual for many old concretes. For that reason, V rck values for each beam were calculated assuming different knowledge levels about the concrete compressive strength. Each level of knowledge is defined taking into account a different combination of available data about the compressive strength carried out from destructive tests. A comparison among the V rck values obtained for each knowledge level is shown to draw useful considerations about the beam shear strength assessment based on materials test data.
KeywordsExisting RC structures Characteristic value Capacity assessment
This work was partially supported by the Italian Consortium of Laboratories ReLUIS, funded by the Italian Federal Emergency Agency, with partial funding from PE 2015–2018, joint program DPC-ReLUIS. This research is also supported by the Structural Laboratory College of Civil Engineering (Fuzhou University), the Sustainable and Innovative Bridge Engineering Research Center of Fuzhou University (SIBERC) and the International Joint-Lab (Universities of Roma Tre and Fuzhou).
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