<b>Size effect in shear strength of prestressed beams</b>

<p dir="ltr">Extensive research on the relationship between the height (h) or depth (d) of a beam without and with shear reinforcement and its normalized shear strength resulted in the implementation of a size effect factor in the design codes for estimation of shear strength of beams. A great deal of experimental work conducted so far on the unit shear strength of reinforced concrete beams of different properties has reached the same conclusion: a reduced unit shear strength of reinforced concrete beams without shear reinforcement (stirrups), compared to smaller depth beams of the same properties. The reduction can go up to 50% (<a href="#Sneed" target="_blank">Sneed and Ramirez</a>, 2010). However, the same consensus has not been reached for prestressed concrete (PC) beams. The <a href="#Databank" target="_blank">ACI-DAfStb databases</a> 2015 with shear tests for evaluating relationships for the shear design of structural concrete members without and with stirrups, comprising 1258 tests conducted into 4 different groups of beams: RC beams with and without shear reinforcement and PC beams with and without shear reinforcement is re-examined in this thesis regarding the size effect of prestressed members.</p><p dir="ltr">The approaches to calculate shear capacity in <a href="#ACI2025" target="_blank">ACI 318-25</a>, and the 2004 edition of <a href="#Eurocode2" target="_blank">Eurocode 2</a> are compared and contrasted in this thesis in the case of PC beams. The motivation for this comparison is that in ACI 318-25, the size effect is not considered in prestressed concrete members, whereas the approach of shear strength estimation in EC-2 2004 is unified for RC and PC beams, including a size effect. The results will be compared to evaluate how the approaches to the size effect impact the shear design of the pretensioned beams, and in particular if there are differences in the shear capacity. Of particular interest in this study is to attempt to elucidate whether there is a need to consider possible changes in ACI318-25 to include a size effect in the shear design of PC beams.</p>