SHEAR DESIGN AND ASSESSMENT OF REINFORCED AND PRESTRESSED 1 CONCRETE BEAMS BASED ON A MECHANICAL MODEL 2 Antonio Marí 1 , Jesús M. Bairán 2 , Antoni Cladera 3 , and Eva Oller 4 3 Corresponding autor: Antonio Marí. antonio.mari@upc.edu 4 5 Abstract 6 Safe and economical design and assessment of reinforced (RC) and prestressed concrete 7 (PC) beams requires the availability of accurate but simple formulations which adequately 8 capture the structural response. In this paper, a mechanical model for the prediction of the 9 shear-flexural strength of PC and RC members with rectangular, I or T sections, with and 10 without shear reinforcement, is presented. The model is based on the principles of concrete 11 mechanics and on assumptions supported by the observed experimental behavior and by the 12 results of refined numerical models. Compact, simple and accurate expressions are derived for 13 design and verification of the shear strength, which incorporate the most relevant shear 14 transfer actions. Excellent agreement between the predictions of the model and the results of 15 the recently published ACI-DAfStb databases, including more than 1287 tests on RC and PC 16 beams with and without stirrups, has been observed. The theory behind the model provides 17 consistent explanations for many aspects related to the shear response that are not clearly 18 explained by current code formulations, making it a very helpful tool for daily engineering 19 practice. 20 1 Professor, Construction Engineering Department, Universitat Politècnica de Catalunya, Jordi Girona 1-3, C-1 201, 08034 Barcelona (Spain), antonio.mari@upc.edu 2 Associate Professor, Construction Engineering Department, Universitat Politècnica de Catalunya, Jordi Girona 1-3, C-1 201, 08034 Barcelona (Spain), jesus.miguel.bairan@upc.edu 3 Associate Professor, Physics Department, Universitat de les Illes Balears, Ctra. Valldemossa km 7.5, 07122 Palma de Mallorca (Spain), antoni.cladera@uib.es 4 Assistant Professor, Construction Engineering Department, Universitat Politècnica de Catalunya, Jordi Girona 1-3, C-1 201, 08034 Barcelona (Spain), eva.oller@upc.edu Manuscript Click here to download Manuscript STENG-4531_re-re- reviewed manuscript.docx