Title:
Strut-and-Tie Model for Externally Prestressed Concrete Beams
Author(s):
K. H. Tan and A. E. Naaman
Publication:
Structural Journal
Volume:
90
Issue:
6
Appears on pages(s):
683-691
Keywords:
flexural strength; prestressed concrete; prestressing; shear stress; strength; strut-tie model; trusses; Design
DOI:
10.14359/4492
Date:
11/1/1993
Abstract:
A model based on the strut-and-tie method is presented to predict the strength of simply supported, externally prestressed concrete beams subjected to a midspan concentrated load. The model defines a safe domain within which the beam would not collapse under the applied load. It predicts four possible modes of failure, which may be broadly classified into shear-type failure and flexural-type failure. Shear-type failure of the beam is due to the crushing of the diagonal compressive concrete strut or the yielding of the web reinforcement, while flexural-type failure is due to the yielding of the internal longitudinal reinforcement or the yielding of the external prestressing tendons. The actual mode of failure depends on the shear span-to-depth ratio (a/h) of the beam, the ratio of the loading platen width to the beam depth (w/h), the longitudinal and transverse reinforcing indexes (<{omega} sub l >, <{omega} sub v >), the ratios of effective depths of reinforcements to beam depth (d pe/h, d e/h), and the loading path relating the stress in the external prestressing tendons to the failure of externally prestressed concrete beams. The predictions of the model are compared with available test results of prestressed concrete beams with and without external prestressing tendons. Good agreement between the predicted and observed values is obtained.