Load‐path modeling of pier diaphragms under vertical shear in concrete box‐girder bridges

Abstract

Pier diaphragms are usually adopted in concrete box girder bridges to transmit shear forces from the webs to the bearings. The pier diaphragm under vertical shear acts as a side‐shearing loaded deep beam that is rarely studied in the literature. Through the load‐path modeling, this paper provides an analytical method for the design of pier diaphragms under vertical shear in concrete box‐girder bridges. Explicit equations are derived for the direct calculation of transverse tension forces in the pier diaphragms, which are critical for the determination of the amount of transverse reinforcement. Further comparative studies in this paper show that: (a) the side‐shearing loaded deep beam differs greatly with the top‐loaded beam in the aspect of elastic internal force distribution when the span‐to‐depth ratio of the diaphragm section is less than 1; (b) the proposed quantitative strut‐and‐tie models agree well with the elastic internal force distribution in the pier diaphragms with various configurations; and (c) the commonly used “direct‐strut model” is acceptable for the design of pier diaphragms with span‐to‐depth ratios greater than 1.5, while it would greatly underestimate the top tension force when the span‐to‐depth ratio is less than 1 (referred to as the “ultra‐deep member”).

Construction of strut‐and‐tie models for members under complex stress states based on topology optimization

“…To introduce the STM method into engineering design, the construction of STM is a key problem that needs to be solved urgently 12 . The main methods of constructing STM are: load path method, 13 elastic stress analysis method 14 and topology optimization method 15 . Among them, the load path method connects the resultant force of the applied force and the support with smooth streamlines to reflect the force transmission path and establish the STM accordingly.…”

Optimization-based strut-and-tie model generation for reinforced concrete structures under multiple load conditions

“…The simple implementation of this method and the resulting safe designs are preferred characteristics in practice. However, there are still some difficulties in applying the STM method, such as, finding suitable truss-like models [48,25,19,18], determining accurate safety factors [42,33], and considering complex dynamic loadings [37]. Some challenges in STM have been summarized in Tjhin and Kuchma [43].…”