1. Introduction

In the field of civil engineering, and more specifically in the field of reinforced concrete structures (BA), for the design of massive elements with low flexural stress such as corbels, beams and plates with abrupt changes in their section, girders or flag sails, for example, for the design of massive elements with low flexural stress, for the design of massive elements, the tie-rod method (MBT) can be preferred over conventional reinforcement calculation algorithms that rely on flexible resistance. to the various limit states (for example Wood-Armor or Capra- Maury [Capra et al, 1978]).

MBT remains a suitable alternative for the design of concrete structures with elastic or plastic behavior whose application framework is well defined in concrete structure design codes such as Eurocodes (§5.6.4 and 6.5 of [EN 1992-1-1]).

Command CALC_BT presents a semi-automatic method for implementing MBT, which is consistent with [EN 1992-1-1], which recalls that adapted tie rod models can be defined from stress isostatics and stress distributions obtained using linear elasticity theory. As such, the macro-control uses the directions of the main stresses, \({\mathrm{\sigma }}_{I}\) and \({\mathrm{\sigma }}_{\mathit{III}}\), for the rods and the tie rods, the directions of the main stresses, obtained from a preliminary calculation on a finite element model of the structural element studied.