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What is STM?

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What is STM? - 1. Introduction
Writer admin Date 2020.01.18 Hit 382
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In the past several decades, there has been a major movement in the design methods for reinforced and prestressed concrete towards methods based on equilibrium solutions from the theory of plasticity and related conceptual models (such as strut-tie models). Strut-tie models represent a generation of the truss analogy method for beams. They are powerful and promising tools for designing structural concrete which includes both reinforced and prestressed concrete structures.


In a strut-tie model, the stress distribution is idealized as a static force system consisting of three basic elements: struts, ties, and nodes. A strut-tie model provides truss-like load path. Compressive forces are directed along struts representing compressive stress fields within the concrete. Tensile forces are directed along ties which represent reinforcement. Intersections of struts and ties occur at nodes which are idealizations of areas where internal forces change directions.


Design procedures for reinforced and prestressed concrete members in general consist of three major steps. The designer first chooses the initial concrete dimensions. In the second step, concrete dimensions and amount and detailing of reinforcement are determined using equilibrium and ultimate strength considerations. An estimate of the deformations under service condition can be considered as the last step. Strut-tie models are conceptual tools employed in the second stage to investigate the equilibrium between loads, reactions and internal forces in the concrete and reinforcement. By replacing a complex structural system with a strut-tie model, the estimates of internal forces due to shear, flexure, torsion and axial loads in the system can be obtained by analyzing the strut-tie model with the external forces applied to the system. The estimates of internal forces may then be used to determine reinforcement requirements, check concrete stresses and determine anchorage requirements. 

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