A strut-and-tie model (STM) is an ultimate strength design method based on the formation of a hypothetical truss elements that transmit forces from loading points to supports. The STM utilizes concrete struts to resist compression and reinforcing ties to carry tension. Design using STM involves calculating the required amount of reinforcement to serve as the tension ties and then checking that the compressive struts and nodal zone (joints) are adequate to support the forces. A key advantage of design using STM is that the designer can visualize the flow of stresses in the member. This paper presents the basic concepts, assumptions and approaches using STM to perform the calculation and design for the existing foundation anchor retrofit based on a real application in high seismic zone. The analysis also includes up-to-date finite element modelling techniques for the machine base plate the anchor rods connection to the concrete foundation subjected to large forces (tension and shear).
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