How to Make STM? – Load Path Method

One of methods to select Strut-Tie model is stress path method base on inner stress flow. After satisfy the D-region balance, this method determines elastic stress trajectories. Using that, selects Strut- Tie model. The picture above shows a typical D-Region elastic stress trajectories and the selected Strut-Tie model based on elastic stress trajectories.

Selecting Strut-Tie model is very easy if it’s simple design. Inclined Strut which represents compressive stress field can be allocated parallel with crack. Also you can allocate Tie with reference general reinforcement. These two procesures require knowledge and experience for basic design of structural concrete. In case of  complicated design, analystic procesure is also needed.

When you design structural concrete with complicated load and shape condition, it’s required the process of determining structural elastic stress trajectories . Generally, these handwork is unefficient because it takes so much time. But you can save time and effort by using the unmerial analysis software and the Strut-Tie model software.

 

Summary

1. A strut-tie model constructed by tracing elastic stress trajectories requires min. amount of reinforcing bars.

2. As a strut-tie model is generally selected based on the designer’s experience and subjectivity, the different strut-tie model design results may be acquired under the same circumstances.

3. Reliability on design results may be greatly reduced if a designer is deficient in understanding the structural behavior and load transfer mechanism.

 

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Reference

1. Schlaich, J., Schaefer, K., and Jennewein, M. (1987) Towards a Consistent Design of Structural Concrete, Journal of the Prestressed Concrete Institute, Vol. 32, No. 3, pp. 74-151.
2. American Concrete Institute (2014) Building Code Requirements for Structural Concrete (ACI 318M-14) and Commentary(ACI 318RM-14), Farmington Hills, Michigan, USA.
3. Korean Concrete Institute (2012) Design Specifications for Structural Concretes, Kimoondang, Seoul, South Korea (in Korean).

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4 figure(s) from the original post could not be recovered (the original server was retired and the Wayback Machine did not archive them). Text is as originally published.