STM is a type of truss-like model that conceptually simplifies a concrete structure based on the stressing mechanism. Specifically, STM simplifies the tensile stress region as a tie, the compressive stress region as a strut, and the connection between the tie and the strut as a nodal zone. As a result, it not only makes full use of the tensile properties of steel rebars and the compressive properties of concrete but also satisfactorily reflects the load transfer mechanism inside a concrete structure.  
The construction of an accurate and reasonable optimal STM is not only the primary task of the design of concrete structures using the STM method, but a better choice for the reinforcement design of concrete structures. However, in the STM construction process, the analysis of the stress transfer in irregular concrete deep beams, especially in their D-regions, is often difficult, inefficient, and requires a designer's subjective experience, resulting in a somewhat arbitrary model. That is, different designers can construct different optimal STMs and can also design significantly different reinforcements for the same irregular concrete deep beam member. [PERSON] and [PERSON] [14] proposed an evolutionary structural optimization (ESO) method to construct the STM of a concrete member by obtaining the optimal topology through the gradual removal of inefficient materials. Later, to address the low optimization efficiency of the ESO method, [PERSON] et al. [15] proposed a bidirectional ESO (BESO) method to both remove and add material elements in the optimization process; thus method has a better optimization efficiency but is unstable and prone to oscillation. [PERSON] et al. [16] improved the STM of [PERSON] et al. [6] by using the homogenization topology optimization method and proposed the corresponding optimal STM, which has significant advantages in controlling the width of cracks and reducing the amount of steel used, as demonstrated by the test results. [PERSON] et al. [17] generated the optimum STM for corbels and concrete deep beams with openings using the isolines topology design (ITD) method and verified the validity of the optimal STM with existing test data. [PERSON] et al. [18] noted that when constructing the optimal STM for concrete structures, it is necessary to repeatedly optimize and improve the STM. They then gave suggestions on how to obtain the optimum STM. Based on an existing STM, [PERSON] and [PERSON] [19] proposed a new STM that can minimize the amount of steel used in concrete deep beams by adjusting the position and number of struts and ties in the STM; they also introduced two design parameters, namely, a practical reinforcement design coefficient and a stress redistribution coefficient. [PERSON] et al. [20] constructed two optimal STMs for the same simply supported concrete deep beam with an opening and designed the reinforcement using each STM. The validities of the two optimal STMs were then verified with finite element (FE) analyses.  
A properly and reasonably designed STM can effectively reduce the amount of steel used while ensuring the load-carrying capacity of a structural member. In this study, the STMs of two typical irregular concrete deep beams (designated as Group A and Group B) were constructed based on the FE results and the optimal topology. Additionally, the optimal STMs for each group of irregular concrete deep beams were compared with the STMs previously constructed by other researchers. For each group of irregular concrete deep beams, a plain concrete deep beam specimen and a reinforced concrete deep beam specimen according to the reinforcement design and guided by the corresponding STM were cast and subjected to static tests. Based on the test results, the STMs for each group of irregular concrete deep beams were comprehensively evaluated.