Two and Three-dimensional Analyses of Supported Excavations via Truss

Nowadays, the need for tall buildings, substruction of highways, construction of underground trains and consequently excavating operations is essential for modern urban communities. One of the most common types of retaining structures used for varying excavation depths is the metal truss. The aim of this study was to introduce a logical connection between two and three-dimensional analyses in a manner that by using two-dimensional analysis, horizontal and vertical displacements as well as internal forces of the retaining structures with a good approximation in three dimensional analysis (which is closer to the reality) can be calculated. Therefore, several parametric modelings were simulated in order to investigate the behavior of supported excavations via truss. Also, it was aimed to determine the ratio between maximum horizontal displacement at two-dimensional and three-dimensional analyses (PSR ratio). The PSR ratios for the depth of 4, 7 and 10 meters were 0.7, 0.55 and 0.4, respectively. The internal forces of a critical truss (near the center of the excavation) including axial forces and bending moments were also studied. Comparing the values of axial forces in the main structural members of the critical truss in two-dimensional and three-dimensional analyses shows a good agreement between the two types of modeling. The magnitude of bending moment in three-dimensional to two-dimensional analyses was 0.14, which proves unrealistic in twodimensional analysis, and can consequently be neglected in structural design procedure