*2.2. Structural Members*

Members with steel tube sections of different diameters and thicknesses are used in the truss roof system. The pipe elements with screwed cone ends are connected to the hot forged steel spherical joints. These joints ensure that no eccentricity occurs and the only axial forces are developed in the bars of the truss system. The yield strength of the material (S235JR) of the bars and the cone parts at the ends of them (DIN 2458) is 235 MPa, ultimate tensile strength is 510 MPa, and the allowable stress is 144 MPa. The bolts used for mounting the bars to the spherical joints are made of 10.9 material quality. The tensile strength of the bolts is 1000 MPa, yield strength 900 MPa, and the allowable strength is 360 MPa, in which the safety factor is 2.5. The spherical joints used to connect the rods to each other and the supports are made of hot forged steel with a yield stress of 330 MPa and a tensile strength of 590 MPa. The strength values and the chemical decompositions of the materials used in the truss roof system were validated by Piroglu et al. [8].

The support spheres are fixed onto the concrete columns by using square or circular plates bolted to the columns. The supports are made of EN C45 steel, and Teflon plates are placed under the sliding supports to reduce friction. The details of the joints and supports are given in Figure 5.

**Figure 5.** View of the spherical joints and the supports.

## **3. Analysis**

Two main groups of analyses were performed within the scope of this study. The first group was called the global analysis, where all the load-carrying members of the building were considered as beams and bars, while the second group considered the individual columns and supports.

The first group included multiple case scenarios with different combinations of loads. Only two major cases are presented in this study for the sake of simplicity.

The second group consisted of two stages. The first stage investigated the effective material properties of the concrete column reinforced with steel rods under uniaxial tensile strain conditions. Thus, the column was handled as a composite material. The second stage investigated the individual column support connection under the highest forces determined by the global model acting on an individual support.

All the simulations were conducted using the commercial software Abaqus (Dassault Systèmes, Vélizy-Villacoublay, France) under static loading assumptions.

The values of the three most important material properties, namely Young's modulus (E), Poisson's ratio (ν), and the thermal expansion coefficient (α) are shown in Table 1.


α μ μ

ν

ν α **Table 1.** The material properties considered in the analyses.
