Overload in the roof trusses of the Media Center building in Saransk

. The possibility of applying overload to the nodes of the bottom chord of the roof trusses of the Media Center building constructed as a part of the design of the temporary buildings and structures for the preparation and holding of the World Football Cup in the Russian Federation (Saransk) in 2018 is studied in the article. A variant of fixing the load with the help of the universal mounting is developed.


Introduction
After the end of the World Cup 2018 in Russia, a rich legacy in the form of sports facilities and infrastructure remained. For infrastructure facilities, it was immediately clear that they would continue to serve the benefit of the population of the organizing city: hotels will be partially transferred to the housing stock, improvement of the city will contribute to a more progressive cultural rest for citizens and tourists, new roads and interchanges will significantly reduce the time on the road and significantly reduce the transport load on the existing network, newly built or reconstructed facilities, such as the airport in the city of Saransk, will allow relocating with minimal time between cities.
The situation with sports objects, is different a little. Tremendous stadiums, designed for tens of thousands of spectators, are currently not as popular as during the championship, and facilities for auxiliary purposes: press centers, media centers, fan passport issuing centers, etc. are generally empty. In order to get benefit out of empty space, the operating organizations received the right to rent out part of the auxiliary buildings for mass cultural events.
Since mass events envisage performance on the speaker's stage, and the stage, in turn, provides for suspended light and sound equipment, it became necessary to carry out activities for the preparation of truss structures for additional load application.
Thus, there is a relevance of the development of design solutions in terms of the application of additional load on the trusses. Let us consider the possibility of applying additional load to the nodes of the lower belt of the roof trusses of the Media Center building built as a part of the design of temporary buildings and structures for the preparation and holding of the World Cup in the Russian Federation (Saransk) in 2018.

Materials and Methods
The possibility of applying additional loads on building structures in connection with the suspension or support of rigging means is determined by appropriate calculations and measures are taken to exclude the possibility of damage to building structures. The nature of the application of the additional load is stationary, since the action planes of the bending moment and lateral force rotate together with the joint. To calculate the additional load, do the following: collect the load on the existing system, determine the additionally applied loads (size, location), determine the internal forces arising in the rods of the truss from the combined effect of the design and additionally applied loads, determine the load-carrying capacity of the nodes the farm connections, taking into account the additionally applied load, with a positive result of the calculation of the possibility of applying additional load and develop a mounting option.
The settlement mechanism is adopted in accordance with the joint venture 16.13330.2011 Updated version of SNiP II-23-81 "Steel structures". To determine the internal efforts, the program complex LIRA-SAPR R 2013 has been adopted.

Results
We will check the carrying capacity of roof trusses of the Media Center building in the city of Saransk. Rafter trusses are made of galvanized thin-walled steel profiles with a C-shaped section. The verification of the carrying capacity of roof trusses is carried out in order to determine the possibility of applying additional nodal loads.
The initial data was the working documentation "Design of buildings and temporary facilities for the preparation and holding of the World Cup in 2018 in the Russian Federation. Media Center 40x70m, Saransk" in terms of sections: metal structures, metal structures, metal structures, as well as measurement drawings [1][2][3][4][5][6].
In the extreme, panels of the upper belt are taken outside the nodal load application. The design scheme of the trusses and the magnitude of the nodal loads are shown in Figure. 1. The design cross-sections of the elements of the truss trusses are shown in Table 1 and   The results of the calculation of the determination of the forces and the geometrical dimensions of the trusses are shown in Table 2 and Figure 2, respectively.
Therefore, the moment of inertia of the C-shaped profile AC-400-90-22-3,0: The radius of inertia of the section: We Moment of resistance: Check the stability of this rod as an eccentrically compressed element. For this, reduced eccentricity: The ratio of the area of the shelf section to the area of the wall: Galvanized steel: Wall thickness -2 mm.
= 6450 * 0.9 * 1,6 * 0,6 = 5573 , In the support unit of the upper belt, 12 bolts were designed. The force in the upper belt, taking into account the additionally applied load of 700 kg in each node of the lower belt, is N (2-4) = -35 tons.
The required number of bolts in this connection with a diameter of M16 of strength class 5.8: In the node the number of bolts is designed 12 pcs.
In the assembly joint of the upper belt (middle of the truss) 11 M16 bolts of strength class 5.8 were designed. Force in the joint zone Ng = -44 tons.
The number of bolts, sufficient for the perception of this effort, taking into account the additional load in the nodes of the lower zone by 0.7 tons.
In reality, 11 units are designed in the unit. The lower belt "works" on stretching and is made of a C-shaped galvanized paired profile.
In the connection, 6 pcs are designed. Efforts in all three racks of the truss with additional load are Racks are attached to the nodal gaps 4 M16 bolts strength class 5.8. Taking into account the additionally applied load, the required number of bolts for fastening the struts to the gussets is: Consequently, when an additional load of 700 kg is applied to the lower nodes of the truss (3 knots), the carrying capacity of the truss trusses will be provided.
We will develop a variant of the suspension device to ensure universal mounting of the additionally applied load to the truss assembly. The designed suspension must meet the requirements of universality for the further installation of suspension equipment. Therefore, we use a loop made of sheet steel. Such fastening will allow the load to be applied to the node in any convenient way (hook, sling, etc.) and to ensure the attachment mobility in the plane of load application.
Technology suspension device is as follows: − dismantle one existing bolt in the rack mount, as shown in Figure 6; install washers on the two sides of the pin, nuts, lock nuts; − tighten the connection with a torque wrench to a standard value corresponding to strength class 5.8; − install 2 intermediate nuts, washers on both ends of the stud, install the suspension, the remaining 2 washers and nuts, tighten the connection on each side of the stud.
Let's make the specification of materials for the device of one suspension, we will present the results in table 3.

Conclusion
As a result of the study, the following were found: 1. It is possible to apply additional load in the trusses. 2. The maximum additional nodal load should not exceed 800 kg due to the carrying capacity of the bolted joint of the upper belt in the middle of the span. 3. The option of attaching an additional load to the lower nodes of the truss is designed in Figure 6 of this study.