Actual problems of the design documentation development for capital repairs or reconstruction of capital structural facilities

. The article discusses some urgent problems that designers face when developing design documentation for overhaul or reconstruction of capital structural facilities using the example of the object " The pool overhaul at the address: Rostov-on-Don".


Introduction
One of the main design goals is the development of a technical solution in accordance with the task (technical design assignment). At the same time, the implementation of the technical task can lead to both the overhaul of the structure and its reconstruction.
The Urban Planning Code of the Russian Federation [1] contains the following definitions (Chapter 1. Article 1): Reconstruction of capital construction facilities (with the exception of linear facilities)changing the parameters of a capital construction facility, its parts (height, number of floors, area, volume), including superstructure, reconstruction, expansion of a capital construction facility, as well as replacement and (or) restoration of load-bearing building structures of a capital construction object, with the exception of individual elements' replacement for such structures with similar or other elements that improve the performance of such structures and (or) restoration of these elements.
Overhaul of capital construction objects (excluding linear objects) -replacement and (or) restoration of the capital construction objects' building structures or the elements of such structures, with the exception of load-bearing building structures, replacement and (or) restoration of engineering support systems and engineering networks -technical support of capital construction objects or their elements, as well as replacement of individual elements of load-bearing building structures with similar or other elements that improve the performance of such structures and (or) restoration of these elements.

Method
Let us consider modern methods of design solutions [2][3][4][5][6] on the example of the object "The pool overhaul at the address: Rostov-on-Don". Before the design solutions' development, a detailed instrumental examination was carried out in accordance with the requirements BC 13-102-2003 "Rules for Inspection of Load-Bearing Structures of Buildings and Structures" [7] and GOST 31937-2011 "Buildings and Structures. Rules for inspection and monitoring of technical condition" [8].
The pool building is a structure of brick bearing walls and precast reinforced concrete beams, floor slabs and coverings. The building has a variable number of storeys: from 1 to 3, built in 1968. In plan, a building of complex configuration with overall dimensions in the axes 35.75х25.11 m.
Pool bowl in axes 1-9, C-D is a rectangular reinforced concrete tank. The dimensions of the pool in the plan are 24.95x9.15 m. It is made of monolithic reinforced concrete of class B25. The bottom of the tank is a monolithic ribbed floor consisting of a 300mm thick slab, secondary and main beams. The main beams, in turn, rest on a grid of columns. Columns are reinforced concrete monolithic ~ 500х500mm. The walls of the bowl are reinforced concrete of variable thickness (thickened at the bottom and ~ 200mm at the top at the level of the side of the pool). The foundations are free-standing, stepped. The pool bowl has a deep-water part with a depth of 4.35 m and a shallow part, a depth of 1.6 m (to the top of the side).

Results and discussion
Significant defects and damage recorded during the survey -significant damage to the reinforcement by corrosion from 40 to 90% of the cross-sectional area. In addition, it should be noted that the protective layer of concrete in the walls is peeling off. In the cantilever beams of the deep-water part, cracks with an opening from 0.3 to 1.0 mm were recorded. This characterizes the destruction of these cantilever beams from the acting load. Reinforcement corrosion is on average up to 30%, which makes the periodic profile of the reinforcement indistinguishable. Destruction of the protective layer of concrete and corrosion of reinforcement of monolithic structures adjacent to the pool bowl. In the course of the survey, another reason for the violation of the concrete structure was discovered -physical corrosion of the reinforcement.
Reinforcement corrosion in the concrete body was influenced by the following factors: -neutralization of calcium oxide hydrate in a humid alkaline environment with airborne vapors (CO2). At the same time, reaching the reinforcement, carbonization transfers the steel into an active state, and the oxygen entering the concrete from the moisture ensures the corrosion process flowing according to the electrochemical principle; -corrosion destruction of reinforcement due to de-passivation of reinforcing steel under the influence of chlorine ions (Cl-).
The greatest corrosion destruction can be observed on the end wall, side walls of the deep-water part of the pool bowl.
Thus, the corrosive destruction of reinforcing steel was the result of the combined action of neutralization of the concrete moisture-alkaline environment (carbonization as a continuous process) and de-passivation of reinforcing steel due to the effect of chlorine ions contained in the water of the pool bowl (continuous process).  The main reason for the existing defects in the pool bowl structures is massive and regular leaks caused by a malfunction of the waterproofing.
Lack of the pool technical operation system in general and the pool bowl in particular is observed. With an established system of operation, attention would be paid to the state of the pool bowl (commissioned in 1968) and appropriate timely measures could be taken.
As a result of assessing the technical condition of the monolithic reinforced concrete basin of the pool, based on the results analysis of a detailed (instrumental) survey, it was found that the supporting structures of the basin (walls, bottom, beams, columns) have defects and damage that do not meet the requirements of construction rules and regulations. The technical condition of the pool bowl was recognized as emergency. Particular attention should be paid to the fact that the emergency state is characterized by damage and deformations, which can lead to a sharp decrease in the bearing capacity, the collapse of individual structures.
In connection with the actual technical condition, working drawings were developed to strengthen the pool bowl.
The     Due to the fact that the category of the pool bowl technical state according to the survey results is emergency, and the adopted reinforcement option entails a change in the stressstrain state of the supporting structures (i.e., the design scheme changes), the work on the pool restoration should be classified not as capital repair, but as reconstruction (GOST 31937-2011, UPC RF №190-FL, Art. 1, Art. 14). Today, this is one of the most common problems that have arisen in the process of developing design documentation for the overhaul of an object, which puts the designers in the "to-peak".

Conclusion
For the implementation of design solutions to strengthen the basin of the pool, other methods can also be applied, for example, using modern reinforcement methods using composite materials [9][10][11]. This will increase the rigidity of each structure and the bowl as a whole.
the development and implementation of these design solutions using modern methods will qualify the design of the pool bowl in a working condition and will return the ability to perceive all the loads acting on it.