Architecture

Architect Plamen Bratkov

The concept of the building has two points of departure: analysis of its location and analysis of its function. In order to analyze the location we set off to it from Sveta Nedelia Square and along Al. Stamboliyski Blvd. We move in an urban environment typical for the centre of Sofia. The comparatively uniform outline of the buildings is interrupted once at Vazrajdane Square, and again – by the tall structure of the building of the National Social Security Institute. The new office building is at the same side of the street, and with its permitted height of 15 floors it has been determined to be the second vertical repère along that axis. That is why for its facing we chose light-colour stone similar to that used in the National Social Security Institute building.

After we cross Opalchenska Str. the environment is the following: On the right there is a long row of pseudo-classic Stalinist architecture buildings which starts from the very corner with the technical school. Our building is on namely on that “classic” side of the street. At the crossing on the right is the new and shining horizontal structure of the mall, the school after it, and some of the blocks of flats of the conventionally modern Zone B5. In short, the environment here is non-homogenous in style, and on the other hand – as in many other sections of Sofia - development is yet to follow. This indefiniteness suggests some similarity with the office buildings of Chicago built in the first half of 20th century.

Thus we reach the second point of departure of our analysis: the fact that this is an office building. Its function together with the small area plot and considerable allowed height predetermine the vertical development. Since we intervene in urban tissue and create a new vertical repère, we limited our means of expression to a minimum set. At first those actually consisted in a classic set of distinguishable elements – slabs with colonnades between them. We refracted those elements through the prism of modernity, and they were turned into marks of assembling together of precast units resembling double T-panels. Colonnades were kept but joints cross the middle of each column and each slab, and they break up the structure which is monolithic at first glance, into components much smaller in size.

Had we lived in the first half of 20th century, we would have probably stopped here. The building would have been a smooth vertical structure with segmentation of the façade as described. But the world which we today live in is post-modern, with exactly so many versions of it as is the number of people inhabiting it. We refracted the form once again, this time submitting it to all possible attraction and repulsive forces with the respective directions into which they operate. Thus each “colonnade” was driven into its own way, all of them continuing to be parts of a whole.

When we move from the general concept to the concrete form a few other elements emerge which deserve attention. The “tower” or the main section of the building is constructed from two-floor and three-floor colonnades displaced in relation to each other. In plan they occupy one and the same perimeter; the difference is in their disposition. One of the floors is “intermediate” as a pause in the sequence. That floor lacks a colonnade and the structure is hidden behind the glass. Some “errors” – solid recesses instead of glass between columns - appear at several spots in the austere structure of volumes.

On both sides of the tower the building continues at the height of the neighbouring buildings. In both streets between the tower and the neighbouring buildings there are structures with openings in them, accomplishing and softening the transition. Those intermediate structures are in turn detached from the tower by a continuous glass joint which follows them in layout also along the vertical. Part of the roof areas of the protruding and lateral structures are used as terraces and the remaining areas are used for roof planting.

The building has all prerequisites to become an emblematic repère for the city – not just a vertical of urban development but a characteristic mark which is both derived from the spot and in its turn permeating it with a new meaning.

Structure

Dipl. Eng. Alexander Traykov
Dipl. Eng. Nikolay Dereliev

The building structure is monolithic, made of reinforced concrete. The constructional solution follows the architectural design which is unique and in many aspects challenging for the construction designers.

To enable maximum freedom of space planning beamless floor structures are used, and the use of beams is limited to the spots where considerable concentrated loads are applied.

The considerable console protrusions of the slabs at certain spots which are important accents of the architectural solution are made by building of rigid reinforcement into those zones.

The height of the building, the fact that Sofia region is a region of high seismic activity, and the broken up architectural form require serious attention to be focused to the calculation issues and the securing of the building against seismic impacts. Multi-version examinations were performed on three-dimensional models before decisions were made regarding the system intended to absorb seismic forces.

The structure safety and its flawless exploitation have been a priority in designing, which in the part of constructions was developed by a team of the designers office lead by Dipl. Eng. Alexander Traykov and Dipl. Eng. Nikolay Dereliev. Essential aspects of the project meant to provide the load capacity are the following:

• Observing strictly of all regulations currently in force in Bulgaria
• Applying the requirements and criteria of the European norms (Eurocodes) where that is important for improving the structure safety
• Using of licensed software – SAP2000, Tower and Stadyps to create computer models for calculation regarding the structure, aimed to analyze the result options of the building’s behaviour in response to different types of loads especially as regards seismic impact
• Applying the results of the team’s considerable experience gained in the course of many years in designing different constructions of buildings and facilities

Heating, Ventilation and Air Conditioning

Dipl. Eng. Yordan Angelov

The central heating / air conditioning installation is of direct evaporation type VRV

Choosing a VRV type of central system is based on the following characteristics of the system:

• High transformation ratio at 100% loading in heating mode – from 4.25 to 3.68 depending on the chosen outdoor units capacity
• Extremely high transformation ratios in operation under partial loading – reaching levels above 5
• Low operating expenses and maintenance expenses for the system
• Small size horizontal and vertical pipe ways
• Double rotor inverter compressors of the outdoor units
• The system is flexible and easy to install
• Possibility for a complete BMS including centralized control of all indoor units, access denial when locally set, possibility for energy monitoring – monitoring the electricity consumed for each indoor unit
• Refrigeration agent R-410A

The system design will comprise eight vertical pipes. The distribution grid is made of copper pipes supplying heat/cooling to the floors. Branching from a vertical pipe to the indoor units of the system will be realized through two-way distributors to each indoor unit. Copper pipes will be laid in the raised floor. Indoor units will be controlled by means of wired remote control installed in a convenient spot within the operation room. The system indoor units installed in the offices will be open and low mounted to the walls.

The distribution grid and vertical pipes will have heat insulation of micro-porous rubber 09-13-19 mm thick.

The heating of toilets/WC and bathrooms will be by means of conventional radiators.

Ventilation

Mechanic suction ventilation is envisaged for the two levels of the underground parking. It is provided by means of a roof-top fan. The exhaust air is emitted at the roof of the building. Exhaust air is naturally compensated through the parking entrance.

Toilets/WC and bathrooms ventilation is by means of forced suction through independent axial fans with back valves. The fans exhaust air through metal pipes of dia.110 and dia.160 vertically into special installation shafts to the roof of the building. The fans are switched on by means of switches mounted next to those for the illumination.

Internal Water Supply and Sewerage Installation

Dipl. Eng. Ivan Dragoshinov
Dipl. Eng. Lidiya Yaramova

Water Supply Pipework

The vertical water supply branches will be made of polypropylene PN10 pipes with heat insulation against condensate.

The piping in the toilets/WC and bathrooms will be in the walls, made also of polypropylene pipes - PN10 for cold water and PN16 for hot water.

Hot water will be provided from horizontal electric boilers hidden above the false ceiling of those rooms.

The main horizontal cold water supply network will consist of zinc plated steel pipes laid along the ceiling of the underground parking.

The internal anti-fire water supply for manual operation will be provided through fire hydrant cells on each floor.

Sewerage Pipework

The vertical sewer branches will be made of reinforced pipes because of the considerable height of the building.

The horizontal sewerage pipework will be laid along the ceiling of the underground parking level, and made also of reinforced PVC pipes and fittings.

Drainage of the underground parking space will be realized through low-profile linear drains by pumping.

Electric Installations

Dipl. Eng. Vasko Milenkov

Illumination Installation and Power Installation

In the offices power supply to all power consumption devices will be through installed distribution boards providing power supply to the regular, emergency and neon sign illumination; to reserve power sockets, computer sockets, workstation sockets and general use sockets. The workplaces will be provided with floor-mounted or wall-mounted power sockets “Schuko” type with safety pin - red in colour for computers and white for other consumption devices; sockets for the telephone installation and sockets for the computer network. Lighting of all rooms is in accordance with their envisaged functions.

In the shops distribution boards will be installed and from them the installation for the illumination, for power sockets and ventilation convectors will be laid above false ceilings and vertically behind gypsum board walls. Three types of illumination are envisaged for the shops: regular, emergency and signboard illumination. Lighting of all rooms is in accordance with their envisaged functions.

For the basements separate distribution boards are envisaged for each level. The power supply installation will have IP 44 class of protection. Regular and emergency illumination is envisaged. Operating illumination is turned on by means of motion detectors (PIR) and a contactor. Ventilation is controlled through a time relay. All lighting fixtures are of fire-safety type and have respective certificates.

In the café power supply to all power consumption devices will be through an installed distribution board providing supply to the regular, emergency and signboard illumination; to the regular power sockets, power sockets for technological needs and general use power sockets. Distribution boards will provide power supply automatically for the café ventilation – suction and supercharging type. Lighting of all rooms will be in accordance with their envisaged functions.

Doorbell Installation

A power supply block for the doorbell installation will be included in the main distribution board of the building. The doorbell installation will be in goffered PVC pipes laid vertically in special groove in the structure. Doorbell buttons will be mounted next to the front doors of offices, and the door bells - above the front door inside each office.

Telephone Installation

Telephone reglets will be mounted at a certain spot in the basement, in a detached room for weak-current equipment for the building; they will be encased in a communication cabinet from which the installation will be extended for the respective offices, shops and the café . Installing a RACK type communication cabinet is planned for the weak-current installations of each office, shop and for the café. The telephone outlets will end in RJ 11 telephone sockets in the floor boxes installed under each workstation.

Antenna Installation for Cable Television

A communication weak-current cabinet with TV amplifiers will be mounted at a certain spot in the basement, in a detached room for low-current equipment; the installation for the respective offices, shops and the café will be extended from the cabinet. Installing a RACK type communication cabinet is planned for the weak-current installations in each office, shop and in the café. The antenna outlets will end in antenna sockets located at a 0.35m from the floor and in the very floor boxes.

Structural Cabling

The installation for structural cabling of the respective offices, shops and the café will be extended in vertical piping from the weak-current equipment room in the basement. Installing of RACK type communication cabinets is planned in each office, shop and the café. The internet cables will end in RJ 45 sockets in the floor boxes installed under each workstation.

Security System

Each shop, office and the café will be cabled /prepared for installing the security system connected to the post of the 24-hour security guards. The equipment will be installed by the security companies after individual contracts are concluded with them.

Metering

Individual metering devices for remote metering with possibility for optimization of expenses will be installed for each shop and office and for the café – a heat meter, water meter, and power meter.

Lightning Protection Installation

A lightning protection installation will be provided for preventing of direct and indirect lightning strikes on the office building.

The installation will comprise lightning conductor rods and a conductive network made of zinc plated steel. The metal parts of the building which are located on the roof will be connected to the lightning-arresting system or to the metal roof, and additional lightning receiver rods will be placed on the non-metal parts of the building rising above the roof, and will be connected to the conductive network.

Grounding Installation

The grounding installation is a basic component of each power supply installation. It is provided for the purpose of limiting of high voltage and leading to the ground a strong charge which could result from a lightning strike or from commutation processes in the power system. The grounding system eliminates or mitigates the risk of damages to the electric installation thus protecting people and equipment from hazardous voltage.

All power sockets of all shops, offices and garages and the café, all the bodies of motors, boilers, pumps, electric convectors, fans and all equipment comprising the technological equipment of the building will be connected to the grounding installation.

Fire Alarm System

Dipl. Eng. Liliya Stoyanova

A fire detection system and automatics equipment with addressable sensors will be installed in the basements, in the shops, in the café and in the office section.

Fire Protection System

Dipl. Eng. Svetlana Dimitrova

An automatic sprinkler fire suppression installation is envisaged in the basements for protection of the two underground garages.