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CONSTRUCTION ANALYSIS PROJECT
This report considers the issues of loads and how they are distributed throughout a multi-story structure towards the foundations, as my project topic suggests I must analyse and compile drawings that accurately display the loads within my chosen building. The building I’ll be looking at over the course of this period is ravens Bourne college.
RAVENSBOURNE COLLEGE PROJECT DATA:
The £70 million college, specialising in digital media and design, features a tessellated cladding which the practice describes as a ‘‘non-periodic tiling system symbolising a more diverse and contemporary approach to technology’’. The building’s design looks almost at chaos due to this tessellated effect, however it also provides a sense of order and structure. These two opposing ideals have helped create an architectural wonder, during the progression of this report I hope to display the main structural systems that are present.
Ravensbourne college is built up in two areas, the east and west wing. The building has been split into these two halves, the east wing and the west wing Floor-to-floor heights are a generous 4.5m. Both areas have a centralised core that house a few of the services within the building;
- emergency exit stairwell
- main elevator
- the emergency elevator
Internally a split level section is separated by the atria and reconnected by bridges and floor trays. The voids at irregular intervals connect but bottom-out at different levels, informing a clear hierarchy and creating real spatial drama.
The type of frame used for this building is a rigid concrete frame they are very common for buildings of this height, and can reach up to twenty stories. The system used has its advantages and its disadvantages as shown below.
The limitation in this design is caused by the continuity between members in a rigid frame, this type of structure is particularly advantageous in resisting wind and seismic loads. It does not necessarily have to be subjected to vertical loads only or consist of vertical and horizontal members." (Ellis, A. 2004).
The columns and the beams used within the internal structure for this particular type of construction, are made from reinforced concrete and they were cast in place. Due to this factor within the design of the building the tension and compression which is caused from the loads from above are greatly reduced.
The foundation system used within this structure is a typical deep foundation, this type of foundation is commonly used to extend through unsuitable or unstable soils. A bore hole test was carried out in the initial site analysis for this site it showed there was a high percentage of soft silt clay this is because the site is situated directly next to the River Thames.
(The bore hole test was not undertaken by myself but the information was there when researched.)
The majority of piles which were used in this construction were driven into the ground in clusters of two or more, when they are grouped in such a way it is important that the loads from the building are distributed evenly through the piles, therefore a reinforced concrete pile cap is joined to the heads of each cluster. The sets are all situated beneath a column. The piles are made from pre cast reinforced concrete. To support the building further a solid slab raft was placed and connected to the pile caps this completed the foundations.
The type of flooring system used is pre-stressed wide slab flooring. This type of system spans from one beam to the next. The reason pre-stressed flooring is used, is to overcome the concretes weakness in tension. Pre-tension concrete works by casting concrete around some pre tensioned tendons “this method produces a strong bond between the tendon and concrete, which protects the tendon from corrosion and permits the direct transfer of tension throughout the floor. Pre- tension concrete can be used to produce beams and floors spanning further than that of ordinary reinforced concrete.
This is the method used to create the concrete slabs off site. Once constructed they are transported back to site and craned into position. Each slab is purposely extruded one side and indented on the other, this way of fixing the slabs together provides a much stronger bond for the flooring system. Part of the flooring system, is a 50mm thick screed that covers the entire flooring, this takes us to ground level.
Steel columns and beams are used at the front entrance of the building, creating the structure for the atrium. The steel used for this development was made off site and brought in using the many transport links available to the area. Each element of the atrium was made to connect with a specific component and will only connect to its counterpart. The positioning of the steel is crucial due to fact that the steel itself isn’t directly part of the rigid frame system.
RAVENSBOURNE COLLEGE POSSIBLE IMPROVEMENTS TO THE STRUCTURE
‘’FOA claims the building will reach a BREEAM qualification of environmental excellence through ‘optimum environmental performance, low maintenance and high flexibility’ with a very low ratio of façade to area.’’
The design of this structure is truly beautiful, not only does it work as design but it also works with the function of the building. Without ascertaining any future plans of development the claim made above could either be false or true. As a whole the structure flows providing a large space that can be used for multiple uses.
The design of the building has allowed for the maximum use of both space and light. Creating wider space, however if it were possible by reducing the number of windows, it would be possible to further strengthen the structure in areas that could be seen as weakness’s.
Additional bracing of columns would further reduce wind loads, greatly so towards the east (River Thames) as this is where wind loads would be strongest.
The building features an innovative screen wall cladding system clad in small element tiles in a Penrose pattern inspired by the Arts and Crafts tradition. the architect has purposely used this form of inspiration to create an exterior that ties into the functional use of the building i.e. digital media and design. Displaying both the creative side and logical side. The cladding on this particular building seems to be used for aesthetic purposes it does provide further capabilities, in this section of my report I will be looking very closely at the technology that has been put together to build Ravensbourne College.
The main performance characteristics associated with cladding;
- Texture or profile
- Environmental impacts
- Embodied energy
- Structural capabilities
- Thermal mass
- Sound insulation
- Vermin resistance
Although listed some of the above characteristics have not been recorded in this report.
Vinyl cladding or PVC is widely used and very well known for being virtually maintenance free. The surface will never need to be repainted or repaired; it is a material which will last for years. Vinyl cladding is also environmentally friendly as nearly all of the materials used in making the material is from recycled plastic. (Fitzgerald, 2010).
Another type of wall cladding is metal cladding this can be made from various metals like;
All of the metals which can be used in the cladding process must be protected. Some of the techniques are powder coating, anodising or galvanising.
Despite its apparent complexity, only three tile shapes were required, comprising two irregular pentagons and an equilateral triangle. These tessellate and could be rearranged to work around the various window sizes, which were designed to accommodate the changing daylighting requirements. The structure is composed of 28,000 anodised aluminium tiles in three different colours.
Although aesthetic considerations is fundamentally important, the colour of cladding influences its capacity to absorb and reflect heat. it is preferable to use lighter colours or proprietary reflective finishes. Anodised aluminium tiles have been used throughout the structure. This design idea, will improve the thermal comfort inside the structure and reduce heat loss.
The cladding on this building comes in large sections which all piece together like a puzzle, the steel and the aluminium are used to create these sections. The sections are fixed to the main external wall. The way they are connected is, at the rear of the sections there are brackets which run the length of the building. These are made from steel and in the same way as the aluminium cladding they were treated and then painted for extra protection from the elements. These brackets are screwed trough the steel sheet and into a plywood board. The next stage is to position the sections onto the external wall. Eventually when in place the panels are screwed to the steel brackets which run along the walls. The screws do no penetrate the aluminium cladding as they fit between the gaps in the aluminium section.
ALUMINIUM TILE CLADDING SYSTEM
Availability: widely available
Embodied energy: Highest of any cladding. Most appropriate in highly corrosive environments where products with lower embodied energy have a reduced life span.
Maintenance: the maintenance of the tiles is quite low. Powder coated finishes generally have a life expectancy of 15 years. With the tiles being used the residual wear and tear from construction is almost non-existent, so if water is used it will seem virtually brand new.
Durability: Durability is very high due to corrosion resistance of the material.
Breathability: Aluminium is a vapour barrier and its excellent conductivity makes it highly prone to dew-point formation and water vapour condensation. It should always be fixed via a breathable cavity.
Waterproofness: Among the most waterproof of cladding materials.
Insulation: low U values
Fire resistance: The thermal conductivity of aluminium is around four times that of steel and its specific heat twice that of steel. The structure as a whole has good heat resistance capabilities
Finishes: Generally powder coated in standard colour for this building anodized coating has been used on all tiles.
Resource depletion: Aluminium is an abundant but non-renewable resource.
Recycling/reuse: Aluminium cladding is highly reusable (if screw fixed) and 100% recyclable.
CLADDING SYSTEM IMPROVMENTS
Improvements and alterations could be made to the cladding, one of which could be to change the way in which the sections are attached to the external wall. A way in which this could work is by installing support brackets horizontally up and down the water tight wall, these are fixed using screws which will penetrate the internal insulation.
Once the brackets are attached a channel bracket is fitted, there are supporting bars along the steel channel these are used for hooking the panels on to. The next step is to simply lift and hang them up onto the external wall. Finally isolator clips would be added, by doing this the panels will be safe from movement. If the external cladding system was carried out this way the panels could be easily moved if in an incorrect position therefore saving time and labour costs.
Purpose for which a building or compartment of a building is used
Assembly and recreation
Place of assembly or recreation, including the following:
A building may not be treated as a place of assembly solely because it is a building to which members of the public are occasionally admitted. Ravensbourne college although it is used as a learning facility, the building is used as a broadcasting centre for BBC Radio one.
Below I have listed a few precautions that have been developed to reduce the spread of fire within the building.
PRECAUTION ONE- PROTECTION OF INTERNAL PARTITIONS
- the internal partitions are made from steel stud work, this is roughly 600mm from centre, laid over the stud work is 12.5mm plasterboard with a 2mm cover of plaster
PRECAUTION TWO – PROTECTION OF BEAMS AND COLUMNS
- the beams are made from reinforced concrete, the main reinforcement is at the bottom of the beam this area is most likely to get affected first in the case of a fire, the thickness of the concrete to cover the reinforcement is 50mm
PRECAUTION THREE – PROTECTION OF FLOORING
- the flooring system used within the structure are solid flat reinforced concrete slabs, the overall thickness of this slab is 125mm this figure also includes the floor screed
PRECAUTION FOUR – PROTECTION OF STRUCTURAL STEEL
- The next structural element to be considered is the way in which the structural steel is protected; steel is one of the weakest materials when it comes to the effects of fire. So to protect the steel a covering of 20mm is used, this includes two layers of gypsum plasterboard, 1.6mm thick wire binding and a 2mm plaster finish.
Fire resistance estimate
The above figure shows the estimated time of fire resistance that is possible for each structural element with Ravensbourne College.
The main priority is to evacuate the occupants safely and securely. A disabled exit is critical with a large structure such as this and as mentioned in the beginning of this report
Within this building there are 8 fire exits all located on the ground floor. When the fire strategy is being designed one of the most important factors is the means of escape, within the structure there are pressurised stairways on each wing of the building. This type of stairway system works by keeping the stairwell under constant pressure at all times, by doing this it keeps the stairwell free from smoke and reduces the chances of fire.
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