Investigation into Proposals for the Superstructure of a Building

Investigation Report for the Requirements and Options Available for the Superstructure of a Proposed Building.

Performing Arts Centre at Gipsy Lane, Bishops Hull, Taunton.

Contents;

• Summary of Requirement of Report
• Analysis of Site
• Building Proposal
• Building Elements;

• Functional Requirements
• Performance Specifications
• Potential Solutions
• Comparison of Options
• Selection of Preferred Option

Summary of Requirement of Report;

The aim of this report is to analyse the superstructure requirements at the proposed Performing Arts Centre in Bishops Hull, Taunton.

For each building element the report will consider the functional requirements and performance specifications. From this analysis, potential building solutions will be determined and compared. Subsequently a particular technology will be proposed for the construction of each element.

Analysis of Site;

The site itself is situated in a residential development in Gipsy Lane, Bishops Hull in Taunton and is the site of an old Victorian School shown in red on the site location plan below;

Building Proposal;

The proposed structure for the PAC is a 2 storey height auditorium with store and access area, the cantilevered atrium at the entrance, a single storey office building and performer facilities with single storey corridor connecting to the old school building and original structure itself.

The floor plan attached below, has been annotated to reflect these separate areas.

Building Elements;

The separate elements to be considered for this report are as follows;

• Superstructure (load distribution structure).
• External Envelope (load bearing or non-load bearing).
• Internal Finishes.
• Roof Structure

For each of these building elements the report will discuss the functional requirements, Buildability requirements, various options available to satisfy the requirements, a comparison of these options and eventual decision based upon this comparison.

Investigation Report for the Requirements and Options Available for the Superstructure of a Proposed Building.

As the introduction explained the following building elements will now be discussed in depth consequently delivering a conclusion as to the preferred method of construction.

• Superstructure (load distribution structure).
• External Envelope (load bearing or non-load bearing).
• Internal Finishes.
• Roof Structure

Superstructure;

The functional requirements of the superstructure are such that it needs to have the strength to maintain the loads imposed on it, for example; able to support the roof and maintain stability. It should be durable, fire resistant and far as reasonable considering its proximity to other buildings and preferably affordable and sustainably sourced or recyclable.

The performance specifications required to meet these functional requirements with regards the loading capabilities of the Superstructure can be seen in Approved Document A and Approved Document B of the Building Regulations which cite;

Making reference to the following British Standards for Loadings;

And;

The functional requirements of the superstructure and its subsequent performance criteria could potentially be achieved with the following solutions;

• Framed Structure
• Load Bearing Walls

Framed Structures; 

These consist of skeletal frames;

                Figure i                Figure ii                                Figure iii

Portal frames;

                        Figure iv                                Figure v

And Panel frames;

                                                        Figure vi

Load Bearing Walls;

Usually consisting of block and brick or solid pre-cast concrete and a traditional method of construction;

Figure vii                                                        Figure viii        

Comparison of Options - Materials characteristics and properties;

By comparing the types of materials which can be used; such as timber, steel, block and brick and reinforced concrete; and each type of frame or wall in turn a conclusion may be reached as to the preferred method of construction technique.

Timber and steel are the most commonly utilised materials in structural frames. However, reinforced concrete is becoming a very popular modern method of construction as well. Regarding traditional construction brick and block methods are most usually utilised. The table, in document 2.2 figure i, and below shows the comparison of the materials in the form of timber, concrete, steel and brick to give quantitative figures for the following aspects; strength, elasticity, density, porosity, water absorption, moisture movement, thermal transmittance, electrical conductivity, durability, workability and melting points for each material.

                        

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Figure ix

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From figure ix, it can be clearly discerned that steel is the strongest, most durable, workable and dense however, it also has an electrical conductivity level and melting point to take into consideration.

The functional requirements of the construction insist that it must be strong, durable and flexible yet remain resistant to moisture movement and water absorption, due to the size in height of the main structure a skeletal frame is the most viable choice. Regarding material choices; steel would consider all of these aspects but with regards fire resistance would have to be treated (galvanised) to withstand and meet the guidelines in the Building Regulations.

Comparison of Options - Materials limitations;

The table in document 2.2 figure ii, shows the materials in the form of timber, concrete, steel and brick to give comparative information for the following aspects; corrosion, fungal attack, insect attack, frost attack, sulphate attack, efflorescence. Ultraviolet degradation and water attack (rising damp, water penetration) for each material.

It can be discerned from this comparison table that Steel is the strongest performing for each of the properties and limitations of the materials discussed. By using a steel frame, the superstructure will perform well in strength, density, non-porosity and elasticity and from sustainability point of view will be recyclable at the end of the building lifecycle due to its durability.

From a Buildability perspective, ease of use regards manoeuvrability, rapid construction and, relatively, cost is without question when comparing to reinforced concrete or a traditional load bearing brick and block wall. A Timber frame would also achieve this but is less successful as a material due to its susceptibility to fungal, frost, water and insect attack.

External Envelope;

As the external envelope is not actually part of the structure it does not carry any loads. The functional requirements of the external envelope for this type of structure, therefore, are such that it needs to have thermal and sound insulation, give enough natural light, provide security and privacy, be durable, prevent against water absorption and rising damp, be non-combustible, sustainably sourced, stable, prevent vapour movement, provide adequate ventilation, give little in the way of thermal or structural movement due to diurnal expansion and contraction and be affordable.

The performance specifications required to meet these functional requirements can be seen in Approved Document C of the Building Regulations, regards water absorption, which cite;

Making reference to the following British Standards;

Approved Document E of the Building Regulations, regarding Resistance of the passage of sound will give guidance as to materials likely to enhance sound insulation.

Approved Document F, regards Ventilation states;

Making the following references for Educational Structures such as the Performing Arts Centre;

Approved Document N; Glazing - safety in relation to impact, opening and cleaning states;

Making reference to the following British Standards;

Comparison of Options Available;

There are four basic systems of enclosing a framed structure; facings, infill, cladding and curtain walling. Due to the requirements of the building as a Performing Arts Centre a cladding system has been given further consideration.

Facings;

The fascia is applied to a solid background on the frame of the superstructure, in this case the steel skeletal frame. The background in this instance needs to be structural to support the facing and needs to ensure it is weather proof before erection.

Infill;

This system fills in the gaps in with panels or masonry. The system needs to allow for movement and be structural stable. With regards to weather proofing this system it requires a cavity to do this. Infill systems are labour intensive which may prove difficult on the type of site the Centre is being constructed on.        

Cladding;

This system is designed to fix to the frame in panels. There are many different options of materials available when using this type of external envelope system. The system can be weather proofed very quickly and already allow wind deflection and thermal movement.

Curtain Walling;

This system is similar to the above cladding in that it is made up of panels and can be manufactured off-site to include all windows and doors already in situ. As above they already allow wind deflection and thermal movement. They are very quick to erect and are fairly cost effective.

Comparison of Systems and Final Choice;

Having assessed the above information a cladding system would be the most sensible choice for the external envelope. The system is quick to install, is fairly cost effective, is designed with wind loads and thermal movement in mind and allows the greatest flexibility of the internal space. The fascia would be masonry in keeping with the original school building as requested in the design.

Internal Finishes;

Functional Requirements;

The functional requirements of the internal finishes are such that it needs to be able to control light reflection, provide privacy and sound & thermal insulation.

Performance Requirements;

The performance requirements can be found in Approved Documents B and E  as cited below;

Options Available;

Many options are available for the internal finishes of a building, such as partition walls or masonry load bearing walls. The cladding on a partition wall in the atrium or auditorium areas as opposed to the office space would have to be given careful consideration due to the spaces differing functional requirements. The auditorium for example requires much more sound insulation than, say, the office or corridors.

In using a cladding system, insulation may be used in the cavity to provide further sound and heat insulation which makes this one of the more sensible choices for the internal finishes. Different materials may be used to clad, such a wood or drylining. Wood would give a more aesthetically pleasing, modern finish. The cladding system provides not only the cavity for insulations but also the space for services which would usually have to be boxed in should another finish be decided upon.

Roof Structure;

The functional requirement of the roof structure are such that it needs to be weather tight, support loads, allow adequate drain off of water, provide security and protection from weather.

The performance specifications required to meet these functional requirements can be seen in Approved Document A, B, C. F and H which cite;

Due to the potential of inclement weather, the roof needs to be constructed quickly but with minimal risk to health. The Auditorium area is two storey height so a particular method must be chosen so that the roof can be constructed quickly crating the least risk to health and safety. This may be achieved by making use of Mobile Elevated Working Platforms and scaffolding.

The systems available for the roof system are a pitched trusses, cut-pitched roof, structural panels or a flat roof with false exterior.

The pitched trusses are manufactured off-site usually from timber or steel, and brought to site ready for putting in place. This makes the installation very quick from the delivery time to site and would be a good solution, however, because of the roof space being filled with bracing as is a requirement of this type of system useful space would be lost which may otherwise have been utilised for alternative heating systems or water storage.

The void would be usable however, if a cut pitched roof system were implemented. This would take more time though. The purlins required to carry the load of the rafters can be made from timber, steel or laminated timber (Glulam) which has very good sound insulation properties.

                                                

                Figure x                                Figure xi

The Structural Panels on the roof are the same as the Structural Panels as in walls;  manufactured off-site and installed with very little requirement of operatives spending excessive amounts of time at height. It is stable and can be constructed very quickly once delivered to site.