Key Criteria for On-Site Material Storage

Task 1

a. With reference to the sketch important criteria pertaining to materials storage on site are:

Safety considerations to allow vehicles delivering materials to site to be able to move and off-load without harm; Ensuring that appropriate quantities of the right materials and materials are delivered to, or near, the point of use on a just-in-time basis has a great impact on productivity, project timekeeping and general housekeeping and safety (Mawdesley et al., 2002); To provide a method of accounting for the quantities i.e. materials are arranged so that the assets can be counted and located; Security to reduce the risk of theft or vandalism; and Provision of a fabrication area which can be used for activities such as the final assembly of small components and lagging of air conditioning ductwork and units.

b. During the preparation of the site, including the demolition of the incumbent buildings the following materials may be required

Hoardings established at the site edge to provide separation between the site works and the adjacent areas; For top down demolition projects, a scaffolding system, comprising tubes, couplers, baseplates, toe boards, brace and decks; Screening for the building including catch fans; Temporary supports and props to support the phased demolition of the building; (Possibly) explosives for stubborn building elements.

In addition, temporary site utility services (electricity and water) will also be required to provide power for equipment and water for damping down, cleaning etc

The demolition works will yield demolition waste (Poon et al., 2001) which can be classified as:

Hazardous materials, for example batteries, asbestos, lamp ballasts, PCBs etc Material for landfill; and Recyclable material

The client has a legal responsibility to ensure that production, for waste storage, transporting and disposal of business waste is carried out without harming the environment. This is usually passed to the Contractor who will develop a Site Waste Management Plan (Mcdonald and Smithers, 1998). This will address how the materials are sorted, stored and disposed of.

During the early phases of construction, the following materials may be required

Formwork and falsework; Sand, cement, water and additives for concrete; Drainage pipes to be installed within the foundations; and Bricks, glazing, doors and roofing materials.

Additional materials required for the construction of the main structure and the associated precautions required with respect to handling and use include:

Compressed air for use in power hammers and drills Volatile organic compounds (VOC) are either natural or man-made chemicals typically found in thinners, paint, plastics, artificial fibres, glues and protective coatings which need to be stored and used in well ventilated spaces.

c. The following table summarises the main construction materials, what hazards they may present and what measures must be taken to reduce the risks to people working on the site or working moving or living near to the site.

For the solvents a risk assessment would be undertaken which would involve Undertaking a Control of Substances Hazardous to Health (COSHH) appraisal (Russell et al., 1998). This will help inform the best way to store and handle the materials. This may inform the need for bunded areas, specialist fire protection measures, or locked ventilated cupboards.

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d. As this is a brownfield site as the land has been used previously for an industrial or commercial purpose, there will be some existing utility services within the footprint. These may either be

Provided by public utility services provides to serve the buildings: for example, for the main incoming electricity, gas, water or telecoms supply or drainage; Public utility services which have nothing to do with the buildings on the site, but have been granted a wayleave or easement to pass through and will thus there will be requirement for access; ‘Private’ services within the site: for example, electrical power supplies for external lighting and external power provision. There may also be interconnecting services for fire detection and alarm system cabling, medical or other gas pipes and CCTV systems cabling, and generator fuel lines between buildings.

Approved Codes of Practice (ACOPs) are guidance with specific legal standing. is approved by the Health and Safety Executive, with the consent of the Secretary of State. They give practical advice on how to comply with the law. In this case the relevant guidance is ‘Avoiding danger from underground services HSG47’ This targets all relevant stakeholders associated with the appointing, scheduling, managing and executing work associated with utility services. It describes the possible hazards and gives information and guidance on how to decrease both indirect and direct risks which may arise. During the construction of the foundations it is necessary to locate all live services. These should first be identified by checking record drawing information, but these can be very unreliable, and it is usually recommended to undertake scans and trial digs to obtain a better degree of confidence. If they are no longer required, then they will need to be disconnected and removed. If they are still required (most likely in the case of easements) then it will be necessary to either work around these or divert them.

It should be noted that the relocation utility services may involve earthworks which could potentially affect the cover (as illustrated above), impact on archaeological heritage, infringe roots of trees with protection orders.

Task 2

Steel can be used for the main structure of the building, and it can also be used for the façade, secondary steelwork that supports building services equipment, for reinforcement in concrete, for fasteners etc. All these uses need to be considered over the whole life-time of a building, which means that the ultimate demolition and disposal of the remains needs to be considered. The main environmental concerns, which need to relate to achieving long-term benefits to the environment, relating to the use of structural steel are:

Embodied energy; Operational energy and internal environment; Sustainable design; Transportation energy; and Recycling and re-use.

Embodied energy

Embodied (sometimes called embedded) energy is the energy expended associated with the ‘upstream’ or ‘front-end’ and the ‘downstream’ cycle of a process. It is the energy is built into the materials and is not dependent on the number of occupants in a building. This starts with the extraction or abstraction of the raw materials, their transportation, processing, final delivery and putting into its final position. Thereafter the demolition and re-using of the materials. The calculation for embodied energy comprises of a multi-faceted complex computational process. At present there is no single globally accepted methodology as to how to undertake these calculations. However, there are several case studies which demonstrate that structural steel outperforms concrete with respect to embodied energy (Costanza, 1980).

Operational energy and internal environment

Operational energy is dependent on the occupants and their behaviour. It may be that a higher embodied energy level can be justified if it contributes to lower operating energy. For example, if there is a great amount of thermal mass which is high in embodied energy it could meaningfully decrease the heating and cooling loads. This means less energy is required for heating and cooling over the lifetime of the building.

Sustainable design

Good robust design methodologies are important with respect to sustainable construction. The decision to use steel in the design can help with respect to material efficiency, as steels high strength/weight ratio means that less material is needed, particularly due to the potential for long spans and slender columns. The specification of steel, also allows for some options for off-site pre-fabrication, thus allowing elements of the building to be constructed in better conditions and brought to site. The development of BIM processes means that the designers requirements can be better passed to the manufacturers with less ‘waste’ between the design intent and the design shown on the fabrication drawings.

Transportation energy

The fabrication of structural steel requires a large permanent factory set up, thus is almost always off-site and thus there will be a requirement for the steel to be transported. On the other hand, concrete can be created closer to the site, or an on-site batching plant can be provided. Concrete is also more likely to use locally sourced materials.

Recycling and re-use

Most of the structural steel used in the UK is recycled. Steel is relatively easy to sort from waste as it can be ‘picked-up’ by magnets. Most steel can be relatively easily dismantled and either re-used in the same form or recycled without any loss of quality (Dahlstrom et al., 2004)

Features of typical materials used for such a structure 50 years ago might have included:

The inclusion of asbestos-cement for a range of purposes such as strengthening cement, fire and acoustic resistance; hence it could be found in wall and roof claddings, floor coverings and spray-on textured ceilings. This is now known that classified as a known human carcinogen which if asbestos fibres are inhaled affect the tissues in lungs and cause scarring and inflammation (asbestosis). It now requires specialist involvement with respect to surveying, removal and disposal; Poor quality installations leading to concrete cancer. This may originate due to poor materials and workmanship practices associated with the reinforcement steel; External walls and roofs would not have included insultation as this was not a requirement of the Building Regulations; Less composite materials such as multi-walled panels.

In general, the development of more sophisticated software for calculations, including finite-element analysis means that the use of materials is leaner,

Task 3

a. Both steel and concrete can be used to provide the beams and columns that form the structure of a building.

Capital and Operating Costs

Generally, the capital cost of steel is less than concrete, albeit the price can fluctuate due to political drivers and global supply and demand. In contrast the capital cost of concrete tends to be more stable. However, concrete installations attract more operational costs associated with on-going maintenance and repairs, an in terms of labour costs, the provision of concrete is more labour intensive, thus in parts of the world where labour is very cheap, this may be the overriding factor.

Physical properties

Characteristics of structural steel are that it is tremendously sturdy, rigid, tough, and supple. Concrete has a relatively high compressive strength but lacks tensile strength. Concrete used in construction is almost always reinforced with steel reinforcement to increase a structure’s tensile capacity, ductility and resistance. Structural steel is prone to corrosion when it meets water, as such needs to be treated. Whilst concrete itself (if properly constructed) is water resistant, the steel reinforcement is susceptible to corrosion if it comes in contact with water. Thus, care is required in this respect of the installation (Tuutti, 1982).

Fire Resistance

Steel is intrinsically a non-combustible material hence fire resistant, but when extreme heat is applied its strength is compromised. This must be addressed by adding a coat of fire resistant material, either sprayed on or by boarding to structural steel columns (Kodur, 1999).

Concrete does not need any extra fireproofing treatment.

Environmental impact

Most structural steel used is derived from recycled materials. Thus, when manufactured, fabricated and treated properly, structural steel will have a minimal impact on the environment. The main composite materials that make up concrete (cement, sand, water and gravel) are naturally occurring. However, it should be noted that this is not true for some of the aggregates and additives added to the blend. During demolition, concrete can be recycled by crushing and re-used used in future blends. This type of recycling can reduce a presence of concrete in landfills.

Adaptability and flexibility in design

Structural steel is flexible in the sense that it can be fabricated into very many forms and shapes. Whilst concrete can be formed many ways, it does have limitations in terms of spans and heights. Also, some buildings use the steel as part of its architectural features. Whilst there was a fashion for this for concrete in the 1970’s, this has now passed, and steel is more fashionable.

b. An alternative to concrete or steel for building structures could be Mass Timber Construction (MTC). This is the output of a process that makes use of engineered wood fabricated by bonding solid-sawn timber together in crosswise and longitudinal layers with structural glues to produce timber panel products as the main structural material. The environmental benefits espoused include the fact that wood is hard-wearing and renewable resource and can lead to a more pleasant and natural ambiance inside a building (Kremer and Symmons, 2015).

c. The standards used in the design of a buildings structure are generally either

In the UK, The Structural Eurocodes (BS EN1990-1999) which have essentially superseded the codes produced with the British Standards Institute; or

The International Building Code (IBC) established in the US by the International Code Council (ICC).

It should be noted that either of these codes may be modified to reflect local conditions and regulations when used outside their countries of origin.

d. An example of the testing procedure that would be used to check that the material is able to support a structure would be the concrete cube test which determines the compressive strength of concrete which checks the ratio of water to cement, the strength of the cement and the quality of concrete material and the quality control being undertaken during making of concrete (Polder, 2001).

The procedure involves making test cubes from the same concrete that is poured into a building, then leaving them to set. Then, the cubes are tested, by crushing them in a compression machine at 7 and 28 days. If they then fail, then then further investigation is required with respect to the concrete as poured. In the worst case it may need to be removed.

e. Concrete is exceptional compared with other construction materials as it undergoes numerous processes between arriving on site and being put into its final position, and then compressed, finished and cured. This is the case whether the concrete is site batched or arrives ready-mixed. It is therefore necessary to sample the concrete and conduct concrete testing to ensure that it complies with the requirements of the project specification. The cube test must be undertaken under the control of a competent person. This usually means a locally registered engineer and they must follow exactly the requirements and procedures set out on the code.

f. With reference to the case of King’s Buildings Arcadia Nursery – University of Edinburgh (found at https://www.breeam.com/case-studies/) which describes where a significant decision was made to select materials that scored very highly in the Green Guide, including a large amount of responsibly sourced, legally harvested and traded timber from a sustainable source.

To achieve the BREEAM credit, it was necessary to prove that the source was either an independently verifiable legal and sustainable sources or Forest Law Enforcement, Governance and Trade (FLEGT) - licensed timber or equivalent sources.

g. Columns fail by buckling when their critical load is reached. Long columns can be analysed with the Euler column formula

F = n π2 E I / L2

where

F = allowable load (lb, N) [ to be calculated]

n = factor accounting for the end conditions [Will be 4, as fixed as both ends]

E = modulus of elasticity (lb/in2, Pa (N/m2)) [Young’s Modulus given as 35GPa]

L = length of column (in, m) [Given as 4m]

I = Moment of inertia (in4, m4) [ From tables - 250 10-8 m4]

Thus F = (4 x π2 x (35 x 109) x (250 x 10-8)) / 42 = 215.7kN

Task 4

a. Whilst human comfort is subjective and different people may desire different conditions. Some parameters associated with the internal environmental conditions are driven by health and safety criteria and are included in legal requirements. Others are guided by reputable guidance and reference documents. In the UK, the Chartered Institute of Building Services Engineers (CIBSE) are generally used for this purpose.

Temperature

Both dry and wet-bulb temperatures need to be considered. The dry bulb temperature is not dependent on the amount of moisture in the air, whereas the web-bulb temperature is.

Relative Humidity

Relative humidity is a ratio the water vapour held in the air as a percentage of the total possible: for example, if the relative humidity is 66% then the air contains two-thirds of the possible water. If it was at 100%, it would be fully saturated and there would be rain. Relative humidity varies with air temperature. In the UK humidity control is not generally required except for areas where there are processes whose success is critical on humidity control: for example, semi-conductor fabrication plants, operating theatres (Jones, 2007).

Radiant temperature

Mean radiant temperature (MRT) is concerned with the average temperature of the surfaces which surrounds a particular point, with which it will exchange thermal radiation. If the point is exposed to the outside, this may include the sky temperature and solar radiation (Watson and Chapman, 2002).

The mean radiant temperature is that uniform temperature of an imaginary black enclosure resulting in the same heat loss by radiation from the person in the actual enclosure. This is a very arduous process.

Ventilation

Ventilation is concerned with removing stale air in a space by introducing fresh air. This ensures that there is adequate oxygen for respiration. It also contributes to:

Maintaining ambient temperature and relative humidity, and creating some air movement to improve the comfort in the space; Removes or dilutes airborne contaminants: for example, C02, bacteria, moisture, odours, smoke; and Reduces potential fire or explosion hazards.

Whilst Part F of the Building Regulations provides some requirements for ventilation rates, its main focus is on residential properties. For offices it does quote a rate of 10l/sec/person. However, it does refer to CISBE Guide B (Ken, 2005) which is much more detailed for specific areas.

Reverberation

Sound waves in an enclosed space will be partially reflected and partially absorbed by all the surfaces: for example, floor, walls, ceiling, doors, windows, furniture, curtains, people and even any unintentional openings. Reverberation is related to the time taken for a particular sound to decay or ‘fade-away’ by 60dB after an abrupt termination (Moiseev, 2011). The reverberation time of a room or space is defined as the time it takes for sound to decay by 60dB. For example, if the sound in a room took 10 seconds to decay from 100dB to 40dB, the reverberation time would be 10 seconds. This can also be written as the T60 time.

Illumination

Illumination (or lighting) for any area is specified using a range of parameters including:

Maintained illuminance which is the quantity of light energy on a designated task level where the light is required.

Glare index provides a limit on the unnecessary contrast or an inappropriate distribution of light sources that distracts or limits the ability to distinguish detail within the task. Colour rendering index (CRI) which measures how well lamps reproduce could compared with the colour under natural daylight as illustrated below:

It should be noted that the CIBSE SLL Code (Raynham, 2012), schedules numerous types of area, task and activity and it is important to further check based on the exact use of the building.

b. The following equation will be used to determine the heat requirement from each surface:

Ht = U A dt

where

Ht = heat flow (Btu/hr, W, J/s)

U = overall heat transfer coefficient, "U-value" (Btu/hr ft2 oF, W/m2K)

A = wall area (ft2, m2)

dt = temperature difference (oF, K).

The value will be calculated for each surface and summated.

Thus, the required heat is 45.52KW

c. The following equation will be used to determine the heat requirement:

Eh = c m ΔT

Where

Eh is measured in joules

m is measured in kilograms

ΔT is measured in °C [given as 20oC]

c is measured in joules/kg °C [given as 1]

First calculate the mass flow rate

120 people @8l/s/person = 1200 l/s which is 1.2m3/second

Then convert to Kg/second at air temperature of 0oC ( where the density is 1.2922 kg/m3),

Mass = density x volume = 1.2922 x 1.2 = 1.5507 Kg/sec

Input to calculation

Eh = 1 x 1.5507 x 20 = 31.01kW

d. This calculation will make use of Sabines formula (Millington, 1932) as follows:

Where

RT60 is the reverberation time (to drop 60 dB)

V is the volume of the room

c20 is the speed of sound at 20°C (room temperature) [the speed of sound at 20°C is 343 m/s]

Since we know the speed of sound at 20°C is 343 m/s, we can do a little maths and reduce the formula to:

Sa is the total absorption in sabines can be calculated as follows:

The Volume of the space is 17 x 30 x 8 = 4,080m3

Therefore

RT60 = 0.161s/m 4080 m3 / 789 sabins = 0.833 seconds

e. If the hall contained the maximum number of people the reverberation time would decrease, as people are able to absorb and hence prevent the reflection of sound and thus will contribute to the damping. Of course, if they were all wearing suits of armour, which would reflect the sound, then the reverberation time would increase.

f. There are a range of measures that could be used to minimise energy in the building (Bownass and Bownass, 2002). For example;

Better insulation and U values and more efficient building services equipment specified (Sadineni et al, 2011);

Use of renewables (solar water heating, PV panels) to reduce the demand on the public utilities supplies; and

Educating the users to use the manage the lighting, heating and cooling to reduce losses.

References

Bownass, D. and Bownass, D., 2002. Building services design methodology: a practical guide. Routledge.

Costanza, R., 1980. Embodied energy and economic valuation. Science, 210(4475), pp.1219-1224.

Kodur, V.K.R., 1999. Performance-based fire resistance design of concrete-filled steel columns. Journal of Constructional Steel Research, 51(1), pp.21-36.

Kremer, P.D. and Symmons, M.A., 2015. Mass timber construction as an alternative to concrete and steel in the Australia building industry: a PESTEL evaluation of the potential. International Wood Products Journal, 6(3), pp.138-147.

Millington, G., 1932. A modified formula for reverberation. The Journal of the Acoustical society of America, 4(1A), pp.69-82.

Polder, R.B., 2001. Test methods for on site measurement of resistivity of concrete—a RILEM TC-154 technical recommendation. Construction and building materials, 15(2-3), pp.125-131.

Russell, R.M., Maidment, S.C., Brooke, I. and Topping, M.D., 1998. An introduction to a UK scheme to help small firms control health risks from chemicals. The Annals of occupational hygiene, 42(6), pp.367-376.

Sadineni, S.B., Madala, S. and Boehm, R.F., 2011. Passive building energy savings: A review of building envelope components. Renewable and sustainable energy reviews, 15(8), pp.3617-3631.

Tuutti, K., 1982. Corrosion of steel in concrete.

Watson, R.D. and Chapman, K.S., 2002. Radiant heating and cooling handbook (pp. 5-251). New York: McGraw-Hill.