The Importance of Construction Mock-ups and Trials

Document type: Technical Paper
Author: Stuart Moxton IEng MCIOB MICE, Simon Atherton BEng, ICE Publishing
Publication Date: 03/11/2014

1 Star2 Stars3 Stars4 Stars5 Stars (Be the first to rate this document)
Loading...

  • Abstract

    The objective of this paper is to consider the importance of both full scale construction mock-ups and smaller trial samples to a large construction project such as Crossrail. The paper identifies the range of benefits and advantages to be gained by relatively small investment in mock-ups and trial samples and the enhanced value they can add to the final project.

     

  • Read the full document

    Introduction

    The objective of this paper is to consider the importance of both full scale construction mock-ups and smaller trial samples to a large construction project such as Crossrail. The paper identifies the range of benefits and advantages to be gained by relatively small investment in mock-ups and trial samples and the enhanced value they can add to the final project.

    The benefits of using mock-ups and trial samples have been identified in the following aspects of construction projects:

    • Buildability
    • Health and Safety
    • Protection of the Environment
    • Access Requirements
    • Sustainability
    • Aesthetics and Appearance
    • Benchmarking
    • Maintenance
    • Publicity

    Referring specifically to the Crossrail station mock-up further benefits have been achieved following completion of the model when it was widely publicised and a media event was held which included print and digital media. An item was also broadcast to millions of viewers in the London area, giving customers a vision of the future.

    Visits to the model allow visualisation and assessment of the proposed final product in a unique way with a level of reality that cannot be provided by CAD, drawings or even 3D computer modelling.

    To date over 500 people have visited the mock-up model including:

    • Disability interest groups
    • Designers and project teams
    • Local authorities, government and councillors
    • Potential sub-contractors and materials suppliers
    • Key personnel from TfL
    • Media

    It is evident from the analysis of the benefits presented in this paper, that construction of a full-scale mock up, and testing on both the model and on the associated trial samples, can lead to reductions in construction costs, improvements in project programme management and delivery within planned timescales, reductions in unforeseen errors, increased safety during construction and can help reduce the impact on the environment. Ultimately, reviewing the mock-up of the finished product with the client before construction commences should ensure that there is greater transparency and all expectations are achieved.

    7C_017 Figure 1.jpg

    Photo 1 – View of station platform

    Crossrail is a major new railway currently under construction in South East England. It includes the construction of 21 km of new tunnels under central London, connecting the Great Western Main Line near Paddington and the Great Eastern Main Line near Stratford, and is currently planned to open in 2018.

    The proposed total budget is in the region of £15 billion with new Crossrail stations, costing in the region of £2 billion being constructed along the central route at Paddington, Tottenham Court Road, Bond Street, Farringdon, Liverpool Street, Whitechapel and Canary Wharf.

    Technology Centre have constructed a full-size replication of a Crossrail station platform to provide a tangible preview of the future Crossrail station environment and passenger experience. It will aid future design decisions on aspects such as cladding type and geometry, flooring, lighting, platform edge screen, CCTV, seating, ventilation, signage, space management, advertising and art.

    This model has so far proved invaluable to the project in enabling people to visualise layouts, comment on finishes, experience the space and view lighting options. This is essential as it provides opportunity at an early stage of the project to comment on general impressions of the general layout and environment, to determine materials selection, to develop maintenance programmes, reduce risk, ensure sustainability and enable stakeholder buy-in.

    The construction of this mock-up will be followed up with the construction of a number of smaller scale trial samples using real materials. These samples can be used as bench marks as well as aids for testing, training and process development.

    7C_017 Figure 2.jpg

     Photo 2 – Totem

    7C_017 Figure 3.jpg

                            Photo 3 – Cladding & totem 

    When undertaking a construction project both the client and the main contractor will have a hierarchy of targets and constraints to consider. The primary driver for all commercial companies is profitability, however other important considerations are health and safety, Corporate Social Responsibility, meeting all the client’s specifications and requirements and the company’s reputation in the wider world.

    When a large, costly or complicated construction project is planned it is often beneficial to consider smaller scale trials or mock-ups prior to the construction phase commencing.

    Some of the rewards of this approach can include:

    • Honing construction techniques allowing the main project to be built in a shorter timescale at a reduced cost, with less wastage and a smaller impact on the environment and the neighbourhood.
    • Assessing buildability, enabling obstacles to the construction process to be foreseen and designed out preventing delays and increased costs during the construction phase.
    • Assessing safety hazards in a small controlled environment so they can be controlled or eliminated across the project, reducing injuries, costs and delays to the programme.
    • Enable training of the workforce to reduce defects and improve efficiency.
    • Ensuring the finished project will match the anticipation of all interested parties, reducing costs and extended programmes associated with modifications and late specification changes.

    Buildability

    The use of mock-ups as a preliminary step in the construction process is an invaluable tool for ensuring buildability. Difficulties encountered and mistakes made building the mock-up can then be avoided on the full-scale construction phase. Undertaking small scale trials will prove whether processes that appear practical on paper are equally so in reality or whether modifications are required. For example, can work areas be accessed to undertake works and if so what plant will be required to undertake the works.

    Every construction company should be aiming for a target of zero defects, getting everything right the first time therefore removing the costs of “putting right” as well as reducing delays to the programme. One method of working toward this goal is the use of mock-ups and trials as a development and training aid. Problems can be identified and designed out through design improvements, better sequencing, better training and ensuring that the most appropriate construction methods and materials are employed.

    Significant savings can be made by refining the construction process to ensure that the correct plant is made available when it is needed. In some cases a trial build followed by consultancy with the workforce can lead to small modifications in process or design that reduce the need for expensive plant or access equipment.

    Modifications to the construction methods and procedures can be obtained by using mock-ups to assess the advantages of implementing off-site pre-fabricated components or alternatively reducing the size of components being brought to site. By assessing timescales and scheduling alternatives it may be possible to optimise delivery schedules during the construction phase, ensuring the required materials are always delivered in time without having materials arrive before they are required leading to storage problems where space is at a premium and potential damage to materials held in storage.

    A major cost in construction can be remedial works or undertaking modifications. Trials and mock-ups enable improvements to the construction process to be achieved by identifying and illuminating any “mistakes” in a controlled environment before full-on construction begins. This leads to a reduction in the risk of errors being made, which can add to the construction cost and programme. Therefore greater control can be achieved during the actual project construction, with a safer, right first time method of work, with no need for reworks resulting from the time spend preparing the process of work on the mock-up.

    Health and Safety

    Health and safety is of major importance both in the construction phase of the project and after hand-over throughout the life of the facility. The use of a mock-up both allows safe methods of work to be developed where construction methods are innovative or a development is unique or ground-breaking and permits potential hazards to be identified and eradicated prior to the onset of the main construction phase of the project.

    Construction phase health and safety goes hand in hand with buildability. Certain activities will have safety risks inherent in them such as working at height, hot works, transportation of heavy items and traffic movements both on-site and in the adjacent area with public access.

    The use of small scale trials on mock-ups can be used to establish the safest ways to undertake operations, identify unforeseen hazards which can then be guarded against and explore whether certain activities can be avoided.

    There is generally considered to be a hierarchy of health and safety control measures with the primary option being the removal of the hazard. A good example of this would be working at height; if the works can be done at ground level then the hazard of working at height is removed.  Experimentation with a mock-up can investigate if assembly is possible at ground level with a completed component then lifted into place. A ‘dry run’ can establish the feasibility of this and investigate whether other enabling works or alternative sequencing can facilitate this approach.

    A major safety issue can be accessibility, how accessible is the work area, what access equipment is required, how much space is available to work in. Accessibility can be maximised by experimentation with a mock-up to optimise the sequencing and construction methods and to discover the most effective means of access.

    Training can be undertaken utilising a full scale mock-up allowing the workforce to be instructed in, and practice using, safe working techniques in a safe and controlled environment. Mistakes can be made in a controlled environment with no repercussions in contrast to errors occurring during the construction phase, which are best avoided.

    Protection of the Environment

    The use of trials and mock-ups can be useful for reducing environmental impacts. By developing best practices the use of materials can be reduced, the amount of waste can be reduced and energy usage can be reduced.

    Trials of equipment and working practices can be developed within a mock-up to determine the best methods of reducing noise, dust and other environmental impacts during the construction process. By developing means of optimising sequencing, the number deliveries can be reduced and storage of materials on site can be reduced, which will help to improve the environmental impact of construction works in and around the construction site.

    Access Requirements

    There are few buildings in the current age that are not required to be accessible to all regardless of age or mobility. There are legal requirements detailed in both the Disability Discrimination Act 2005 and more recently The Equality Act 2010 to ensure that access is readily available for everyone regardless of mobility or other disability. Part M of the Building Regulations details many access requirements which must be complied with. Any company having a regard to Corporate Social Responsibility will have a moral duty to ensure a policy of accessibility for all. This would normally be a desire of not only their boards of directors but also of shareholders and clients. Commercial operations including retail outlets such as department stores, shopping centres and other shops, transport terminals such as airports and stations, entertainment facilities such as cinemas, sports centres, theatres, museums and galleries will all have a vested interest in ensuring their potential customers are not excluded from their business.

    Under the Equality Act 2010 a person is considered to have a disability if they have a physical or mental impairment and the impairment has a substantial and long-term adverse effect on their ability to perform normal day-to-day activities. To many people the stereotypical image of a disable person is someone in a wheelchair but the definition is clearly much wider. Disability could include the infirm such as those able to walk but with reduced mobility. A disability may be visual, the blind or partially sighted, or it could include hearing difficulties. In cases it may include those with learning difficulties and the elderly.

    The challenge, therefore, to clients, planners, architects, designers and others concerned in the construction process is to design, build and deliver a facility which is accessible to all.

    There are many documents published giving guidance on access requirements but while some measures are straightforward such as ensuring a doorway is wide enough other issues are more complex and may not manifest themselves in a desk top study.

    A full scale mock-up allows a range of persons with relevant expertise and interest in disability equality, access and service provision to appraise and evaluate the proposed arrangements allowing design modifications at an early stage should they be considered beneficial. A liaison with relevant interest groups such as the Disabled Experts Reference Group (part of the BSI Consumer & Public Interest Network) or local access groups can be highly beneficial.

    Physical obstacles and restrictions are the most obvious; helping to determine early on if the access is wide enough, the access ramps are at a suitable inclination and are not too long without a landing, if adequate hand-holds are provided, are of the right kind and are at the correct location. In addition the mock-up will help to identify if there are physical obstructions which could be relocated or redesigned and if the floor is a suitable surface.

    Visual aspects can also be determined earlier on with a mock-up model, including the correct lighting levels, planned access route acceptance and if the signage is clearly visible.

    Personal perception of the future customer can also be determined early on within the full-scale mock-up. Confirmation of the whether or not the access appears straightforward and manageable or if the layout is confusing or daunting in any way.

    Finally, a mock-up can identify any unforeseen pit-falls. If it is possible to go wrong, to get a wheelchair stuck, to take a wrong turn or if there are any trip hazards which could conceivably be encountered, then a mock-up of a typical platform and underground access section would give the added benefit of identifying these issues before full-scale construction takes place.

    Sustainability

    Construction mock-ups and trials are a very good example of sustainable solutions in practice through delivery of ‘triple bottom line’ benefits based on the widely recognised three pillars of sustainability: the Economical; Environmental and Societal factors.

    Economical

    The lessons learnt from other sectors such as the car industry and manufacturing sectors show that prototypes are an essential norm. Construction mock ups and trials reduce financial and performance risk, facilitate faster ways of working, understanding issues and scope. Therefore, such mock ups should be seen as an investment for project improvement and cost reduction rather than an additional cost.

    Environmental

    Construction Mock-ups and trials facilitate best practice resource efficiency and less waste through optimum design. Currently WRAP, a government funded organisation are strongly promoting resource efficiency research and best practice implementation. Best practice eventually finds its way to standard good practice, thus making more widespread reductions in environmental impact.

    For repeat items such as installation of signs, lighting posts and tunnel sections, the reductions in CO2 and environmental impact can be determined within a mock-up. These reductions and the resultant savings can be multiplied many times over. For technically complex one-off builds, the environmental savings can be seen by understanding potential environmental impacts due to rebuilds.

    Mock-ups also give the added benefit of focusing attention on reducing environmental impact in many forms, including:

    • Less base material
    • Less waste
    • Standardisation
    • Optimum design
    • Reducing the need to rebuild
    • Consideration of whole life cycle ‘cradle to grave’
    • Understanding carbon impact and possibilities for reduction.

    Societal

    Construction Mock-ups and trials have proven to be an effective means of obtaining buy in of project stakeholders and investors in future projects.

    Opinions of designers, experts and stakeholders can be gathered and acted upon before it gets built and becomes public. Getting this buy-in helps the construction move forward more positively and with more certainty.

    Not just technical inputs but also the ‘softer’ side of aesthetics colour and form can be addressed. Getting it right first time, the avoidance of errors leads to client satisfaction and reassurance for stakeholders.

    Using this sustainable solutions approach not only ensures an economically viable, environmentally sensitive and socially acceptable outcome, furthermore, the three factors help each other in such a way to deliver a ‘triple bottom line’ win.

    Aesthetics and Appearance

    The aesthetics of a building, facility or space can only ever be subjective but there will in most cases be a general consensus on what works and is pleasing to the eye and what is less appealing. Aesthetics is based on a multitude of elements including colour, texture, pattern and form. It will be affected by lighting, by layout, by the materials used and by colour schemes utilised. There can only ever be one way to assess aesthetics and that is to experience the layout first hand.

    A full-scale mock-up allows a spectrum of people to walk through and gain an impression of a proposed finish and to comment on thoughts and feelings. Various options can be trialled to see whether a proposal will be acceptable and to see what colour schemes are attractive to prospective users of the space.

    Aesthetic trials can be of economic benefit, it may be acceptable in some locations to use a cheaper finish; a painted or plastered concrete rather than expensive cladding may work in one location but not another. If the finish is to be bare concrete, can simple sprayed concrete be left on show or will it need floating off, painting or even covering completely. While the client will want a finished facility that is aesthetically attractive and pleasing, it may not be necessary to spend excessive amounts to achieve a satisfactory finish and different locations as well as different usages may dictate what is acceptable.

    Benchmarking

    The basic station design and layout developed at Technology Centre will be used as a model for six new underground stations with some design aspects possibly used as a standard for works undertaken at existing stations to be served by Crossrail. There is therefore a desire for consistency with the as-built stations matching all expectations. Trial samples constructed at Technology Centre can be referred back to as benchmark examples, furthermore construction of a trial sample demonstrates the quality which can be expected in the finished environment as well as enabling methods of achieving the desired standard to be developed.

    Standards benchmarked can include:

    • Aesthetic appearance – Colouring, Lighting, Signage, General impressions.
    • Tactile aspects – Textures, Slip resistance, Abrasive surfaces.
    • Quality of Workmanship
    • Ease of Cleaning

    Maintenance

    Throughout the life of each station a programme of planned and reactive maintenance will be required. Maintenance will be undertaken by a wide range of contactors ranging from basic cleaners to electricians and specialist engineers. There are both costs and timescale issues associated with maintenance whether planned or reactive. The costs associated with maintenance can be minimised by reducing the level of maintenance required, increasing the ease of maintenance and reducing the duration of the maintenance period.

    Maintenance can be expected to include the following activities:

    • General Cleaning
    • Specialist Cleaning
    • Graffiti Removal
    • Replacement of consumable such as lighting components
    • Replacement of damaged items due to vandalism or accident
    • Replacement of time expired items – general refurbishment of signs, furniture etc.
    • Routine servicing and inspections – electrical installations etc.
    • Changing advertising

    Reactive maintenance can be reduced by ensuring components are as durable as possible and with high resistance to attack by vandals or accidental damage. Specialist cleaning and finishes which are relatively easy to clean and will not be permanently degraded by contact with various the substances they are likely to encounter throughout their life.

    Ensuring safe access is readily available to undertake regular maintenance tasks will assist in keeping maintenance to simple routine operations without the need for extended timescales, increased manpower and corresponding increased costs. This may be achieved by small modifications to design to ensure that access is possible with standard equipment.

    Test and Evaluation Schedule

    The materials testing schedule for the Crossrail station mock-up and trial samples is varied and extensive. An overview of the testing is presented below, this is not necessarily exhaustive as additional testing can be undertaken, including bespoke testing to client’s specifications.

    • Impact Testing of a full size lower interface zone GFRC panel assessed against BS 8200:1995 “Code of practice for design of non-loadbearing external vertical enclosures of buildings” Appendix G: Hard and soft body impact tests.
    • Impact Resistance testing to BS EN 12372:2006 Natural stone test methods. Determination of flexural strength under concentrated load of Terrazzo and Granite floor tiles.
    • Abrasion Resistance testing to ASTM / C944M – 99 (2005) E1 – Standard Test Method for Abrasion Resistance of Concrete or Mortar Surfaces by Rotating – Cutting Method undertaken on polished and sandblasted finish GFRC flat test samples.
    • Abrasion Resistance testing to BS EN 14157:2004 Natural stones. Determination of abrasion resistance of Terrazzo and Granite floor tiles.
    • Cleanability (dust & dirt) assessment against document E3834 A3– Station Cleaning: Attachment 2 Walls, Ceilings and Soffit [Dust, hand and shoe mark removal] of GFRC panels, Terrazzo flooring and Granite flooring.
    • Cleanability (common food and beverage spillages) assessment against document E3834 A3 – Station Cleaning: Attachment 2 Walls, Ceilings and Soffit [Cleaning of spillages of Cola, Coffee, Tomato ketchup sauce] of GFRC panels, Terrazzo flooring and Granite flooring.
    • Cleanability (Chewing gum) assessment against document E3834 A3 – Station Cleaning: Attachment 2 Walls, Ceilings and Soffit of GFRC panels, Terrazzo flooring and Granite flooring.
    • Cleanability (Body Fluid Spillages – blood stains) assessment against document E3834 A3 – Station Cleaning: Attachment 2 Walls, Ceilings and Soffit of GFRC panels, Terrazzo flooring and Granite flooring.
    • Cleanability (Anti-Graffiti) assessment against document E3834 A3 – Station Cleaning: Attachment 2 Walls, Ceilings and Soffit and “Updated Anti-graffiti Testing Criteria” of polished and sandblasted finish GFRC test samples with surface sealant and anti-graffiti coating
    • Bomb Blast Testing of components
    • Abrasion Resistance of Anti-scratch coatings used on PES wall passenger interface zone, fire hydrant cabinet, balustrades, escalator side panels assessed against DIN52348 – Testing of glass and plastics; abrasion test; sand trickling method.
    • Visual appearance assessment of Anti-scratch film versus Permanent anti-scratch glass coating.
    • Slip Resistance testing in accordance with BS 7976 of Terrazzo and Granite floor tiles.
    • Spectrometer test of GFRC panels, Terrazzo and Granite floor tiles in accordance with BS8300:2009 A1:2010 Design of buildings and their approaches to meet the needs of disabled people – Code of practice.
    • Spectrometer testing to confirm stainless steel handrail finish does not create reflective surface to cause hazard to partially sighted customers in accordance with BS8300:2009 A1:2010 Design of buildings and their approaches to meet the needs of disabled people – Code of practice.
    • DDA – ‘Warm to touch’ assessment of handrail in accordance with BS 5395-1:2000: Stairs, ladders and walkways. Code of practice for the design, construction and maintenance of straight stairs and winders. A heat conductivity test to confirm alternative handrail finish is made of low conductive material to satisfy the “warm to touch requirement”.
    • General Design and Detailing Assessment of glass and stainless steel handrail. Assessment of robustness and ergonomics – Visual and tactile assessments on design and finishing details of glass and handrail elements to ensure elements shall be reasonably robust against removal by general hand held tools by the public and checking elements have no sharp edges, projections or finger traps.
    • General Design and Detailing Assessment of glass and stainless steel handrail. Assessment of robustness and ergonomics – Visual and tactile assessments on design and finishing details of glass and handrail elements to ensure elements shall be reasonably robust against removal by general hand held tools by the public and checking elements have no sharp edges, projections or finger traps.
    • Design Assessment – Confirmation that the current design allows for replacement of a single glass pane or railing section without extensive disturbance of the adjacent member.

    Conclusions

    Following completion, the model was widely publicised and a media event was held which included print and digital media, including presentation of information and views of the model on the Crossrail website: http://www.crossrail.co.uk/route/stations. Millions of viewers and future customers in the London area have also been given a vision of the future when a television news story was broadcast from the Crossrail mock-up.

    To date over 500 people have visited the model including:

    • Disability interest groups
    • Designers and project teams
    • Local authorities, government and councillors
    • Potential sub-contractors and materials suppliers
    • Key personnel from Transport for London (TfL).

    Visits to the model have enabled the visualisation and assessment of the proposed final product in a unique way with a level of reality that cannot be provided by Computer Aided Design (CAD), drawings or even 3D computer modelling.

    Testing undertaken both on the model and on trial samples can reduce costs and timescales, reduce errors, increase safety and help reduce the impact on the environment. Ultimately allowing the client to see the finished product before construction begins should ensure that all expectations are met.

  • Authors