Lateral Torsional Buckling in Beams

Lateral Torsional Buckling in Beams = Lateral Deflection + Torsion

Lateral torsional buckling occurs when an applied load causes both lateral displacement and twisting of a member. This failure is usually seen when a load is applied to an unconstrained, steel I-beam, with the two flanges acting differently, one under compression and the other tension. ‘Unconstrained’ in this case simply means the flange under compression is free to move laterally and also twist. The buckling will be seen in the compression flange of a simply supported beam.

Lateral Torsional Buckling of a Beam Girder

WHAT IS Lateral Torsional Buckling?

Lateral torsional buckling may occur in an unrestrained beam. A beam is considered to be unrestrained when its compression flange is free to displace laterally and rotate. When an applied load causes both lateral displacement and twisting of a member lateral torsional buckling will occur. Figure shows the lateral displacement and twisting experienced by a beam when lateral torsional buckling occurs.

What causes the lateral deflection?

The applied vertical load results in compression and tension in the flanges of the section. The compression flange tries to deflect laterally away from its original position, whereas the tension flange tries to keep the member straight. The lateral movement of the flanges is shown in Figure. The lateral bending of the section creates restoring forces that oppose the movement because the section wants to remain straight. These restoring forces are not large enough to stop the section from deflecting laterally, but together with the lateral component of the tensile forces, they determine the buckling resistance of the beam.

Torsional effect

In addition to the lateral movement of the section the forces within the flanges cause the section to twist about its longitudinal axis as shown in Figure. The twisting is resisted by the torsional stiffness of the section. The torsional stiffness of a section is dominated by the flange thickness. That is why a section with thicker flanges has a larger bending strength (pb) than the same depth of section with thinner flanges

cause of lateral deflection in beam

How to prevent Lateral torsional buckling

The best way to prevent this type of buckling from occurring is to restrain the flange under compression, which prevents it from rotating along its axis. Some beams have restraints such as walls or braced elements periodically along their lengths, as well as on the ends. This failure can also occur in a cantilever beam, in which case the bottom flange needs to be more restrained than the top flange.

Torsion in Beam

The location of the applied load is a major concern. If the load is applied above the shear center of a section it is considered a destabilizing load, and the beam will be more susceptible to lateral torsional buckling. Therefore loads applied at or below the shear center is a stabilizing load, with little risk of the buckling occurring.

Torsion in Beam



Release date 12 January 2020

Typical Construction Costs of Buildings

Below is a guide to typical construction costs of various buildings per m2 of gross internal floor area (internal area measured over internal walls and partitions, stairwell openings etc). The costs are typical guide costs for a building of the size stated, constructed to a typical or mid-range specification. Building size and shape, number of storeys, ground conditions, design and material specification can all have a significant impact on costs. It is quite possible for costs to vary from the guide costs given here, perhaps by +20% or more and even this higher figure is not absolute but a guide only.

Costs are set at current index 188 – 1Q2020 (Year 2000 = 100), at UK national average (index 100). See the Construction Indices, the Regional Variations and the Project Value Adjustments pages for more details. The costs are for the building only, inclusive of preliminaries and contractor’s overheads and profit. The costs are exclusive of furnishings, external works, allowances for risk (contingencies), fees and VAT.

If you don’t know any better, we would typically add a further 20% of the costs below to cover the possible costs of external works (hard pavings, landscaping, external fences and walls, etc., foul and surface water drainage, and external services) and to the new sub-total figure a further 15% to cover risk (contingencies). This is only very much a rough guide and depends very much on the size of the site associated with the building and the level of specification and complexity of the external works. Professional fees can be anything from 5% to 10% depending on the size of the project – generally the larger the project the smaller fee percentage.

Building prices can be influenced significantly by local conditions, local market conditions, size and specification. The prices given here are intended only as an indicative guide and should be used with caution as prices outside these ranges can be encountered in meeting local conditions and specific client requirements.

An example of how a construction works budget may be put together is given at the end of this page.

Industrial buildings
Factory, light industrial, including office accommodation (4.5m high) 5000m2 £940
Warehouse including office accommodation (7.3m high) 5000m2 £980
High bay warehouse including office accommodation (excludes racking), (21.0m high) 10000m2 £1240
Distribution centre including office accommodation (15.0m high) 71750m2 £660
Small start-up units (5.0m high) 900m2 £1100
Administrative buildings
Office, low rise, non-air conditioned, basic specification 3000m2 £1790
Office, low rise, non-air conditioned, higher specification 3000m2 £2130
Office, low rise, air conditioned, basic specification 3000m2 £1960
Office, low rise, air conditioned, higher specification 3000m2 £2330
Office, high rise, non-air conditioned, basic specification 10000m2 £1650
Office, high rise, non-air conditioned, higher specification 10000m2 £1960
Office, high rise, air conditioned, basic specification 10000m2 £1810
Office, high rise, air conditioned, higher specification 10000m2 £2150
Shop unit (block of three small units) 500m2 £1820
Shop unit with flats above 1500m2 £1560
Shop unit with offices above 1000m2 £1700
Retail warehouse 5000m2 £980
Health and welfare buildings
General hospital 10000m2 £2750
Psychiatric ward 1500m2 £2970
Pathology lab 1200m2 £3150
Health centre 2000m2 £2260
Hospice 3000m2 £2060
Nursing home 2000m2 £2240
Home for the elderly 2000m2 £2230
Home for the mentally ill 5000m2 £2400
Refreshment, entertainment and recreation buildings
Restaurant 700m2 £2100
Community centre 500m2 £2360
Leisure centre with swimming pool 6000m2 £2660
Sports hall with swimming pool 9000m2 £2720
Sports changing pavilion 200m2 £1870
Library 700m2 £2020
Youth club 800m2 £1960
Educational, cultural and scientific buildings
Nursery school 250m2 £2830
Primary school 2000m2 £2160
Secondary school 4000m2 £1940
College, non-air conditioned 5000m2 £1790
College, air conditioned 5000m2 £1960
Residential buildings
Estate housing 800m2 £1230
Detached house 200m2 £1640
Apartment block 7000m2 £1950
Hall of residence 1500m2 £2320
Student residence 8000m2 £1910
Sheltered housing 3000m2 £2110
Hotel, air conditioned 5000m2 £2530

If you wish to what see costs below comprise why not download our app and create a cost model yourself. It’s simple, easy to do, quick and completely free of charge! Go to our download section now and use our wizard to create your cost model from scratch.

Example of putting a budget together

The following is an example of how an early cost advice budget may be put together when all that is know about the project is building size (gross floor area), location and an indicative start of construction date.

This example is for a proposed new office block in York, 2000m2 gross floor area, with a proposed construction start date of January 2021.

Base cost from cost per m2 table above
Office, low rise, air conditioned 2000m2 x £1,960 3,920,000
Adjustment for location (York = 96) 0.96
Adjustment for project value
Base cost factor (3000m2 x £1,960 = £5,880,000) 0.91
Cost factor for this project (base value £3,763,000) 0.93
Adjustment (0.93 – 0.91) / 0.91 2.20% 83,000
Adjustment for construction start date
Current tender price index January 2020 188
Forecasted tender price index January 2021 192
Adjustment (192 – 188) / 188 2.13% 82,000
Allowance for external works say 20% 786,000
Allowance for risk say 15% 7078,000
Indicative total building works cost £5,500,000

Estimate base date: 12 January 2020.

Falls and drainage

It is a requirement of Building Regulation Part H that adequate provision is made for rainwater to be carried from the roof of the building.

It is generally considered good practice for flat roofs to be designed to clear surface water as rapidly as possible. According to BS6229 & BS8217, flat roofs should be designed with minimum falls of 1:40 to ensure a finished fall of 1:80 can be achieved, allowing for any inaccuracies in the construction.

Water ponding on membrane roofs should be avoided because:

  • It encourages the deposition of dirt and leaves which can be unsightly, may obstruct outlets and /or become a slip hazard.
  • In the event of damage, the interior may suffer greater water ingress.
  • It increases the dead load and may cause progressive deflection of the deck.
  • Ice may be a slip or wind hazard during the winter months.
  • Roofs with extensive ponding require increased maintenance input.

Falls in the structure can be achieved by adjusting the height of the supporting beams or purlins, by using tapered supports, or by the addition of firring pieces before the deck is laid. In the case of a cast in-situ concrete slab, falls are normally provided by use of a screed.

Tapered insulation

Tapered insulation systems are a lightweight, convenient and cost effective alternative method of providing falls to the roof and can be used with our reinforced bitumen membrane (RBM) and synthetic single ply roof systems.


Drainage needs to be provided via internal rainwater outlets and downpipes or via external guttering systems or hoppers. Even if a roof is very small, it is recommended there are at least two drainage points in case one becomes blocked. Internal gutters linking internal outlet positions should be at least 500mm wide.

BS EN 12056-3 and the Building Regulations Approved Document Part H contain relevant design information to enable rainfall calculations to be undertaken and give design principles for gutters and downpipes. Alternatively, most drainage component manufacturers will make recommendations regarding the type, size and location of their products for any given roof project.

BIM File Naming

File Naming


The method for naming a file is detailed within BS 1192:2007+A2:2016 Collaborative production of architectural, engineering and construction information – Code of practice.

Before we get into the detail of how the naming works, a couple of key points:

  • To comply with Level 1 BIM (and subsequently Level 2 BIM) standard naming applies to all project documents (and not just drawings and models)
  • Project codes (ideally) should be defined by the client within the Employer’s Information Requirements (EIR) or alternatively are defined within the BIM Execution Plan (BEP)
  • The fields required for file naming (and only those required) are clearly defined within the code of practice. All fields are required in the defined order (within the exception of the optional and metadata fields which may be omitted)

So, to deliver BIM level 2 all project document files should be named in accordance with BS 1192, no alternative methods are accepted. However, in practice not all the file naming requirements will work for every project any deviation should be clearly referenced within project documents (EIR and BEP).

The arrangement for file naming, with each field separated by a hyphen (generally the table below and further information applies to the BS 1192 standard coding):

Field Project Originator Volume or System Levels and Locations Type Role Classification Number Suitability Revision Extension Suffix
Example AAA BB 00 01 DR A SL_25_70_47 0001 .pdf
Required or optional Required Required Required Required Required Required Optional Required Optional Optional Required
Characters 2-6 3-6 1-2 2 2 1 character To match the selected classification library 4 integer numeric digits 2 3 – with additional decimals for WIP As applicable application

Project Code

This is an individual code for the project that will be used consistently throughout the project. Ideally the project code should be confirmed at the early stages of the project, ideally by the client and confirmed in the EIR. For a project where a client does not initialise a project wide code, but the design team require a consistent reference, this should be developed by the project team and confirmed within the BEP.

Some large projects, for example a large development, may consist of multiple projects with some of the projects being sub-projects. The project code can be setup to have a main project number with sub-projects identified with an additional reference.

Main project code 101

Sub-project code101a

Originator Code

A unique code for each organisation, so that the originator for the file can identified from the file name.

Volume or System Code

This provides a code for identifying an individual or system. The code should be one to two characters long.

A volume can consist of groupings such as existing building with another code for the proposed new building. Projects can also be split into systems, allowing for items such as primary electrical containment or steelwork to have a unique system code. The codes can be viewed as similar to CAD layers, they allow related parts of a model to be provided as a single volume.

Volume and system codes can also be used to organise large estates with separate volumes being provided for each facility and then sub-volumes for departments. Depending upon the size of the estate this may require additional codes beyond those available with the allowable 2 digits. The use of additional digits would not be in accordance with the requirements of BS 1192, but the standard provides guidance, the use of codes should work for your requirements.

Levels and Locations

Standard codes for levels

ZZ Multiple levels Where the file applies to multiple levels, for example a cross sectional drawing
XX No level For files that are not relevant to the levels, for example specifications or meeting minutes
GF Ground floor
00 Base level For linear assets (for example roads) or where GF isn’t applicable
01 Level one The first level primary level above ground level
M1 Mezzanine one Mezzanine level above level one
M2 Mezzanine two Mezzanine level above level two
B1 Basement one The first level below ground level
B2 Basement two The second level below ground level


A code to identify the type of file, the full list of type codes from BS 1192

Drawings & Models

AF Animation File (of a model)
CM Combined model (federated mutlidiscipline model)
CR Specific for the clash process
DR 2D drawing
M2 2D model file
M3 3D model file
MR Model rendition file (for example thermal analysis)
VS Visualisation of a model


BQ Bill of quantities
CO Correspondence
CP Cost plan
DB Database
FN File note
HS Health & Safety
IE Information exchange file
MI Minutes / action notes
MS Method statement
PP Presentation
PR Programme
RD Room data sheet
RI Request for information
RP Report
SA Schedule of accommodation
CA Calculations
SH Schedule
SN Snagging list
SP Specification
SU Survey


A code to identify the originator of the file, the full list of codes from BS 1192

A Architect
B Building Surveyor
C Civil Engineer
D Drainage, Highways Engineer
E Electrical Engineer
F Facilities Manager
G Geographical and Land Surveyor
H Heating and Ventilation Designer
I Interior Designer
K Client
L Landscape Architect
M Mechanical Engineer
P Public Health Engineer
Q Quantity Surveyor
S Structural Engineer
T Town and Country Planner
W Contractor
Y Specialist Designer
Z General (non-disciplinary)


For standard codes, BS 1192 references codes compliant to BS ISO 12006 and the Uniclass publication. The Uniclass 2015 tables that may be utilised for classification include the Products and Systems tables.

Some points to note

    • Standards have been defined as “an agreed, repeatable way of doing something”, they are not compulsory and should be a live and evolving document. Therefore, deviations from the standards shouldn’t be discounted subject to any deviations providing a meaningful benefit to a project and are clearly defined and agreed
    • Number, PAS 1192-2 identifies 5 digit numerical characters (an additional digit to BS 1192)
    • Number, it’s possible to add in the CI/SfB code into the number character. For example the first two digits relate to the CI/SfB code (for example 43 floor finishes and 90 external works) and the next three digits providing the drawing number within the series.
    • Role, the single letter character can be insufficient for complicated projects with multiple stakeholders and consultants (such as acoustic or catering)
    • Suitability, PAS 1192-2 lists a similar (not the same) suitability codes table and headed as status codes. Status = Suitability Code + Revision Code. Some of differences include:

Standard Coding

Within clause 15 Status, BS 1192 section 15.3 has the following for Standard coding:

Standard status codes for ‘status’: Standard codes should be used for the ‘status’ fields wherever possible.


Standard codes for ‘suitability’: The ‘suitability’ code should be one or two characters. The ‘suitability’ codes given in Table 5 should be used.

Table 5:

enter image description here

The above extract shows that the table is for ‘Standard codes for suitability…’ but the heading of the column above the codes (S0, S1 etc) says ‘Status’.

PAS 1192-2 provides a similar table (although it contains less detail)

Table 3:

enter image description here

The above table makes no reference to suitability (except within Note 2 as listed above) with the codes being clearly referenced as status codes.


What is the difference between zinc-plating & galvanising? And which will be best for your farm fences?

What Does Galvanised Mean?

Galvanisation is when a protective zinc coating is applied to steel or iron, to prevent rusting.

The most common method is hot-dip galvanising. This is when metal parts are fully submerged in a bath of molten zinc.

Zinc plating (also known as electro-galvanising) is a process where zinc is applied by using a current of electricity. While is does provide some rust protection, its thinner coating is not as rust resistant as hot dip galvanising. Its main advantage is it is cheaper and easier to weld.

Be careful when choosing your product! The fact that it says ‘galvanised’ doesn’t mean it’s ‘hot dip galvanised’. Electro-galvanising is another term for zinc plating. So when you see ‘galvanised’ use your newly acquired knowledge to make sure it is hot dip galvanised and not electro-galvanised.

What Can Be Galvanised?

Hot dip galvanising or zinc plating can be used on anything from small nuts and bolts to large beams for buildings. The steel is put in a big bath, where the coating is applied.

If it’s galvanised, it will be dull grey and a little rough. A zinc plated product will be shiny and smooth. A hot dip galvanised product has the best protection against rust, even though it’s a bit ugly.

What Are The Different Galvanisation Processes?

Whether the steel is to be hot dip galvanised or zinc plated it is prepared in a similar way. The steel is cleaned to remove all oils, paint, grease, mill scale (small flakes of metal) and rust in a bath of acid.

Steel, when being hot dip galvanised is dipped into a 450°C bath of molten liquid zinc. The steel and the liquid zinc bond together because of the high temperature. The steel and the zinc become one.

Zinc plating, on the other hand, is immersed in a cold chemical solution of zinc and uses an electrical current to apply a layer of zinc. The thickness of the coating is measured in microns or micrometre’s (μm). Zinc plating requires a minimum thickness of 5μm (.005mm) and a maximum of 25μm (.025mm). It would become too technical and expensive to coat the steel any thicker than this.

Hot dip galvanising requires a minimum thickness of 45μm (.045mm) and goes beyond 100μm (.1mm)

What Does This Mean For You (And Your Fence)?

A product that is hot dip galvanised will have a thicker coating, meaning it will last far longer. Hot dip galvanised coatings give superior protection against corrosion.

The images below show that zinc plated gate hardware will rust over time. This puts more strain on your hinges, stops your gate from swinging smoothly, and looks unsightly.

Difference between dowel bars and tie bars

Dowel bars

Dowel bars are placed at the transverse joints of concrete pavement and they take part in partial wheel load transfer from one slab to its adjacent slab. The dowel bars also allow axial thermal expansion and contraction of the concrete slab along the axis of the dowel.

Dowel bars are Mild Steel bars 30–38 mm diameter and 450 or 500 mm length. They are spaced at 300 mm centre to centre.


Tie bars

Tie bars are deformed rebars or connectors used for holding faces of rigid slabs in contact to maintain aggregate interlock. Tie bars are not load transferring device. For instance, tie bars are used in longitudinal joints in concrete pavement.

Tie Bars are TOR Steel bars 12 or 16 mm in Diameter (12 is common, 16 is not) of around 640 mm length. Their spacing is variable since it depends upon thickness of concrete surface and width of slab, though typically it varies between 550–640 mm.


Difference between dowel bars and tie bars

Screenshot (37).png

20 phrases for closing an email

A common problem

We often hear how writing emails in English can cost just too much time. One solution that works for many people is to begin building a “toolbox” of useful phrases. A toolbox is a simple idea – you just start keeping a list of common and useful expressions – perhaps on your desktop or in a notebook next to your keyboard? There’s nothing wrong with reusing some standard phrases if it helps save you time and communicate clearly. You probably already have 2 or 3 sentences you reuse again and again. But sometimes the tone just isn’t right, is it? To help you find the right words when you need them here are 20 great expressions for closing an email. As you read through them ask yourself two simple questions:

1. When would I use this?

2. When will I use this?

Expressions for thanking

  1. Thank you for your help. / time / assistance / support
  2. I really appreciate the help. / time / assistance / support you’ve given me.
  3. Thank you once more for your help in this matter.

Expressions with a future focus

  1. I look forward to hearing from you soon / meeting you next Tuesday.
  2. I look forward to seeing you soon.
  3. I’m looking forward to your reply.
  4. We hope that we may continue to rely on your valued custom.
  5. We look forward to a successful working relationship in the future.
  6. Please advise as necessary.
  7. I would appreciate your immediate attention to this matter.

Expressions for showing them you want to help

  1. If I can be of assistance, please do not hesitate to contact me.
  2. If you require any further information, feel free to contact me.
  3. If you require any further information, let me know.
  4. Please feel free to contact me if you need any further information.
  5. Please let me know if you have any questions.
  6. I hope the above is useful to you.
  7. Should you need any further information, please do not hesitate to contact me.
  8. Please contact me if there are any problems.
  9. Let me know if you need anything else
  10. Drop me a line if I can do anything else for you.

Don’t hesitate to comment below if you have any questions or additional phrases you’ve used that work.

Construction Drawings

Construction Drawings

Detail Design

On large or complex projects the Detail Design stage provides a vital opportunity to further refine the design language set out in the concept or planning stages. This informs Found and the design team the best approach for the construction methodology and approach to services. At Found we are always looking to explore new construction techniques and the innovative use of materials that make a project unique, the Detail Design stage allows valuable time to research and examine this.

During the Detail Design stage the Concept is further developed and the design work of the core design team is progressed until the general approach to a coordinated layout, design and construction method has been completed. This process may require a number of iterations of the design and a series of workshop meetings. Once this process is completed approval of the outline proposals will be required by the client prior to the design team commencing with the Tender Drawings and Specifications. This stage is equivalent to RIBA Stage 3.

Depending on the complexity of the planning requirements of a project the Detail Design stage may need to be carried out in advance so that the technical information produced can be included in the planning submission.

The work undertaken at this stage will vary depending on the size and nature of a project but in most instances the following drawings will be fixed by the end of this stage:

  • Builders Works, Services, Reflected Ceiling and Finishes Plans
  • General Arrangement Plans, Sections and Elevations

Tender Drawings

Tender Drawings form an incredibly important stage in the process of bringing a project to fruition and can define either its success or failure. To ensure that its always a success our approach at Found is to hold a series of design review meetings and showroom visits with our clients taking them through all aspects of the design, layout, materials and fixtures specification for the project and including all the decisions that are made in our drawings, schedules and specifications. In providing concise information at the tender stage we ensure that there is cost certainty for our clients projects minimising the amount of contingency required at the construction stage.

During the Tender Drawing stage the Detail Design drawings are further developed to provide technical definition to the project. Any construction issues and specialist subcontractor packages will be developed and concluded, this process will require a series of design team meetings. The drawings will also incorporate all design issues and amendments raised by the client at the approval presentation at the end of Detailed Design. By the end of this stage a detailed set of information will have been completed that will enable a tender or tenders to be obtained. This stage is equivalent to RIBA Stage 4.

The work undertaken at this stage will vary depending on the size and nature of a project but in most instances the final set of tender information will consist of:

  • Builders Works, Services, Reflected Ceiling and Finishes Plans
  • General Arrangement Plans, Sections and Elevations
  • Individual Room Drawings
  • Detail Drawings
  • Schedules and Specification

Construction Drawings

The Construction Drawing stage commences once a tender or tenders have been returned, analysed and the contract awarded. The stage offers the opportunity to amend the Working Drawings to reflect any value engineering that has been undertaken during the tender process or incorporate alternative suppliers or subcontractors that may have been put forward by the successful tenderer. At the end of this stage a full set of Construction Issue drawings, schedules and specifications will be issued to the appointed contractor so that work can commence onsite.

The work undertaken at this stage will vary depending on the size and nature of a project, the output of information will be similar to that produced at the Tender Drawing stage:

  • Builders Works, Services, Reflected Ceiling and Finishes Plans
  • General Arrangement Plans, Sections and Elevations
  • Individual Room Drawings
  • Detail Drawings
  • Schedules and Specification

Design Development

Similar to the Detailed Design or Tender Drawings produced for UK based projects the drawings produced at this stage will incorporate all design issues and amendments raised by the Client at the concept presentation. The drawings and specifications produced in the design development stage will reflect all, finishes and specifications to all elements in sufficient detail to allow the Clients local architect to commence with the development of Construction Documents which will resolve remaining technical issues and local, building code, CDM and planning requirements.

The work undertaken at this stage will vary depending on the size and nature of a project, the typical output of information would include:

  • Shell/Core drawings inclusive of plans, exterior elevations, building and wall sections and enlarged details.
  • Floor Plan locating new walls with dimensions and noting other important architectural elements or features.
  • Reflected Ceiling Plan which would incorporate the proposed lighting design by the Lighting Designer and also the proposed MEP elements designed by the MEP Engineer.
  • All interior elevations of affected space with critical dimensions and material notations.
  • Critical ceiling details related to form and shape.
  • Critical flooring details which would enhance the understanding of pattern layout or alignments.
  • Critical architectural details that are important to communicate to Client’s Local Architect.
  • Assist in providing additional information and attending meetings to allow for budget pricing.

Construction Documents

Once the project has reached this stage the Client’s Local Architect will be responsible for taking the project forward. Found will assist the Clients Local Architect with Construction Documents ready for the project to be tendered to local contractors. Founds responsibilities at this stage will be:

  • Attend project co-ordination meetings as required.
  • Review and comment on all Construction Documents supplied by Clients Local Architect to confirm design compliance.
  • Produce additional details to clarify design intent.
  • Provide additional clarification if required.

As-Built Drawings

On projects its common for changes to be made during construction because of circumstances that emerge on site or requested changes to the design. As a result as-built drawings are prepared towards the end of the onsite period to reflect what has actually been built.

These drawings will be issued to the contractor at the end of the project to be included within the operations and maintenance manual and the health and safety file. They will also be issued to the client for them to keep on file.

Eight-stage guide for Structural Engineers to implementing BIM on a project

It’s been years since the UK government announced its BIM mandate, large parts of the industry are still getting to grips with what this really means to their business. Trimble guides readers through the key stages, documents, terminology and, above all, processes that are ‘Level 2 BIM’.

The BSI defines Building Information Modelling (BIM) Level 2 maturity as ‘a series of domain and collaborative federated models. The models, consisting of both 3D geometrical and non-graphical data, are prepared by different parties during the project life-cycle within the context of a common data environment’1.

To start on this journey, it requires a plan. In the UK, this is called a digital plan of work (DPoW); the Royal Institute of British Architects (RIBA) DPoW2, published in 2013, is probably best known within the industry, but other plans of work exist for specific organisations within the construction industry, such as Network Rail’s Governance for Railway Investment Projects (GRIP) stages. The RIBA DPoW divides a project into eight stages to cover the whole lifecycle of a built asset:

0.    Strategic definition
1.    Preparation and brief
2.    Concept design
3.    Developed design
4.    Technical design
5.    Construction
6.    Handover and closeout
7.    In use


It is this digital plan (Figure 1) that we will use to guide you through delivering BIM, as a structural engineer, on a project.


0. Strategic definition
Strategic definition is a new stage that wasn’t in the previous RIBA plan and has been created to ensure that the actual need for a new or amended asset is discussed with a customer. In some cases, it may be decided that no work is needed and a project stops here. This stage is all about identifying the business case for the project and it generally won’t involve a structural engineer, or even much of the collaborative behaviours required to deliver BIM.

1.  Preparation and brief
With an agreed business case in place, the project then moves to this stage, where the foundations for a good BIM project are created. As well as preparing for the physical delivery of the asset, it is at this point that the BIM strategy for a scheme must be determined in order to deliver the greatest benefits to the team.

As a structural engineer, it is at this point that you will probably be appointed to begin your services. As such, this is the time to check whether a project purporting to be a ‘BIM job’ is set up correctly to deliver in this
way. Some of the questions you should ask yourself include:

  • Is there a set of employer’s information requirements (EIRs) (See “Definition of key BIM terms” tab below)?
  • Has any sort of BIM execution plan (BEP) been published?
  • Have task information delivery plans (TIDP) been requested or are any available?
  • Is the BIM protocol included within the contractual documents?
  • Has an information manager (See “What is an Information Manager” tab below) been appointed on the contract?

While there are many other indications of the existence of BIM on a project, these documents, and the processes that project teams need to agree upon, are the key indications that a project is serious about delivering BIM.

2. Concept design
At this stage, the design is still probably quite fluid and so starting to create a detailed 3D model risks being an abortive and wasteful process. Instead, massing models from the architect are likely to be shared around the team in order to test conceptual assumptions. The choice of material for the structural solution may not be fixed either, so simple calculations may be all that are required. What will be more important is ensuring that the information is being prepared correctly and shared in accordance with your own TIDP and the overall project master information delivery plan (MIDP).

However, by the end of this stage of the project, the agreed structural solution should have been determined.

3. Developed design
By this point in the project, real BIM workflows should be taking place and models being created and shared in accordance with the guidance in BS 1192:20073. Domain- specific (i.e. individual discipline) models, such as ones created by a structural engineer, are developed and shared to the common data environment (CDE). These discipline- specific models are then assembled together to create a ‘federated’ model – a single, complete model of the building that allows the collaborative workflows, which BIM is advocating, to happen.

This is also where the suitability codes within BS 1192 become even more important to ensure that the rest of the team understand for what purpose a model or data file has been issued (See “What are suitability codes” tab below). Suitability codes are covered in BS 1192, Table 5 and should be used whenever documents are issued to other parties on the project.

It is at this stage that 3D modelling software can be used to create both geometrically accurate and code-compliant designs, which can be exported as models and shared around the rest of the design team.

4. Technical design
This is the stage where engineering information and the scheme design generally move across to the specialist structural frame fabricator. In a traditional 2D design process, this would normally be done by issuing a set of drawings and accompanying calculations, which would give the fabricator most, but not all, of the information.

However, in a correctly managed BIM workflow, the full design can be shared, via the model, and so the digital processes ensure that the information can be relied upon. This is because it has been coordinated with the rest of the design team and is therefore far more accurate. This thoroughness, the improved coordination and data transparency result in better designs at this point and help to reduce risk, thereby improving profit for all organisations on the project.

Typically, a design team’s model would be passed to the fabricator to work up and complete the design to a fabrication level of detail without the need to build the structural model from scratch; a less wasteful and much more accurate process for both parties.

5. Construction
For an engineer, the construction stage of a project should be the point in time where they can sit back, relax and watch the design take shape on site. However, in the past this has not been the case, with numerous queries and clarifications coming from the site team over the detailing of the project.

With a well-executed BIM project, this should not be the case. The time spent early in the design process creating, checking and coordinating models will ensure that few, if any, requests for information (RFIs) come from the site team. With well-managed BIM processes, coordination and a data-rich model ensure that the construction stage on site goes smoothly, without the need for the structural engineer to revisit their documentation. Therefore, by doing BIM, the risk of overspending on any remaining design fees during this stage is all but mitigated. Remember, good modelling = better fees!

6. Handover and closeout
When the asset has been completed, the handover of agreed construction information takes place, to allow the customer to manage their asset. This is effectively the digital version of issuing operation and maintenance manuals; the difference being that the customer and their team have agreed what was needed from the start, so there should be no surprises. The responsibilities for issuing data are clearly defined through the EIRs and the project BEP.

7. In use
Unless monitoring the structure of an asset is required, it is unlikely that a structural engineer will be required to deliver any services during this stage of a project. By their very nature, structural frames should be low or zero-maintenance items. Maintenance regimes such as painting of exposed steelwork will be covered in Stage 6 and refurbishment of the asset would trigger a whole new cycle of a digital plan.

As this stage-by-stage guide shows, a BIM process adds a much greater level of rigour to projects, but one that allows teams to collaborate far more effectively to the benefit of all concerned. Designs are more accurate, appropriate and less wasteful, with re-work and errors all but eliminated. This means that the overall risk of the project is reduced and the chances of increased profit are greatly increased. Even when the rest of the team may not be doing BIM, the internal benefits to an engineering practice of sharing data and coordinating their own processes will still reap benefits.