Introduction to Concept Design in the IStructE Exam
The Institution of Structural Engineers (IStructE) exam is a challenging test of your structural engineering knowledge, skills, and ability to develop concept designs, then appraise and design them. The exam is split up into the following sections:
Section 1a – Design appraisal - developing two viable, distinct, and sustainable solutions.
Section 1b – Professional communication to the client
Section 2e – Calculations of main structural members
Section 2d – Drawings of proposed solution
Section 2e – Method statement
This article provides tips, hints, and examples for section 1a which focuses on scheme development, looking at functional framing, stability, and scheme recommendation. This includes determining preliminary member sizes, describing load transfer, and recommending the scheme proposal. These insights will help you prepare effectively for the IStructE Part 1 exam. Whether you are taking the exam for the first time or seeking to improve your approach, these tips will enhance your readiness and performance.
Part 1a: Design appraisal
In the first part of the IStructE exam, you are tasked with demonstrating your ability to propose two distinct, viable, and sustainable solutions to a client brief. To develop your design appraisal you will start by writing your 'initial Thoughts' to assess the clients brief and come up with ideas for the 2 schemes. After this you will explain 2 proposed schemes with the 'Functional Framing and Stability', followed by an explanation of 'Load Transfer. Repeat this for both schemes. You will conclude with the 'Scheme Recommendation' to determine your final proposed scheme. This article provides you with guidance for 'Initial Thoughts', 'Functional Framing and Stability', 'Load Transfer', and 'Scheme Recommendation'.
Initial Thoughts
Review each question to decide which one you want to answer. Choose the question that best suits your abilities and experience, (i.e. the question that you feel like you can answer the best), exam day is not the day to be attempting something new! Now you have chosen your question, review the clients brief in further detail. There will be various key issues / hurdles / challenges that you need to overcome in your solutions. These include key issues like structural zones, column free zones, long span structures, unsuitable ground conditions etc. Review each one and consider different options, i.e. long span structure – option 1 portal frame, option 2 roof truss. Provide sketches for the structural zones and ground conditions to show that you understand the client brief. Complete this review and summary with each of the key issues and combine the options to make two viable, distinct, and sustainable schemes that you will discuss in the next section.
An example for the initial thoughts is shown below based on question 1 of the IStructE January 2015 exam.
Functional Framing and Stability
This section serves as an introduction to your schemes with a combination of sketches, annotation, and an explanation describing the overall framing system chosen for the structure and how the structures are to remain stable.
An example for the functional framing and stability is shown below based on question 1 of the IStructE January 2015 exam. Repeat this process for scheme 2.
Here are some hints and tips for explaining functional framing and stability.
🔶 Use guidance tables, span/depth ratios, and quick calcs if necessary to determine preliminary sizes for members.
🔶 For each scheme, provide indicative sketches followed by a brief description, use colour if it helps.
🔶 In the sketches, highlight / colour the use of bracing, shear walls, or moment frames to resist lateral loads and provide stability.
🔶 This page gives a good introduction to the reader / marker of your conceptual design and ideas, helping to demonstrate that you understand how it is framed together and will remain stable so ensure sketches and writing is clear enough to understand.
Load Transfer
A fundamental aspect of the exam involves explaining how loads are transferred through the proposed structural schemes. This includes both vertical load transfer and lateral load transfer in which you will write an explanation and provide sketches showing the path of the loads transferring through the structure down to the supporting foundations.
An example for the load transfer is shown below based on question 1 of the IStructE January 2015 exam. Repeat this process for scheme 2.
Here are some hints and tips for explaining the load transfer for your schemes.
🔺 For each scheme explain how vertical and lateral loads transfer through your structure, use text and sketches like shown in the example.
🔺 Describe the load path and how the structural members behave, e.g. slab acts as a diaphragm, the braced bay acts as a cantilever for the foundations, etc.
🔺 Provide sketches and add colour to indicate the loads, the 'vertical transfer load' example shows basic pencil sketch for the frame, with a red pen used for the applied loads, blue pen used for the behaviour of the members, and green pen to show the foundation reactions.
🔺 This section essentially shows the marker that you understand how a structure behaves with applied loads.
🔺 Ensure you include the essential information, and if you have spare time then you can add more detail.
Scheme Recommendation
After you have developed your 2 distinct, viable, and sustainable schemes, you then need to recommend one of these as the preferred scheme. This part is called the scheme recommendation / appraisal and includes critically appraising and assessing your two schemes based on various criteria then concluding with an explanation of why you have chosen the preferred scheme.
An example for the scheme recommendation is shown below based on question 1 of the IStructE January 2015 exam.
Here are some hints and tips for developing your scheme recommendation.
🔹 Decide which criteria you should use to assess the schemes. Typically this includes: aesthetics, buildability, economy, environment/sustainability, function, health & safety, and stability. Both schemes should satisfy each criteria aspect well enough to be considered viable, and a comparison should be made to evaluate the best scheme. Note that the IStructE consider environment/sustainability as an important factor to consider in all designs.
🔸 Aesthetics - which scheme is going to look the best? Think about what will be visible when it is built. Cable bracing is likely going to look better than big steel bracing. Timber beams may be considered to look nicer than steel beams. Bigger spans will likely be better aesthetically due to less columns.
🔸 Buildability - which scheme is going to be the most buildable? Think about construction programme, how easy it will be to build, how fast it will be to build etc. Think about the site constraints, is it a small site with only small areas for storage? Does any scheme have offsite fabrication to save time on site? Can it be built with minimal temporary works?
🔸 Economy - which scheme is going to be the most economic? Consider cost of materials and construction. A steel structure will likely be lighter than concrete resulting in smaller foundations.
🔸 Environment/Sustainable - which scheme is going to be the most environmental and sustainable? Consider carbon emissions of the construction and materials. This is very important to include as the exam requires you to demonstrate that you understand this aspect.
🔸 Function - which scheme is the most functional? For example, if the clients brief emphasizes open spaces, then the scheme with less internal columns will likely be better.
🔸 Health & Safety - which scheme is the most safe? Each scheme will have certain aspects that make it safer than the other. Think about what construction method is being used, such as offsite fabrication which could be considered safer with a more controlled environment in the factory.
🔸 Stability - which scheme is the most stable? Stability of the structure is a key aspect of determining distinct and viable schemes, it's very likely that both schemes will have different stability systems. Think about how stable the structure is in both the permanent and temporary case.
🔹 Assessment - compare the pros and cons of each scheme, add up the values and recommend the preferred scheme. You could in to more detail by factoring each criteria by its importance, but remember that this will take more time.
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