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In his editorial of 18th October 2011, Managing Editor Lee Baldwin heralded the introduction of a series of 'Technical Guidance Notes'. Sarah Fray - Director: Engineering and Technical Services provides an introduction to the series.
All Level 1 Technical Guidance Notes (originally published in The Structural Engineer magazine).
Although retaining walls have been the subject of two earlier Technical Guidance Notes; No. 8 (Level 1): Derivation of loading to retaining structures and No. 33 (Level 1): Retaining wall construction, their design has not been covered. This guidance note focuses specifically on the design of reinforced concrete gravity retaining walls.
There are three different forms of this type of wall, all of which are designed to resist overturning and sliding failure. The primary difference between them is their height. The taller the retaining wall, the more likely that counterforts and beams spanning between them will be necessary. This note describes how all of these forms of retaining wall can be designed.
(This article was updated in October 2016 to reflect errata issued since its original publication.)
The importance of accurate information and interpretation of soil conditions on a site cannot be understated. The chosen form of any sub-structure is entirely dependent upon what the site investigations have revealed. It is typically up to the structural engineer, with the aid of geotechnical engineers and specialists, to determine the extent of this investigation and interpret its results. This Technical Guidance Note explains the various methods of site investigation and can be considered a partner to the previously published note on 'soil bearing capacity'.
This Technical Guidance Note concerns the derivation of dead loads. This is a core guidance note and as such, subsequent notes will make reference to this one. It is therefore important to understand the contents of this note before attempting to digest any of the others.
Dead load is defined as the weight of static materials contained with a structure. This includes the self weight of the structure as well as the materials it is supporting that are fixed to it. Within Eurocode 1 it is defined as a 'Permanent Action'.
When designing foundations for a structure there is a need to determine the bearing capacity of the soil. This applies to all forms of foundation, from a simple pad footing to a pile cap. The bearing stress capacity of the soil is the key variable that has a direct impact on the form and size of foundations. This Technical Guidance Note explains the principles of how bearing capacity of soils are determined and how it impacts on the design of foundations.
One of the most common structural elements is the timber floor joist. This is normally found in residential properties, but can also be seen in medium sized commercial developments. This Technical Guidance Note will explain the principles behind the design of timber floor joists and provide a worked example. All of the advice given will be in accordance with BS EN 1995-1-1 Eurocode 5: Design of Timber Structures – Part 1-1: General – Common rules and rules for buildings.
Once the concept and scheme for a structure has been settled upon, the initial sizing of the elements that it is made up of commences. This Technical Guidance Note provides a set of hints as to how to initially size elements, prior to carrying out the detailed design. This process allows the engineer to gain an appreciation of the form of the structure and the changes that may be required if element sizes prove to be too onerous following this size estimation process.
Access more Technical Guidance Notes through our series homepage .
Elements within a steel frame structure are at risk of buckling under load. If measures are not taken when designing steel elements that recognise this risk, then the likelihood of its failure is significantly increased. This Technical Guidance Note explains how steel elements are restrained against buckling and what the structural engineer should consider when analysing steel structures with respect to buckling resistance.
While the advancement of computer based analysis continues to grow exponentially within the field of structural engineering, the tools that are used to analyse structures by hand are no less relevant. Many would argue that such tools are even more vital today than they have ever been if we are to fully understand the output of analysis applications. With this in mind, this Technical Guidance Note describes one of the most powerful analysis tools available: moment distribution.
Moment distribution is a method by which statically indeterminate structures are analysed elastically. It’s based on the relative stiffness of elements that make up a structure and shifts bending moments from one section of the structure to another until they become balanced. Once this balance has been achieved, the forces and bending moments within the structure are modelled.
A description of the various forms of retaining walls currently in use. This note is primarily concerned with structures that retain soil.
When developing a scheme for a structure, the choice of floor slab construction is critical to the columns, foundations, walls and overall stability. As such, the floor slab’s form should be selected with care and consideration.
This Technical Guidance Note provides information about a number of common floor construction forms that are currently available. It focuses on concrete based solutions: some acting compositely with steel elements, such as reinforcement and/or steel members. Descriptions of each flooring system together with their key features (which cover topics such as buildability, aesthetics and compatibility of other elements e.g. building services) are included. Please be aware that floor slab technology is continually evolving and that new floor slab solutions continue to become available as a result.
This Technical Guidance Note describes the basic knowledge required to read drawings produced by structural engineers.
An introduction to ground bearing floor slabs, touching on the slabs' reinforcement by considering both historical use of mesh as well as current plastic and steel fibre reinfocement methods.
The use of masonry dates back to antiquity with evidence of the use of some form of stone masonry originating over 10,000 years ago. This guide introduces the material, focusing on the two most common forms; brick and concrete block.
This Technical Guidance Note describes the causes of cracking in concrete.
This Technical Guidance Note defines the concept of fatigue and how its effects can be countered.
This Technical Guidance Note describes how prestressed precast concrete planks are constructed, specified and installed.
This guidance note describes the different types of pile presently in use, the design concepts that are employed when determining their size and depth, how they are constructed and the various tests that can be carried out to assess a pile's integrity.
This Technical Guidance Note describes the concept of biaxial bending of columns, as well as the effect direct bending has on column design. The guidance given here can be applied to columns made from any material, be it steel, concrete, timber or even glass.
The twisting of elements within structures due to eccentric loading is something that is best avoided as far as is possible. Such actions develop torsion forces in elements against which they were not designed to withstand. This Technical Guidance Note concerns this buildability and detailing issue that structural engineers must become familiar with in order to avoid otherwise unforeseen problems that can lead to significant remedial works on site and in some cases failures.
When analysing structures it is important to adopt a methodical approach wherever possible. By breaking down the structure into manageable portions, the complexity of the analysis is reduced and thus becomes easier to control and review. By adopting such an approach, a seemingly insurmountable task becomes a much more approachable one. This Technical Guidance Note is a good practice guide for analysing and designing structures. It explains how structures are given form, modelled, analysed and designed. Mention is made of the need to rationalise the analysis process, but not at the expense of an economic design.
This Technical Guidance Note describes how drawings for structural steelwork are developed and read. They have their own unique set of rules and nomenclature and it is important for engineers to understand all of these rules in order to communicate and interpret the design of steelwork structures.
This guide is split into two sections; the ﬁrst contains the information a designer of the steel elements provides, whilst the second contains the information a fabricator creates in order to manufacture and construct the steel structure. While one feeds into the other, the level of detail each set of information provides is very different, due primarily to the end result. One is informing the manufacture of the steelwork, while the other focuses on its installation.
This Technical Guidance Note explains the way in which reinforced concrete drawings should be read. In many cases reinforced concrete drawings are more diagrammatic than their general arrangement counterparts and carry with them their own unique set of rules and nomenclature. Note that the guidance provided here is based on European codes of practice; for all other regions the reader is directed to local guidelines on reinforced concrete detailing methods. This technical guidance note does not cover the rules governing the detailing reinforced concrete. That is a far more complex subject which is dealt with in The Institution of Structural Engineers’ publication Standard Method of Detailing Structural Concrete (3rd edition).
This Technical Guidance Note is an introduction to the assessment of floor vibrations. Since the adventof lighter structures that have longer spanning elements within them, the built in dampening effectbuildings have had historically has become less pronounced. Despite this, floor vibration canbe an overlooked criterion during the design process. This can lead to expensive remedial works being carried out on structures after they have been built, as occupants complain of discomfort due to excessive movements and vibrations.
This guide explains the various methods that can be adopted to ensure that lateral stability to structures is achieved. This note also highlights the need for robustness in structures as it is regarded as an aspect of structural design that can have an impact on strategies adopted for lateral stability. All of the guides in this series have an icon based navigation system, designed to aid the reader.
This Technical Guidance Note acts as an introduction to the core design concepts that are found within the current codes of practice used within the UK. It also explains the relationship between each of the other guidance notes and how the reader is to navigate and use them. All of the subsequent notes make reference, be they direct or implied to this core guide; it is therefore imperative that anyone seeking to use these guides must be fully conversant with what is contained within this note.
This Technical Guidance Note covers the inspection of structural elements that are typically present within buildings during their construction and/or alteration phases.
This Technical Guidance Note concerns the design of pile-caps for small groups of piles e.g. 2-4 piles. It relies on the strut and tie method to determine the amount of reinforcement required in the pile-cap; which is dependent upon the depth of the cap, the magnitude of the axial load being placed upon it, the cap’s concrete strength and the pile size and spacing.
The purpose of a pad foundation is to spread a concentrated force into soil. They are one of the most simple and cost effective types of footings for structures. Provided the founding soil is of sufficient strength and is not too deep to reach, pad foundations are the preferred solution for foundations due to the straight forward nature of their design and construction.
This Technical Guidance Note covers the design of concrete pad foundations, both mass and reinforced concrete forms. It will not, however, discuss how the bearing capacity of the soil is determined, as that is explained in Technical Guidance Note 19 (Level 1) Soil bearing capacity. It is suggested that you read that text in conjunction with this, in order to gain a more comprehensive understanding of the topic.
Until relatively recently, masonry was the major load bearing component in a building structure. With the advent of steel and concrete frame technologies, masonry has become a part of a building’s cladding envelope and as such is more prone to being exposed to lateral loads than vertical ones.
This Technical Guidance Note concerns the design of masonry walls that are subject to lateral loads i.e. they are being used as a cladding element. It will discuss the way in which the material is assessed against how it is being restrained and its geometry. All of these factors have an impact on the design of masonry walls as well as the mortar within them and the exposure conditions. This is discussed in Technical Guidance Note 27 (Level 1) and should be read in conjunction with this guide.
This Technical Guidance Note concerns the assessment of loads that are applied to retaining structures, typically generated from soil. These forces primarily come into play during the design of retaining wall structures, but they can also be found in water retaining structures and storage vessels.All of the guides in this series have an icon based navigation system, designed to aid the reader.
This Technical Guidance Note concerns lateral loads that are applied to barriers and wheel axle loads from vehicles. Barrier loading is dealt with slightly differently to other forms of imposed loading. The nature of the loading can vary from people leaning against barriers to vehicles colliding with them at speed. Axle loading from vehicles has to be treated somewhat differently to other forms of imposed loading. While it is possible to assume a blanket area load to represent them, it is the point load from each wheel that needs closer attention.
This Technical Guidance Note concerns the concept of notional loading, which the Eurocodes classifies as Equivalent Horizontal Forces. These are loads that exist due to inaccuracies and imperfections introduced into the structure during its construction. The following text explains how notional lateral loads are incorporated into the design process.
This Technical Guidance Note concerns the derivation of snow load onto structures. It is based on Eurocode 1: Actions on Structures Part 1-3; General Actions – Snow Loads. With this Eurocode being focused on an action that is sensitive to environmental effects, the UK annex to it plays a significant role, as it makes reference to projected snow falls that are unique to the British Isles. There are a large number of variations and conditions the designer must be aware of when determining snow loads onto structures. As such, the reader is referred to the code text more frequently than in other Technical Guidance Notes.
This Technical Guidance Note concerns the derivation of wind load onto structures. It is based on Eurocode 1: Actions on Structures Part 1-4; General Actions – Wind Actions. With this being focused on a load that is sensitive to the environment, the UK Annex to the Eurocode plays a significant part as it makes reference to wind speeds that are unique to the British Isles. There are a large amount of variations and conditions the designer must be aware of when determining wind loads on structures. It is for this reason that the reader is referred to the code text more often than in other notes in this series.
This technical guidance note is an introduction to glass as a structural material. It aims to describe glass in terms of its properties, how it reacts when subjected to various forces and the methods currently being explored and adopted by structural engineers when designing structural glass elements.
This Technical Guidance Note explains the basic principles of below ground drainage for both surface and foul water. Acting as an introduction, it describes the different types of drainage pipes that are available, how they are installed, how they interface with structure, their testing and maintenance.
A significant-sized opening in a masonry wall will always require a lintel to bridge over it. This note offers advice on the different types of lintel that are available, their detailing requirements and their design.
The subject of this guide is the design of columns in simple construction to BS EN 1993-1-1 – Eurocode 3: Design of Steel Structures – Part 1-1: General Rules for Buildings. It covers rolled steel ‘I’ and ‘H’ sections that are acting as columns within a braced steel frame structure.
Thin panels of masonry in large buildings, or cavity wall skins, require additional horizontal support to make them stable. The element that provides this support is a vertical prop known as a ‘windpost’. Its principal role is to provide lateral support against destabilising horizontal forces that typically originate from wind pressure – hence, the name.
Windposts are typically steel elements – either open sections, such as channels or angles, or closed sections, such as rolled hollow rectangular sections. This Technical Guidance Note provides guidance on the design and detailing of windposts relating to their incorporation into building structures.
This Technical Guidance Note is intended to act as an aide to those seeking to design an unreinforced masonry retaining wall. Following this guidance will prevent cracking and ensure that the wall performs as originally intended.
The note will not cover the design of reinforced masonry retaining walls and variants of that form. Such reinforcement typically strengthens the wall itself against induced bending stresses and the wall’s geometry will therefore be somewhat different to that of an unreinforced retaining wall.
The note will also not discuss the applied actions that a retaining wall will be subjected to, nor the construction of retaining walls. These subjects have previously been covered in the following Technical Guidance Notes: Level 1, No. 8: Derivation of loading to retaining structures and Level 1, No. 33: Retaining wall construction. It is assumed that the reader is familiar with the content of both these notes.
This Technical Guidance Note aims to clarify the term 'simple connection' by explaining its use when designing connections within steel frames. Additionally, guidance is offered on different types of simple connection and the design checks that need to be carried out.
Piled foundations are one of the first aspects of scheme design a structural engineer needs to consider during a project's development. It is at this crucial stage that, without any specialist input, the structural engineer must make recommendations based on the typically limited knowledge they have on the subject.
This Technical Guidance Note describes the method by which bored piles are designed using the current UK codes of practice, i.e. BS EN 1997 (Eurocode 7). It explains how to interpret soil conditions and design piles to match what has been discovered following a site investigation.
The note does not address the types of piling systems that are available, nor the technical issues concerning their installation; these questions are covered in Technical Guidance Note Level 1, No. 23 Introduction to piling.
The note explains how to design what is essentially a buried column of concrete to resist forces from the superstructure that are applied to it. It concerns the design of a single pile and not one that is part of a group. For information on how grouped piles differ in their design approach, the reader is directed to Cl. 6.3.3 of BS 8004:2015.
(This article was update on 9 March 2018 to correct an error in Table 6.)
The design of timber posts follows the same principles as the design of vertical structural elements formed from other materials. Extreme fibre stresses or buckling due to applied axial forces are the key components affecting a post’s ability to perform. The major difference is the anisotropic nature of timber, which, for vertical elements, has a significant impact on the assessment of their performance as a structural member.
The design of timber elements in the UK, according to current codes of practice, is based on limit state theory. This Technical Guidance Note adopts this approach to describe the design of timber posts. The note assumes that the reader is familiar with the use of coefficient factors prevalent within BS EN 1995-1-1 (Eurocode 5), as described in Technical Guidance Notes Level 1, No. 18 Design of timber floor joists and Level 2, No. 14 Design of unrestrained timber beams.
This Technical Guidance Note concentrates on the design of reinforced concrete columns to BS EN 1992-1-1 – Eurocode 2: Design of Concrete Structures – Part 1-1: General Rules for Buildings. It covers the design of columns of all cross section proﬁles, which are typically square, rectangular and circular.
The subject of this guidance note is the design of reinforced concrete beams to BS EN 1992-1-1 – Eurocode 2: Design of Concrete Structures – Part 1-1: General Rules for Buildings. It covers the design of multispan beams that have both ‘L’ and ‘T’ cross section profiles.
The subject of this guide is the design of one way spanning concrete slabs to BS EN 1992-1-1 – Eurocode 2: Design of Concrete Structures – Part 1-1: General Rules for Buildings. The design of such elements is very simple to carry out and thus acts as a good introduction to the concept of reinforced concrete.
This Technical Guidance Note describes the design and detailing of base plates – the primary means by which steel-framed structures transmit vertical loads into their foundations.
Imposed load is defined as the load that is applied to the structure that is not permanent and can be variable. In Eurocode phraseology, it is described as a 'quasi-permanent variable action'. Please be aware that this note does not cover lateral loads onto barriers, balustrades and axle loads from vehicles. These will be covered in a forthcoming note.
Recently, the technology behind post fix anchors has become increasingly complex. This guidance note has been developed in order to provide some clarity around the multitude of options that can be presented to a designer required to specify anchors.
This guidance note pays particular attention to partial factors with reference to BS EN 1990: Eurocode – Basis of structural design, to illustrate how extreme events are approached within a code of practice, and explains how the code interprets the application of loads/actions for the design of structures for such events.
This Technical Guidance Note addresses the design of timber elements that are unrestrained against lateral torsional buckling. It explains how such beams are analysed and designed. The impact of notching the supports of beams is also considered with respect to the shear capacity of the beam.
For clarity and brevity, this note only covers solid and glued laminated (glulam) timber elements; compound and composite beams, such as flitch beams, are not considered. The connections within timber frame assemblies will be addressed in a future note.
Readers should also be aware that this note forms part of a trio of Technical Guidance Notes leading to the design of bespoke timber trusses – assemblies made from unrestrained timber beams and posts. Notes on the design of timber posts and bespoke timber trusses will follow later in the series.
Since the invention of medium-storey framed structures in the late 1800s, there has been a need to clad them with a reasonably robust material that acts as an efficient barrier to the external environment. Masonry delivers the performance required of a cladding system on multiple fronts. It has therefore developed from a load-bearing element within structures to become a component of an envelope to larger framed buildings.
This Technical Guidance Note introduces structural engineers to the interfaces between a primary structure that is principally formed from steelwork and a masonry cladding system.
Portal frames are a simple and very common type of framed (or skeleton) structure. Steel portal frames, in particular, are a cost-effective structural system to support building envelopes (such as warehouses and shopping complexes) requiring large column-free spaces. In general, the loads and consequent deformations for these frames are in the plane of the structure, and hence these are a 2D (or plane) frame structure. Due to the practical requirement of having a clear space between the supports of a portal frame, providing in-plane bracing is generally not feasible. Consequently, these frames undergo larger deflections and are prone to sway laterally, even under the vertical loads. The concept of sway frames is addressed in more detail in Technical Guidance Note No. 10 (Level 1) Principles of lateral stability. Thus, in spite of the inherent simplicity of portal frames, many aspects of their analysis, design and detailing require careful consideration.
Portal frames can be made from concrete, timber and even glass but the vast majority, in the UK certainly, are constructed from steel. This Technical Guidance Note gives an introduction to steel portal frames and their preliminary analysis. Steel portal frames usually have pinned bases and moment connections at the column/rafter interface and mid-span apex splice in the rafter. Although there are other forms of portal frame (described in Elastic Design of Single- Span Steel Portal Frame Buildings to Eurocode 3), for the sake of brevity and clarity this note will be dedicated to this particular form.
This Technical Guidance Note describes how steel fibre reinforced concrete ground bearing slabs are designed. This is a relatively recent innovation that continues to evolve. As such, this note aims to motivate the design and development of steel fibre reinforced ground bearing slabs, based on the most up-to-date information available at the time of writing.
This Technical Guidance Note explains how reinforced concrete walls are designed to withstand high in-plane bending forces, in accordance with Eurocode 2.
The subject of this guide is the design of non-composite steel beams to BS EN 1993-1-1 – Eurocode 3: Design of Steel Structures – Part 1-1: General Rules for Buildings. It covers both restrained and unrestrained rolled steel ‘I’ and ‘H’ beam sections.
This is the first in the series of Level 2 guides and as such,the reader is assumed to be familiar with the concepts explained in relevant Level 1 Technical Guidance Notes.
This Technical Guidance Note focuses on the visualisation of structures. It is essential for structural engineers to be able to express their ideas clearly through their designs. Visualising structures in the appropriate way enhances the design process - not least because drawing the complex elements of a structure while carrying out calculations, can help to identify possible construction issues/problems at an earlier stage than may otherwise be possible. This guide explains two techniques that are commonly used to draw in three dimensions and thus aid the structural engineer in visualising the structures they design.All of the guides in this series have an icon based navigation system, designed to aid the reader.