It provides a comprehensive review of structural analysis and design methods related to vertical and lateral forces. All exam topics are covered, and exam-adopted codes and standards are frequently referenced. You will learn how to apply concepts by reviewing the example problems, and you will strengthen your problem-solving skills by working the 50 end-of-chapter practice problems. However, if the tension chord is tied at 1.
If the compression chord bracing is reduced to 1. The maximum allowable shear is about 12 kN. Unit beams Unit beams are normally about mm deep, are about 2Z. Loads should only be applied at the node points. May be used to span between scaffolding towers or as a framework for temporary buildings. As with ladder beams, bracing of both the top and bottom chords is required to prevent buckling, but diagonal plan bracing should be provided to the compression flange.
Units can be joined together with M24 bolts to make longer length beams. Standard lengths are 1. However, if the tension chord is tied at 3. If the compression bracing is reduced to 1.
The maximum allowable shear is about 14 kN. The following three iron ore products contain differing amounts of carbon: cast iron, wrought iron and steel. Cast iron involves the heat treatment of iron castings and was developed as part of the industrial revolution between and It has a high carbon content and is therefore quite brittle which means that it has a much greater strength in compression than in tension.
Wrought iron has relatively uniform properties and, between the s and , wrought iron took over from cast iron for structural use, until it was in turn superseded by mild steel. The steel can be formed into structural sections by casting, hot rolling or cold rolling.
Mild steel which is now mostly used for structural work was first introduced in the mid-nineteenth century. Types of steel products Cast steel Castings are generally used for complex or non-standard structural components. The casting shape and moulding process must be carefully controlled to limit residual stresses. Sand casting is a very common method, but the lost wax method is generally used where a very fine surface finish is required. Cold rolled Cold rolling is commonly used for lightweight sections, such as purlins and wind posts, etc.
Work hardening and residual stresses caused by the cold working cause an increase in the yield strength but this is at the expense of ductility and toughness. Cold rolled steel cannot be designed using the same method as hot rolled steel and design methods are given in BS Part 5.
The total amount of rolling work and the finishing temperatures are controlled to keep the steel grain size fine — which gives a good combination of strength and toughness. This pocket book deals only with hot rolled steel. Structural Steel Summary of hot rolled steel material properties Density It is therefore not realistic to provide a definitive list of the radii to which every section can be curved due to the wide number of end uses, but a selection of examples is possible.
Normal bending tolerances are about 8 mm on the radius. In cold rolling the steel is deformed in the yield stress range and therefore becomes work hardened and displays different mechanical properties notably a loss of ductility. However, if the section is designed to be working in the elastic range there is generally no significant difference to its performance. Source: Corus Construction Short stocky elements have low values of slenderness and are likely to fail by crushing, while elements with high slenderness values will fail by elastic reversible buckling.
Slender columns will buckle when the axial compression reaches the critical load. Slender beams will buckle when the compressive stress causes the compression flange to buckle and twist sideways. This is called Lateral Torsional Buckling and it can be avoided and the load capacity of the beam increased by restraining the compression flange at intervals or over its full length.
Full lateral restraint can be assumed if the construction fixed to the compression flange is capable of resisting a force of not less than 2. Structural Steel Effective length of cantilevers Conditions of restraint Effective length Support Cantilever tip Normal Destabilizing loading loading Continuous with lateral restraint to top flange Free 3.
Effective length of braced columns — restraint provided by cross bracing or shear wall Conditions of restraint at the ends of the columns Effective length Effectively held in position at both ends Effectively restrained in direction at both ends 0. The corrosion rate is affected by the atmospheric pollution and the length of time the steelwork remains wet. Sulphates typically from industrial pollution and chlorides typically in marine environments — coastal is considered to be a 2 km strip around the coast in the UK can accelerate the corrosion rate.
Both anodic and cathodic areas can be present on a steel surface. The following factors should be considered in relation to the durability of a structure: the environment, degree of exposure, shape of the members, structural detailing, protective measures and whether inspection and maintenance are possible.
Bi-metallic corrosion should also be considered in damp conditions. Unheated buildings where condensation may Mostly rural areas occur, e. Coastal some air pollution, e. BS EN ISO Part 3 gives advice on steelwork detailing to avoid crevices where moisture and dirt can be caught and accelerate corrosion. Some acidic timbers should be isolated from steelwork. Get advice for each project: Corus can give advice on all steelwork coatings. Structural Steel Methods of corrosion protection A corrosion protection system should consist of good surface preparation and application of a suitable coating with the required durability and minimum cost.
As it cools, its surface reacts with the air to form a blue-grey coating called mill scale, which is unstable, will allow rusting of the steel and will cause problems with the adhesion of protective coatings.
The steel must be degreased to ensure that any con- taminants which might affect the coatings are removed. The mill scale can then be removed by abrasive blast cleaning. Sa 3 is often used for surface preparation for metal spray coatings. Metallic and non-metallic particles can be used to blast clean the steel surface. Chilled angular metallic grit usually grade G24 provides a rougher surface than round metallic shot, so that the coatings have better adhesion to the steel surface.
Coatings must be applied very quickly after the surface preparation to avoid rust reform- ing and the requirement for reblasting. Paint coatings for structural steel Paint provides a barrier coating to prevent corrosion and is made up of pigment for colour and protection , binder for formation of the coating film and solvent to allow application of the paint before it evaporates and the paint hardens. When first applied, the paint forms a wet film thickness which can be measured and the dry film thickness DFT — which is normally the specified element can be predicted when the percentage volume of solids in the paint is known.
Primers are normally classified on their protective pigment e. Intermediate which build the coating thickness and finish coats are usually classified on their binders e. Zinc rich primers generally perform best. Application of paint can be by brush, roller, air spray and airless spray — the latter is the most common in the UK.
Application can be done on site or in the shop and where the steel is to be exposed, the method of application should be chosen for practicality and the surface finish. Shop applied coatings tend to need touching up on site if they are damaged in transit. The zinc reacts with the surface of the steel, forming alloys and as the steel is lifted out a layer of pure zinc is deposited on outer surface of the alloys.
The zinc coating is chemically bonded to the steel and is sacrificial. The heat can cause distortions in fabricated, asymmetric or welded elements. Paint coatings can be applied on top of the galvanizing for aesthetic or durability reasons and an etch primer is normally required to ensure that the paint properly adheres to the galvanizing. Thermal spray Degreased and blast cleaned generally Sa 3 steel is sprayed with molten particles of aluminium or zinc.
The coating is particulate and the pores normally need to be sealed with an organic sealant in order to prevent rust staining. Metal sprayed coatings are mechanically bonded to the steel and work partly by anodic protection and partly by barrier protection. There are no limits on the size of elements which can be coated and there are no distortion problems. Paint coatings can be applied for aesthetic or durability reasons.
Professional Ethics. Engineering Economics. Engineering Materials. Strength of materials. Building Construction. Civil Programming. Reinforced Concrete. Differential Equations. Soil Mechanics I.
Past Papers. Civil Engineering Ebooks. Recommended Books. Free Downloads. MS Project Video Tutorials. Clough, S. Livesley, H. Martin, M. Turner, E. Wilson, and O. Structural engineering is the science and art of planning, designing, and constructing safe and economical structures that will serve their intended purposes.
Structural analysis is an integral part of any structural engineering project, its function being the prediction of the performance of the proposed structure. As this diagram indicates, the process is an iterative one, and it generally consists of the following steps:. Planning Phase — The planning phase usually involves the establishment of the functional requirements of the proposed structure, the general layout and dimensions of the structure, consideration of the possible types of structures e.
This phase may also involve consideration of non-structural factors, such as aesthetics, environmental impact of the structure, and so on. The outcome of this phase is usually a structural system that meets the functional requirements and is expected to be the most economical. This phase is perhaps the most crucial one of the entire project and requires experience and knowledge of construction practices in addition to a thorough understanding of the behaviour of structures.
Preliminary Structural Design — In the preliminary structural design phase, the sizes of the various members of the structural system selected in the planning phase are estimated based on approximate analysis, past experience, and code requirements.
The member sizes thus selected are used in the next phase to estimate the weight of the structure. Estimation of Loads — Estimation of loads involves determination of all the loads that can be expected to act on the structure. Structural Analysis — In structural analysis, the values of the loads are used to carry out an analysis of the structure in order to determine the stresses or stress resultants in the members and the deflections at various points of the structure.
Safety and Serviceability — Checks The results of the analysis are used to determine whether or not the structure satisfies the safety and serviceability requirements of the design codes. If these requirements are satisfied, then the design drawings and the construction specifications are prepared, and the construction phase begins. Revised Structural — Design If the code requirements are not satisfied, then the member sizes are revised, and phases 3 through 5 are repeated until all the safety and serviceability requirements are satisfied.
Commonly used structures can be classified into five basic categories, depending on the type of primary stresses that may develop in their members under major design loads. The members of tension structures are subjected to pure tension under the action of external loads.
Because the tensile stress is distributed uniformly over the cross-sectional areas of members, the material of such a structure is utilized in the most efficient manner. Tension structures composed of flexible steel cables are frequently employed to support bridges and long-span roofs. Because of their flexibility, cables have negligible bending stiffness and can develop only tension. Thus, under external loads, a cable adopts a shape that enables it to support the load by tensile forces alone.
0コメント