1- Concrete Structures
Concrete is the most commonly used man-made material on earth. It is an important construction material used extensively in buildings, bridges, roads and dams. Its uses range from structural applications, to paviours, kerbs, pipes and drains.
Concrete is a composite material, consisting mainly of Portland cement, water and aggregate (gravel, sand or rock). When these materials are mixed together, they form a workable paste which then gradually hardens over time.
For the different types, see Types of concrete.
A material similar to concrete was first developed by the Egyptians, consisting of lime and gypsum. Typically, lime, chalk or oyster shells continued being used as the cement forming agent until the early-1800s.
In 1824, Portland cement, a mixture of limestone and clay was burned and ground, and since then, this has remained the predominant cementing agent used in concrete production.
Benefits of concrete
There are numerous positive aspects of concrete:
It is a relatively cheap material and has a relatively long life with few maintenance requirements.
It is strong in compression.
Before it hardens it is a very pliable substance that can easily be shaped.
It is non-combustible.
Limitations of concrete
The limitations of concrete include:
Relatively low tensile strength when compared to other building materials.
Low strength-to-weight ratio.
It is susceptible to cracking.
2- Steel Structures
What is steel structure?
Steel structure is a metal structure which is made of structural steel* components connect with each other to carry loads and provide full rigidity. Because of the high strength grade of steel, this structure is reliable and requires less raw materials than other types of structure like concrete structure and timber structure.
In modern construction, steel structures is used for almost every type of structure including heavy industrial building, high-rise building, equipment support system, infrastructure, bridge, tower, airport terminal, heavy industrial plant, pipe rack, etc.
Depending on each project’s applicable specifications, the steel sections might have various shapes, sizes and gauges made by hot or cold rolling, others are made by welding together flat or bent plates. Common shapes include the I-beam, HSS, Channels, Angles and Plate.
Main structural types
- Frame structures: Beams and columns
- Grids structures: latticed structure or dome
- Prestressed structures
- Truss structures: Bar or truss members
- Arch structure
- Arch bridge
- Beam bridge
- Cable-stayed bridge
- Suspension bridge
- Truss bridge: truss members
Reasons to choose Steel Structures
1. Cost savings
Steel structure is the cost leader for most projects in materials and design. It is inexpensive to manufacture and erection, requires less maintenance than other traditional building methods.
Steel has a natural beauty that most architects can’t wait to take advantage of. Steel allows for long column-free spans and you can have a lot of natural light if you want it in any shape of structures.
3. Control and Management
Steel structures is fabricated at factory and rapidly erected at construction site by skilled personnel that makes safe construction process. Industry surveys consistently demonstrate that steel structures is the optimal solution in management.
It can withstand extreme forces or harsh weather conditions, such as strong winds, earthquakes, hurricanes and heavy snow. They are also unreceptive to rust and, unlike wood frames, they are not affected by termites, bugs, mildew, mold and fungi.
Structural analysis is the determination of the effects of loads on physical structures and their components. Structures subject to this type of analysis include all that must withstand loads, such as buildings, bridges, vehicles, furniture, attire, soil strata, prostheses and biological tissue. Structural analysis employs the fields of applied mechanics, materials science and applied mathematics to compute a structure’s deformations, internal forces, stresses, support reactions, accelerations, and stability. The results of the analysis are used to verify a structure’s fitness for use, often precluding physical tests. Structural analysis is thus a key part of the engineering design of structures.
Types of Structural Analysis
To perform an accurate analysis a structural engineer must determine information such as structural loads, geometry, support conditions, and material properties. The results of such an analysis typically include support reactions, stresses and displacements. This information is then compared to criteria that indicate the conditions of failure. Advanced structural analysis may examine dynamic response, stability and non-linear behavior. There are Classical method and Numerical method.
1- Classical Method
The solutions can under certain conditions be superimposed using the superposition principle to analyze a member undergoing combined loading. Solutions for special cases exist for common structures such as thin-walled pressure vessels.
he solutions are based on linear isotropic infinitesimal elasticity and Euler–Bernoulli beam theory. In other words, they contain the assumptions (among others) that the materials in question are elastic, that stress is related linearly to strain, that the material (but not the structure) behaves identically regardless of direction of the applied load, that all deformations are small, and that beams are long relative to their depth. As with any simplifying assumption in engineering, the more the model strays from reality, the less useful (and more dangerous) the result.
2- Numerical Method
It is common practice to use approximate solutions of differential equations as the basis for structural analysis. This is usually done using numerical approximation techniques. The most commonly used numerical approximation in structural analysis is the Finite Element Method.
The finite element method approximates a structure as an assembly of elements or components with various forms of connection between them and each element of which has an associated stiffness. Thus, a continuous system such as a plate or shell is modeled as a discrete system with a finite number of elements interconnected at finite number of nodes and the overall stiffness is the result of the addition of the stiffness of the various elements. The behaviour of individual elements is characterized by the element’s stiffness (or flexibility) relation. The assemblage of the various stiffness’s into a master stiffness matrix that represents the entire structure leads to the system’s stiffness or flexibility relation. To establish the stiffness (or flexibility) of a particular element, we can use the mechanics of materials approach for simple one-dimensional bar elements, and the elasticity approach for more complex two- and three-dimensional elements. The analytical and computational development are best effected throughout by means of matrix algebra, solving partial differential equations.