Archive for October, 2011

What is Structural Engineering?

October 15, 2011

Structural engineering is a branch of engineering which deals with the analysis and design of various structural systems. It is more commonly identified with civil engineering. Structural engineering deals with conception, design, and construction of the structural systems that are needed in support of human civil engineering
“Structural engineering is the art of molding materials we don’t wholly understand, into shapes we can’t fully analyze, so as to withstand forces we can’t really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance.” …James E. Amrhein 
Engineers are the invisible presence that brings the architect or designer’s concept into reality. In a broad sense, architects create the skin defining the usable flow of space that we live and work – occasionally appearing to defy gravity. The Engineer relies on the physical sciences to create a “skeleton” of interconnected elements that support the shell in the physical world. He or she uses the laws of physics (equilibrium) to design the structure (in part and in whole) to safely support the weight of the permanent building materials, changing movement of people, and short term applications of snow and water. These are defined as the vertical “gravity” while resisting the “horizontal” forces of nature due to the worst case comparing; wind and seismic events that may act simultaneously. Equilibrium is achieved by anchoring the structure to an adequate foundation based on the recommendations of a geotechnical (soils) engineer. Starting at the top and working down to the foundation, the engineer designs each element and the connections supporting the combination of elements to create the “structure” – a sum of its elements (whether a building, soil retaining wall or a bridge). The engineer follows building codes, enacted in state congress to create law that provides a minimum requirement to protect life safety.
Structural engineering is mainly involved with two activities
    1. Structural Analysis
    2. Structural Design
Structural design is the process of selecting members of required dimensions such that they provide adequate stability under service loads. There are two conditions that a structural designer must keep in mind. One is “stability” and the other is “serviceability”. Stability of a structure means that it can resist the loads acting on it satisfactorily and that the structure will not collapse immediately (that is, it provides enough time to escape to safety). Serviceability refers to certain conditions that are required so that the structure remains serviceable. For example, consider a bridge that can resist service loads without collapse. This is a “stable” structure. Now assume that this bridge shows abnormal deflections. The deflections could be such that the bridge feels bouncy and could lead to steering problems for vehicles crossing it at high speeds. As such this may not cause the structure to collapse. So we can say that the structure is stable, but according to serviceability criterion it is not serviceable because people could feel afraid of using the bridge.
In the design and construction of the foundation and framing for buildings and bridges, the main materials used are concrete, steel, timber, and masonry. Steel can further be subdivided into two subsections: hot-rolled steel and cold-formed steel. Cold-formed steel applies to material of approximately 1/8″ or less in thickness that is either folded or roll-formed from flat sheets into structural shapes while at room temperature.
All structures must be designed to carry all foreseeable loads with a suitable factor of safety. Clearly it would be unsafe to walk on a structure that was adequate but had no margin of safety built in. With this in mind, most countries have standards that prescribe the required minimum safety factors for structures. The minimum is usually a factor of about 1.7. This is not a factor to allow for overloading or poor workmanship. If there is a possibility of overloading or poor workmanship, the design loads must be increased to account for the overloading and the strengths of the materials upon which the design is based must be reduced to account for the poor workmanship. The safety factor must remain complete, as it is there to account for the unexpected events and unforeseen circumstances. If a structure becomes worn, loose, cracked or corroded, it should always be repaired so the safety factor is preserved.
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Importance of Structural Engineers in House Design

October 13, 2011

Structural civil engineering is a part of civil engineering. The primary goal of a structural engineer is to design a structure, regardless of the type, that’s built with solid integrity, with a great amount of care paid to dependability and safety of the structure.
What is included in structural engineering? Many things like planning, projecting, and attention to detail. A structural engineer may also design and build larger building structures, residential house, commercial shopping complex, industrial buildings, group housing, apartments etc.
However, structural engineering in the construction area has to do with tunnels, dikes, retaining walls or additional walls, bridges, and edifices. They must be creditworthy for the systems and factors that support these structures. Several components go into projecting the structure system of a construction or any large item for that matter. Not only do they have to have safety as a foremost consideration but also have to think about other details such as how well the construction functions for a business organization or residence. 
Structural Engineering carries additional responsibility for checking the power of the structure to resist water, wind, quakes, tsunamis, and sabotage or acts of wildness. Fundamentally, the life and durability of a structure depends upon the experience, knowledge, and expertise of those within the civil engineering area.
Strength design and the design of allowable stress use a combination of many dead or live loads so as to engineer a very safe structure. It additionally uses a variety of resistance factors for each individual structural element so as to calculate precisely, the factor of safety. The values of materials cannot always be repeated. For example, one steel beam will always have a different value of resistance from the other.
The advantage of Load Resistance Factor Design or strength design is that it returns to the idea of factor of safety. According to Civil Engineers, one can adjust the factor of safety simply by varying the materials used, failure types and the mixture of dead and live loads. Calculations in strength design give the engineer the flexibility of adjusting for axial compression, bending, shear and other similar impact loads at a much higher level than required. This gives a higher degree of factor of safety.