MODULE 1 Flashcards
The prime purpose of structures is to carry loads and transfer them to the ground. Structures may be classified according to use and need. A general classification is:
- residential
- commercial
- institutional
- exhibition
- industrial
residential
houses, apartments, hotels;
commercial
offices, banks, department stores, shopping
institutional
schools, universities, hospitals, gaols;
exhibition
churches, theatres, museums, art galleries, leisure centres, sports stadia, etc.;
industrial
factories, warehouses, power stations, steelworks, aircraft hangers etc.
bridges
truss, girder, arch, cable suspended, suspension;
towers
water towers, pylons, lighting towers etc.;
special structures
offshore structures, carparks, radio telescopes, mine headframes etc.
loadbearing walls or columns in compression and walls taking in-plane or transverse loads. Construction is very durable, fire resistant and aesthetically pleasing.
MASONRY
framed or shear wall construction in reinforced concrete is very durable and fire resistant and is used for the tallest buildings. Reinforced or prestressed, is used for floor construction in all buildings, and foundations are required for all buildings
CONCRETE
loadbearing walls resist loads transmitted to them by floor slabs. Stability depends on gravity loads.
Gravity masonry structures
a steel or concrete skeleton collects loads from plate elements and delivers them to the foundations.
Framed structures
a curved surface covers space and carries loads.
Shell structures
cables span between anchor structures carrying membranes.
Tension structures
a membrane sealed to the ground is supported by internal air pressure.
Pneumatic structures
Steel-framed structures may be further classified into the following types:
- single-storey,
- multistorey,
- space structures
- tension structures and cable-supported roof structures;
- stressed skin structures,
single- or multibay structures which may be of truss or stanchion frames or rigid frame of solid or lattice members;
single-storey
single or multibay structures of braced or rigid frame construction
multistorey
space decks and domes are redundant structures, while towers may be statically determinate space structures;
space structures (space decks, domes, towers etc.)
where the cladding stabilizes the structure.
stressed skin structures,
Buildings must be designed and constructed according to the provisions of a building code, which is a legal document containing the requirements related to such things as
Structural Safety
Fire Safety
Plumbing
Ventilation
Accessibility to the physically disabled
AISC
American Institute of Steel Construction
AASHTO
American Association of State Highway and Transportation Officials
ACI
American Concrete Institute
NSCP
National Structural Code of the Philippines
It is determining and selecting the overall dimensions of the supporting frameworks or members in a structure. Here, we determine a required cross-sectional area for a certain structural member and select the safest dimensions based on this area. Also, in RC, we determine the required number of steel bar to be used on a member just to resist and safely carry the effects caused by loadings.
STRUCTURAL DESIGN
Structures are designed to resist many types of loads including dead loads, live loads, wind loads, and earthquake loads. The complete design must take into account all effects of these loads, including all applicable load combinations.
Loads and Stresses
to be assumed in design consists of the weight of steelwork and all material permanently fastened or supported by it.
Dead Load
must be that stipulated by the applicable code under which the structure is being designed or that dictated by the conditions involved.
Live Load
For structures carrying live loads which induce impact, the assumed live load must be increased sufficiently by the percentage provided in the given table below.
Impact loads
STEEL COMPOSITION & GRADES
Structural steels can be grouped according to their composition as follows:
- Plain carbon steels
- Low-alloy steels
- High-alloy or specialty steels
mostly iron and carbon, with less than 1% carbon.
Plain carbon steels
iron and carbon plus other components (usually less than 5%). The additional components are primarily for increasing strength, which is accomplished at the expense of a reduction in ductility.
Low-alloy steels
similar in composition to the low-alloy steels but with a higher percentage of the components added to iron and carbon. These steels are higher in strength than the plain carbon steels and also have some special quality, such as resistance to corrosion.
High-alloy or specialty steels:
PROPERTIES OF STEEL
Yield Stress
Tensile Strength
Modulus of Elasticity
Ductility
Toughness
Weldability
Poisson’s Ratio
Shear Modulus
is that unit tensile stress at which the stress-strain curve exhibits a well(defined increase in strain (deformation) without an increase in stress.
Yield Stress, Fy
is the largest unit stress that the material achieves in a tension test
Tensile Strength, Fu
is the slope of the initial straight-line portion of the stress-strain diagram. It is usually taken as 200,000 MPa for design calculation for all structural steel.
Modulus of Elasticity, E,
is the ability of the material to undergo large inelastic deformations without fracture.
Ductility
is the ability of the material to absorb energy and is characterized by the area under stress-strain curve.
Toughness
is the ability of steel to be welded without changing its basic mechanical properties.
Weldability
is the ratio of the transverse strain to longitudinal strain. Poisson’s ratio is essentially the same for all structural steels and has a value of 0 in the elastic range.
Poisson’s Ratio
is the ratio of the shearing stress to shearing strain during the initial elastic behavior
Shear Modulus
The steel enters to a continuous casting system where it solidifies and passes through series of rollers
Hot-rolled
Bending thin material such as sheet steel or plate into the desired shape without heating.
Cold-formed
