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STRUCTURES Inés García Cáceres y Helena Gijón Jiménez
Types of structures - Frame structures -Shell structures -Arch structure -Mix and Match structures -Mass structures -Suspension structures
Frame structures -These structure are composed of long elements join each other at the end. -The elements are made of strong materials. -The space between the elements is empty space. -Advantages : they are relatively easy to build. -Disadvantages : they aren't good for strong impacts.
Shell structure -Are made of a thin outer layer of material that surrounds a volume. -The volume can be empty space or can be filled with something that has no structural relevance. -They maintains the required shape. -They keep their shape and support without a solid mass.
Arch -There are many type,but the semicircular arch, which was the roman arch still remains the most used. -The stone at the very top is called the keystone. -This makes it suitable for bridges since the large space left underneath can span a river ,stream or other obstacule.
Mass structures -There are simply made of clump material, filling the body completely. -They are made of low quality materials,but the structure, is normally thick. -Advantage:held in place by its own weight -Disavantage:heavy and occupy large amount of space.
Suspension structure -It hold and element by cables that are heald from the top of a tall column. -The space between one column and newt is called the ''span'' -Advantage: good for covering a very large span. -Disavnatage: expensive build
Structural elements -In an structure,the forces for every element are calculated and the element is designed to withstand them -The foundation is the element to the ground by friction. -The foudation is joined to the column by friction. -The column is joined to the foundations and to the primary beams -The beams and the column are joined by welding if they are metallic -In some cases the beam can be laid on the column that is healded by gravity.
Type of unions - All strutural elements mustbe somehow united to the other elements an the whole structure often united to the floor/ground as well. -PERMANET UNIONS: They are meant for strutures that will not need to be disassembled. Like: weldings, rivets, glue... -NON-PERMANET UNIONS: Are those designed to assemble and dissamble the elements of the structures as many times as necessary. Like: nuts and bolts, clamps, friction...
FORCES ON STRUCTURAL ELEMENTS A successful structure must be able to withstand all the forces that it will experience without toppling over or collapsing.The type of forces are: -tensional strain -comprenssion forces -shear strain -torsion forces -bending forces
Tensional strain Is the strain that causes an element to strech. It can be due to forces taht pull an element from its ends.
Compression forces They are those forces which cause an element to get squeezed or buckled. When you ''squeeze'' an element, it becomes shorter abd thicker. In the case of buckling, an element loses all its strenght and, if the force does not disappear quickly, the buckling continues until catastrophic failure.
Shear strain They act across a material in such a way that they can force one part of an elements to slide over another. Example: When you cut a paper with a pair of scissors, then you preduce a shear strain in the bigger than it can withstand and one part completely slides over the other until they are separated.
Torsion forces If you apply a turnig forces, (called ''torque'') at one end of a element and, if the elements is fixed to a support at the other ebd, the elements twists. If the element wasn't fixed at the other end it would just turn without changing shape.
Bending forces They act at an angle to a member (at 90º from the axis line in the drawing) making it bend.