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Sunday, October 21, 2007
Kates Playground Members Full Set
serve for that architecture should not move or deform so as to prevent its use without breaking. To achieve this there are structures that can be undifferentiated when they not only attend such functions, or different only if ordered structure function. structure definition: Set bodies linked together and arranged to receive and withstand the forces acting on these and forward them to the ground. Is an organized set it implies a certain organization, both geometric and links. These are the possible limiting movement of a body and there are three types: Mobile joint, cancels travel in one direction fixed joint, prevent movement in both directions, and embedding that cancels both displacements and rotations.
When thinking about the structures is crucial to analyze the loads on the building considering its function (home, library, storage), materials to be used (heavy or light), the place where it will reside (winds, possibility of earthquakes), or as long as it can vary its use or condition.
loads Classification:
1) Static: are those who do not suffer abrupt changes. May be permanent (weight structure, complementary elements, etc.) or transient (people, furniture, etc.).. These are all gravity loads and therefore have the direction of the radius of the Earth, are constant and the most important, what are the easiest to predict.
2) Dynamics: those values \u200b\u200bare changing rapidly. Can be resonant (seismic and wind) or impact (sudden rush of vehicles, materials sudden shock, shock waves, etc..).
All loads can be balanced by the reactions and thereby prevent any movement of translation or rotation. So that there is no displacement and the building is in equilibrium the sum of the forces in the x and y axis must be zero as the sum of moments.
There are several types of balance:
1) Indifferent: in which all positions are balanced in a small disturbance which the body will be in another position. No good for architecture.
2) Unstable: is one who does not return to its original configuration after a small perturbation. No good for architecture.
3) Stable: Whenever you get a small perturbation restores its original position. This is the one used for architecture and is the first basic requirement of a structure.
All solid experience deformations to be applied by outside forces. At the beginning of deformation, the particles originating from internal forces increased the intensity of external forces to balance them. Reached this situation is said that all particles of the body are balanced between internal and external forces (internal equilibrium).
of tensions will study the basic compression and tension, in which the material "works" with the same intensity throughout the section and the efforts made, bending, where the "work" does not occur homogeneously (existence fiber tension to neutral and compressed),
1) Compression: is a normal stress of converging forces with equal and opposite direction. The particles of material tend to crowd one another, producing a deformation in the material that is shortening the piece in the sense of direction of force and the thickening of the section perpendicular to the direction of the effort. It is important to mention that compression occurs in relatively short pieces because otherwise it will produce the phenomenon of buckling (lateral bending and will be mentioned later). 2) Drive: As compression is a cooperative effort forces normal and reverse direction but diverge, so the deformation is given by the removal of the particles that make up the material, extending the piece in the sense of the direction of the force and the reduction of the cross section to address
effort. 3) Flex: is given by the combination of the two basic states of stress described above: the compression and traction. Occurs when a piece is a stress perpendicular to its longitudinal axis and supported by one or more points do not coincide with the line of action of loads. The strain is the elongation fiber traction and shortening of the compressed. In between these there is a neutral axis in which the fibers remain unchanged.
buckling or lateral bending effect: It is straight across bar whose length is significantly larger than the smaller side. This bending occurs long before the collapse of compressive material and depends on the slenderness (ratio between the upper and lower side of the compressed element), the form of the section of material, the material itself, links, and the magnitude of loads.
Resistance is the second basic requirement of a structure and analyze the forces developed inside the material originated as a result of forces applied on it, and the balance between the two systems of forces.
Another aspect to consider is the material stiffness , ie the relationship between the cause (force) and effect (producing strains). The structure and every part of it does not have a single rigid but as many as different actions you can apply. Such rigidity depends on the geometric organization, links and the characteristics of the material.
Finally, it is important to refer to effectiveness: Third basic requirement of a structure. It is the relationship between results and resources used . Is closely linked to the size, configuration geometric and materials.
Finally, say that there are certain ways to solve problems involving geometric configuration in relation to the use of materials, to each of these forms are called structural types.
main problems of architectural structures are: 1) Cover lights, 2) Move vertically to the ground loads, 3) Supporting horizontal thrust.
1) 1st problem - Cover Lights:
Light is the distance between the supports of an element that covers a space.
a) Structures compressed The most typical examples are the arc and vault. To understand its operation is necessary to analyze the behavior of its centerpiece, the keystone of the arch. It should come down to "push" out to the two following parts (contraclaves). Its vertical load is divided into two oblique forces that drive each of the two aforementioned contraclaves. Each of these forces combined with the weight of the new force resulting in a more "bowed down" to act on the next piece. So that the resultant force of each piece is made with the burden of the next piece. Must analyze the direction of the final result because of not being perfectly vertical horizontal thrusts appear to be balanced with buttresses, flying buttresses (Gothic) or internal clamping thin.
most appropriate materials to build both arches and vaults are those with a good compression behavior such as stone (natural and artificial), brick, wood, etc. ..
b) Structures tension to The most common are those suspended by cables. The cables take different forms depending on the disposition of the charges on him. In general, the structures "hung" are relatively low weight and have low stiffness.
The cable system is the only one who can build with the same geometry (Only varies the size of the tension members) small elements such as huge as the system is independent of the size of the light.
Membranes: Its own weight is relatively insignificant and do not depend on the stiffness of the material. As such material is not rigid in itself, this feature should be achieved through a drive geometry. One possible solution is the use of forms with opposing curves. Supported by their shape, are inflexible structures using flexible materials. These materials should be achieved without stiffness keep the shape under all load conditions should support the building. The lightness, while being a disadvantage, rooted many difficulties must be cinched down instead of being borne upwards by example.
c) bent structures
Before an external force applied and the two reactions in the two support points the beam begins to deform. If we increase the applied force will come a time when the beam is broken. If we look, we see that at each end so there was a twist that caused a moment (when abroad). To achieve balance, showed an inner strength that grew as grew outside (now inside).
If we look at a "slice" of the beam center, we see that the internal forces compress the material on top of a maximum on the edge and then descends to a failure to solicitation in the middle and then began to pull up to the maximum in the other edge. This concludes that not all the material used is used with the same degree of order.
If the beam is balanced, the bending moment (outside) is equal to the moment resistance (indoor). The first increases by increasing strength or light (distance between supports). To give more strength to the beam can be used more resistant materials or increase the height of the section for the moment resistance is higher. But while this happens, the weight increases and as the material does not work homogeneously so all is not used to its full potential (only the ends) and with increasing height of the piece increases the material well "idle."
What materials I can use? Those who respond to requests from both compression and tension. Among these we can distinguish the wood and steel, but can also be given a combination of different materials that work well for each of the two solicitations, is the example of concrete where concrete works best compression and tensile iron .
Strategies to improve the efficiency
i. material is placed where you actually need and lighten less popular areas (closer to the neutral axis). This is very easy on the steel which displayed different profiles such as Double T. With the concrete implementation is difficult in the formwork to achieve appropriate forms, and the wood is useless. If this strategy is extremely possible to separate tablets tensile cords holding only a union between them to work together. But it introduces the problem of how to unite both parties to maintain rigidity. There are two different types of unions, rigid and articulated by triangles (geometrically deformable).
ii. Another way to separate the strands tablets and traction is obtained from elements thin, low resistance to bending that allow it to fold as a grant stiffness.
d) crosslinked structures The most characteristic example is the truss characterized by its lightness and ability to withstand heavy loads. They are mainly used in large buildings with lights, and ceilings of warehouses, stores, churches and buildings are generally large spaces inside. It consists of a succession of short pieces, tied in knots, which form triangles (geometrically deformable). Between truss and truss are the straps. The various parts that make up this system are pairs, the tensor, the pendolón, diagonals and uprights.
2) the 2nd problem - vertically transmit loads to the ground.
This is done by column, pillars and supporting walls and more. The introduction of modern materials with high compressive strength such as steel columns can be used to build much thinner than with stone or concrete. But this thinness, introduces a limitation on the buckling that occurs in long, thin elements that under compressive stress experience a lateral bending and occasionally collapse. Buckling depends on the slenderness, the shape of the cross section (those showing better Most of the material from the center such as round hollow sections, the double-T profile, etc.), and restrictions on their ends (the embedding gives greater resistance to buckling).
3) 3rd problem - horizontal thrusts. These can be produced for different reasons and permanent (long acting without changing such as the thrust produced by a drop) or possible (not always but sometimes act are those produced by winds and earthquakes).
The wind pressure is distributed over the exposed faces of the building, resulting in a force applied at the geometric center of faces. This force generates the ground reaction triggers a moment called "tipping point." This increases the power of the wind or by an increased distance between the wind and its reaction (building height). So that the building is at rest the overturning moment must be balanced with other time in equal and opposite, the "stabilizing moment." The stability of a building increases its weight and the breadth of its base.
's quake is another possible push. The energy released by an earthquake propagates through the crust in the form of vibrations that cause displacement of the ground in any direction (horizontal or vertical). The destructive force of the quake was explained on the principle of inertia which states that every body has a reaction to change its state of motion. This reaction is directly proportional to body mass. Thus, the earthquake occurred, each of the parts of the building "reacts" to oppose the motion with a force proportional to its mass and opposite movement of the ground. Unlike the wind, the weight does not contribute to the stability but also increases the destructive force.
Answers to achieve greater stability.
In columns: depends essentially on their links. By having a smaller base than its height shows little reaction overturning. To maintain a stable balance should be linked or embedded articulated to other elements. When inserting it modifies the behavior of the column as it is subjected to bending. The walls
: Responsiveness to a drive depends on its direction: If the force is perpendicular to the wall must be embedded (if resistant to bending) or linked with elements that prevent them from overturning. If the force on the wall is parallel to this, substantially improves its stability. The lower and a wall length is greater stability.
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