|
In architecture and structural engineering, a truss is a static structure consisting of straight slender members inter-connected at joints into triangular units. The Parthenon on top of the Acropolis, Athens, Greece Architecture (from Latin, architectura and ultimately from Greek, αÏχιτεκτων, a master builder, from αÏχι- chief, leader and τεκτων, builder, carpenter) is the art and science of designing buildings and structures. ...
Taipei 101, the worlds tallest building as of 2004. ...
Look up Structure in Wiktionary, the free dictionary. ...
 Truss bridge for a single track railway, converted to pedestrian use and pipeline support Another view A Southern Pacific Railroad bridge, now part of the Iron Horse Regional Trail. ...
Another view A Southern Pacific Railroad bridge, now part of the Iron Horse Regional Trail. ...
A log bridge in the French Alps near Vallorcine. ...
History
The earliest trusses were made out of timber. The ancient Greeks used truss construction for their dwellings. In 1570 Andrea Palladio published I Quattro Libri dell'Architettura, which contained instructions for wooden trussed bridges. Ancient Greece is the period in Greek history which lasted for around one thousand years and ended with the rise of Christianity. ...
Andrea Palladio. ...
Front page of a Ist Edition: I Quattro Libri dellArchitettura I Quattro Libri dellArchitettura (The four books of Architecture) was published in 1570, in four volumes written by the architect Andrea Palladio (1508-1580), whose name is identified with an architectural movement named after him, Palladianism. ...
Statics of trusses Outer vertical members are in tension, lower horizontal members in tension, shear, and bending, diagonal and top members are in compression. The central vertical member stabilizes the upper compression member, preventing it from buckling. If the top member is sufficiently stiff then this vertical element may be eliminated. If the lower chord is sufficiently resistant to bending and shear, the outer vertical elements may be eliminated. The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection, the availability of machinery and the cost of labor. In other cases the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics. Modern materials such as post-stressed concrete and fabrication methods, such as automated welding, have significantly influenced the design of modern bridges. A log bridge in the French Alps near Vallorcine. ...
In order for a truss with pin-connected members to be rigid, it must be composed entirely of triangles. In mathematical terms, we have the following necessary condition for stability: Download high resolution version (1200x1600, 369 KB)Shanghai Shimao International Plaza under construction in Shanghai. ...
Download high resolution version (1200x1600, 369 KB)Shanghai Shimao International Plaza under construction in Shanghai. ...
Shanghai (Chinese: ; pinyin: ; Shanghainese: ), stuated on the banks of the Yangtze River Delta in East China, is the largest city of the Peoples Republic of China. ...
A mechanical floor, mechanical penthouse, or mechanical level is a floor of a high-rise building that is dedicated to mechanical and electronics equipment. ...
The word stability has a number of technical meanings, all related to the common meaning of the word. ...
where m is the total number of truss members, j is the total number of joints and r is the number of reactions (equal to 3 generally) in a 2-dimensional structure.
When m = 2j − 3, the truss is said to be statically determinate because the (m+3) internal member forces and support reactions can then be completely determined by 2j equilibrium equations, once we know the external loads and the geometry of the truss. Given a certain number of joints, this is the minimum number of members, in the sense that if any member is taken out (or fails), then the truss as a whole fails. While the relation (a) is necessary, it is not sufficient for stability, which also depends on the truss geometry, support conditions and the load carrying capacity of the members. A standard definition of mechanical equilibrium is: A system is in mechanical equilibrium when the sum of the forces, and torques, on each particle of the system is zero. ...
The word stability has a number of technical meanings, all related to the common meaning of the word. ...
Some structures are built with more than this minimum number of truss members. Those structures may survive even when some of the members fail. They are called statically indeterminate structures, because their member forces also depend on the relative stiffness of the members, in addition to the equilibrium condition. In statics, a construction is statically indeterminate when the static equilibrium equations are not sufficient to calculate the reactions on that construction. ...
Stiffness is the resistance of an elastic body to deflection by an applied force. ...
Vierendeel truss A special truss is the Vierendeel truss, named after the Belgian engineer Arthur Vierendeel [1], who developed the design in 1896. Also described as a Vierendeel frame, this truss has rigid upper and lower beams, connected by vertical beams. The joints are also rigid. In this statically indeterminate truss, all members are subject to bending moments. Trusses of this type are used in some bridges (see Vierendeel bridge), and were also used in the frame of the 'Twin Towers' World Trade Center. By eliminating diagonal members the creation of rectangular openings for windows and doors is simplified since this truss can reduce or eliminate the need for compensating shear walls. A rigid frame in structural engineering is the load-resisting skeleton constructed with straight or curved members interconnected by mostly rigid connections. ...
In physics, the moment of force (often just moment, though there are other quantities of that name such as moment of inertia) is a quantity that represents the magnitude of force applied to a rotational system at a distance from the axis of rotation. ...
A log bridge in the French Alps near Vallorcine. ...
A Vierendeel bridge is a bridge employing a Vierendeel truss. ...
WTC redirects here. ...
Analysis of trusses
 Cremona diagram for a plane truss The analysis assumes that loads are applied to joints only, not to the members. The estimated weights of bars are either omitted or, if required, they are applied to the joints (a half of the weight to each of the bar joints). As long as loads are applied only at the joints of a truss, and the joints act like "hinges", every member of the truss is in pure compression or pure tension -- shear, bending moments, and other more complex stresses are all practically zero. This makes trusses easier to analyze. This also makes trusses physically stronger than other ways of arranging material -- because nearly every material can hold a much larger load in tension and compression than in shear, bending, torsion, or other kinds of stress. Structural analysis of trusses of any type can readily be carried out using a matrix method such as the matrix stiffness method or the flexibility method. Download high resolution version (500x775, 39 KB)Cremona (Maxwell) diagram to calculate forces in truss members. ...
Download high resolution version (500x775, 39 KB)Cremona (Maxwell) diagram to calculate forces in truss members. ...
A hinge is a mechanical device that connects two solid objects, allowing rotation between them. ...
Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ...
Tension is a reaction force applied by a stretched string (rope or a similar object) on the objects which stretch it. ...
In physics and mechanics, shear refers to a deformation that causes parallel surfaces to slide past one another (as opposed to compression and tension, which cause parallel surfaces to move towards or away from one another). ...
In physics, the moment of force (often just moment, though there are other quantities of that name such as moment of inertia) is a quantity that represents the magnitude of force applied to a rotational system at a distance from the axis of rotation. ...
Figure 1 Stress tensor A mature tree trunk may support a greater force than a fine steel wire but intuitively we feel that steel is stronger than wood. ...
Structural analysis comprises the set of physical laws and mathematics required to study and predict the behavior of structures. ...
In structural engineering, the matrix stiffness method (or simply stiffness method) is a matrix method that makes use of the members stiffness relations for computing member forces and displacements in structures. ...
In structural engineering, the flexibility method is the classical consistent deformation method for computing member forces and displacements in structural systems. ...
Forces in members On the right is a simple, statically determinate flat truss with 9 joints and (2 x 9 − 3 =) 15 members. External loads are concentrated in the outer joints. Since this is a symmetrical truss with symmetrical vertical loads, it is clear to see that the reactions at A and B are equal, vertical and half the total load. In statics, a construction is statically indeterminate when the static equilibrium equations are not sufficient to calculate the reactions on that construction. ...
Square with symmetry group D4 Symmetry is a characteristic of geometrical shapes, equations, and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ...
The internal forces in the members of the truss can be calculated in a variety of ways including the graphical methods: In physics, force is that which changes or tend to change the state of rest or motion of a body. ...
Or the analytical Ritter method (method of sections). Luigi Cremona (7 December 1830, Pavia - 10 June 1903) was an Italian mathematician. ...
Carl Culmann (July 10, 1821 - December 9, 1881) was a German structural engineer. ...
Structural analysis comprises the set of physical laws and mathematics required to study and predict the behavior of structures. ...
In the Cremona method, first the external forces and reactions are drawn (to scale) forming a vertical line in the lower right side of the picture. This is the sum of all the force vectors and is equal to zero as there is mechanical equilibrium. The concept of scale is applicable if a system is represented proportionally by another system. ...
This article is about vectors. ...
In physics and in vector calculus, a spatial vector is a concept characterized by a magnitude, which is a scalar, and a direction (which can be defined in a 3-dimensional space by the Euler angles). ...
A standard definition of mechanical equilibrium is: A system is in mechanical equilibrium when the sum of the forces, and torques, on each particle of the system is zero. ...
Since the equilibrium holds for the external forces on the entire truss construction, it also holds for the internal forces acting on each joint. For a joint to be at rest the sum of the forces on a joint must also be equal to zero. Starting at joint Aorda, the internal forces can be found by drawing lines in the Cremona diagram representing the forces in the members 1 and 4, going clockwise; VA (going up) load at A (going down), force in member 1 (going down/left), member 4 (going up/right) and closing with VA. As the force in member 1 is towards the joint, the member is under compression, the force in member 4 is away from the joint so the member 4 is under tension. The length of the lines for members 1 and 4 in the diagram, multiplied with the chosen scale factor is the magnitude of the force in members 1 and 4. In physics, static equilibrium, or neutral balance, exists when the forces (actions), and torques, on all components of a defined system are balanced such that no component is undergoing an acceleration relative to the designated frame of reference. ...
A factor can be: a person acting for another as a mercantile and/or colonial agent, or, in Scotland, a Factor is a person or firm managing property on behalf of the owner; in mathematics, a multiplicative factor is a synonym for coefficient a number that is a divisor of...
// Real numbers The magnitude of a real number is usually called the absolute value or modulus. ...
Now, in the same way the forces in members 2 and 6 can be found for joint C; force in member 1 (going up/right), force in C going down, force in 2 (going down/left), force in 6 (going up/left) and closing with the force in member 1.
The same steps can be taken for joints D, H and E resulting in the complete Cremona diagram where the internal forces in all members are known.
In a next phase the forces caused by wind must be considered. Wind will cause pressure on the upwind side of a roof (and truss) and suction on the downwind side. This will translate to asymmetrical loads but the Cremona method is the same. Wind force may introduce larger forces in the individual truss members than the static vertical loads. Wind is the roughly horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earths surface. ...
A roof tiled in imitation of thatch at Croyde, north Devon, England Rooftops in Vietnam Snow on the roof The roof, the top covering of a building, is one of the universal structures found on all buildings. ...
Design of members Once the force on each member is known, the next step is to determine the cross section of the individual truss members. For members under tension the cross-sectional area A can be found using A = F × γ / σy, where F is the force in the member, γ is a safety factor (typically 1.5 but depending on building codes) and σy is the yield tensile strength of the steel used.
The members under compression also have to be designed to be safe against buckling. Cross section may refer to the following In geometry, Cross section is the intersection of a 3-dimensional body with a plane. ...
Factor of safety (FoS), also known as Safety Factor, is a multiplier applied to the calculated maximum load (force, torque, bending moment or a combination) to which a component or assembly will be subjected. ...
A building code is a set of rules that specify the minimum acceptable level of safety for constructed objects such as buildings and nonbuilding structures. ...
Yield may mean: In economics, yield is a measure of the amount of income an investment generates over time (related to return on investment). ...
It has been suggested that this article or section be merged into Strength of materials. ...
In engineering, buckling is a failure mode of a structural member characterised by a failure to react to the bending moment generated by a compressive load. ...
The weight of a truss member depends directly on its cross section -- that weight partially determines how strong the other members of the truss need to be. Giving one member a larger cross section than on a previous iteration requires giving other members a larger cross section as well, to hold the greater weight of the first member -- one needs to go through another iteration to find exactly how much greater the other members need to be. Sometimes the designer goes through several iterations of the design process to converge on the "right" cross section for each member. On the other hand, reducing the size of one member from the previous iteration merely makes the other members have a larger (and more expensive) safety factor than is technically necessary, but doesn't require another iteration to find a buildable truss.
The effect of the weight of the individual truss members in a large truss, such as a bridge, is usually insignificant compared to the force of the external loads. A log bridge in the French Alps near Vallorcine. ...
Design of joints After determining the minimum cross section of the members, the last step in the design of a truss would be detailing of the bolted joints, e.g., involving shear of the bolt connections used in the joints, see also shear stress. There are three kinds of fastener given the name bolt. ...
In physics and mechanics, shear refers to a deformation that causes parallel surfaces to slide past one another (as opposed to compression and tension, which cause parallel surfaces to move towards or away from one another). ...
Shear stress is a stress state where the shape of a material tends to change (usually by sliding forces -- torque by transversely-acting forces) without particular volume change. ...
Download high resolution version (1350x900, 339 KB)A picture of the Old Little Belt Bridge in Denmark This image was taken by Ævar Arnfjörð Bjarmason on 2004-04-10 using a Kodak EasyShare DX4330 camera. ...
Download high resolution version (1350x900, 339 KB)A picture of the Old Little Belt Bridge in Denmark This image was taken by Ævar Arnfjörð Bjarmason on 2004-04-10 using a Kodak EasyShare DX4330 camera. ...
The bridge seen from Snoghøj The Little Belt Bridge, also known as The Old Little Belt Bridge, is a truss bridge over the Little Belt strait in Denmark. ...
A log bridge in the French Alps near Vallorcine. ...
Truss Types A metal plate-connected wood truss is a roof or floor truss whose wood members are connected with metal connector plates.
There are two basic types of trusses. The pitched truss or common truss is characterized by its triangular shape. It is most often used for roof construction. Some common trusses are named according to their web configuration. The chord size and web configuration are determined by span, load and spacing. The parallel chord truss or flat truss gets its name from its parallel top and bottom chords. It is often used for floor construction.
See also A truss bridge is a bridge composed of connected elements (typically straight) which may be stressed from tension, compression, or sometimes both in response to dynamic loads. ...
A Vierendeel bridge is a bridge employing a Vierendeel truss. ...
Interior structure of a covered lattice bridge A lattice bridge is a form of truss bridge that uses a large number of small and closely spaced diagonal elements that form a lattice. ...
A covered bridge is a bridge, often single-lane, with enclosed sides and a roof. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
Compressive stress is the stress applied to materials resulting in their compaction (decrease of volume). ...
Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ...
Simplified space frame roof with the nearest unit polygon hightlighted in blue A space frame is a truss-like, lightweight rigid structure constructed from interlocking struts in a geometric pattern. ...
In geometry, the Andreini tessellations are the complete set of 28 uniform (space-filling) honeycombs of 3-space. ...
In mechanics and biomechanics, tensegrity or tensional integrity is a property of objects with components that use tension and compression in a combination that yields strength and resilience beyond the sum of their components. ...
Schematic section of electric guitar neck Truss rod is a device to stabilize and adjust profile of guitar neck. ...
This article or section does not cite its references or sources. ...
Mechanics of structures is a field of study within applied mechanics that investigates the behavior of structures under mechanical loads, such as bending of a beam, buckling of a column, torsion of a shaft, deflection of a thin shell, and vibration of a bridge. ...
This page is a candidate to be copied to Wiktionary. ...
Structural steel is steel construction material formed with a specific shape and certain standards of chemical composition and strength. ...
External links |
Feeds |
Contact