mechanical action of a structure 1. control their own weight 2. Receive additional loads 3. Transmit them internally 4. Discharge them to the foundations/ground
must be converted into forces to the mathematically analyzed
may be further visualized by converting the forces into vectors
1. the flow of forces 2. their geometry 3. the material used
structures are defined through
force- a quality which induces a solid to move or to change its state (or shape)
loads- forces that act on a solid from the exterior
grav force- the fore by means of which mass of the earth pulls….
digram: behavior of structure: force/loads/gravitational force
moment- the turning motion induces by a couple or exerted by a force on a solid of which the center of motion lies outside the direction of force
stress- the internal (resistant) force per unit area in a solid from external forces
resistance- the force that a solid can withstand deformation or motion induced by external forces
equilibrium- state when all forces are balanced so there is no motion
diagram: behavior of structure: moment/stress/ resistance/ equilibrium
constraining and sheering forces
structures are devices for
1. weight of the building and its live (utilitarian) loads 2. kind of usage (consequences of operation) of the building 3. properties and articulation of the building substance 4. influences and conditions of the location and surroundings
the forces are determined by 4 conditions specific to each building
diagram: diversity of forces in structures: stress
diagram: forces in structures: distribution
diagram: forces in structure: structural members
1. adjustment of the structure to the forces: form active structure 2. dissection of the forces: vector active structure 3. confinement of the forces: section active structure 4. dispersion of the forces: surface active structures
diagram: the essence of structure: the redirection of forces
5. collection and grounding of loads: height active structure
diagram: the essence of structure: the redirection of forces cont.
are systems of flexible, non rigid matter, in which the redirection of forces is effected by particular FORM design and characteristic FORM stabilization
diagram: type 1 form active structures
cable structures, tent structures, pneumatic structures, arch structures
example of form active structures
systems of short, solid, straight lineal members, in which the redirection of forces is effected by vector partition, i.e., by multidirectional splitting of single force simply to tension or compressive elements
diagram: type 2 vector active structures
flat trusses, curved trusses, space trusses
ex: pompidou, paris
examples of vector active structures
systems of rigid, solid, linear elements, in which redirection of forces is effected by mobilization or sectional forces
diagram: type 3 section active structures
beam structures, frame structures, slab structures
ex: willis faber & dumas office building
examples of active structures
systems of flexible or ridged planes able to resist tension, compression or shear, in which the redirection of forces is effected by mobilization of sectional forces
diagram: type 4 surface active structures
plate, folded, shell
ex: sports palace, rome
examples of surface active structures
systems in which the redirection of forces necessitated by height extension, i.e. collection and grounding of story loads and wind loads, is effected by typical height proof structures- high rises
diagram: type 5 height active structures
amount of force quantified as the weight if the body, measures in
-lb (pounds or larger collection of lb)
-N (newtons ” “)
orientation of the path of the force. described by the angle that the line of action makes with some reference line, such as the horizon.
direction of the force/ line of action
diagram: unites of measurement
____ of the force with respect to the lines of action of other forces
position of the line of action
an object is in equilibrium when a system is forces action on it produces no motion
external forces are redirected through sectional fabric (forces)
system of redirecting forces
diagram: direction of forces?
diagram: shear forces cont.
diagram: horizontal shear
diagram: internal rotation moment
diagram: beding and bending resistance
diagram: torsion- bearing- deflections
a structure comprising one or more triangular hits constructed with straight members whose ends are connected at joints referred to as NODES
external forces and reactions to those forces are considered to act only at the nodes and result in forces un the members which are either tensile of compressive forces. – moments (torques) are excluded bc all the joints in a truss are treated as pinned, allowing single axis rotation.
forces and trusses
where all the members and nodes lie within a two dimensional plane
members and nodes extending into three dimensions
top beam in a truss, usually in compression
bottom beam in truss, usually in tension
interior beams of a truss and the area inside them
webs & panels
diagram: forces in planar trusses
diagram: analysis of planar truss
bending, sliding, tilting, shear
to stabilize against: buckling, breaking, twisting, vibrating
diagram: buildings- forces and moments
diagram: responses for preventing failures
diagram: stability of structures
diagram: summary of beam internal forces
diagram: dominant stress states
diagram: rigid structures/ flexible structures
diagram: rigid structures
diagram: rigid structures cont.
diagram: lateral design strategies
diagram: lateral stability
diagram: structural supports
under loads they cannot be divorced rom each other. they are so interrelated that often the distinction between the two is vague at best.
structural properties of material and the behavior of structures…
ductility and brittleness, elasticity, and plasticity, are also used to describe the behavior or an entire structure of components of a structure.
properties of material
carries loads primarily in compression, these dominated arch for centuries because of the availability of material at the time- stone and brick which are brittle- extremely durable
the arch, vault, and dome
less brittle then stone, limited to minor buildings or components of buildings because of its lack of durability
revived the beam as a horizontal spanning element because of its tensile strength. large openings were possible without arches, progression from load bearing masonry to skeleton frame
wrought iron, cast iron
prestressed concrete, high strength steels, reinforced concrete, concrete masonry
one that does not deform at all under the action of loads- aka it won’t stretch, shorten, bend, or change shape regardless of the magnitude of the load places on it.
stress in nearly always accompanied by deformation of the member. the exception to this rule is a rigid body. in the real world, a rigid body does not exist- all materials deform when loaded- deformations in buildings are usually too small to be visible.
ductility and brittleness
materials that produce large deformations before failure. it has equal strength in compression and tension
metals- pure metals are more ductile than their alloys
materials that do not deform much before failure. stronger in compression than in tension.
brick, stone, concrete, glass
fully recoverable from deformation after the load is removed.- elasticity-
metals can sustain large deformations, usually greater than %10. they are elastic up to a certain stress level, and if loaded beyond that stress value, they are plastic- that is, their deformation beyond that point is permanent.
does not recover from its deformation after the removal of the load- inelastic, plasticity
availability, strength, stiffness, speed of erection, cost/economics, ability to accommodate movement, durability, disposal
factors in material selection
framework or skeleton of beams and columns is used to carry the structural loads down the building to the foundation- framework is usually of steel or reinforced concrete, or in small structures of timber or aluminum. external and internal walls are non-structural and support no loads
walls are load-bearing and usually masonry, but may be reinforced concrete.
walls, floors, beams, columns, pitched roofs, foundations
materials used for particular structural elements
steel frame, reinforced concrete frames, precast concrete frames, timber frames, load-bearing masonry, hybrid schemes, e.g. steel frames with precast concrete floors, hybrid
most common types of structural systems for buildings
need for flexibility
access to the site
experience of the designers
experience of the contractors
availability of materials
chic between construction systems will depend on what factors
diagram: shear force diagram
1. identify all info and draw diagram 2. construct a red-body-diagram and solve for all unknown reaction forces 3. cut the beam, draw a fed, and solve for the unknown m and v at the cut in terms of x 4. plot the moment and shear equations developed in step 3
steps for shear and moment diagram
diagram: structural properties
diagram: structural properties cont.
diagram: compressive and tensile stresses in components
diagram: compressive and tensile stresses in members of a suspension bridge
section through a concrete beam
removing the material from the central region of the cross section (where the stresses are low) and placing it closer to the extremes edges of the cross section (where the stresses are high)
strategies to improve the structural efficiency of members subjected to bending
diagram: deformation caused by shear force
construction started in 2005. however on may 13 2007, with the building still under construction, a storm hit the city. the high winds and a lack of diagonal bracing, caused a 1 m twist in the steel structure between floor 28 and 40.
torre escollera in cartagena
the bridge was made of aluminum decking and stiffened by suspension cables in the horizontal plane. no attempt was make to stiffen it in the vertical plane.
tacoma narrows bridge
hyatt regency walkway collapse, kansas city
may be related in a wide variety of ways from domination by structure to disregard for form and aesthetic- 6 broad headings
-ornament of structure
-structure as ornament
-structure as arch
-structure as form generator
structure and arch
building has little more than visible structural armatures adjusted in fairly minor ways for visual reasons- structure and arch expression coexist in harmony
ornamentation of structure
the manipulation of structural elements by criterial which are principal visual- the structure is given visual prominence but unlike ornamentation os structure, the design process is driven by visual rather than by technical considerations.
structure as ornament
the limits of what was technically feasible were approached and in which no compromise with structural requirements was possible- structure without ornament, or structure as architecture
structure as arch
structural requirements are allowed to influence strongly the forms of buildings even though the structure itself is not necessarily exposed.
in the former the form generating possibilities are an active determinant of architectural form.
in the latter, the overall building form is influenced by the structural requirements but the architectural interest may lie elsewhere
structure as form generator/ structure as accepted
a form is adopted which is sensible structurally but the arch interest is not closely related to structural function.
prominent since italian ren
structure as accepted
a disregard of structural and constructional concerns in the determination of the form
core towers are clad with clay tile curtain wall construction- office floors have two-layer facade with double glazing for each layer.
1. both skins of the two layer facade around the offices are double glazing 2. flint glass is used to ensure a greater degree of transparency and to minimize color distortion in view out of the interior 3. inner skin of the double facade is a wood and glass construction with service ducts integrated into the apron panels beneath the window 4. the outer skin is a post and rail construction
high rise building in hanover
use of two layer facade
structural concept: main factors for the structural concept are
-transmission of wind and bracing loads
-transmission of dead loads
-transmission of live loads
site-cast concrete, two-way solid slabs transfer the dead and live loads to central, edge and corner columns.
lateral loads are transmitter through stiffening concrete core elements on the north-east and south-west corners of the building.
the 11-story tower, itself, amidst numerous classrooms and practice rooms, will host even more auditoria; a screening room, performance spaces- one for dance, one for theater- and what promises to be a spectacular “performance penthouse” at the top, with the building cracking open to the northwest like a giant yoked rectangular egg to create a rooftop terrace.
high rise building in hanover cont.