Structural Forms Flashcards
(137 cards)
1
Q
What is the core concept behind the Pantheon’s dome?
A
A large concrete dome with an oculus, showcasing ancient mastery of structural engineering.
2
Q
What does a structural system unify according to the definition of a structure?
A
Form, materials, and forces.
3
Q
What are the three key criteria that structures must satisfy according to structural engineering principles?
A
Strength to prevent breaking, stability to prevent collapse, and stiffness to prevent excessive deformation.
4
Q
What are structural forms dictated by?
A
Function and the need to redirect forces in equilibrium.
5
Q
What are the main tools used in conceptual structural design?
A
Sketches, mathematics, structural analysis software, research, experience, and case studies.
6
Q
What does ‘stability’ prevent in a structure?
A
Collapse.
7
Q
What is the significance of understanding load assessment and geometry in structural analysis?
A
They are essential for modelling the structure’s behaviour and ensuring its safety and functionality.
8
Q
What are the three ‘S’s in structural design?
A
Strength, stability, and stiffness.
9
Q
What are the main functions of a structure’s interior and exterior design?
A
Interior supports activities and aesthetics; exterior provides enclosure, protection, and visual identity.
10
Q
What is the primary function of a structure in engineering?
A
To transmit forces and discharge them safely to the ground through the flow of forces.
11
Q
What does ‘stiffness’ prevent in a structure?
A
Excessive deformation or excessive movement under load.
12
Q
What is the function of a structure?
A
To transmit forces and discharge them safely to the earth.
13
Q
How do structures transmit and discharge forces?
A
They transfer forces through structural elements and discharge them to the earth, following principles of mechanics and equilibrium.
14
Q
What does the term ‘stability’ refer to in structural design?
A
The ability of a structure to resist collapse under applied loads.
15
Q
What is the significance of the ‘three S’s’ in structural design?
A
Strength, stability, and stiffness, which are essential for a structure’s performance.
16
Q
What is the significance of the Oceanographic Valencia structure?
A
It exemplifies innovative structural design using a steel-fibre reinforced concrete thin-shell.
17
Q
What are some typical questions addressed during structural design?
A
Form, elements, sizes, materials, connection strength, and how elements work together.
18
Q
What tools are used in conceptual structural design?
A
Sketches, math, structural analysis software, research, experience, and case studies.
19
Q
What is a superstructure?
A
The part of a building above the substructure, designed to enclose space and distribute loads.
20
Q
What does ‘stiffness’ prevent in a structure?
A
Excessive deformation.
21
Q
What are common materials used in historical and modern domes?
A
Roman concrete, ferro-cement, timber, and glulam.
22
Q
What is the primary purpose of a structure?
A
To support and transmit applied loads safely to the ground without exceeding material stresses.
23
Q
What are the main types of loads acting on structures as shown in the cross-section diagram?
A
Occupancy, snow, water, live, dead, static, and variable loads.
24
Q
What is the significance of the Oceanographic Valencia structure?
A
It exemplifies a thin-shell structure that combines structural efficiency with aesthetic design.
25
How are structural forms dictated during design?
By the function and the need to redirect forces in different directions through various states of equilibrium.
26
How does the Millennium Dome exemplify the integration of natural principles into structural design?
It uses flat fabric panels supported by a cable net, reminiscent of natural structures combining beauty and strength.
27
What are structural forms mathematically described by?
The principles of mechanics and equilibrium.
28
What are examples of structural systems used in famous structures?
Ferro-cement dome of Palazzetto dello Sport, Roman concrete of the Pantheon, timber in Rimini Exhibition Centre.
29
Describe the relationship between actions and effects in a structure as depicted in the diagram.
Actions such as loads and thermal changes cause effects like displacements, strains, and stresses.
30
What are the three key criteria structures must satisfy according to structural engineering principles?
Strength, stability, and stiffness.
31
What are the typical questions addressed during structural design?
Form, elements, fitting, sizing, material grade, and connection strength.
32
How does the Millennium Dome exemplify natural principles in structural design?
It uses a fabric-supported cable net system reminiscent of natural structures to combine beauty and structural integrity.
33
What is the primary goal in the initial qualitative phase of structural analysis?
Concept generation and establishing proportions of structural elements based on simple rules.
34
Why is understanding load assessment and geometry crucial in structural analysis?
They are essential for modelling the structure, determining reactive and internal forces, and ensuring member adequacy.
35
What is the process called where forces are transferred and discharged to the earth in a structure?
Flow of forces.
36
What does the diagram of a beam supported by two pillars illustrate regarding forces?
Distribution of tension and compression forces within the beam.
37
What are common materials used in historical and modern domes?
Roman concrete, ferro-cement, timber, and steel-fibre reinforced concrete.
38
What is the role of the flow of forces in structural behaviour?
It describes how forces are transmitted through the structure and discharged to the ground.
39
Why are structural forms mathematically described?
To ensure they satisfy equilibrium conditions and effectively redirect forces.
40
Define 'superstructure' in structural terminology.
Everything above the substructure, designed to enclose and divide space and spread loads to the substructure.
41
What is the first qualitative activity in the structural design process?
Concept generation and applying simple rules of thumb to establish proportions of structural elements.
42
Why is concrete reinforced with steel in beams?
Because concrete's tensile strength is too weak to resist bending stresses, so steel reinforcement prevents cracking.
43
Why is considering load combinations important in structural design?
To ensure safety and economy by designing for the most damaging combination of loads that may act simultaneously.
44
What is a gravity load?
A vertical load including permanent and variable loads such as dead weight and occupancy or snow loads.
45
Describe the steps to sketch a load path.
Draw external load vectors, trace the load from application to supports, sketch transfer elements, and ensure a load transfer system exists.
46
How are loads classified in Eurocode?
As permanent actions (G), variable actions (Q), and accidental actions (A).
47
Give examples of permanent, variable, and accidental loads.
Permanent: self-weight; Variable: wind or snow; Accidental: impact from vehicles or explosions.
48
What are the three fundamental qualities of a structure according to Vitruvius and Eurocode?
Firmitas (robustness and safety), Utilitas (serviceability and functionality), Venustas (elegance and beauty).
49
What is a cantilever beam?
A projecting beam supported at only one fixed end.
50
What is an overhanging beam?
A beam extending beyond one of its supports.
51
What is the load path in structural analysis?
The route by which loads are transmitted from their application point to the ground or supports.
52
What is the primary force acting on a beam that causes bending?
Transverse forces applied perpendicular to the beam's longest axis.
53
How is a gravity load transferred in a building?
From slabs to columns or walls, then to foundations, and finally to the supporting soil.
54
What are Eurocodes?
A set of common technical rules for designing buildings and civil engineering works in the EU to standardize practices and replace national standards.
55
What characterizes a simply supported beam?
A beam resting on supports at both ends, free to rotate.
56
What primarily influences the design loads on a building?
The building's intended use, configuration, and location.
57
What are the main types of support conditions for beams?
Fixed on a wall, roller support, hinge support, and overhanging support.
58
How does the maximum deflection of a simply supported beam change when the length doubles?
It increases by a factor of 8.
59
Give an example of a fixed support in construction.
Beam ends bolted to a concrete shear wall.
60
What is a simply supported beam?
A beam resting on a hinge support at one end and a roller support at the other, subjected to vertical loads.
61
Where is the neutral axis located in a beam under bending?
In the mid-depth of the beam, experiencing no stress, tension, or compression.
62
Why are steel rebars added to concrete beams?
To control cracks and resist tensile stresses, since concrete is weak under tension.
63
Give an example of a cantilever beam in construction.
Signboards, lighting columns, or stadium canopies.
64
What deformation shape occurs when an upward transverse load is applied to a beam?
Hugging, which resembles a dome, with the top face under tension and the bottom face under compression.
65
What is the formula for maximum deflection of a simply supported beam under a mid-span point load?
D_max = (P L^3) / (48 E I).
66
What deformation shape occurs when a downward transverse load is applied to a beam?
Sagging, which resembles a bowl.
67
What is a support in structural engineering?
A connection between a structural member and a rigid body.
68
What are the four main support conditions?
Fixed support, pin support (hinge), roller support, and free support.
69
How can displacement at the free end of an overhanging beam be limited?
By replacing the hinge support with a fixed support at the support end.
70
How does a pin support (hinge) support a beam?
Allows rotation but restricts horizontal and vertical translation.
71
What is an overhanging beam?
A simple beam extending beyond one support.
72
What does a roller support allow and restrict?
Allows rotation and horizontal movement, but restricts vertical displacement.
73
In a simply supported beam subjected to downward load, which fibres are under tension and compression?
The top fibre is under compression, and the bottom fibre is under tension.
74
What is bending in structural members?
The tendency of a member to bow as a result of an applied load perpendicular to its longitudinal axis.
75
What is a cantilever beam?
A beam fixed at one end and free at the other, which can be displaced and rotated at the free end.
76
What are the characteristics of a fixed support?
No rotation, no horizontal or vertical displacement allowed.
77
What are beam members or flexural members characterized by?
They have a length significantly greater than their other two dimensions and are idealized by a line.
78
What is the purpose of elevator shafts in structural stability?
They act as vertical structural elements that resist horizontal loads and carry vertical loads, containing the elevator machinery.
79
Why are columns considered critical in structural systems?
Because failure of a column can cause the entire structure to collapse, unlike beams which cause only local failure.
80
Explain the concept of triangulation in structural stability.
Breaking down a frame into triangles, which are inherently stable geometric forms, to improve overall stability.
81
What are shear walls and how do they function?
Shear walls are planar surfaces that resist lateral forces by changing shape and transmitting these forces to the ground, extending from foundation to roof.
82
List key advantages of frame systems in high-rise construction.
Optimum use of floor space, rapid construction, economic efficiency, and suitability for steel or reinforced concrete.
83
Define a bay in structural terms.
The distance between two adjacent frames in a building structure.
84
How do rigid joints contribute to lateral stability?
They create rigid connections that transmit bending moments and share deflections across the structure, enhancing stability against horizontal loads.
85
What is the primary function of slabs in concrete frame structures?
To carry loads primarily by flexure, supporting vertical loads and transferring horizontal forces to beams.
86
What components make up a portal frame?
Commercial-grade steel columns and rafter beams connected to form a single frame.
87
What is the purpose of foundations in a building?
To transmit loads from columns and walls to the solid ground safely.
88
What is a structural frame system in building design?
A framework of beams and columns that gives shape and support to a building, and is the most common structural system.
89
What role do beams play in a structural system?
Beams carry loads from slabs and direct loads from masonry walls and self-weight, supporting them via flexural resistance.
90
Differentiate between one-way and two-way slabs.
One-way slabs are supported by beams on two sides with reinforcement in one direction; two-way slabs are supported on all four sides with reinforcement in both directions.
91
What shape does a funicular cable assume when unloaded, and what determines this shape?
The shape is a catenary, determined by the cable's self-weight, representing the natural form under its own weight.
92
What are the main components of a truss system?
Ties (in tension) and struts (in compression), arranged in pin-connected triangles.
93
How does the tensile force in a cable relate to reaction components?
The tensile force in a cable always equals the resultant of the vertical and horizontal reaction components.
94
What is the main idea behind inverting the shape of a flexible cable under load?
Inverting the shape yields a form that carries the load by axial compression only, useful in arch design.
95
What are the main components of a truss system?
Ties (in tension) and struts (in compression), arranged in pin-connected triangles.
96
How does the horizontal thrust reaction in a cable change as the slope approaches horizontal?
The horizontal thrust reaction increases dramatically as the slope of the cable approaches horizontal.
97
How does the horizontal thrust reaction in a cable change as the slope approaches horizontal?
The horizontal thrust reaction increases dramatically as the slope approaches horizontal.
98
What is a truss and what is its main structural principle?
A truss is a framework of members arranged in triangles, supporting loads primarily through tension and compression in pin-connected members.
99
What is the primary structural behaviour of arches in terms of support reactions?
Arches exert support reactions that vary inversely with their rise (depth), supporting loads mainly in compression.
100
What is the main idea behind inverting the shape of a flexible cable under load?
The inverted shape carries the load primarily through axial compression, similar to an arch.
101
What is the fundamental structural behaviour shared by cables and arches in funicular systems?
Cables support loads in tension, while arches support loads in compression, sharing the characteristic of supporting loads through their primary stress mode.
102
What shape does a funicular cable assume when unloaded, and what determines this shape?
The catenary shape, which is determined by the self-weight of the cable.
103
What is the significance of the Vierendeel girder in bridge design?
It omits sloping ties or struts and uses rigid connections, transmitting internal bending moments at joints.
104
What is the primary difference in force support between cables and arches?
Cables support loads in tension, while arches support loads in compression.
105
What is the primary structural behaviour shared by cables and arches in funicular systems?
Cables support loads in tension, while arches support loads in compression, both relying on their shape to carry forces efficiently.
106
In a system with a suspended climber weighing 75 kg, what forces are calculated in the cable?
The forces in the cable on each side of the climber are calculated using equilibrium equations and depend on the angles of the cable segments.
107
What remains constant in a cable's reaction regardless of slope?
The vertical reaction remains constant and is equal to the vertical load.
108
In a system with a suspended climber weighing 75 kg, what forces are calculated in the cable?
The forces in the cable are determined using equilibrium equations, resulting in forces F_AB and F_AC calculated via trigonometry based on the angles.
109
Why are triangles used in truss design?
Triangles are the only stable polygon with pin connections, providing a rigid, stable structure.
110
What is the significance of the Vierendeel girder in bridge design?
Vierendeel girders use rigid joints and internal bending moments, omitting sloping ties or struts, allowing for rectangular openings.
111
What is the primary difference in force support between cables and arches?
Cables support loads through tension, while arches support loads through compression.
112
Why are triangles used in truss design?
Triangles provide inherent stability and are the only polygon with an inherently stable shape when hinged.
113
How does the tensile force in a cable relate to the reaction components?
The tensile force in a cable equals the resultant of the vertical and horizontal reaction components at its supports.
114
What remains constant in a cable's reaction regardless of slope?
The vertical reaction component remains the same regardless of the cable's slope and equals the vertical load.
115
What is a truss and what is its main structural principle?
A truss is a framework of interconnected members, typically arranged in triangles, that supports loads mainly through tension and compression.
116
What is the behaviour of diagonal members in a simple truss subjected to vertical load at a joint?
They typically act as tensile or compressive members depending on loading, with diagonals often in tension in uniform loading cases.
117
Why are pin connections used in truss systems?
Because they allow elements to rotate freely, making the elements axial with zero bending moment resistance.
118
How does changing the loading condition affect the forces in the diagonal members?
Different loads can cause diagonal members to experience compression or tension, potentially leading to instability if cables are used.
119
What is the primary geometric shape that provides stability in truss structures?
Triangles, as they are the most stable shape even with pin connections.
120
What material is suitable for diagonal members under tension in a Pratt truss?
Ropes or cables, as they are effective in tension but have zero stiffness in compression.
121
What are the two types of axial elements in trusses?
Ties under tension and struts under compression.
122
What is a key difference between normal trusses and Vierendeel trusses?
Normal trusses use pinned connections and are primarily axial, while Vierendeel trusses have rigid connections that transfer bending moments.
123
What is qualitative analysis in truss evaluation?
A method to determine whether members are under tension, compression, or zero force based on deformation and removal of members.
124
What is a truss system?
A structural system used to bridge large voids in buildings or across wide bays and valleys, typically composed of connected triangles for stability.
125
What is the primary function of triangulation in truss structures?
Triangulation stabilizes the structure by ensuring that all members are either in tension or compression, preventing deformation.
126
What is the significance of the loading condition in choosing materials for truss elements?
Loading conditions determine whether elements are under tension or compression, influencing whether materials like cables or struts are appropriate.
127
What is the main limitation of using cables for interior vertical elements in truss systems?
Cables cannot resist compression, so if an interior vertical element under load becomes compressive, the cable will buckle and the structure may become unstable.
128
What is structural idealization in the context of truss modelling?
A process of simplifying a physical structure by assuming pin connections and supports for computational analysis.
129
Why are crossed cables recommended for all diagonal elements in certain truss designs?
Crossed cables are recommended because they can handle tension effectively, which helps prevent instability under specific loading conditions.
130
How are loads typically applied in a truss system?
At the pin connections, causing members to experience tension or compression.
131
In qualitative analysis, what does removing a member help determine?
The role of that member in carrying load and whether it experiences tension, compression, or zero force.
132
How does a change in load distribution impact the forces in the diagonal members of a truss?
Different load distributions can switch diagonal members from tension to compression or vice versa, potentially causing buckling or instability if improperly designed.
133
What distinguishes a Vierendeel truss from a normal truss?
Vierendeel trusses use rigid connections and rectangular frames without diagonal members, allowing transfer of bending moments, unlike normal trusses which use pinned connections and triangular frames.
134
How does qualitative analysis determine whether a truss member is in tension, compression, or zero force?
It involves removing members and observing deformations or stability changes; if a member's removal causes displacement, it carries force; if not, it may be zero force.
135
In the context of truss analysis, what is meant by 'axial members'?
Axial members are structural elements that primarily carry tension or compression loads along their length, with no bending resistance.
136
Why are rigid connections used in a Vierendeel truss?
Rigid connections are used to resist bending moments and maintain stability in the absence of diagonal members.
137
What is the structural role of vertical interior elements in an over-trust configuration under uniform load?
They are under tension, and their proper function depends on the load condition; they may need to be cables if under tension.
