Read textbook Chapters 1-5 (pages 1-66) and prepare a synopsis (summary) of the contents about 1 page long for each Chapter (Chapters 1thru5 all in one WORD Document) and submit it to the Instructor by midnight Sunday. Please prepare your assignment in a single spaced MS WORD Document Format and it doesn't have to be in APA Style. You can use charts/figures/visuals to enhance your Assignment.
Chapter 1: Structure in Architecture
Chapter 1 introduces the concept and purpose of structure and compares natural with human made structures. The historical development of structures from the earliest Greek edifices through gothic cathedrals to modern skyscrapers are discussed. Utilitarian as well as aesthetic considerations are presented with the aid of several photographs. The need for close cooperation between the architect and the structural engineer is emphasized.
Summary of ideas presented in the chapter:
Structure is the external or internal armature that gives physical objects form and resistance to external forces.
Structure may be human-made or natural.
Built structures frequently imitate nature. Cooperation between architects and engineers is essential for successful structures; they complement each other. Multiple engineering disciplines are needed in a building project.
Architecture evolved and changed with the development of building materials from stone and wood to steel, concrete, and composites.
The advent of computers has simplified the design of complicated and daring forms.
Chapter 2: Building Loads and Codes
The chapter discusses the loads structures must resist. The difference between dead and live loads is explained and typical weights of building materials are tabulated as are most frequent design loads for various structures. Permissible loads are dictated by international as well as local building codes. Safety factors, the ratios between permissible and actually applied loads are also part of the codes. The intensity of snow and wind loads over the United States are shown on maps. Their destructive effects are presented. Stresses and elongations produced by temperature changes and by support settlements are discussed together with techniques to reduce their effects. The differences between static or slowly applied loads and dynamic loads are explained. Dynamic loads, such as impacts, vibrations and earthquakes are described. Resonance and fundamental periods of motion are introduced. A seismic intensity map for earthquake intensities over the US is presented. Various structural damping systems for dynamic load mitigation are also shown.
Summary of Ideas Presented in Chapter 2:
Structure is the load-carrying part of physical objects.
Loads are categorized as applied and hidden loads.
Applied loads are the ones the structure must support. These are as follows: Dead loads (the weights of building materials and of all permanent fixtures); live loads (occupancy loads and movable fixtures); wind, snow, and earthquake loads; as well as others, such as dynamic loads produced by machinery.
Hidden loads are produced by thermal environments and support settlements.
Building codes dictate the design values for each load category depending on the purpose of the building. The codes may also prescribe heights, and type of construction depending on locality.
Chapter 3: Structural Materials
Chapter 3 introduces the most frequently used materials of construction. The significant properties of wood, steel, aluminum, concrete, glass and plastics are described. Elasticity, plasticity and viscoelasticity, brittleness and strength of these materials are examined and compared. Mechanical constants, such as the Modulus of Elasticity, Yield strength and Ultimate strength are defined. The concept of stress (pressure) and strain are introduced, load-deformation and stress-strain diagrams are presented. Property changes as functions of temperature are discussed. The three basic stresses: tensile, compressive and shear are defined and the deformations produced by them are shown with the aid of figures and photographs. The materials most suitable to carry each of these stresses are discussed together with combinations of materials such as steel-reinforced concrete, fiber-reinforced glass and plastics and laminated wood.
Summary of Ideas Presented in Chapter 3
Materials of construction must carry loads without permanent deformation. They may be (1) elastic, within a certain range; (2) elastic-plastic; and (3) brittle.
Some materials are able to carry tensile and compressive loads equally well, while others can only be used with compressive loads.
Stress is defined as the force per unit area and strain as elongation per unit length. There are specific characteristic properties of yield point, yield stress, and ultimate strength for any given material.
Rigidity/flexibility of a material is quantified by the modulus of elasticity, defined as the ratio of stress to strain.
Chapter 4: Structural Requirements
Chapter 4 discusses the various requirements a structure must satisfy. All forces must be in linear equilibrium that is actions have to be opposed by reactions both horizontally and vertically. In addition moments producing rotations must also be equilibrated by opposing moments. Moments are defined as the products of forces and their distances form a fulcrum.
Structures must also be stable, they should not slide down a hill or topple over. Appropriate foundations are to be designed to prevent such problems. Examples are presented for these types catastrophes. Structural strength is also a requirement. The materials used for construction have to have adequate properties such as yield and ultimate strength with sufficient factors of safety to carry the applied loads. Most buildings need to satisfy certain functions and have to be constructed economically unless their purpose is only ornamental. Structures should also be aesthetically pleasing rather than eye-soars. While most structures may be designed using mathematical/theoretical or computer aided techniques, in some instances scaled models are used to verify their safety.
Summary of Ideas Presented in Chapter 4:
Structures must be in equilibrium. All forces acting on the structure must be balanced. All actions must have equal and opposite reactions.
Equilibrium is required for both linear forces and rotational actions.
The action of a force at a distance that generates rotation is known as amoment of a force. Understanding moment is at the root of all structural knowledge.
Structures have to be stable. They must not slide or overturn.
Structural elements should be designed so that stresses do not exceed the yield strength of their materials or stress limits dictated by the appropriate building codes.
All structures have a purpose, and they have to be designed to function properly to achieve it.
All structures are to be built within a predetermined budget. They have to satisfy economical requirements, whether a building or a monument.
Beauty is in the eye of the beholder. A structurally correct building usually satisfies aesthetic tastes.
With the aid of modern computers and engineering knowhow, anything can be designed; structurally optimum buildings do not always satisfy of requirements of economy and aesthetics.
Chapter 5: Basic States of Stress
Chapter 5 presents the basic states of stress encountered in structures. Simple tension,
Simple compression, Shear and Bending are discussed with the aid of figures and diagrams. When a component is being stretched it under goes a tension stress, its particles are pulled apart and the component elongates. The applied force divided by the cross-sectional area perpendicular to the applied force is defined as stress. The corresponding change in length divided by the un-stretched length is called strain. For an elastic material stress and strain are proportional: doubling the stress results in doubling the strain. The constant of proportionality is the Modulus of Elasticity. If the applied stress is great enough to reach the ultimate strength of the material, the component breaks. A compressed column undergoes compressive stress resulting in shortening. The definitions of compressive stress and compressive strain are analogous to those for tension. While a short column may break at the ultimate strength a long, slender column may suddenly bend out of shape, it buckles long before the ultimate strength is reached. The so-called buckling load depends not so much on the cross-sectional area but on the distribution of the material. This load is also a function of the column’s support conditions.
In addition to length change the thickness of a member also changes. In tension it becomes thinner and in compression thicker. The third basic stress, shear, is analogous to friction between two surfaces sliding past each other. Shearing takes place when a hole is punched. Shear stress is defined as the applied force divided by the cross-sectional area parallel to the force. Shear strain is not a change in length but a change in shape. When two equal and opposite vertical forces are applied to a square piece of material, the square is deformed into a rhombus. The right angles at the corners of the square become smaller (larger). This angle change is defined as shear strain. Shear stress and shear strain are also proportional to each other. Here the constant of proportionality is the Modulus of Rigidity. To maintain the required equilibrium of forces and moments, two equal and opposite forces must also be applied to the horizontal sides of the square element. The resulting shape change could also be accomplished by pulling and pushing on opposite corners of the element, hence shear is equivalent to tension and compression at 45 degrees to the shear forces. Torsion. i.e., twisting, produces shear stresses. A rectangular grid drawn on the surface of a cylinder deforms into rhombi, indicating shear. The last basic stress is bending stress. When a straight bar is bent into a curved shape, one surface is shortened and the opposite side extended. The two surfaces are in compression and tension. These stresses are greatest on the two opposite sides and diminish towards the middle. This intermediate surface is unstressed and is termed a Neutral Surface. Bending stresses are not governed as much by the cross-sectional area of the bar but by the distribution of material away from the neutral surface. The farther the material is from this surface the smaller the bending stresses. The behavior of such “beams” is discussed in detail in Chapter 7.
While shear and bending stresses have been described as separate types, it should be clear from the above that both may be resolved as only two basic stresses: tensile and compressive.
Summary of Ideas Presented in Chapter 5
The basic states of stress are tension, compression, bending, and shear. Tensile stresses pull material particles apart, while compression presses them together. Bending and shear change the shape of structural members.
Tensile stresses produce elongation of components, while compression results in shortening. Both stresses are defined as the applied force divided by the cross-sectional area of the member perpendicular to the force. In each case, the change in length is proportional to the applied stress and to the original length of the member and the strain is the percent change in length.
Under tension the length increases, and at the same time the thickness of a tensed component decreases. In compression, the shortening of length is accompanied with a widening of thickness. This phenomenon is referred to as the Poisson Effect.
Most metals are able to carry tensile and compressive loads within their elastic ranges. Brittle materials such as concrete, stone, and brick are capable of compressive loads only.
Tall, slender compressed columns may suddenly buckle as the applied load increases. The buckling load is proportional to the modulus of elasticity and to the distribution of material away from the centroid of the cross section: (Moment of Inertia will be discussed in Chapter 7) it is inversely proportional to the length of the column. Buckling load is also a function of end restraints and of lateral supports.
Shear produces sliding of materials parallel to the applied force. It distorts a square element into a rhombus. Shear stress is defined as the applied force divided by the cross-sectional area parallel to the force. Shear strain is the change of angle from a right angle to a skewed angle.
Shear is equivalent to tension and compression at 45 degrees from the shear stress.
When a cylindrical bar is twisted, squares drawn on its surface deform into rhombuses and indicate the presence of shear. Torsion is a special case of shear.
Simple bending produces curvature in straight elements. When a component is bent into an arc, the fibers nearer the center of curvature shorten and hence experience compression while the opposite side is elongated and is in tension. A surface between the two sides is unstressed.
Bending stresses are proportional to the depth of the beam and inversely proportional to the moment of inertia. The farther the amount of material is from the neutral surface the smaller the bending stress.