OBJ 3.2 Flashcards

Question

Structural tee concrete system

Answer 1

Pre-stressed ribs with a 2-inch topping slab integrally connected. Good for long spans. Can be either single or double tee.

Answer 2

Lightweight steel truss with parallel top and bottom chords and a triangulated web system between. Lightweight and efficient system that can be used for both long and short spans (depending on depth) that allow for ductwork to pass through.

Answer 3

Tributary area in structural engineering refers to the plan area of a building that loads onto a particular structural member. For example, the tributary area of a beam is half the distance to the next beam in each direction.

Answer 4

Influence area is the tributary area plus the area that will impact the load on a structural member.

Answer 5

A dynamic load in a building that occurs quickly. Examples include moving elevators or a vehicle hitting a structure. Building codes account for impact loads by adding a safety factor.

Answer 6

Can use the principles of statics to determine forces and reactions.

Answer 7

Cannot use the principles of statics to determine forces and reactions.

Answer 8

A measure of resistance to bending and buckling.

Answer 9

A vertical curve that is built into a beam to counteract the deflection imposed by any added dead load.

Answer 10

Normal cement used for most construction.

Answer 11

Normal cement, which is air entraining.

Answer 12

Moderate resistance to sulfate attack (used when in contact with water with high concentrations of sulfates).

Answer 13

Moderate resistance, air entraining.

Answer 14

High early strength (hardens more quickly; used when reduced curing time is required).

Answer 15

High early strength, air entraining.

Answer 16

Low heat of hydration (used in massive structures such as dams, where emitted heat might raise thetemperature of the concrete to damaging levels).

Answer 17

High resistance to sulfate attack (used when in contact with water with a high concentration of sulfates).

Answer 18

Admixtures are ingredients other than cement, aggregates, and water that are added to the mix to alter it in various ways.

Answer 19

Increase the workability of wet concrete, reduce freeze/thaw damage, and (when a lot is used) create very lightweight nonstructural concretes with thermal insulating properties.

Answer 20

Allow a reduction in the amount of mixing water whileretaining the same workability; results in a higher-strength concrete.

Answer 21

Organic compounds that transform a stiff concrete mix into one that flows freely into forms; used to help place concrete in challenging circumstances or to reduce the water content in a mix in order to increase its strength.

Answer 22

Concrete cures more rapidly.

Answer 23

Slow curing to allow more time to work with wet concrete.

Answer 24

A fine powder that is a waste product from coal-fired power plants. It increases concrete strength, decreases permeability, increases sulfate resistance, reduces temperature rise during curing, reduces mixing water requirements, and improves workability.

Answer 25

Byproduct of iron manufacturing that improves workability,increases strength, reduces permeability, reduces temperature rise during curing, and improves sulfate resistance.

Answer 26

Varicose natural/artificial material that reacts with calcium hydroxide in wet concrete to form cementing compounds.

Answer 27

Improve the plasticity of wet concrete to make it easier to place in forms and finishes.

Answer 28

Used to reduce rusting of rebar in structures that are exposed to road deicing salts or other corrosion-causing chemicals.

Answer 29

Short fibers of glass or steel added to a concrete mix to act as microreinforcers.

Answer 30

Allow concrete to cure at temperatures as low as 20°F.

Answer 31

Used to delay the curing reaction in concrete for up to seven days.

Answer 32

Dyes and pigments used to alter the color of concrete.

Answer 33

A rocklike material produced by mixing coarse and fine aggregates, portland cement, and water, and by allowing the mixture to harden.

Answer 34

Gravel or crushed rock.

Answer 35

Chemical reaction between water and cement that creates heat.

Answer 36

A product of lime, iron, silica, and alumina that is crushed, ground, proportioned, and blended and then sent through a kiln, cooled, and pulverized to a powder.

Answer 37

A mineral that expands upon being heated; used in the expanded state for heat/sound insulation and fireproofing.

Answer 38

A form of obsidian formed by cracking of cooling volcanic glass; used as insulation.

Answer 39

A steel alloy typically used for the production of wide flange shapes. A992 steel has an Fy of 50 ksi and an Fu of 65 ksi.

Answer 40

Stress is the intensity of a force. It is force per unit area, or f = P/A, where f is stress, P is force, and A is cross-sectional area. There are two kinds of stresses: normal (perpendicular) and tangential. Shearing stresses are tangential and axial stresses are normal. Bending stresses result in both normal and tangential stresses.

Answer 41

Strain is the physical change in a body from the result of stress. Under stress, the size or shape of the body changes. Tensile stress strains a body by elongation and compressive stress shortens a body. Strain has no units because it is a ratio.

Answer 42

Lateral forces such as wind and seismic loads act on entire buildings, causing them to want to turn over. Buildings must resist the tendency to overturn due to the moment caused by the lateral force.

Answer 43

Lateral or story drift is the amount of horizontal displacement or sway in a building due to lateral loading such as wind or seismic activity.

Answer 44

A telescoping, adjustable, thin-walled round steel column. Often found in basements or crawl spaces of homes. Can be temporary or filled with concrete to remain in place.

Answer 45

Buildings that are multiple stories of wood over an elevated concrete podium or deck. An example is a four-story wood-framed apartment building over a two-story concrete parking structure.

Answer 46

Estimate depth at 1/18th of their span.

Answer 47

2 x 6 = 9 feet; 2 x 8 = 11 feet; 2 x 10 = 14 feet | 2 x 12 = 17 feet (for estimating only).

Answer 48

2 x 4 = 7 feet; 2 x 6 = 10 feet; 2 x 8 = 14 feet | 2 x 10 = 17 feet (for estimating only).

Answer 49

Cross laminated timber. An engineered wood building system of solid, prefabricated structural panels made from lumber that is stacked in alternating directions and bonded with adhesives. They are lightweight, structurally efficient, and gaining in popularity in the United States.

Answer 50

A closed structural system with compression struts within a network of tension tendons.

Answer 51

Control joints are placed every 5 feet, and expansion joints are placed every 20 feet.

Answer 52

A 1 percent slope minimum.

Answer 53

The diameter is 3/8 inches. Generally, the number size is always the numerator in a ?/8-inch fraction because rebar comes in 1/8 of an inch increments.

Answer 54

This is the type of steel and will always be the third marking down on the rebar. S = carbon steel, W = low alloy steel, SS = stainless steel, R = rail steel, A = axle steel, CS = low-carbon chromium.

Answer 55

Pre-stressed concrete is constructed with pre-tensioned or post-tensioned cables.

Answer 56

Gravity (the building itself, its contents, snow, ice, and water on the roof); wind, seismic, and hydraulic pressure (groundwater); soil pressure; thermal changes; shrinkage within building materials (similar to thermal changes); internal forces (for example, warping or loosening of the building components and settling); and vibrations (from machinery, for example).

Answer 57

These forces are not always apparent to the building designer, but they must be considered.

Answer 58

Anything that is not a permanent load in a building. Includes people, contents, snow, ice, and wind. Live loads are usually dynamic.

Answer 59

The weight of the permanent parts of a building. They are static loads that are relatively constant.

Answer 60

A force that does not change in magnitude or position. They are relatively independent of time. Dead loads are static forces. Static forces have mass and potential energy.

Answer 61

A force that changes in magnitude or position over time. Live loads are dynamic forces. Dynamic forces have mass and inertia.

Answer 62

Loads that are concentrated; for example, a column on a footing is a point load. Also called concentrated load.

Answer 63

Loads that are dispersed across a structure; for example, the dead load of a roof transferred to a bearing wall.

Answer 64

Randomly dispersed live loads.

Answer 65

A load imposed on a column that is located a short distance away from the centroid.

Answer 66

Generally, it is not required to design for both earthquakes and high wind velocities occurring simultaneously, nor is it required to design for high wind velocities blowing from more than one direction simultaneously.

Answer 67

A structural member must have sufficient strength and stiffness to resist displacement, deformation, and fracturing. A reaction is the term given to these forces of a structural member that resists the forces acting on it. A reactive force must be equal to the force acting on it in magnitude and opposite in sense (direction), leading to a state of static equilibrium.

Answer 68

Shear forces are those that pull a body apart through an internal, parallel, opposing, or sliding action. Scissors cutting paper is a shear force.

Answer 69

Occurs at column footings and in slabs supported by columns. Punching shear is a localized force characterized by the column’s tendency to want to “punch through” the footing or slab.

Answer 70

When a force acts on a body, causing it to want to rotate. For example, a cantilever beam that is supported at one end must resist rotational force. Rotational force is also called moment and is a function of force times distance.

Answer 71

Any forces applied to a structure from outside the system. Dead loads, live loads, uniform loads, point loads, and moments are all external forces. External forces cause internal forces.

Answer 72

A force generated within a structure in response to resisting external forces. Includes normal (axial) forces, shear forces, and bending moments.

Answer 73

Appearance, weight, fire resistance, thermal properties of expansion and contraction, durability to weathering and wear, availability, cost, and constructability.

Answer 74

Any force applied to a body.

Answer 75

A two-way truss-like system that can span large areas with few supports.

Answer 76

A membrane roof is a thin fabric sheet that cannot resist compression, bending, or shear but can resist tension. It is a “tent” structure. Examples: Munich Olympic Stadium and Denver International Airport.

Answer 77

When a membrane roof is supported by air pressure. Commonly used for sports arenas.

Answer 78

Assemblies of flat plates that are inclined and joined to create a roof structure. Eliminates the need for beams.

Answer 79

Long-span.

Answer 80

Close to equal.

Answer 81

Manufactured panels of glued and nailed plywood skins to both sides of a wood frame, resulting in a unit that performs like an I-beam. Not necessarily insulated.

Answer 82

Sandwich panels and unfaced panels. Skins of panels resist tension and compression, whereas the wood frame or core resists shear and prevents buckling of skins.

Answer 83

Rigid-foam panels faced with two structural grade skins; usually made of oriented strand board or plywood.

Answer 84

Looks like panels of stick framing with thermal insulation between the members, instead of blanket insulation.

Answer 85

Slabs combine desirable characteristics of cast-in-place precast concrete. The panels act as permanent forms for the field-placed reinforcing and cast-in-place topping. The underside is smooth and can be left exposed.

Answer 86

Include auger cast grout, bored and socketed, bored concrete, drilled caissons, drilled concrete piers and shafts, and drilled micropiles. Conditions that make bored piles advantageous include: cohesive soils, obstructions that can be tolerated with the right size drill, and dense reliable bearing surface.

Answer 87

Include concrete, steel, timber, and composite piles that are driven into the ground with a mechanical hammer. Conditions that make driven piles advantageous include cohesionless soils with few boulders.

Answer 88

This element is used when more than one deep foundation element is required to resist gravity and lateral loads to distribute the loads from a single point column to multiple foundation elements.

Answer 89

Design strength is the assumed value of strength for concrete and the yield stress of steel. For concrete, the maximum compressive strength is reached after curing for 28 days and is typically in the range of 3,000–6,000 psi.

Answer 90

Horizontal. Wood is stronger perpendicularly, or across the grain, rather than parallel to the grain direction.

Answer 91

Lumber is wood that has been milled and is ready to be used as a construction member. Timber is standing or felled trees that have yet to be shaped. Rough stock wood is also referred to as timber. Structural timber is timber machined for use in structural applications and is at least 5 inches or greater in the least nominal direction.

Answer 92

Carbon. It is important to note that, with an increase in the carbon content of steel, ductility and welding capabilities are reduced.

Answer 93

False. The cost of the entire building must be considered, because savings in designing with more efficient structural members can mean deeper sections, which increases the floor-to-floor and overall building height. The resulting increases in all the extra costs of the building in the stairs, elevators, cladding, and MEP systems may offset the cost savings of the structural sections. The most cost-efficient structural system is often one that produces a major cost savings of another system.

Answer 94

- Faster erection at the site - Economy of formwork - Higher quality can be achieved in the factory, including tighter dimensions, a more uniform look, and higher strengths through pre-stressing - Allows shortcuts in design efforts by using standardized components

Answer 95

- Handling and transporting is burdensome - Costly - Connections (probably the single biggest disadvantage) - Coordination with other systems, such as MEP systems - Lack of performance during seismic events

Answer 96

Weight reduction due to the form’s response to the development of forces.

OBJ 3.2 Flashcards

(125 cards)