Concrete and Structural Frames
Concrete Work
1. Define cement and the function of the paste.
2. Why is it desirable to use a maximum amount of aggregate when making concrete?
3. List the 4 classifications of aggregate to produce a unit density of 135 – 160 lb/cft.
4. List 3 basic types of concrete based upon the unit density and 2 ingredients of each.
5. What does the largest size of course aggregate depend upon – list 3?
6. Describe the differences between the 2 different classes of natural aggregates.
7. Briefly describe the 8 different quality tests conducted on aggregate.
8. What is the chemical reaction that produces cement?
9. What are the basic raw materials for portland cement?
10. What are the 5 basic types of portland cement – describe?
11. List 5 important properties of concrete mix design.
12. How is plasticity or flowability of the concrete mix measured?
13. What does the water to cement ratio mean?
14. Why are concrete admixtures added to concrete?
15. Briefly describe 7 admixtures and their purpose.
16. Why are the slump test and compression test conducted?
17. How must the subgrade be prepared before placing concrete?
18. What determines the amount of time required for mixing concrete?
19. List 2 concrete mixers.
20. List 5 types of equipment used for placing concrete.
21. Briefly describe the conditions for placing concrete.
22. What is hot concrete and why is it used?
Concrete Answers
1. Cement: the product of a combination of Portland cement and water paste with some type of AGGREGATE. The paste surrounds the aggregate particles, as it sets, binds them solidly together – forming a dense concrete – the paste fills the voids between the particles of the aggregate.
2. Cement is up to 10 times more expensive than aggregates, and Cement paste tends to shrink while setting and curing – the use of more paste than is necessary results in a more expensive concrete and produces excessive shrinking.
3. Sand, Gravel, Crushed stone (natural aggregates), and Air-cooled blast furnace slag
4. Lightweight Concrete (85-115 lb/cu ft) – use expanded shale, slate, clay, and slag, Nonstructural insulating concrete (15-90 lb/cu ft) – use vermiculite, perlite, pumice, scoria, and diatomite
Heavyweight concrete (189 – 380 lb/cu ft) – use hematite, barite, limonite, magnetite, steel punchings, and steel shot
5. The size of the unit being poured, Whether it is reinforced, and The spacing of the reinforcement.
6. FINE aggregate (F.A.) – material < 1/4 in. diameter and COURSE aggregate (C.A.) – material 3/8-3 in.
7.
Soundness – to ensure that coarse aggregate is free of weak or laminated particles, soft and porous particles, or bits of shale.
Cleanliness – to test the presence of fine material – too much means an increase in surface area to cover with paste.
Silt Test – test for very fine material – water in a jar
Colorimetric – test for the presence of fine organic material – which would retard concrete setting
Gradation – particle size – fill voids with particles not air – reduce voids by improving gradation
Moisture Content – used to determine if adjustments in the addition of water are required,
Specific Gravity and Particle Shape and Surface Texture
8. ‘hydration’
Chapter 8,9,10 Part 3
15. To ensure continuity within the structural members in the building frame.
There are 3 types of splices available:
Welded – not recommended for normal reinforcing bars – large amount of heat required in welding process affecting the properties of the bar
Mechanical – used where butt-type spliced are needed (metal sleeve)
Lap – most common – simple – considered tension or compression lap splices.
16. The longitudinal bars that run the length of the columns, and The lateral reinforcing that encloses the longitudinal steel.
17. To provide tensile strength to that part of the beam cross-section that undergoes tension due to an applied load, To add compression strength to the portion of the beam cross section that is in compression, and To provide additional shear strength to the beam cross section.
18. Normally reinforced, Pre-stressed (placed under tension) pre-tensioned, and Pre-stressed post-tensioned.
19. Advantages of Factory Type – freedom of design, high degree of quality control of ingredients, wide variety of shapes, sizes and configuration, finishing completed, rapid enclosure of building, and pre-insulated (energy efficient).
Concrete answer from 9-15
9. Raw Materials: Lime, Silica, Alumina, and Iron.
10.
Type I(10) or normal cement: – general purpose
Type II(20) or moderate cement – protection against sulfate attack and large mass concrete structures.
Type III (30) or high early strength:-high strengths in a very short time
Type IV (40) or low heat of hydration – to maintain low heat requirements – massive structures – dams
Type V (50) or sulfate resisting – protect against severe sulfate attack – foundations
11. Compressive strength, Consistency, Durability, Resistance to freeze-thaw action, and Ease of pouring and finishing
12. Plasticity or Flowability of the mix – slump test.
13. Water:Cement ratio – as the amount of water increases per lb of cement, the strength of the concrete decreases.
14. Concrete Admixtures – increase durability, life span – freezing-thaw cycles
15.
Accelerators, chlorine type and non-chlorine type – improve the setting time and early strength gain
Air-entraining admixtures – improve the durability and workability of the concrete mix.
Colouring agents – provide different colours
Pumping additives – improve the pumpability
Retarders – increase the setting time by slowing the initial set of the concrete.
Super-plasticizers – increase concrete flow and retard the setting time – less water needed
Water reducers – reduce the quantity of water required
Concrete Answers 16-22
16. Slump – to ensure the concrete has the flowability required for placing – sheet metal cone and tamping rod
Compression – to determine the quality of the cured concrete and to ensure that it meets the design specs after being cured for a certain length of time
17.
Before placement – the subgrade must be properly prepared, and forms and reinforcing must be erected according to specifications
18. Volume and stiffness of the mix, The size of the C.A. and the fines of the sand, and The type of mixer being used
19. Drum Mixer – rotating drum with stationary blades fixed on the inside. And Countercurrent Mixer – horizontally revolving pan, into which is suspended one or more vertical, 3-paddle mixing tools, offset from the center of the pan.
20. Wheelbarrows and buggies, Chutes, Buckets, Belt Conveyors, Pumps
21. Maintain fresh concrete with 50-90 F, Concrete must be placed as nearly as possible to its final position, Should not place in large quantities in one position and allow to flow or be worked over a long distance in the form – mortar will tend to flow ahead of the coarser materials, thus causing stone pockets and sloping work planes, In forms – never allow concrete to be drop freely more than 1m
22. Mixed in a central plant for used in producing reinforced precast products or for concrete blocks – can be placed at temperatures up to 175 F.
Why use hot concrete? It sets and gains early strength much more rapidly than concrete placed at conventional temperature
Chapter 8,9,10 questions
Structural Steel Frame
20. List 7 reasons for using steel in structural design.
21. Describe the uses and differences for the 2 basic styles of hot-rolled I-shaped sections.
22. List the 2 types of angles.
23. What are cold-formed structural shapes normally used for?
24. Describe 2 considerations in designing steel frames.
25. Describe the 2 basic categories of steel frames.
26. Describe the difference between pin-type and moment resisting type connections.
27. List 7 major components in steel frames.
28. What are the 2 most common methods of connecting steel frames?
29. How are structural bolts classified?
30. Describe the 3 types of bolts.
31. What are the 2 types of bolt connections?
32. Describe where the 2 types of welds are used.
Answers Part 1 Chapter 8,9,10
1.
Braced Frames:
When the lateral displacement has been prevented and any lateral movement that occurs is small. The connections between the structural members are normally designed to resist gravity loads.
UNbraced Frames:
Lateral stability is developed through the rigidity of the frame members and the ability of the connections to resist rotation.
Chapter 8,9,10 questions
Structural Timber Frame
1. Describe the differences between the 2 classifications of timber frames.
2. List 6 basic components of timber frame buildings.
3. What does the size of the components depend upon – list 6?
4. What is the function of the connectors?
5. List 7 types of connectors.
6. Describe the purpose and difference between shear plates and split-ring connectors.
7. Describe the 3 categories of wall sections.
Reinforced Concrete Frame
8. Why is steel added to concrete structural frames?
9. What determines the section size and load resistance?
10. Briefly describe the 2 options for reinforced concrete sections.
11. What are the 3 common grades of reinforcing bars?
12. What does the grade of the bar designate?
13. How is the size of the bar designated?
14. Describe the 2 important factors to be considered in the location of the bars in a concrete section.
15. Why would reinforcing bars be spliced and describe the 3 types of splices?
16. What does column reinforcement consist of?
17. What are the 3 purposes for beam reinforcement?
18. List the 3 types of precast structural members.
19. What are the advantages of the factory type of architectural precast concrete?
Answers Part 2 Chapter 8,9,10
2.
Columns, Beams, Purlins, Trusses, The connectors that are required, and Decking or planking.
3. The load, The span of girders, The span of beams, The span of planks, The unsupported height of columns, and The species and grade of timber being used.
4. Connectors are required to transfer the load from one member to another without producing any adverse effects on the connected member
5. T-straps, U-Straps, Wood or steel side plates, Angles, Saddles, Bolts, Lag screws
6.
Shear plates – to prevent deformation of the timber due to the forces in the bolt by distributing the forces over a much larger area of the wood.
Split-ring connectors – same as shear plates but the bolt is not used in the transfer of load from one member to another.
7. Load bearing walls – support gravity loads due to floors and roofs
Non-load-bearing walls or partitions – serve to divide large areas into smaller areas
Shear walls – resist horizontal loads (wind) and act as a method of bracing within a building frame.
Chapter 8,9,10 Part 3 Answers
8. Steel – the number of rods or bars and the location in the concrete are based upon frame analysis conducted by a structural designer.
9. The tensile strength of the bars, and the 28-day compressive strength of the concrete mix determine the section size and its load resistance.
10.
Cast-in-Place – connections designed to develop resistance to rotation and adds stability to the frame.
Precast – connections are pin type – lateral stability of the frame must be transferred through the connection into portions of the frame that will act as bracing.
11. 40, 50, 60
12. Grade designates the yield strength of the material used, ex. grade 40 bar has a yield strength of 40 000 PSi.
13. The size is designated by a number that represents the number of 1/8 of an inch of bar diameter.
14. Sufficient cover must be provided to protect the reinforcing steel from the environment (ex. Concrete cast against earth cover = 3 in.), and Proper spacing must be provided between the bars to ensure the concrete flows around the bars and develops the necessary bond (code requirements).
Chapter 8,9,10 Part 4
20. High strength-to-weight ratio, It is ductile, Equally strong in tension and compression, Can be formed and fabricated into any shape without experiencing any detrimental effects to its physical properties, Can be disassembled and reused, recycled, Can be cut, drilled and extended
21. W-shapes – wide flange sections – used as beams, columns, bracing, and truss components (most common in structural steel frames), and S-shapes – standard I-beams – narrow flanges sloped on the inside face – used for special applications such as overhead monorail systems.
22. Equal-leg angles, and Unequal-leg angles.
23. Cold-Formed Structural Shapes – normally rolled from sheet steel as C-shapes or Z-shapes – used in lightweight pre-engineered structures.
24. The strength of the individual sections that make up the frame, and The overall stability of the frame – dependent upon the arrangement of the framing members and the type of connections.
25. Braced – lateral bracing is used to prevent horizontal movement of the frame, and Unbraced – the stiffness of the load-carrying sections in the assembled frame must resist the anticipated horizontal movement.
Chapter 8,9,10 Part 5
26. Pin-type – are flexible and allow rotation to occur between connected members when deflections occur due to applied loads.
Rigid or moment resisting connections – add stability to the frame by their ability to resist rotation that occurs between the frame sections when the frame is under the influence of lateral loads.
27. Anchor bolts, Columns, Girders, beams, Joists, Steel decking, and Bracing.
28. bolting and welding.
29. Structural bolts are classified according to type of thread, type of steel, steel strength, shape of head and nut, and type of shank.
30. A307 – standard unfinished or machine bolt – low strength used in temporary and secondary connections,
A325 – hexagonal heads and nuts – easier to grip – made of high-strength carbon steel used in connections, and
A490 – hexagonal heads and nuts – easier to grip – made from alloy steel and higher strength than A325.
31. There are 2 types of bolted connections – bearing type and friction type.
32. Fillet weld – used wherever possible because no edge preparation is required, and
Groove or butt weld – used when the full strength of the connected parts is to be developed.
Chapter 11,12 Floor and roof System Questions
Flooring Systems and Industrial Flooring
1. What is a subfloor and what materials are used to construct subfloors?
2. What are the 2 parts of a floor system?
3. Describe the 2 different ways in which wood subfloors are constructed.
4. Describe the 2 types of concrete subfloors?
5. What does the floor type depend upon as it relates to concrete structural slabs?
6. List the 5 concrete structural slab floor types.
7. What is the advantage of adding post-tensioning strands to concrete slabs?
8. What is an integrated distribution floor system and what are the components?
9. List 7 industrial floor finishes.
10. In what situation could the use of access flooring be considered as a viable alternative to other flooring systems?
Roof Systems and Industrial Roofing
1. List 4 basic roof system design requirements that must be dealt with when considering a roof design.
2. Describe the 2 variations in basic roof design and construction.
3. Describe the term ponding as it relates to a low slope roof.
4. List 3 components of a roof-structural framing system.
5. What types of loads must a roof be able to support?
6. List 1 advantage of using open-web steel joists over precast pre-stressed concrete joists.
7. List 5 roof systems or styles.
8. List 5 materials used as roof decks.
9. What does the type of roof membrane depend on – list 7?
10. List 6 direct advantages of green roofs.
Chapter 11,12 Answer part 1
Flooring Systems and Industrial Flooring
1. The SUBFLOOR is considered part of the structural frame in floor systems suspended above grade – it must be capable of supporting all superimposed design loads.
Sub floors are constructed of wood, concrete, or a combination of concrete and steel.
2. The base or subfloor, and The application of the floor finish.
3. For heavy loading conditions – 2×4, or 2x6s are placed on edge at right angles to the floor beams the sections are laminated together side-by-side, using spikes, in a controlled random arrangement-as per code. And More common approach use heavy planking, laid flat
4. Slab on Grade – is a floor poured directly on a prepared subgrade to provide a clean and durable surface for building occupants.
Structural Slabs-must span between supporting walls, columns, or beams, must be able to support its own dead weight and the superimposed load that it was designed to carry.
5. The intended use of the building, The type and magnitude of the loads to which the floor will be subjected, The length of the span between supports, The type of building frame, and The number of stories in the building.
Chapter 11,12 Part 2 (Flooring System)
6. One-way solid slabs, Two-way solid flat slabs, Two-way flat-plate slab, One-way joist slab and, Waffle slab.
7. Post-Tensioned Concrete Slabs– adding post tensioning strands to concrete slabs produces sections that can span over greater distances than non-prestressed sections and are able to support greater loads with less deflection and virtually no cracking.
8. Developed by Portland Cement Association – specially designed for use in low rise apartments, light commercial and industrial buildings, and residences.
The I/D concept includes 3 basic components: Steel truss Is, Forms to be left in place, and Cast-in-place concrete.
9. Wood (block or strip), Concrete, Terra-cotta tile, Mastic flooring, Resilient tile, Access flooring, Terrazzo
10. Access Flooring– allows for flexibility in the placing of electrical outlets and telecommunications wiring throughout the office- can be placed on top of existing floors with sufficient space for the running of wires and conduits between the two – supported by preformed metal frames.
Chapter 11,12 Part 1
Roof Systems and Industrial Roofing
1. Building-envelop requirements, Waterproof membrane selection, Structural considerations, and Maintenance programs.
2. Divided into 2 variations: Pitched roofs, and low-sloped roofs
3. Term Ponding in Low-sloped roofs means the excessive accumulation of water at low-lying areas that remains after 48 hours after the end of the rainfall under conditions conducive to drying.
4. The building size, Shape, and The building material that is used.
5. Loads Must Roof Be able to Support:
Primary framing members- trusses, beams, or girders
Secondary supports – purlins or joists
Roof decking -(must be capable of supporting the dead weight of the roof insulation and waterproof membrane and live loads)
Chapter 11,12 Part 2 (Roof Systems)
6. Open-Web Joist Roof Framing – use light, open-web pre‑engineered roof sections – open-web joints – cost effective – used primarily in low-slope or flat roofs. Where as
Precast Concrete Roof-framing systems – pre-stressed precast concrete consists of beams and joist – used primarily in warehouse type structures where spans are repetitive, allowing for large numbers of similar sections.
7. Stressed-Skin Panel, Folded-Plate, Long-Barrel Shell, Dome Shells, Hyperbolic Paraboloid Saddle Shaped
8.
Wood, Concrete, Steel, Gypsum, and Lightweight cellular concrete.
9. The suitability of the membrane material (including cost) for the shape of the roof structure, The necessity, location and type of vapour barrier, The characteristics of the particular insulation that will be used, The thermal characteristics and rigidity of the decking material, The required durability of the roofing membrane, The fire resistance of the roofing and, The esthetic value of the roofing material.
10. Longer roof membrane life, Improved sound insulation, (Smaller heating, ventilation and AC, equipment), Fewer roof drains, Lesser amount of roof insulation, An esthetically pleasing rooftop garden.