Site planning Hw Lecture 9 PDF

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MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

LAGUARDIA COMMUNITY COLLEGE MAE 209 - 5799 STRUCTURAL AND SITE PLANS HOMEWORK #9

Student: De la Cruz, Luis 05/20/2019

Professor: Rafea Hashimshak

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

Lecture 9 Hw: 1- Read chapters 11,12 2- Solve the homework assigned in the lecture file. Hw 1: Read about and explain, cast steel, and cold-worked steel. Cast steel is especially well suited for the production of custom shaped connections for steel structures that are stronger, lighter, and more attractive than possible with those fabricated from conventional rolled steel. Steel can be cold-worked or cold-formed (rolled or bent) in a socalled ‘cold’ state (at room temperature). Cold working causes the steel to gain considerable strength through a realignment of its crystalline structure.

Hw2: Define: -

High Strength Bolts A325-A490

Both are structural bolts. In contemporary steel frame construction, bolted structural connections rely almost exclusively on highstrength bolts. Carbon steel bolts are used in the fastening of minor framing elements or temporary connections. -

Carbon steel bolts A307

It’s the standard specification for carbon steel bolts, studs, and threaded rods of 60000 PSI tensile strength in sizes from ¼ inch to 4 inches in diameter. -

Bearing type connection

Bolts need only be installed to a snug-tight condition. In this case, movement between the joined members is resisted by the bolts themselves as the sides of the bolt holes in the connected members bear against the bodies of the bolts.

MEC 209 Prof. Rafea Al Suhili

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Spring 2019 LaGuardia Community College

Hw:Lecture 9

Slip-critical connection or friction type connections

This type of joint has a low probability of slip during the life of the structure. Because of their increased cost compared to connections with snug tight bolts, slip-critical connections should be used only when it is expected that slip in the joints would jeopardize serviceability of the structure. -

Swedge Bolt

A boltlike steel pin with annular rings that relies on a steel collar in lieu of a conventional nut to hold the pin. The Swedge bolt is installed using a special power tool to hold the pin under high tension while cold forming (swaging, a crimping like action) the collar around its end to complete the connection. -

Galling (Tearing)

Galling is caused by a combination of friction and adhesion between metallic surfaces during sliding. When galling occurs material is adhesively pulled from one surface leaving it stuck on the other in the form of a lump.

Hw3: Explain the method of bolts tightening. The bolt is tightened, protrusions on the washer are progressively flattened in proportion to the tension in the bolt. Inspection for proper bolt tension then becomes a relatively simple matter of inserting a feeler gauge to determine whether the washer has flattened sufficiently to indicate the required tension.

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

Hw4: State the advantages and disadvantages of light steel grade steel framing. Most of the advantages of wood light framing: It is versatile and flexible; requires only simple, inexpensive tools; furnishes internal cavities for utilities and thermal insulation; and accepts an extremely wide range of exterior and interior finish materials. Additionally, steel framing may be used in buildings for which noncombustible construction is required by the building code, thus extending its use to larger buildings and those whose uses require a higher degree of resistance to fire. Steel members tend to be straighter and more uniform than wood members, and they are much more stable dimensionally because they are unaffected by changing humidity. Among the disadvantages, they may corrode if exposed to moisture over an extended period of time, particularly in oceanfront locations, steel framing members cannot fall victim to termites or decay. Compared to walls and partitions of masonry construction, equivalent walls and partitions framed with steel studs are much lighter in weight, easier to insulate, and accept electrical wiring and pipes for plumbing and heating much more readily. Steel framing, because it is a dry process, may be carried out under wet or cold weather conditions that would make masonry construction difficult.

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

3- Solve the review and exercise problems of chapters 11,12. Chapter 11 1. What is the difference between iron and steel? What is the difference between wrought iron and cast iron? -

The difference is that steel is an alloy of iron which is stronger and better in tension and compression. It has 2% more carbon than iron. The basic distinction between the two is simple: Cast iron is iron that has been melted, poured into a mold, and allowed to cool. Wrought iron is iron that has been heated and then worked with tools.

2. By weight, what is the major raw material used in the making of cast iron? The major raw material used is Carbon. 3. How are steel structural shapes produced? How are the weights and thicknesses of a shape changed? During production, steel is reduced to a liquid state and then cast into structural shapes. These forms are refined later on when the steel is reheated and passed through a succession of rollers which squeeze it into the correct shape and size. A hot saw is used to trim the final length. 4. How does the work of the fabricator differ from that of the erector? The fabricator works to determine the length of steel pieces and detail of connections in the building then deliver them to the site. The erector works to assemble the pieces into a frame. 5. Explain the designation W21 x 68. W = wide flange, 21 = 21 inches deep, 68 = 68 pounds per one foot of length. 6. How can you tell a shear connection from a moment connection? What is the role of each? A shear connection simply connects the web of the beam to the column whereas a moment connection requires the beam’s flanges to extend through the column’s depth. Shear connections transfer vertical load through the floors but cannot resist lateral forces like moment connections can.

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

7. Why might a beam be coped? A coped beam has no top flanges so the tops of the beams are level and can be used for roof decking, floors, etc. 8. What is the advantage of composite construction? Increased strength, stiff, lightweight. 9. Explain the advantages and disadvantages of a steel building structure with respect to fire. How can the disadvantages be overcome? The heat of a fire is not hot enough to melt steel but it can deform it, thus causing it to lose structural integrity. This can be overcome by encasing the steel in various materials which absorb the heat and protect it for extended amounts of time. 10. List three different structural systems in steel that might be suitable for the roof of an athletic fieldhouse. Castellated beams, trusses, arches

Chapter 12 1. How are light gauge steel framing members manufactured? Sheet steel is fed from continuous coils through machines at room temperature that cold-work the metal and fold it into efficient structural shapes, producing linear members that are stiff and strong. 2. How do the details for a house framed with light gauge steel members differ from those for a similar house with wood platform framing? Light gauge steel members and nominal 2-inch wood members are framed essentially the same. Because light gauge steel members are more prone to twist or buckle under load, more attention must be paid to their bracing and bridging. 3. What special precautions should you take when detailing a steel-framed building to avoid excessive conduction of heat through the framing members? Should be detailed with thermal breaks: materials with high resistance to the flow of heat, such as foam plastic sheathing or insulating edge spacers between studs and sheathing.

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

4. If a building framed with light gauge steel members must be totally noncombustible, what materials would you use for subflooring and wall sheathing? Protection provided by gypsum sheathing and gypsum wallboard or plaster. 5. What is the advantage of a prescriptive building code for light gauge steel framing? Prescriptive building codes allow builders to design and construct light gauge steel-framed houses without having to employ and engineer or architect. 6. Compare the advantages and disadvantages of wood light frame construction and light gauge steel frame construction. a) Both are versatile and flexible; requires simple, inexpensive tools; furnishes internal cavities for utilities and thermal insulation; & accepts a wide range of exterior finish materials. b) Advantages: Steel can be used in buildings that require noncombustible construction. Steel framing is lighter than wood. Steel studs are often spaced at 24” O.C. while wood is 16” O.C. Spans longer distances. More straight and uniform. Much more stable dimensionally because they are unaffected by changing humidity. Cannot fall victim to termites or decay. c) Disadvantages: Steel may corrode if exposed to moisture over extended period of time. Thermal conductivity is much higher than wood.

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

4- Ching Hw: Q1) Sketch one-way and two-way beam girder system for steel building, showing girders and beams, primary and secondary beams, state typical span range.

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

Q2) Sketch and define steel box girder. Box girders are built up from shapes and have a hollow, rectangular cross section.

Q3) Estimate the depth of WF section and the flange width for a beam of a span of 20 ft., a girder of span of 30 ft.  Beam of a span of 20 ft. Beams = Span/20 Therefore: 20/20 = 1 ft. of depth. Width = 1/3 to 1/2 of depth Therefore: The width is between 1/3 and 1/2.  Girder of span of 30 ft. Girders = Span/15 Therefore: 30/15 = 2 ft. of depth. Width = 1/3 to 1/2 of depth Therefore: The width is between 2/3 and 1. Q4) For k-series standard steel joist 8 x30 inches what is the span range for 22k9. The span range for 22k9 is 24’ to 42’ (7 to 12m). Q5) What is the minimum bearing length for k series steel joists on reinforced concrete wall. The minimum bearing length for k series is 4” to 6” (100 to 150).

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Hw:Lecture 9

Q6) What is the span range for 8 inches Light-Gauge steel joists. The span range for 8” (205) Light-Gauge steel joists is 12’ to 18’ (3660 to 5485). Q7) Sketch a rigid frame and specify the max. span (plate 6.07)

MEC 209 Prof. Rafea Al Suhili

Spring 2019 LaGuardia Community College

Q8) Compare flat and Pratt trusses with sketch of each.

Q9) Sketch ribbed roof decking and Cellular Roof Decking.

Hw:Lecture 9...