# Structural Analysis

question 3-6

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question 3-6

ARMWOOD, CATHERINE 1

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS

Due Thursday 9/16/2020 by 11:59pm.

1. Compute the values requested using the basic floor framing plan shown in the accompanying figure. Consider floor live-load reductions following the provisions of

ASCE 7 as appropriate. For purposes of these problems, assume that this is the uppermost

floor in a multistory office building. Also assume that it has a one-way slab behavior.

a. Load on column B3 contributed by this floor if the floor live load is 150psf. b. Load on column A3 contributed by this floor if the floor live load is 75 psf. c. Load on column A1 contributed by this floor if the floor live load is 100psf. d. Load on an interior floor beam if the floor live load is 75psf. e. Load on Girder B2-B3 if the floor live load is 50 psf.

2. The loading for a single frame-line of a three story building is given in the figure. The

roof is subjected to a snow load and a dead load, while the two upper floors are subjected

to floor live load and dead load. Using the tributary approach and without taking any

reductions, find the following:

a. The total dead load, live load and snow load present in column B between the

second and third floors.

b. Sketch the loading diagram including all relevant loads for the transfer girder

located at the second floor.

c. The total dead load, floor live load, and snow load present in column A between

the ground and the second floor.

ARMWOOD, CATHERINE 2

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS

d. Using the strength-based load combinations, find the total design axial load that

should be used for the column described in part c. (Assume the floor live load

results from a load less than 100 psf.)

3. Compute the values requested using the basic floor/roof framing plan. The building

consists of five levels as shown. If live load reductions are considered, use the

appropriate provisions given in ASCE 7.

a. Assume W = 20 ft and D = 48 ft and that the slab behavior can be classified as a

two-way slab. If the dead load for the roof is found to be 22 psf, compute and

sketch the load diagrams for B1, B3, G3, and G4 located in the roof. (Be careful

of the opening.)

b. Assume W = 20 ft and D = 48 ft and that the slab behavior can be classified as a

two-way slab. If the dead load for the roof is found to be 22 psf, compute and

sketch the load diagrams for B1, B2, G1, and G2 located in the roof. (Ans: point

loads on G1 = 1848 lb, point loads on G2 = 3696 lb)

c. Assume W = 20 ft and D = 30 ft and that the slab behavior can be classified as a

one-way slab. If the unreduced floor live load is 50 psf, compute and sketch the

load diagrams for B1, B2, G1, and G2 located in the fourth floor. Take

appropriate reductions. (Ans: point loads on G1 = 3593 lb, point loads on G2 =

5625 lb)

ARMWOOD, CATHERINE 3

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS

ARMWOOD, CATHERINE 4

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS

4. The senior engineer working on a two-story office building project has laid out a framing plan to

be used for the first floor and roof level. The box with an × in the plan view represents an

opening in the floor and roof for the elevator. The senior engineer anticipates using a concrete

slab supported by steel beams and girders. Before we can begin to design the members, we

need to know the idealized load on each member due to each type of load.

a. We are tasked with finding the idealized live load. For preliminary design of the

members, we can ignore the corridors and consider the entire floor to be offices. Let’s

start with the idealized live load on girder B3-B4 for level 1 (first floor).

b. The maximum likely snow load on the roof is 20 psf. Our task is to find the idealized

snow load on beam A2-B2 for level 2 (the roof).

c. A more experienced engineer on the team anticipates the floor and roof to be 12 inches

thick. The superimposed dead load (weight of flooring, ceilings, lights, ducts, etc.) will be

about 10 psf on the floor and roof. Initially let’s assume each beam and girder has a self-

weight of 75 plf. Our task is to find the idealized dead load on girder A3-B3 for level 2,

including its own self-weight.

ARMWOOD, CATHERINE 5

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS

5. We are to design the lateral load-resisting system for a building with a high roof. The senior

engineer has already decided that the outer walls perpendicular to the wind will be the lateral

load-resisting elements (e.g., the beige walls will resist wind from the left in the photo). The

senior engineer has also concluded that the best way to transfer the wind pressure to the outer

walls is by purlins. Therefore, the outer skin of the wall touches only the slab-on-grade and the

purlins. Before we can analyze and design the purlins, we need to determine the idealized line

load on each purlin due to the wind. The wind generates a pressure of 950 Pa.

ARMWOOD, CATHERINE 6

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS

6. Our team is designing the lateral load-resisting system for a two-story office building. To do so,

we need to determine the wind loads on the lateral load-resisting elements. At this preliminary

stage, let’s consider the floor and roof diaphragms to be flexible, and consider the wind pressure

to be uniform. Note that the south and east walls have been cut away so that we can see the

system supporting them.

a. When the wind blows from the south, it creates a uniform pressure of 25 psf on the

south elevation.

i. Our job is to convert the applied wind pressure into line loads that act at each

diaphragm level on the windward side.

ii. Then we are to convert the line loads into point loads that act at the locations

where the diaphragms meet the lateral load-resisting elements.

b. When the wind blows from the east, it creates a uniform pressure of 30 psf on the east

elevation.

i. Our job is to convert the applied wind pressure into line loads that act at each

diaphragm level on the windward side.

ii. Then we are to convert the line loads into point loads that act at the locations

where the diaphragms meet the lateral load-resisting elements.

iii.

ARMWOOD, CATHERINE 7

ASSIGNMENT #4: VERTICAL AND HORIZONTAL LOADS