structural calculations

Urban and Civil

Nov 25, 2013 (4 years and 5 months ago)

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Architectural Drawing

Structural Calculations

Beams and Girders

Beams or girders support floor joists over long spans.

Beams or girders May be wood or metal.

Wood beams may be built
-
up or solid.

Steel beams may be S
-
beams or W
-
beams.

Size based on weight of the structure and the span.

Structure Loads

Dead load

is the weight of the structure itself:

Roofing, siding, joist, etc.

Live load

is the fixed or moving weights:

Furniture, appliances, occupants, snow on the roof, etc.

Structural Calculations

Table S
-
1: Residential Live and Dead Loads

Area

Live Load

Dead Load

Each Floor

40 lbs./sq. ft.

10 lbs./sq. ft.

Attic (with Storage)

20 lbs./sq. ft

10 lbs./sq.
ft.

Attic (without Storage)

0 lbs./sq. ft.

10 lbs./sq. ft.

Partitions

0 lbs./sq. ft.

10 lbs./sq. ft.

Roof (235 lb. Comp)

30 lbs./sq. ft

8 lbs./sq. ft.

Roof (cedar shakes)

30 lbs./sq. ft

7 lbs./sq. ft.

Roof (tile)

30 lbs./sq. ft

25 lbs./sq. ft.

Roof (
built
-
up)

30 lbs./sq. ft

8 lbs./sq. ft

Weight Supported by Beam

Typical Load
Distribution in a
Structure

Structural Calculations

Typical Load Distribution in
a Structure

Structural Calculations

Building Loads

Make a sketch of the load distribution.

Make a listing of the building loads using the following format:

Area

Construction

Live Load
(lbs/sq ft)

Dead Load

(lbs/sq ft)

Total Load

(lbs/sq ft)

ROOF

BUILT
-
UP

30

8

38

ATTIC

WITH STORAGE

20

10

30

FLOOR

FIRST FLOOR

40

10

50

PARTITIONS

PARTITIONS FIRST FLOOR

0

10

10

Total
Building
Load

128 LBS/SQ FT

Structural Calculations

Beam Support Area with no columns

60'-0" (SPAN)
30'-0"
15'-0"
15'-0"
7'-6"
7'-6"
BEAM SUPPORT AREA
NO COLUMNS
15'-0"
Structural Calculations

Beam Support Area with one column

30'-0" (SPAN)
BEAM SUPPORT AREA
ONE COLUMN
60'-0"
30'-0"
15'-0"
15'-0"
7'-6"
7'-6"
15'-0"
Structural Calculations

Beam Support Area with two columns

20'-0" (SPAN)
BEAM SUPPORT AREA
TWO COLUMNS
60'-0"
30'-0"
15'-0"
15'-0"
7'-6"
7'-6"
15'-0"
Structural Calculations

Beam Calculations

Make a listing of the loads acting on the beam using the following format:

Area

Building Load (lbs/sq ft)

ROOF

0

ATTIC

30

FIRST FLOOR

50

PARTITIONS

10

Total

Load
acting on the beam

90 LBS/SQ FT

Make a series of trials
using various numbers of columns and record the date using the following format:

Trial

Number of
Columns

Span (ft)

Support
Width (ft)

Support
Area

(sq ft)

Load

(lbs/sq ft)

Support
Load
(Kips)

Beam Size

1

0

60

15

900

90

81

NA

2

1

30

15

450

90

40.5

W14
x 61

3

2

20

15

300

90

27

W10 x 49

4

3

15

15

225

90

20.25

W8 x 31

Mark
final selection of beam size and number of columns.

Structural Calculations

W
-
beam span and load table.

(American Institute of Steel Construction)

Structural Calculations

Column Support Area with one column

30'-0" (SPAN)
COLUMN SUPPORT AREA
ONE COLUMN
60'-0"
30'-0"
15'-0"
15'-0"
7'-6"
7'-6"
15'-0"
Structural Calculations

Column Support Area with two columns

20'-0" (SPAN)
COLUMN SUPPORT AREA
TWO COLUMNS
60'-0"
30'-0"
15'-0"
15'-0"
7'-6"
7'-6"
15'-0"
Structural Calculations

Column Calculations

Make a series of trials using various numbers of columns and record the date using the following format:

Number of
Columns

Span (ft)

Support
Width (ft)

Support
Area

(sq ft)

Load

(lbs/sq ft)

Support
Load

(Kips)

Column
Height (ft)

Colu
mn
Size

1

30

15

450

90

40.5

13

5”

2

20

15

300

90

27

13

4”

3

15

15

225

90

20.25

13

3.5”

Structural Calculations

Beam Support Area

Structural Calculations

Column Support Area

Structural Calculations

Ceiling Joists

Structural Calculations

Procedure for Using Span Data Charts

Select species of wood to be used.

Select appropriate live load.

Determine lumber grade to be used.

Scan the lumber grade row and note the maximum spans.

Select the joist size and spacing that will support the desired
live load (16" OC spacing is typical).

Structural Calculations

Joist and Rafter selection

Indicate the selection of joist and rafter sizes and spacing by listing the data using the following format (be sure to show all possible combinations):

Live Load

40

Dead Load

10

Area

Species

Grade

Span (ft)

Size

Spacing

Floor
Joist

Douglas Fir

#2

16

2 x 10

12

Floor Joist

Douglas Fir

#2

16

2 x 12

12

Floor Joist

Douglas Fir

#2

16

2 x 12

16

Floor Joist

Douglas Fir

#
1

16

2 x 10

12

Floor Joist

Douglas Fir

#
1

16

2 x 10

16

Structural Calculations

Joist and Rafter selection

Indicate the selection of joist and rafter sizes and spacing by listing the data using the following format (be sure to show all possible combinations):

Live Load

20

Dead Load

10

Area

Species

Grade

Span (ft)

Size

Spacing

Ceil
ing Joist

Douglas Fir

#2

15

2 x 8

12

Ceiling Joist

Douglas Fir

#2

15

2 x 8

16

Ceiling Joist

Douglas Fir

#2

15

2 x 10

12

Ceiling Joist

Douglas Fir

#2

15

2 x 10

16

Ceiling Joist

Douglas Fir

#2

15

2 x 10

24

Structural Calculations

Joist and Rafter selection

Indicate the selection of joist and rafter sizes and spacing by listing the data using the following format (be sure to show all possible combinations):

Live Load

40

Dead Load

10

Area

Species

Grade

Span (ft)

Size

Spacing

Floor
Joist

Douglas Fir

#2

16

2 x 10

12

Floor Joist

Douglas Fir

#2

16

2 x 12

12

Floor Joist

Douglas Fir

#2

16

2 x 12

16

Floor Joist

Douglas Fir

#
1

16

2 x 10

12

Floor Joist

Douglas Fir

#
1

16

2 x 10

16

Live Load

20

Dead Load

10

Area

Species

Grade

Span (ft)

Size

Spacing

Ceiling Joist

Douglas Fir

#2

15

2 x 8

12

Ceiling Joist

Douglas Fir

#2

15

2 x 8

16

Ceiling Joist

Douglas Fir

#2

15

2 x 10

12

Ceiling Joist

Douglas Fir

#2

15

2 x 10

16

Ceiling Joist

Douglas Fir

#2

15

2 x 10

24

Live Load

Dead Load

Area

Species

Grade

Span (ft)

Size

Spacing

Roof Rafter

Southern Pine

#2

16

2 x 8

12

Roof Rafter

Southern Pine

#2

16

2 x 10

12

Roof Rafter

Southern Pine

#2

16

2 x 10

16

Roof Rafter

Southern Pine

#2

16

2 x 12

16

Roof Rafter

Southern Pine

#2

16

2 x 12

24

Mar
k
the final selection of materials.
Use the same species and grade for the selected structural components.

Structural Calculations

Footing Calculations

Make a listing of the loads acting on the footings using the following format:

Type of Ground

Safe Ground Loading

(lbs/sq ft)

Area

Length (ft)

Building
Load

(lbs/sq ft)

Total Load
(lbs/ft)

Roof

Attic

Floor

Partiti
ons

Area

Wall Width
(ft)

Length (ft)

Building
Load

(lbs/cu ft)

Total Load
(lbs/ft)

First floor wall

Basement wall

Total load acting on the footing

Safe ground loading for soil type

Minimum footing width
(ft)