MPNH Floor Extension
Structural Analysis of Floor Extension
Assumptions and load paths:
-
Beams and columns are perfectly connected.
-
Floor load of the hallway transfers directly into the three adjacent columns.
-
Roof load supported by columns.
-
Floor load is distributed evenly in wood joists i.e. additional load per meter of joist is constant.
-
Wall load acts as a uniformly distributed load on the beams that it’s placed on.
-
Beams transfer load on the closest column.
-
Beams in the middle (B3, B4, B8) take twice the load of the outside beams.
-
Dead load (DL) is the weight of the components.
-
According to the NBCC, design live load (LL) applied on the floor area for this type of building structure is 4.8 kPa.
Notes:
-
Calculated loads are rounded up since it is more conservative.
-
Load on columns and beams are in bold.
-
The beams and columns are named and labeled in Figure 2 for easy reference.
Hallway Load:
Hallway area = 19.9 m2
DL = 0.11 + 0.08 = 0.19 kN/m2 LL = 4.8 kN/m2
Unit hallway load = DL + LL = 4.8 + 0.19 = 4.99 kN/m2
C1 and C3 take one quarter of the total hallway load. C2 takes the remaining half of the total hallway load:
Wall Load:
Wall 1,2 area = 15’ 6” × 12’ = 186 ft2 = 17.3 m2
Wall 1,2 load = 17.3 × 0.16 = 2.8 kN
-
Uniform load on B1,B2 = 2.8 / 1.83 = 1.6 kN/m
-
Load on C1, C3 = 2.8 / 2 = 1.4 kN
-
Load on C2 = 2.8 kN
Wall 3 area = 11’ 6” × 12’ = 138 ft2 = 12.8 m2
Wall 3 load = 12.8 × 0.16 = 2.0 kN
-
Uniform load on B9 = 2.0 / 1.37 = 1.5 kN/m
-
Load on C3,C6 = 1.0 kN
Roof Load:
-
Area of roof above hallway = 19.9 m2
-
Area of roof above floor extension= 46.6 m2
Floor Extension Flooring Load:
DL = 0.19kPa
LL = 4.8 kPa
Total flooring load = (DL+ LL) × Area of floor extension
= (0.19 + 4.8) × 501.25 = 2501 kN
Total joist length = 169.5 m
Flooring load unit length of joist = 2501 / 169.5 = 14.8 kN/m
Total Flooring Loads on Joists:
Load on lateral 1 joist = 14.76× 3.5 = 51.66 kN
Load on lateral 2 joist = 14.76 × 4.3 = 63.47 kN
Load on longitudinal joist = 14.76 × 4.7 = 69.37 kN
1 Longitudinal joist on each B1,B2,B5,B6 (uniform load)
1 Lateral 1 joist on each B7, B9 (uniform load)
2 Lateral 1 joists across each B3, B4 (point loads)
15 Lateral 2 joists across B1,B3,B5 (point loads)
15 Lateral 2 joists across B2,B4,B6 (point loads)
Total number of joists = 1 × 4 + 1 × 2 + 2 × 2 + 15 + 15 = 40 joists
The point loads of the lateral beams are summed to give a uniform load.
Total Load of Joists (with weight of joists):
Load of Lateral 1 joist = 51.66 + 0.18 = 51.9 kN
Load of Lateral 2 joist = 63.47 + 0.26 = 63.7 kN
Load of Longitudinal joist = 69.37 + 0.26 = 69.7 kN
Floor Extension Loads on Beams:
Floor Extension Loads on Columns:
Top View of Structural Layout with Beams and Columns
Top View of Structural Layout with Beams and Columns
