CVEN 4545 Steel Design 1

Transcription

1 CVEN 4545 Steel Design 1 George.Hearn@colorado.edu s. Design Basis. s Table 1 Source Direction Duration Stage Dead D Vertical Permanent Construction, Service Live L Vertical Transient Service Construction Live Lr Vertical Transient Construction Roof Live Lr Vertical Transient Service Snow S Vertical Transient Construction, Service Wind W Horizontal and Vertical Transient Construction, Service Rain (ponding) R Vertical Transient Construction, Service Seismic E Horizontal and Vertical Transient Construction, Service Sources of Table 2 Symbol D L Lr S Name Dead load Live load Roof live load Snow load Description Weight of permanent parts of a building including, but not limited to, walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding, other similarly incorporated architectural and structural items, and fixed service equipment including the weight of cranes. produced by the use and occupancy of the building or other structure that does not include dead load or environmental loads, such as wind load, snow load, rain load, earthquake load, flood load, etc. on roof produced (1) during maintenance by workers, equipment, and materials and (2) during the life of the structure by movable objects, such as planters or other similar small decorative appurtenances that are not related to occupancy. due to snow accumulation. Magnitude of snow load depends on geographic location (ground snow load), roof slope, drifting snow, sliding snow, extra load from rain on snow, adjacent roofs and sites, and consequences of load in excess of design value. R Rain load The weight of water that could accumulate on a roof from blockage of the primary drainage system. The roof is designed to withstand the load created

2 CVEN 4545 Steel Design 2 George.Hearn@colorado.edu Symbol W E Name Wind load Earthquake load Description by that water plus the uniform load caused by water that rises above the inlet of the secondary drainage systems at its design flow. Simultaneous horizontal and vertical loads due to wind acting at the building envelope. Magnitude of wind load depends on geographic location, site exposure, building height and building shape. on building during earthquakes. Magnitude of earthquake load depends on geographic location, site (soil) characteristics, and building height, mass, stiffness and connection details. Design Basis Strength Design Basis Eq 1 LRFD Basis Where Manual Eq (2-1) = Value from a factored load combination = A resistance factor = A nominal strength Eq 2 Table 3 LRFD Factored Combinations (Manual 2-10) (1) 1.4D (2) 1.2D + 1.6L + 0.5(Lr or S or R) (3) 1.2D + 1.6(Lr or S or R) + (0.5L or 0.5W) (4) 1.2D + 1.0W + 0.5L + 0.5(Lr or S or R) (5) 1.2D + 1.0E + 0.5L + 0.2S (6) 0.9D + 1.0W (7) 0.9D + 1.0E

3 CVEN 4545 Steel Design 3 George.Hearn@colorado.edu Eq 3 ASD Basis Where Manual Eq (2-2) = Value from a load combination = A safety factor = A nominal strength Table 4 ASD Combinations (Manual 2-11) (1) D (2) D + L (3) D + (Lr or S or R) (4) D L (Lr or S or R) (5) D + (0.6W or 0.7E) (6a) D L (0.6W) (Lr or S or R) (6b) D L (0.7E) S (7) 0.6D + 0.6W (8) 0.6D + 0.7E

4 CVEN 4545 Steel Design 4 George.Hearn@colorado.edu Exercise Combinations A concrete floor has self weight (D) equal to 33psf, a construction live load (Lr) equal to 25psf and an occupancy live load (L) equal to 40psf. Determine the controlling LRFD load combination and the value of the factored load during construction, and separately in service. During Construction psf In Service psf A concrete floor has self weight (D) equal to 33psf, a construction live load (Lr) equal to 25psf and an occupancy live load (L) equal to 40psf. Determine the controlling ASD load combination and the value of the load during construction, and separately in service. During Construction 3 58 psf In Service 2 73 psf A steel beam has self weight (D) equal to 40 plf, and carries a concrete floor has self weight (D) equal to 33psf, a construction live load (Lr) equal to 25psf and an occupancy live load (L) equal to 40psf. Beams are parallel and spaced at 10 ft. Determine the controlling LRFD load combination and the value of the factored load during construction, and separately in service. During Construction plf In Service plf A steel beam has self weight equal to 40 plf, and carries a concrete floor has self weight equal to 33psf, a construction live load equal to 25psf and an occupancy live load equal to 40psf. Beams are parallel and spaced at 10 ft. Determine the controlling ASD load combination and the value of the factored load during construction, and separately in service. During Construction plf In Service plf

5 CVEN 4545 Steel Design 5 George.Hearn@colorado.edu Eq 4 Deflection Design Basis Table 5 Combinations for Deflections Total s Permanent s Transient s (1) D D (2) D + L D L (3) D + (Lr or S or R) D (Lr or S or R) (4) D L (Lr or S or R) D 0.75L (Lr or S or R) (5) D + (0.6W or 0.7E) D (0.6W or 0.7E) (6a) D L (0.6W) (Lr or S or R) D 0.75L (0.6W) (Lr or S or R) (6b) D L (0.7E) S D 0.75L (0.7E) S (7) 0.6D + 0.6W 0.6D 0.6W (8) 0.6D + 0.7E 0.6D 0.7E Eq 5 Design Specifications Building Authority The building code in Boulder, Colorado is Chapter 10-5 of the Boulder Revised Code 1 What is the legislative intent of Chapter 10-5 of the Boulder Revised Code? What model building code is adopted by Boulder, with amendments? What is the minimum roof snow load in the Boulder Building Code? What is the ultimate design wind speed for areas west of Broadway in the Boulder Building Code? to protect the public health and safety The 2012 edition of the International Building Code 30 psf 130 mph 1

6 CVEN 4545 Steel Design 6 George.Hearn@colorado.edu Figure 1