1. Lateral Loads

2. Lateral Load sources Wind Seismic Flood or Tsunami Earth pressure
Tornado, hurricane, explosion
Seismic
Flood or Tsunami
Earth pressure
Basement or retaining walls

3. Probability
Code specified maximum wind velocities have a frequency of once per 50 years.
Code specified seismic loads have a frequency of once per 500 years.

4. Hurricanes Floyd 1999 Andrew 1992

5. Tornado Spawned by Katrina

6. Wind Damage (Hurricane Andrew)

7. Hurricane Storm Surge
Camille (1969) storm surge damage

8. Surf City, New Jersey 1944

9. Wind Scale

10. Saffir-Simpson Hurricane Scale Sustained Wind Velocities
Category One Hurricane:
Winds mph , Storm Surge 4 ~ 5 feet
Category Two Hurricane:
Winds mph, Storm Surge 6 ~ 8 feet
Category Three Hurricane:
Winds mph, Storm Surge 9 ~ 12 feet
Category Four Hurricane: Ex. Andrew 1992
Winds mph, Storm Surge 13 ~ 18 feet
Category Five Hurricane: Ex. Camille 1969
Winds greater than 155 mph, Storm Surge >18 feet

11. Tornado Classifications
F-0 Gale Tornado MPH Chimneys damaged; branches broken off trees; shallow-rooted trees uprooted
F-1 Moderate Tornado MPH Roof surfaces peeled off; mobile homes pushed off foundations or overturned; moving autos pushed off roads.
F-2 Significant Tornado MPH Roofs torn off frame houses; mobile homes demolished; box cars pushed over; large trees snapped or uprooted; light-object projectiles generated.
F-3 Severe Tornado MPH Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.
F-4 Devastating Tornado 158 – 206 MPH Well-constructed houses leveled; structures with weak foundations relocated; cars thrown and large projectiles generated.
F-5 Incredible Tornado MPH Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized projectiles hurtle through the air in excess of 100 yards; trees debarked; other incredible phenomena expected.

12. Hurricane Frequency

13. Global Warming

14. Wind Flow across a Low Rise Building
Positive pressure area
Negative pressure areas

15. Wind flow across a low rise building

16. Wind Effect on Roofs
Windward roof steep enough to feel pressure. Leeward roof subjected to suction.
Leeward Roof
Windward roof shallow enough to feel suction. Breakpoint approx 20°.

17. Earthquakes
Niigata 1964

18. Tsunami 12/2004

19. Tsunami Effects

20. SOURCE: US NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
PACIFIC MARINE ENVIRONMENTAL LABORATORY, US NATIONAL DATA
BUOY CENTER; © 2004 KRT

21. Scale for Measuring earthquakes was developed by seismologist Charles Richter
Class Magnitude
Great 8 or more
Major
Strong
Moderate
Light
Minor

22. Types of Seismic Waves

23. Probability (statistics of chance)

24. Defining Lateral Loads
Codes specify environmental and live loads
Local geography affects intensity of wind loads
Importance factors are used to adjust loads for more important buildings
Seismic loads are affected by building geometry, mass, structural system and local geological conditions
Soil lateral loads affect by soil type and groundwater level

26. Seimic Loads
SEI/ASCE 7-02
Total lateral force V in each principal direction should be computed as
V = CsW
Cs = seismic response coefficient
W = Total dead load and applicable portions of other loads

27. Applicable portions of other loads
Storage areas: minimum of 25% floor live load. Not needed for garages and open parking
When partition load is included in floor load design, actual partition weight or minimum of 10 psf whichever is greater
Total operating weight of permanent equipment
Where flat roof snow load exceeds 30 psf, design snow load should be included in W. When jurisdiction authority approves it, snow load contribution may be no less than 20% of design snow load.

28. For the given occupancy classification, the appropriate Seismic Use Group and corresponding Importance Factor Is is determine.

29. Building Classification for Lateral Loads: Category I
Buildings and other structures that represent a low hazard to human life in event of failure, such as
Agricultural facilities
Certain temporary structures
Minor storage facilities

30. Building Classification for Lateral Loads: Category II
Every building or structure that is not listed in Categories I, III, or IV

31. Building Classification for Lateral Loads: Category III
Buildings with substantial hazard to humans in case of failure, such as
Where more than 300 people congregate
Day care facilities greater than 150
Schools greater than 250
Colleges greater than 500
Heath care greater than 50, but no surgery or emergency
Jails and detention facilities
Power generation facilities no in Cat IV
Buildings not in Cat IV that mfg, process, handle, store, use or dispose of hazardous fuels, chemicals, waste, or explosives containing sufficient quantities to be dangerous if released

32. Building Classification for Lateral Loads: Category IV
Essential facilities such as
Hospitals/health care
Fire, rescue, ambulance
Emergency shelter
Emergency preparedness, communication, operations
Power generating facilities/public utilities + ancillary facilities (towers, storage tanks, substations, etc.)
Aviation control towers
Water storage facilities and pump stations
Critical national defense
Hazardous materials facilities where quantity exceeds threshold quantity determined by the relevant authority

33. Seismic Use Group DesignationsII
III
Occupation Category ✪ IV

34. Occupancy Importance Factors
Seismic Use Group Is I
1.0 II
1.25
III
1.5

35. Site classification (A-F) must be determined, and then the site coefficients Fa and Fv can be found. These are the maximum considered earthquake (MCE) spectral acceleration. Fa is for short period and Fv for 1 second. Ss and S1 values are taken from the maps

36. Seismic Site Classificationvs
N or Nch su
A: Hard Rock
>5,000 ft/s NA
B: Rock
2,500 – 5,000 ft/s
C: Very dense soil and soft rock
1,200 – 2,500 ft/s
>50
>2,000 psf
D: Stiff soil
600 – 1,200 ft/s
15-50
1,000 – 2,000 psf
E: Soil
<600 ft/s
<15
<1,000 psf
F: Soil requiring site-specific evaluation
Soils vulnerable to potential failure or collapse
Peats and/or highly organic clays
Very high plasticity clays
Very thick soft/medium clays
Vs =measured shear wave velocity
N = Standard penetration resistance (blows/ft)
Nch = corrected N for cohesionless layers (blows/ft)
su = undrained shear strength

37. Value of Fa for short-period max spectral acceleration
Site Class
Ss ≤ 0.25
Ss = 0.5
Ss = 0.75
Ss = 1.0
Ss ≥ 1.25 A
0.8 B
1.0 C
1.2
1.1 D
1.6
1.4 E
2.5
1.7
0.9 F *
* Site specific response analysis shall be performed except for structures with periods of vibration less than 0.5 sec. Values of Fa for liquefiable soils may be assumed equal to the values for the site class determined without regard to liquefaction in Step 3.

38. Value of Fv for 1 second max spectral acceleration
Site Class
S1 ≤ 0.1
S1 = 0.2
S1 = 0.3
S1 = 0.4
S1 ≥ 0.5 A
0.8 B
1.0 C
1.7
1.6
1.5
1.4
1.3 D
2.4
2.0
1.8 E
3.5
3.2
2.8 F *
* Site specific response analysis shall be performed except for structures with periods of vibration less than 0.5 sec. Values of Fv for liquefiable soils may be assumed equal to the values for the site class determined without regard to liquefaction in Step 3.

40. Seismic design category (A-F) and response factor R for the basic seismic force-resisting structural system must then be identified (SEI/ASCE 7-02 or relevant building code)
R-factor value is proportional to the amount of ductility, overstrength, and energy dissipation the seismic force resisting structural system possess.
For more ductile systems with larger R, the lateral seismic design force will be lower than a more vulnerable system with a lower R.
R = 1.0 is the conservative lower-bound. This is pure linear response

41. Seismic Base Shear Coefficient
SDS = design spectral response in short period range (g)
R = response modification factor for structure
Is = occupancy importance factor for seismic use group
However, Cs has a max value of
Use the smaller value
SD1 = design spectral at 1 second
T = fundamental period of the structure (s)

42. Design spectral accelerations
SDS = (2/3) SMS SD1 = (2/3) SM1 SMS = Fa Ss SM1 = Fv S1

43. Fundamental period
Actual determination is quite complex. Code allows the following approximation
Ta = Ct hnx
Ta = approximate fundamental period
Ct = period parameter (table)
x = period parameter (table)
hn = height from base to highest level of bldg (ft)

44. Values of period parameters
Structure Type Ct x
Moment resisting frame systems of steel where frame resists 100% of the seismic force and not enclosed or adjoined by more rigid components preventing frame deflection
0.028
0.8
Moment resisting frames of reinforced concrete where frames resist 100% of seismic force and not enclosed or adjoined by more rigid components preventing frame deflection
0.016
0.9
Eccentrically braced steel frames
0.03
0.75
All other structural systems
0.02

45. Vertical distribution of seismic forces
Lateral base shear V should be distributed over the height of the structure as concentrated loads on each floor level.
At a given floor level
Fx = Cvx V
where
wi is the portion of total gravity load of W at level I
hi = height from base to level I
k = 1 for building with T ≤ 0.5 s; 2 when T≥2.5 s (interp between)

46. Example Industrial building 180’ x 90’, clear height approx 30’
Supported on spread footings on moderately deep alluvial deposits (medium dense sand)
Astoria, Oregon

50. Site Class Site Class vs N or Nch su A: Hard Rock >5,000 ft/s NA
B: Rock
2,500 – 5,000 ft/s
C: Very dense soil and soft rock
1,200 – 2,500 ft/s
>50
>2,000 psf
D: Stiff soil
600 – 1,200 ft/s
15-50
1,000 – 2,000 psf
E: Soil
<600 ft/s
<15
<1,000 psf
F: Soil requiring site-specific evaluation
Soils vulnerable to potential failure or collapse
Peats and/or highly organic clays
Very high plasticity clays
Very thick soft/medium clays

51. Seismic Use Group First need occupancy category Category I ✪II
III
Occupation Category ✪ IV
First need occupancy category
Low occupancy, industrial building
Category I

52. Spectral Response Acceleration Ss and S1
Read from maps for short period and 1 second intervals for Oregon.
We get Ss = 1.5 and S1 = 0.6

53. MCE Spectral Acceleration
Site Class
S1 ≤ 0.1
S1 = 0.2
S1 = 0.3
S1 = 0.4
S1 ≥ 0.5 A
0.8 B
1.0 C
1.7
1.6
1.5
1.4
1.3 D
2.4
2.0
1.8 E
3.5
3.2
2.8 F *
Site Class
Ss ≤ 0.25
Ss = 0.5
Ss = 0.75
Ss = 1.0
Ss ≥ 1.25 A
0.8 B
1.0 C
1.2
1.1 D
1.6
1.4 E
2.5
1.7
0.9 F *
Use the tables!
For Fa, we have Ss = 1.5 so Fa = 1.0
For Fv, we have S1 = 0.6 so Fv =1.5

54. SMS, SM1, SDS, SD1 SMS = Fa Ss = 1.0 * 1.5 = 1.5 SDS = (2/3) SMS = 1.0
SM1 = Fv S1 = 1.5 * 0.6 = 0.9
SD1 = (2/3) SDS = 0.6

55. Parameters Site Class D SS 1.5 S1 0.6 Fa 1.0 Fv SMS SM1 0.9 SDS SD1
Seismic Use Group I

56. Period Parameters N-S we have moment resisting frame system of steel
From table, Ct = and x = 0.8 and R = 5
E-W we have a braced frame system
Thus Ct = 0.02 and x = 0.75 and R = 4.5

57. Seismic Base Shear Coefficient
Step 1 - Determine SS and S1
Step 2 - Determine site Soil Classification
Step 3 - Calculate Response Accelerations
Step 4 - Calculate the 5% Damped Design Spectral Response Accelerations
Step 5 - Determine the Seismic Design Category
Step 6 - Determine the Fundamental Period
Step 7 - Calculate Seismic Base Shear Coefficient

58. Seismic base shear coefficient
N-S: Cs = 1.0/(5/1.0) = 0.20 E-W: Cs = 1.0/(4.5/1.0) = 0.22

59. Seismic base shear coefficient
But, there are limits Max value:

60. We need the Period, T Approx: Ta = Ct hnx hn = 30.5
N-S: Ta = (30.5).8 = 0.43 s
E-W: Ta = 0.02 (30.5).75 = 0.26 s

61. Maximum Cs values N-S: Cs = SD1 I / (TR) = 0.6 * 1 /(0.43 * 5) = 0.278
E-W: Cs = 0.514

62. Seismic Base Shear Coefficient
N-S: Cs = 0.20
E-W: Cs = 0.22

63. Vertical Distribution
We have just one story – mezzanine does not count because it is less than 1/3 of the footprint
F = Cv V = 1 V for single story building
V = Cs W

64. Loads Snow load from map 25 psf Dead load on roof = 15 psf
Mezzanine live load, storage = 125 psf
Mezzanine slab/deck dead load = 69 psf
Wall panels = 75 psf

65. Loads On mezzanine, need 25% of storage load
%(125) = = 100 psf
On roof, snow load is less than 30 psf, so not needed.

66. Roof Projected roof area: 90 x 182 = 16,380 ft2
Inclined roof area: x 182 = 16,438 ft2
Roof load: 15 * 16,438 = kips

67. Mezzanine Mezzanine area: 40 x 90 = 3,600 ft2
Mezzanine floor: 360 kips
Mezzanine frames: 35 kips
Main framing: 27 kips

68. Walls Long walls: 2 x 32 x 180 x 75 / 2 = 437
Short walls: 2 x 35 x 90 x 75 / 2 = 224

69. Load by direction Source E-W N-S Roof D+L 243 Long walls -- 437
Short walls
224
Mezzanine slab
360
260
Mezzanine framing 35
Main framing 27
Seismic Weight
889 kips
1,102 kips

70. Shear force V = Cs W N-S: V = 0.2 * 1,102 = 220.4 kips
E-W: V = 0.22 * 889 = kips