1.1 General
Loads and external forces to be
considered in the design of plant structures include but are not limited to the
following:
Abbreviations:
D = Dead loads
L = Live load
O = Operating load
T = Test load
Vh = Vehicular
load
Th = Thermal
friction forces
I = Impact Load
J = Dynamic/ Vibration load
H = Earth Pressure
W = Wind load
R = Rain Load
E = Earthquake load/ Seismic Load
M = Maintenance load
1.2 Dead Load (D)
1.2.1 Dead Load of Equipment (DE)
Dead loads are
the weight of equipment and all materials permanently fastened thereto or
supported thereby, including piping attached to equipment, fireproofing,
electrical conduit and insulation.
1.2.2 Dead Load of Structure Proper (DS)
Dead loads are
the self-weight of structures or foundation. Unit weights of the major
construction materials shall be in accordance with SKBI – 1.3.53.1987 UBC:
624.042, Chapter 2, Table 1, and those listed below:
Table 1
Unit Weight of
Material
1.3 Live Load (L)
Live load are
the weight of all movable loads, including: personnel, tools, miscellaneous
equipment, movable partitions, cranes, hoists, part of dismantled equipment,
and stored material.
Live Loads and
reduction of live load shall be in accordance with UBC, Chapter 16, and as
specified below:
Table 2
Live Loads
1.4 Operating Load (O)
Operating load
are the dead load of equipment plus the weight of any liquid or solids that is
present within the vessels, equipment or piping during normal operation.
1.5 Test Load (T)
Foundation and
structures supporting vessel and tanks for which the hydro test will be carried
out shall be designed to support the dead load of equipment plus a full hydro
test load of the equipment simultaneously.
1.6 Vehicular Load (Vh)
All heavy-duty
roads, pavement, bridges and underground installations accessible to truck
loading shall be designed as per AASHTO.
Bridges,
trenches and underground installations accessible to truck loading shall be
designed to withstand HS20 load as defined by AASHTO Standard Specifications
for Highway Bridges. Maintenance or construction crane or bridge crane loads
shall be considered also.
1.7 Thermal Load (Th)
Thermal load
shall be defined as those forces caused by a change in temperature. Thermal
load results from both operating and environment conditions. Such forces shall
include those caused by vessel or piping expansion or contraction, and
expansion or contraction of structures
Thermal loads
and displacements caused by operating conditions shall be based on the design
temperature of the item of equipment rather than the operating temperature.
In the design of
pipe racks and pipe supports, a horizontal friction force (Ff) due to thermal
expansion or contraction of pipe or equipment shall be applied at the support
bearing surfaces. This force shall be assumed to act in either direction
parallel or perpendicular to the piping run and shall be as follow :
The friction
coefficients shown in Table 4 shall be used for determining restraint (force)
due to temperature change or lateral force on sliding surfaces:
Table
3
Friction Coefficients
Lateral load applied at the top
of beam support due to thermal expansion or contraction of pipe shall be
determined in accordance with Table 5, as follows:
Table 4
Lateral Loads
1.7.1 Sliding Thermal Force
The sliding supports supporting
heat exchanger or horizontal vessels for high-temperature service shall be
designed to be safe under the friction force due to thermal deformation of
equipment. This force shall be deemed as permanent load when the temperature
corresponds to the normal operating condition.
1.7.2 Anchor Force
For pipe racks and pipe supports,
pipe anchor force shall be calculated based on the thermal stress analysis of
the piping system. Deflection of the supports shall be considered.
The anchor force shall be deemed
as a permanent thermal load when the temperature corresponds to the normal
operating condition. When the temperature corresponds to the start-up
condition, such force shall be deemed as temporary thermal load.
The total design base shear need not exceed the
following:
1.8 Impact Load ( I )
For structures carrying live
loads, which induce impact, the live load shall be increased sufficiently.
Vertical, transverse, and
longitudinal impacts are normally not considered to act concurrently.
Impact load (vertical)
- Crane or monorail support : 25 %
Impact Load (lateral)
- Crane
runways or monorail :
Transversal :
20 % from max. lifted load
Longitudinal : 10 % from max. wheel loads
Design loading for road,
pavement, bridges, trenches, and underground installation subject to impact
load of truck or crane shall be increased 20% (vertical). Reciprocating
machinery or power driven unit shall be not less than 50%.
1.9 Dynamic Loads (J)
Vibration loads are defined as
those forces that are caused by vibrating machinery such as pumps, blowers,
fans and compressors. Including in this definition are surge forces similar to
those acting in surge vessels. All supports and foundation for
vibrating equipment shall be designed to limit vibrations to an acceptable
level.
1.10 Earth Pressure (H)
The earth pressure shall be
designed if has enough affecting to foundation design. The lateral soil pressure Ka, Kp,
and Ko shall be calculated base on soil investigation report.
1.11 Erection Loads
Erection loads are temporary
forces caused by erection of structures or equipments.
1.12 Wind Load (w)
Every Building, Structure,
component and cladding shall be designed to resist wind effects according to
UBC chapter 16. Wind speed of local data shall be
carried from local authority Climatology department, BMG (Badan Meterologi dan
Geofisika). The minimum wind speed at
standard height of 33 feet above ground shall be 70 miles per hour (112 km per
hour), UBC chapter 16. These higher values wind speed
data shall be the minimum basic wind speed loading data in the calculation
design.
Wind
stagnation pressure, q(s), shall be 61.52 kg/m²
(12.6 psf) according
to UBC Table 16-F. The wind loads shall be based on
terrain Exposure “ C “. Wind Importance Factor, Iw = 1.00
for all buildings, except Iw = 1.15 for essential facilities and hazardous
facilities as set forth in UBC Table 16-K. The product of the combined
height, exposure and guest factor coefficient, Ce (UBC Table 16-G), times the
stagnation pressure qs shall be taken as given in table bellow:
Table 5
Coefficient Ce
Equipment and structures shall be
designed to resist a design wind pressure, p = CeCqqsIw, where pressure
coefficient Cq, shall be obtained from Table 16-H of UBC.
Vertical and horizontal vessels
shall be designed to resist a design wind pressure, p = CeCqqsCpaIw, where Cq =
0.8. The projected area increased coefficient Cpa is given in Table 6 below:
Table 5
Coefficient Cpa
Note:
The value Cpa refers to
"Pressure Vessel Design Manual" by Moss, Dennis R.
In applying the wind pressure as
lateral force on the projected areas of vessel diameter, the projected area
increase factor Cpa, given above will provide as adequate allowance for
manholes, nozzles, piping, ladders, platforms and other attachments for normal
refinery-type vessels.
Wind load shall be separately
computed for all supported equipment, ladders, and stairs except for vessels
where projected area increase factors have already accounted for these items.
Gust response factor for a main
wind resisting system of flexible building, structures and vertical vessel with
height to diameter ratio equal or greater than 5:1 shall be calculated.
Calculations shall be based on a rational analysis that incorporates the
dynamic properties of the main wind forces resisting system. No reduction shall be made for
shielding effect of vessel or structure adjacent to the structure being
designed. Wind loads on open structures
shall be calculated using Cq from Table 16-H.5 of UBC, without regard for
shielding by other structural members.
The overturning moment due to
wind shall not exceed 2/3 of the resisting moment of the structure and
foundation during its lightest possible conditions after plant construction is
complete.
Wind and earthquake forces shall
not be assumed to act concurrently. Typical values of Cq can also be
referred to UBC Code (1997 Edition) Table H.
Wind force, F = p . Af ,
Where:
p = wind pressure
= CeCqqsIw
for equipment and structure
= CeCqqsCpaIw
for vertical and horizontal vessel
Af
= projection area normal to wind
Projection area Af = D x L Projection area Af = 1/4 x x D2
Note:
D = diameter of
pipe, vessel, or etc.
L
= length of pipe, vessel, or etc.
1.13 Rain Load (R)
The effect of pounding on
building and enclosed structure as produced by rain loads shall be assessed in
accordance with UBC Section 1605.6 and 2312.4.6 and the rain intensity for the
region. Rain intensity shall be collected from the nearest rainfall measurement
station, or from the Geophysical and Meteorological office for such area.
1.14 Seismic or Earthquake Load ( E )
Earthquake load shall be defined
as the static horizontal and vertical forces equivalent in their design effect
to the dynamic loads induced by ground motion during an earthquake.
All plant equipment and
structures shall be designed for earthquake forces in accordance with UBC 1997,
Chapter 16, as specified in Table 16-I and the following factors:
- Seismic
Zone : 4
- Seismic
Zone Factor : Z = 0.40
- Seismic
Importance Factor: I = 1.25 for all structures (UBC table 16-K)
- Soil
profile type : SE , Soft soil profile (UBC table 16-J)
Every structure, building and
foundation shall be designed to resist the effects of overturning moments
caused by earthquake forces as specified in UBC 1997, Sections 1630.8 and 1809.
The overturning moment due to seismic shall not exceed 2/3 of the resisting
moment. Providing soil-bearing stresses are within allowable, seismic
overturning stability is satisfied.
Tall structures and structures
having stiffness, weight and geometric irregularities as defined in UBC Section
1629.8.4 shall be analyzed using dynamic lateral force procedures of UBC
Section 1631, including appropriate scaling of the results.
Design base shear. Total design
base shear in a given direction shall be determined from the following formula:
(UBC section 1630.2.1)
The total design base shear shall
be less than the following:
V = 0.11 Ca I W
For Seismic zone 4, the total
base shear shall also not be less than the
following:
For all buildings, the value T
may be approximate from the following:
Where
V =
|
Total lateral force at the base
|
Cv =
|
Seismic coefficient, in table 16-R
|
Ca =
|
Seismic coefficient, in table 16-Q
|
Ct =
|
Numerical coefficient
|
R =
|
Numerical coefficient representative of the inherent overstrength and
global ductility capacity of lateral-force-resisting systems, table 16-N or 16-P
|
W =
|
The total seismic dead load defined UBC in section 1630.1.1.
|
T =
|
Elastic fundamental period of vibration, in seconds of the structure in
the direction under consideration.
|
I =
|
Importance factor given in table 16-K UBC 1997
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2.0 LOADING COMBINATION
2.1 General
Structures, buildings, and
foundations shall be designed to have design strengths at least equal to the
required strength calculated for the following loading combinations.
Factor loading combination shall
be used for concrete structure and foundation. Un-factor loading combination
shall be used for steel structure and stability check of foundation. Factor and
un-factor loading combination shall be considered for permanent and temporary
conditions.
2.2 Loading Combination
Load prescribed here to fore
shall be considered to act in the following combination adjusted by multiplying
a load combination (LC) probability factor whichever produces the most
unfavorable effects in the building, foundation, or structure member concrete.
2.2.1 Steel Structure Design.
2.2.2 Concrete Structure and Foundation
2.2.3 Foundation Stability Check
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