TYPICAL STRUCTURE UPLIFT DERIVATITYPICAL STRUCTURE UPLIFT DERIVATI OO NN

TYPICAL STRUCTURE UPLIFT DERIVATI

N N

F i g u r e 4 - 1 F i g u r e 4 - 1

4-8 4-8

water impinging on the sides of the pumping station are computed water impinging on the sides of the pumping station are computed in a

in accccordordancance wie with tth the phe provrovisiisions ons of Eof EM 11M 1110-10-2-22-2502502.. For For strstrucuc- -tures having sloping exterior walls, or footings extending

tures having sloping exterior walls, or footings extending outside the structure walls,

outside the structure walls, the force wedges used for structurethe force wedges used for structure stability analysis will originate at a vertical plane projecting stability analysis will originate at a vertical plane projecting upward from the outer edge of the structure footing or wall at calcu-lated by the Westergaard approximation.

lated by the Westergaard approximation.

e. Wind Loading.Wind Loading. Wind loads should be applied accordingWind loads should be applied according to the provisions of ANSI A58.1.

f. Floor Loads.Floor Loads. The structural support system for theThe structural support system for the operating floor should be designed for dead loads including the

placed on the floor. The machinery loads,The machinery loads, for both service andfor both service and maintenance conditions,

maintenance conditions, should be furnished by the pump designer.should be furnished by the pump designer.

The service loads will include the machinery weight plus the

downward hydraulic thrust under operating conditions in addition downward hydraulic thrust under operating conditions in addition to t station should be designed using the applicable minimum dead

station should be designed using the applicable minimum dead loa allowed only where the member under consideration supports more allowed only where the member under consideration supports more than 500 square feet of slab.

than 500 square feet of slab.

4-9 4-9

TABLE 4-1 TABLE 4-1

MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS

LB/SO FT

Forebay Deck (Outdoor Pumping Station)...

Forebay Deck (Outdoor Pumping Station)... 300 or H20**300 or H20**

Electrical Substation Deck

Electrical Substation Deck ... 200200 Forebay Deck Grating...

Forebay Deck Grating... 300 or H20**300 or H20**

Pumping Station Access...

Pumping Station Access... 300 or H20**300 or H20**

* Operating floor must be designed to allow placement of the

* Operating floor must be designed to allow placement of the heaviest machinery piece anywhere on the floor unless specific heaviest machinery piece anywhere on the floor unless specific areas are designated for this purpose.

areas are designated for this purpose.

** Use whichever is more critical and where mobile cranes might

** Use whichever is more critical and where mobile cranes might be used, applicable loading including impact loads should be

be used, applicable loading including impact loads should be applied if more critical than those listed.

applied if more critical than those listed.

g. Stairway and Landing Loads.Stairway and Landing Loads. Stairways and landingsStairways and landings should be designed using the live load given in Table 4-1 unless

sidered. Snow loads should be determined and distributed accord-Snow loads should be determined and distributed accord-ing to the provisions of ANSI A58.1.

per square foot of horizontal projection.

i. impact (for power operated cranes), longitudinal forces, and impact (for power operated cranes), longitudinal forces, and lateral forces. resulting longitudinal forces should be provided for in the resulting longitudinal forces should be provided for in the design of the crane runway.

design of the crane runway. Acceptable allowances for impact,Acceptable allowances for impact, longitudinal forces and lateral forces are as follows:

longitudinal forces and lateral forces are as follows:

Impact...

Longitudinal forces... 10% of maximum vertical wheel10% of maximum vertical wheel loads (applied at top of rail).

j. Moving Concentrated Live Loads.Moving Concentrated Live Loads. Medium to largeMedium to large

pumping stations may be designed with forebay and discharge decks equipment (truck crane, tractor trailer, etc.) fully loaded.

equipment (truck crane, tractor trailer, etc.) fully loaded.

Load distribution for truck loading should be made in accordance Load distribution for truck loading should be made in accordance with AASHTO

with AASHTO "Standard Specification for Highway Bridges.""Standard Specification for Highway Bridges." It mayIt may be advisable to place load limit signs at the entrances to these

4-4. Loading Conditions and Design Criteria.Loading Conditions and Design Criteria. The followingThe following loading conditions should not be regarded as a comprehensive loading conditions should not be regarded as a comprehensive list.

list. In many instances,In many instances, unique site specific factors such asunique site specific factors such as water conditions,

water conditions, station arrangement and location, pump type,station arrangement and location, pump type, 4-11

4-11

pump and discharge arrangement, etc. will dictate modification of pump and discharge arrangement, etc. will dictate modification of some of these loading conditions to fit the specific site.

some of these loading conditions to fit the specific site. TheThe conditions described should be used as a guide to the range of conditions described should be used as a guide to the range of stability analyses required.

stability analyses required. The external structure forces andThe external structure forces and distributed loads should not be factored for stability analysis, distributed loads should not be factored for stability analysis, but may be subsequently factored when applied to the concrete but may be subsequently factored when applied to the concrete members of the structure for use

members of the structure for use in reinforcement design inin reinforcement design in accordance with EM 1110-2-2502.

accordance with EM 1110-2-2502. Design of the miscellaneousDesign of the miscellaneous structures associated with the pumping station (wing walls, structures associated with the pumping station (wing walls, headwalls,

headwalls, discharge piping, culverts, gate structures, etc.)discharge piping, culverts, gate structures, etc.) should be based on the applicable design water levels, earth conjunction with the basic loading conditions as applicable conjunction with the basic loading conditions as applicable depending on the meteorological condition at the site.

depending on the meteorological condition at the site. StabilityStability and stress criteria vary according to the nature of the loading and stress criteria vary according to the nature of the loading con

conditditioion impn imposeosed on td on the she strutructucturesres.. For tFor the phe purpurpose ose of crof criteiteririaa application,

application, there are three categories of loading conditions;there are three categories of loading conditions;

usual,

usual, unusual,unusual, and extreme.and extreme. Usual conditions are defined asUsual conditions are defined as

those related to the primary function of a structure and expected those related to the primary function of a structure and expected to occur during its life.

to occur during its life. For pumping stations, all of theFor pumping stations, all of the operating flood conditions should be considered usual.

operating flood conditions should be considered usual. UnusualUnusual conditions are those which are of infrequent occurrence or short conditions are those which are of infrequent occurrence or short duration.

duration. Construction condition,Construction condition, maximum design water levelmaximum design water level condition,

condition, maintenance conditions,maintenance conditions, rapid drawdown condition, andrapid drawdown condition, and blocked trash rack condition are examples of unusual loading for blocked trash rack condition are examples of unusual loading for pumping stations.

pumping stations. Extreme conditions are those whose occurrenceExtreme conditions are those whose occurrence is highly improbable and are regarded as emergencies, such as is highly improbable and are regarded as emergencies, such as those associated with major accidents or natural disasters.

those associated with major accidents or natural disasters. ForFor pumping stations, pumping station inundated and earthquake

pumping stations, pumping station inundated and earthquake co

condinditiotions sns shohould uld be cbe consonsideidered red exextretreme.me. ThThe base basic loic loadiadingng conditions for design and their categories are listed below.

conditions for design and their categories are listed below.

a. Construction Condition.Construction Condition. Pumping station complete withPumping station complete with and without fill in place, no water loads.

and without fill in place, no water loads. Unusual.Unusual.

b. Normal Operating Condition.Normal Operating Condition. Plant operating to dis-Plant operating to dis-charge routine local floods over a range of exterior flood levels

start elevation or maximum pump level. Usual.Usual.

d. Pump Stop Condition.Pump Stop Condition. Water below pump start elevationWater below pump start elevation 4-12

4-12

on intake side,

on intake side, levee design flood on discharge side.levee design flood on discharge side. UsualUsual e.

e. High Head Condition.High Head Condition. Maximum design water levelMaximum design water level outside protection line,

outside protection line, minimum pumping level inside.minimum pumping level inside. Usual.Usual.

f. Maximum Design Water Level Condition.Maximum Design Water Level Condition. Maximum operat-Maximum operat-ing floods both inside and outside protection line, maximum pump ing floods both inside and outside protection line, maximum pump thru

thrust. st. UnusUnusual.ual.

g. Maintenance Conditions.Maintenance Conditions. Maximum design water levelMaximum design water level inside with one, more,

inside with one, more, or all intake bays unwatered.or all intake bays unwatered. Unusual.Unusual.

h. Rapid Drawdown Condition.Rapid Drawdown Condition. Water at pump stop eleva-Water at pump stop eleva-tion,

tion, sumps unwatered.sumps unwatered. (Apply to stations inside protection line(Apply to stations inside protection line only.)

only.) UnusualUnusual i.

i. Blocked Trash Rack Condition.Blocked Trash Rack Condition. Five foot head differen-Five foot head differen-tial across trashracks.

tial across trashracks. Unusual.Unusual.

j. Pumping Station Inundated.Pumping Station Inundated. Maximum flood levels insideMaximum flood levels inside and outside protection line,

and outside protection line, pumping station inoperative, founda-pumping station inoperative, founda-tion drains inoperative, protecfounda-tion line intact.

tion drains inoperative, protection line intact. Extreme.Extreme.

k. Earthquake Conditions.Earthquake Conditions. Earthquake loading combinedEarthquake loading combined with normal operating condition.

with normal operating condition. ExtremeExtreme 4-5.

4-5. Stability.Stability. Analyses should be made for stability ofAnalyses should be made for stability of

structures against overturning, sliding, flotation, and structures against overturning, sliding, flotation, and founda-tion pressure.

tion pressure.

a. Overturninq.Overturninq. For overturning stability, all structuresFor overturning stability, all structures should meet the criteria given in Table 4-2 for percent of base should meet the criteria given in Table 4-2 for percent of base in compression.

in compression.

b. Sliding.Sliding. The resistance to sliding under variousThe resistance to sliding under various

loading conditions will be analyzed according to EM 1110-2-2502.

The result of this analysis is expressed in terms of a sliding The result of this analysis is expressed in terms of a sliding safety factor which is the ratio between the total shear strength safety factor which is the ratio between the total shear strength available in the soil-structure wedge system and the applied

available in the soil-structure wedge system and the applied sh

shear ear strstressess.. The mThe miniinimum smum slidliding sing safeafety faty factctors fors for vaor varioriousus types of loading are shown in Table 4-2.

types of loading are shown in Table 4-2.

C. Flotation.Flotation. The analysis of structures for stabilityThe analysis of structures for stability against flotation should be performed in accordance with the against flotation should be performed in accordance with the pr

Table 4-2 Table 4-2

STABILITY CRITERIA FOR PUMPING STATIONS STABILITY CRITERIA FOR PUMPING STATIONS

Aspect

d. Foundation Pressure.Foundation Pressure. In conjunction with the overturn-In conjunction with the overturn-ing analysis,

ing analysis, the base pressures and foundation pressures forthe base pressures and foundation pressures for each loading condition should be calculated and the maximum each loading condition should be calculated and the maximum

values compared with the maximum allowable values determined for values compared with the maximum allowable values determined for the foundation material.

the foundation material. These maximum allowables should not beThese maximum allowables should not be exc

exceedeeded ed fofor ar any ny loloadiading ng concondiditiotion.n. ThThe alloe allowabwable valle valueues shous shouldld be coordinated between the geotechnical and structural engineers.

be coordinated between the geotechnical and structural engineers.

4-6.

4-6. Design Stresses.Design Stresses. Allowable working stresses for structuralAllowable working stresses for structural materials will generally be as prescribed in EM 1110-1-2101,

materials will generally be as prescribed in EM 1110-1-2101,

except that reinforced concrete structures should be designed in except that reinforced concrete structures should be designed in accordance with the strength design method given in EM accordance with the strength design method given in EM 1110-2-2502.

2502. Working stresses for use in proportioning masonry struc-Working stresses for use in proportioning masonry struc-tural components should be taken from TM 5-809-3.

tural components should be taken from TM 5-809-3. For earthquakeFor earthquake loading, design stresses should be evaluated in accordance with loading, design stresses should be evaluated in accordance with guidance given in ER 1110-2-1806 and TM 5-809-10.

effects, and economics.and economics. There are two general categories ofThere are two general categories of disc in significant cost savings compared to the over-the-protection in significant cost savings compared to the over-the-protection line type.

continuous coconcrncrete bete bededdinding,g, or othor other apper approvroved meaed meansns.. ThThee principal loads imposed on the pipe are positive and negative principal loads imposed on the pipe are positive and negative hydraulic pressures and external compressive pressure from fill hydraulic pressures and external compressive pressure from fill material and vehicular surcharge.

material and vehicular surcharge. EM 1110-2-2902 contains proce-EM 1110-2-2902 contains proce-dures for the design of conduits under embankment and backfill dures for the design of conduits under embankment and backfill loading.

loading. Embankment settlement should be considered in theEmbankment settlement should be considered in the design of the pipe joints.

design of the pipe joints. Over-the-levee type pipes are some-Over-the-levee type pipes are some-times designed as siphons,

times designed as siphons, using the pumps to establish flow.using the pumps to establish flow.

This introduces an additional design loading consideration. At This introduces an additional design loading consideration. At the levee crest,

tained in EM 1110-2-3105. Discharge pipes passing through orDischarge pipes passing through or under the protection line are pressure pipes and the internal under the protection line are pressure pipes and the internal hydraulic pressures are

hydraulic pressures are therefore greater than for the over-the--therefore greater than for the over-the--protection line type. the integrity of the embankment.

the integrity of the embankment. The materials used in theseThe materials used in these pipes are ductile iron, steel,

pipes are ductile iron, steel, concrete pressure pipe, andconcrete pressure pipe, and cast-in-place reinforced concrete.

cast-in-place reinforced concrete. To prevent leakage, steel andTo prevent leakage, steel and ductile iron pipe should be joined with flexible, watertight

ductile iron pipe should be joined with flexible, watertight couplings,

couplings, and concrete pipe should have alignment collars andand concrete pipe should have alignment collars and waterstops at each joint.

waterstops at each joint. Materials used for discharge pipingMaterials used for discharge piping sho

b. Discharge Conduit Gates.Discharge Conduit Gates. A pressure discharge conduitA pressure discharge conduit from a pumping station through the protection line must be

usually be in a well integral with the floodwall.

Well type gate structures should be constructed of reinforced Well type gate structures should be constructed of reinforced concrete and designed in accordance with strength design concrete and designed in accordance with strength design provi-sio

will experience fill loading, uplift and vertical water loads,uplift and vertical water loads, an to withstand gate operating forces.

to withstand gate operating forces. See EM 1110-2-3105 forSee EM 1110-2-3105 for further discussion of forces on the gate structure induced by further discussion of forces on the gate structure induced by gate operation.

gate operation. In areas of high seismicity, defensive structur-In areas of high seismicity, defensive structur-al layout may dictate that the concrete mass extending above the al layout may dictate that the concrete mass extending above the ground line be kept to a minimum.

ground line be kept to a minimum. Restriction of the gateRestriction of the gate

structure projection above the ground line might also be of value

economic, and technical considerations.and technical considerations.

slots near the intake face of the substructure. TrashracksTrashracks should be designed for a minimum of 5 feet of head differential installations some positive means of trash removal should be installations some positive means of trash removal should be provided.

provided. both trashracks and trash raking equipment, durability under

both trashracks and trash raking equipment, durability under adverse operating conditions and harsh environment must be adverse operating conditions and harsh environment must be considered.

considered. These items should be designed to function depend-These items should be designed to function depend-ably with a minimum of maintenance over the life of the station.

conventional trash raking equipment. The method of trash removalThe method of trash removal and handling should be coordinated early in the design process, placements except as required near the concrete surfaces to

placements except as required near the concrete surfaces to pr

preveevent nt spaspallilling ng of of ththe ce cornornersers.. ThiThis can us can usuasualllly be coy be contntrolrolledled by using V-grooves at monolith joints.

by using V-grooves at monolith joints. However,However, in some casesin some cases such as a thin wall section abutting the end wall of the pumping such as a thin wall section abutting the end wall of the pumping station,

station, deeper separation may be desirable.deeper separation may be desirable.

g. Construction Joints.Construction Joints. Reinforced concrete portions ofReinforced concrete portions of pumping stations may be placed in segments, separated either pumping stations may be placed in segments, separated either vertically or horizontally by construction joints.

vertically or horizontally by construction joints. These jointsThese joints are meant only to facilitate the construction process by dividing

placements, construction joints can also serve to minimize crackconstruction joints can also serve to minimize crack formation.

formation. Reinforcing steel should pass through these joints,Reinforcing steel should pass through these joints, and surfaces should be cleaned and scoured as necessary to

and surfaces should be cleaned and scoured as necessary to provide good bond between the concrete placements.

In document Structural And Architectural Design Of Pumping Stations (Page 28-72)