reinforced concrete designers handbook 10th edition reynolds steedman 2 part print

118 Loads

characteristic load and an alternative concentrated charac-teristic load as given in Table 11. For the parking of heaviervehicles and for repair workshops, greater loading and themost adverse arrangement of actual wheel loads must betaken into account.

9.2.6 Overhead travelling cranes

To allow for vibration, acceleration and deceleration, slipp-ing of slings, and impact of wheels, maximum static wheelloads (see Table 12 for typical loads) of simple electricoverhead travelling cranes should be increased by 25%.Braking or travelling under power produces in the rail-beama horizontal thrust which is transferred to the supports. Thetraversing of the crane and load produces a horizontal thrusttransversely to the rail-beam. Therefore the additional forcesacting on the supporting structure when the crane is movingare (a) a horizontal force acting transversely to the rail andequal to 10% of the weight of the crab and the load lifted, itbeing assumed that the force is equally divided between thetwo rails; (b) a horizontal force acting along each rail andequal to 5% of the greatest static wheel load that can act onthe rail. The forces (a) and (b) are not considered to actsimultaneously, but the effect of each must be combined withthat of the increased maximum vertical wheel loads.

For a crane operated by hand, the vertical wheel loadsneed be increased by only 10%; for force (a) the proportion ofthe weight of crab and load can be 5%. Force (b) is the samefor hand as for electrically operated cranes.

The foregoing requirements are in accordance withBS6399: Part 1. Gantry cranes other than simple typesshould be considered individually.

9.2.7 Structures supporting lifts

The effect of acceleration must be considered in addition tothe static loads when calculating the load due to lifts andsimilar machinery. If a net static load of Fd is subject to anacceleration of a metres per second per second (mis2) theload on the supporting structure is approximately Fm = Fa X

(1 + 0.098a). If a is in ft/s2, Fm = Fd(l + 0.03a) approximately.The average acceleration of a passenger lift may be about0.6m/s2 or 2ft/s2, but the maximum acceleration will beconsiderably greater. An equivalent load of 2Fd should betaken as the minimum to allow for dynamic effects. The loadfor which the supports of a lift and similar structures aredesigned should be related to the total load on the ropes. Ifthe latter is Fm and the ropes have an overall factor of safetyof 10, the service load on the supports should be not less than2.SFm to ensure that a structure, if designed for a nominaloverall factor of safety of 4, is as strong as the ropes.

The requirements of BS2655 (see Table 12) are that thesupporting structure should be designed for twice the totalload suspended from the beams when the lift is at rest.Reinforced concrete beams should be designed for this loadwith an overall factor of safety of 7, and the deflection underthis load should not exceed 1/1500 of the span.

9.2.8 Industrial plant

Typical static weights of screening plant, conveyors and

conveyor gantries are given in Table 12 (in SI and imperialunits). The supports for such machines and for all industrialmachinery should be designed for the static weight plus anallowance for dynamic effects; i.e. vibration, impact etc.

9.2.9 Pit-head frames

A pit-head frame of the type that is common at coal minesand similar may be subjected to the following loads. (Thesenotes do not apply to the direct vertical winding type of pit-head tower.)

Dead loads. The dead loads include the weights of (1) theframe and any stairs, housings, lifting beams etc. attached toit; (2) winding pulleys, pulley-bearings, pedestals etc.;(3) guide and rubbing ropes plus 50% for vibration.

Imposed loads. The imposed loads are the resultants of thetensions in the ropes passing over the pulleys and (unlessdescribed otherwise) are transmitted to the frame throughthe pulley bearings and may be due to the followingconditions. (a) Retarding of descending cage when near thebottom of the shaft; this force is the sum of the net weight ofthe cage, load and rope, and should be doubled to allow fordeceleration, shock and vibration. (b) Force due tooverwinding the cage which is then dropped on to theoverwind platform; this force acts only on the platform (andnot at the pulley bearings) and is the sum of the net weights ofthe cage and attachments and the load in the cage, which sumshould be doubled to allow for impact. (c) Force causingrope to break due to cage sticking in shaft or other causes; theforce in the rope just before breaking is the tensile strength ofthe rope. (d) Tension in rope when winding up a loaded cage.

Combined loads. For a frame carrying one pulley, theconditions to be designed for are the total dead loadcombined with either imposed load (a), (b), (c) or (d).Generally condition (c) gives the most adverse effects, but it ispermissible in this case to design using service stresses of say,double the ordinary permissible service stresses because ofthe short duration of the maximum force. The procedurewould be to design the frame for service dead load plus half offorce (c) and adopt the ordinary service stresses. If the framecarries two pulleys, the conditions to be investigated are:dead load plus (a) on one rope and (d) on the other (this is theordinary working condition); dead load plus (a) on one ropeand overwind (b) on the other; and dead load plus (a) on onerope and breaking force (c) on the other rope (this isgenerally the worst case: force (c) can be halved as explainedfor a single-pulley frame).

The weights of the ropes, cages etc. and the strength of theropes would be obtained for any particular pit-head framefrom the mining authorities, and they vary too greatly fortypical values to be of any use.

9.2.10 Railway bridges

As stated in section 2.4.6, standard railway loading through-out Europe (including the UK) consists of two types, RU andRL. The former, which is illustrated in Table 9, covers allcombinations of main-line locomotives and rolling stock. RL

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Weights of vehicles

Type0a000

Ea

Heavy goods2-10-0

+L 56ff

m

plus tender

8Express Mixed traffic Shunter

0-6-04-6-2+ooe.e4

5911 3m

plus tender

2-6-4+G.GøO 32ft6in

(tank)4.7m(tank)

Maximum kNaxle load tons

Total weight kNengine+tender

1385139

1564157

86787

55856

15415.5

21922

17918

18919

y

Type

-__Total weight kN

tons

Maximum kN

Express Mixed traffic

1-co-co-i - ao-BOooi

21.2m 20.7m 15.2m

1320 to 1380 1000 to 1280 680 to 770

132 to 138 100 to 128 68 to 77

20020

Shunters

0-6-0 0-4-0

7.9m 6.1 m

300 to 550 220 to 3601500 standard)

30 to 55 22 to 36(50 standard)100 to 170 110 to 180IOta 17 11 to 18

axle load tons 17 to 22 to

TypeC0a

a

ECa0

Data apply tostandard gaugerolling stockon BritishRailwaysexcept(steamlocomotivesnot now ingeneral use)

Maximum axleload 200 kNor 20 tons onrails weighing500kg/rn or95—100 Ib/yd,oror 22.5 tonsformulticylinderlocomotives.

560kN 56 ton ore wagons

5ft6in

____________5ft6in

m

m

ft 11 inOverall width

Total weightfkN

tons

kN ton wagons

6 1 6 ft

1.83m7.32m

2.44 m8 ft

35035

85085

Colliery tubs and minecars 610 mm or 690mm(2ft or 2ft3in) gauge

Minimum turningradius 3,66m or 121t

1.07 m3 ft 6 in

7.5 to IS0.75 to 1.5

21221.25

'75I

3.75 to 7.50.375 to 0.75

Street tram car Road rollers Articulated tipping —

Tractor Trailer Tractor Trailer(eight wheeled) Steam Diesel

Type of vehicle 00 003.05m

200kNor 20 tons

49ft

2.74m

lOOkNor 10 tons

A B 41t C A B C C CI 1.35m Iø'.I 8ff

H32ft 32ft9.75m 9.75m

A Ic loadsX kNDriving Pony75 37

DrivingRoller wheels80 120

DrivingRoller wheels50 50

5

A B C60 80 80

6 8 8

A B C60 80 60

6 8 6tons 7.5 3.75 8 12 5

320

T al I dkN

ot weight a en tons224

22.5200

20

10010

30030

2.44m

32

2.44m. 2.74m l.68m

Overall width — 9 ft 5 ft 6 in 8 ft 8 ft

— l.435m 1.75m l.37mGauge 4 ft in 5 ft 9 in 4ft 6 in —

driving wheelsi

driving wheels

Width Length Axle loads

Vehicle m ft in Vehicle m ft in Description kN tons

Department Locomotive 2.75 9 Rigid vehicle 11.0 36 1 One-wheel axle 45(50) 4,5(5)

of Transport Heavy motor car Articulated* 13.0 42 Single two-wheel

regulations and other vehicles 2.50 8 21 Trailers* 7.0 22 axle (90(100) 9(10)

Trailer 2.30* 7 6* Vehicle and trailer* 18.0 59

Maximum —_______________________dimensionsand * Unless drawn by locomotive, * No specified limit if constructed Weights in brackets apply if wheels

axle loads heavy motor car or tractor: and normally used to carry are fitted with twin tyres at not less

otherwise projection on either indivisible loads of exceptional than 300mm or 12 in centres.

side of drawing vehick not lengthgreater than 300mm or 12 in

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Loads on bridges: BS5400—1 ULTIMATE VALUESVALUES OF PARTIAL FACTOR OF SAFETY CORRESPONDING TO LOADING CONDITION I

Type of loadingLimit-state considered*

Ultimate Serviceability

Dead load

From structural elements

Steelwork1.05

(1.10)ri nni

1.00

Concrete1.15

(1.20)[1.00]

1.00

.

From all materials other than structural elements 1.75{l.20}

1.20{l.00}

Earth pressureDue to retained material and/or surcharge 1.50 1.00

Due to relieving effects 1.00 —

Imposed load

On highway bridgesDue to HA loading alone 1.50 1.20

Due to HB loading with or without HA loading 1.30 1.10

On footbridges and cycle track bridges 1.50 1.00

On railway bridges 1.40 1.00

*Increased values indicated thus (1.10) apply when dead loads are not properly assessed.Reduced values indicated thus [1.00] apply where these cause a more severe total effect.Reduced values indicated thus { 1.20} may be adopted only where approved by appropriate authority.

IMPOSED LOADS

Loading Notes

Highwaybridges

HABasic

Uniform load as follows:

Loaded length 1(m): Load (kN/m of lane):

Up to 30 303Oto 379 151 (1//)0475More than 379 9

PLUS a knife-edge load of 1 2OkN per lane

No dispersal of load beneathcontact area may be considered

Knife-edge load arranged to havemost severe effect

Alternative Single 100 kN load having circular (340mm dia.) or square (300 mm)contact area transmitting effective pressure of 1.1 kN/mm2

Loads may be dispersed asindicated on Table 10

—

HB

Due to vehicle as follows:Load per wheel = 2500/ newtons (where Limit of vehiclej=number of units of HB load)

1

11 m

I

—.O.2m.J

(whichever has most criticaleffect on member being considered)

Loads may be dispersed asindicated on Table 10

I unit represents 4 tonnes grossladen weight of vehicle

HC See section 2.4.6

Footbridges and cycle trackbridges

Loaded length 1(m): Load (kN/m2):

Upto 30 5Exceeding 30 25(1/1)0475*

(

*But not less than 1.5 kN/m2

Railway bridges (RU loading)

Due to train of loads as follows:

250kN 250kN 2SOkN 250kN

rn_fi.6 rn_fl .6 mJO.8rr

Note: for details of loads due to wind, braking, traction, lurching, nosing, centrifugal force etc. see BS5400

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Loads on bridges: BSS400—2FORMULAE FOR DISPERSAL OF LOAD

ULTIMATE VALUES 1 0Material

Shape ofloaded area Formula Notation

Concrete

Square=

2500j

+ 2W]2

f

h'

pressure in N/mm2

depth below surface atwhich load is applied.in mm

slab

Circular=

l000Qj

+ 2h']2n J number of units of HBload (to consideralternative HA load,take j=4)

AsphaltSquare f =

2500j

,J(2500j/l.l) + h']2II

etc.surfacing

Circular j=

l0000j

+ h']2ir

Load = 1.1 N/mm2

Third lane (if any)

Any other lanes

Loading arrangement

_________

2 3 4

HA only HB with or without HA

Notes:I. Actual lanes designated first, second etc. should be chosen so as to

induce most severe conditions (but if HB load straddles two lanes, thesemust adjoin).

2. Where HB loading occurs, no HA load need be considered in that lanewithin a distance of 25 m from the limits of the HB vehicle.

(HA3. indicates HB load straddling adjoining lanes with remainder

(HAof both lanes loaded with full HA loading.

(HAindicates HR load straddling both lanes with remainder of

(HA/3one lane loaded with full HA load and other with HA/3 load.

Dispersal of loadconcrete slab

.1/6 load transmittedby this sleeper

Dispersal of load throughasphalt etc. surfacing

I.. over which sleeper

__________

transmits load to ballast*aorDIspersal of concentrated load beneath sleepers 0.4 m

DETERMINATION OF LANE ARRANGEMENT DISPOSITION OF LOADS IN BANDS

First lane

Second lane

Total carriagewaywidth

Lane arrangement

Up to 4.6 mDivide each carriageway by 3m. Loadingon any fractional lane is proportional tothat on a complete lane.

Exceeding 4.6 m

Divide each carriageway into least possibleintegral number of lanes of equal width bydividing by 3.8 m and rounding up to nextwhole number.

SURCHARGE ON RETAINING STRUCTURE

HA load lOkN/m2

HBload (j—5)/2kN/m2 wherej=number of units of HBload

RU load 50 kN/m2 on areas occupied by tracks

HA

HA

HA/3

HA/3

HB

HA

HA/3

HA/3

(HA (HA

HA

HA/3

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122 Loads

loading is less severe and is only applicable for rapid-transitpassenger systems where main-line equipment cannot ope-rate: brief details of this loading are given in section 2.4.6.

In addition to the primary loads considered above,secondary live loading due to dynamic effects (such as impactand oscillation), nosing, lurching, centrifugal force, acceler-ation and braking must be taken into account. For detailsreference should be made to clause 8 of BS5400: Part 2.

9.2.11 Aircraft runways

The design of a pavement for an aircraft runway or aprondepends on the amount, frequency and distribution ofloading from the aircraft, the flexural strength of the slab, thesupport provided by the subgrade and the particular type offacility (e.g. runway, apron etc.) being designed. In currentdesign practice, the loading data produced by the aircraftmanufacturers are used to prepare design charts giving theresulting flexural stresses in slabs of various thicknesses bymeans of computer programs or influence charts: for furtherdetails see ref. 132.

Designers of such pavements must anticipate future as wellas present loading requirements.

Experience obtained from designing runways for heavyUS military aircraft which are supported on isolated groupsof up to four wheels (the gross tyre weight of a B52 bomberexceeds 22680kg) has confirmed the validity of current

design methods. However, it seems possible that futureheavier aircraft may utilize undercarriage arrangements inwhich larger numbers of wheels act together, with additionalincreases in the tyre contact area. The deflection of, andsupport provided beneath, slabs carrying such large loadedareas then become increasingly important and may requiregreater consideration in future.

For information, some details regarding the Boeing 747,the largest commercial aircraft currently operating, are asfollows: overall width 59.64m; length 70.51 m; height 19.33 m;gross weight at take-off 371945kg; capacity up to 550passengers; undercarriage consists of sixteen wheels arran-ged as four 4-wheel bogies; maximum weight per tyre20 640 kg.

9.2.12 Dispersion of wheel loads

Rules for the dispersion of road and rail wheel loads onconcrete slabs are shown on Tables 10 and 11. Note that therequirements of BS5400 (Table 10) differ from those thathave been generally adopted in the past (Table 11).

9.2.13 Effects of wind

The data in Tables 13 to 15 are based on BS3: Chapter V:Part 2: 1972, and a description of the use of these tables isgiven in section 2.7,

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Imposed toads from vehicles

Loadedlength

(m)

HA uniform loading forreinforced concreteslabs on steel beamsEquivalent

HA uniformloading(kN/m2)

Longitudinal(kN/m2)

11HA uniform loading for

reinforced concreteslabs on steel beams

T

1.01.52.02.53.03.54,04.55.05.56.0

6.5 to 23253050100

106.259.842.231928.224.121.619.016.413.711.010.510.39.67.65.3

Transverse(kN/m2)

94.037.824.218.415.012.911.410.610.510.510.510.510.39.67.65.3

106.259.835.724.019.516.414.012.111.310.710.510.510.39.67.65.3

U)

0U)I-,

S..

0.E

•0

I-

II-Ce

5-C)0.

•0Ce0

5-.Ce

Ce

rtjU)C)so

-uI--c

-uCe0

Loadedlength

(ft)

3

45

67

8

910

12141618

20 to 7580

100200

EquivalentHA uniform

loading(Ib/ft2)

24201 7001 225966828725644

487421355288220216200142

Longitudinal(lb/ft2)

24201 7001225

885655520452400325270240225220216200142

ransverse(lb/ft2)

22701180

770580460390340310260230220220220216200142

7Smm.ø$ 375mm

Direction900mm 3ft travelH

-uCe0C)C)

iBm

Load on each contactarea 112.5kNor 11.25 tons

6.1 m 1.8m

75 mm-u900mm Ii 3inl Directionmrnl_f_

900mm

—

travelCeO 4--- *- 3ttmm

20 ft

Load on each contactarea= 112.5kNor 11,25 tons

Dispersion atis allowed

from eachcontact area.

Specified loadsinclude anallowance forimpact.

With HB andtwin-wheelloading, stressespermissible maybe increasedby

C)Cau

00

Imposed loads per BS6399: Part IConcentrated load usually assumed to act on 300mm or 12 in square

Uniformly distributed Concentrated

lbkN/m2 lb/ft2 kN

Footbridgesbetweenbuildings

Loading from crowds only 4.0 83.5 4.5 1012

Loadingexceedingcrowds(e.g. trolleysetc.) 5.0 104.5 4.5 1012

Grandstands 5.0 104.5 4.5 1012

C)Ca

Floors,ramps,drivewaysetc.

Parking only: vehicles 25 kN or 2.5 tons 2.5 52.2 9.0 2023

Parking of vehicles> 25 kN or 2.5 tonsRepairworkshops 5.0 104.5 9.0

4.5

2023

1012

&0

At ground floorsof buildings

Pedestriantrafficonly 4.0 83.5

No obstruction to vehicular traffic 5.0 104.5 9.0 2023

Road bridgesDTp

Where vehicles can mount footpathConcentrated load of 40 kN or 4 tons

(including impact) in any position

U)-uCe0C)C)

5—0

0U)

Wheels on ballasted rail tracks on concrete slabWheels on concrete slab

F=wheel load

dLrY)1)

Surfacing //a

=

+

I /i '.

/ a contact length

Blb width of tyre

I (=7510450mm or3to l8in)I /I / '. Wheel-load dispersion area = A x B

C overall width (two sleepers)1 length of sleeperAxle-load dispersion area = A x B

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Reduction of uniformlydistributed imposed loadsspecified onTables 6 and 7(per BS6399:Part 1)

ColumnsPiersWallsFoundations

Number of floors (including roof)supported by member

Reductions apply to all buildings except warehouses and other stores, garages andoffice areas used for storage or filing

Applicable also to factories, workshops etc. Design for imposed load not less than5 kN/m2 or 104 lb/ft2 provided the reduced load is not less than S kN/m2 or 104 lb/ft2

No reduction is to be made for machinery or other particular loads

Maximum static load on pair of wheelskN tons

Vertical load Increase static wheel load by 25% 10%

Transverse to rail:proportion of weights of crab plus load

Longitudinally (along rail):proportion of max. static wheel loads

Imposed loads: miscellaneous 12Reduction of load

on all floors

2

Beams

5to More10 than 10

Single span supporting not lessthan 40 m2 or 430 ft2 at same general level

0 10% 20% 30% 40% 50%max.

Multiply load by (1.05— A/800), whereA = area in m2. Maximum reduction = 25%

This reduction or reduction for columns etc. can be made, whichever gives the greatestreduction

Applicability

MISCELLANEOUS IMPOSED LOADS

Liftingcapacity

kN tons

Minimumwheelbaseor * 1/5

m ftin

Span! ofçrane (m)

9

ci,0)

C)

Ce

CeI-

0)3.0

Span lof crane (ft)

12 15 18 30 40 50 60

Height H Endclearance E

Notes

m ftin mm in

20 2 1.8 6 0 55 60 70 — 5.5 6 7 — 1.7 5 6 200 8 Tabulated50 5 2.5 8 6 -— 115 130 140 11.5 13 14 1.8 6 0 230 9 dataare

100 10 3.0 10 0 — 180 200 215 — 18 20 21.5 2.0 6 9 240 9.5 typicaland200 20 3.2 10 6 — 310 355 — 31 33 35.5 2.3 7 6 280 11 mayvarydue300 30 3.6 12 0 — 460 480 510 — 46 48 51 2.6 8 6 300 12 tomakeand500 50 4.0 13 0 — 700 720 810 —- 70 72 81 3.1 10 3 360 14 useofcrane

Allowancesfor dynamic effectson crane beamsand supportsBS6399: Part I

Increased vertical load to be considered to act at same time as eithertransverse or longitudinal horizontal force

Forces actinghorizontallyat rail level

Operation

Electric Hand

10%

5%

5%

5%

Beams and su ortsBS 2655

ppDesign load: weight of all machinery on beams plus twice max. suspended loadsFactor of safety of beams (based on strength of materials) = 7

spanDeflection of beams 4c

1500

Type of plant Use/construction kN/m lb/ft

Belt conveyors

Conveyor gantries

For cement, grain, coal, crushed stone etc.

Steel framing, corrugated sheeting, wooden floor

2.5 to 4.1

8.2 to 9.8

168 to 280

560 to 672

kN/m2 lb/ft2

Screening plant Shaker type for coal (including steel supports) 8.0 168

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