RUNWAY CRANE GIRDERS

1. General elements: details of supports on columns, sections, rails2. Forces acting on runway girders and combinations rules3. Verifications of the runway girders

Overhead crane girders for industrial buildings (small lifting capacity)

TYPES OF RUNWAY GIRDERS

Runway crane and girders: 1-crane bridge; 2- gantry girder; 3- crab; 4- end carriage; 5- payload; l-span of the crane bridge; a- spacing between the wheels of the crane; L-bay of the building

Section of runway girders for cranes with different loading: a)- hot rolled sections for light loads and small bays: b) and c)- build up sections from hot rolled shapes; d) runway girder with horizontal girder which delivers the reactions to the structural column ( heavy loads and big bays)

I (IPE) and build up sections are used for smaller bays and lighter cranes (6 m, Q=50...100 kN). Bigger bays and lifting capacities of the cranes (9…12 m, Q200 kN) build-up cross sections are used .

Runway girder with horizontal girder made of steel plate: 1- top flange of the crane girder; 2- rail; 3- angle cleats for fixing the rail on top flange; 4- thick chequered plate; 5- angle stiffener; 6- joist supporting the plate between two running columns; 7-angle supporting the plate attached to the flange of the column; 8- splice for thee bolted connection of the joist to the column

Runway girders with platform sustained of steel lattice girder: 1- welds done at site; 2- bolted connection between the flange of the column and the elements of the horizontal lattice girder

RAILS SYSTEMS

Different systems of fixing the rails on the crane girder: a), b) square rails welded continuously to the top flange; c) - railway rails fixed with clamps; d), square rail fixed with angles fastened with bolts to the top flange; e)- KP profile of rail ; f)- railway rails on elastic support (1-neoprene pad); g) rails attached with hooks to the top flange.

Minimum thickness tr measured downwards from the wear

surface of the rail

Buffers on the crane girders: a)- for cranes carrying light loads and easier working conditions; b), c) – for cranes carrying heavy loads and hard working conditions

Evaluation of the permanent actions on runway girders

L)30.0...15.0(g k,G

uniform distributed loads on the length of the girder [kN/m];1) estimated characteristic value of the weight of the crane girder, extracted from tables of hot rolled sections or evaluated during the sizing procedure; for plate girders the following value may be adopted:

2) characteristic value of the weight of the rail (including the weight of the connections); for a square section we may determine the weight:

3) characteristic values of weights of the elements of the horizontal girder, in the case when they are part of the runway system, for ex. weight of the chequered steel plate or of the elements of the horizontal lattice girder. In all the cases the weight transferred to the runway girder is considered from half of the width of the platform, the other half being supported by the horizontal joists attached to external flanges of the columns.

2

bwg i

k,pk.p

wp,k – weight of the chequered steel plate of mild steels from catalogue, according with its thickness; for industrial purposes a minimum thickness is required because of corrosion exposure;bi – width of the column assimilated with the distance between the axis of the rail of the runway and axis of the transversal frame

live loads according to the EN 1991-3 recommendations: Point load Qk = 3.0 kN if materials are deposited on the platform and Qk = 1.5 kN

if the platforms insure only the access. Forces resulted from other elements existing on the runway (like buffers, a.s.o.).

15.17850hg 2rk,r

Vertical loads cases Total wheel load on railCrane stationary, lifting the payloadCrane moving with the loadi - impact factor;f – partial safety factor for vertical crane actions;Qmax – characteristic vertical wheel reaction from the hook load;Gk – sum of the weight of the crane, rails and others

kf1maxf2 GQ kfmaxf4 GQ

Maximum vertical loadsPermanent loads: - weight of the trolley (carriage) and the lifted load ;- weight of the crane bridge;- self-weight of the crane girder and rails;- weight of the horizontal girder if this exists;

Live load on the platform if there is the case, Qk,i.

Maximum horizontal loads

Transverse surge from the crab ( the load is taken as 10% of the combined weight of the crab and the lifted load);

Longitudinal surge load from the crane (5% of the static vertical reactions, i.e. from the weight of the crab, crane bridge and lifted load;

Skew loads due to travelling; if the crane is class S1 or S2, then these forces would not need to be considered.

Horizontal loads need not to be combined together.

Forces from the point loads acting on the runway girder: 1- vertical actions on the wheels of the crane; 2- horizontal longitudinal actions from crane surge; 3- horizontal transversal actions from crab surge; 4- effect of skewing of the crane; 5- crab

Combination of the vertical and horizontal loads in U.L.S.

Considering the recommendations for grouping the vertical with the horizontal loads, the following combinations are: Dead loads (permanent) + live loads (accompanying variable) + vertical point loads from reactions on the

wheels (basic variable); Dead loads (permanent) + live loads (accompanying variable) + horizontal point loads from: crane surge or crab

surge or skew driving effects (as basic variables); Dead loads (permanent) + live loads (accompanying variable) + vertical point loads from reactions on the

wheels (basic variable) + horizontal point loads from: crane surge or crab surge or skew driving effects (accompanying variable).

Determination of the relevant internal forces and moments in the runway girder

The concentrated forces being mobile influence lines will be used to determine the maximum bending moments, shear forces and reactions on the supports.During the process of determination of the position of the convoy of mobile forces that will lead to the maximum bending moments some forces may remain outside the girder length. The factors that influence these situations are mainly the wheel spacing, a, and the width of the end carriage, aw.

Design verifications of the crane girder Limit state of strength and stability: Lateral-torsional buckling Horizontal moment capacity Combined vertical and horizontal moments Web shear at supports Local compression under wheels Web bearing and buckling under the wheel and under the supports

Determination of maximum internal efforts and bending moments in the simple supported girders: a) the translation of the convoy of mobile forces along the girder for

the position of maximum moment;b) b)- influence lines for bending moments and shear forces (in case

of three mobile forces on the girder).

Verifications in S.L.S.

Vertical deflection of a crane girder under static vertical wheel loads

Horizontal deflection under the transversal loads

600

Llim,v

500

Llim,h

Fatigue verification is run according to EN 1993-1-9

The effects of the actions from cranes on the girders

I. Biaxial bending produced by the vertical and longitudinal transversal actions;II. Axial compression or tension produced by the horizontal longitudinal actions;III. Torsion produced by horizontal transversal forces eccentrically applied with respect to the shear center

of the cross section of the girder;IV. Horizontal and vertical shear forces, produced by the corresponding actions;V. Local stresses produced by the weighing forces, statically applied from the wheels on the top of the

rail.

Local stresses in the web of the crane girder produced by vertical loads on the wheel at the top flange

Local compression stresses, 0z,Edwteffl

Ed,zF

Ed,oz

Extending the length of distribution of the local stresses on the depth of the crane girder

Case DescriptionEffective length of

distribution leff

1 The rail is fully restrained to the top flange2 The rail is partially restrained to the top

flange3 The rail is placed on a flexible neoprene pad

of 6mm thickness

If,eff – moment of inertia of the flange of the crane girder with effective width beff with respect to its horizontal neutral axis;Ir – moment of inertia of the rail with respect to its horizontal neutral axis;Irf – moment of inertia of the cross section obtained from the flange of the crane girder with effective width beff and the rail with respect to its horizontal neutral axis;tw – thickness of the web

but Where: b – total width of the top flange of the crane girder; bfr – width of the rail, see fig. 2; hr – height of the rail, see fig. 1; tf – thickness of the flange of the beam.

Note: the wear of the rail must be considered

31

wreff tI25.3l

31

weff,freff tII25.3l

31

weff,freff tII25.4l

frfreff thbb bbeff

Local shear stresses,0xz,Ed

Local and global shear stresses produced by the vertical forces transferred from the wheel to the crane girder: 1- global shear stresses; 2-local shear stresses; 3- position of the load on the wheel

Local stresses of bending produced by the eccentricity of application of the loads on the wheel, T,Ed

tanh2wat

EdT6

Ed,T

5.0

awh2awh2sinh

awh2sinh

tI

2wat75.0

yEd,zEd eFT

Torsion of the top flange of the crane girder

Strength verifications of the crane girders 0.1f

3ffff

2

My

Ed

My

Ed,z

My

Ed,x

2

My

Ed,z

2

My

Ed,x

00000

0.1M

M

M

M

N

N

Rd,z

Ed,z

Rd,y

Ed,y

Rd

Ed

Axial internal efforts Rd,tEd NN

2M

ufTF,netA9.0

Rd,uN

;

0M

yf

TFARd,plN

)Rd,uN,Rd,plNmin(Rd,tN

Rd,cNEdN

0M

yf

TFARd,plNRd,cN

Shear resistance of the top flange Rd,cVEdV

0M3

yf

TFARd,plVRd,yV

Shear resistance of the web in elastic or plastic; buckling in shear of the web

1

0M3yf

Ed

72t

h

w

w

Rd,pl

My

Ed,tRd,T,pl V

/3f25.11V

0

0.1

V

V

Rd,T,pl

Ed