Eccentric connections in steel structure

ECCENTRIC CONNECTIONS IN STEEL STRUCTURES

Presented by- Sarvesh Sureshrao Chikte

CONTENT

• Introduction

• Literature Review

• Theoretical Background

• Experimental Analysis

• Conclusion

• References

Introduction

1) Types of connection

2) Connection Subjected to eccentric shear

3) Methods of analysis

TYPES OF CONNECTIONS1. SIMPLE CONNECTIONS2. ECCENTRIC CONNECTIONS

Basis of classification – C.G of connection & load axis.

SIMPLE CONNECTIONS

Fig -1aFig -1b

Applied load passes through C.G of connections

ECCENTRIC CONNECTIONS

Applied load does not pass through C.G of connections

Fig 2

CONNECTIONS SUBJECTED TO ECCENTRIC SHEAR

Seat ConnectionsFramed ConnectionsBracket Connections

SEAT CONNECTION

Fig 3a – Unstiffened Seat Connections

Fig 3b – Stiffened Seat Connections

SEAT CONNECTION

FRAMED CONNECTIONS

Fig - 4

BRACKET CONNECTIONS

1) Bolted bracket – type I connections2) Bolted bracket – type II connections3) Welded bracket – type I connections4) Welded bracket – type II connections

Methods of analysis

1) Elastic method2) Rigid plastic method3) Ultimate method4) Geometric method

Literature Review• Dr D. M. F. Orr , “The strength of Eccentrically loaded Shear connections” ,

Vol 2, Journal of Constructional Steel Research , 1982

• John R. Veillette1 and John T. DeWolf, “ECCENTRICALLY LOADED HIGHSTRENGTH BOLTED CONNECTIONS” , 111(5), Journal on Structural Engineering, 1985

 • P. S. Nowak and T. W. Hartmann, “ECCENTRIC CONNECTION DESIGN: GEOMETRIC APPROACH” , 119(2) , 1993 • Harish N. Sayankar, Prof. S. D. Khamankar, “Experimental and FE Analysis of

Eccentric Loaded Welded Joint Structure” , Vol 4, Issue 8 , Int. journal of Engineering research and application , 2014

Theoretical Background

BRACKET CONNECTIONS

BOLTED BRACKET CONNECTIONS TYPE 1

Fig 5

FORCES ON BRACKET TYPE 1

Fig 6

 From the assumption made in the concentric bolted joints, ‘ the load over the joint is shared equally by all the bolts’ ,force in any bolt due to direct load is,

  (1)We know that,

And alsoForce = Stress * Area

Therefore,

F2 = k*r

Therefore, the Torque about the center of rotation of the bolt group

Total resisting toq

The resisting torque should be equal to torque over the connection. Hence,

Force F2 is maximum when distance r is maximum. Let the distance of the extreme bolt be rn . then,

(2)

The two forces F1 and F2 act at some angle on various bolts in the connection. Let be the angle between these forces on the critical bolt. Then the resultant force F on the critical bolt will be

(3)

For the connection to be safe, this force must be less than the strength of the bolt.

M = torque in Nmm (caused by the eccentric load) = load * eccentricitye0 = the perpendicular distance measured from the center of

rotation of the bolt group to the line of action of load, called eccentricity P = the eccentric load acting over the joint in N r1, r2…. rn = the distances of the bolts from the center of rotation of the bolt group.

n = number of bolts in the bolt groupF1 = force in a bolt due to direct shear PF2 = force in bolt due to torque Mk = elastic constant

From equation of resultant F it is evident that F depends upon F1, F2 and . For the resultant force F to be maximum with F1 being same for all the bolts and F2 being maximum for the bolt farthest from the center of gravity of the joint, the angle between the forces has to be minimum.

BOLTED BRACKET CONNECTIONS TYPE 2

Fig 7

From the assumption made in the concentric bolted joints, ‘the load is shared equally by all bolts’, Forces F1 in any bolt due to direct load

The tensile force in the bolt is proportional to the distance of the bolt from the line of rotation.

Moment of resistance due to tensile force in a bolt, =Total moment of resistance due to tensile force,

For equilibrium,, total compressive force C should be equal to total tensile force.Hence, total compressive force, External moment = moment resisted by the bolts in tension + moment of the compressive force.

Where,M = Pe0 moment in Nmm, caused by the eccentric loade0 = the eccentricity of the load P from the bolt plane to the

line of action of load in mmP = the load acting over the joint in N

M’ = moment of resistance provided by bolts in tensionVb = force in a bolt due to direct shear P

Tb = tensile force in the bolt due to bending moment (Pe0)n = number of bolts in the bolt groupy1,y2….yn = distance of the bolts in tension from the axis of rotation

y = distance as shown in figure.

WELDED BRACKET CONNECTIONS TYPE 1

WELDED BRACKET CONNECTIONS TYPE 2

Experimental Analysis

Reference paper -The Strength of Eccentrically Loaded Shear Connections(Ultimate Method)

Reference paper - Eccentric Connection design- geometric approach(Geometric Method)

Reference Paper -Experimental and Fe Analysis of Eccentric Loaded Welded Joint Structure(Elastic Method)

Conclusion• Different method of analysis are compared• If priority is less computational efforts go for elastic

method• If number of connections are less go for geometric

approach• If number of connections are more , use elastic approach• Limitation of ultimate method – trial and error method• Limitation of geometric method – if lengthy & tedious

calculations • Limitation of elastic method – assumes linear load-

deformation relationship

References • X.C. Liu , S.H. Pu, A.L. Zhang, A.X. Xu, Z. Ni, Y. Sun, L. Ma , “Static and seismic experiment ⁎ for bolted-welded joint in modularized prefabricated steel structure” ,115, Journal of Constructional Steel Research, 2015 • X.C. Liu , A.X. Xu, A.L. Zhang, Z. Ni, H.X.Wang, L. Wu , “Static and seismic experiment for ⁎ welded joints in modularized prefabricated steel structure” , 112, Journal of Constructional Steel Research, 2015 • Dr D. M. F. Orr , “The strength of Eccentrically loaded Shear connections” , Vol 2, Journal of Constructional Steel Research , 1982 • John R. Veillette1 and John T. DeWolf, “ECCENTRICALLY LOADED HIGH STRENGTH BOLTED CONNECTIONS” , 111(5), Journal on Structural Engineering, 1985 • P. S. Nowak and T. W. Hartmann, “ECCENTRIC CONNECTION DESIGN: GEOMETRIC APPROACH” , 119(2) , 1993 • Harish N. Sayankar, Prof. S. D. Khamankar, “Experimental and FE Analysis of Eccentric Loaded Welded Joint Structure” , Vol 4, Issue 8 , Int. journal of Engineering research and application , 2014

By Murty K. S. Maduguia1 and S. Mohan2, ANGLES IN ECCENTRIC TENSION J. Struct. Eng., 114(10) 1988 

Akbar Pirmoz,_, Amir Saedi Daryan, Ahad Mazaheri, Hajar Ebrahim Darbandi, Behavior of bolted angle connections subjected to combined shear force and moment , Journal of Constructional Steel Research 64 (2008)  Konstantinos E. Kalochairetis , Charis J. Gantes, Xenofon A. Lignos, ⁎Experimental and umerical investigation of eccentrically loaded laced built-up steel columns, Journal of Constructional Steel Research 101 (2014)

Thank You