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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