Description

Eurocodes (EC3/EC8)

AISC/ASCE

Remarks

Energy dissipation philosophy

EBFs shall be designed so that specific elements or parts of elements called seismic links are able to dissipate energy by the formation of plastic bending and/or plastic shear mechanisms.

EBFs are expected to withstand significant inelastic deformations in the links when subjected to the forces resulting from the motions of the design earthquake.

An almost same criterion is considered

Rotation capacity (local ductility

concept)

Plastic hinge rotation is limited to 35 mrad for structures of DCH and 25 mrad for structures of DCM

Link rotation angle shall not exceed (a) 0.08 radians for links of length 1.6 Mp/Vp or less and (b) 0.02 radians for links of length 2.6 Mp/Vp or greater.

For high seismicity it is recommended by both codes to apply ductility concept

Dissipative members

Plastic Hinges should take place in links prior to yielding or failure elsewhere.

EBFs are expected to withstand significant in-elastic deformations in the links when subjected to forces resulting from the motions of the design earthquake.

Links can be short, long and Intermediate. Which fail due to Shear, bending and bending & Shear respectively.

If N E D / N p l , R d 0.15 then Check for Design Resistance of Link is

V E D V p , l i n k

M E D M p , l i n k

Effect of axial force on the link, available shear strength need not be considered if P u 0.15 P y (LRFD) or P a 0.15 / 1.5 P y (ASD)

NED, MED& VED respectively are the design axial force, design bending moment and design shear at both ends of the link.

Check to achieve global dissipative behaviour of the structure

The maximum overstrength Ωi should not differ from the minimum value Ω by more than 25%

The required strength of each lateral brace at the ends of the link shall be P b = 0.06 M r / h 0 , where h0 is the distance flange centroids

Ω i = 1.5 V p , l i n k , i / V E D , i among all short links and minimum value of Ω i = 1.5 M p , l i n k , i / M E D , i among all intermediate and long links.

Seismic load reduction factor

A behaviour factor (q) equal to 4 for DCM and 5αu1 for DCH is provided.

A response modification factor (R) equal to 8.0 for EBFs is given

An almost same criterion is considered

Overstrength factor

the minimum value of Ω i = 1.5 V p , l i n k , i / V E D , i among all short links, whereas

the minimum value of Ω i = 1.5 M p , l i n k , i / M E D , i among all intermediate and long links;

Ωo equal to 2 for EBFs is given

Ωo in EC8 is (1.1γovΩ)