|
|
||
|
|
|
|
The transfer of shear forces in the vicinity of the web opening induces local bending moments, known as the Vierendeel mechanism. Fig. 3 shows the development of the four local plastic hinges, for the same opening size (do=0.8h) at different locations along the beam. Connections with small openings are unable to develop plastic hinges as the effective depth of the web is still large enough to resist the global vertical shear stresses. As a result, higher stresses are developed in the panel zone and in the shear tab as the beam rotates.
From:
Konstantinos Tsavdaridis and Christopher Pilbin (School of Civil Engineering, University of Leeds), “Finite Element modelling of steel connections with web openings: Aseismic design and avoidance of progressive collapse”, The 7th European Conference on Steel and Composite Structures, Napoli, Italy, September 2014
PARTIAL INTRODUCTION: Events of extreme loading on structures such as the 1994 Northridge, California earthquake and the 2001 attack on the World Trade Centres, New York have not only lead to loss of life but highlighted structural deficiencies and lack of existing knowledge of the progressive collapse behaviour. As a result, Governmental bodies such as the GSA [1] and DoD [2] have established design codes and guidelines to reduce the possibility of progressive collapse through the promotion of redundancy, ductility and continuity in structural systems. The design codes do not provide guidelines for the complete prevention of progressive collapse but rather mitigate a ‘disproportionate’ area of collapse. In collapse scenarios, following the removal of a load bearing column, the ability for the beams and columns to develop catenary action is essential for the structure to resist further collapse. Beam-to-column connections should provide sufficient ductility to sustain large rotations and allow structural members to carry loads in tension.
Page 222 / 410