Exceptional Loadings / Robustness

June 14, 2002 Volos

A.M. (Nol) Gresnigt

Delft University of Technology The Netherlands

Exceptional loadings / actions (1)

• •

Explosion - where:

– Buildings: gas explosion - limit damage – Refinery : explosion - blast to control buildings – Offshore platforms: gas - living quarters – Transport: road / ship / pipeline – Fireworks (Enschede 2000)

Explosion - research:

– Safety and reliability analyses to quantify acceptable risk – Identify possibilities to avoid occurrence and evaluate effectiveness and costs of such measures – Design guidelines to limit damage - “ALARA principle”

Exceptional loadings / actions (2)

• • •

Fire

– Development to natural fire concept – Laws and building regulations - practice - local authorities – Optimisation fire safety / protection measures – Research at TNO - TUD

Collision

– Buildings / bridges / offshore platforms / ….

– Identify possibilities to avoid occurrence and evaluate

Earthquake

– In 1992 one exceptional with Richter 5.8 near Roermond – July 22, 2002 one with 4.9 in the same area – Faults in earth crest - mining (coal-gas) – Design: wind load is supposed to be adequate

Robustness (1)

•

Strength - rotation / deformation capacity

– Work of Martin Steenhuis: interaction to structural reliability – Work of P. Zoetemeijer 1975 - 1985 – Various studies in connection with explosion safety / design – …...

• Practical application in engineering community ?

– Design guides –

Education:

much has to be done…...

Robustness (2)

•

Education

– Design philosophy • Loads and deformation requirements often not quantified in standards • Many loads and imposed deformations not taken into account • Robustness - deformation capacity needed: not quantified • Schematisation of the structure in the structural analysis (e.g. hinges / stiff connections) – Practical • Welded connections: sufficient strong welds and ductile weld metals • Bolted connections: sufficient strong and ductile bolts • Yielding in the plate material before failure of welds / bolts • Bearing above shear • T-sub yielding of the plates above rupture of the bolts • …...

Robustness (3)

•

Education

– In practice • Steel construction shop has to design the connections • Designer of connections often not well skilled • Designer of connections often not well payed • Tendency to simplify connections design and above all simplify connection calculations – Examples of poor design / calculations • Thick end plates that never yield; then determine number of bolts on the basis of design load: no check on deformation capacity etc.

• Lap joints: relatively thick plates and thin bolts: no need for checking bearing, just shear from table to determine number of bolts • Semi-rigid calculation and verification on one half A4……..

Concluding

• Theoretical and experimental research must go on • Education and checking of people in practice is essential • Task of local building authorities • Political awareness and involvement will improve, especially after some collapses and disasters in recent years