Lateral loading and response for a tall building in the non-seismic doldrums

Abstract

The situation for building design against wind and earthquake effects in Singapore is apparently unique. There is no seismic design code as there is no local seismicity, yet the effects of significant regional earthquakes are frequently felt in many high rise buildings in Singapore. Whereas it has become clear that the strongest winds in Singapore originate from storms and squalls, design for wind by law requires use of an arbitrary design wind speed applied in a British loading code geared to cyclonic wind systems. A decade of monitoring of a 280 m office tower has shown that distant strong earthquakes generate dynamic response typically an order of magnitude greater than due to the strongest winds occurring during the same period. The effect is greater for high rise apartment blocks and it is becoming clear that for extreme events with similar return periods, earthquake effects should govern design for lateral load in terms of dynamic base shears under such conditions. For the present, building control authorities take code provisions for accidental eccentricity to be adequate in covering seismic loads. While there have been moves towards a more rational local code, there remains an open question about the relationship of static and dynamic effects due to wind for both cyclonic and (thunder)storm winds. In this paper, the evidence concerning the nature of the two forms of loading is presented, and the various existing and potential code provisions examined.