WIND TUNNEL TEST IN TALL BUILDINGS AND STRUCTURES

ABSTRACT

The new generation of tall buildings is gone much higher than before. This poses new challenges for wind engineering. For the super-tall buildings wind tunnel testing is often commenced much earlier in the design than for lesser buildings. The objective of the wind tunnel test study is to replicate the real physics of wind loading at model scale. This includes along wind loading, cross wind loading, torsional loading, load combinations, building motions, and the influence of terrain roughness, topography, directionality and other nearby structures.Wind tunnel tests were conducted to investigate the effects of some aerodynamic devices on the wind-induced responses of tall buildings and structures. The wind tunnel methods used include the force balance technique, aeroelastic modeling, high frequency pressure integration tests, as well as the traditional pressure model and pedestrian wind studies. Since the impact of wind on people using terraces and balconies increases with building height, it is an issue needing particular attention for super-tall buildings.

Wind-induced response is an important factor in the design of modern tall buildings and structures. The along-wind and cross-wind excitation mechanism, response characteristic and prediction procedure have been studied extensively and are well-documented. The reason that the wind tunnel testing of buildings and other structures continues to increase at a rapid pace is the realization by many designers that, for large structures, the generic load provisions derived from analytical methods in building codes and standards (herein called Codes) are often insufficiently precise for an optimal design. Code analytical provisions typically, but not always, give wind loads that are higher than what the building will really experience in the storm of design intensity. Fortunately, most modern Code analytical methods also allow and, in fact, recommend wind tunnel tests be undertaken where more accurate wind loads are desired. Physical modeling to quantify wind effects for either wind-engineering design or research requires simultaneous similarity for two distinct physical phenomena. The initial consideration is similarity of the desired natural wind characteristics. Wind tunnel testing requires up-front cost and time, or reduced “short-term” economy. However, wind-tunnel loads are usually lower than code, resulting in greater economy in the structural framing. Sometimes, wind-tunnel results can be greater than code loads, resulting in greater safety, reduced risk, and reduced maintenance all contributing to long-term economy. An efficient and economical structural system designed against these wind-induced stresses and motions is required to ensure structural safety, serviceability, and occupant comfort.

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