Structural wind loads
Buffeting by gusts in strong wind can cause dynamic loads in a building structure. GWTS is able to determine the building response to buffeting by using state-of-the-art wind engineering techniques. The method employed for a particular project can be desktop, wind tunnel or wind tunnel in combination with computational fluid dynamics depending on the complexity of the project.
Desktop study of structural wind load is based on experience, literature review and building codes and standards. Some of the standards and references used are:
- AS/NZS 1170.2011
- ASCE 7-10
- IBC 2012
- Wind Loading of Structures by John Holmes
- International Journal of Wind and Structures
- We can also use any standard required by our clients.
Wind Tunnel Study
Wind tunnel study of structural wind load usually uses one of the three wind tunnel structural load study techniques. The three methods are High Frequency Base Balance, Simultaneous Pressure Integrations and Aeroelastic methods.
High Frequency Base Balance: The technical procedure for the force balance study involves the use of a light weight, rigid, geometrically similar model of the prototype building mounted on a stiff base balance. The wind tunnel measured values combined with structural data provided by the structural engineers enables complete and accurate building response to be predicted rapidly and economically.
The method has considerable advantage over the older aeroelastic (stick model) techniqueswhich require scaled prototypes to be built and tuned to scaled values of mass, damping and stiffness. Fundamental to this approach is that if any of the design mass stiffens or the damping parameter changes the model must be adjusted and the test repeated. The method is not suitable for structures with a significant torsional response. In this case full aero elastic test is required.
Simultaneous Pressure Integrations: The development of the pressure measurement system allows simultaneous local pressure measurement of all locations on the building. These local pressures measured can be integrated at each sample time to predict the overall structural forces and moments on a building. This method has a similarity with High Frequency Base Balance method. The method requires a high resolution of pressure taps to capture all the local effects which contribute to the global structural loads. The main advantage of this method is that with one test it is possible to provide structural loads information as well as local façade pressure predictions.
Aeroelastic method: This is one of the oldest method in wind tunnel study of structural loads. The full aeroelastic method is still the most valuable method for determining the dynamic loads for very flexible structures. In a wind a structure may experience an aeroelastic instability when aeroelastic forces act to increase the amplitude of motion. The wind tunnel model of aeroelastic test reproduces scales of the building mass, damping, stiffens and frequencies. This method can be combined with High Frequency Base Balance method to reduce the cost and time. For very flexible structures the first stage of the design can be done by HFBB method and the final stage can be refined by using a full aeroelastic wind tunnel test. GWTS engineers will assist you to determine the appropriate method for your project. Computational Fluid Dynamics (CFD) Study: CFD is used as a complement to desktop or wind tunnel study. Vortex shading and the effect of building shape can be easily investigated using CFD.