Equivalent static wind load procedure for skew winds on large bridges

<p>This paper describes theoretical framework on forming equivalent static wind loads (ESWL) for large bridges. A method is proposed for efficient handling of large number of load cases, when vibration and structural analysis is extended to skew winds, i.e., to the wind directions other than the principal ones. These appear to be increasingly important in many practical cases when complex bridge geometry is used for architectural uniqueness; or when the bridge is situated in city centres or hilly terrain, where local obstacles make the wind turbulence difficult to assess with standard models.</p><p>The method uses a set of load cases for principal wind directions to be input and solved with the static Finite Element (FE) model. Combination matrix is deduced for the results to assess skew winds. The method is alike that is frequently used in wind-tunnel studies of tall buildings. ESWL determination is done in co-operation with the wind and the bridge engineer. The needed input for the wind engineer includes numeric vibration mode shape data, global nodal coordinates and mass distributions. ESWL are created in numeric form that could be easily input to the FE-model. The method allows utilisation of various type analysis results and experimental data available for the bridge, including section-model based analysis, full-model wind-tunnel tests and structural monitoring results. It facilitates examination and adjustment of appropriate safety marginal to wind loads that take into account methodologic uncertainties in each.</p><p>It is proposed that wind-tunnel laboratories, or other wind engineers with bridge analysis expertise, should more often include ESWL-extraction to their services.</p>

Design application and verification of equivalent static wind loads in bridge design

<p>Kruunuvuori Bridge is new link to connect Laajasalo area to the Helsinki city center by crossing a Kruunuvuorenselkä bay. It’s a cable stayed bridge with a single pylon and symmetric span arrangement, designed to be built with free cantilever method. For such a structure, wind is a governing load for the construction and for the final stage.</p><p>In the Engineering design of the bridge, equivalent static wind load (ESWL) extraction was used to define the action forces for the structures due to the wind. With the applied method it is possible to include crucial frequency-dependent parameters like statistical wind turbulence parameters; aerodynamic damping; aerodynamic admittances and modal coupling into the design. Skew wind angles could also be defined. Such loads are easy to apply with general commercial software and the workflow for the design is practical. As the method itself is not standardized and includes specialist defined parameters, it requires an additional verification. This paper describes how the static equivalent wind loads were applied in the design and how the results were verified with full-aeroelastic model wind tunnel testing. As a conclusion, static wind load extraction provides reliable results and is a practical approach for bridge design under skew winds.</p>

Reduced Equivalent Static Wind Loads for Tall Buildings with Tuned Liquid Dampers

The tuned liquid damper (TLD) is a proven and an increasingly popular auxiliary device for mitigating the dynamic effects induced by wind loading on tall buildings. As buildings become taller, lighter, and more flexible, there is a greater contribution from the dynamic component. The most reliable tool for assessing the dynamic component is wind tunnel testing. A boundary layer wind tunnel is capable of accurately calculating an equivalent static wind load (ESWL) acting on a building. The current study investigates the reduction in the ESWL of a lateral-torsional coupled building with a TLD system installed. The building is sensitive to torsion in the first two vibration modes. The current investigation uses three unique multi-modal TLD systems designed specifically for a lateral-torsional coupled building. The building ESWL is evaluated with the TLD systems using measurements from tests conducted at the Boundary Layer Wind Tunnel Laboratory at Western University.

Wind-Induced Vibration Analysis of Wind Fence Structure

As a new wind-break and dust-control technology, the wind fence is widely used at storage yards in factories and ports. The wind fence structure is a new high-rise wind-resistant structure with light damp and very heavy wind load, and the wind-induced vibration response is unknown and equivalent static wind load is hard to determine in design. Based on the Davenport spectrum, wind-induced vibration of the plane frame structure was analyzed with frequency domain method and the response spectrum of displacement and acceleration were obtained. The equivalent static wind load was studied and the wind-induced vibration coefficient and gust loading factor were gained. The results show that the wind-induced vibration response of the structure is significant, and it should be taken into consideration in structural design.