Mg Savage

Buffeting analysis of long span bridges to turbulent wind with yaw angle

Abstract Based on sectional model tests, a method is presented to predict the buffeting response of long span bridges under turbulent wind with a yaw angle. The yaw angle of the wind generally influences the buffeting response through the change in the effective mean wind speed, the effective deck section and the horizontal correlation of the turbulence along the span. The presented method takes all these effects into account with certain approximations.

Prediction of wind-induced failure of loose laid roof cladding systems

Abstract This paper presents a correlation for predicting wind speeds at which loose-laid insulation boards or paving slabs are dislodged from roofing systems on flat roofs. The correlation is based on experimental data obtained from 1:10 scale model tests in a 9 m × 9 m wind tunnel. The influence of building shape, parapet height, weight per unit area of boards or paving slabs and interlocking effects are accounted for.

An experimental study of the aerodynamic influence of a pair of winglets on a flat plate model

The influence of a pair of thin stationary winglets on the aerodynamics of a bluff body is studied in this paper. The bluff body in question is a rectangular prism with a width-to-depth ratio of nine, and is referred to as a flat plate. The aerodynamic and aeroelastic characteristics studied experimentally were the static aerodynamic force and moment coefficients, their rate of change with angle of wind incidence and the motional aerodynamic derivatives. It was observed that a pair of winglets placed directly above the leading and trailing edges of the rectangular prism improved its aeroelastic characteristics. The winglets provided important aerodynamic damping and reduced the sensitivity of the rectangular prism to torsional aerodynamic instability. The experimental approach and a summary of the main findings are presented.

Half-circular and half-elliptic edge modifications for increasing aerodynamic stability of stress-ribbon pedestrian bridges

A wind tunnel study was conducted to examine the aerodynamic stability of concrete stress-ribbon pedestrian bridges with special reference to the Jomon Bridge. Not popular triangular fairings but half-circular and half-elliptic modified edges on both sides of decks were examined as a fundamental study prior to the Jomon deck model test. The modifications are found to be effective in increasing the critical flutter speed VF as well as suppressing vortex excitation. It was found in the Jomon deck model test that VF was below the design speed for the deck with a conventional cross-section and that VF was greatly increased by the similar edge modifications and a pair of half-circular cylindrical fairings as well. Based on the test results and for some reasons, the half-circular fairing was applied to the actual bridge.

Wind-induced oscillations of groups of bridge stay-cables

An experimental study of wind-induced oscillations of groups of bridge stay-cables was conducted in two wind tunnels, one in Japan and one in Canada, to develop a method for suppressing the instability. At first, the parallel cable models were connected rigidly to each other with spacers, forming a coupled cable group whose surface-to-surface separation, or gap, could be varied from 0 to 2 cable diameters. This modification stabilized the wake galloping but it was found that a different form of instability then occurred at higher wind speeds. In this case the group of cables, rather than just the downwind cable, was unstable. With zero gap, the group was most stable, being unstable only near wind angles of 5° and aerodynamically stable otherwise. When the cable group with zero gap was twisted into a shallow helix, it was found to be aerodynamically stable for all wind angles.

A device for suppressing wake galloping of stay-cables for cable-stayed bridges

Abstract An experimental study of wake galloping of a pair of parallel stay-cables for cable-stayed bridges was conducted in two wind tunnels to develop a new device for suppressing the instability. In its early stage, the following device was examined: A pair of parallel cables is connected rigidly to each other with spacers so that the cables form a SINGLE MEMBER with or without a GAP between the cables. It was determined from the tests that the member without a gap is stable for all wind angles of attack with the exception being around 5 deg. Based on the experimental results, an alternative device was developed consisting of a pair of cables stranded helically. The strand was found to be stabilized aerodynamically as only a small portion of the cables is exposed to the unstable wind angles of attack around 5 deg.