Influence of the group positioning of cylinders on the wind pressure distribution in the post-critical regime

In order to estimate the wind loads on circular cylindrical shell structures, the pressure coefficient as a function of the Reynolds number is given for an isolated cylinder in Eurocode 1 - Part 2-4: Actions on structures - Wind actions. As cylinders are often placed in groups and the configuration of these groups largely influences the pressure distribution around the cylinders, a computation of the wind flow provides a more realistic estimation of the pressure coefficients. First, the transient 2D turbulent air flow around a single cylinder at a Reynolds number of 12.4 millions is computed using the SST turbulence model and the results are compared with the pressure coefficients in Eurocode 1 and with experimental data. The minimum pressure coefficient is underestimated, while the base pressure coefficient is slightly overestimated. Unsteady simulations are performed for the flow around a group of 2 by 2 and of 8 by 5 cylinders. Vortex shedding occurs both from the group as a whole, and from individual cylinders. The group configuration drastically changes the time-averaged pressure distribution around the cylinders. High values of suction are present at the location of the small gaps between the cylinders and upstream of the separation points of the cylinders on the side corners of the groups. The cylinders at the borders of the groups experience high drag or lift forces, while these forces are considerably lower in the middle of the group

Verification of joint input-state estimation by means of a full scale experiment on a footbridge

This paper presents a verification of a state-of-the-art joint input-state estimation algorithm using data obtained from in situ experiments on a footbridge. A dynamic model of the footbridge is based on a detailed finite element model that is calibrated using a set of experimental modal characteristics. The joint input-state estimation algorithm is used for the identification of two impact, harmonic, and swept sine forces applied to the bridge deck. In addition to these forces, unknown stochastic forces, such as wind loads, are acting on the structure. These forces, as well as measurement errors, give rise to uncertainty in the estimated forces and system states. Quantification of the uncertainty requires determination of the power spectral density of the unknown stochastic excitation, which is identified from the structural response under ambient loading. The verification involves comparing the estimated forces with the actual, measured forces. Although a good overall agreement is obtained between the estimated and measured forces, modeling errors prohibit a proper distinction between multiple forces applied to the structure for the case of harmonic and swept sine excitation.Offshore Engineerin

Verification of Joint Input-State Estimation by In Situ Measurements on a Footbridge

An existing joint input-state estimation algorithm is extended for applications instructural dynamics. The estimation of the input and the system states is performed in a minimum-variance unbiased way, based on a limited number of responsemeasurements and a system model. The noise statistics are estimated, as they areessential for the joint input-state estimation and can be used to quantify the uncertainty on the estimated forces and system states. The methodology is illustrated using data from an in situ experiment on a footbridge.Offshore Engineerin

Identification of multiple localized forces on a footbridge

An existing joint input-state estimation algorithm is extended for applications in structural dynamics. The estimation of the input and the system states is performed in a minimum-variance unbiased way, based on a limited number of response measurements and a system model. An additional method is proposed to identify the noise statistics, which are needed for the joint input-state estimation procedure and which can be used to quantify the uncertainty on the estimated forces and system states. The proposed methodology is illustrated using data from an in situ experiment on a footbridge.Hydraulic EngineeringCivil Engineering and Geoscience