Dynamic wind load

The effective loads on structures due to blast and associated dynamic wind loads are a function not only of the dynamic characteristics of the load but also the dynamic response characteristics of the structure, which should be... 

In the evaluation of blast damage to structures, a distinction should be made between local and global response of structures. Local response would be associated with response of wall elements relative to their supporting members (girt, purlin, beam and column). For local structural elements the blast and dynamic wind loads are typically associated with only their load on the local structure. 

No.4, July 1999, p.249-65 NEW DYNAMIC WIND LOAD CYCLE TO EVALUATE MECHANICALLY ATTACHED FLEXIBLE MEMBRANE ROOFS... 

Au SK (2014b) Uncertainty law in ambient modal identification. Part II implication and field verification. Mech Syst Signal Process 48(l-2) 34-48 Au SK, To P (2012) Full-scale validation of dynamic wind load on a super-tall building under strong wind. J Struct Eng ASCE 138(9) 1161-1172 Au SK, Zhang FL (2012a) Fast Bayesian ambient modal identification incorporating multiple setups. J Eng Mech 138(7) 800-815... 

For a building with a flat roof (pitch less than 10°) it is normally assumed that reflection does not occur when the blast wave travels horizontally. Consequently, the roof will experience the side-on overpressure combined with the dynamic wind pressure, the same as the side walls. The dynamic wind force on the roof acts in the opposite direction to the overpressure (upward). Also, consideration should be given to variation of the blast wave with distance and time as it travels across a roof element. The resulting roof loading, as shown in Figure 3.8, depends on the ratio of blast wave length to the span of the roof element and on its orientation relative to the direction of the blast wave. The effective peak overpressure for the roof elements are calculated using Equation 3.11 similar to the side wall. 

Certain simplifications that allow the dynamic response to be reconciled with equivalent static loadings are examined. In earthquake loading the dominant effects are found to occur in the lowest mode for which no cross sectional distortion takes place. In wind loading the dynamic response is spread over several modes. The maximum dynamic tensile stresses at the windward base of the tower can be estimated using simple gust effect factors. 20 refs, cited. 

The computation of the dynamic reaction of buildings imder wind load in the freqnency domain is suggested by Davenport (Davenport 1961a). Normally the goal of this method is to evaluate the size of a specific or a vary set of structural reaction values and the exceeding probability of the value for dynamic sensitive structures. The probability distribution used in the spectral method is already fixed with the standard Gaussian probability distribution. Initial step of the method is... 

Locking at the different models it get obvious that both has a different dynamic behavior out of it s model capacity. The beam model is not feasible to show torsion modes, which is easily represent with the finite element model. This phenomena is to be noticed very carefully, in this example we wiU see that it has no big impact, actually no impact at aU because the first bending and the second torsion eigen mode can be considered separate and the torsion mode is not activated by the wind load spectrum. Another problem of the beam model is that only points on the building axis can be considered, with the finite element model any chosen point can be considered. NB Both models represent theatrically correct the behavior under wind load, but the similarity to the reality is very different in this case for both models. 

Vessels will vibrate based on an exciting force such as wind or earthquake. There are two distinct types of loadings as a result of wind. The first is the static force from wind loading pressure against the vessel shell. The second is a dynamic effect from vortex shedding due to wind flow around the vessel. Tall, slender, vertical vessels are more susceptible to the effects of vortex shedding. 

A representative full state finite element dynamic model of OWL is outlined in Fig. 5.4. It comprises the main and secondary mirror and their support structure including the interface to the ground. A typical result for transfer functions from reduced models with 1000 states and 25 states or considered modes are given in the Fig. 5.5. The transfer function describes the movement of the secondary mirror when subjected to wind loads in the -direction. As can be seen, the drastically reduced model still covers the... 

Ropeways are commonly used for skiing and sightseeing venues and urban transportation. The swing of ropeway carriers is easily induced by wind loading, rendering them inoperable for wind speeds in excess of about 15 m/s. This problem has attracted much research attention in the past few decades. The research work has primarily focused on two methods to reduce swing that involve a dynamic vibration absorber and a gyroscope. 

The shakes function is to break up vortices such that mode shapes stimulating dynamic response to the tower are quickly dampened. It is significant to note that adding the strakes significantly increases the drag and thus wind loading. These strakes are shown in Figure 3.4. 

There is also a discussion about the application of gny cable supports for stacks in regards to dynamic response and wind loads. Of particular interest is a discussion about flare header stacks and how to design guy cables for these tall and slender structures. 

Wind load is a transient, live load (or dynamic load) applied to piping systems exposed to the effects of the wind. Obviously the effects of wind loading can be neglected for buried or indoor installation. Wind load can cause other loads, such as vibratory loads, due to reaction from a deflection caused by the wind. 

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