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3.2 ADVANTAGES and DISADVANTAGES OF
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Fig. 2b. Pedestrian Tensegrity Cable-stayed Bridge (Shawkat, 2019)
Fig. 2c. Pedestrian Tensegrity Cable-stayed Bridge (Shawkat, 2019)
when solving the load-bearing capacity of structures as the Pedestrian Bridge, it is necessary to solve the problem of how stresses and deformations arise when the structure is suddenly loaded, which are in many times greater than when the load is slowly applied to the structure. Such rapidly applied forces or displacements are usually referred to as impact respectively accidental or impulse loads.
The question of whether it is necessary to consider the load of the structure as quasi-static or accidental is usually solved by comparing the time of loading the load and load time, with the largest period of natural vibrations of the structure.
If the time of the load is less than half of the largest period of the natural frequency, the loads must be considered accidental. if the load time is more than three times the period of the natural frequencies, the loads can be considered quasi-static. In the case of accidental load, it is necessary to consider not only the value of the load but also the time during which this load reaches the final value, as well as the impulse, which represents the area under the curve of the load-time diagram.
In the case of quasi-static loads, they arise in the structure in different ways. the load is created by a rapidly moving load, created for example by the movement of a train on a bridge.
Once it takes place at the reinforcement point of the structure, for example at the connection point of the support plate to the heat exchanger tubes, accidental forces may cause abrasion due to small transverse displacements caused by transverse deformations or small transverse components of the speed of the sliding impact, i.e. there is a risk of failure in the form of abrupt friction.
It should be noted that due to accidental loads, the load increase, and the properties of the material can change significantly in comparison to quasi-static loads, it can be noted that the values of yield strength and elasticity under accidental load significantly differ from their values under static or quasi-static loading.
