Seismic Pounding of Bridges due to Multi-Support Excitation with traveling wave

Abstract: -Among structural damages, seismic induced pounding has been commonly observed in severalearthquakes. When lateral and transverse movement of a structure occurs during earthquakes, it will hit adjacent structure and bounce back. This back and forth hitting of adjacent structures is known as pounding. The earthquake ground motion is usually assumed as uniform dynamic motion in seismic analysis. This assumption may be inadequate for structures placed at large areas like bridge, dam etc. Pounding in bridges is a result of the relative movement of the adjacent bridge superstructures at the expansion joints. This movement depends on different structural dynamic properties of the adjacent spans and characteristics of ground motions at the pier supports along the bridge. This paper includes a study of effect of pounding between bridge superstructures under the action of earthquake motion having multi-support excitation with traveling effect. The present study is a numerical investigation of pounding effect on a simply supported bridge using finite element method, using the software, OpenSees

Effect of hammer impact on wave propagation characteristics of soil: A laboratory study

Copyright © 2020 IGI Global. Wave transmission through soil due to dynamic load causes many problems to civil engineers craving safe construction. In this article, a laboratory model study is conducted to investigate the vibration propagation characteristics of soil due to the falling masses at different depths. Different types of impact, soils, and relative densities are used to study the characteristics of vibration transmission and energy dissipation. It was found that the increase in relative density and decrease in the depth causes an increase in the Peak Particle Acceleration and wave velocity of soil. An attempt is also made to determine the dynamic properties of soil using wave velocity ratios. A simple laboratory arrangement discussed here can be used to predict the wave propagation in soil reasonably and can determine its elastic constants. From the studies, it was revealed that the wave travel in soil and the peak particle acceleration depends on many factors like density, particle gradation, impact energy, etc

Self-expandable stents for tracheal stenosis: experience in two patients

Two patients with cervical tracheal stenosis, following prolonged ventilatory support, underwent balloon dilatation and expandable stainless steel stent placement across the stenoses. Following the successful release of the stent, there was gradual widening of the stenosed trachea in one patient, while in the other re-stenosis occurred due to columns of tracheal tissue projecting between the limbs of the stent. In the chronically ill and debilitated, use of expandable stents provides a good alternative to complex reconstructive surgery