OPTIMIZATION OF TUNED MASS DAMPERS ATTACHED TO DAMPED STRUCTURES - MINIMIZATION OF MAXIMUM DISPLACEMENT AND ACCELERATION

A tuned mass damper is a device, which can be highly helpful while dealing with dynamic behaviour of structures. Its proper design is conditioned by knowledge of both loading and the structure properties. In many cases, the structure can be represented by single degree of freedom model, which simplifies the design and optimization of tuned mass dampers. Most of studies focus only on minimization of displacement of the main structure under harmonic force load, however, in many cases, different frequency response function would be more appropriate. This paper presents an extension of design formulas for the H∞ optimization of tuned mass dampers for damped structures and various frequency response functions

DESIGN OF TUNED MASS DAMPERS FOR LARGE STRUCTURES USING MODAL ANALYSIS

Tuned mass damper is a device, which can be highly useful when dealing with excessive vibration and is widely used in many engineering fields. However, its proper design and optimization is a complicated task. This study uses mode superposition method to speed up the evaluation of dynamic response. The speed of response calculation allows for a quick calculation of frequency response function and numerical optimization of tuned mass dampers. This optimization method is demonstrated on a numerical example of a cable stayed footbridge. The example compares a simplified and widely used design method of tuned mass damper with numerical optimization

Dynamic response of structures with tuned mass dampers in modal coordinates

The tuned mass damper (TMD) is an effective way to deal with excessive vibration of structures. Its high efficiency is, however, conditioned by proper design. The optimization of TMD is a complicated process, because a closed-form solution for its optimal parameters is known only for several simplified cases. This paper presents an approach of dynamic response calculation of structures with TMD in modal coordinates, which is suitable for repeated evaluations of response to harmonic load which is necessary in case of optimizing TMD parameters for large and damped systems

DESIGN OF TUNED MASS DAMPERS FOR LARGE STRUCTURES USING MODAL ANALYSIS

Tuned mass damper is a device, which can be highly useful when dealing with excessive vibration and is widely used in many engineering fields. However, its proper design and optimization is a complicated task. This study uses mode superposition method to speed up the evaluation of dynamic response. The speed of response calculation allows for a quick calculation of frequency response function and numerical optimization of tuned mass dampers. This optimization method is demonstrated on a numerical example of a cable stayed footbridge. The example compares a simplified and widely used design method of tuned mass damper with numerical optimization

RELATION BETWEEN STATIONARY AND MOVING PEDESTRIAN LOAD MODELS

The dynamic analysis of footbridges became common in recent years, but the approach to modelling pedestrian induced load is still inconsistent. This paper compares two different ways of modelling single pedestrian load. The response of the structure to stationary pulsating force is compared to the results given by the same force moving along simply supported beam. 300 randomly generated beams were used in this parametric study to describe the relation among these two approaches and parameters of the structure. The proposed formula was successfully applied to get more realistic estimation of response of the structure to a single walking pedestrian using stationary pulsating force

OPTIMIZATION OF TUNED MASS DAMPERS ATTACHED TO DAMPED STRUCTURES - MINIMIZATION OF MAXIMUM DISPLACEMENT AND ACCELERATION

A tuned mass damper is a device, which can be highly helpful while dealing with dynamic behaviour of structures. Its proper design is conditioned by knowledge of both loading and the structure properties. In many cases, the structure can be represented by single degree of freedom model, which simplifies the design and optimization of tuned mass dampers. Most of studies focus only on minimization of displacement of the main structure under harmonic force load, however, in many cases, different frequency response function would be more appropriate. This paper presents an extension of design formulas for the H∞ optimization of tuned mass dampers for damped structures and various frequency response functions

Role of alarmins in perioperative medicine.

Úvod: ZO je základní reakcí na poškození buněk a tkání. Jejím cílem je zvrat patologického procesu a zachování strukturální a funkční integrity živého organismu. Nadhraniční nebo protrahované působení inzultu může vést k dysregulaci zánětu až na systémovou úroveň. Za významný inzult lze považovat i rozsáhlý chirurgický výkon, např. resekční výkon na GIT, tzv. major abdominal surgery (MAS). Signálem pro aktivaci ZO mohou být alarminy, což jsou intracelulární molekuly, které v situaci, kdy je buňka poškozena, jsou uvolňovány do extracelulárního prostoru, kde mají bioaktivní efekt. Alarminy tedy mohou odrážet míru chirurgického poškození. Cíle práce: Primárním cílem práce bylo zjistit roli vybraných alarminů při stimulaci ZO při MAS. Sekudárními cíle práce byly: 1) zjistit schopnost vybrané skupiny alarminů predikovat klinický výsledek, 2) stanovit vztah hladiny alarminů a lokalizace chirurgické resekce, 3) stanovení korelace mezi hladinami alarminů a některými charakteristikami chirurgického výkonu, např. délka výkonu, krevní ztráty a intraoperační tekutinová nálož, 4) srovnat efekt laparoskopie a otevřené chirurgické operativy na hladiny alarminů a 5) ověřit předchozí výsledky stanovením role alarminů v podskupině pacientů podstupujících kolorektální chirurgii. Materiál a metodika: Subjekty byly zařazovány...Introduction: Inflammatory response (IR) is a fundamental reaction to the cell and tissue injury. It is aimed at correcting the pathologic condition and maintaining the structural and functional integrity of the organism. The insult with too extensive or prolonged effect can lead to dysregulation of IR to the systemic level. Major abdominal surgery (MAS) can be considered as a potentially significant insult. Alarmins are endogenous, intracellular proteins that are passively or actively released upon the cell injury to extracellular space where they express their bioactive effect. Alarmins has therefore potential reflect the degree of surgical injury. Purpose: The main goal of the study was elucidating the role of selected alarmins in inflammatory response after MAS. The secondary aims were: 1) determining the relationship between alarmins and outcome prediction, 2) to determine relationship of alarmins and place of surgical intervention, 3) to determine correlation between alarmins and some of the surgery characteristics, e.g. length of surgery, blood loss, and intraoperative fluid load, 4) compare injury caused by laparoscopy and open surgery reflected by alarmins, and 5) to confirm previous results by determining the role of alarmins in surgical injury in subgroup of patients undergoing colorectal...Department of Infectious and Tropical Diseases First Faculty of Medicine and Hospital BulovkaKlinika infekčních a tropických nemocí 1. LF UK v Praze a Nemocnice Na BulovceFirst Faculty of Medicine1. lékařská fakult

Pedestrian load models of footbridges

The increase of vibration problems in modern footbridges shows that footbridges should no longer be designed for static loads only. Not only natural frequencies but also damping properties and pedestrian loading determine the dynamic response of footbridges and design tools should consider all of these factors. In this paper the pedestrian load models for serviceability verification of footbridges, which are missing in the current European codes, are presented. For simplicity reasons the proposed pedestrian load models are based on stationary pulsating loads instead of moving pulsating loads. It is shown that simplified procedure can be used in verification of the serviceability limit state related to vibration due to pedestrians. Footbridge vibrations don’t cause usually structural problems, but if the vibration behaviour does not satisfy the comfort criteria, changes in the design or damping devices could be considered. The most popular external damping devices are viscous dampers and tuned mass dampers (TMD). The efficiency of TMD is demonstrated on the example of a footbridge prone to vibrations induced by pedestrians. It is shown that if the TMD is tuned quite precisely the reduction of accelerations can be very significant