ANALYSIS OF A TUNED LIQUID COLUMN DAMPER IN NON-LINEAR STRUCTURES SUBJECTED TO SEISMIC EXCITATIONS

Abstract

THE BEHAVIOR OF THE TUNED LIQUID COLUMN DAMPER (TLCD) IS ANALYZED IN THE CONTROL OF NON-LINEAR STRUCTURES SUBJECTED TO RANDOM SEISMIC EXCITATIONS. THE STRUCTURE IS MODELED AS A SYSTEM OF ONE DEGREE OF FREEDOM WITH INCURSION IN THE NON-LINEAR RANGE. THE BOUC-WEN HYSTERETIC MODEL IS USED TO MODEL THE STRUCTURE'S NON-LINEAR BEHAVIOR. A STATIONARY STOCHASTIC ANALYSIS IS PERFORMED IN THE FREQUENCY'S DOMAIN. AN EQUIVALENT STATISTICAL LINEARIZATION WAS USED FOR THE ANALYSIS OF THE MAIN SYSTEM AND THE TLCD. THE TLCD PARAMETERS CONSIDERED FOR THE OPTIMIZATION PROCESS WERE THE FREQUENCY AND THE HEAD LOSS COEFFICIENT. TWO TARGET FUNCTIONS WERE CONSIDERED, (I) REDUCTION OF THE MAIN SYSTEM'S DISPLACEMENT, (II) REDUCTION OF THE HYSTERETIC ENERGY. TWO RANDOM PROCESSES WERE CONSIDERED AS SEISMIC EXCITATION, FIRST A BROAD BANDWIDTH PROCESS AND SECONDLY A NARROW BANDWIDTH PROCESS. THE RESULTS SHOW THAT FOR A BROAD BANDWIDTH PROCESS, THE TLCD TENDS TO TUNE WITH THE SYSTEM´S LINEAR EQUIVALENT FREQUENCY IN THE CASE WITHOUT TLCD, WHILE FOR THE NARROW BANDWIDTH PROCESS, IT TUNES (TLCD) WITH THE DOMINANT FREQUENCY OF THE INPUT. IT IS SEEN THAT THE TLCD BECOMES DETUNED WITH REGARD TO THE STRUCTURE'S FREQUENCY AS THE STRUCURE BECOMES MORE NON-LINEAR. IT IS ALSO SEEN THAT THE TLCD'S OPTIMAL TUNING RATIO IS UNSENSITIVE TO THE DEVICE'S MASS RATIO AND THE MAIN SYSTEM'S DAMPING RATIO. IT IS ALSO CONCLUDED THAT IN CASE OF  FLEXIBLE STRUCTURES, THE OPTIMAL HEAD LOSS COEFFICIENT TENDS TO BE LOWER AND INCREASES WITH REGARD TO ITS LENGTH RATIO. IT IS SEEN THAT THE TLCD'S EFFECTIVENESS IS GREATER FOR THE DEVICE'S HIGHER MASS RATIOS. IN ADDITION, IT IS FOUND THAT THE OPTIMAL TLCD BECOMES LESS EFFECTIVE AS THE STRUCTURE ENTERS THE NON-LINEAR RANGE, SHOWING LOWER EFFICIENCY THAN WHAT IS SEEN IN THE LITERATURE FOR OPTIMAL TLCDS IN LINEAR STRUCTURES.