Ground Vibrations: Effects of masses placed on or in the ground
Authors
Paven, Ioan-Oreste ; Muresan, Mihai ; Muresan, Liviu-Ionut
Term
4. term
Education
Publication year
2016
Submitted on
2016-06-09
Pages
131
Abstract
Byaktiviteter som trafik og byggeri skaber jordbårne vibrationer, der kan påvirke bygninger. Dette projekt undersøger, hvordan vibrationer forplanter sig gennem jord, og afprøver en måde at dæmpe dem på: at placere ekstra masser mellem vibrationskilden og modtageren (en bygning eller sensor), enten på jordoverfladen eller nedgravet. Arbejdet kombinerer to tilgange. For det første småskalaforsøg, hvor vibrationsforholdene skaleres til laboratoriestørrelse med tilgængelige materialer. Responsen måles med accelerometre og en impulshammer og analyseres i PULSE som frekvensresponsfunktioner (FRF), der viser, hvordan systemet reagerer ved forskellige frekvenser. Det førte til to forsøgsopstillinger, begge med mulighed for forskellige konfigurationer af masser: (1) et enkelt jordlag med masser placeret på overfladen mellem kilde (exciter) og modtager og (2) et tykkere jordlag med masser nedgravet i jorden. For det andet udvikles numeriske modeller i Abaqus CAE med samme materialer og randbetingelser som i forsøgene. De eksperimentelle og numeriske resultater sammenlignes for at vurdere, hvor godt modellerne kan gengive fænomenet. De numeriske modeller stemte bedst overens med relativt simple opstillinger, hvor færre usikkerheder forventes. Effekten af de tilføjede masser kunne ses i alle konfigurationer: accelerationer blev dæmpet i visse frekvensområder og forøget i andre. Den mest positive indvirkning blev observeret, når flere masser var placeret periodisk mellem kilde og modtager.
Urban activities such as traffic and construction generate ground-borne vibrations that can affect buildings. This project examines how these vibrations travel through soil and tests a way to reduce their strength: placing added masses between the vibration source and the receiver (a building or sensor), either on the ground surface or buried. The study uses two complementary approaches. First, small-scale laboratory experiments, where the vibration conditions are scaled to lab size using accessible materials. Responses were measured with accelerometers and an impact hammer, and analyzed in PULSE as frequency response functions (FRF), which show how the system behaves across different frequencies. This led to two test setups, both allowing different mass configurations: (1) a single soil layer with masses on the surface between the source (exciter) and the receiver, and (2) a thicker soil layer with masses embedded in the ground. Second, numerical models were built in Abaqus CAE using the same materials and boundary conditions as in the experiments. Experimental and numerical results were compared to assess how well the simulations reproduce the phenomenon. The numerical models agreed better with relatively simple setups where fewer uncertainties are expected. In all configurations, the added masses influenced the response: accelerations were reduced in some frequency ranges and increased in others. The most positive effect was observed when multiple masses were arranged periodically between the source and receiver.
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