This paper presents the design and testing of an innovative methodology to assess wind loads on façade louvers. It consists in wind tunnel tests with multiple model scales (1:70, 1:4 and 1:1) and different measurement methods. The leading idea is to assess the louvers’ wind loads along the façade from the 1:70 scale test, and then consider the real fins’ aerodynamic to correctly scale the results of the smaller scale to the full scale loads. The small scale (1:70) is utilized to represent the whole building’s details, the atmospheric boundary layer and the side effects coming from the surrounding constructions; the louvers are shifted from the façade by a porous walkway forming a second outer wall. Pressure measurements on fins are carried out with simplified thin flat louvers instrumented with pressure sensors on both sides (net-pressure) and the same is done with a couple of FBG sensors to compensate for the thermal effects and to assess wind loading on the whole element (global measurement). That scale (1:70), however, does not allow maintaining the Reynolds similarity in the model of the louvers, therefore two further scales are considered: 1:4 model scale representing a corner of the building (tested with alternately rectangular and elliptical shape of the louvers) and a sectional model of the 1:4 and 1:1 scale fins to assess the Reynolds dependency of the measured loads. The 1:4 corner model is properly designed to assess the dependency of the loads on the louver’s shape, the flow characteristics and on the porosity of the outer wall (louvers’ layout). Simultaneously the flow around a building’s corner is analysed to find out the louvers’ pro and cons on the building cladding’s net pressures, finding a favourable reduction of the suctions. The whole methodology has been experimented measuring wind loads on the external louvers of the Amorepacific HQ (Seoul, Korea) by means of a test in the PoliMi’s boundary layer wind tunnel (WT). The methodology has proved to be suitable to the initial purpose and the results allowed optimizing the distribution of louvers’ wind load and assessing their effect on the corner’s flow.
L’elaborato presenta il progetto e la sperimentazione di una metodologia per valutare, tramite test in galleria del vento, i carichi sulle lamelle frangisole degli edifici alti. La metodologia consta dell’applicazione di un approccio multiscala (1:70, 1:4 e 1:1) e dell’utilizzo di due tipologie di misura: puntuale (prese di pressione) e globale tramite sensori in fibra ottica. L’idea è valutare la distribuzione dei carichi del vento sulle lamelle dal modello in scala 1:70 e poi avere altri test per scalare i risultati al vero tenendo in considerazione l’aerodinamica esatta. L’intera metodologia è stata sperimentata nella galleria del vento del Politecnico di Milano, misurando i carichi dovuti al vento sulle lamelle frangisole dell’AmorePacific HQ situato a Seoul ( Korea). La prima scala (1:70) viene considerata per rappresentare l’intero edificio nei suoi dettagli e valutare gli effetti dovuti allo strato limite ed alle costruzioni circostanti; le lamelle vengono modellate con forma rettangolare e fissate su di una passerella che le separa dalla facciata. Le misure sono effettuate tramite le prese di pressione su entrambe le facciate delle lamelle ed analogamente è fatto con una coppia di sensori FBG per compensare gli effetti termici e misurare i carichi integrali sull’elemento. Non permettendo la scala 1:70 di mantenere la similitudine del n° di Reynolds, si considerano due ulteriori modelli: un modello in scala 1:4 che riproduce un angolo dell’edificio (montando alternatamente lamelle rettangolari ed ellittiche) ed il modello sezionale delle lamelle in scala 1:4 ed 1:1. I modelli 1:4 ed 1:1 sono progettati in modo tale da valutare la variazione dei carichi in funzione della forma delle lamelle, delle caratteristiche del flusso e della porosità dovuta al loro schema di posizionamento. Si è inoltre studiata l’influenza delle lamelle sul campo di pressioni intorno ad un angolo caratteristico dell’edificio, riscontrando un effetto positivo nel ridurre le depressioni sulla facciata. La metodologia è risultata essere particolarmente adatta allo scopo ed i risultati hanno dato la possibilità di ottimizzare i carichi del vento sui supporti delle lamelle.
Wind tunnel methodology to study wind loads on facade louvers
RACCO, SERGIO
2014/2015
Abstract
This paper presents the design and testing of an innovative methodology to assess wind loads on façade louvers. It consists in wind tunnel tests with multiple model scales (1:70, 1:4 and 1:1) and different measurement methods. The leading idea is to assess the louvers’ wind loads along the façade from the 1:70 scale test, and then consider the real fins’ aerodynamic to correctly scale the results of the smaller scale to the full scale loads. The small scale (1:70) is utilized to represent the whole building’s details, the atmospheric boundary layer and the side effects coming from the surrounding constructions; the louvers are shifted from the façade by a porous walkway forming a second outer wall. Pressure measurements on fins are carried out with simplified thin flat louvers instrumented with pressure sensors on both sides (net-pressure) and the same is done with a couple of FBG sensors to compensate for the thermal effects and to assess wind loading on the whole element (global measurement). That scale (1:70), however, does not allow maintaining the Reynolds similarity in the model of the louvers, therefore two further scales are considered: 1:4 model scale representing a corner of the building (tested with alternately rectangular and elliptical shape of the louvers) and a sectional model of the 1:4 and 1:1 scale fins to assess the Reynolds dependency of the measured loads. The 1:4 corner model is properly designed to assess the dependency of the loads on the louver’s shape, the flow characteristics and on the porosity of the outer wall (louvers’ layout). Simultaneously the flow around a building’s corner is analysed to find out the louvers’ pro and cons on the building cladding’s net pressures, finding a favourable reduction of the suctions. The whole methodology has been experimented measuring wind loads on the external louvers of the Amorepacific HQ (Seoul, Korea) by means of a test in the PoliMi’s boundary layer wind tunnel (WT). The methodology has proved to be suitable to the initial purpose and the results allowed optimizing the distribution of louvers’ wind load and assessing their effect on the corner’s flow.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/114042