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Experimental assessment of damping factors in concrete housing walls
Evaluación experimental de los factores de amortiguamiento en muros de concreto para vivienda
DOI:
https://doi.org/10.15446/ing.investig.v32n3.35939Keywords:
concrete wall, vibration period, damping factor, dynamic transfer function, shake table test (en)muros de concreto, periodo de vibración, factor de amortiguamiento, función de transferencia dinámica, ensayos en mesa vibratoria (es)
Thin walls having low concrete strength, minimum web steel ratios and web shear reinforcement made of welded wire meshes are commonly used in low-rise concrete housing. The damping factor commonly used for code-based dynamic analysis was evaluated based on seismic response measured during shake table tests of six low-rise concrete walls. The variables studied were the type of concrete (normal and lightweight), the web steel shear ratio (0.125% and 0.25%), the type of web shear reinforcement (deformed bars and welded wire meshes) and the effect of openings (doors and windows). Dynamic properties were evaluated considering the advantages of frequency-domain system identification, using the dynamic transfer function amplitude fitting method. The effect of failure mode on damping factor is discussed. An equation for estimating damping associated with a particular vibration period value is also proposed. It was observed that a 5% damping factor (assumed for dynamic analysis of concrete housing in the range of lineal elastic behaviour) was consistent with the values measured here.
En viviendas de concreto de baja altura se emplean usualmente muros delgados con baja resistencia del concreto, cuantías mínimas de refuerzo y mallas de alambre soldado para refuerzo a cortante en el alma. Con base en la respuesta sísmica medida durante el ensayo en mesa vibratoria de seis muros de concreto de baja altura se evalúa el factor de amortiguamiento que se utiliza usualmente en el análisis dinámico especificado en los reglamentos. Las variables estudiadas fueron el tipo de concreto (peso normal y ligero), la cuantía - 0,125% y 0,25%- y el tipo de refuerzo a cortante en el alma -barras corrugadas y malla de alambre soldado- y el efecto de aberturas (puerta y ventana). Tomando en cuenta las ventajas de los sistemas de identificación en el dominio de la frecuencia, las propiedades dinámicas se evaluaron utilizando el método de ajuste de amplitud de la función de transferencia dinámica. En el artículo se discute el efecto del modo de falla sobre el factor de amortiguamiento y se propone una ecuación para estimar el amortiguamiento asociado a un determinado valor del periodo de vibración. Se observó que el factor de amortiguamiento del 5%, supuesto en el análisis dinámico de viviendas de concreto en el intervalo de comportamiento elástico lineal, es consistente con los valores medidos.
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References
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Carrillo J., Evaluation of shear behavior of concrete walls using dynamic tests, PhD thesis, Universidad Nacional Autónoma de México, UNAM, 2011 (in Spanish).
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Copyright (c) 2012 Julián Carrillo, Sergio M. Alcocer, Giovanni González
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