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Natural period and vertical distribution of base shear in confined masonry buildings using ambient vibration test
Bulletin of Earthquake Engineering ( IF 4.6 ) Pub Date : 2021-01-31 , DOI: 10.1007/s10518-021-01046-8
Pranav Chakra-Varthy , Dhiman Basu

In semi-urban setting where availability of land can afford construction of low-rise buildings, confined masonry may compete with other alternatives of seismic resilient system provided well-articulated design standards and construction guidelines are available. Most seismic standards do not make explicit recommendations on the natural period and vertical distribution of base shear for the design of confined masonry buildings. In such a case, one of the two alternatives, such as (1) reinforced concrete (RC) frame building with masonry infill walls and (2) RC frame building with structural walls, is tacitly extrapolated. This paper is first aimed to explore the possible recommendations from the ambient vibration testing of a class of confined masonry building stock. Nine (G + 3) confined masonry hostel buildings are considered for Ambient Vibration Testing (AVT). Recorded signatures are processed and modal characteristics (primarily restricted to the first triplet of fundamental modes) are extracted. Each building is modelled numerically and fine-tuned followed by a comparison of natural frequencies and mode shapes in numerical model and experimental results. The fine-tuned numerical models are analysed against a set of recorded ground motions. Possible design recommendations for natural period and distribution of base shear along the height are the key contributions. Empirical equation for natural periods is derived from the seismic code recommendation on that of reinforced concrete (RC) buildings but removing the bias contributed from the height shorter than one storey while using the experimental results. Distribution of the base shear along the height follows a parabolic profile with an exponent close to 0.4. Results of AVT indicate the inherent damping ratio on an average of about 5% which, however, may not be directly used for seismic excitation. The building stock used for AVT in this paper does not include considerable variations in height and different varieties of confined masonry constructions. Therefore, recommendations of this paper should be verified against a larger size of dispersed building stock.



中文翻译:

使用环境振动试验的密闭砖石建筑,基础剪力的自然周期和垂直分布

在半城市环境中,可用土地可以支付低层建筑的费用,如果有明确的设计标准和施工准则,承压砌体可能会与其他抗震系统替代方案竞争。大多数地震标准没有对封闭式砖石建筑设计的自然周期和基础剪力的垂直分布提出明确建议。在这种情况下,默认选择两个备选方案之一,例如(1)带砌体填充墙的钢筋混凝土(RC)框架建筑和(2)带结构墙的RC框架建筑。本文首先旨在探讨一类密闭砌体建筑房屋的环境振动测试可能提出的建议。九座(G + 3)受限的砖砌宿舍楼被考虑用于环境振动测试(AVT)。处理记录的签名并提取模式特征(主要限于基本模式的第一个三元组)。对每座建筑物进行数值建模和微调,然后在数值模型和实验结果中比较固有频率和振型。针对一组记录的地面运动分析了微调的数值模型。对于自然周期和沿高度分布的基础剪力的可能设计建议是关键的贡献。自然周期的经验方程式是根据关于钢筋混凝土(RC)建筑物的抗震规范的建议推导出的,但是在使用实验结果的同时,消除了由于高度短于一层而造成的偏差。基本剪应力沿高度的分布遵循抛物线形,指数接近0.4。AVT的结果表明,固有阻尼比平均约为5%,但是它可能无法直接用于地震激励。本文中用于AVT的建筑存量不包括高度的显着变化以及密闭砖石结构的不同品种。因此,应针对较大规模的分散建筑材料来验证本文的建议。本文中用于AVT的建筑存量不包括高度的显着变化以及密闭砖石结构的不同品种。因此,应针对较大规模的分散建筑材料来验证本文的建议。本文中用于AVT的建筑存量不包括高度的显着变化以及密闭砖石结构的不同品种。因此,应针对较大规模的分散建筑材料来验证本文的建议。

更新日期:2021-01-31
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