Designing an Earthquake resisting open ground storey building

Published on 16 Apr 2022. Written by Nidhi Tiwari

Increasing population has led to a drastic increase in the number of multi-storied buildings in recent years. With this, open ground buildings have also become popular as these buildings provide parking area on the ground floor of the building itself and thus, there is no need to worry about creating a parking arena.

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However, these buildings are also prone to damage due to the earthquake loads. Infill walls in the structure play a very important role in deciding the effect of the lateral loads on the structure. The upper storeys of the buildings have the presence of infill walls while the ground storey is almost completely devoid of them. Therefore, the upper storeys are much stiffer than the ground floor. As a result, the ground storey suffers the maximum horizontal displacement and the columns and beams in the ground storey suffer excessive sway load. Thus, it becomes very necessary for the columns and beams in the ground storey to have sufficient strength and stiffness.

Many measures have been taken to make the open ground buildings resistant to the lateral loads caused by earthquakes. In common practice, the infill walls are ignored in the analysis of the building design and this is compensated by using a multiplication factor of 2.5. According to the IS code 1893:2002, The columns and Beams of soft storey building are to be designed for 2.5 times the storey shears and bending moments calculated under seismic loads of bare frames.

However, this factor is not adequate in case of medium and low-rise buildings. Thus, it is necessary to check the applicability of the multiplication factor in such open ground storey buildings.

In this project, you have to check the applicability of the multiplication factor of 2.5 and to study the effect of infill strength and stiffness in seismic analysis of open ground storey buildings. Also, you will have to study the effect of infill strength and stiffness (with infill Opening) in the seismic analysis of Open ground storey building. The software used in the analysis will be the ETABS software where you will create a 3D model of a building and the infill structure will be brought into effect by the Diagonal Strut Approach. You then have to perform the linear and nonlinear analysis of different models and compare the results.

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Project Implementation:

1. As the first step to this project, you have to design a 3D model of the structure you want to analyse. You need to design an RC framed, open ground storey building with Special Moment Resisting Frame using the ETABS software.

For designing the model, you need to provide details like the type of structure, number of storeys, type of soil, height of the building, infill wall dimensions, column and beam dimensions, etc. These details will vary for different cases to help you in a detailed analysis.

2. You then have to specify the loads acting on the structure, The common loads are the dead load, live loads, lateral loads, floor finish, etc.
3. You have to specify the details of the equivalent strut in the model. The equivalent strut used in the model will be the one proposed by Mainstone in 1971 where the cross-sectional area of the strut was calculated by considering the sectional properties of the adjoining columns. With the mainstone equation, you can calculate the opening % of the infill.
4. Once your model is ready, you need to record the parameters like horizontal drift, base shear, shear force, bending moments, etc. These parameters have to calculated for various cases and the recorded results have to be compared.

Conclusion:

After a complete analysis of the various cases with different heights and strength, you will get an idea of the ideal case which will be most suitable for resisting the lateral earthquake loads on the building. Also, you will get to know whether the multiplication factor of 2.5 is adequate for designing structures or not.

SLDYK
Kit required to develop Designing an Earthquake resisting open ground storey building:

• No kit

Technologies you will learn by working on Designing an Earthquake resisting open ground storey building:

• Civil engineering
• ETABS

Any Questions?