International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 10 Issue: 06 | Jun 2023
p-ISSN: 2395-0072
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Impact of fault line on behaviour of flat slab under vertical motion of earthquake Abhishek Chandrakant Ghela1, Aakash Rajeshkumar Suthar2 1 Student Civil Engineering Department, L.J.I.E.T. Ahmadabad, Gujarat, India 2 Professor Civil Engineering Department, L.J.I.E.T. Ahmadabad, Gujarat, India ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - The effects of vertical acceleration of the ground
Due to the belief that vertical acceleration is often smaller than horizontal acceleration, vertical ground motion has received less study. The vertical component of the ground motion was found to be greater than the horizontal component during the most recent earthquakes. Most design codes, including IS-1893 (2016), accept Newmark and Hall's (1982) recommendation that the design vertical spectrum should be 2/3 of the design horizontal spectrum.
on flat slab building are presented in this paper. In the current environment, most design standards, including IS 1893-2016, recommend that the vertical acceleration element of an earthquake be designed as 2/3 of the horizontal. During recent quakes, the vertical element of ground motion was discovered to be greater than the horizontal element. It is consequently vital to investigate structural reaction in this sort of earthquake, where the vertical element's peak ground acceleration (PGA) may reach two-thirds of the horizontal element. Time history analysis was done in this study utilising 5 unscaled seismic data. To account for the influence of vertical ground vibrations, 5 various structural systems were investigated, including a drop panel, shear walls, and three flat plates of varying thickness. Variations in several parameters such as axial force for column at several locations in building, punching shear at the junction of slab & column, and deflection of slab have been examined. The results of the calculations demonstrate that vertical ground movement has a significant impact on the flat slab structure in regards to axial force variations, punching shear, and deflection of slab.
Within 30 km of the source, the V/H ratio is crucial, according to Papazoglou and Elnashai (1996) (1), and the 2/3 rule is found to be on the cautious side for events that occur close to the source. Nipan Bhandar Kayastha and Rama Debbarma (2016) (2) performed analysis on G+3 building by SAP 2000. They considered seismic zone V with soft soil strata. They chose 5 different structural configurations consist of conventional RC frame structure, flat slab with dropped, column head & shear wall. Flat slab with shear wall at periphery performs batter that general RC frame. It also gives maximum base shear compare to other models. Story displacement, Story drift are minimum in flat slab with shear walls. Natural period is also very less.
Key Words: flat slab, flat plate, vertical ground motion, vertical earthquake motion, vertical PGA, response of flat slab, time history analysis
Further, a study on vertical ground motion and its impact on engineered structures by Bipin Shrestha (2009) (3) found that the current design process could have catastrophic results. It is advised that sites located within 20 km of the main active fault be designed to account for the combined effect of horizontal and vertical ground motion. The V/H ratios for near-source seismic events can be higher than 2/3. The primary impact of the vertical ground motion on the structure is to put more axial strain on the vertical load bearing element. When a vertical motion with similar amplitude to a horizontal motion occurs, it is seen that the axial force is typically greater than the equivalent transverse loading. It is also noted that variation of axial force is more on upper floor rather than lower floor.
1.INTRODUCTION The reinforced concrete flat slab technique is being used extensively for residential and commercial development in various regions, including high seismic zones. Flat slab is fashionable and easy to construct. It also helps to maximise the height between the ceiling and the floor. Below are the types of flat slabs: 1.
Flat Slabs without drop and column head.
2.
Flat Slabs with column head.
3.
Flat Slabs with drop
4.
Flat Slabs with drop and column head
Researchers Siyun Kim, Sung Jig Kim, and Chunho Chang (4) The effect of vertical ground movement on the 13 reinforced concrete structures with various geometric shapes was studied analytically. Horizontal ground motion has a greater impact on lateral displacement than vertical movement of the ground. Vertical ground movement caused by earthquakes is incorporated, the axial force fluctuation on the Reinforced concrete columns in the 1st story increases significantly, up to roughly 240%. This significant axial force
Due to its low lateral stiffness, flat slabs wobble significantly during seismic events, and the most dangerous failure in flat slabs is punching shear failure. If this occurs, the surrounding connections must be able to handle and redistributed pressures else it might cause a progressive failure of the structure.
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