Concept on positioning of Columns

Question 1:

Comment on the layout of the framing plan concerning earthquake resistance in the two horizontal directions X or Y (dots are columns, lines depict beams). Look into aspects of symmetry, redundancy and bi-directional stiffness and ductility.

Ans

Investigation of the framing plan with respect of symmetry in X direction

If we split the plan what we probably are, it will look minor. So we can’t do the given plan as symmetric in X direction

Investigation of the framing plan with respect to symmetry in Y direction

if we split the plan horizontally ask, it will look mirrored so we conclude the given plan is symmetry in Y direction

Contd.,

Investigation of the framing plan with respect of redundancy in X direction

Natalie next direction on comparatively more antibiotic space So the structure is more redundant in next direction expect the top and bottom column rows are having quite longest span

Investigation of the framing plan with respect of redundancy in Y direction

The column in Y direction are cooperatively lesser but evenly spaced. So the structure is redundant but lesser than that of X direction

Investigation with respect to buy directional stiffness

• The column with the horizontal direction are connected with straight to straight beams This means any lateral load [systemic force in X direction] passing from left end of the building will have its path straight till it reaches right end of the building. Sir no more or less possibility of force diversion take place
• The column in vertical direction are not connected with straight to straight beams. Show a lateral load passing from south side of the building Will get diverted to east and West direction to reach next bay. There will be major post diversion take place with seismic force in white direction. The framing plan is weak with respect to bidirectional stiffness in Y direction.
• Prima facie, hey Cortana the aspect ratio of the plant clearly hints more corner in X direction compared to Y direction. It will result in higher stiffness of the building in X direction which would reduce ductility in X axis
• Moreover, the force will easily pass from one way to its next due to beam alignment. Whereas , the Y force will struggle to pass through the north south beams or arranged in zigzag which leads to the discontinuous bracing.
• We can control that the given framing plan is more ductile in Y direction than that of X direction

Question 2:

What are the possible sources of irregularity in the building shown here? Explain how, as an engineer, each of these irregularities should be dealt with.

Ans.

• Vertical irregularity - the building area is larger in bottom stories. The floor plan areas are getting reduced with increase in height. These buildings offset has to be cross checked with reference to IS 1893-2016 table 6 serial number iii
• Soft storey – the building has uncovered open space in 6^th floor as there is no occupancy of our partition wall this will lead to plastic hinge formation at the columns [with reference to IS1893-2016 figure 4A] this has to be checked under sufficient design
• Slopy Base – the building is constructed on a sloping ground at one side This will lead to significant variance in the stiffness [with reference to IS1893-2016 figure 5E] fuel levels may be subjected to soft story mechanism.

Question 3:

A 4-storey hotel building has an open ground floor for the restaurant. Story 2 to 4 have one row of rooms along each long side in plan, separated by a corridor. The two short sides of the perimeter are fully in-filled in all storeys, except for certain openings at the ends of the corridor at storeys 2 to 4 and along the right-hand side of the ground floor. There is a staircase near the upper left-hand corner, with straight flights between landings at floor levels and in-between floors. Cross-section dimensions are written next to the member no. in meters.

Comment on the features of the structural design and of the layout of infills which are important for earthquake resistance and seismic performance. How do they relate to the almost full collapse of this building (the extreme left-hand bay with the staircase survived, as well as one long-side façade in the rear end, and the frame along the right-hand side in plan).

Ans

• Open ground floor – this denotes soft story mechanism acting in the building
• Rooms along to be separated by an open corridor – the base filled with rooms will have higher mass compared to the middle pale left open for corridor. This includes as irregularity along height and uniformly.
• Two short sides covered with infant walls – this means the buildings left and right sides periphery his most stiffer during seismic force especially along North South
• Staircase partition at left top corner – usually staircase and a lift to partitions are stiffer than other parts because of concentrated concrete Element. So the staircase partition contains most stiffness in the provided building plan.

Contd.,

• No frames connection along Y direction – we could see no structural beams provided along the vertical direction between column. This makes the building more vulnerable during the North South Seismic Force
• Beams connected along column minor axis – the columns are having longer dimension in Y direction. This means they are more stiffer along Y direction. But beams are running only along X direction which would attract much lesser lateral force and hardly transfer it.
• Variation in column sizes – the internal column are having a higher size compared to exterior column [this is common because of higher load demand] but this will lead to significant different in lateral drift to column. So the concrete floor has might have suffered heavy out of plain shear which would lead to collapse.