Concept on positioning of Columns

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.

Objective : To under stand the vertical and horizontal Impact in seismic behaviour of structure and to find the irregularities in structure.

Answer:

Identifying the symmetry of the structure in both directions:

• It can be identify by the dividing the layout in to half at vertical direction
• The above lay out looks inverted to each part by these we can decide that it is symmetry in Y direction

• Similarly, for X direction we need to divide the layout in horizontal direction .
• By observing the above plan results symmetry in X direction.

Identifying the Bi directional stiffness :

• The columns are connected with beam in horizontal direction on both ends, it states that any end of forces earthquake forces

will be transfers at the ends of the building in horizontal direction.

• Similarly at vertical direction the columns are not connected with beams up to ends except both ends of column
• So the lateral loads will be diverted to another direction to reach next bay and causes major forces diversion
• The above plan states that weak in bi-directional stiffness in Y direction.

Investigation of ductility :

Where as the higher stiffness would reduces the ductility at X - direction and at Y- direction less in stiffness states more in ductility.

2.

Objective : To find the possible sources of irregularity in building shown below.

Identifying the possible irregularities:

Vertical irregularity: The plan area is larger than floor area and the floor area is reducing as the change as increasing height.

It should be check with the reference code book IS 1893-2016.

According to IS 1893-2016 Table -6 (iii) states that

Soft story : Uncovered opening space in 6^th floor , as there is no occupancy or wall this will leads to plastic hing formation as the columns

According to IS 1893-2016 FIG : 4A

Slopy base : The building is constructed in slopy ground at one side and it varies in stiffness

• Few levels may be subjected to soft story mechanism

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Q3:

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.

Open ground floor : The ground floor leads to soft story meachanism

Mass irregularity in floors : The rooms are filled with higher mass then bay of corridor leads to mass irregularity.

Stair case at top corner : stair case portion are stiffer than other pats of concrete element

No framing connection along y direction- There is no beams are connected in Y- direction of columns the lateral loads in Y- direction are hardly to transfer.

Beams are connercted connected along colomn at minor axsis: The colums having longer dimension in Y- direction and they are more stiffer but the beams are connected in X- direction which would attract much lesser. ther vertical forces hardly to transfer.

Variation in column size :

The internal columns dimensions are higher than external columns it significates lateral drift of column.