In last a few years there has been a lot of talks in Indian construction industry about designing the buildings earthquake resistant because of some serious earthquake incidents happened in the past and less or no damaging tremors that we are experiencing in some intervals. More and less majority of developers, structural consultants, architects and up to some extent end users are aware about this issue. Structural consultant ensures earthquake resistance in design.
Structural engineer analyzes the structure for seismic forces, design structural members, and further produces the good for construction (GFC) drawings incorporating ductile detailing requirement as prescribed in design codes. Contractor receives the drawings and does construction either directly using the GFC drawings (which is not advisable as some of the information in GFCs are typical which has to be elaborated on case basis for accurate and smooth construction especially for big projects) or by preparing the detailed shop drawings on the basis of GFCs. Now following questions are raised;
- Is the structure constructed earthquake resistant?
- Does the earthquake resistant design alone ensure the earthquake resistance of the structure?
- Have all the structural design details as prescribed by the consultant been incorporated at site?
- Is there a gap between structure constructed on paper and structure constructed at site?
- Why there is a gap? If there is a gap, can this be eliminated?
In my opinion, good for construction drawings, produced by structural consultant, alone cannot ensure the earthquake resistance of the structure constructed at site. As even if contractor has captured all the information correctly as mentioned in GFCs in terms of structural member sizes, reinforcement diameter, and no. of rebars etc., still there are a lot of details at junctions for example beam-column junction, and rebar splicing, which have to be interpreted and captured rightly by the contractor from the drawings. These details are not so detailed in GFCs and only typical information are provided, which have to be explored further by the contractor on case to case basis. And, this requires knowledge about the structural engineering. All these details are very crucial when it comes to earthquake resistance of a structure. If junctions, splices etc. are not detailed correctly at site, no matter how good the structural design is, no matter how much steel has been put in the building, still the structure will have weakness for earthquake forces. There is a gap between structural design done by consultant at office and building construction done by contractor at site.
This gap between design and construction can be eliminated by extending the project structural consultant role beyond the issuance of GFC drawings. The consultant should also be responsible for checking the shop drawings prepared by the contractor, especially the shop drawings capturing all the junction details. Structural consultant shall be engaged on a project right starting from the concept design stage to the complete structural construction of the project.
Today, this kind of extended role of structural consultant in any project is rarity in India, which actually should be a norm if we really want to be 100% sure about the earthquake resistance of at least the newly constructed buildings.