Kattumaanap Poriyaalar october 2013 | Page 54

be ‘controlled’ and kept within permissible limits. Take another example, if a lintel above a doorway deflects too much, it may cause warping of the door frame below it and, consequently, the door itself may not open or close properly. Cracking is ugly and may or may not be indicative of a structural problem. But it may, in itself, lead to problems. For example, if cracking occurs on the outside face of a reinforced concrete wall then rain water may penetrate and cause corrosion of the steel reinforcement within the concrete. Responsibilities of a Structural Designer. A structural designer should create a functional, economic and most importantly , safe structure for the public to enjoy. The following are to be considered during structural design of a building: (a) Proper foundation to be designed based on soil profile and SBC. Avoid eccentric or floating column at the foundation level. If not possible, even extra cost is incurred , connect the eccentric footings to the nearest footing and make it combined with strap beam arrangement. (b) Interact with architect and plan the structure layout from stability point of view. i.e Plan a frame layout which is connected by beams and columns before dividing the floor area for functional requirement. Proper connection of beam to column is very important during seismic loading. Secondary beams can to be planned to meet the other requirements. Stability is very essential for any good structure to transfer the forces smoothly to the ground. (c) As far as possible , floating columns are to be avoided. Floating column will not allow smooth flow of force from beam to column and foundation . It produces heavy moment during earthquake and cause damages to the building. (d) Concealed beams are adopted to support roof and connect to columns. Concealed beam in a slab has no capacity to behave as regular beam. 125mm thick slab with 25mm cover can have a maximum gap between top and bottom reinforcement of 55mm, which is insufficient to provide beam action. However, it can minimize stress concentration and useful under half brick wall. Therefore, it is recommended that concealed beam concept should not be considered under full wall load or as a connecting member between two columns. (e) Beam width should not be restricted only to wall width. Beam width should satisfy code requirements, as per seismic code IS 13920, the width of a beam shall be 300mm beam for a beam length more than 5m. Interact with architect and permit the beams to run in side the rooms if required for better performance during seismic load. è † ´ ñ £ ù (f) Structural engineer should advise the client to preserve the copy of structural details and use it during any addition/ alternation to the building in future . Adding the extra floor Š without knowing the structural strength is not advisable. Many buildings have failed due to ªð over loading. £ P Conclusion. ò There are many multistoried buildings have failed and collapsed in various cities. Owner £ and architect of a building should give equal importance to the safety and strength of the ÷ building and allow the structural engineer to design a structure to with stand all forces ˜ including seismic load. fl;Lkhdg; nghwpahsh; 56 mf;Nlhgh; 2013