Chapter 7Provisions for Structural Safety

7.1 Structural design and safety.- For any building under the jurisdiction of these byelaws structural/retrofitting design shall only be carried out by a registered Structural Engineer on Record (SER). Proof checking of various designs/ reports shall be carried out by competent authority as per Table 7.1wherever applicable.

7.1.1 Additional Provisions for natural hazard prone areas.- Generally, the structural design of foundations, elements of masonry, timber, plain concrete, reinforced concrete, pre-stressed concrete and structural steel shall conform to the provisions of Part 6: Structural Design –

Section– 1 Loads, Forces and Effects

Section– 2 Soils and Foundations,

Section– 3 Timber and Bamboo,

Section– 4 Masonry,

Section– 5 Concrete

Section– 6 Steel

Section– 7 Prefabrication Systems, Building and Mixed /Composite Construction of National Building Code of India (NBC), taking into consideration the Indian Standards as given below.

(1) IS: 456:2000 ‘Code of Practice for Plain and Reinforced Concrete’;

(2) IS: 800-2007 ‘Code of Practice for General Construction in Steel’;

(3) IS: 801-1975 ‘Code of Practice for Use of Cold Formal Light Gauge Steel Structural Members in General Building Construction’;

(4) IS 875 (Part 2):1987 Design loads (other than earthquake) for buildings and structures Part2 Imposed Loads;

(5) IS 875 (Part 3):1987 Design loads (other than earthquake) for buildings and structures Part 3 Wind Loads;

6. IS 875 (Part 4):1987 Design loads (other than earthquake) for buildings and structures Part 4 Snow Loads;

7. IS 875 (Part 5):1987 Design loads (other than earthquake) for buildings and structures Part 5 special loads and load combination;

8. IS: 883:1994 ‘Code of Practice for Design of Structural Timber in Building;

9. IS: 1904:1986 (R 2005) ‘Code of Practice for Structural Safety of Buildings: Foundation’;

10. IS 1905:1987 ‘Code of Practice for Structural Safety of Buildings: Masonry Walls; and

11. IS 2911(Part 1): Section 1: 2010 ‘Code of Practice for Design and Construction of Pile Foundation Section 1

Part 1: Section 2 Bored Cast-in-situ Piles

Part 1: Section 3 Driven Precast Concrete Piles

Part 1: Section 4 Bored Precast Concrete Piles

Part 2: Timber Piles

Part 3: Under Reamed Piles

Part 4: Load Test on Piles

For Cyclone/Wind Storm Protection

(12) IS 875 (3):1987 ‘Code of Practice for Design Loads (other than Earthquake) for Buildings and Structures, Part 3, Wind Loads’

(13) Guidelines (Based on IS 875 (3)-1987) for improving the Cyclonic Resistance of Low rise houses and other building.

(14) IS: 1893 (Part 1)-2002 ‘Criteria for Earthquake Resistant Design of Structures (Fifth Revision)’

15. IS: 13920-1993 ‘Ductile Detailing of reinforced Concrete structures subjected to Seismic Forces-Code of Practice

(16) IS: 4326-2013 ‘Earthquake Resistant Design and construction of buildings code of practice (second revision)’

(17) IS: 13828-1993 ‘Improving earthquake resistance of low strength masonry buildingsguidelines

(18) IS: 13827:1993 ‘Improving Earthquake Resistance of Earthen Buildings-Guidelines

(19) IS: 13935-2009 ‘Seismic Evaluation, Repair and Seismic Strengthening of Buildings - Guidelines’

(20) IS 14458 (Part 1): 1998 Guidelines for retaining wall for hill area: Part1Selection of type of wall.

(21) IS 14458 (Part 2): 1997 Guidelines for retaining wall for hill area: Part 2 Design of retaining/breast walls

(22) IS 14458 (Part 3): 1998 Guidelines for retaining wall for hill area: Part 3Construction of dry stone walls

(23) IS 14496 (Part 2): 1998 Guidelines for preparation of landslide – Hazard zonation maps in mountainous terrains: Part 2 Macro-zonation.

Note: Whenever an Indian Standard including those referred in the National Building Code or the National Building Code is referred, the latest revision of the same shall be followed except specific criteria, if any, mentioned above against that code.

7.1.2 Structural Design Basis Report (SDBR).- In compliance of the design with the above Indian Standard, the Structural Engineer on Record will submit a structural design basis report in the Performa attached herewith covering the essential safety requirements specified in the Standard.

The ‘Structural Design Basis Report (SDBR)’consists of four parts

Part 1: General Information/ Data

Part 2: Load Bearing Masonry Buildings

Part 3: Reinforced Concrete Buildings

Part 4: Steel Buildings

(a) Drawings and Documents to be submitted for approval of appropriate authorities shall include SDBR as detailed below:

Part 1: Completed

Part 2: (if applicable) – completed

Part 3: (if applicable) – undertaking that completed Part 3 will be submitted before commencement of construction.

Part 4: (if applicable) – undertaking that completed Part 4 will be submitted before commencement of construction.

(b) SDBR as detailed below shall be submitted to the appropriate authority as soon as design of foundation is completed, but not later than one month prior to commencement of construction.

Part 1: Completed

Part-2, Part-3 or Part-4: (if applicable) Completed

7.1.3 Seismic strengthening/retrofitting.- Prior to seismic strengthening/retrofitting of any existing structure, evaluation of the existing structure as regards structural vulnerability in the specified wind/seismic hazard zone shall be carried out by the SER. If as per the evaluation of the SER the seismic resistance is assessed to be less than the specified minimum seismic resistance as given in the note below, action will be initiated to carry out the upgrading of the seismic resistance of the building as per applicable standard guidelines.

Note:

(1). For masonry buildings reference shall be made to IS 4326 and IS 13935

(2). For concrete buildings and structures reference shall be made to IS15988: 2013 Seismic

evaluation and strengthening of existing RCC buildings.

7.1.4 Buildings with Soft Storey.- In case buildings with a flexible storeys, such as the ground storey consisting of open spaces for parking that is ‘Stilt buildings’ or any other storey with open halls, special arrangements are to be made to increase the lateral strength and stiffness of the soft/open storey such as Steel bracing / Shear walls / Brick infill’s between columns. Dynamic analysis of building is to be carried out including the strength and stiffness effects of infills and inelastic deformations in the members, particularly, those in the soft storey, and the structural members are to be designed accordingly.

Alternatively, the following design criteria are to be adopted after carrying out the earthquake analysis, neglecting the effect of infill walls in other storeys:

(a). The columns and beams of the soft storey shall be designed for 2.5 times the storey shears and moments, calculated under seismic loads specified in the other relevant clauses; or,

(b). Besides the columns designed and detailed for the calculated storey shears and moments, shear walls shall be placed symmetrically in both directions of the building as far away from the Centre of the building as feasible; to be designed exclusively for 1.5 times the lateral storey shear force calculated as before. For details of design and provisions, IS 1893, Part 1 shall be referred.