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design philosophy in structure design in civil engineering


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this presentation contain design philosophies as per IS Code and designs for structure designs in civil engineering

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design philosophy in structure design in civil engineering

  1. 1. S.N.P.I.T. & R.C., UMRAKH DESIGN PHILOSOPHY - Professor Urvesh N.Barot - Assis. Professor Keyur P. Shah 1S.N.P.I.T. & R.C.
  2. 2. Presentation by:  Mehta Mrunali- 130490106064  Modi Nagma- 130490106065  Nakrani Akash- 130490106066  Nikam Sejal- 130490106067  Pansuriya Prashant- 130490106068  Patel Akshar- 130490106071 2S.N.P.I.T. & R.C.
  3. 3. DESIGN PHILOSOPHY The main buildings in the stadium complex are the stands, members and player's pavilion block, venue operating centre, media centre and landscaped seating stand apart from service buildings and underground structures. The structural system adopted for the buildings are concrete/structural steel framed conventional beam slab and column structures on pile caps over bored cast-in-situ concrete piles/pre-cast concrete piles/green heart timber piles. The slabs are proposed in composite construction with concrete on profiled metal decking (serving as reinforcement). The stands are designed with pre- cast bleachers on raker beams in concrete/structural steel 3S.N.P.I.T. & R.C.
  4. 4. . The roof covering the stands are designed with structural steel elements in profiled sections to match the architectural form. The columns in cast- in-situ concrete/structural steel have insert plates/base plates to seat the roof-supporting member. The structures are analysed for dead load, live load and wind loads as per the codal provisions. Waterproofing on concrete surfaces exposed to atmosphere is done with reinforced modified bituminous membrane and is protected by cement concrete tiles. The waterproofing of sunken slabs in toilets is also achieved with the same material. All structural steel surfaces are protected from corrosion with anti-corrosive paint. 4S.N.P.I.T. & R.C.
  5. 5. SERVICEABILITY:  It implies satisfactory performance of the structure under service loads, without discomfort to the user due ti excessive deflection, cracking, vibration and so on. Other considerations that comes under the preview of serviceability are durability, acoustic and thermal insulation etc.  The adverse effect of excessive deflections are: 1. it creates feeling of lack of safety 2. Asthetic view is spoiled. 3. Creates ponding of water on roof slabs 4. Cracking of floor finish materials 5. In machines, it result into misalignment of machines. S.N.P.I.T. & R.C. 5
  6. 6. DESIGN LOADS Dead Loads The self weight of the various elements are computed based on the unit weight of materials as given below: Material Unit Weight kN/m3 Steel 78.5 Plain Cement Concrete 24 Reinforced Cement Concrete 25 Cement Concrete Screed 24 Soil 20 6S.N.P.I.T. & R.C.
  7. 7. Imposed Loads As per BS:6399 (Part 1)-1996 the building is classified as Public Assembly building. The superimposed loads or otherwise live load is assessed based on the occupancy classification as per BS:6399(Part 1)-1996 for assembly building. The imposed loads (in kN/m2) considered are as listed below: 7S.N.P.I.T. & R.C.
  8. 8. Occupancy Classification Load (kN/m2 ) a) Assembly areas: 1) with fixed seats 4.0 2) without fixed seats 5.0 b) Kitchens, laundries 3.0 c) Stages 7.5 d) Corridors, hallways, stairs 4.0 e) Dressing rooms 2.0 f) Areas for equipment 2.0 g) Toilets and bathrooms 2.0 8S.N.P.I.T. & R.C.
  9. 9. On flat roofs, sloping roofs and curved roofs with slopes up to and including 10 degrees, the imposed loads due to use or occupancy of the buildings and the geometry of the roofs are given below: As per cl 6.2, BS:6399 (Part 1)-1996 a) For roofs with access provision 1.5 b) For roofs without access provision 0.75 On sloping roof of slope greater than 10o, as per clause 6.3 of BS:6399(Part1)-1996 the imposed loads (kN/m2 of the plan area) that are likely to act permanently are as follows: Waterproofing* 1.5 (On roof / terrace) Partitions 1.0 (wherever applicable) False ceiling 0.5 wherever applicable) 9S.N.P.I.T. & R.C.
  10. 10. Structural slab shall be sloped suitably to avoid achieving requisite slopes with screed/brick bat coba Bleachers are designed to resist a horizontal force applied to seats of 3.0 kN per linear meter along the line of seats and 1.5 kN per linear meter perpendicular to the line of seats. 10S.N.P.I.T. & R.C.
  11. 11. Wind Load The wind pressure is calculated based on the data furnished below and as per the provisions laid in BS:6399 (Part 2)-1997 Basic Wind speed = 50m/sec (As assessed from UBC) Maximum gust = 30mph (13.5m/sec) As given Mean probable = 50 years 11S.N.P.I.T. & R.C.
  12. 12. DESIGN LIFE OF STRUCTURE Building Type factor Kb = 1.0 Ground roughness category = town Built up areas with an average level of roof tops at least Ho =5m above GL Dynamic Augmentation Factor Cr =0.03 12S.N.P.I.T. & R.C.
  13. 13. Static Simplified method is used for design for wind loads with the following parameters as per cl 2.2 BS:6399 (Part2)-1997 Directional Factor Sd = 1.0 Altitude Factor Sa = 1.0 Seasonal Factor Ss = 1.0 Probability Factor Sp = 1.0 Site Wind Speed Vs = Vb x Sa x Sd x Ss x Sp = 50 x 1 x 1 x 1 x 1 x 1 = 50m/sec Effective Wind Speed = Vs x Sb Where Sb is the terrain and building factor obtained from cl of BS:6399(Part2)-1997 13S.N.P.I.T. & R.C.
  14. 14. Earthquake Load Guyana is not within the earthquake belts and also does not figure in the places listed in the seismological active zones. It has been mentioned that Guyana experiences tremors every 5-10 years. Earthquake loads are not considered for analysis and design. With the given conditions it is assumed that the wind load on the structure would be sufficient for the lateral loads that would be generated during the tremors. 14S.N.P.I.T. & R.C.
  15. 15. Structural Codes Description Indian Standards IS: 456-2000 Code of Practice for Plain and Reinforced Concrete IS: 800-1984 Code of Practice for General Construction in Steel IS: 808-1989 Dimensions for hot rolled steel beams, columns, channels and angle sections IS:875-1987(Part-1) Code of Practice for Design Loads (Other than Earthquakes) for Buildings and Structures. Dead Loads — Unit Weights of Building Materials and Stored Materials IS:875-1987(Part-2) Code of Practice for Design Loads (Other than Earthquakes) for Buildings and Structures. Imposed Loads IS:875-1987(Part-3) Code of Practice for Design Loads (Other than Earthquakes) for Buildings and Structures. Wind Loads 15S.N.P.I.T. & R.C.
  16. 16. Codes Description Indian Standards IS:875-1987(Part-5) Code of Practice for Design Loads (Other than Earthquakes) for Buildings and Structures. Special Loads and Load Combinations IS:1786-1985 Specification for High Strength Deformed Steel Bars and Wires for Concrete Reinforcement. 16S.N.P.I.T. & R.C.
  17. 17. Design process: analysis, design and detailing:  Analysis: Structural analysis is necessary to determine the stress resultant like, 1. Shear stress 2. Bending moment 3. Axial force 4. Torsional moment Acting at various cross sections of structural elements. IS:456 permits the analysis of all structures by linear elastic theory. Code also permit use of approximate methods like substitute frame method, use of coefficients for the continuous beams and slabs. For the analysis of statically determinate beams and frames, conditions of static equllibrium 17S.N.P.I.T. & R.C.
  18. 18. Structural analysis: modelling 18S.N.P.I.T. & R.C.
  19. 19.  Design: A systematically planned structure: 1. Should satisfy the functional requirements of the client and should be asthetic, which needs an architect. 2. Should be structurally safe so as to withstand the loads it has to bear, which needs a structure engineer. The functional design of the building consists of planning the areas in best possible ways to obtain maximum usage and functions from the building. For a given residential bunglow, 19S.N.P.I.T. & R.C.
  20. 20. Functional planning 20S.N.P.I.T. & R.C.
  21. 21.  The structural design is concerned with the strength of the building and its components. The aim of structural design is to decide the size of the member and provide appropriate reinforcements so that the structures being designed will perform satisfactorily during their intended life.  With the appropriate degree of safety, the structure should: 1. Sustain all loads 2. Sustain the deformation during and after construction 3. Should have adequate durability 4. Should have adequate resistance to misuse and fire 21S.N.P.I.T. & R.C.
  22. 22. Structural planning 22S.N.P.I.T. & R.C.
  23. 23.  Detailing: On completion of the structural design, the design ideas normally need to be communicated for construction at the site by translating them into detailed structural and comprehensive. In fact, an elaborate analysis becomes worthless if the computations are not translated effectively into the structural drawings. Two main aims of RCC detailing are: 1. Providing an outline of the concrete to give necessary information regarding formwork to provide finished section of the desired size. 2. Providing enough reinforcement details for fabrication of the steel skeleton and its placement in the desired position. 23S.N.P.I.T. & R.C.
  24. 24. Detailing 24S.N.P.I.T. & R.C.
  25. 25. Limit state method  In this method of design, the structure shall be designed to withstand safety all loads liable to act on it throughout its life. It shall also safety the serviceability requirements, such as limitations on deflection and cracking.  The aim of design is to achieve acceptable probabilities that the structure will not become unfit for use for which it is intended, that is, that it will not reach a limit state.  All relevent limit state shall be considered in designed to ensure an adequate degree of safety and serviceability. In general, the structure shall be designed for the most critical limit state and shall be checked for the other limit states. 25S.N.P.I.T. & R.C.
  26. 26.  The limit state design philosophy, uses a multiple safety factor format, which attempts to provide adequate safety at ultimate loads as well as adequate serviceability at service loads, by considering all possible limit states.  For ensuring the above objectives, the design should be based on characteristics values for material strengths and applied loads, which takes into account the variation in the material strength and in the loads to be supported. 26S.N.P.I.T. & R.C.
  27. 27. 27 Serviceability Limit States: • Cracking • Excessive Deflection • Buckling • Stability Limit States S.N.P.I.T. & R.C.
  28. 28. Working stress method:  This is the traditional method of design, used not only reinforced concrete but also for structural steel and timber. This method of design was evolved around the year 1900. this method was accepted by many national codes. This method is based on linear elastic method.  This method ensures adequate safety by suitably restricting the stresses in the materials induced by the expected working loads on the structure.  In this method it is assumed that concrete and steel are elastic. At the worst combination of working loads, the stresses in materials are not exceeded beyond permissible values. 28S.N.P.I.T. & R.C.
  29. 29.  The permissible stresses are found out by using a suitable factor of safety to material strength, e.g. for concrete in compression due to bending, a factor of safety equal to 3.0 is considered on 28 days. Characteristic strength and factor of safety equal to 1.8 is considered on the yeild strength for mild steel reinforcement in tension due to bending.  Working stress method does not consider the mode of failure of the structure . Also, the reserve strength of materials beyond yield point is not considered in this method of design.  The WSM assumes strain compatibility, whereby the strain the reinforcing steel is assumed to be equal to that in the adjoining concrete to which it is bonded. 29S.N.P.I.T. & R.C.
  30. 30. Demerits of WSM:  The WSM does not show the real strength nor gives the true factor of safety the structure under failure.  Because of creep and non linear stress- strain relationship , concrete does not have definite modulus of elasticity.  It assumes stress-strain relationship for concrete is constant, which is not true  WSM does not consider the mode of failure of the structure i.e. ductile or brittle.  It give large sections of structural elements, thus uneconomical. 30S.N.P.I.T. & R.C.
  31. 31. Merits of WSM:  It is simple, both in concept as well as in application.  The design usually results in large sections of structural members, compared to LSM. Due to this, structures designed by WSM give better serviceability performance. i.e., less deflection, less crack width etc.  It is reasonably reliable. 31S.N.P.I.T. & R.C.
  32. 32. 32S.N.P.I.T. & R.C.