ASPIRE TO EXCEL ABHYUDAY TITIKSH Dr. M.K. GUPTA A Project Presentation

ASPIRE TO EXCEL ABHYUDAY TITIKSH Dr. M.K. GUPTA A Project Presentation
A STUDY OF THE VARIOUS STRUCTURAL SYSTEMS SUBJECTED TO SEISMIC LOADS Submitted by: ABHYUDAY TITIKSH (Roll No.: ; Enrollment No.: AF8022) Under the guidance of : Dr. M.K. GUPTA Professor & Head, Department of Civil Engineering, Bhilai Institute of Technology, Durg ASPIRE TO EXCEL

A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta
ABSTRACT The objective of this study is to investigate the seismic behavior of the structure having various structural configurations like OMRCF (Ordinary Moment Resisting Concrete Frames), SMRCF (Special Moment Resisting Frames) and BSF (Braced Steel Frames). A comparative study of all the types of frames will shed light on the best suited frame to be adopted for seismic loads in Indian scenario. For this purpose, a G+4 building was designed for OMRCF, SMRCF and BSF framing configurations in Seismic Zone V according to Indian design codes. Tests were carried out to evaluate their structural efficiencies in terms of Storey Drifts, Base Shear, Amount of reinforcement and Average Displacements.

WHAT IS AN EARTHQUAKE? An earthquake (also known as a quake or tremor) is the result of a sudden release of large amount of energy in the Earth's crust that creates seismic waves. These waves manifest themselves by shaking and often displacement of the ground at the Earth's surface. The earthquake mainly occurs in Mantle part of Earth and most of them mainly occur by sudden slippage of fault. Alfred Wegener developed theory of Plate Tectonic Forces which clearly explains Earthquakes and their propagation.

SEISMIC ZONES IN INDIA The constantly varying geology at different locations in our country clearly implies that the likelihood of major earthquakes taking place at various locations is different. Thus a seismic zoning map was required to identify these regions. Based on the levels of intensities sustained during past major earthquakes, the zone map divided India into 5 zones in 1970. This was later revised in 2002 to 4 zones i.e. Zones II, III, IV & V. The areas under seismic zone I of the 1970 version of the zone map were merged with the areas under zone II in the 2002 version.

TYPES OF STRUCTURAL SYSTEMS
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta TYPES OF STRUCTURAL SYSTEMS A rigid frame in structural engineering is the load-resisting skeleton constructed with straight or curved members interconnected by mostly rigid connections which resist movements induced at the joints of members. Its members can take bending moment, shear, and axial loads. They are of two types: Rigid-framed Structures Braced-frames Structures.

The Rigid frame structures provide more stability. These structures resist the shear, moment and torsion more effectively than any other type of framed structures. In Braced frame structures, bracings are usually provided between beams and columns to increase their resistance against the lateral forces and sideways forces due to applied load. Bracing is usually done by placing the diagonal members between the beams and columns. This frame system provides more efficient resistance against the earthquake and wind forces.

Moment-resisting frames are rectilinear assemblages of beams and columns, with the beams rigidly connected to the columns. Resistance to lateral forces is provided primarily by rigid frame action-that is, by the development of bending moment and shear force in the frame members and joints.

AIMS OF THIS STUDY To model 3 structures for analyzing multistoried frames having OMRCF, SMRCF & BSF configurations. To carry out the analysis and design of the selected buildings in Seismic zone V. To make a comparative study of the storey drifts and Base shear for these frames. To provide structural engineers with a guideline on the economy aspect that could be obtained using Base Isolation.

Codes used for design are: RCC Design - IS 456:2000
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Codes used for design are: RCC Design - IS 456:2000 Steel Design - IS 800:2007 Loads for Steel Design - IS:875 (Part 1&2) Seismic Design - IS 1893:2000 (Part 1) Wind Loads – ASCE 7 The building frames are modeled in STAAD.Pro and the average displacement, beam stresses, slab stresses, storey drift and base shear are analyzed to give a comparative result in between the different framing systems.

COMPARASION OF MOMENT RESISTING FRAMES & BRACED FRAMES
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta COMPARASION OF MOMENT RESISTING FRAMES & BRACED FRAMES Moment frames are typically more expensive than braced frame systems, especially when they are designed for similar stiffness and serviceability. Cost is the main reason that most of the structural engineers tend to use moment frames as a last resort. Shear walls and brace frames tend to create barriers within structural floor plans, which are often acceptable for highly partitioned spaces. However, if open-space floor plans with minimal obstructions are needed, the beam-to-column connections in moment frames allow for wide-open spaces with no diagonal members or walls, making them worth the higher cost.

Moment-frame column and beam sizes can be significantly heavier per meter than in braced frames due to their means of transferring forces and resisting lateral drift. Heavier sections lead to higher overall material costs, and possibly the need for larger erection equipment. Moment frames can require more field-welding than braced frames, which leads to higher erection costs. A greater number of moment frames is often required over braced frames to provide enough stiffness in the building to accommodate drift requirements for serviceability. There are a limited number of prequalified connections allowed in mid/high-seismic regions, which can be more expensive than braced frame and low-seismic moment frame connections.

MODELING IN STAAD.Pro Three separate models were prepared in STAAD.Pro to check the behavior of the frames under the action of seismic forces. The first model was given OMRCF configuration, the second was given SMRCF configuration and the third was given BSF configuration.

The following assumptions were made before the start of the modeling procedure so as to maintain similar conditions for all the three models: Only the main block of the building is considered. The staircases are not considered in the design procedure. The building is to be used for exhibitions and so no interior walls are provided. Only external walls 230 mm thick with 12 mm plaster on each side are considered. At ground floor, slabs are not provided and the floor is resting directly on the ground.

CONCRETE MOMENT RESISTING FRAMES
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta The beams are resting centrally on the columns so as to avoid the conditions of eccentricity. For all structural elements, M30 & Fe500 are used. The footings are not designed. Supports are assigned in the form of fixed supports. Sizes of the members are as follows (All dimensions are in mm.) PROPERTY CONCRETE MOMENT RESISTING FRAMES BRACED STEEL FRAMES COLUMNS 500 x 500 ISWB 600 BEAMS 500 x 300 ISMB 500 SLABS 20 BRACES - ISMB 250

The buildings are to be designed for the following conditions:
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Seismic loads are considered in the horizontal direction only and the vertical direction are assumed to be insignificant. The buildings are to be designed for the following conditions: Live load = 4 KN/m2 (Typical floor); 1.5 KN/m2 (Roof) Dead load of walls on beams = 4.9 KN/m2 Location = Seismic Zone V (Not designed for Wind Loads as EQ loads are greater) Soil type = Soft; as per IS-1893(Part 1):2002 Floors = G+4 (Floor height = 4 m)

ANALYSIS & DESIGN OF THE MODELS
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta ANALYSIS & DESIGN OF THE MODELS The following load combinations are considered during the analysis of the model: 1.5 DL LL 1.2 DL LL EQX 1.2 DL LL EQZ 1.2 DL LL WLX 1.2 DL LL WLZ 1.2 DL LL EQX 1.2 DL LL EQZ 1.2 DL LL WLX 1.2 DL LL WLZ For asserting the simplest yet reliable method for analysis, the combined action of DL, LL & EQ forces are considered i.e. 1.2 DL LL EQX.

RESULTS & DISCUSSIONS The behavior of all the three framing systems is taken as a basic study on the modeled structure. The following parameters were considered to present a comparison between the different frames: Materials used Maximum Nodal Deflection Maximum Beam Shear & Moments Maximum Plate Stresses Storey Drift Average Storey Displacement

Materials used- Volume OMRCF SMRCF BSF Concrete (m3) 16.800 NIL Steel (kN) 8.312 9.821 Using the above data, it can be stated that the percentage of steel in concrete frames varies as follows: OMRCF = Taking as Base SMRCF = Increase of % In case of steel frames, the amount of concrete will be zero. However the weight of steel is very large as compared to concrete frames. This will lead to very high construction costs. But in long term, this high initial cost gets balanced as the salvage value of concrete frames is almost nil.

Maximum Nodal Deflection-
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Maximum Nodal Deflection- Deflection OMRCF SMRCF BSF Max. X (mm) 30.178 18.108 4.774 Min. X (mm) 0.000 Max. Y (mm) Min. Y (mm) -2.728 -2.450 -2.526 Max. Z (mm) 0.005 0.004 0.020 Min. Z (mm) -0.005 -0.004 -0.020 For the selected load case, the values of Nodal deflections are shown above. It can be seen clearly that Braced Steel Frames undergo minimum deflections.

Maximum Beam Shear & Moments-
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Maximum Beam Shear & Moments- Parameter OMRCF SMRCF BSF Max. Fx (kN) Min. Fx (kN) -4.586 -3.223 Max. Fy (kN) 98.410 67.184 54.708 Min. Fy (kN) Max. Fz (kN) 16.814 14.497 1.674 Min. Fz (kN) -1.674 Max. Mx (kNm) 1.394 1.020 0.011 Min. Mx (kNm) -1.394 -1.020 -0.011 Max. My (kNm) 33.960 29.090 3.376 Min. My (kNm) -3.376 Max. Mz (kNm) 48.226 Min. Mz (kNm)

For the selected load case, the axial forces in X and Y directions and Moments in Z-direction are the major terms to be considered. It is clear that because of higher resistance to deformation, the values of Fx, Fy and Mz are very low in case of Braced Steel Frames. SMRCF, although better than OMRCF, does not perform as well as the Steel frames.

Maximum Plate Stresses-
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Maximum Plate Stresses- The above figure shows the stress contours in the slabs for each of the frames. For the selected load case, maximum stresses are occurring near the ground floor in concrete frames. However in case of steel frames, these maximum stresses are seen at higher floors. The legends beside the figures (a), (b) and (c) show the values of stresses corresponding to the different colour codes.

Storey Drifts- Storey Height (m) OMRCF SMRCF BSF G 0.0000 1 4 0.4464 0.2678 0.0645 2 8 0.6372 0.3823 0.0939 3 12 0.6113 0.3668 0.0941 16 0.5022 0.3013 0.0818 5 20 0.3174 0.1905 0.0590 The storey drifts are zero for the ground and first floors. This is because the frames are assumed to be fixed at the base. However these values go on increasing as we increase the number of storeys. The maximum drift is seen in the case of OMRCF and the minimum is observed in case of Braced Steel frames. This is due to the presence of lateral braces in the steel frame which restrict the deformation of the structure.

Average Storey Displacement-
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Average Storey Displacement- Storey Height (m) OMRCF SMRCF BSF G 0.0000 1 4 0.4464 0.2678 0.0645 2 8 1.0836 0.6502 0.1584 3 12 1.6949 1.0170 0.2525 16 2.1972 1.3183 0.3343 5 20 2.5146 1.5088 0.3933 As we go on higher up the frame, the value of average displacement goes on increasing. But in case of steel frames, these values are very low. The maximum displacements are seen in the case of OMRCF. This means that under the action of selected load case, maximum deformation will be observed in the Ordinary Moment Resisting Frame.

SUMMARY & CONCLUSIONS It is clear to all that the seismic hazard has to be carefully evaluated before the construction of important and high-rise structures. The previous works done in this are mainly compared OMRCF and SMRCF, sometimes also involving shear walls in the design. But in this paper, the concrete MRF and braced steel frames both were compared side by side.

Based on the above analytical study carried out on 3 structures, the following deductions are made: BSF clearly provides more safety to the designers but it may prove to be extremely costly in some cases. In all the systems, the storey drift is within the permissible limits as per IS:1893 (Part 1). However SMRCF showed better results when compared to OMRCF. There is an increase of 18.5 % in the quantity of steel in case of SMRCF when compared to OMRCF. However this also results in a deduction of % in the amount of storey drift in SMRCF. Because of the presence of lateral braces, the stresses in columns are minimum in BSF.

The lateral loading is most effectively resisted in BSF. Thus the service life will be largest for this framing configuration. Due to the falling of the zone, the earthquake hazard will also increase. In such cases, BSF or SMRF with shear walls are applicable. Storey drifts are more in case of OMRCF & SMRCF. It is least in case of BSF. To further increase the effectiveness of the structure, earthquake resisting techniques such as shear wall & Base-Isolation can be used.

ROLE OF BASE ISOLATION IN REDUCING THE EFFECTS OF EARTHQUAKES
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta ROLE OF BASE ISOLATION IN REDUCING THE EFFECTS OF EARTHQUAKES Countries like US, New Zealand, Japan, China and European countries have adopted these techniques as their normal routine for many public buildings and residential buildings as well. In India, the use of base isolation techniques in public or residential buildings and structures is in its inception and except few buildings like hospital building at Bhuj, experimental building at IIT, Guwahati, the general structures are built without base isolation techniques. National level guidelines and codes are not available presently for the reference of engineers and builders.

Base Isolation - Video Demonstration

Advantages of Base Isolation:
A Study of the Various Structural Systems subjected to Seismic Loads – A. Titiksh, Dr. M.K. Gupta Advantages of Base Isolation: The isolated buildings will be safe even in strong earthquakes. The response of an isolated structure can be ½ to 1/8 of the traditional structure. Since the super structure will be subjected to lesser earthquake forces, the cost of isolated structure compared with the cost of traditional structure for the same earthquake conditions will be cheaper. The seismic isolation can be provided to new as well as existing structures. The buildings with provision of isolators can be planned as regular or irregular in their plan or elevations. Base Isolation also protects non-structural elements and instruments by lessening the entire structure’s speed during an earthquake, as opposed to toning alone.

SCOPE FOR FUTURE WORK As of now, the use of base isolation techniques is fairly new and the structural efficiency of Moment Resisting Frames can further be increased by using them along with Shear walls. National level guidelines can be prepared for selection of framing configuration in different Seismic Zones. The behavior of Base Isolated – Special Moment Resisting Frame – with Shear wall can then be analyzed and compared to Braced Steel Frame to obtain the optimum framing technique.

REFERENCES A Study Of The Various Structural Framing Systems Subjected To Seismic Loads A. Titiksh, Dr. M.K. Gupta, IJCE, ISSN: , Vol. 2, Issue 4, April 2015, pp A Comparative Study on Seismic Provisions made in Indian and International Building Codes for RC Buildings Seismic behaviors of columns in Ordinary and Intermediate Moment Resisting Concrete Frames S.W. Han, N.Y. Jee, Engineering Structures 27 (2005) pp. 951–962 Analysis and Design of R.C. Moment Resisting Frames with and without Shear Wall for Different Seismic Parameters A. Chippa, P. Nampalli, IJISET, Vol. 1 Issue 6, August 2014 A Comparative Study of OMRF & SMRF structural system for Tall & High Rise buildings subjected to Seismic Loads G.V.S. Sivaprasad, S. Adiseshu, IJRET, pISSN: , Vol. 2 Issue 9, September 2013 Comparative Study of SMRF building over OMRF building with Seismic and Wind effect Dr. Valsson Varghese, Y.R. Borkar, IJERA, ISSN: , Vol. 3 Issue 3, May-Jun 2013, pp

Seismic Design of Steel Special Moment Frames: A Guide for Practicing Engineers R.O. Hamburger, H. Krawinkler, J.O. Malley, S.M. Adan, NIST GCR ; National Institute of Standards & Technology, US Department of Commerce Design codes like IS : , IS : , IS : (Part-1), IS : , IS : 875 (Part-1&2), & ASCE 7. S.K. Duggal, Earthquake Resistant Design of Structures, (Oxford Press, 2007) Mario Paz , Dynamics of Structures: Theory & Computation (Kluwer Academic Publishers, 1997) P. Agarwal, M. Shrikhande, Earthquake Resistant Design of Structures, (PHI Learning Pvt. Ltd., 2006)

LIST OF PUBLICATIONS A. Titiksh & Dr. M.K. Gupta, “A Study Of The Various Structural Framing Systems Subjected To Seismic Loads” SSRG-IJCE International Journal of Civil Engineering; ISSN: ; Volume 2, Issue 4, April 2015; pp ) A. Titiksh & Dr. M.K. Gupta, “A Comparative Study Of The Various Structural Framing Systems Subjected To Seismic Loadings” IJETR International Journal of Engineering & Technical Research; ISSN: ; Volume 3, Issue 5, May 2015; pp ) Abhyuday Titiksh & M.K. Gupta, “A Study Of The Various Structural Framing Systems Subjected To Seismic Loads” (IREHM – International Journal of Earthquake Engineering & Hazard Mitigation (Tehran, Iran); ISSN: ; e-ISSN: ; Volume 3, No. 1, June 2015; pp ) Paper Accepted for Publication at IEIA Institution of Engineers India Springer Series-A, for June 2015 edition.

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ASPIRE TO EXCEL ABHYUDAY TITIKSH Dr. M.K. GUPTA A Project Presentation

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