GRD Journals- Global Research and Development Journal for Engineering | Volume 6 | Issue 6 | May 2021 ISSN- 2455-5703
Review on Performance of RCC Frame Structure under Blast Explosion Dixit K. Patel PG Student Department of Civil Engineering Sankalchand Patel College of Engineering, Visnagar-384315, Mehsana, Gujarat, India
Dhruvkumar H. Patel Assistant Professor Department of Civil Engineering Sankalchand Patel College of Engineering, Visnagar-384315, Mehsana, Gujarat, India
Abstract In present day days numerous regular citizen structures need safeguarding against impact impacts. Past occurrences of fear based oppressor exercises have expanded the mindfulness towards the foundational layout to relieve the impact of blast and counteraction of breakdown of the structure. The impact issue is somewhat new data about the improvement in this field is made accessible generally through distribution of the Army Corps of Engineers, Department of Defense, and other administrative office and public organizations. Because of various unplanned or purposeful occasions, the conduct of underlying parts exposed to impact stacking has been the subject of extensive exploration exertion as of late. The target of impact safe plan is to forestall the breakdown of the primary framework and to keep up underlying honesty through malleable and excess conduct. The aim of present work is to study the effects on building due to blast and to study progressive collapse potential of reinforced concrete building designed for gravity loading only and building designed for seismic loading. Present study includes the structural and non-structural aspects for blast resistant building. Depending on building dimensions and blast load parameters, blast pressure on each face of the rectangular building is calculated. Blast load parameters includes scaled distance, peak overpressure, peak reflected pressure, and positive phase duration. The comparison of blast overpressure suggested by different authors is presented. The calculation of blast load on the faces of the building, as per IS 4991-1968 criteria for blast resistant structures for explosion above ground is included is this work. Keywords- Blast Loading, Collapse, Gravity Loading, Overpressure, Explosion
I. INTRODUCTION The impact can by and large order as outside and interior impact. Outer impact can additionally recognized as surface burst or air burst. A blast which is situated a good ways off from or more the design is known as air burst blast, while surface impact will happen when explosion is found near or on the ground. An interior or kept blast will deliver stun loads or, gas pressure loads from the containments of the results of the blast. This pressing factor has a long span in contrast with that of the stun pressure, because of outer explosion. Due to exceptionally vulnerability in anticipating impact loads, it is hard to develop impact evidence building [10].However, different primary and nonunderlying safety measures can be taken to limit primary harm and physical injuries. A. Blast Load and Blast Phenomena When all is said in done, a blast is the aftereffect of a speedy arrival of a lot of energy in a restricted space. Blasts can be grouped by their inclination as physical, atomic and synthetic occasions [2]. If there should be an occurrence of an actual blast: - The energy can be delivered by the calamitous disappointment of a packed gas chamber, the volcanic ejection or even the blending of two fluids at various temperatures. In atomic blast: - The energy is delivered from the arrangement of various nuclear cores by the reallocation of protons and neutrons in the cores acting inside. In substance blast: - The quick oxidation of fuel components (carbon molecules and hydrogen) is the fundamental wellspring of energy. The sort of burst for the most part delegated, 1) Air burst 2) High height burst 3) Submerged burst 4) Underground burst 5) Surface burst The conversation in this segment is restricted to air burst or surface burst. This data is then used to decide the powerful loads on surface constructions that are exposed to such impact pressures and to plan them as needs be. It ought to be brought up that surface
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
construction can't be shielded from an immediate hit by an atomic bomb it can notwithstanding, be intended to oppose the impact pressures when it is situated at some separation from the place of burst [11]. The front of the blast waves weakens as it progresses outward, and its velocity drops towards the velocity of the sound in the undisturbed atmosphere [4]. Another quantity of the equivalent importance is the force that is developed from the strong winds accompanying the blast wave known as the dynamic pressure; this is proportional to the square of the wind velocity, u and the density of the air behind the shock front, ρ:
Fig. 1: Variation of blast pressure with distance
B. Blast Force-Time History The power for the accepted charge weight and scaled distance is determined physically by utilizing IS:4991-1968 and the variety of power for various time stretches is additionally determined physically for each shaft segment joint[3]. Time history loads created because of impact loads have extreme focus at first and continuously diminishing to focus in exceptionally little time span, use of impact load is like breeze load application on structure however the thing that matters is impact is motivation load which goes on for brief timeframe say not many milli second's.
II. METHODOLOGY This nonlinear powers removal, speed increase, speed trademark in singular casing components demonstrated in a SAP2000 programming. Impact wave relies on two elements blast size and weight of TNT and the stalemate distance between where the impact is happening at ground surface. Consider the structure will be influenced on the shoot loads by some weight (kg) of TNT at a specific stalemate distance. For dynamic investigation of construction, the impact load impact will be founded on stacking and time history that is applying to the design individuals as diminutive term stacking (transient stacking). The pack size, complete spear on each joint, terms are in the middle of pressing factor time history computations will be taken Table-1 given IS 4991-1968. The technique used to compute impact presser on front face of every single joint as a network plan. In a front face of building every single pillar – section joint is differing three-sided powers are acting. The maximum values of the positive side-on overpressure, reflected over pressure and dynamic pressure as caused by considering the explosion of one tonne TNT at various distances from the point of explosion, are given in tabular form in IS 49911968. The duration of the positive phase of the blast, and the equivalent time duration of positive phase are also given in the table of the code as per IS:4991-1968[8]. Ps= Pso (1-(t/t0)) e-t/to q = qo(1-(t/to)) e-2t/to Where, P is side-on over pressure Ps is peak side-on over pressure. to is time for positive phase of side on over pressure t is time at present q is dynamic pressure.
III. ANALYSIS AND MODELING G+9 structure displayed examined exposed to shoot heap of a blast 100kg TNT utilizing SAP2000. Impact load characterized as presser-time three-sided work in this model. To discover the impact boundaries stalemate distance is vital. Shoot highlight structure distance builds pressing factor will be diminishes in view of pressing factor diminishes expanding of stalemate distance [9]. A. Model of Building The RCC framed structure is designed in the software tool and the Structure material properties can be observed in Table-1. The description of member and load specifications are follow (see below).
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
Table 1: Concrete and steel bar properties as per IS 456 Properties Concrete Properties Steel Bar Properties 3 3 Unit weight (γ) 25 (kN/m ) 76.9729 (kN/m ) 5 Modulus of elasticity (E) 22360.68 (MPa) 2x 10 (MPa) Poisson ratio (ν) 0.2 0.3 -6 -6 Thermal coefficient (α) 5.5x10 1.170 x10 Shear modulus (G) 9316.95 (MPa) 76923.08 (MPa) Damping ratio (Ϛ) 5 (%) Compressive strength (Fc) 30 (MPa) Yield strength (Fy) 415 (MPa) Tensile strength (Fu) 485 (MPa) Table 2: Member and load specifications Column 0.300m x 0.750m Beams 0.300m x 0.450m Slab 120 mm 4 KN/m2 for slab Dead load 9.38 KN/m2 for outer walls ( IS 875-Part 1 ) 4.27 KN/m2 for inner walls 2 KN/m2 for slab Live loads 3 KN/m2 for corridors ( IS 875-Part 2 ) 1.5 KN/m2 for top slab Blast load calculated manually (as per IS:4991-1968 and given in Table) Combination load 1.5(Dead load +Live load) 1.2 (Dead load+ Live load) Materials used M30, Fe415
B. Structural Modeling The building for the present study is G+9 building consisting of 3 bays in X- direction and an overall span of 9m and 3 bays in Ydirection up to 12m. The typical storey height is 3 meters and overall height of the building is 30m from the ground level. In this study aimed the comparison the different structural building under the blast load [9]. So, we consider, 1) Simple RCC frame structure 2) RCC frame structure with shear wall 3) RCC frame structure with x- bracing.
Fig. 2: Simple RCC frame structure
Shear wall system is one of the most commonly used lateral-load resisting technique for high-rise buildings. Shear walls have very high in-plane strength and stiffness, which can be used simultaneously for resisting large horizontal and gravity loads. In tall buildings, it is very important to ensure adequate lateral stiffness to resist lateral load [13].
Fig. 3: RCC frame structure with shear wall
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
In this study cross bracing (X-bracing) has been used in RCC bare frame structure and modal have been generated in SAP-2000. Cross Bracing is a framework used to built up building structures in which slanting backings meet. Cross propping is normally seen with two slanting backings put in a X-molded way. Under parallel power (like breeze or seismic movement) one support will be under pressure while the other is being packed.
Fig. 4: RCC frame structure with X-bracing
C. Applying Blast Load on Structure The following models of different structure blast load applied and models created by SAP2000.
Fig. 5: Blast load applied on simple RCC frame structure
Fig. 6: Blast load applied on RCC frame structure with shear wall
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
Fig. 7: Blast load applied on RCC frame structure with X-bracing
IV. ANALYSIS OF RESULTS The blast load applied on the different RCC frame structure the results of different TNT at different distance like as 20m, 30m, 40m are shown in graph as follows:
Fig.8: Storey drifts for structure with bare frame, bracing & shear wall (0.1T_20m)
Fig. 9: Storey drifts for structure with bare frame, bracing & shear wall (0.2T_20m)
Fig. 10: Storey drifts for structure with bare frame, bracing & shear wall (0.3T_20m)
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
Fig.11: Storey drifts for structure with bare frame, bracing & shear wall (0.1T_30m)
Fig. 12: Storey drifts for structure with bare frame, bracing & shear wall (0.2T_30m)
Fig.13: Storey drifts for structure with bare frame, bracing & shear wall (0.3T_30m)
Fig.14: Storey drifts for structure with bare frame, bracing & shear wall (0.1T_40m)
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
Fig. 15: Storey drifts for structure with bare frame, bracing & shear wall (0.2T_40m)
Fig. 16: Storey drifts for structure with bare frame, bracing & shear wall (0.3T_40m)
V. CONCLUSIONS The Present study of this paper a 10 Storey RCC building is analyzed for blast load for 100kg TNT placed at a distance of 30m from the point of explosion. Blast load in each point was calculated from IS 4991-1968 and nonlinear time history is carried out of finite element analysis software SAP2000. There are following conclusion were drawn. – For 0.1T at 20m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 40.15% & 59.36% respectively compare to structure with bare frame. – For 0.2T at 20m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 53.67% & 64.67% respectively compare to structure with bare frame. – For 0.3T at 20m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 53.13% & 64.93% respectively compare to structure with bare frame. – For 0.1T at 30m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 51.07% & 61.93% respectively compare to structure with bare frame. – For 0.2T at 30m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 47.47% & 63.29% respectively compare to structure with bare frame. – For 0.3T at 30m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 51.46% & 62.38% respectively compare to structure with bare frame. – For 0.1T at 40m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 51.57% & 60.91% respectively compare to structure with bare frame. – For 0.2T at 40m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 55.34% & 65.08% respectively compare to structure with bare frame. – For 0.3T at 40m away from building, the storey drift of Structure with bracing & with shear wall at 10th floor is decrease by 50.78% & 61.55% respectively compare to structure with bare frame. – The Structure with bare frame, with bracing & with shear wall, axial force is decrease for increase in blast explosion from 0.1T to 0.2T & 0.1T to 0.3T at 20m, 30m & 40m away from building. – The Structure with bare frame, with bracing & with shear wall, bending moment is decrease for increase in blast explosion from 0.1T to 0.2T & 0.1T to 0.3T at 20m, 30m & 40m away from building. – The Structure with bare frame, with bracing & with shear wall, shear force is decrease for increase in blast explosion from 0.1T to 0.2T & 0.1T to 0.3T at 20m, 30m & 40m away from building.
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Review on Performance of RCC Frame Structure under Blast Explosion (GRDJE/ Volume 6 / Issue 6 / 005)
ACKNOWLEDGMENT This research paper is made possible through the help and support from everyone, including: parents, professors, family, friends, and in essence, all sentient beings. I would like to express my deep gratitude to Mr. Dhruvkumar H. Patel, my research supervisors, for their patient guidance, enthusiastic encouragement and useful critiques of this research work. He kindly read my paper and offered invaluable detailed advices on grammar, organization, and the theme of the paper. For his inspiring and encouraging attitude. Initially working out to this would have been a very tedious job if proper support was not presented from his side. I would also like to thank Dr. Abhijitsinh Parmar who provides me ancillary guideline to achieve desired goal. The concerning paper is only used for educational research and development purpose that is not tested for industrial protocols. Finally, I offer my deep gratitude to my parents who have appreciated, encouraged and assisted in our endeavor.
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