Comparison of the lateral deflection at midpoint of long & short side column

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Comparison of the lateral deflection at midpoint of long & short side column

  1. 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 106 COMPARISON OF THE LATERAL DEFLECTION AT MIDPOINT OF LONG & SHORT SIDE COLUMN UNDER BLAST LOADING 1 Prof.M.R.Wakchaure, 2 S.T.Borole 1, 2 Department of Civil Engineering Amrutvahini College of Engineering, Amrutnagar Tal-Sangamner, Dist-Ahmednagar (M.S.) India – 422608 ABSTRACT The study conducted on the behavior of structural concrete subjected to blast loads. An extensive parametric study was carried out on a series of 8 columns at long & short side to investigate the effect of transverse reinforcement, longitudinal reinforcement due to blast loading. Analysis of RC Column subjected to blast loading by using the finite element package ANSYS. The comparison between long side & short side column is made & further results are presented. In final result ratios of deformation of short to long side column are presented in this paper. Keywords: Column, Blast loading, structure, collapse, ANSYS I. INTRODUCTION The blast effects of an explosion are in the form of a shock wave composed of a high intensity shock front which expands outward from the surface of the explosive into the adjoining air. As the wave expands, it decays in strength, lengthens in duration and decreases in velocity. This phenomenon is caused by spherical divergence as well as by the fact that the chemical reaction is completed, except for some afterburning associated with the hot explosion products mixing with the surrounding atmosphere. Due to different accidental or intentional events, the behavior of structural components subjected to blast loading has been the subject of considerable research effort in recent years. Loss of life and injuries to occupants can result from many causes, including direct blast- effects, structural collapse, debris impact, fire, and smoke. To provide adequate protection against explosions, the design and construction of public buildings are receiving renewed attention of structural engineer’s .Use finite element programs such as ABAQUS, ANSYS, and ADINA etc. for analysis of RC Column subjected Blast Loading. INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), pp. 106-112 © IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2013): 5.3277 (Calculated by GISI) www.jifactor.com IJCIET © IAEME
  2. 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 107 II. METHODS FOR PREDICTING BLAST EFFECT The following methods are available for prediction of blast effects on RC building structures: Empirical (or analytical) methods Semi-empirical methods Numerical methods. Now described analytical procedures are presented in technical design manuals TM 5-1300 (US Department of the Army, 1990) this manual is one of the most widely used publications available to both military and civilian sectors for designing structures to provide protection against the blast effects of an explosion. It contains step-by-step analysis and design procedures, including information on (i) blast loading; (ii) principles of non-linear dynamic analysis; and (iii) reinforced concrete structural steel design. The design curves presented in the manual give the blast wave parameters as a function of scaled distance for three burst environments: (i) free air burst; (ii) air burst; and (iii) surface burst. A charge is located on or very near the ground surface, the blast environment is considered to be a surface burst. III. FINITE ELEMENT ANALYSIS FEM is useful for obtaining the load deflection behavior and its crack patterns in various loading. The FEA software should be selected based on the following considerations: 1. Analysis type to be performed. 2. Flexibility and accuracy of the tool. 3. Hardware configuration of your system FEA through ANSYS In ANSYS, the general process of finite element analysis is divided into three main phases, preprocessor, solution, and postprocessor. The finite element method has thus become a powerful computational tool, which allows complex analyses RC structures to be carried out in a routine fashion. 3.1 Element Type There are few assumptions that will be made with this model due to the SOLID65 concrete element capabilities. One assumption is that the base of the column will be fixed due to the rigid foundation on the existing column. This is a consequence of not having any concept of the placement, size, and number of reinforcing members of steel being used. The reason we cannot predict the longitudinal or transverse steel orientation is due to the smeared reinforcement associated with the SOLID65 element. 3.2 Modeling Properties The specimen will be modeled using the SOLID65 concrete element, which is used for modeling three dimensional solid models with or without rebar. The element is capable of cracking, crushing, plastic deformation, and creep in tension and compression using material properties. The material properties are as follows:
  3. 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 108 Table 1. Material Properties Fig. 1 Stress-Strain Graph 3.3 Column Geometry Using the finite element models discussed above extensive parametric study was carried out with the following cases considered for each columns for which the spacing of the transverse reinforcement is determined in accordance with the requirement in the IS 456-2000 code. Fig. 2 Column Geometry Structural Young's Modulus 2.e+005 MPa Poisson's Ratio 0.3 Density 7.85e-006 kg/mm³ Thermal Expansion 1.2e-005 1/°C Tensile Yield Strength 250. MPa Compressive Yield Strength 250. MPa Tensile Ultimate Strength 460. MPa Compressive Ultimate Strength 0. MPa Thermal Thermal Conductivity 6.05e-002 W/mm·°C Specific Heat 434. J/kg·°C Electromagnetics Relative Permeability 10000 Resistivity 1.7e-004 Ohm·mm
  4. 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 109 IV. BLAST LOADING A scaling chart that gives the positive phase blast wave parameters for a surface burst for hemispherical TNT (Trinitrotoluene) charge is presented in Figure 2-13. Such scaling charts provide blast load data at a distance R (called the standoff distance) along the ground from a specific explosive. The following step-by-step procedure for determining blast wave parameters for a surface blast is outlined in (Technical Manual) TM5-1300: Step 1. Determine the charge weight, W, as TNT equivalent, and ground distance RG from the charge to the surface of a structure. Step 2. Calculate scaled ground distance, ZG: ZG = RG / W1/3 Step 3. Read the blast wave parameters from Manual TM5-1300 on Page No. 2-13 & Clause No 2- 13-3 for corresponding scaled ground distance, ZG. To obtain the absolute values of the blast wave parameters, multiply the scaled values by a factor W1/3 Consider Third-storey building having height 12.5m is analyzed in this study. Standoff distance is considered as 6m, & Charge weight 500 kg which is the closest point to the building as shown in fig.4. An extensive parametric study was carried out on a series of 8 columns at long & short side to investigate the effect of transverse reinforcement, longitudinal reinforcement subjected by same blast load. Required: Free field blast wave parameters Pso, Pr, U, to, tA for a surface burst of W =500kg at a distance of Rh = 6m Table 2. Blast Load Parameter Sr.No Floor Col Col Size (mm) Pr (Mpa) Pso (Mpa) U (M/ms) to (ms) 1 Ground A-B 230x400 14.5 2.06 1.46 08.22 2 First C-D 230x400 8.27 1.31 1.16 16.44 3 Second E-F 230x350 4.31 0.91 0.97 19.73 4 Third G-H 230x300 2.06 0.48 0.85 20.83 Fig. 3 Blast loading of column A & B Fig. 4 Location of explosion on building 0 2 4 6 8 10 12 14 16 0 5 10 Pressure(Mpa) Time ( ms)
  5. 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 110 V. RESULT & DISCUSSION According to the results, the stand-off distance is the key parameter that determines the blast pressure so for protecting a structure is to keep the bomb as far away as possible by maximizing the stand-off distance. The results showed that if the member subjected to high pressure, they could cause big deformation on Long side Column as compare to short side of Column. 5.1 RC Column Responses to Blast Loading Fig. 5 Rebar structure of column Fig. 6 Meshing of column Fig. 7 Lateral Deflection of Long Side Fig. 8 Lateral Deflection of Short Side Column A Column A 0 10 20 30 40 50 60 70 0 5 10 Deformation(mm) Deformation 0 5 10 15 20 25 30 0 5 10 Deformation(mm) Time (ms) Deformation Fig. 9 Time Vs Deformation of Long & Short side column A
  6. 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 111 Table 3. Comparison of the lateral deflection at midpoint of Long & Short side columns 0 10 20 30 40 50 60 70 2 4 6 8 12 14.5 Deformation(mm) Pressure (Mpa) LA SA 0 10 20 30 40 50 60 70 2 4 6 8 10 12 14.5 Deformation(mm) Pressure (Mpa) LB SB Fig. 10. Lateral Deformation of Long & Short side Column A & B under pressure 0 10 20 30 40 50 60 70 2 4 6 8 12 14.5 Deformation(mm) Pressure (Mpa) LA LB 0 5 10 15 20 25 30 2 4 6 8 12 14.5 Deformation(mm Pressure (Mpa) SA SB Fig. 11. Comparison of Lateral Deformation of Long & Short side Column A& B Sr. No. Floor Element Deformation (mm) 1 GF LA 66.24 2 GF SA 24.89 3 GF LB 64.76 4 GF SB 23.55 5 FF LC 38.36 6 FF SC 14.37 7 FF LD 36.88 8 FF SD 13.22 9 SF LE 36.77 10 SF SE 11.32 11 SF LF 35.35 12 SF SF 10.28 13 TF LG 33.90 14 TF SG 08.72 15 TF LH 32.82 16 TF SH 07.92
  7. 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME 112 VI. CONCLUSION Based on the results of the parametric study, the main conclusions can be drawn, to know the procedure for calculating the blast loads on the RC structures. The comparison between the Long side columns and short side columns showed that the critical impulses for the long side column case are significantly higher. From result shows maximum lateral deformation ratios of short side to long side for the Column A, B, C, D, E, F, G, and H are 0.38, 0.36, 0.37, 0.36, 0.31, 0.29, 0.26, and 0.24 respectively. Under the blast loading, deformation of RC column A & B at long & short side is slightly changed. REFERENCES 1. IS 456:2000 Indian Standard Plain and Reinforced Concrete Code of Practice 2. Demeter G. Fertis (1973), “Dynamics and Vibration of Structures”, A Wiley-Interscience Publication, pp. 343-434. 3. Alexander M. Remennikov, “A review of methods for predicting bomb blast effects on buildings”, Journal of battlefield technology, vol 6, no 3. pp 155-161. (2003). 4. American Society for Civil Engineers, “Combination of Loads”, pp 239-244.7-02 (1997) 5. ANSYS Theory manual, version 5.6, 2000. 6. Biggs, J.M. “Introduction to Structural Dynamics”, McGraw-Hill, New York.(1964). 7. Dannis M. McCann, Steven J. Smith (2007), “Resistance Design of Reinforced Concrete Structures”, structure magazine, pp 22-27, April issue. 8. A.K. Pandey et al. “Non-linear response of reinforced concrete containment structure under blast loading” Nuclear Engineering and design 236, pp.993-1002. (2006). 9. D.L.Grote et al.(2001),“Dynamic behaviour of concrete at high strain rates and pressures”, Journal of Impact Engineering, Vol. 25, New York, pp.869-886. 10. A. Khadid et al. “Blast loaded stiffened plates” Journal of Engineering and Applied Sciences, Vol. 2(2) pp. 456-461. (2007). 11. J.M. Dewey (1971), “The Properties of Blast Waves Obtained from an analysis of the particle trajectories”, Proc. R. Soc. Lond. A.314, pp. 275-299. 12. J.M. Gere and S.P. Timoshenko (1997.), “Mechanics of materials”, 13. Xiaoli Bao, Bing Li.” Residual strength of blast damaged reinforced concrete columns.” 14. Mohammed S. Al-Ansari, “Building Response to Blast and Earthquake Loading”, International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012, pp. 327 - 346, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. 15. Dr. Salim T. Yousif, “New Model of Cfrp-Confined Circular Concrete Columns: Ann Approach”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 3, 2013, pp. 98 - 110, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. 16. H.Taibi Zinai, A. Plumier and D. Kerdal, “Computation of Buckling Strength of Reinforced Concrete Columns by the Transfer-Matrix Method”, International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 1, 2012, pp. 111 - 127, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.

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