Study of Seismic Effect on Re-entrant Corner Column
Investigating the Seismic Behavior of Structures with Irregular Plan
by Rohit Deshmukh*, Vaishnavi Vishnu Battul, Mithun Sawant, Tejashri Gulve,
- Published in Journal of Advances and Scholarly Researches in Allied Education, E-ISSN: 2230-7540
Volume 15, Issue No. 2, Apr 2018, Pages 299 - 304 (6)
Published by: Ignited Minds Journals
ABSTRACT
Irregularities in buildings are always expected due to many reasons like aesthetics, light, ventilation, etc. The irregularity is due to the reason the stiffness center and mass center of the building is not at the same location. Hence it is needed to study behavior of such structures during earthquake. The objective of this study is to understand plan irregularity and to analyze the seismic performance of the irregular frame using nonlinear static analysis in SAP2000. The study includes identification and measure of the irregularity level due to the irregular plan and improvement of the structural system considering seismic behavior.
KEYWORD
seismic effect, re-entrant corner column, irregularities, stiffness center, mass center, behavior, earthquake, nonlinear static analysis, SAP2000, plan irregularity
I. INTRODUCTION
Earthquake engineering deals with designing and constructing a structure such that during earthquake there is no damage to the structure. Seismic excitations diversely affect constructions. Seismic response of the structure depends on many parameters like structural configuration, quality of construction, soil condition, etc. It is observed that Structural and architectural configuration in plan and elevation are responsible for making the building irregular. Irregularities in buildings are always expected due to many reasons like aesthetics, light, ventilation, etc. A structure is identified as irregular from the geometrical positioning of the stiffness and mass center. Hence there is a need to estimate the seismic response of such structures and also quantify the eccentricity. Such an understanding on seismic response of irregular building would obviously help to modify the structural system at the design stage itself. With this as aim the paper tries to quantify the magnitude of irregularity and identifies the members that need to perform in the same way as that of performance of regular structure.
II. MODELLING AND ANALYSYS
To verify the validity of pushover analysis with the actual situation and for fixing the pushover parameters for proposed study, push over analysis has been carried on a structure which was tested and the results are reported in the literature (Ref.7 ). As explained in the paper, a three storied 2x2 bay structure is modelled and analysed in the SAP2000 software. Plan and elevation reinforcement detailing for the structure are shown in fig 1 to 3 respectively.
Figure 1: Plan
Figure 2: Elevation
Figure 3: Reinforcement Detailing
Result is obtained after doing pushover analysis, It is found that they are identical this can be seen from fig. 4 and 5.
Figure 4: Pushover curve in SAP2000
Figure 5: Comparison of Experimental results with Analysis
Based on this study material parameters and the procedure are finalised for beam and column model withM3 hinge. respectively. It is a five storied residential building located in zone V area. The soil is hard. For comparison, a regular building is considered, its plan and 3D view is as shown in fig. 8 and 9.
Figure 6: Plan of Proposed Irregular Structure
Figure 7: 3D view of Proposed Irregular Structure in SAP2000
Figure 8: Plan of Proposed Regular Structure
Mr. Shrikant R. Kate1* Miss. Prajkta B. Jamale2
Figure 9: 3D view of Proposed Regular Structure in SAP2000
The analysis and design of the structure is done in STAAD Pro. Detailing of beam and columns are done as per the provision given in IS456:2000 and IS13920:1993. They are computed and given in Table 1 and Table 2 respectively
Table 1: Geometrical details of the structural members of the proposed structures with IS456:2000 Table 2: Geometrical details of the structural members of the proposed structures with IS13920:1993
With the help of design and detailing obtained from STAAD Pro., the proposed structure is modelled in SAP2000. All the properties has been assigned and analysed. Pushover analysis is done on all the models in X and Y directions i.e. Irregular and Regular Structures with consideration of IS456 and IS13920, using SAP2000. Results are obtained after pushover analysis. Comparison of base shear and roof displacement are given in Fig 10 to 13. Table 3 gives the base shear and roof displacement for the different models analysed.
Figure 10: Pushover curves for IS456 in X Direction
Figure 11: Pushover curves for IS456 in Y Direction
Figure 12: Pushover curves for IS13920 in X Direction
Figure 13: Pushover curves for IS13920 in Y Direction Table 3 : Base Shear and Roof Displacement for global structure
Base Shear and Roof displacement at the performance point are given in Table 4. Comparison irregular and regular frame is done with respect to same.
Table 4: Comparison of Shear Force and Displacement at Performance Point
Bending moment of the re-entrant column is checked for all frames at the performance level i.e bending moment demand and moment of resistance i.e bending moment capacity of the same column is calculated manually using SP16. Bending moments are tabulated in Table 5.
From Table 5, it is observed that the bending moment demand is more than the capacity for both the irregular structures i.e IS456 and IS13920 when pushover analysis is done in X Direction. Though the demand and capacity is matching for global structure as shown in figure 14 and 15, we need to take due care while designing re-entrant corner columns, as moment at the re-entrant corner columns is more than the capacity of the column. It can be seen from Table 5.
Figure14 : Capacity Spectrum for Pushover analysis of Irregular 456 in X Direction
Figure15 : Capacity Spectrum for Pushover analysis of Irregular 13920 in X Direction
Mr. Shrikant R. Kate1* Miss. Prajkta B. Jamale2
the re-entrant corner colums are modified. The modified details of column are given in Table 6.
Table 6: Geometrical details of the modified structural members of the proposed structures
Again pushover analysis is done on both the modified structures. The bending moment demand and capacity is given in Table 7.
Table 7: Comparison of Bending Moment of Modified Structures with respect to demand and capacity at Performance Point
Comparison of base shear and roof displacement of original and modified structure are given from fig 10 to 13
Figure 10: Pushover curves for IS456 in X Direction
Figure 10: Pushover curves for IS13920 in X Direction
Irregularity Level is calculated as response of regular structure to the irregular structure and is given in Table 8
Table 6: Irregularity Level at Performance Point
IV. CONCLUSION
Irregularity in plan is unavoidable. It is because of many reasons like requirement of client, functional requirements, etc. Due care is needed while designing such structures. It is observed from above study that for re-entrant corner columns need more attention than the other columns. These columns should be designed properly. ● After proper modifications the bending moment capacity of re-entrant corner column is increased by 1.5 and twice in case of IS456 and IS13920 respectively. ● Base Shear for regular Structures is more than that of irregular structures. ● Base shear for modified structures is more than the original structures. ● Irregularity level is almost about 25% for both the irregular structures.
ACKNOWLEDGMENT
We acknowledge the support of Dr. A. V. Patil, Principal, DYPIEMR, Akurdi, Pune, Ms. Amruta
REFERENCES
Andrea Lucchini, Giorgio Monti, Enrico Spacone (2005). "Asymmetric-Plan Buildings: Irregularity Levels And Nonlinear Seismic Response", ―Dipartimento di Protezione Civile – Consorzio Reluis‖, signed on 2005-07-11 (n. 540). Dr. S.K. Dubey & P.D. Sangamnerkar (2011). "Seismic Behaviour of Asymmetric RC Buildings", International Journal of Advanced Engineering Technology E-ISSN 0976-3945, IJAET/Vol.II/ Issue IV/October-December, 2011/296-301. IS: 1893 (Part 1) : 2002- Criteria for Earthquake Resistant Design of Structures.
IS13920:1993-Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces IS456:2000- Plain and Reinforced Concrete-Code for Practice.
Magliulo G., Maddaloni G. and Petrone C. (2014). "Influence of earthquake direction on the seismic response of irregular plan RC frame buildings", Earthq Eng & Eng Vib (2014) 13: 243-256 DOI: 10.1007/s11803-014-0227-z. N. Lakshmanan, K. Muthumani, G.V. Rama Rao, N. Gopalkrishnan and G. R. Reddy (2007). "Verification of Pushover Analysis Method With Static Load Testing", International Workshop on Earthquake Hazzards and Mitigation, Guwahati, India, 7-8 December 2007. Neha P. Modakwar, Sanita S. Meshram, Dinesh W.Gawatre, "Seismic Analysis of Structures with irregularities", IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684, p-ISSN: 2320-334X, pp. 63-66 R. I. Herrera, J. C. Vielma, R. Ugel, A. Alfaro, A. Barbat & L. Pujades (2013). "Seismic response and torsional effects of RC structure with irregular plant and variations in diaphragms, designed with Venezuelan codes", WIT Transactions on The Built Environment, Vol 132, © 2013 WIT Press., ISSN 1743-3509 (on-line) Earthquake Engineering October 12-17, Beijing, China.
Corresponding Author Rohit Deshmukh*
Asst. Prof. D.Y. Patil Institute of Engineering, Management and research, Akurdi, Pune
E-Mail – rohit16007@gmail.com
