Performance of Short-Leg Shear Wall and Bare Frames in Irregular RC Structures
1 like67 views
This document presents the results of a study that used pushover analysis in ETABS to examine the structural performance of irregular RC structures with and without short-leg shear walls. Models of step-shaped, U-shaped, L-shaped, and T-shaped plans were analyzed, with and without short-leg shear walls included. The analysis found that inclusion of short-leg shear walls improved structural performance by increasing the base shear capacity and roof displacement at maximum base shear. Asymmetry in building elevation also decreased structural performance for bare frame models compared to symmetric models. Inclusion of short-leg shear walls was shown to improve performance of irregular structures.
Performance of Short-Leg Shear Wall and Bare Frames in Irregular RC Structures
- 1. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 12 | Dec-2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 666 PERFORMANCE OF SHORT-LEG SHEAR WALL AND BARE FRAMES IN IRREGULAR RC STRUCTURES Harshith Akash K1, M R Suresh2 1Post Graduate student in Structural Engineering, DR. AIT, Bengaluru, 560056, Karnataka, India 2 Associate Professor, Dept. of Civil Engineering, DR. AIT, Bengaluru, 560056, Karnataka, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract – Pushover analysis in ETABS is considered to examine the structural performance.Theperformanceofthese structures depends on their location, construction expertise and building geometry. Especially in seismic-prone areas it’s recommended to enhance structural ductility to prevent early failure. The performance variation can be seen when use of short-leg shear wall is incorporated in the design. Pushover curves, and graphical representation of the results are shown. 1. INTRODUCTION Asthe need for shelter arisesmore, the adequatenessofland would remain dismal, in such cases demand for high- rise/mid-rise buildings increases rapidly, in order to take care of this problem. The provision of short-leg shear wall in irregular buildings enhances the structural performance. Non-linear methods are to be used to understand their behavior because they give the exact picture both in elastic and plastic states. The analysis is done for Type-ii soil. 2. ETABS Modeling for asymmetrical plans No. of stories in all the models =10 Story height --3.2m Beam and column: 300 mm x 600 mm & 500 mm square column Coupling beam: 200 mm x 750 mm Slab thickness: 150 mm Wall thickness: 230 mm Shear wall depth: 200 mm 2.1 SOIL AND MATERIAL PROPERTIES: Grade of Concrete: M40 – for Beams, Walls and Columns M25 – for Roof Slabs Grade of Reinforcing Steel: Fe–500-forBeams,Walls and Columns Fe–415- for Roof Slabs Soil type: Type-ii medium-stiff Zone-iv 2.2 Geometry and Loads Initial grid size: 25 m x 25 m Bay width in both directions: 5 m Table -1: Loads Floor finishes 1 kN/m2 Imposed Load on all Floors 3.5 kN/m2 Imposed Load on Roof Slab 1.5 kN/m2 Partition Load on Beams 13 kN/m Parapet Wall Load 7 kN/m Seismic Zone and Zone factor Z-iv, Z=0.24 Importance and Response Reduction Factor (I and R) 1 and 5 The models are shown below and pushover analysis is done subsequently for the models. The planof buildingsistakenas step-shaped for Model-9, U-shaped for Model-10Y, L-shaped for Model-11, T-shaped for Model-12Y. Then, for the same models short-leg shear walls are provided at the corners: Model-9S, Model-10YS, Model-11S, and Model-12YS. It’s difficult to analyze the performance in linear methods hence non-linear methods are recommended for the design. Model 9 Model 10Y
- 2. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 12 | Dec-2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 667 Model 9S Model 10YS Model 11 Model 12Y Model 11S Model 12YS 3. Modeling for elevation (symmetrical and asymmetrical) Here, the models for both symmetry and asymmetry are considered for the design for the same building details as mentioned earlier.
- 3. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 12 | Dec-2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 668 Fig1: Plan, elevation and isometric view of Model-1 The same type of change in plan takes place for thefollowing models. a. (1-4 stories) b. (5-7 stories) c. (8-10 stories) Fig 2: Plan for same above stories (a,b and c), elevation and isometric view of Model-13
- 4. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 12 | Dec-2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 669 Fig 3: Plan for same above stories, elevation and isometric view of Model-14 Fig 4: Plan for same above stories, elevation and isometric view of Model-15
- 5. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 12 | Dec-2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 670 Fig 5: Plan for same above stories, elevation and isometric view of Model-16 Results and Conclusions The pushover analysis wascarried out for the abovemodels, following shows the variation of performance when short- leg shear wall is used in the design. Pushover curves without SLSW Pushover curve for models with SLSW The roof displacement corresponding to maximum base shear is highest for model 10y-S. The pushover curves of models 10Y and 12y-S show highest strength before reaching collapse. Pushover curves for bare frames The roof displacement corresponding to maximum base shear is highest for model 16 and least for model 16 among elevation asymmetric models. The roof displacement corresponding to maximum base shear of all elevation asymmetric models is greater than the symmetric model. Base shear vs roof displacement for bare frame models
- 6. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 12 | Dec-2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 671 The base shears obtained at performance point is maximum for model 16 and minimum formodel 1 among the RC frame models with elevation asymmetry. Also, the base shears at performance point of all the elevation asymmetric models are greater than the symmetric model. REFERENCE 1. Ashraf, H. and Stephen, P., (1998), “Practical Three- Dimensional Nonlinear Static Pushover Analysis”, Structural Magazine, Winter Edition. 2. Dai, K. (2013), “Breakthrough of Traditional Shear Wall Structure System-Short Leg Wall Structure System”, Journal of the Structural Design of Tall and Special Buildings, Vol.2, No.2, pp 1270-1278 3. D’Ayala, D., Meslem, A., Vamvatsikos, D., Porter, K., Rosetto, T., Crowley, H., and Silva, V. (2014), “Guidelines for Analytical Vulnerability forAssessment of low/mid rise buildings: Methodology”, Report published in context of the Vulnerability Global Contract Project, WWW.nexus.globalquakemodel.org 4. Nikhil, A., Kulkarni, P.B., Pooja, R. (2013)