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Analysis of Confined Masonry part 1
 

Analysis of Confined Masonry part 1

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    Analysis of Confined Masonry part 1 Analysis of Confined Masonry part 1 Presentation Transcript

    • Short Course on Seismic Design of Reinforced and Confined Masonry Buildings February 17-21, 2014, IIT Gandhinagar, India
    • Acknowledgments Kiran Rangwani, IIT Gandhinagar, India EERI Confined Masonry Network – authors of the confined masonry guide: Roberto Meli and others
    • Topics Part 1: Simplified Method (Svetlana Brzev) Part 2: Wide Column Model (J.J. Perez Gavilan)
    • The Simplified Method (SM) Based on an idealized distribution of lateral seismic forces in regular shear wall structures with rigid diaphragms. Shear strength of all walls at any floor level is required to exceed the seismic demand (applied shear force due to earthquake ground shaking)
    • Assumptions 1.It is assumed that all walls at each floor level fail simultaneously. 2.The walls have shear-dominant behaviour (the effect of bending is ignored). 3.The method assumes rigid diaphragm behaviour. 4.The method ignores torsional effects.
    • Theoretical Background The goal: Shear strength of all walls at any floor level (VR ) should exceed the seismic shear force demand (Vx) at the same level
    • Seismic Shear Force Demand Interstorey shear force Vx  ix QV
    • Seismic Force Distribution to Individual Walls Wall shear demand Vjx
    • Seismic Force Distribution to Individual Walls xN j jx jx xjxjx V k k DkV   1 j jAEj jx H AFG k      N j jAEj jAE xjx AF AF VV j 1
    • Wall resistance VRj Storey Shear Resistance Seismic load Ap Aw Wall cross-section Aj
    • Storey Shear Resistance 1AEF when 33.1 L H 2 33.1        H L FAE when 33.1 L H AEjsRj FAfV 
    • Wall Density Index (d) One of the key indicators of seismic resistance p w A A d  Seismic load Ap Aw
    • Wall Density Index Derivations Goal: resistance greater than demand ws N j jsR AfAfV  1 ThB WAV  pT nwAW  s h f wnA d   BR VV 
    • Wall Density Index – India Allowable shear stress (N/mm2) Floor weight (kN/m2) Number of storeys Seismic Zone III IV V 0.3 6.0 1 1.6 2.4 3.6 2 3.2 4.8 7.2 3 4.8 7.2 10.8 0.4 1 1.2 1.8 2.7 2 2.4 3.6 5.4 3 3.6 5.4 8.1 0.5 1 1.0 1.5 2.2 2 2.0 2.9 4.4 3 2.9 4.4 6.5 0.3 8.0 1 2.2 3.2 4.8 2 4.3 6.4 9.6 3 6.5 9.6 14.4 0.4 1 1.6 2.4 3.6 2 3.2 4.8 7.2 3 4.8 7.2 10.8 0.5 1 1.3 2.0 2.9 2 2.6 3.9 5.8 3 3.9 5.8 8.7
    • Assumptions 1. 𝑅=2.5 for confined masonry (currently not addressed by IS 1893) 2. 𝑆𝑎 𝑔 = 2.5 assuming the fundamental period range from 0.1 to 0.4 sec 3. Importance factor 𝐼=1 assuming regular importance 4. Allowable masonry shear stress (fs): from 0.3 to 0.5 N/mm2 5. Floor weight (w) – two values: 6.0 kN/m2 (light-weight floor structure) and 8.0 kN/m2 (heavy-weight floor structure e.g. RC slab).
    • Further Reading  Attached writeup (document) on the Simplified Method  Seismic Design Guide for Low-Rise Confined Masonry Buildings, EERI, 2011 www.confinedmasonry.org