Modelling for Seismic Analysis of RC Frame Buildings with Infill Wall and Special Shear Wall Kaustubh Dasgupta Department of Civil Engineering Indian Institute of Technology Guwahati
Seismic behaviour Outline RC frame building Structural walls (shear walls) Analysis aspects Modelling Frame building components Special shear wall Current concern
Seismic Behaviour
Seismic Behaviour RC Frame Buildings with Masonry Infill Walls
Open Ground Storey Building Configuration (Murty, 2001)
Open Ground Storey Building Inverted pendulum type behaviour (Murty, 2002)
Seismic Damage Crushing of column (Murty, 2001)
Seismic Damage Collapse of ground storey (Murty, 2001)
Seismic Damage Poor reinforcement detailing (Murty, 2001)
Open Intermediate Storey Configuration (Kaushik, 2006)
Seismic Behaviour RC Frame Buildings with Structural Walls
Column Structural Walls Also called Special Shear Walls Principal attributes Large Lateral Strength High Stiffness Ductility Slab Beam Foundation RC Shear Wall (Murty, 2002)
Failure Modes: Slender Walls Flexure-Shear (Hines and Seible, 2004) Web Crushing Failure
Failure Modes Flexural-Compression 1986 San Salvador earthquake (EERI, 1987)
Failure Modes Flexural Compression Boundary element reinforcement Fracture and buckling of vertical reinforcement 2010 Chile earthquake (Massone et al., 2012)
Failure Modes Diagonal Tension 2001 Bhuj earthquake (EERI, 2002)
Failure Modes Diagonal Compression 2002 Molise earthquake (EERI, 2004)
Failure Modes Rocking Local soil failure 1994 Northridge earthquake (EERI, 1996)
Failure Modes Out-of-Plane Instability Steel Crack Crack Tension Compression Experimental Observation (Paulay and Goodsir, 1985)
Failure Modes Out-of-Plane Instability Also due to local crushing at multiple locations 2010 Chile earthquake (Massone et al., 2012)
Failure Modes: Squat Walls Shear Cracking 2010 Chile earthquake (Verisk Analytics webpage, 05 Feb 2018)
Failure Modes Sliding 1985 Chile earthquake (EERI, 1986)
Failure Modes Diagonal Compression Desirable Modes of Failure - Yielding of vertical steel?? - Yielding of horizontal steel?? Diagonal Tension
Failure Modes Squat bridge pier 1995 Kobe earthquake (EERI, 1996)
Damage at Wall-Slab Junction Propagation of damage in slab from wall 1985 Chile earthquake (EERI, 1986)
Damage at Wall-Slab Junction Case study (Kaushik and Dasgupta, 2017)
Damage at Wall-Slab Junction Case study (Kaushik and Dasgupta, 2017)
Damage at Wall-Slab Junction (Sherstobitoff et al., 2012)
Structural Analysis
Static Analysis Structural Analysis No time dependence of forces and deformations Linear Estimation of stress resultants at design level Nonlinear Pushover analysis Estimation of stress resultants under actual conditions
Structural Analysis Static Analysis No time dependence of forces and deformations Linear Estimation of stress resultants at design level Nonlinear Pushover analysis Estimation of stress resultants under actual conditions Dynamic Analysis Time dependence Inertial and damping effects Linear Nonlinear
Structural Analysis Static Analysis No time dependence of forces and deformations Linear Estimation of stress resultants at design level Nonlinear Pushover analysis Estimation of stress resultants under actual conditions Dynamic Analysis Time dependence Inertial and damping effects Linear Nonlinear
First level Modelling requirements Limit State Method of Design Estimation of design level forces and moments Linear elastic analysis under design load combinations» IS:1893 (Part 1) 2016» IS:13920-2016 Second level Performance evaluation after capacity based design Estimation of seismic capacity Sequence of occurrence of possible failure modes Displacement controlled nonlinear static analysis
Structural Modelling
Structural Modelling RC Frame Buildings with Masonry Infill Walls
Design Level Analysis Modelling for design level force demand 2-noded frame (beam-column) element Centre-line modelling 4-noded shell element Planar element (mid-surface) modelling 2-noded strut element for unreinforced masonry infill wall Sec. 7.9 of IS:1893 (Part 1)-2016 Rigidity of beam-column joints Offset modelling
Modelling of Material Nonlinearity Failure modes Lumped plastic hinges in frame members Hinge Priority
Plasticity in Structural Members Distributed Plasticity Micromodeling Elastoplastic behavior Plastic Hinge Region σ s ε s BMD M y M p (Murty, 2005)
Plastic Hinges Lumped Plasticity Macromodeling Elastoplastic behavior at a section σ s ε s M M p M p M p 2 M p (Murty, 2005)
Plastic Hinges Actual Constitutive Properties Concrete Confined Unconfined Reinforcement Strain-hardening σ c σ s Confined f u Unconfined σ y ε c ε y ε s
Plastic Hinges Actual Constitutive Properties Concrete Confined Unconfined Reinforcement Strain-hardening σ c Confined f u σ s Unconfined IS:456-2000 f y IS:456-2000 ε c ε y ε s
Plastic Hinges Moment-Rotation curve Flexural failure Member characteristic M M M u M y 0.2M y 0 y u Idealised Curve
Plastic Hinges Axial Force-Moment curve Flexural failure Section characteristic P P Compression P T M 0 M Balance Point Tension P C Idealised Curve
Plastic Hinges Shear Force-Shear Displacement curve Shear failure Section characteristic V V V max V s,max Δ 0 Δ y Δ u Δ
Plastic Hinges Axial Force-Axial Displacement curve Compression failure Member characteristic Single strut model H H H max 0.2H max m
Structural Modelling RC Frame Buildings with Structural Walls
Analysis Outcome Design level stress resultants V M P M V
Macro-modelling :: Slender Walls Equivalent Frame Model Wall Rigid link Centerline of Wall H s H s Lumped properties of wall L w L w (Smith and Girgis, 1984; FEMA 356, 2000)
Macro-modelling :: Squat Walls Strut-and-Tie model (Hwang et. al., 2001) Combination of three mechanisms Compression softening of concrete V Diagonal Mechanism V V Vertical Mechanism Horizontal Mechanism
Macro-modelling :: Fibre Modelling (a) Shear wall (c) Fibre section (b) Equivalent beam-column (d) Constitutive properties (Ureta, 2016)
Micro-modelling Brick element for concrete Truss element for rebar Modelling of reinforcement Shear wall-slab assembly Discretization of concrete part (Pantazopoulou and Imran, 1992; Kaushik and Dasgupta, 2017)
Micro-modelling Confinement effect 2-noded truss element Confined Concrete Unconfined Concrete 8-noded solid element
Micro-modelling Two layers of reinforcement Total Concrete Area Unconfined Concrete Area Confined Concrete Area
Micro-modelling One layer of reinforcement Total Concrete Area Unconfined Concrete Area Confined Concrete Area
Micro-modelling Concrete Damaged Plasticity (CDP) model Degradation of strength and stiffness Extent of damage in concrete Actual behaviour of reinforcement Strain hardening σ c Confined f u σ s Unconfined σ y ε c ε y ε s
Current Concern Difference with observed behaviour Bernoulli Region Disturbed Region (Kaushik and Dasgupta, 2017)
Acknowledgement Bureau of Indian Standards Consulting Engineers Association of India Indian Institute of Technology Guwahati C. V. R. Murty, IIT Madras Snehal Kaushik, GIMT, Guwahati Hemant B. Kaushik, IIT Guwahati Earthquake Engineering Research Institute, USA Research papers
Thank you Contact details: Kaustubh Dasgupta kd@iitg.ac.in, kaustubh.dasgupta@gmail.com