Safe Built Environment

Dr. J.N.Jha Dean (Testing & Consultancy Cell) Guru Nanak Dev Engineering College, Ludhiana Punjab The EQ Tips for Creating Safe Built Environment

Latest in the Series of Natural Disasters: Earthquake in Indian Ocean on 26 th December 2004 Generating Huge Tsunami Waves Killing Thousands

Inside the Earth ,[object Object]

Inside the Earth (Contd.) ,[object Object],[object Object]

Local Convective Currents in the Mantle The Circulations Convection currents develop in the viscous Mantle, because of prevailing high temperature and pressure gradients between the Crust and the Core, like the convective flow of water when heated in a beaker

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Types of Inter-Plate Boundaries Convergent Boundary Transform Boundary Divergent Boundary The convective flows of Mantle material cause the Crust and some portion of the Mantle, to slide on the hot molten outer core. This sliding of Earth’s mass takes place in pieces called Tectonic Plates .

[object Object],[object Object], For example, the energy released during the 2001 Bhuj (India) earthquake is about 400 times (or more) that released by the 1945 Atom Bomb dropped on Hiroshima!!

Elastic Rebound Theory Elastic Strain Build-Up and Brittle Rupture

The slip generated at the fault during earthquakes is along both vertical and horizontal directions (called Dip Slip ) and lateral directions (called Strike Slip ) with one of them dominating sometimes. Large strain energy released during an earthquake travels as seismic waves in all directions through the Earth’s layers, reflecting and refracting at each interface.

Arrival of Seismic Waves at a Site Type of Faults

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Direction of Energy Transmission Motions caused by Body and Surface Waves ( Adapted from FEMA 99, Non-Technical Explanation of the NEHRP Recommended Provisions)

Earthquake generation along a fault ,[object Object],[object Object]

So here’s the big picture of what we’re living on

Schematic of Early Seismograph

[object Object],[object Object],[object Object],[object Object],[object Object],Recent Earthquakes…

[object Object],[object Object],[object Object],[object Object],… .Recent Earthquakes…

Some Past Earthquakes in India

Within the last two hundred years, India has experienced five great earthquakes, each with Richter magnitude exceeding 8. The regions where these occurred are as follows: ,[object Object],[object Object],[object Object],[object Object],[object Object]

What are the Seismic Effects on Structure ,[object Object],[object Object],[object Object],[object Object]

What are the Seismic Effects on Structure ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What are the Seismic Effects on Structure ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What are the Seismic Effects on Structure ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Affect of Architectural Features on Bld on during EQ ,[object Object],[object Object],[object Object]

Affect of Architectural Features on Bld during EQ ,[object Object],[object Object],[object Object],[object Object]

Affect of Architectural Features on Bld during EQ ,[object Object],[object Object],[object Object],[object Object],[object Object]

Affect of Architectural Features on Bld during EQ ,[object Object],[object Object],[object Object],[object Object],[object Object],Contd………

Affect of Architectural Features on Bld during EQ ,[object Object],[object Object],[object Object]

How building twists during Earthquake ,[object Object],[object Object],[object Object],[object Object],Contd………

How building twists during Earthquake ,[object Object],[object Object],Contd………

How building twists during Earthquake ,[object Object],Contd……… ,[object Object],[object Object]

How building twists during Earthquake ,[object Object],[object Object],[object Object],[object Object]

How building twists during Earthquake ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],Seismic Design Philosophy for Building

Seismic Design Philosophy for Building ,[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],Seismic Design Philosophy for Building

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Seismic Design Philosophy for Building

[object Object],[object Object],[object Object],[object Object],Flexibility of Building Affects their EQ Response Contd………

[object Object],[object Object],[object Object],Flexibility of Building Affects their EQ Response

[object Object],[object Object],[object Object],Flexibility of Building Affects their EQ Response ,[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],Behaviour of Brick Masonary Houses during EQ

[object Object],[object Object],[object Object],[object Object],Behaviour of Brick Masonary Houses during EQ

[object Object],[object Object],[object Object],Simple Structural Configuration required for Masonary Building ,[object Object],Contd………

[object Object],[object Object],Simple Structural Configuration required for Masonary Building Contd………

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Simple Structural Configuration required for Masonary Building

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Horizontal Band necessary in Masonary Building Contd……… TYPES OF HOR. BANDS

[object Object],Horizontal Band necessary in Masonary Building Contd……… Lintel Band:-- ---Most important needs to be provided in almost all buildings --- Ties the walls together and creates a support for walls loaded along weak directions from walls loaded in strong directions --- Bands also deduces the unsupported height of the walls and thereby improve their stability in weak direction

[object Object],Horizontal Band necessary in Masonary Building Roof Band:-- ---To be provided in building with flat timber or GI Seats roofs only --- This band is not required with flat reinforced concrete or reinforced brick roofs (Roof slab) Plint Band:-- --- It is used when there is concern about uneven settlement.

[object Object],Horizontal Band necessary in Masonary Building

[object Object],Horizontal Band necessary in Masonary Building ,[object Object],[object Object],[object Object],[object Object],Contd………

[object Object],Horizontal Band necessary in Masonary Building ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Vertical Band necessary in Masonary Building ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Vertical Band necessary in Masonary Building ,[object Object],[object Object],[object Object],[object Object]

[object Object],Vertical Band necessary in Masonary Building ,[object Object],[object Object],[object Object]

[object Object],Vertical Band necessary in Masonary Building ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Effect of Earth Quake on RC Building ,[object Object],[object Object],[object Object],[object Object]

[object Object],Effect of Earth Quake on RC Building ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Effect of Earth Quake on RC Building ,[object Object],[object Object],[object Object]

[object Object],How do Beams in RC Bld resist EQ ,[object Object],[object Object]

[object Object],How do Beams in RC Bld resist EQ ,[object Object],[object Object],[object Object]

[object Object],How do Beams in RC Bld resist EQ ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],How do Columns in RC Bld resist EQ ,[object Object],[object Object],[object Object],[object Object]

[object Object],How do Columns in RC Bld resist EQ ,[object Object],[object Object],[object Object],[object Object],[object Object],beyond hook bend must be atleast 10d of steel bar ( close ties) but not less than 75 mm.

[object Object],How do Columns in RC Bld resist EQ ,[object Object],[object Object]

[object Object],How do Beam Column Joins in RC bld Resist EQ ,[object Object],[object Object],[object Object]

[object Object],How do Beam Column Joins in RC bld Resist EQ  Under these moments, the top bar in the beam-column joint are pulled in one direction & the bottom one in opposite direction.  The forces are balanced by bond stress developed between concrete and steel in the joint region  If there is insufficient grip of concrete on steel bars in such circumstances, the bar slip inside the joint region, the beam loose their capacity to carry load

[object Object],How do Beam Column Joins in RC bld Resist EQ   Under this pull- push forces at top and bottom ends joint undergo geometric distortion   One diagonal length of the joint elongates and the other compresses. If the column cross- sectional size is insufficient, the concrete in the joint develops diagonal cracks

[object Object],How do Beam Column Joins in RC bld Resist EQ   Problem of diagonal cracking & crushing of concrete in the joint region can be controlled by a) Providing large column size b) Providing closely spaced closed loop steel ties around column bars in joint region  Ties hold together the concrete in the joint and also resist shear force.

How do Beam Column Joins in RC bld Resist EQ ,[object Object], Three stage procedure for providing horizontal ties in the joints

How do Beam Column Joins in RC bld Resist EQ ,[object Object], Anchorage of beam bars in interior joints

[object Object],Why are Soft storey building vulnerable in EQ  Relatively flexible in the ground storey, also called Soft storey.(Relative horizontal displacement is much larger as compared to the above storey)  Relatively weak storey in ground storey (Weak Storey)  Such buildings are extremely vulnerable under earthquake shaking

[object Object],Why are Soft storey building vulnerable in EQ  Presence of walls in upper storeys make them much stiffer than the open ground storey  Upper storeys move almost as a single block and most of the horizontal displacement occurs in the soft ground storey itself

[object Object],Why are Soft storey building vulnerable in EQ

[object Object],Why are Soft storey building vulnerable in EQ   In the current practice, stiff masonry walls are neglected and only bare frames are considered in design calculation   After 2001 Gujrat EQ , IS : 1893 (Part –1)- 2002 has given special design provisions related to soft storey buildings   Special higher design forces for the soft storey as compared to the rest of the structure   Beam and column in the open ground storey are required to be designed for 2.5 times the forces obtained from bare frame analysis

[object Object],Why are Short Columns more Damaged During EQ  Bld resting on sloped ground consisting of short & long column, when shakes, all column move horizontally by the same amount along with floor slab at a particular level  Short column effect also occurs in columns that support mezzanine floor or loft slabs that are added in between two regular floors.

[object Object],Why are Short Columns more Damaged During EQ  A tall column & a short column of same cross section move horizontally by same amount during EQ  Short column is stiffer than long column(Stiffness of column means resistance to the deformation)  Larger is the stiffness, larger is the force required to deform it

[object Object],Why are Short Columns more Damaged During EQ  If a short column is not adequately designed for such large force, it can suffer significant damage during EQ  Short column attracts several times larger force and suffer more damage as compare to taller ones.  This behaviour of short column is called short column effect and often the damage is in the form of X –shaped cracking (Shear Failure)

[object Object],Why are Short Columns more Damaged During EQ  Special Confining reinforcement is to be provided over the full height of column that are likely to sustain short column effect  Special confining reinforcement must extend beyond the short column into the column vertically above and below by certain distance

[object Object],Why are Short Columns more Damaged During EQ  In new building, short column effect should be avoided to the extent possible during Architectural design itself For short columns in the existing building retrofit solutions can be employed to avoid damage in future Earth Quake The retrofit solution should be designed by a Qualified structural Engineer with requisite background

[object Object],Why are Bld with Shear Walls preferred in Seismic Regions   Reinforce concrete (RC) Bld often have vertical plate like RC walls called Shear walls   Shear walls are generally start at foundation level and are continuous throughout the building height  Thickness range; 150 mm to 400 mm  Shear walls are usually provided along both length and width of Bld  Shear walls are like vertically originated wide beams that carry EQ load downwards to the foundation  Shear walls are efficient both in terms of const. Cost and effectiveness in minimizing EQ damage in Structural & Non-Structural Member

[object Object],Why are Bld with Shear Walls preferred in Seismic Regions   Shear walls in building must be symmetrically located in plan to reduce ill effects of twist in building  Shear walls are more effective when located along exterior perimeter of building

[object Object],Why are Bld with Shear Walls preferred in Seismic Regions

[object Object],Why are Bld with Shear Walls preferred in Seismic Regions   Steel reinforcing bars are to be provided in walls in regularly spaced vertical & horizontal grids  Vertical and horizontal reinforcements in the wall can be placed in one or two parallel layers called curtains  Horizontal reinforcements needs to be anchored at the ends of wall  Minimum area of reinforcing steel to be provided is 0.0025 time the cross sectional area (Along each of the horizontal & vertical directions)

[object Object],How to reduce EQ effects on Buildings  Lifeline structures like hospitals etc are remain to be functional in the aftermath of EQ Special techniques are required to design such life line structures which usually cost more than normal bld do Two basic technology are a) Base isolation device b) Seismic Dampers

[object Object],How to reduce EQ effects on Buildings a) Base isolation device - Idea behind base isolation is to detach (isolate) the buildings from the ground in such a way that EQ motions are not transmitted up through the building or at least reduced b) Seismic Dampers - Special devices introduced in the building to absorb the energy provided by the ground motion to the building

How to reduce EQ effects on Building a) Base isolation device - Idea behind base isolation is to detach (isolate) the buildings from the ground in such a way that EQ motions are not transmitted up through the building or at least reduced b) Seismic Dampers - Special devices introduced in the building to absorb the energy provided by the ground motion to the building

How to reduce EQ effects on Building ,[object Object],[object Object],[object Object],[object Object],[object Object]

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