EQ Risk Management



From: |Hsrai | |

|To: |suraj |

|Posted|28 Oct 2009 17:40 |

|: | |

|Subjec|Request for resource person: EQ Risk Management | |

|t: | | |

|Respected Sir, |

|We are conducting a course entitled "Capacity Building of Engineers in Earthquake Risk Management" during 2nd week of Dec 2009 i.e|

|7-12 Dec. I request you to spare one or two day, and be part of this course as resource person [even you may suggest to add or |

|remove something]. The contents of course may be accessed by visiting: , then click on "Contents" |

|The course is meant for working professional of Govt. Department. Hoping to see you at GNDEC, Ludhiana. With kind regards, -- |

| |

|Dr. M.S. Saini director@gndec.ac.in Phone No. 0161-2490339, 2502700 Fax No. 0161-2502240 Guru Nanak Dev Engineering College Gill |

|Park Ludhiana 141006 Punjab(India) |

|  |

| |

|Head of the Department Civil Engineering Department Guru Nanak Dev Engineering College Ludhiana (Punjab) |

|Pin: 141006 India Phone: 91 161 2490 339 Ext 208 Email: civil@gndec.ac.in Dr. H.S.Rai Prof. and Head |

|Civil Engineering Department Guru Nanak Dev Engg. College Ludhiana (Pb) India |

|Mobile 098552 25007 |

San 2010 ki Aap Sabhi Ko Shub Kamnai (Happy Year 2010 To All)

Course schedule: Dec 28/12/2009 to 2/1/2010 /

This Talk On 01/01/2010 to 02/01/2010

EQ Risk Management Note

Scope Of This Session

Earthquake Preparations Preventive & Curative

Go To Seismology & Rock Mechanics.

Go To Soil Mechanics and Earthquake Resistant Design

Go To Soil-Structure Interaction and Foundation Design

Go To Site Planning, Building Forms and Architectural Design Concept for Earthquake Resistance.

Go To Structural Systems For Earthquake Resistance.

Go To Structural Analysis: Gravity and Lateral Loading.

Go To Structural Design and Ductile Detailing.

Go To Strength & Retrofitting of Structures & Vulnerability Assessment.

Go To Seismic Risk Management in Action.

Go To Effect on Natural and Built Environment

Go To Reference Example & QA

Presentation By

Professional Engineer Suraj Singh

25 Years + Experience (18 Years Overseas) RCC Buildings & Onshore Oil

Thanks to Dr. H.S.Rai Prof. and Head

Civil Engineering Department extending me an opportunity for this presentation

Back Earthquake Preparations Preventive & Curative:

This presentation is meant for the civil field engineers & high ups to apprise themselves about the earthquake involvement factors that make an impact on building designs. No engineering formulas are included herein due to the fact that all qualified engineers have learnt that during engineering training. This document is submitted as an objective projectile to those aspiring for practical potential backup know how & meant only for refreshing respective reader about the subject. Easy text has been used while composing the descriptive information. It is hoped that readers would find the explanations interesting for updating professional awareness. It is generally meant for the middle level government, corporate sector engineers & other engineering buds. No new knowledge has been added but rather, a collection of various already known information, has been made for the assistance of reader to serve as a reference, whenever required. It is advised that civil/structural engineers have been interacting regularly on whereon, all you good engineer may raise questions for experts feed back & suggestions. You may also advise the budding engineers. Many of you are experts in the government services operation thereby, by virtue of which specialization, you may help the nation.

Please refer to various slides & other documents from various sources included to support this note.

Back Seismology & Rock Mechanics:

Prior to entering to deliberate the subject, it is advisable to refresh about the Earth’s crust from Applied Science of Geology view point. Applied Geology is a branch of Earth’s science that is a must to be understood by any Civil Engineer without which, a civil engineer would definitely feel missing a lot about the structural foundations.

Lithosphere Indicative Model

Lithosphere Model On Cad

Preliminary explanation regarding Lithosphere:

Earth- What is meaning of Earth? Is it the globe solid surface? What else consists of Earth? What relevance does it have on the system of this planet towards environment up to space?

Earth= Lithosphere + Aerosphere = Solid globe + Air envelope surrounding Lithosphere

Lithosphere = Solid portion of Globe = About 12000 Km generally

Lithosphere = Core + Mantle + Crust: where crust is uppermost, Mantle is in the intermediate portion while Crust is within top 35 Km.

1. Crust represents such as skin of an apple containing all seas & oceans.

2. Mantle goes down to about 2500 Km of Lithosphere interior with increasing temperature & densification of material in.

3. Core goes further down to the centre of Lithosphere where materials are found in liquid state but with higher densities & rising temperatures.

4. Crust generates all earth quakes actions in the form of rocking of earth crust due to the stored strain energy within, that is released due to imbalance & the release continues until re equilibrium is established.

5. A parallel portion to the Lithosphere up to say 18 to 20 km from sea or surface constitutes aerosphere within which volume, various gases, photons, sun rays involving huge chemical reactions work that are responsible for changing regularly occurring on Lithosphere.

6. Generally speaking, the seas constitutes up to 4 Km of sea level while oceans go down up to 10 Km. The sea or oceanic floors are generally basaltic in nature having stronger rocks.

7. Lithosphere Crust portion, creates by eruption of magma/lava, by wind erosion, by environment adverse effects, by variation of temperatures, by works of various other agencies’ effects imposition, do form various types of topping of crust such as rocks classified as Volcanic, Sedimentary & Metamorphic that are responsible to force all engineers to fit their designs according to the properties of these beds. Similarly, wind erosion responds to the formation of sands beds or alluvial planes.

8. Due to the continuous movements by the release of volcanic material as said by magma erupting & in some places, entering in to the crust again by convection after having cooled immensely, the cycle works to impose various changes on the crust & in particular, on the limits within which the foundations are to be placed. Rock movement by the name of Plutonic Plates involved motion keep on working & their movement towards each other, make extension of continents while their breaking at certain points forms new continents.

Earthquakes are defined as, ‘Ground shaking and radiated seismic energy caused mostly by sudden slip on a fault, volcanic or any sudden stress change in the earth’.

PresentationEQ.ppt

Back Soil Mechanics and Earthquake Resistant Design:

1. Should we call Applied Geology as the title subject, soil mechanics is the chapter like subordinate subject. Earthquake Resistant Design is a specialist subject then.

2. Soil Mechanics = Soil Engineering +Soil Static + Soil Dynamics +Soil Testing, Exploration & Reporting + Soil Tomography + Soil Development + Soil Foundation Interactions

3. All naturally formed materials whatever is available in any form, in portion utilizable for foundations inclusion of any structure, is or can be called soil & includes all rocks, sands, clays, silts, gravels, pebbles & soil water etc.

4. Soil Mechanics operations are solely responsible to tell engineer what to do to decide about any foundation? When all soil investigation reports are available in elaborate details, no need arises to make any approximate assumptions keeping in view the generality of the proposed foundations areas. Based on these soils performance in the long past resembling to the available rocking data, with assessed EQ intensity, the zoning of the areas are carried out. That provision of designating any area any where, is termed as Seismic Zoning.

5. An engineer who understands the clear concept of available reports from the materials testing laboratory, would be in a definitely certain position to make a good decision on the design based on the soil engineer’s recommendations with additions of his own interpretation of the reports parameters. Earthquake resistant effects shall be rightly provided within the proposed foundations in such a situation of engineer’s interpretations of the reports. It is also true that detailed studies are never made in the educational training programmes anywhere. Even, the master degrees do not provide detailed understanding about EQ, the most significant subject from design engineering viewpoints.

Back Soil-Structure Interaction and Foundation Design:

1. This topic is in continuation to the foregoing explanation as the foundation is to be placed on soil while the two parts of structural & soil component must work together integrally for the successful performance of any sub structural system.

2. Soil may contain any compact or spatial structure or cohesive or frictional structural grains depending on soil nature. It may also be constructed of platelets. Even rocks may be adversely affected by the weak planes faults or bends or cracks or fissures or cavities. Rock may be weathered. Soil could be clay or silt or sandy or peat or other. All soils work with the foundations in one form or other but are supposed to work as a team for a successful safe foundation.

3. Water being dangerous by its presence in the soil or rock mass either in moisture form or laminar or turbulent flow form. Since, soil contains various chlorides or sulphides or various types of carbonates in either loose or in dissolved form & these compositions keep on altering for years & decades, may affect the soil performance badly. Water keeps moving within voids & with that, provides all these chemicals to soil that changes the soil chemical properties affecting its performance or resisting power. Water is better to be kept off the soil mass by providing various means or methods of constructions.

4. Permeability is a property that allows water to flow within soil mass of interconnecting voids soils. Sand, gravels, pebbles etc constitute such soils. Such soils are dominated by angle of internal friction.

5. Porosity is the property that allows water to remain stored for certain duration within soil mass imposing soil swelling pressure from within voids. Clay & Silt are such soils. Such soils are badly affected by capillary actions. Foundations are designed based on all these considerations by applying the interactions between the available soil strata & the proposed foundation elements. Such soils are dominated by cohesion.

Ref CRC Press: Earthquakes are naturally occurring broad-banded vibratory ground motions, caused by a number of phenomena including tectonic ground motions, volcanism, landslides, rock bursts and human made explosions. Of these various causes, tectonic-related earthquakes are the largest and most important. These are caused by the fracture and sliding of rock along faults within the Earth’s crust. A fault is a zone of the earth’s crust within which the two sides have moved—faults may be hundreds of miles long, from 1 to over 100 miles deep and not readily apparent on the ground surface. Earthquakes initiate a number of phenomena or agents termed seismic hazards, which can cause significant damage to the built environment—these include fault rupture, vibratory ground motion (i.e. shaking), inundation (e.g. tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. liquefaction), fire or hazardous materials release. For a given earthquake, any particular hazard can dominate and historically, each has caused major damage and great loss of life in specific earthquakes. The expected damage given a specified value of a hazard parameter is termed vulnerability and the product of the hazard and the vulnerability (i.e. the expected damage) is termed the seismic risk.

Ref CRC Press LLC Causes of Earthquakes and Faulting

In a global sense, tectonic earthquakes result from motion between a number of large plates comprising the earth’s crust or lithosphere (about 15 in total). These plates are driven by the convective motion of the material in the earth’s mantle, which in turn is driven by heat generated at the earth’s core. Relative plate motion at the fault interface is constrained by friction and /or asperities (areas of interlocking due to protrusions in the fault surfaces). However, strain energy accumulates in the plates, eventually overcomes any resistance and causes slip between the two sides of the fault. This sudden slip, termed elastic rebound by Reid based on his studies of regional deformation following the 1906 San Francisco earthquake, releases large amounts of energy, which constitutes the earthquake. The location of initial radiation of seismic waves (i.e. the first location of dynamic rupture) is termed the hypocenter, while the projection on the surface of the earth directly above the hypocenter is termed the epicenter. Other terminology includes near-field (within one source dimension of the epicenter, where source dimension refers to the length or width of faulting, whichever is less), far-field (beyond near-field), and meizoseismal (the area of strong shaking and damage). Energy is radiated over a broad spectrum of frequencies through the earth, in body waves and surface waves. Body waves are of two types: P waves (transmitting energy via push-pull motion), and slower S waves (transmitting energy via shear action at right angles to the direction of motion). Surface waves are also of two types: horizontally oscillating Love waves (analogous to S body waves) and vertically oscillating Rayleigh waves.

While the accumulation of strain energy within the plate can cause motion (and consequent release of energy) at faults at any location, earthquakes occur with greatest frequency at the boundaries of the tectonic plates. The boundary of the Pacific plate is the source of nearly half of the world’s great earthquakes. Stretching 40,000 km around the circumference of the Pacific Ocean, it includes Japan, the west coast of North America and other highly populated areas and is aptly termed the Ring of Fire. The interiors of plates such as ocean basins and continental shields, are areas of low seismicity but are not inactive — the largest earthquakes known to have occurred in North America for example, occurred in the New Madrid area far from a plate boundary. Tectonic plates move very slowly and irregularly with occasional earthquakes. Forces may build up for decades or centuries at plate interfaces until a large movement occurs all at once. These sudden, violent motions produce the shaking that is felt as an earthquake. The shaking can cause direct damage to buildings, roads, bridges, and other human-made structures as well as triggering fires, landslides, tidal waves (tsunamis), and other damaging phenomena.

Faults are the physical expression of the boundaries between adjacent tectonic plates and thus may be hundreds of miles long. In addition, there may be thousands of shorter faults parallel to or branching out from a main fault zone. Generally, the longer a fault the larger the earthquake it can generate. Beyond the main tectonic plates, there are many smaller sub-plates (platelets) and simple blocks of crust that occasionally move and shift due to the “jostling” of their neighbors and/or the major plates. The existence of these many sub-plates means that smaller but still damaging earthquakes are possible almost anywhere, although often with less likelihood.

Generally, earthquakes will be concentrated in the vicinity of faults. Faults that are moving more rapidly than others will tend to have higher rates of seismicity and larger faults are more likely than others to produce a large event. Many faults are identified on regional geological maps, and useful information on fault location and displacement history is available from local and national geological surveys in areas of high seismicity. Considering this information, areas of an expected large earthquake in the near future (usually measured in years or decades) can be and have been identified. However, earthquakes continue to occur on “unknown” or “inactive” faults. An important development has been the growing recognition of blind thrust faults, which emerged as a result of several earthquakes in the 1980s, none of which were accompanied by surface faulting. Blind thrust are faults at depth occurring under anticlinal folds—since they have only subtle surface expression, their seismogenic potential can be evaluated by indirect means only. Blind thrust faults are particularly worrisome because they are hidden, are associated with folded topography in general including areas of lower and infrequent seismicity and therefore, result in a situation where the potential for an earthquake exists in any area of anticlinal geology even if, there are few or no earthquakes in the historic record. Recent major earthquakes of this type have included the 1980Mw 7.3 El- Asnam (Algeria), 1988 Mw 6.8 Spitak (Armenia), and 1994 Mw 6.7 Northridge (California) events. Probabilistic methods can be usefully employed to quantify the likelihood of an earthquake’s occurrence, and typically form the basis for determining the design basis earthquake.

Tsunami:

Tsunami is a Japanese word meaning ‘The Harbor Wave’.

Shallow water waves with destructive potentials that propagate with greater speeds transferring tectonic energy towards land from beds across oceans increasing in height as they approach land.

Causes of Tsunamis:

Tsunamis are usually caused by underwater earthquakes often, occuring offshore at subduction zones (a tectonic plate that carries an ocean gradually slips under a continental plate). A receding sea usually precedes a tsunami wave. In most cases there is also drawdown of sea level preceding crest of the tsunami waves.

Landslides can also cause tsunamis by displacing large volumes of water.

If Volcano collapses and slides into the ocean it may also create a very large tsunami wave.

They are caused by earthquakes or landslides.

Tsunamis can be generated when the seafloor abruptly deforms vertically displacing

large volume of water which under the influence of gravity forms waves around it in order to reach equilibrium .

Displaced water mass.

Tectonic earthquakes can cause tsunamis when a tectonic place subsides or rises. Along plate faults, is where vertical movements of plates take place. Subduction zones are usually sources of large tsunamis. During subduction earthquake, offshore ocean bottom lifts up the land along the coast lowers down.

However, an earthquake generating process is not understood well enough to reliably predict the times, sizes, and locations of earthquakes with precision. In general, therefore, communities must be prepared for facing an earthquake to occur at any time. No nation is perfect in EQ Risk Management. Only prevention & post EQ disaster management can be ascertained by one & all responsible citizens.

Back Site Planning, Building Forms and Architectural Design Concept for Earthquake Resistance:

1. Prior to starting planning for any building site, it is a requirement particularly for projects going to consume high quantity of concrete & other reinforcement, to carry out a reasonable level of soil investigation & the report should be made available to the designer immediately for studies & a good understanding of recorded parameters. Prior investigation of soil may also indicate the non suitability of the proposed site or it would be uneconomical from various aspects or constructability / build ability issue may cause a problem for a smooth passage of construction.

2. Practice had been that an architect used to conceive any building & produces its envelope details to ideals thought of. This applied to buildings constructed of stone or brick masonry. Should one refer to old buildings for example Taj Mahal or Red fort or even old houses /havelees, one would find walls too thick. I remember one of my professor in 1974 instructed that brick single wall of 225 mm could take the building safely up to 3 storey with 3 to 4 m span size room. Actually, in those days there, was no consideration of Earthquake Resistance technologies that can help a lot buildings construction in general.

3. After conception of any building at schematic stage, next step should be to fit in the dream on to the proposed available plot. The complete setting out of the main as well as ancillary buildings follows & the plan is given final architectural touch including an attractive perspective or an isometric view. These plans are given to the engineer to insert in the structural mechanism or skeleton in to it to satisfy the demanded requirements by the architect. Various instances have been witnessed where the architect defines the dimensions of the column sections with locations. These conditional qualifications on the given drawings generally, prohibit engineer to work independently for making design decisions about the framing of the building.

4. Meetings are held to explain to the architect about the forces compatibility problems caused by the defined locations & members sizes. In case, architect is rigid on assumed locations, engineer may not help the design to amend but to continue designing on the given locations. Best practice would have been had the architect given a free hand to designer to locate the members & then discuss with the architect about the adoptability for a better structural formation. During mechanizing process of the structure, an engineer can conceive & anticipate where to & in which locations of members, critical forces would generate & would help members to be correctly located to respond to earthquake language.

5. Analysis of the superstructures can be easily carried out to meet given requirements in accordance with various recognized structural systems for multistory & high rise buildings. For low rise buildings structures, a lot depends on the concept of design engineer to chart out decisions for the projections of possible foundations. Since variations do occur for the spans fixing, that would certainly make the structures different in the substructure as well as superstructure formation mechanism.

6. Facets demanded makes a difference on the structural framings. Architects generally intend to hide the structural members while, these also can add to the building elevations. Any low rise building can be analysed by 2 D or 3 D systems. I have used for many analysis the non practiced Kani’s Rotation Contribution method that provided reliable forces to be adopted for designing & detailing. Earthquake resistance solution parameters & formula to be used, which have been coded as well as given in the available literature. But as a thumb rule, a 25 % building mass can be used as horizontal seismic shear around the whole building.

7. It is also kept in view that wind loads & seismic forces do not act together. Only one should be considered one time. It is a fact that horizontal forces would impact the structure to be deflected or swayed away diagonally introducing torsion into the building as well as transferring moments to the foundations. All these developed forces need considerations of adjustments within designs.

8. Main point herein is to know how to develop a structure that would resist the seismic actions resulting vibrations being imposed on the building to be dampened gradually within seconds of applications of the forces. This method needs to be considered at all levels of the structures. Seismic forces act at the foundations laterally & continue to transfer to the upper levels. In fact, we can consider a building as a machine for all practical purposes. Reliable stability can be provided to the soil foundation system.

9. Building should be as light as possible. Light building means low mass value.

10. Foundations should be spread in such a way that maximum area of soil contact is feasible. Maximum contact area means low upward reaction.

11. Foundation structure should not localize the upward reactions but spreaden as uniform distributed reaction load.

12. Foundation should rest on a soil that would provide the required safe bearing capacity as well as have good shear resistance with minimum predicted settlement. Minimum settlement & reaction UDL economise construction cost.

13. Need not mention that unequal settlement should be avoided.

14. Let us take example of a wooden stool that is constructed sometimes, by providing either vertical post or by inclined posts duly tied at the bottom or top of the posts. This stool is stirred horizontally but it remains stable after vibrations. Similar concept can be applied to any building just to understand the basics.

15. Generally, Buildings are provided with cantilever footings/spread footings/independent foundations. Well, these foundations work acceptably fine to the requirement of direct load & also, part of bending moments but, the cantilever is not supposed to be economical as it does not work safely when imposed upon by EQ vibratory forces.

16. One way to come out of this problem is to add connecting beams to foundations level or at the plinth level. If connected at the foundation level, these may share foundation loads jointly with the foundation pads. At plinth level, these would add to the stability of the lower storey columns. These have been successful for decades.

17. Seismic forces while acting horizontally need concrete members to digest/absorb or dampen the forces. In case, all these foundations & connecting or plinth beams are replaced by the standalone beam frames in both directions as a mat or to work in stool fashion, a considerable dimension diaphragm shall be available for the seismic forces to be resisted with. In this situation, all the beams in both directions shall work as a frame while depth of the frame being considerable say 900 mm to 1200 mm or even 1500 mm with 300 to 500 mm width. This can well apply to ordinary low rise buildings say up to 4 to 5 stories high.

18. Advantage would be that absenting cantilever actions would result in less bending moments. The imposed lateral forces shall be comfortably resisted. All these frame members in both directions shall act as virtual columns during earthquake allowing only small fraction of forces to the superstructure.

19. I have used this method for many designs successfully. Since, foundations are in beam form, skin reinforcement too shall be provided. Stirrups shall run all ways/grids of the framings adding to the shear resistance, punching resistance & providing adequate development length to column reinforcing bars. The portion left among peripheral beams can be used to be plugged in by concrete fill or by granular fill in case, water table or moisture content do not pose a threat to foundations. Moreover, in certain bays, water storage tank can be used by making certain amendment to designs. Columns extend or protrude out from the foundation framing in the form of stubs. Superstructure can be started from that point onwards.

20. Columns size in section should never be compromised. Depending on the span between columns as well as cross spacing between frames, a responsive & worth constructable size should be selected irrespective of aesthetic look. Practical difficulties should be kept abreast during making decisions on columns & beams sectional dimensions. Small sections with heavy reinforcing bars shall create congestion problems posing vibrator application inefficiency. Adequate thickness concrete spacer or cover is also very significant to be provided with otherwise, protection to the concrete section from moisture penetration, fire attacks cannot be controlled. Deeper cover means lesser rapid chloride penetration in to the core of the member extending the concrete durability. Denser the concrete mix with higher grade means resistance to chloride & moisture penetration.

21. Durable & ductile or ductable structures are demands of the day. The term ductable that I have added to make another understanding of members & building structures in addition to concrete material plastic property avoiding sudden crash. Durability provides the long distance service travel of the structure safely while it depends upon various technical factors including, quality of ingredients of concrete, cement quantity, water quantity, mix design or combined aggregate grading, admixtures added, environment conditions, construction quality controls on total concrete operations.

22. We can just consider a lapse on curing particularly within a few days of pouring due to any reason whatsoever, & carrying out long duration curing thereafter, shall certainly pose threat to the durability of concrete. Concrete would not achieve defined characteristics compressive strength & disintegrate sooner than expected. Lapse on compaction vibrations shall also induce similar adverse impact on the durability part of concrete. Adequate chemical protection may be applied on quality produced concrete members after carbonation in case it is to be left exposed.

23. I can say that whatever definition of ductility of concrete is explained, all element members & the integrated structures should conduct in a way a duct conducts. A duct moves uniformly duly closed in all sections & stresses are equally imposed on it. The induction of this property requires an additional thought on the designer to include reinforcement in such a way that member reinforcement behaves in that fashion. Wherever members are provided, should be equally doubly reinforced. Compression reinforcement can induct additional resistance to stiffness to member thereby, reducing possibility of calculated deflections not exceeded than permitted, means member would resist extra deflection keeping the member safe even if overstressed in inelastic or non linear range. Size control on section can also be established in a good way.

24. Foundations & structures should talk same language during setting out the floor plans to keep the centre of gravity of the loads & plans nearly same. Rigidity cg should pass in line with mass cg. An attempt should be made to avoid undesired cantilevers for aesthetic purpose & if so necessary to be included with, should be adequately designed keeping restrictions on the span. Torsion provision is a must on this member supporting beams. Cantilever requires 5 times strengthening than non cantilever members to resist EQ forces. It is also a good detailing practice to avoid unnecessary overlaps if it is feasible to continue the rebars to the extent of standard lengths. Higher dia bars should be mechanically connected for better working using high strength couplers.

25. High rise or multistory structures are generally designed on pile foundations but it is also not right to say that piles are indispensable to some extent if good responsive soil is available. We should remember that piles too are subject to horizontal force during seismic occurrence & there is a possibility for socketed or friction pile to deflect during EQ attack. In case, rock or good soil is available within foundation scope, it is better to accommodate foundations within that portion avoiding piles. Soil can be improved by many methods applications to erect on heavy foundations. Water has to be kept out of coming in contact with foundations & soil. On various floors of high rise structures, various dampers can be provided that would dissipate passive energies generated from the seismic effects.

Ref CRC Press

Metallic Yield Dampers

One of the effective mechanisms available for the dissipation of energy input to a structure from an earthquake, is through inelastic deformation of metals. The idea of utilizing added metallic energy dissipators within a structure to absorb a large portion of the seismic energy began with the conceptual and experimental work of Kelly et al.

Friction Dampers

Friction dampers utilize the mechanism of solid friction that develops between two solid bodies sliding relative to one another to provide the desired energy dissipation. Several types of friction dampers have been developed for the purpose of improving seismic response of structures.

Viscous Fluid Dampers

Damping devices based on the operating principle of high-velocity fluid flow through orifices have found numerous applications in shock and vibration isolation of aerospace and defense systems. In recent years, research and development of viscous fluid (VF) dampers for seismic applications to civil engineering structures have been performed to accomplish three major objectives. The first was, to demonstrate by analysis and experiment that viscous fluid dampers can improve seismic capacity of a structure by reducing damage and displacements without increasing stresses. The second was, to develop mathematical models for these devices and demonstrate how these models could be incorporated into existing structural engineering software codes. Finally, the third was, to evaluate reliability and environmental stability of the dampers for structural engineering applications.

As a result, VF dampers have in recent years been incorporated into civil engineering structures. In several applications, they were used in combination with seismic isolation systems. For example, VF dampers were incorporated into base isolation systems for five buildings of the new San Bernardino County Medical Center, located close to two major fault lines in 1995. The five buildings required a total of 233 dampers each having an output force of 320,000 lb and generating an energy dissipation c

Tuned Mass Dampers TMD

The modern concept of tuned mass dampers (TMDs) for structural applications has its roots in dynamic vibration absorbers, studied as early as 1909 by Frahm. Under a simple harmonic load, one can show that the main mass can be kept completely stationary when the natural frequency of the attached absorber is chosen or tuned to be the excitation frequency.

Tuned Liquid Dampers TLD

The basic principles involved in applying a tuned liquid damper (TLD) to reduce the dynamic response of structures, are quite similar to those discussed above for the TMD. In effect, a secondary mass in the form of a body of liquid is introduced into the structural system and tuned to act as a dynamic vibration absorber. However, in case of TLDs, the response of the secondary system is highly nonlinear due either to liquid sloshing or the presence of orifices. TLDs have also been used for suppressing wind-induced vibrations of tall structures. In comparison with TMDs, the advantages associated with TLDs include low initial cost, virtually free maintenance and ease of frequency tuning. It appears that TLD applications have been installed primarily in Japan. Examples of TLD-controlled structures include the Nagasaki Airport Tower, installed in 1987, the Yokohama Marine Tower, also installed in 1987, the Shin-Yokohama Prince Hotel, installed in 1992, and the Tokyo International Airport Tower, installed in 1993. The TLD installed in the 77.6-m Tokyo Airport Tower, for example, consists of about 1400 vessels containing water, floating particles and a small amount of preservatives. The vessels shallow circular cylinders 0.6 m in diameter and 0.125 m in height, are stacked in six layers on steel-framed shelves. The total mass of the TLD is approximately 3.5% of the first-mode generalized mass of the tower and its sloshing frequency is optimized at 0.743 Hz. Floating hollow cylindrical polyethylene particles were added in order to optimize energy dissipation through an increase in surface area together with collisions between particles. The performance of the TLD has been observed during several storm episodes. In one such episode, with a maximum instantaneous wind speed of 25 m/s, the observed results show that the TLD reduced the acceleration response in the cross-wind direction to about 60% of its value without the TLD.

Active Control

As mentioned, the development of active or hybrid control systems has reached the stage of full-scale applications to actual structures. Since 1989, more than 20 active or hybrid systems have been installed in building structures in Japan, the only country in which these applications have been installed. In addition, 14 bridge towers have employed active systems during erection.

Back Structural Systems For Earthquake Resistance:

CRC Press LLC Rigid Frames

A rigid frame derives its lateral stiffness mainly from the bending rigidity of frame members interconnected by rigid joints. The joints are designed in such a manner that they have adequate strength, stiffness and negligible deformation. The deformation must be small enough to have any significant influence on distribution of internal forces and moments in the structure or on overall frame deformation.

A rigid unbraced frame should be capable of resisting lateral loads without relying on an additional bracing system for stability. The frame by itself, has to resist all the design forces including gravity as well as lateral forces. At the same time, it should have adequate lateral stiffness against sidesway when it is subjected to horizontal wind or earthquake loads. Even though, the detailing of the rigid connections results in a less economic structure, rigid unbraced frame systems have the following benefits:

1. Rigid connections are more ductile and therefore, the structure performs better in load reversal situations or in earthquakes.

2. From the architectural and functional points of view, it can be advantageous not to have any triangulated bracing systems or solid wall systems in the building

Braced Frames vs. Unbraced Frames

The main function of a bracing system is to resist lateral forces. Building frame systems can be separated into vertical load-resistance and horizontal load-resistance systems. In some cases, the vertical load-resistance system also has some capability to resist horizontal forces. It is necessary, therefore, to identify the two sources of resistance and to compare their behavior with respect to the horizontal actions. However, this identification is not that obvious since the bracing is integral within the structure. Some assumptions need be made in order to define the two structures for the purpose of comparison.

Sway Frames vs. Non-Sway Frames

The identification of sway frames and non-sway frames in a building is useful for evaluating safety of structures against instability. In the design of multistory building frame, it is convenient to isolate the columns from the frame and treat the stability of columns and the stability of frames as independent problems. For a column in a braced frame, it is assumed that the columns are restricted at their ends from horizontal displacements and therefore, are only subjected to end moments and axial loads as transferred from the frame. It is then assumed that the frame, possibly by means of a bracing system, satisfies global stability checks and that the global stability of the frame does not affect the column behavior. This gives the commonly assumed non-sway frame. The design of columns in non-sway frames follows the conventional beam-column capacity check approach and the column effective length may be evaluated based on the column end restraint conditions.

Another reason for defining “sway” and “non-sway frames” is the need to adopt conventional analysis in which all the internal forces are computed on the basis of the undeformed geometry of the structure. This assumption is valid if second-order effects are negligible. When there is an interaction between overall frame stability and column stability, it is not possible to isolate the column. The column and the frame have to act interactively in a “sway” mode. The design of sway frames has to consider the frame subassemblage or the structure as a whole. Moreover, the presence of “inelasticity” in the columns will render some doubts on the use of the familiar concept of “elastic effective length”

On the basis of the above considerations, a definition can be established for sway and non-sway frames as:

A frame can be classified as non-sway if its response to in-plane horizontal forces is sufficiently stiff for it to be acceptably accurate to neglect any additional internal forces or moments arising from horizontal displacements of its nodes. This indicates that non sway frame is stronger to resist lateral forces without providing any other members for such forces. It means that rigidity of frame is higher than its flexibility.

CRC Press LLC Classification of Tall Building Frames

A tall building is defined uniquely as a building whose structure creates different conditions in its design, construction and use than those for common buildings. From the structural engineer’s view point, the selection of appropriate structural systems for tall buildings must satisfy two important criteria: strength and stiffness. The structural system must be adequate to resist lateral and gravity loads that cause horizontal shear deformation and overturning deformation. Other important issues that must be considered in planning the structural schemes and layout are, the requirements for architectural details, building services, vertical transportation and fire safety among others. The efficiency of a structural system is measured in terms of its ability to resist higher lateral loads which increase with the height of the frame. A building can be considered as tall when the effect of lateral loads is reflected in the design. Lateral deflections of tall buildings should be limited to prevent damage to both structural and non-structural elements. The accelerations at the top of the building during frequent windstorms should be kept within acceptable limits to minimize discomfort to the occupants.

The various structural systems can be broadly classified into two main types:

(1) medium height buildings with shear type deformation predominant and

(2) high rise cantilever structures, such as framed tubes, diagonal tubes, and braced trusses. This classification of system forms is based primarily on their relative effectiveness in resisting lateral loads. At one end of the spectrum is the moment resisting frames which are efficient for buildings of 20 to 30 stories, and at the other end is the tubular systems with high cantilever efficiency. Other systems were placed with the idea that the application of any particular form is economical only over a limited range of building heights.

An attempt has been made to develop a rigorous methodology for the cataloging of tall buildings with respect to their structural systems. The classification scheme involves four levels of framing division:

(1) primary framing system,

(2) bracing subsystem,

(3) floor framing, and

(4) configuration and load transfer.

While any cataloging scheme must address the pre-eminent focus on lateral load resistance, the load-carrying function of the tall building subsystems is rarely independent. An efficient high-rise system must engage vertical gravity load resisting elements in the lateral load subsystem in order to reduce the overall structural premium for resisting lateral loads.

Some degree of independence can be distinguished between the floor framing systems and the lateral load resisting systems but, the integration of these subassemblies into the overall structural scheme is crucial.

Composite Floor Systems Semi Rigid Frame up to 15 stories, Rigid Frame up to 30 stories, Frame with shear truss up to 45 stories, Frames with shear bend & outrigger trusses up to 55 stories, End channel Framed tube with interior shear trusses up to 60 stories, End channel & framed tube up to 65 stories, Exterior framed tube up to 85 stories, Bundled framed tube up to 105 stories, Exterior diagonalised tube up to 110 stories

Tall building floor structures generally do not differ substantially from those in low-rise buildings; however, there are certain aspects and properties that need to be considered in design:

1. Floor weight to be minimized

2. Floor should be able to resist construction loads during the erection process.

3. Integration of mechanical services (such as ducts and pipes) in the floor zone.

4. Fire resistance of the floor system.

5. Buildability or constructability of structures.

6. Long spanning capability.

Modern office buildings require large floor spans in order to create greater space flexibility for the accommodation of a greater variety of tenant floor plans. For tall building design, it is necessary to reduce the weight of the floors so as to reduce the size of columns and foundations and thus, permit the use of larger space. Floors are required to resist vertical loads and they are usually supported by secondary beams. The spacing of the supporting beams must be compatible with the resistance of the floor slabs.

The floor systems can be made worth buildable or worth constructable by using prefabricated or precast elements of steel and reinforced concrete in various combinations. Floor slabs can be precast concrete slab, in situ concrete slab or composite slabs with metal decking. Typical precast slabs are 4 to 7m, thus avoiding the need of secondary beams. For composite slabs metal deck spans ranging from 2 to 7 m may be used depending on the depth and shape of the deck profile. However, the permissible spans for steel decking are influenced by the method of construction in particular, it depends on whether or not, shoring is provided. Shoring is best avoided as the speed of construction is otherwise, diminished for the construction of tall buildings.

Sometimes openings in the webs of beams are required to permit passage of horizontal services, such as pipes (for water and gas), cables (for electricity and tele and electronic communication), ducts (air-conditioning), etc.

In addition to strength, floor spanning systems must provide adequate stiffness to avoid large deflections due to live load which could lead to damage of plaster and slab finishers. Where the deflection limit is too severe, pre-cambering with an appropriate initial deformation equal and opposite to that due to the permanent loads can be employed to offset part of the deflection. In steel construction, steel members can be partially or fully encased in concrete for fire protection. For longer periods of fire resistance, additional reinforcement bars may be required.

Back Structural Analysis: Gravity and Lateral Loading.

Fundamental Principles

Structural analysis is the determination of forces and deformations of the structure due to applied loads. It involves volumes of calculations based on various theories of analysis formulas.

Structural design involves the arrangement and proportioning of structures and their components in such a way that the assembled structure is capable of supporting the designed loads within the allowable defined limit states. Analytical model is an idealization of the actual structure. The structural model should relate the actual behavior to material properties, structural details, loading and boundary conditions as accurately as is practicable. In addition, constructability based on designs plays a significant role.

All structures that occur in practice are three-dimensional. For building structures that have regular layout and are rectangular in shape, it is possible to idealize them into two dimensional frames arranged in orthogonal directions.

Joints in a structure are those points where two or more members are connected.

A truss is a structural system consisting of members that are designed to resist only axial forces.

Axially loaded members are assumed to be pin-connected at their ends.

A structural system in which joints are capable of transferring end moments is called a frame. Members in this system are assumed to be capable of resisting bending moment axial force and shear force. A structure is said to be two dimensional or planar if, all the members lie in the same plane.

Beams are those members that are subjected to bending or flexure. They are usually thought of as being in horizontal positions and loaded with vertical forces.

Ties are members that are subjected to axial tension only, while struts (columns or posts) are members subjected to axial compression only.

Structure formation mechanism should be intuitively conceived considering the possible deflections in all three dimensions. Trial parameters should be used for obtaining various modeling results. Moderation of structure should be conducted prior to making various analysis decisions for economizing as well as optimally producing a sound, safe & adequate structure. What software or formulae are to be used, is the discretion of the designer. Real purpose of analysis is that all possible lifetime imposable forces should be covered in considerations giving no opportunity to the structure to talk different language or behave differently than conceived. Structure should be compatible to allow variation of use within certain flexible limits keeping in view the volume & the cost of building. Contemporary fashion to be infused into the structure nowadays, is good RCC framing, good shear wall based framing, stronger & flexible foundations with good degree of rigidity, energy dissipation techniques etc. Micro piling, piling, shear keys, structural fills, engineering fills, general fills, sand fills, concrete protections & many others which require equal considerations while analyzing various aspects of the structure.

Back Structural Design and Ductile Detailing.

Ductility: Capability of a material or structural member to undergo large inelastic deformations without distress; opposite of brittleness; very important material property, especially for earthquake-resistant design; steel is naturally ductile, concrete is brittle but it can be made ductile, if well confined. Ductility takes material into plastic or inelastic stage for allowing it additional deformations without causing structural failures. Forces redistribution is carried out in this stage giving an opportunity to structure for safe collapse stage in stages.

Durability: The ability of concrete to maintain its qualities over long time spans while exposed to weather, freeze-thaw cycles, chemical attack, abrasion, and other service load conditions. Durable concrete does not allow rapid chloride penetrations more than defined value. This property leads to prevention from corrosion to acceptable level if not fully. It also enhances the service life of concrete & other materials.

Ductility & durability are interrelated terms as one is required to achieve the other. Inducing ductility on to the RCC, durability can be achieved to certain extent by virtue of reinforcing confining actions.

It has already been suggested that, to keep the members ductile, compression reinforcement would assist. It is in the interest of the structure to produce ductile even if, the member does not technically require being designed so. Should beam be provided with compression rebars, it shall help beam ductility even though, the beam has to be provided rebars in compression zone for purpose of anchorage & temperature rebars.

Same principle applies to slabs as well as columns. In fact, within slab, compression steel would also act as reducing the possibility of deflection. Rebars would not be required to be cut within the portion of the main part of suspended slabs. There shall be no need place additional bars on the beams portion in slab for anchorage or negative moment. Vertical stirrup spacing may be kept confining to the ductile requirement in case of beams & columns.

Structural design & analysis can be based on any method using any software or by manual means depending on the required quantum of design work. It is also suggested that slab should use smaller dia bars to prevent cracking. Columns should also, not be encouraged by higher size bars. Bars should be tried to be spread on the members’ surfaces.

Due care should be envisaged for the development length, curtailment locations, overlapping considerations & many such required factors. Proper binding should be done in all rebars to keep them fully intact while pouring concrete. Positions of the construction joints if so required, during emergencies, must better be shown on design drawings. Expansion or contraction joints locations must be indicated on the drawings so that, these are taken care of by the field engineers to avoid possible mixing of requirement.

Drawings should clearly state the structural brief specification to facilitate the engineer to understand what should be done on site. In the absence of this information, construction site engineer would execute the work complying to his either right or wrong information jeopardizing the well designed structure. Details should be elaborately indicated in sections in such a fashion that site engineer does the job right first time every time. Least queries raisings designate a drawing good one. If possible, bar bending schedule should be charted out either on detailed drawings or on some other documents to have the right & accurate cut dimensions. Conventional shape coding based BBS should be issued for sites execution.

Constructability concerns should be minded while deciding reinforcement within sections of all members. All possible steel congestion must be avoided. Practical aspects must be minded while detailing to extend ease of construction to the site team & the contractor. Details of required grade of concrete for various locations as well as grade of reinforcement must all be indicated clearly. Where welded prefabricated mesh is to be used, should be clearly mentioned. Totality of project specification must give all information about all requirements. It is suggested that drawings should accompany some set standard sections for the typical items on the project for reducing the volumes of detailing repetitions.

Advisory construction method statements though not binding on contractor or builder, can also be included within the specification to apprise the executor about the project intended requirement. Definitions of all terms as well as procedures, the relevant specifications & codes used, should be indicated. Documents precedence should be clearly indicated to avoid various disputes.

Back Strength & Retrofitting of Structures & Vulnerability Assessment:

State of building construction in Bharat is not good as far as the quality criteria is concerned from every angle. Buildings had been constructed long back & have been being constructed presently but, an overall quality status does not look to be to the required quality mark. Those structures that were meant to serve for say 50 years, do yield earlier than required & signs of distress & disintegration are visible. Some defects had been crept in during construction while, the others were by ill use as well as by adverse weather conditions. There is no gain by criticizing about all these defects but to reinstate or rehabilitate the existing structures to their original state or even to improve the conditions so that, strucyures can serve up to the designed duration that we call specified durability.

Structural Audit: The process that involves first understanding the properties losses that structure has already undergone during its used life by means of testing various materials, by settlement surveys, by core drillings from RCC without involving reinforcement, by checking reinforcement conditions etc. all can be termed as structural audit based on surveys to know the deficiency requirement induced in the structure. If so required, even the load testing can be conducted on the structures to know about better state of facts. Cores shall definitely tell about the concrete quality while building quality shall be provided by load testing. Investigation shall reveal about the new requirement, the structure waits to be rehabilitated for future imposed loads & missing durability. Even, by this investigation, further life can be added to the structural members. All such requirements are referred to the process of rehabilitating & retrofitting the structure.

Retrofitting: It is a slow process which requires high degree of patience & study a lot about the operations & their research. Substructure as well superstructures would require retrofitting. Foundations may require extensions. Additional thickness may be required to be added to foundations. Columns may require jacketing. Beams may require jacketing or substitute arrangement. Resin injection may be required for the distressed areas. Various locations on the concrete surface may require repairs though in patches.

To meet all foregoing requirements, various construction chemicals would be required, the study of which, the retrofitting engineer should do. Retrofitting covers a wide scope & varies from one building to another. In some old buildings, structure may be inserted by any method while semi performing buildings could be reinstated to the requirement as said earlier. Applications of new concrete to the old concrete would be required. Applications of additional reinforcement to be inserted would also be required. Some weak concrete portions shall be required to be extracted out to be replaced by the new one. Various combinations of chemicals shall be made necessary. Materials shall be used based on the recommendations of the chemical supplier or manufacturer as the case may be. Special chemical concrete, micro concrete, bonding agents, chemical anchors, low shrinkage concrete & many others would be studied. Intensive research work shall be put in during investigations. After applying the retrofitting activities, test loads shall be conducted on all rehabilitated elements. Retrofitting cost factor would dominate over making a decision about choosing rebuilding or retrofitting. I think an estimated cost on retrofitting ranging 30 to 40 % of rebuilding cost should lead to retrofitting.

Preferred Cements: Replaced By Silica fume: Very fine non crystalline silica produced in electric arc furnaces as a by-product of the production of metallic silicon and various silicon alloys (also know as condensed silica fume); used as a mineral admixture in concrete. GGBS Ground Granulated Blast Furnace Slag. PFA Pulverised Fly Ash

Back Seismic Risk Management in Action:

Post Earthquake-

1. Well, every seismic calamity is different. Disaster level would require what degree of management is necessary. National Disaster Management authority should function virtually as a proficient body working with full efficiency & not just to show its mere presence.

2. Since concrete involves heavy dead loads, heavy duty cranes & other equipment would be required to remove the broken debris as fast as possible so that some lives could be saved. Various required machines & equipment, mostly operationally necessary, must be stocked some where all times in all vicinities to let those be transported to earthquake effected area immediately after the demand is raised.

3. All safety, health & environment issues considerations must be incorporated for risks mitigation planning or disaster controls bodies. Health authorities must be kept on alerts & be deployed immediately post earthquake occurs. All medicines & required equipment must be made available with the medical authorities. Many pools of doctors should be kept on standby to meet such calamities.

4. An easy access to the disaster management personnel & vehicles should be made available for such disaster management being a success. Specialist personnel must be deployed immediately after the earthquake occurrence.

5. Fire can also break out post earthquake which requires fire tender to operate. Emergency buildings such as hospitals, police offices, civil defense, telecommunications & whatever can serve during such emergencies should be properly designed keeping in view their required service continuity & if revealed deficient during audit, must be on priority basis retrofitted.

6. Standby arrangement for water & powers must be made available to meet these emergencies for certain days or hours till the normal life is reinstated in the area affected by earthquake.

7. All residents of the area susceptible to earthquakes must know how to act during such moments without causing panic.

8. All sequential bye calamities must be well planned to be managed with efficiently. Public should be regularly educated by conducting virtual drills for awareness teaching about how to conduct in case of earthquake.

Pre Earthquake management requires production of seismic resistant buildings according to the defined zonings. The design, construction as well as quality criteria should be complied with come what may. All buildings should be designed & compulsorily, supervised by certified competent engineers well trained in the buildings & other structures specific filed. All required facilities should be made intact for the new settlements. Locations of buildings must be rightly selected so that access & egress for the involved areas are conveniently effected with. High rise buildings must be allowed located off from busy roads & colonies. Tall buildings must be provided with all emergency serving measures as applicable to meet successfully all dangers. Local & central agencies including police as well as army in collaboration with civil defense & general public should be adequately trained by conducting required drills’ management & kept updated.

Back Effect on Natural and Built Environment:

Volcanic eruption, T Sunamis, Landslides, Afthermaths effects.

Buildings collapses, bridges collapses, roads failures, human losses, crops loss, animals loss, serious injuries, fires break out, shocks to occupants, interruption of necessary services, rains additions as calamity, communication loss, transport loss, epidemic & many others, environment pollution, material losses, epidemics, hardships to occupants,

Are the relevant natural as well as built environment ill effects resulted by earthquakes.

Back Reference Example

House Construction On Plot 430 Sector 21 B,

NCR India, Faridabad

Construction Synopsis

Construction commenced 12.11.2008

Structure completed 9.7.2009

Please refer to the plates from 1 to 26 giving entire views of the structural construction.

Cost on RCC 500 rupees per square foot

Figures 1 to 8 below give certain details for your reference.

Purpose of this file is an exclusive information exchange.

[pic]

Figure 1

Plot Size 420 sqm

Basement below drawing room hall portion

Ground coverage 55 %

Total coverage added 540 sqm

[pic]

Figure 2

Salient features of construction carried out:

1 Front portion double height drawing room or hall

2 Rear portion Bed Room area in three storeys

3 Ground floor portion 75 sqm previously constructed in 2000

4 Soil Silty Clay with high affinity to water & white ants.

5 Depth of formation level (-3.4 m) for basement.

6 Excavation carried out by JCB partly & then used donkey stock for a total excavation quantity of 550 cum. Soil removed from the site.

Soil improvement below formation level as defined below:

1 Soil improvement by filling 40 mm size graded aggregate 250 mm thick, followed by placing 10 mm graded aggregate & then on that placed graded machine dust. Above mix compacted dry as well as wet to densify the placed mix material for both to enhance the bearing capacity & to reduce the settlement.

2 I had observed one pit 1 m x 1 m x 2 M deep for about six months. There was no problem in excavation & there was no need of any shoring during excavation that indicates that the soil was self supporting due to having no angle of internal friction but due to possessing high value of cohesion. The substrata did not have any water table but, certain moisture content % very nominal. It appears that the land was used for the purpose of agriculture in the long past & for the development of the area, the development authority acquired the land for urbanisation around Delhi. The soil definitely contained certain organic chemicals that had to be avoided to impart adverse affect to the building.

3 I judged the SBC of the soil to be somewhere 5 to 10 T/sqm based on my experience yet, it did not meet the building requirement due to unforeseen behaviour of Clays that could have contended minerals like Montmorillonite or illonite or some others, that could help the soil to swell while being in contact with water or loosen the entire shear resistance. The proposal was to include one equal size basement that caused me a cause of concern. I had decided to avoid the formation of the foundations on existing soil even at cost of additional expenses.

4 Fortunately, I have experienced during my career extensively on the RCC building projects as well on the industrial on shore projects both, in office engineering as well as field engineering. Based on my experience earning, I could solve the proposal easily which I did comfortably with full confidence successfully. A decision was made to apply soil improvement technique in the easiest way so that the bearing capacity as well as the permeability of the soil below the formation is sustainable. The water should not effect the foundation if it is allowed to move beneath the foundation structures. Clay soil had to be isolated from the building substructures for the purpose of RCC protection.

5 To meet the requirement, I decided to form a road type structure below the foundation formation without involving any cementing material but to be included just water bound. Some person suggested to use lime also, but it did not convince me as the lime is not a reliable material in moist environment. I went ahead to excavate about 300 mm additional depth to accommodate proposed soil improvement to a minimal meeting. It could be more thick but, I did not intend to take risk more than that due to excessive depth of excavation where on two sides, existing building up to three storey are located.

6 The formation was prepared & 40m size aggregate which is called Vapisi in Delhi term, was used to be placed first. 10 mm size aggregate was placed on the 40 mm size layer so that the voids within the 40 mm size aggregate be filled with 10 mm size aggregates. Later, the additional layer of machine graded dust was placed so that the voids within the 10 mm size aggregate be filled with the mechanically produced dust. All laid dry mix was watered & compacted just as it is done on a water bound macadem road structure formation. I noticed after compaction that the formation was very strong & there was much improvement on the SBC.

7 The foregoing fill has to respond to work as a permeable medium also for the down flowing water as well as to allow a break for the upward flowing water in future that could be a result of heavy rains or by whatsoever reason. This provision has also affected as a barricade for the clay soil to be in contact with the foundations.

8 In addition to the above, on the sides of the fixed retaining RCC walls built between the main columns, the fill material used is river sand so that it allows water to permeability since the clay does not possess this property but considerable porosity. Virtually, the foundations built are soil contact free & the portions between all the RCC beams foundations joining the columns in both directions, an exclusively river sand was used as a filling material to avoid cumbersome work on compaction of the soils either to be taken from site or to be imported.

9 I think the work has been done economically in all respects inducing to the foundation what it necessitated from practical engineering construction viewpoints.

Structural:

1 On the prepared soil improvement base, a 50 mm thick layer of blinding concrete was laid.

2 The surface of the blinding concrete waterproofed using CICO Tapecrete coating protected by plastering on the coating.

3 Analysis of the structures done using Kani’s Rotation Contribution Method, a very old method of moment distribution but yet, useful.

4 Analysis of the foundation framed matting done by purpose made worksheets.

5 The sketch shows the details of the foundation section 400 x 1200 mm beam with 800 wide spreader, embedded in full 200 mm thick RCC matting under all the beams in both directions. Columns were revealed from the beams. One 16000 litres capacity water storage tank has also been provided between the foundation beams.

6 Between the beams, river sand filling provided in place of soil.

7 Externally, 450 mm wide portion filled with river sand while remaining soil butts with the 450 mm line. There is allowed no contact between the soil & the foundations anywhere.

[pic]

Figure 3

8 Retaining walls 200 mm thick provided around the foundations to hold the fill. The wall reinforced with 8 mm rebars @ 200 centres both ways.

9 Main hall portion allowed 12 columns. 1000 x 400 mm 4 columns while 600 x 400 mm 8 columns.

10 Span between the columns 11 m in two frames while 8 m in three frames.

11 Certain frames are located in the double height area.

12 Front allows 1800 mm wide balconies while sides 1000 mm.

13 Six beams provided in the front balconies at both levels.

14 Main beams permitted 300 mm x 600 mm section for stability resolution.

15 Cross beams included 200 x 300 mm section.

16 Stair waste provided 200 mm thick with rebar meshing in top & bottom layers.

17 All suspended slabs included with 8 mm rebars @ 200 mm centres both top & bottom.

18 ear bed rooms’ portion constructed with 11 columns 300 mm x 450 mm sections for spans do not exceed 5m.

19 A quantity of 250 cum RCC constructed using M 30/25.

All site mixing done.

20 Form support systems employed using rented props.

21 Form material employed 12 mm thick ply & timber scantlings/battens 50 mm x 75 mm & 50 mm x 100 mm.

22 A total quantity of rebars used 22000 kg.

Up to ground level 8000 kg & above ground 14000 kg.

23 Labour contractor did not include curing element consequently I had to do this part myself. I did not find any problem for the suspended slab curing but for the columns & brick walls, I faced the hard job.

24 Though the proposed use of the building is for the residential purpose as per local authority, yet the visitors put the building not as residential in look but either commercial or any office.

Observations:

1 I tried all efforts to extract a good quality of the structure from the workers used to system in NCR but, I was successful to certain extent only. It necessitates a lot of training to be imparted with the skilled workers as well as the self styled contractors & foreman. Most significant part that requires training is about what should be real procedures of producing, transporting & placing concrete mix within right defined duration. QA system is slackening on the use of structural concrete. Generally, RMC suppliers think that cube results only dominate the concrete. There is no call in Bharat India to mandatory drill cores post concreting to ensure the accuracy or genuine sampling of cubes.

2 Concrete pouring gangs do work efficiently but, compliance with the requirement raises a question mark on various projects. Absence of qualified engineers on the supervision also raises eyebrows. Public seems to be ignorant & non serious about the required quality of good concrete & very few understand the durability of concrete as a basic property. What is seen by eyes is considered building work but, real technological requirements do not reach the builder or the general public. Promoters or builders befool the consumers in the name of international standards & make profits from innocent buyers.

[pic]

Figure 4[pic]

Figure 5[pic]

Figure 6[pic]

Figure 7[pic]

Figure 8[pic]

Quality Systems: Lessons Learnt & Conclusions

Quality Requirement is More Significant than Quality Awareness. Quality requirement must be binding leaving chalta he or quality last attitude written off for ever to be replaced by thik karo or quality must attitude.

➢ Quality Systems Requirement must be adherently applied from Designs to Tendering to Award to Supervision to Execution of Construction Operations as well as post construction maintenance.

➢ Merely, signing off documents is not sufficient but, carrying out of activities & cent per cent inspections or examinations are mandatory. Those personnel involved with quality system operations, must be themselves quality competent as well as quality supportive & must campaign for its realty achievement by encouraging other department’s personnel. Responsibility ignoring personnel spoil whole system quality.

➢ Lapse on quality cannot be digested in any case whether activity belongs to pre earthquake preventive measures or belongs to a post earthquake disaster management. Loss of lives due to negligence cannot be compromised. Generally, it has been experienced in almost all spheres that after quality system introduction for decades, products quality has not resulted as expected consequently by the inefficient compliance of quality system.

➢ Lapse of quality on performance & its inefficiency cannot be allowed to be digested with any disaster mitigation scenario whether, it has to be in operation or it has to be as supporting resources or as involving leading authorities whosoever & howsoever big one may be. Hard work input, determination, dedication, commitment, implementation, post implementation scrutiny or audits, are all a must & must be seen duly performing in addition to approved or recognized agreements. Bare talks & statements would not work to give required results. Real action must be seen doing by one & by all members of all departments teams.

➢ No leniency should be accepted on doing any activity to the requirement in any department or section. Safety first & Quality must attitude must be adopted as a strong potential slogan. Since world has been changing then Bharat / India has to change otherwise, there would be no way to escape from due responsibility & legal liability.

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Thanks a Lot Indeed for your Patience & Kind Attention. Sorry for boring you by long descriptive contents.

P Eng Suraj Singh

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May we browse following links?

Various Engineers Responsibilities Role of Site Engineer Based

Training Talks Training Brief (Extracts)

Government Involvement Brainstorming Slides

Earthquake Risk Management EQ Management Initiatives

Building a Techno Legal Regime For Safer Bharat / India

knowledge-manageme Knowledge Portal

Engineers Updating EQ National Programme

National Disaster Management Authority Body

..\NDM\Simplified Guideline_Zone III.pdf EQ Provisions

..\NDM\Simplified Guideline_Zone IV.pdf EQ Provisions

..\NDM\Simplified Guideline_Zone V.pdf EQ Provisions

Browsing Certain Chapters Of Designs CRC Press Publication

..\CRC Press - Structural Engineering Handbook 1999-3.pdf

..\CRC Press - Structural Engineering Handbook 1999-4.pdf

Browsing Soils Reports Gulf Reports Examples

..\Soil Reports\rgxls001311001_a_02_final report (1 of 3).pdf

..\Soil Reports\rgxls001311001_a_03_final report (2 of 3).pdf

..\Soil Reports\rgxls001311001_a_04_final report (3 of 3).pdf

Slab Saved Gulf Real Case Study

Thanks a Lot Indeed for your Patience & Kind Attention

P Eng Suraj Singh

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