Framed Structure Multistorey Buildings | Construction Of Tall Buildings In Civil Engineering

Asif Nawaz
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HISTORY OF TALL BUILDINGS

The evolution of first dwelling was simply a natural made cave as the evolution progressed it led to the construction of the first roof structures with Timber and stone the construction by civilizations such as the greeks the Romans Egypt and Indus Valley were primarily of low rise natural limited by the technology of the arch and the dome.

Tall Buildings

It was not until the late 19th century that new technology of materials and vertical transportation justified only by high socio economic pressure of of urban growth, opened the way to the the surge of tall buildings. there have been tall buildings in most cultures since buildings have been erected. the Great Pyramid of Giza for 63 feet.

There have been tall buildings in most cultures since buildings have been erected. The great pyramid of Giza 463 ft. high, remained the tallest man made-structure for about 4,500 years until 1880, when the Gothic spire of the Cologne cathedral in Germany was finished.

The modern history of the tall buildings began with the introduction of wrought and cast-iron into building construction at the end of the 18th century. New York was the scene of the first widespread use of elevators. High speed elevators, reliable foundations, and heating and ventilation systems led to the high rise office and residential structures of the early to mid. 20th century. 

In 1856, New York city's Houghwout Building was the first commercial structure to install the elevator system developed by Elisha Graves Otis. Elevators made all floors of a building equally accessible to the public.

This led to the evolution of the ten-storey "elevator building''-the first tall structure whose plan, use and structure were determined by mechanical installation.

Reinforced concrete began to be introduced as a Common material in frame construction in the 1960s. Today, the potential of new building methods, such as space frame technology and composite construction is only now being realized, and may change the shape of tomorrow's buildings. 

Novel approaches to load bearing began to appear in the 1950s and 60s. A tubular frame was used in the concrete Brunswick Building in Chicago in 1966. The most recent development in structural systems for high-rise construction is the space frame, an idea originally developed for airplane hangers in the 1940s. 

The first building to use this type of structure is the Bank of China Building, now under construction in Hong Kong. It uses half the steel that would be required in a more conventional design and may represent the first of a new generation of buildings.

Tall Buildings

Large-scale industrialization and prohibitive land cost in India have resulted in a vast expansion in the building programme. A stage has reached when multi-storeyed construction is becoming essential and inevitable. 

A common concept of multi-storey building in India is a building having over five or six stories. So far, most of the tall buildings in India have five to twelve stories. Of late buildings as high as 20 to 25 stories have been built or are under construction in the metropolitan cities like Kolkata, Delhi, Bombay and Chennai.


ADVANTAGES OF TALL BUILDINGS

Land-use economy is achieved by construction of multi-storeyed buildings which results in large building getting concentrated on relatively small built up area. This makes available a large proportion of open space for creating natural environments. This also ensures better day-lighting and greater airflow as well as freedom from street noise. Living and working in such buildings provides panoramic view of the city.


PROBLEMS OF TALL BUILDINGS

The construction of multi-storeyed building poses the following common problems:

1. The density of population goes out of control.

2. Prevention of congestion.

3. The uninhibited flow of traffic and minimization of traffic hazards.

4. Parking difficulties.

5. Prevention of excessive and imbalanced load on municipal services like water supply, sewerage, electricity, prevention of accidental fire hazards and earthquake disasters, etc.

6. High rise residential buildings pose a number of social and human problems. These arise out of the indigenous conditions of living as regards climate, social and economic background of population and the extent of general develop ment in science and technology.


DESIGN OF TALL BUILDINGS

The design of tall buildings is dominated by resistance to horizontal forces. In addition to structural safety, sway limitations must be satisfied in terms of horizontal acceleration as well as actual movements. 

In low to medium-rise buildings, the structural system is designed primarily to resist the vertical loads and is then checked for lateral forces which may be taken by movement resisting frame action, braced frames or shear walls conveniently located around lift shafts or stair walls.

Simple shear walls provide the necessary horizontal restraint for 'pin-jointed' frameworks which are often convenient and economical. Thus, the lateral resistance may be provided by frames in bending, braced frames or by shear walls, as in lower structure, but the greater magnitude of the forces and movements necessitates a more sophisticated approach. 

The advancement in the knowledge of bearing capacity of soils and foundation engineering has been mainly responsible for the trends towards construction of taller and heavier buildings. 

The advances made in the designing of structural framework to withstand heavy loads, and to resist wind pressures and earthquake shocks have led to the construction of very tall, economical and efficient buildings.

Damping systems or active control systems are becoming more common place as we design our tallest buildings. None of the available systems are reliable enough to be counted upon fully in the strength design of buildings, but all can make buildings more livable. 

The most promising systems are viscoelastic damping, active tuned mass dampers , and possibly , active pulse control . The ideal damping system should be economical to install , durable , maintenance - free , requiring little space , having low operating expenses , and be effective and reliable at all levels of building dynamic response . Viscoelastic dampers were installed at New York's World Trade Centre in the late 1960s . 

Tall Buildings

Research is in progress to develop a highly damped permanent partition wall system in core areas for the full building height that could also serves fire rated enclosures . 

Another research possibility is in the development of a material that would significantly increase building damping and at the same time evolve fire proof structural steel members . Such a material could be " glued " or " sprayed " to all primary structural members . 

The present state of the art is such that we canact accurately estimate structural damping closer than plus or minus 30 % until a building is fully const ructed . We do know that wind - induced building response is inversely proportional to the sque root of total damping , aeronynamic plus structural damping . 

So if we double the structural damping we reduce dynamic response by 29 % , if we quadruple damping we achieve a 50 % response reduction . Most tall buildings have structural damping between 0.5 % and 1.5 % . 

However , we do not have reliable and effective methods of increasing damping by factors of two or more Recent research results show that buildings under 20 stories tend to have roughly 60 % more damping than taller buildings , taller concrete buildings bend to have roughly 30 % more damping than steel structures , and damping increases with amplitude to the power of 0.1 , with a high coefficient of varia tion , to the order of 0.4 . 

Planning and layout of tall multi - storey buildings require special attention in terms of orientation of buildings , with respect to prevailing wind direction and sun rays , provision of adequate open space for gardens and lawns around the building , suitable arrangements for parking , traffic and drainage. 

In India some of the special requirements respect have already been covered by the local by - laws although no special by - laws exclusively for multi - storeyed and tall buildings have been brought out so far . The general trend in India for planning the space requirements is as below : 

Total built up area (plint area)-------- 30 to 40% of land area

Carpet area, i.e., available for-------- 55 to 66% of plinth occupation area

External walls and columns----------- 4 to 6% of plinth area

External walls and partitions---------- 3 to 7% of plinth area

Area of horizontal circulation---------- 12 to 16% of plinth area

Entrance halls and lobbies------------- 2 to 4% of plinth area

Windows                      --------------- 9 to 12% of plinth area

Area of vertical circulation consisting of lifts and staircases ---------- 6 to 8% of plinth area

Area of toilets-------------2 to 4% of plint area.


Trends in Building Design for Maintainability 

Aesthetics , economic consideraons , the use of new materials or old materials in new applications , and changing building uses are significant factors in building design and construction . Decisions regarding trade - offs between durability , serviceability , safety and economy are inevitable . 

The designer and the builder make choices bet ween no maintenance , low maintenance , passive or active systems . This decision has to be made with current cost in mind and the possible consequences of the failure to maintain the structure in accordance with designer intent . 

A passive , maintenance - free system includes ele ments whose performance throughout the design life of the structure is assured by the selection of materials and details of construction . No inspection or maintenance is required after construction of passive systems such as most foundations and monolithic concrete structures . 

Buildings and other structures are usually passive in operation , but require some maintenance either by design ar default - throughout their life to continue a satisfactory performance . Painting of wood and steel structures , periodic routine repairs . Active systems need active maintenance , especially in adverse environments . 

The level of maintenance that can be reasonably expected depends on the structure's anticipated use , owner awareness of the importance of a maintenance program and the consequences of neglected maintenance . 

Proper upkeep of such a system depends on owner's sophistication . Where the maintenance and repair of an active system are not feasible , the degree of reliability required - and hence the cost - will have to be high . 

An alternative to active systems and periodic maintenance is to design passive systems requiring little or no maintenance . Since inspection and maintenance of reinforcing steel is often impractical , the use of epoxy - coated rebar and well designed concrete mixes provides a virtually maintenance - free option . 

Lack of timely maintenance may result in extensive concealed damage or complete failure . The actual rate of deterioration in a particular structure is uncertain . The purpose of an inspection pro gram is to assess this rate and determine the necessity and timing of expected maintenance . 

Many seemingly well - designed and constructed . buildings are developing serious problems as a result of inadequate or improper maintenance . Detailed inspection and maintenance guidelines could prevent such incidents . 

The sophistication and scope of these instructions may vary according to a structure's size , type , complexity and owner's sophistication . 

A well - designed and enforceable long - term maintenance program could pay for itself by increasing the likelihood of early discovery of unexpected deterioration and ensuring that required mainten ance is provided . 

Since these costs are operational expenses , building reliability can be increased . without raising design and construction costs . 


CONCEPT OF A FRAMED STRUCTURE

Framed structures are comprised of series of frames. These frames are formed of columns which are connected by means of beams at floor and roof levels. 

Within these frames , walls are constructed . A wall is a member whose length and height are larger than the thickness . Walls subjected to vertical loads are called bearing walls . Walls subjected to no loads other than their own weight , such as panel or enclosure walls , are called non bearing walls.

RCC framed structure

Walls with a primary function of resisting horizontal loads are called shear walls . In case of framed structures , the loads of floors roofs and panel walls are supported by the beams which i transmit these loads to the columns . 

Light framed structures are constructed of mate rials like wood , steel and R.C.C. On the other hand . 



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