What Turned Many Apartment Buildings Vulnerable In Bangladesh ?

By:- Prof. Bijon B. Sarma *

ABSTRACT :
In view of tremendous increase of population in scarcity of land, multi-level apartment buildings were accepted as a good solution in the busy cities of Bangladesh. Such buildings usually are constructed with reinforced concrete. At this stage, no one gave deep thought about the fact that "Concrete is an experimental material with many limitation". In the present process of construction, there is no scope for the owners of the apartments to look into the quality of works. It is quite doubtful if the people whose responsibility was to ensure it did their duties. The reasons for expressing such doubt are :

(a) In the democratic country of Bangladesh there is no transparent mode of collection of fund for running the activities of the political parties. It is known to all that "law breakers and privilege enjoyers" supply this fund. For this reason the political government at times introduces various administrative regulations and then allows their violation for obvious reasons. The rules and regulations introduced in connection with design and construction of multi-level apartment buildings also suffered from similar fate.

(b) In a situation where the prospective owners of apartments did not have any scope to look into the quality of works, there was scope for the developers to negotiate with the government’s vigilance team, there is wide possibility that some, if not all, of such buildings were constructed with defects and deficiencies.

This paper would endeavor to show some of the common mistakes and deficiencies. At present a considerable section of affluent people live in multi-level apartment buildings either as owner or rent-payer. Also many non-resident wage earners may feel pleasure to think that that they have "accommodated their old parents" in the "safest place of high-rise apartment building". After knowing the situation of vulnerability of such buildings one may however wonder if those "safest places" are safe or mere "death traps".

INTRODUCTION :
In the contemporary world there exists significant and wide difference in between the building constructed by the owner and a salable apartment building constructed by a developer. The busy cities of populous countries having inadequate land for habitation seems to have accepted the program of accommodating people in multi-ownership apartment building as common and appropriate solution. While all these may be seen as "right solution to the problem", a deeper thought might reveal that in place of making the lives of the inhabitants safe and sound, this solution would in fact endanger those, specially if the country exists in earthquake prone zone.

When an owner goes for the construction of a building he takes utmost care to ensure the stability and durability of the built-form. On the other hand, the developer designs and constructs such a building solely for the purpose of earning profit. In the crudest word, it matters a straw to the developer if the building collapses immediately after the apartments have been handed over. In the developing country there is no government rule to hold the developer responsible for bad construction. Also the loss in good will can be taken care of by opening a new company with another name.

In the field of habitation the architects work for the human society, where as in the building industry the developers or contractors work for profit. When individual owners approached for designing the building, they asked for one that would fulfill the needs and achieve longer life. Now, when the same architects are approached by the developers, they ask for a building that would look nice with no question on its life or durability. Apart from the design of the architects, the developer is free to use low quality materials and can make more profit.

In Dhaka city multi-level apartment buildings are constantly replacing the low-rise independent owning residences. The concept of design (as followed by the architects and design engineers), construction technology (as followed by the contractors) and materials (as made available by the local and international manufacturers) etc. used in constructing buildings are much better then those used and available in earlier days. In such a reality it is natural for one to think that today’s apartment buildings would be much superior in points of safety, life-span, resistance to hazards etc. The reality, however, is with the change in objective from "owning and using" to "selling and earning money" has, in many cases, if not all, worsened durability and life-span of the "salable commodities".

DESIGN AND CONSTRUCTION OF SALABLE COMMODITIES :
The two major fields in which the quality of apartment buildings have worsened IN Dhaka City are : (i) Life span and (ii) Safety. The various design and construction processes on which these two qualities depend upon are (a) Architectural Design, (b) Structural Design inclusive of foundation, (c) Materials used and (d) Supervision and construction method utilized.
The endeavors of the owner of a building usually are the following:

1. Importance on safety and life span : The owner stresses upon the factors like architectural design, structural design, electrical and plumbing design, quality of materials used and supervision because the owner cares for safety, durability and life-span of the building.
   
   
2. Less importance on superficial beauty : In case of financial constraint, the owner goes for inferior quality finish materials and fixtures responsible for superficial beauty. He knows that these can be changed later.
   
   

By all means, the aim and objective of a developer in business of "salable apartments" would be different. These may be :

1. Little or no importance on life-span or safety: The life-span and safety of the building in fact matters nil for the developer in business. The only thing he needs to do is to satisfy the rules and regulations of the urban authorities. To their great fortune, such authorities in Bangladesh do not have consumer-friendly rules and regulations. What is still worse is, many personnel working in these organizations are ‘purchasable by money’. The developer in general believes that there lies profit in each and every violation of RajUK’s regulations.
   
   
2. Extreme importance on factors giving superficial beauty : Since the buyers mostly evaluate the apartment on the basis of its superficial beauty, the developer ensures that through factors like nice-looking finished materials, painting, fixtures etc. The developer in general knows that the better will be the superficial beauty, the more will be the price of the apartment.
   
   
3. The developer also knows that designs by reputed architects, attractive advertisements in the medias etc. can attract the buyers.

The above realities have rendered some, if not all, of the multi-level apartment buildings of Dhaka city quite vulnerable and even ‘death-trap’ during earthquake. The major fields in which these buildings are defective or weak are shown hereunder.

VULNERABILITY DUE TO FAULTY STRUCTURAL DESIGN :
SIZE OF COLUMN : RajUK has prescribed car-parking in the ground floor of the apartment building. This makes the lowest floor a "soft floor" (a floor with less number of walls is known as soft floor), where frequent use of walls in the other floors make those "hard". During earthquake the hard floors en masse act as a rigid body and only the exposed columns are exposed to shivering. In a thumb rule, a reinforced concrete frame-structure building with 6 stories and above needs minimum 20"X20" column in the ‘soft floor" in order to withstand an earth-quake of 3.5 Richter scale, even though a lesser size may be sufficient for bearing the vertical loads. In Dhaka city apartment buildings having columns with less than this size in the "soft floors" are vulnerable to earth quake.

The capacity for bearing vertical load by a column is given by its cross-sectional area. The cross-sectional area of a 20"X20" column is 400 Sq. Inch. Columns with various sizes (like, 10"X40", 15"X27" etc.) may satisfy the condition of bearing vertical load. The designers prefer one side of the column to be 10" since it is advantageous to "flush" the 10" walls with it. Such columns may withstand the earth-quake coming from the direction of its short side. However, apartment buildings having columns with less than 20" on any side in the soft floors are vulnerable to earth-quake coming from the direction of its larger side.

ALIGNMENT OF COLUMN :
As per structural principle of r.c.c frame-structure buildings, the r.c.c. columns need to be placed in regular (not necessarily equal) grid and order. This helps in achieving stability and group-resistance against lateral loads. From whatever direction the vibration due to earthquake may hit a building, it would start swaying only in the two major directions of the rectangular or square plan of the building. It is not difficult to understand that a building can easily resist the vibration coming from its length-wise direction. Even if the designer knows that earthquake would come to his building from a particular direction, in most cases it is not possible to design the building considering this direction only. In order to function well the building must be oriented so as to fit the entrance from the main road, views from inside and outside, climate etc. As for resistance to vibration, a column is stronger in its longer section. However, since it is not possible to orient the columns with respect to any direction, one good solution is to use cross-sectioned columns, where possible. Apartment buildings having columns (i) in less or inadequate number along any length of beam and (ii) not standing in straight lines are weak and vulnerable in point of earth-quake resistance.

CONTINUITY IN BEAM :
Excepting the cantilever ones, all beams should terminate only in columns. It has been observed that in order to facilitate room-divisions many designers place columns at places other than column junctions. Even though such a system can take care of vertical loads, apartment buildings having columns not at the and away from the junction or meeting place of beams are vulnerable to earth-quake.

VULNERABILITY DUE TO LOW QUALITY CONSTRUCTION MATERIALS :
In addition to worthwhile structural design, what contributes most to the life and stability of a building is material. The principle ingredients of reinforced concrete are rod, coarse aggregate and cement. When the owner of a house purchases these items, he endeavors the best materials for obvious reason. But what someone with the objective of earning profit from the "deal" of the consumable item (i.e. the apartments) would purchase from the market are the low quality materials. Unfortunately all varieties of these materials are available in Dhaka city. Thus old rods, brick bats (coarse aggregate) from old buildings, poor quality cement etc. are available in the city. The level of honesty of the people of Bangladesh is not that high. In such a reality it is quite probable that many of the apartment buildings constructed and then sold by the developers are vulnerable to earth-quake simply because of having less strength due to inferior materials.

OTHER REASONS OF VULNERABILITY :
Another important cause of vulnerability of the buildings constructed with best quality materials and sound design has been caused due to inadequate space left around such buildings. In prescribing free/open space in between multi-level buildings what the city authorities (i.e. RajUK) have considered is the space required for running service lines. Naturally multilevel buildings can be constructed by leaving 1 or 2 meter distance in between buildings. In Bangladesh there is good possibility of any building to collapse due to earthquake, structural failure, fire incident etc. and the urban authorities should have prescribed the minimum inter-building open space such that the collapse of one building may not affect the adjacent ones. When buildings are constructed with 1 to 2 meters distance, the sudden collapse of a ill-designed building for whatsoever reason is sure to make the good buildings also to collapse. The case is even worse in case of buildings having flat-plate floor slabs.

IMAGINED SCENE OF DEVASTATION :
Since the earth would not change its habit of contraction, there will be earthquakes. The weaker and old buildings are supposed to collapse due to earth quake. The same may also happen to buildings due to hazards like fire incident or structural fail, specially due to rusting of the reinforcing rods. The city of Dhaka has grown up quickly as per right or wrong decisions of the political government, the various rules and regulations regarding construction of built-form have been prescribed by respective authorities, the developers have constructed the buildings to the best of their honesty and social responsibility. The purchasers of the apartments had little choice, because they did not have any scope to see how the building was constructed and with what type of materials. In such a context we can imagine what may happen in the city in case a severe earthquake hits the city. Thus may be like :
(a) The buildings, specially the high-rise buildings start shivering. In the buildings having all the columns standing on the junctions of regular grid take the jerk equally. In the buildings where some of the columns have been shifted away from the junction points find them helpless, leaving the great task on others. Thus, in a building with say, 5 columns in one a bay, only the few columns standing in one line may contribute to the strength. In case the shiver is sufficient to overpower only this may, there is possibility that the entire building would collapse.

(b) The building having its upper floors furnished with walls in fact act as a solid rectangular mass. When the columns in contact with the ground vibrate, the upper mass tends to remain stationary or move aside due to inertia. In such a situation only the free length (may be 10 feet in case of flat-plate, or 9 feet in case of frame structure) of the columns in the ground floor would try to maintain balance. It is obvious that these would fail unless the sections and reinforcements of the columns are adequate.

(c) During earthquake vibration comes from lateral direction and from below. Buildings with long piles in the ground naturally suffer from more vibrations. In soft clay the piles themselves are subjected to shear failure. Now say, during casting of pile there happened a ‘cave in’ of mud in the reinforcing iron cage. With the passage of time the rods would start rusting. In normal case it may stand in the same position even with rusted rods. But those are supposed to fail due to shivering during earthquake.

(d) Let a 20-storied building fails because of failure in foundation, fracture of the free columns etc. In case it leans to one side, what would happen to the buildings on this side ? Even if it collapses right on its base, should any one expect to see the adjacent building in tact ?

CONCLUSION :
In concluding this article we can mention our finding regarding inappropriateness/ problems of reinforced concrete multi-storied building in Dhaka city under the following subheads :

1. Concrete is an experimental material and should be used with caution: Concrete is an experimental material that has not still attained a life of 100 years. In buildings is attains the requisite strength because of the use of steel, which is used as bars. Irrespective of its strength Steel has got limited life. Its life considerably depends upon its contact with rust-generating materials. Concrete buildings are constructed as a frame with continuity, such that replacement of any element is not possible. Concrete building may fail due to three major reasons : (i) Decay of the reinforcing bars with due to rusting or end of life, (02) Hazards like earthquake, fire etc. Since there is no scope of changing of components, concrete building usually fails in one piece. For this reason, other concrete buildings need to be constructed at safe distance in order avoid "to failure due to impact". One advantage during failure of concrete building is, when the reinforcing bars rust those chip away the covering plaster as ‘peels’. This indication in floors is easily viewable. But in case of external and exposed columns of closely-spaced buildings, it is extremely difficult to identify such defects because of height and proximity of other structures.
   
   
2. Steel bars used in piles in soft soil needs special care.
   
   
3. Safe distance in between high-rise buildings must be maintained in order to avoid failure due to impact created by a collapsing building.

The trend of constructing high-rise residential building initiated in Bangladesh in the seventies. Some of the factors that created this scope were : (i) Extremely high land price in the cities, (ii) Affordability of non-resident wage earners to maintain their families in the city, (iii) Need of such wage earners to get a house as a ‘purchasable item’. (iv) Availability of material and technology for construction multi-level buildings. Even though the purchasers of apartments became the owner, they did not have absolutely any scope to see or know the quality. In such a state, the parties who could guide the quality of such buildings are (i) urban authorities, (ii) the design architects and engineers and (iii) the contractors. We have already shown that none of the above parties exert their duties honestly and efficiently. The evil consequences of this failure will be known in the days ahead. In the second week of February, 2010 we have seen 7 members of a family to have died due to fire incident. We came to know about the deficiency of safety only after their deaths. Probably the other defects associated with such buildings will be known after many deaths. It is probable that the non-resident wage earners working abroad feel pleased to know that they have "accommodated their old parents" in the "safest place of high-rise apartment building". In case such buildings have not been designed with care, those "safest places" might turn to "death traps".

NOTE: Technical (engineering) terms have been avoided in this paper for easy understanding of the readers.

---

* Prof. Bijon B. Sarma contributes to e-pao.net regularly. Prof. Bijon B. Sarma is the Dean, Faculty of Arch. & Planning and Head, Department of Architecture. Ahsanullah University of Science and Technology.
The writer can be contacted at rangada(at)gmail(dot)com
This article was webcasted at e-pao.net on 18th March 2010.

---