Construction Term Papers - Structural Failures During Constructions

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Most prominent structural collapses in the world have occurred under calamitous conditions such as major earthquakes, floods, hurricanes and tornadoes. Others from time to time collapses occur during construction, under heavy snow loads, during thunderstorms, or, more often, as a result of faulty design or manufacture. Many structural failures had been associated with innovation and inability to appreciate the significance of causes of failure. Well-known collapses include the Tay Bridge (1879), which collapsed because it had not been planned to bear the wind load, the Tacoma Narrows Bridge (1940) was destroyed by wind created tremor and the Ronan Point Tower Block (1968) broke up after a gas explosion due to lack of structural stability. Following each failure, reviews and changes are made in the engineering methods to stop recurrence and the faulty methods that were new and had become common. After years of protected structure construction, there is yet another technological development followed by other structural failures. [Peter Carr]

Causes and Types Of The Failure
The temporary structures generally fail due to many reasons. The main causes of collapses include: -

• Excessive Load
It was generally considered that it is very difficult to prevent the catastrophic effect of large seismic activity, storms, cyclones or floods, and they were commonly considered as acts of divinity. It is at the present known that deaths or injuries resulting from catastrophic events can be reduced radically by an appropriate design and proper construction. A reasonably relentless tremor kills hundreds and thousands of people in the world are mainly because buildings are of weak construction. Even with an appropriate design, a really severe overload or unusual load such as an explosion or crashing aeroplane will undoubtedly damage the structure. Nonetheless, this danger can be kept little in contrast with other risks that are faced every day.

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• Inadequate awareness
Many structural failures have been the consequence of poor technical research and knowledge. Insufficient knowledge of the strength of latticed columns was the chief reason of the failure of Quebec Bridge. Lack of knows how of aerodynamic instability was the cause of the collapse of the Tacoma Narrows suspension bridge. In some of the cases strict construction rules have also been partly to be blamed. The collapse of the Ferry bridge-cooling towers in England during high winds was basically recognized to be the result of strict application of allowable stress design, which normally does not provide sufficient safety in cases of stress reversal, for instance, where wind load tension overcomes dead load compression.

• Fault in design
As technical awareness gets better, errors are becoming by far the major cause of known structural collapses, mainly in technologically advanced countries. An error in this situation is a gross error or mistake, not a negligible computation error or construction divergence. Individuals, designers, manufacturers, builders or authorities accountable for examination of a design or inspecting a construction, make the errors. In the majority of the cases not one but a number of errors have contributed to failure sand even collapse. Usually more than one individual has some liability since checking and communication are necessary features of design and construction. Building can fail or do poorly because of bad design, detailing errors, wrong construction methods, inferior building materials, lack of necessary tests or proper construction supervision or a combination of these factors. Overloading, illegal additions and changes to existing building structures and neglect of building maintenance after the occupation of building, could also be considered as causes of building failures. Design errors could happen in the supposition on loadings and structure boundary conditions. Insufficient or flawed drawing details could show the way to structures being built not in harmony with the designer’s plans and requirements. Additional errors include inadequate deliberation of secondary stresses and poorly designed connections between structural members. The likelihood of a design error that leads to building failure is remote bearing in mind the safety factors and the quality control measures used in the design procedure. Yet the risk still exists as in the case of the collapse of the structures.

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• Inappropriate construction techniques
Inadequate design for temporary structures, and contractor’s failure to build in accordance with drawings and specifications can also add to failure of structures. Use of inferior or sub-standard building materials is another probable reason of building failures. Overloading during the life span of building can critically weaken the structural reliability of the building. Extra loads due to unauthorized change of use or additions and alterations to the structure can intensify an under- designed building and can contribute to its eventual failure.

• Maintenance
Overlooking maintenance of building can also be a cause of the structural failure. Signs of structural distress, persistent cracks in columns and beams, excessive settlement or deflections, should be immediately noticed, identified and rectified early to avoid the failure of the building. The protection of structures requires special care from both engineers and builders against lack of control and professional expertise. Failures can also occur after occupancy of a facility as the result of owner/operator errors. These may include alterations made to the structure, change in use, negligent overloading and inadequate maintenance. Not all maintenance-related failures are the fault of the owners and operators of facilities, however. Designers and constructors share the responsibility for durability of constructed projects, through appropriate selection of materials, detailing for ease of maintenance and quality of construction.

• Defective Site Selection And Site Development Mistakes
Failures often also result from wrong land utilization or site selection choices. Certain sites are more susceptible to failure. The most understandable instances are sites located in area of noteworthy seismic activity, in coastal regions, or in flood plains. Other locations pose problems related to explicit soil conditions such as expansive soils or permafrost in cold areas. Identification of the characteristics of particular site conditions, through suitable geo technical studies, can guide to decisions about site selection and site progress that reduce the risk of failure. Unnecessary exposure to natural hazards is a regrettable result of historic example of human settlement.

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• Performance failures
Failure can be described as an intolerable difference between anticipated and existing presented presentation. The designer must unmistakably understand the requirement of the user and they must be practical. When the structure does not perform as estimated, even if the expectations are idealistic or attainable inside given economic restraints, the same is likely tube defined as the project as a failure. A substantial quantity of construction litigation results from uncertain or unrealistic expectations. This type of failure can be kept away through communication during the programming phase of a structure. A program should evidently define the extent and intent of a structure at the beginning, so that common conformity can be arrived at on assessing the success of the structure.

• Blueprint fault
These causes of structural failures comprise errors in idea, lack of structural redundancy, failure to consider a load or combination of loads and lacking correlation information. Also include the estimation errors, wrong use of the computer software and detailed problems containing choice of mismatched materials or assemblies, which are, not construct able. Some more causes are the failure to consider safeguarding requirements and toughness and insufficient or conflicting specifications for materials or anticipated quality of work and uncertain communication of design intention. Such errors ultimately lead to a situation which may involve such failures which are related to excavation and equipment, inappropriate sequencing, not enough temporary support; unnecessary structure weight; untimely taking away of shoring or formwork; and non conformance to design objectives.

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• Material
Most of the structural failures are associated with materials and are the consequence of human blunder involving a lack of knows how about materials or the combination of contrary materials. There are structural failures that can be endorsed to irregularity in materials. Although too much reliance is given on modern structural materials yet the manufacturing or production faults may exist even in the most dependable structural materials, such as standard structural steel or centrally blended concrete. Stone frontage sheets or glass curtain walls may have hidden serious faults.

Prevention of Failures
Having identified the possible causes of building failures, it is vital to find out that how these structural failures can be avoided for the future. The primary step in the avoidance of building failures is to develop a program for educating the engineers on the lessons learnt from past failures. It is not advisable that a mistake once committed and affected is repeated. The engineers, particularly the less experienced ones should be fully conscious of past lessons and make every effort to keep away from such mistakes. The senior engineers should convey the skills and experience to the junior and less experienced engineers and they should oversee personally the inexperienced engineers to get rid of any possibility of errors.

Another way is to make sure that structural designers have an appropriate understanding of the behavior of the structures under design. It is already a custom now for engineers to use computer to analyze and design structures. However, a designer must be able to make use of his engineering principle acquired through years of university training and skill and recognize fully the structural behavior under loads and external forces rather than leaving all the tasks to the computer. An engineer should be able to envisage the deflect shape of the structure under the loads. The engineer should be conscious of the critical areas of stress concentration and the major structural members should be correctly designed to resist such stresses.
A check system must be utilized to assess and check the integrity of structures based on the professional engineer's design and to give independent design results to ascertain the sufficiency of the major structural rudiments of the buildings.

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The recognized check should therefore give particular concentration to unusual design and unusual design details. The inspector and checker should concentrate on significant areas such as transfer beams and columns, and the center of attention be kept on areas where errors are critical and frequent.
Contractors must also have severe control of site operations and quality control. Site staff requires being well qualified and competent and correctly trained in the trade in which they are working to make sure good workmanship and high quality of building works. Independent inspections by professional engineers or his competent site supervisors are essential to make sure that the building is constructed in accordance with approved plans and specifications. Proper maintenance of building structure is also necessary in the prevention of building failures. The neglect of building maintenance may allow and cause some minor structural defects to develop into potential failures. Building defects should be recognized and rectified as early as possible.

Professionalism
It is of extreme significance for building professionals, including builders, to understand that the design process does not stop at the conclusion of design drawings and specifications. The professional engineer’s design aim must go after in the construction stage as well in order that the structure is effectively constructed. A sufficiently designed structure is not only safe, but also serviceable. It should not be subjected to undue bends, twists and corrosion. Increased antagonism during construction bidding by the builders joined with developers’ trend for profit making can place intense pressure and demand on the engineers to create the most inexpensive and efficient design. However, this should not be the end result in any compromise in the safety standard. The building experts have a great liability to make certain the safety of the buildings and infrastructures exists to the maximum.

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The construction team should normally work with a range of professional establishments and associations to improve the professionalism and raise the level of cross-discipline knowledge in the structural building. A system of obligatory continuing professional development should be adopted to ensure that the professional engineers and architects keep abreast of developments in their individual fields. Other professional groups, such as the contractors, developers and project managers, if do not have a code of conduct, should draw up their own code of conduct and satisfactory practices. This is to ensure that all people within the industry of construction attain a high standard of professionalism. With higher professionalism, the industry of construction can be given greater scope to self-regulate. [Tan Siong Leng]

Conclusion
Most of the structural failures have occurred in the world due to such faults, which are controllable. A good operational planning and detailed deliberations and brainstorming can save the failures of the temporary structures. The well-designed structures coupled with the hard effort of the experts with correct material can ensure the structures a complete success.
 

 

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