CAUSES OF STRUCTURAL FAILURE, THE WAY FORWORD
CHAPTER ONE
INTRODUCTION
Structures are building which serve as shelter for man, his properties and activities. They are expected to be properly planned, designed and erected to obtain desired satisfaction from the environment.
Structures in general serve many purposes including provision of shelter for man, protecting properties, and other activities.
With these purposes that structures provide, there is always the need to properly plan, design and construct them to obtain the expected satisfaction from the environment and prevent structures from failing. Failure of structure is the worst form of structural failure and building professionals see it as a structural failure of a higher magnitude.
Every structures can fail but multi-storey structures are more prone to failure of a higher magnitude. Multi-storey structures may fail when there is structural failure.
Structural failure may be unique with every structure such as building and bridges. However, the reasons why a structure will fail could generally be attributed to either natural or man-made infrastructural disasters.
For natural disasters such as typhoons, cyclones, tsunamis, earthquakes and many more, Nigeria is blessed as a nation not to be experiencing any of these. The man-made disasters are born out of man’s negligence. Poor structural design and planning contributes significantly to the failure of multi-storey structure. At the design and planning stage, structural professionals, including architects and structural engineers, perform detailed calculations to ensure a sustainable structural integrity of the structure. In cases of wrong calculations from any of the professionals, a multi-storey structure may fail from varying reasons, including excess load exerted on supporting pillars of the structure.
Low strength of mortar, concrete and sandcrete blocks may not be able to withstand dead and live loads that come with multi-storey structures.
It is even worse with commercial sandcret blocks and concrete manufacturers who always want to make outrageous profit at the expense of product quality.
Weak supervision and the use of incompetent contractors may also lead to the failure of multi-storey structures.
The construction stage of a multi-storey structure is the stage that needs effective supervision because of inadequate skills and knowledge among masons.
A good design may fail when clients fail to secure competent professionals to oversee the construction stage.
Most clients are interested in the structural approval stage and not the aftermath. Thus they do away with professionals when approvals are given by authorities.
A contractor who lacks the requisite skills and is very ignorant of construction skills may have a negative impact on either the pre and post construction stage of multi-storey structures.
STATEMENT OF THE PROBLEM
Before proposing the measures that will drastically reduce the frequency of structural failure in Nigeria, I will highlight the basis for obtaining robust structures that resist test of time in contrast to what is obtainable in the Nigeria built environment.
What is Expected for the Realization of Robust Structures
The purpose for any structure of building or bridge is to satisfy some human needs. The design of any such structure must satisfy the functional objectives of safety, serviceability, and economy. The tools to enable the engineer to realize these objectives are his knowledge of structural mechanics, available research materials, government regulations, codes, his experience, and professional knowledge. The structure must be safe under the worst system of loads. Under extreme loadings, damage to the structure can be localized and possible loss of lives reduced, but progressive and catastrophic structures must not occur. Under the working load, the deformation of the structure must not impair the appearance, durability, and performance of the structure.
A structure is assumed to have failed when it can no longer serve the purpose for which it was built. Failures may occur
during construction or later in the course of the design life of the structure. Irrespective of the type of failure or the period
in the lifetime of the structure that the failure occurs, the effects are always devastating.
The possible causes of failure can be traced to the activities that take place in the following stages of a structural process: conception-design stage, construction-supervision stage, and post construction-service stage. For the realization of quality jobs in any of these stages of the structural process, a high level of skill and professionalism is needed (Ayininuola & Olalusi, 2004).
The conception-design stage is the planning and feasibility studies stage in which some professionals may assist the owner to evaluate the technical and economical options available and then realize the design. The design consists of the creation of the architectural form, identification of the loads, selection of materials, and proportioning of the sections.
During this stage, the basic requirements of safety, aesthetic, economy, and constructability must be considered, irrespective of the client’s brief (Davison & Owens, 2003). The structure produced from this design is strictly for the for a certified engineer to redesign the structure for the new loads and make adequate strengthening on the structure where necessary.
The construction stage is the physical realization and over-seeing of the structure designed in the previous stage. During this implementation stage, every effort is made to ensure compliance with the design and specifications. The activities that take place within this stage are so numerous, and often conflicting with each other. The management of scheduling, materials, human and technical resources is often enormous such that only trained professionals can handle them.
Certified engineers, architects, builders, and skilled artisans all have their respective roles in this phase so as to enforce the quality assurance specifications.
During the service stage, the constructed facility serves the purpose for which it was built. It is expected to serve effectively the purpose for which it was built without causing any form of discomfort to the user. For a good usage of any built structures, a management and monitoring team must always be at hand to continuously assess the true state of the structure and make recommendations for maintenance. Visual inspection may be combined with Non-Destructive Testing techniques to assess internal defects and make maintenance meaningful (Ede, 2008). Failure to execute appropriate maintenance may pose a great danger to the structure and the users.
