Over the years man has accorded priority to his built environment and physical structures as it concern his continuous existence and survival. Nevertheless, maintenance of existing building structures in a standard liveable condition and initiation of new one to safety completion still pose significant challenge (oalgunju 2011). Man built environment can either be temporary or permanent edifices and requires a well layout design and planned measures, well-articulated construction method and process, including a clearly defined intermediate maintenance schedule. This enables the attainment of desired satisfaction, safety, comfort, and safety.
This factor of satisfaction, comfort and safety comes under scrutiny when the structure failed or is unable to carry out its main functions of safety of occupant, and stability of the structures itself (olagunju 2011).
Adesanya (2002) argues that the occurrence of building and structure failure and the ante dent human causality involved, has become alarming and worrisome. A visit to most scenes of failed building structures, the urgency of the issues at stake can be observed. Various preventable and unpreventable factors can be adduced for different cases of building failure and collapse. Adesanya exclaimed that, most factors responsible for this failed building are preventable and asked “Why must a preventable incidence continue to traumatize us over the years”. Incidence such as building failure and collapse have led to question been asked on the effectiveness and efficacy of adopted building method, building professional competency and regulatory policies.
The menace cause has been considered an affront on the capacity and skill proficiency on various country’s construction bodies and societies. This construction bodies includes Architectural institutes and bodies, building and structural engineers’ bodies and institutes, surveyors, urban planner and analyst. These professionals mentioned are considered to be responsible for designing and monitoring construction works (Adesanya, (2002)
Building failure and collapse also arise from other non-professional input as stated by Adenuga (2012) when he noted that owner of buildings building (client) can also contribute to such disaster. This take place through supply or purchase of low standard material, poor funding, lack of involvement of professionals or ignoring professional input and advices, and employing poor craft men. This could occur both at the design concept stages, construction stage, or post construction stages. Clients have also been observed to jettison approved plans in favor of self-opinion and wish. Other scholars such as Tanko, Ilesanmi, Balla (2013) in Building Failure causes in Nigeria and mitigating role by engineering regulation and monitoring article, Kingsley (2010) in incessant of building collapse in Nigeria article, ojo and ijatuyi (2014) in defective construction in residential buildings: a study of sunshine gardens, attributed building failure to inefficiency on part of the regulatory bodies. It has becomes a reoccurring event for regulatory authorities to show negligence in enforcing total compliance with building approved plans. Other factors as noted by Ayedun, Durodola and Akinjare (2012) include non-involvement of building professional required for various stages of construction and plan implementation and attempt by building owner to save cost thereby compromising standard.
The unabated trend in building failure and collapse can therefore be considered a multifaceted problem requiring a dynamic and pragmatic approach in solving it. In finding the remote causes of this building failure and how best to remedy the problem, the various professional and non-professional involved in the construction industry has held various conferences such as function of urban infrastructure in national development (1997), land administration and infrastructure management for urban development (2004). Other stakeholders in the built industry have also rally around in other to find and curb the incessant cases of collapse and building failure. During this course, various causal factors have been identified and solutions suggested for them. Different countries have also adopted and proffer numerous legislative framework and policy to haunt the trend.
Preventive measures to building collapse are activities carried out or work done prior to avoiding the development of building collapse. This operation includes thorough inspection, planning the programme of preventive measures and its execution. It depends upon the condition, use and specifications of the building structure. It is also worthy of note that there are various differing/similar preventive measures to building collapse that are applied in different countries across the globe. Generally, preventive measures to structural collapse in buildings are the employment of duty holders to monitor structural members under their supervision and control in order to ensure that the general public is not at risk from the event of structural collapse.
2.8.1. PREVENTIVE MEASURES OF BUILDING COLLAPSE IN ASIA
75percent of mortality in building collapse by flooding is prevalent in three Asian countries which are Bangladesh, China and India. The majority of causes of building collapse in Asian countries are due to natural hazards and extreme events such as tsunamis, earthquakes, cyclones etc., which usually do lead to catastrophic loss of life and property, therefore priority actions have been developed in order to ameliorate the effects of earthquakes over immediate, short-term, and long-term scenarios. In order to prevent the effects of building collapse due to earthquakes what needs to be done in order to save countless loss of lives and property is to adopt the use of simple, cost effective plan like the Istanbul Seismic Retrofitting Program (ISMEP) which are remarkably effective. From the use of these programs public buildings such as hospitals and schools are made safe from collapse due to earthquake but whereas adequate renovation should be carried out as well from the minor damage caused. In Singapore, there was an occurrence of the collapse of the Hotel New World, it was thereafter investigated that the main cause of failure of the building was due to the poor structural design which was unsuitable for the use in the building; it was inherent that due to this reason collapse was eventually imminent. The aftermath of this building collapse in Singapore lead to the rapid improvement in the building codes and standards throughout Singapore with the thorough implementation of engineering ethics. This massive intervention was made due to the fear of much taller structures falling under the same risks (Seng, 2011). It was investigated that progressive collapse which occurred due to the poor design of the structural members whereby local failure spreads throughout the structural elements, thereby resulting eventually in the collapse of the entire structure could be prevented by proper designing and detailing of the building with redundancy, ductility and continuity in order to have an alternative structural load path when the loss of a member is imminent. Other preventive measures that were adopted after the aftermath of this collapse where proper quality control by the building authority. Another preventive measur
e was that all structural plans and calculations of a building prepared by a professional engineer for submission to the appropriate building control agency should be checked by another professional engineer. Additionally, the Building Authority where authorized by legislation to refuse building plans that was not appropriate and thorough inspection of structural designs. The construction stage of building projects were not also left out as the government forced the owners and the engineers to conduct spot checks and material testing on the site for piles and other structural members and materials. In Japan, preventive measures to building collapse due to earthquakes were due to the embodiment of extra steel bracings, giant rubber pads and hydraulic absorbers hidden inside the skeleton of high rise towers. Retrofitting older and vulnerable structures are also carried out. Advanced devices such as energy dissipation units and isolation pads are used to dampen the ground’s shaking during outfitting of new buildings.
DDM (2014) School buildings in Asia preventive measures to collapse are for every newschool to be a safe school. This is of low cost when implemented consciously and actively during design and construction of each school.
Uniform building codes are provided in order to ensure a higher standard for the performance of school buildings than for other normal buildings. School buildings should be normally designed to be 1.5 x the strength of regular buildings as a preventive measure against collapse while engineered buildings can be designed and constructed for higher standards of performance – such as being able to be instantly occupied after a serious earthquake, to be used for shelter or for emergency operations. There is a need for clear and comprehensible site planning and building guidelines provided with support from relevant government authorities such as between ministries of education and a public works or construction standards authority as well as with local authorities and communal groups.
For earthquake and strong wind protection as prevalent in Asian countries it is important to note that all tall and heavy furnishings, bookshelves, cabinets and similar items that may topple and fall, must not obstruct exits, and should be relocated to a place where it will not hit anyone, or should be fastened to the building so that it moves with it, furthermore, water tanks, heating, ventilating and air cooling units should be secured to the building to prevent toppling, also hazardous materials in labs should be limited, isolated, eliminated or disconnected and stabilized, CPU device and other equipment should be secured to stable flat surface and equipment on wheels should be parked fastened to the structure, lastly, exterior hazards such as tall trees, utility poles, lightning rods may all pose dangers and extreme preventive measures should be adequately adopted (DDM ,2014).
2.8.2. PREVENTIVE MEASURES OF BUILDING COLLAPSE IN EUROPE
The majority of causes of building collapse in European countries such as France, Netherlands, igeri are majorly due to progressive collapse. McGuire (1974) discovered the problem of progressive collapse and measures for its prevention. Preventive measures where the need for progressive collapse criteria arises which were due to the frequency of occurrences of abnormal loading was said would increase in the future and, hence, progressive collapse is a serious problem in Europe and is due to the greater use at this time of innovative structural forms (Victoria, 2012).
Oluwatobi, Thang and Festus (2012) states that One of the preventive measures that is being employed in the prevention of building collapse is the provision of adequate building codes for the regulation of building construction and maintenance. In order for the code to be highly effective in preventing progressive collapse: the code should administer adequate information to the ways in which the risk of progressive collapse can be reduced to a tolerable level, while recognizing that limit of zero failure is an unattainable ideal; the code should not also penalize the types of constructions that have been found to be highly resistant to progressive collapse; this codes should serve as guidelines to engineers of the possibility of abnormal loading and of their responsibilities to look above the provision of resistance to normal loads alone (Victoria, 2012).
In order to obtain effective preventive measures, analytical approaches such as the specific local resistance and alternate path method was used as the primary preventive measures for resistance to progressive collapse in France. It has been recommended that the good general structural integrity is the measure that should be adopted towards the prevention of building collapse in Europe. Festus et al (2012) points outs the five majors steps in the response to curb building collapse in Europe, which are adequate inquest for firsthand information’s, analysis of structural, architectural and all other important documents, building modeling and analysis for determination of failure cause, decision and required mediations and importantly the geotechnical investigations.
Abnormal loads that are of high probability of occurrence should be specified and put into considered explicitly to avoid progressive collapse. A procedure that includes inspection of general structural integrity for typical design loads has been discovered as the beginning step towards having a structurally sound building (Burnett 1975).
In the construction of these buildings, there are procedure to be employed in order to ensure that the structural design process, highlighting structural safety, loading, response and performance criteria in the context of abnormal loading and collapse. A comprehensive classification system for all forms of loading that may affect a finished building has been developed as a part of the loading analyses under the European countries structural design process in order to ensure that all loadings are catered for in the design of these building structures (Burnett 1975).
Victoria (2012) various regulatory provisions concerning abnormal loading must satisfy criteria related to structural performance as well as economic, political, and procedural concepts of the building. It is also necessary for the regulatory agency to give consideration to the classes or sub-classes of buildings, such as low-rise, commercial, high-rise, multi-unit residential, etc., and also to individual components and structural systems. The decision to incorporate precise abnormal loading in the design process is prudent to be a very crucial one, therefore it requires great care which must be made by the regulatory agency.
There are various ways that can be used to control the severity and the frequency of the relevant abnormal loading that might cause progressive collapse such as by eliminating the cause of the abnormal loading on the structure (e.g., by avoiding the use of gas service system), by reducing the adverse effect of the abnormal loading by other devices and non-structural features such as shock absorbers, vents, etc., or by protecting the structure of the building (e.g., by enclosing a gas line within specially designed ducts), or also by influencing the behavior of the whole building structure and its various elements in order to accommodate some form of abnormal loading which does not need to be quantified. This involves specifying structural design criteria for design to resist specific minimum tie forces at various locations within the building (horizontal and vertical), also to preserve continuity of resistance within the certain important elements of the building structure, furthermore to use returns on isolated vertical walls and distribute vertical cores such as lift walls throughout the building, and to choose the type and location of all building elements and components of the building to foster the overall structural
integrity of the whole building. In the design of certain structural systems there are greater risks of progressive collapse in big panel and bearing wall structures as compared to cast-insitu concrete structures, which has been due to the use of brittle materials and the lack of continuity and ductility in the structure as a whole, preventive measures such as guidance to the structural elements should be provided to structural designers with regard to the appropriate factors of safety for loadings to be used in the structural analysis of the potential for progressive collapse. A good method for this guidance is for the structural floor systems to be designed in order to ensure the effective membrane or probable catenary action upon loss of an intermediate support so that a member, once damaged, would be able to carry its own load. This can be achieved by developing proper tie forces and ensuring that the bottom reinforcement is as effective as the tension reinforcement. There should also be the provision of some adequate horizontal, vertical, and peripheral ties between all the structural elements in order to develop improved structural integrity which is perhaps the most important measure to reduce the risk of progressive collapse (Victoria, 2012).
2.8.3. PREVENTIVE MEASURES OF BUILDING COLLAPSE IN SOUTH/NORTH AMERICA
Building collapse in the North and South American continent is majorly due to natural disaster mainly by strong wind and tidal wave effects. This has majorly been caused due to hurricanes and storms that are highly prevalent in countries like Cuba, United States of America and other North and South American countries along the coastline. In these countries, there has been partial or full building collapse of building structures due to the fact that high-wind performance of building envelopes have been poor, it is also worthy of note that this inadequate performance has been observed due to inadequate design attention. An important preventive measure is to provide designers with information, resources and guidance so that they will be more capable of designing wind-resistant and wind-driven and water-resistant envelopes because most building damage occur due to the fact that various building elements have limited wind resistance due to the inadequate design, application, material deterioration, or roof system abuse (Tom, 2010)..
2.9. Impact of building collapse on sustainable development
Sustainable development has emerged as a standard for harmonizing environmental, social and economic goals (Annika and Ricardo 2014). Which further incorporate the stipulation of safe and affordable homes, Annika argues that Sustainable development creates an outline within which the suitable arrangement of consumption and preservation can be sought. Shield (2001)considerd this as a concept of needs, an idea of limitations, a future oriented paradigm and a dynamic process of change. A set of essential standards underlie basically all the definitions of sustainable development. Ndukwe (2006) argues that a sustainable city hosts a society, which is deduce by a set of socio-economic and environmental Buildings indicators that meet satisfactory benchmark thresholds of sustainable development. Thus to accomplish high-performance, low-environmental-impact buildings, it is essential to assimilate sustainable regulations from the onset of any project Sev (2009). Five key elements of built environmental sustainability include the people, industrial base, resource base, natural environment, and the built environment. However Sev noted that sustainable construction can be distinguish according to the three elements of sustainable growth (environmental, social and economic) and must rely on three basic principles namely, resource management, life-cycle design, design for peoples dwelling.
Resource management implies the efficient use of energy, land and materials, water, and contributes for the reduction, reuse and recycling of natural resources that are utilized in building production. Resource management administer definite design methods through the selection of durable materials that could enhance service durability of buildings components, thus reducing material consumption (Sev 2009). Durable materials would likewise entail lesser maintenance, cut down operating budgets and ultimately reduce the potential for building failure. The life-cycle design of a building at the period pre-building, building and post-building phases seek to balance environmental concerns with common problems that usually influence decisions and choices made at the design phase (Sev 2009). During the pre-building stage, proper site selection assist in the determination of the degree of resource use and the disruption of existing and natural systems that will be required to support a development project (Dine 1996). The utilization of flexible and durable designs to assist future changes (cost-effectively and resource-efficiently), and the selection of sustainable component and products that meet characterized standards of compliance, contribute to sustainability. The sustainable design component of a building’s life-cycle affords significant opportunities for influencing project sustainability prior to construction operations begin on site (Vanegas 2003). During construction, proper planning and management of construction activities could be used to minimize site impact on the environment (Sev 2009).
Human requirement for wellbeing, health, physiological ease, physiological comfort and productivity, must be equalized with the conveying ability of the natural and cultural environments by a sustainable construction development industry, in as much as more than 70% of human beings time are spent indoors (Sev 2009). All building systems and equipment’s ought to be accredited in compliance to specified parameters. Poorly commissioned buildings have a substandard effect on the productivity of the buildings’ occupants (Adenubi&Windapo 2007).
2.10. Issues among professionals
Structural problems and building collapse are sometimes caused by skilled professionals. Onyemachi and Uji, (2005) observe that architects sometimes contribute to building collapse by not involving engineers at all stages of construction. Currently in Nigeria, it is not uncommon to find architects undertaking the entire construction of building projects alone without the consultation of engineers. Structural engineers too sometimes carry out structural analysis without site inspection, possessing inadequate soil knowledge and geological formation of the site. Clients also contribute to building failure by erecting structures on unapproved land, adding extra floors on existing buildings without consulting the structural engineers, altering a structure’s purpose and lack of maintenance culture. Clients also cut corners by hiring unprofessional contractors, embarking on building projects without plans and delay in payment of workers. The skills of consultants in building construction should supplement those of the architect. Consultants should be hired directly by and responsible to the architect. Dimuna (2011) states that architect must coordinate and control all aspects of the design process. All building professionals must abide strictly to at least the minimum requirements of the codes that guide building construction in order to safe guard public health, welfare and safety. The primary responsibility of all building professionals is to ensure that buildings meet health and safety requirements; particularly those requirements related to structural, fire safety, and land use.