Quality Tools in Building Maintenance and Monitoring

Transcription

1 Quality Tools in Building Maintenance and Monitoring Bujnak Jan,prof.,Ing.,PhD., University of Zilina, Faculty of Civil Engineering, Komenskeho 52,01026 Zilina, Slovakia, Phone: , Fax: , Odrobinak Jaroslav, Ing., University of Zilina, Faculty of Civil Engineering, Komenskeho 52,01026 Zilina, Slovakia, Phone/Fax: , Abstract Attitude to maintenance and monitoring of building structures depends on management strategy. Actual practice is completed by suggestions for improving execution of these important activities for durability and reliability of structural systems. Total quality management provides a set of effective tools. For this purpose, the principal aspects of the maintenance and monitoring process are discussed in the paper. Key words: maintenance, quality assurance, structural imperfections, quality tools. 9

2 Introduction Building structure may be considered to be a facility, which can be viewed in wider context as a direct generator of income. Sometimes this building function is underestimated. The building exploitation efficiency is traditionally assessed only by space utilization and energy consumption. However building maintenance may have important impact on the productive performance of the environment. Maintenance work is inevitable, because building materials naturally deteriorate over time with usage and exposure to the elements of climate. The rate of materials and components deterioration in the present time may be partially controlled by the appropriate design and the procurement process. It is also important to underline the importance of the proper building monitoring and exploitation. Optimal and professional strategy for these activities have been developed and actually existed, Bujnak,J. (1996). Despite the presence of this expertise, some property owners de not take this professional advice. Surveying and maintenance, they consider wrongly not to carry directly to productive output. The maintenance is important also to meet hygienic and safety requirements. But there exist social and economic limits for maintenance execution. It is often necessary to find compromise between the above conditions. In this paper the recent progress in this area and corresponding suggestions to improve maintenance components are given. Maintenance policy Maintenance strategy may be considered as a set of ground rules for allocation of resources between the various types of maintenance action that can be taken. It is possible to distinguish a policy specifically directed towards building maintenance and strategy decisions taken with respect to other matters, but influencing maintenance. The organization should manage every action or process to be carried out right, first time and every time. Especially, the public sector charged by bridges, roads a railways maintenance generally do not have the choice. Total Quality Management (TQM) can effectively help the public companies to perform better. The proportion of finance and staffing resources allocated to building maintenance is 10

3 determined in a competitive environment. Generally, maintenance tends to compete on rather unfavorable terms for all resources, and for finance in particular. TQM starts with the identification of the needs and expectations of customers. The requirements on the maintenance include appropriate technical standards, but also operational, time and financial standards, reliability and cost effectiveness, amongst many other features. Maintenance position The administrative management depends on organization s attitude to the maintenance and building management. The position of the maintenance within the organization and its relationships with others departments and functions indicates the degree of importance attached to maintenance by company management. Mostly, this activity is obviously considered as an important part of the organizational objectives, but it depends on a company structure. In the case of an occupant dominant maintenance organization, the major emphasis is on speedy service to occupants where work is initiated by occupant requests. As very quick service is required, this maintenance system becomes overloaded due to highly unpredictable activities, and probably inefficient use of resources. Management is concerned with keeping good relations with occupants, and control systems are related to speed of service rather than productivity. Costs are difficult to predict, but tend to be relatively high, because the needs of the important labor force to be capable of meeting peak demands. The owner dominant type maintenance aims to keep costs as low as possible, to protect the value of the property and to ensure that properties are utilized without major stops. When the maintenance group dominates, the professional access to maintenance exists. Preventive maintenance programs are planned to achieve quality and effectiveness. The maintenance team is very well trained. According to the purpose, it is useful to underline the importance of preventive maintenance, carried out at predetermined intervals and corresponding to prescribed criteria. It aims to reduce the failure probability and the performance degradation. The alternative corrective maintenance is carried out after a failure occurred and intended to restore a component for performing its required function. The process management application can improve the maintenance strategy. It consists in the transformation of a set of inputs, which include actions, methods and operations into 11

4 desired outputs in the form of more effective maintenance services. Analyses by an examination of processes taking place in maintenance execution could determine the action necessary to improve quality, Bujnak,J. (1980). There are some key or critical processes. These are activities which the maintenance organization must carry out especially well if its mission and objectives are to be achieved. Maintenance execution Execution of maintenance operations in buildings during exploitation needs coordination with others activities. The concrete administrative management depends on organization s attitude to the maintenance and to construction management. The obvious traditional maintenance represents work carried out at intervals in order to keep building structure in an appropriate condition. This work may involve the repair or replacements of a structural part, necessitated by natural deterioration or normal wear and tear. The classic techniques, and the way they have always been used will not generally result in better quality. The most important task connecting to routine maintenance is to identify a reasonable maintenance cycle and routine operations. However employing more inspectors, tightening up standards, developing correction, repair and rework teams does not promote quality. The many quality problems are originated in the service or administration areas. The quality assurance system presents actually a progressive procedure. It involves a company organization in such a way that the human, administrative and technical factors affecting quality will be under control and produce consistency. This consistency can only be achieved if a maintenance service is performed in exactly the same way, every time. The process is then under control. The people involved should operate according to the documented system audit and this system still meets requirements. If in this system audits and reviews it is discovered that an even better standard can be achieved by changing the method then the change may be executed. Quality improvement techniques backed by good organization and team commitment provide objective means of controlling quality in any process. The total quality management requires that the maintenance process should be improved continually by reducing its variability. This is brought by studying all aspects of the process and a constant search for improvements. The complexity of most of the process which are operated in the maintenance services place them beyond the control of any one individual. The effective way to tackle problems 12

5 concerning such processes is through the use of teamwork, because the recommendations are more likely to be implemented than individual suggestions. Tools To allow people to operate at a high standard, they are equipped with the tools and information to do so. For effective property management, the accurate picture of what the structural estate comprises, the characteristics of properties and their conditions are necessary. Information amount depends on structural type and maintenance requirements. The information can normally be obtained stored in accessible form and easily kept up-to-date. The amount of detail and depth of coverage required for structural system under consideration is extremely variable, and in practice will be determined by the precise requirements and purposes of the survey. The classical manual approach of data collection can be actually replaced by hand-held computer programmed with a series of questions that can be multiple choices or acting as prompts. Built-in checks can eliminate absurd answers et missing some question. A final quality report should give a picture of the condition of the structure. Recommendations for technical care and monitoring of building in service parameter are fixed by standard. Inspections are obviously categorized according to temporal cycles and reasons for which they are executed. Routine inspections are normally carried out to identify structural parts in need of repair or replacement between routine maintenance cycles. By using carefully prepared checklists with clearly defined criteria for classifying the condition of particular elements, it is feasible to use non-technically qualified staff to collect condition data. Larder buildings and estates require special methodology for locating components as well as various imperfections The burn-in structural imperfections obviously may occur during construction or soon after completions, Bujnak,J. (1995). Actually they can be reduced by quality control of building process. The failures occurring over a longer period of time are due to wear out of building structures, Bujnak,J.,Vican,J (1996). Between these two will be on going failures, which can be classed as in service. The defects causes are sometimes the failure combination. The traditional classification of corresponding maintenance into routine or remedial, or planned and unplanned categories is clearly of rather limited value. Strategic repairs and maintenance represent work required for the long-term preservation of structural buildings and include planned maintenance interventions. Tactical repair and maintenance works represent day-to-day miner actions of 13

6 immediate need. Unexpected failures might occur, because it still remains a high degree of uncertainty in the prediction process. Thus, maintenance program must make provisions for a system of regular inspections. To solve the inspection planning problem, in its most general formulation, is very difficult, because it generally requires the calculation of probabilities of a large number of intersection events. A building structure can contain a large diversity of different types of systems and components. It is also important to realize that the degree of control of the engineering system achieved by the inspections is strongly influenced by the reliability of the inspectors, that is, their ability to detect and size degradation. The reliability of inspections may be subject to large uncertainties and this must be taken into account in the planning of inspections. Risk-based inspection planning, as a result of development over the last two decades can be appropriate especially in the case of complex engineering facilities. This inspection decision problem involves the exchange of knowledge and information about the facility at various levels both in the organization of consultant and client, ensuring that a firm basis of the maintenance project will be achieved. The degradation process and principal components for detailed assessment should be identified. Having collected the basis information, a qualitative and semi-quantitative risk analysis is performed. The purpose of this screening process is to establish an overview of the facility, its systems and components with regards to their contribution to the risks and degradation mechanisms. This is carried out in accordance with requirements for safety. commonly specified in terms of maximum risk value acceptance to personnel, the environment and economy. This preliminary risk assessment can identify the subsystems and components of two types, namely those which should either be included in regular corrective maintenance or monitoring activities and structural parts which should be considered for further and more detailed quantitative inspection planning assessment. Thus, the risk screening process cut down the number of components for further consideration. The risk screening categorization methodology is illustrated in the risk matrix in Fig.1: - If the probability and consequence of failure is low, inspection will have no effect on the risk, then the recommended action is minimum surveillance. - If the probability of failure is low but consequence is high, preventive maintenance should be considered to control the risk. - If the probability is high but consequence is low, corrective maintenance is recommended. 14

7 - When both probability and consequence are high detailed risk-based inspection is required. Probability corrective maintenance detailed analyses preventive maintenance Consequences Fig.1.Failure probability /consequence matrix The final inspection plans for all components selected in the risk screening stage should provide instructions on where to inspect, how to inspect and when to inspect. The total maintenance costs can be divided into inspection, repair and strengthening. Considering also eventual failure costs then the resulting inspection plans represent the rather complex optimization problem. To solve this optimization problem in its most general formulation is hardly possible. This is due to the great computational effort as well as lack of some optimization parameters given by operational constraints Therefore simplifications for practical applications are accepted. The first more simple access consists in assuming equidistant inspection times. In this case, the inspection planning problem consists of searching the optimal number of inspections, the repair decision rule and the inspection quantities. Due to the constant inspection intervals, the identified inspection plan will be sub-optimal but provide a strong tool in inspection planning. Another approach is to apply a model where the acceptable annual failure probability for failure is constant. The number and times of inspections are a function of this single optimization parameter. Having identified the cost optimal inspection plan for all considered components, these inspections are rearranged in order to achieve overall optimal inspection schedule of building structure taking simultaneously into account : 15

8 - availability and position of the maintenance team, - impact of inspections on the operation of the facility, - logistic complexity. The inspection plans are determined under the assumption of no defect detected at inspections. For some elements, detection of imperfection at inspection is difficult or impossible and the assumption therefore is reasonable. If a defect is detected and repaired or replaced, as is generally the case, the updating of inspection plans can be required, because stochastically changed impact of retrofitting component. Concluding remarks Maintenance quality has to be managed, because it will not just happen. Clearly it must involve everyone in the quality chains and be applied throughout all maintenance operations. This quality cannot be regarded only as the responsibility of some quality control department. It necessities continuously to improve maintenance operations and the way all jobs are done throughout maintenance processes. References Bujnak,J.(1980) Comments on durability of bridges. Inzenzyrske stavby, Vol. 30 No. 5, pp , (in Slovak) Bujnak,J., Vican,J. (1986) Influence of bridge damages on load carrying capacity. Silnicny obzor, Vol.47 No.6, pp Bujnak,J. (1995) Technical assessment of steel structures failures, in Conference proceedings Recoznawstwo budowlane University of Kielce, Poland, pp Bujnak,J. (1996) Steel structures and bridges. Management, Maintenance & Retrofitting, Alfa, Bratislava 16