Structural Design and Assessment - Essay Example

? Structural Design and Assessment BY Xxxxxxxxxxxx Table of Contents Requirements of a structures inspection and assessment 2. Maintenance management system(MMS) and process 3. Common defects in structures and bridges 4. Solution to defects 5. Case study and calculations 6. Recommendation 7. References Requirements Of A Structures Inspection And Assessment There are two types of inspections that are made as a part of structural assessment. First is the inspection that is made while and just after the construction process is complete whose basic purpose is to ensure the quality of construction done and work is done according to the design. This phase is important for the structural stability and to ensure the safe design implementation and this inspection will also affect the life of the structure because mistakes made at this stage can be corrected on spot but after the facility is complete then the retrofitting would be very difficult and expensive. Then the second phase is the post construction inspection which is done after some time that is 6 months, 1 year and 5 years normally the frequency of the inspection decides its extent, mostly the inspection made after 5 years is far more extensive and detailed than that of which is done after 6 months. This inspection is mostly done by visual monitoring of the facility by professional which inspect the vital areas that are vulnerable to failures and crack propagation. Both the inspection types are extensively vast and hence require a lot of discussion where as at the moment I will only focus on the Post Construction inspection. The key requirements of the inspection would be consisting of many aspects the first among them is property identification information which include the location and type of infrastructure facility. Then a detailed study and preliminary visual inspection of various structural systems employed in the building/structure and applicable non-structural components is done. Further progress in the assessment and its requirement includes critical analysis existing condition of the various structural systems, including foundations, bearing walls, framing, columns and beams, floor systems, roof systems, and their connection and construction details. During the assessment and inspection procedures one fact is also to be considered that the Engineers and/or construction specialists conducting the structural assessment should be knowledgeable of the construction methods, materials, load capacities, and design details of the infrastructure facility or structure type being analyzed, as modern structural design approaches will likely not be directly applicable due to the fact that these structures were made quite a long time before and employed primitive construction standards and design methodologies. William Hover (2008).In addition to requirements discuss above there are other as well and which are equally important, significant among these is analysis of the deficiencies, damage, and failures to determine/identify their evident, probable, or possible causes and after these are been highlighted then it is the responsibility that recommendations for corrective measures, design solutions for stabilization and/or repair and maintenance must be made. Then at the end a cost estimate must be made of the repair works and the cost engineering under different scenario must be made which include the recommendation of new construction or choices of retrofitting and localized repairs. Maintenance Management System Then comes the Maintenance Management System(MMS) for a large infrastructure organization, although the system is very extensive and encompasses many fields but the key focus in this discussion would be on infrastructure organizations and their requirements. MMS is a computerized database system which is made to maximize and increase the efficiency of deferred maintenance and capital improvement activities through the organization and its services using standardized procedures to document and prioritize field facility and equipment needs and to report accomplishments. It is a management tool for planning and budgeting deferred maintenance, capital improvement, equipment repair and replacement, and construction projects. Now a days these systems are used in large infrastructure organizations such a Kuwait Infrastructure Maintenance Management System (KIMMS) Abdul-Aziz (2009) and others are also following the way. The major aims of implementation of such systems is the effective use of resources(money, manpower, machinery), to provide accurate data for planning and executive of maintenance works at their respective levels(national, regional or localized). Then being specific to the infrastructure organization it must be noted that the system is highly effective when the total scope of a construction project generally exceeds $500,000 in cost. In addition construction projects may have both maintenance (replacement, reconstruction, renovation, or demolition of an asset without expanding it or changing its function) and a capital improvement component (erection, installation, or assembly of a totally new facility or the expansion or alteration of an existing facility to serve needs different from or significantly greater than those originally intended). Due to the massively large size and very high level of funding issues, construction projects done on the MMS receive close scrutiny in the Department’s five year planning process. Then I will rather prefer to have show the whole MMS system through this diagram which will make many things more organized about the process. As the process flow diagram(Depository Services Program, Govt of Canada (2000)) show almost every thing that is present in the Maintenance Management System(MMS) which initiates from asset inventory and Task, frequency and times, where as ends on the maintenance budget and value engineering of the project. Common Defects In Structures And Bridges Now as we have a detailed discussion on key requirements of a structures inspection and maintenance management system for a large infrastructure organization. I would like to drift to common defects in structures which initiate the maintenance procedures and what are their solutions. When talking broadly there are mainly four causes of production of defects or deficiencies in structures they include firstly Design Deficiencies, secondly Material Deficiencies, thirdly Substandard Workmanship and fourthly Subsurface or Geo-technical Problems. The most visible sign of defect in the structure are the cracks which are formed, cracks are formed in every structure when it comes under excessive stress and loading and the reason for these cracks would be the defects in the structure and these are a). Moisture change b). Thermal movement c). Elastic deformation(excessive loading) d). Creep e). Chemical reaction f). Foundation movement & settlement of soil. After these there are some defects due to negligence which include improper layout, improper orientation of buildings, far & setbacks, casual decision for foundation, improper construction of wall, construction joint between old/new wall and dissimilar structure, improper slope of floors in rooms and bathrooms, breakage of wall & plastering by installation of electrical insulation, improper drainage and sewage line and defects painting and distempering. Then some defects that are seen in steel structures especially the bridges includes the corrosion of the steel due to ineffective and low quality painting works and consequently the paint is seen to peel off or blister from the surface the main reason for this is the improper application of paint and then the quality of paint used. So the solution to this problem would lie in the workman ship of the painters and strong contractual binding of quality control of materials by both client and contractor. The second defect that is seen in steel bridges is that the member of the bridge are designed by specific sizes and every thing else (bolts joints rivets welding connections stay plates ) are designed accordingly to the most precise calculations, but the sizes written in the manuals or catalogue do not match the sizes of the actual members that are brought to site, they are some times short some times longer so while the fabrication process these members are forced to fit in and some extra force is applied on the member to squeeze them in, consequently what happens is there are residual stress produced in the member and the whole structure gets over stressed. So in order to solve this issue the manufacturer of the members must have high precision engineering equipment at his facility so that exact sizes can be produced. Then another defect that is seen is at the cold worked holes where the cold working results into the loss of ductility and increase in brittleness. This becomes critical for the durability of structures subjected to fluctuation of stresses such as railway bridges and crane girders. Under cyclic loading fatigue cracks can initiate from such punched holes. So in this case the solution is that drilling must be done rather than punching. As we are well aware of the fact that failure mainly occurs from joints and connection so special quality checks should be in place when welding is done for connections, the welding should be water proof and should not have any of the problems such as undercut, porosity, lack of side wall fusion, cracks, slag inclusion and incomplete penetration. Summarizing every thing that there might be problem in erection of such structures and many other problems. But there are solutions and checks for every problem, so good quality workmanship and best material selection solves almost all the problems and defects and proper maintenance and repair prolongs the service life of structure and keeps the inhabitants safe as well. Case Study Question Part 1 Section 762 x 267 x 147 UB Moment = 0.5x1.8x234 + 0.5x40x(1.8+2.6) + 25x2.6 + 0.5x80x(2.6+4.2) + 25x4.2 + 0.5x40x(4.2+5) = 210.6+ 88+ 65+ 272+105+184 = 924.6 KN.m M max = 924.6 KN.m ?max = = Part 2 When there is 25% reduction in the section, Assuming reduction in second moment of inertia Inew = 0.75 Ioriginal , Where as the moment remains the same as before ie 924.6 KN.m ?max new = = Part 3 Recommendation: As before the corrosion the applied stress was less than the allowable stress so the beam was safe, where as when there was a reduction in the section that resulted into a massive increased applied stress than the material can sustain which is 348 N/mm2 So it must be looked into and some correctional measures must be made. Where I have majorly three recommendations, first being that the surface of the beam must be painted so that the corrosion must be prevented. The second major work is to be done when the corrosion has occurred then we have to increase the sectional area back and for that I suggest that the welding of base plates and connection plates must be attached to the beams where corrosion is excessive so that the section and moment of inertia is increased therefore decreasing the applied stress. Third recommendation is done when no other solution is there, this recommendation is that the span of the beam is decreased to a lesser value this can be achieved by providing another support when the same span. This will decrease reaction at the supports and consequently the maximum bending moment and hence reduce the applied stress. There are other measures also to be taken but I think that these are the most relevant ones. References William Hover (2008). Preservation Planning Guidance, Architectural Reviewer. Georgia: Georgia Department of Natural Resources – Historic Preservation Division. Abdul-Aziz Abdul-Rahman Al-Kulaib. (2009). Kuwait Infrastructure Maintenance Management System (KIMMS). Available: http://www.gisqatar.org.qa/conf97/links/d1.html. Last accessed 05-03-2010. Depository Services Program, Government of Canada (2000). MAINTENANCE MANAGEMENT SYSTEMS. Canada: Government of Canada Publications Owens G.W and Knowles P., ‘Steel Designers manual’, 5th Edition, The Steel Construction Institute, ELBS Blackwell Scientific Publishers, London 1994. BRITISH STANDARD BS 5400-2:2006 Steel, concrete and composite bridges Part 2: Specification for loads Westbrook R. & Walker D. (1996) Structural Engineering in Practice; Longman Dr. A Ghafar Ahmad. (2004). THE DILAPIDATION SURVEY REPORT. Available: http://www.hbp.usm.my/conservation/DilapidationSurvey.htm. Last accessed 07-03-2010. Roberto D. Cigolini • Abhijit V. Deshmukh Lorenzo Fedele . (2009). Recent Advances in Maintenance and Infrastructure Management. Available: http://www.slideshare.net/erletshaqe/recent-advances-in-maintenance-and-infrastructure-management. Last accessed 06-03-2010 Read More