A method for prioritisation of concrete bridge inspections in South Africa

Nsabimana, Placide (2015-03)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: Bridges are amongst the most important structures of any highway network. Once the bridge construction is complete and a bridge is put into service, it is subjected to deteriorations. An effective condition assessment, as a component of bridge management system, is therefore necessary to keep bridges in admissible conditions of safety and serviceability. In South Africa, some bridge authorities do not have sufficient funds to carry out bridge inspections at required intervals. In the case where bridge authorities have enough funds, a systematic inspection is performed, covering a number of bridges that are not in need of inspection. Inspection and maintenance for a limited number of bridges randomly chosen may result in an increase of the number of bridges in critical conditions. A bridge inspection prioritisation method that takes into account the need of inspection of bridges is therefore needed for South African highway bridges. This research provides a prioritisation method for concrete bridge inspections by integration of nonprofessional inspectors, imagery inspection and deterioration models. To achieve the research objectives of this study, a literature study has been carried out to understand bridge inspection practice in general and South African practice in particular. The literature helped also to identify previous works on bridge inspection prioritisation, the use of information from informal sources, imagery inspection and involvement of non-professionals in bridge inspection and use of deterioration models in bridge management. A survey has been conducted amongst South African bridge authorities in order to fill the literature gaps. Inventory and inspection data of bridges managed by South African National Roads Agency Limited (SANRAL) was used to develop a deterioration model by considering bridge characteristics such as bridge age, number of spans, and bridge type. Based on the literature review, results of surveys and estimated regression parameters, a bridge inspection prioritisation method has been developed. This method comprises three phases. The first phase is the initial screening that consists of an identification of bridges with critical defects that have not been repaired yet. These bridges, to which are added bridges that have not been inspected in the previous inspection, constitute the first inspection priority category. The second phase is an imagery screening which is an analysis of digital photographs for detection of defects that need urgent assessment by professional inspectors. The analysed photographs are taken by non-professional inspectors and uploaded to the Bridge Management System. The third phase is a grouping of bridges in inspection priority categories as a function of their physical characteristics and deteriorating factors using deterioration modelling. The method has been applied on SANRAL bridges using inspection ratings of 2011-2012. 422 SANRAL bridges have been categorised in the first inspection priority group by considering hydraulic related defects as critical. The third phase allowed to rank 522 possible combinations of bridges based on their characteristics. The developed method would help bridge authorities where inspection budget is limited, to prioritise bridge inspection as a function of needs of inspection.

AFRIKAANSE OPSOMMING: Brûe is ʼn belangrike deel van enige snelweg netwerk. Wanneer brugkonstruksie voltooi is en dit in diens gestel word, is die brug onderhewig aan skade en verval . 'n Doeltreffende toestandsassessering, as 'n komponent van ʼn brug bestuurstelsel, is dus nodig om brûe in ʼn toestand van veiligheid en diensbaarheid te hou. In Suid-Afrika het sommige brugowerhede nie genoeg fondse om bruginspeksies teen vereiste intervalle uit te voer nie. In die geval waar ʼn brugowerhede wel genoeg fondse het, word stelselmatige reekse inspeksies uitgevoer, waar brûe wat nie lukraaknoodwendig op daardie stadium inspeksie nodig het nie, ook soms ingesluit word. Inspeksie en onderhoud vir slegs 'n beperkte aantal brûe wat gekies word kan 'n toename veroorsaak in die aantal brûe wat in ʼn kritiese toestand is. 'n Bruginspeksie prioritiseringmetode wat brûe identifiseer vir inspeksie is dus nodig vir Suid-Afrikaanse brugowerhede. Hierdie navorsing stel 'n metode voor wat bruginspeksies prioritiseer deur gebruik te maak van nieprofessionele inspekteurs, inspeksie van foto’s en brugtoestandsvervalmodelle. Om die navorsings doelwitte van hierdie projek te bereik, is 'n literatuurstudie uitgevoer oor die praktyk van bruginspeksie in die algemeen, en meer spesifiek om die praktyk in Suid-Afrika te verstaan.. 'n Opname is voorts onder Suid-Afrikaanse brugowerhede uitgevoer om gapings in die literatuur aan te vul. Inventaris en inspeksie data van brûe wat bestuur word deur die Nasionale Padagentskap (SANRAL) is daarna gebruik om 'n toestand agteruitgangsmodel te ontwikkel deur die eienskappe soos brug ouderdom, aantal spanne en die tipe brug in ag te neem Gebaseer op die literatuur, resultate van opnames en beraamde regressie parameters is 'n brug inspeksie prioritiseringsmetode ontwikkel. Hierdie metode bestaan uit drie fases. Die eerste fase is die aanvanklike siftingsproses wat bestaan uit die identifisering van brûe met 'n kritiese defek wat nog nie herstel is sedert ʼn vorige inspeksie nie. Hierdie brûe, wat ingesluit word by ander brûe wat nie geïnspekteer was in die vorige inspeksie nie, is die eerste kategorie van inspeksie prioriteit. Die tweede fase is 'n ontleding van digitale foto's vir die opsporing van defekte wat dringende assessering deur professionele inspekteurs nodig het. Die foto's word geneem deur nie-professionele inspekteurs en dit word gelaai op die brug bestuurstelsel. Die derde fase is die groepering van brûe in inspeksie prioriteit kategorieë as 'n funksie van hul fisiese eienskappe en vervalfaktore met die hulp van agteruitgangsmodelle. Die metode is toegepas op die SANRAL brûe met die hulp van inspeksie graderings van 2011-2012. Deur die aanname van hidrouliese defekte as van kritiese belang, is 422 SANRAL brûe in die eerste inspeksie prioriteit gegroepeer. Die derde fase prioritiseer 522 moontlike kombinasies van brûe op grond van hul fisiese eienskappe. Die metode sal brugowerhede waar inspeksie begrotings beperk is, help om bruginspeksies te prioritiseer as 'n funksie van die noodsaaklikheid van inspeksie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96770
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