The impact of human errors on the performance to failure of concrete bridges

Programa doutoral em Engenharia CivilO colapso de pontes que tiveram lugar em todo o mundo nos últimos 50 anos destacou o erro humano como a principal causa do colapso de pontes. Dadas as implicações financeiras, sociais e psicológicas de tais eventos indesejados, a contribuição do erro humano no colapso de pontes deve ser investigada com o objetivo de compreender como é que a robustez e a segurança estrutural das pontes são afetadas pelos mesmos. A deterioração das pontes, leva à redução das margens de segurança, expondo muitas vezes deficiências causadas por erros de projeto e construção, realçando a importância do desenvolvimento de procedimentos de avaliação estrutural mais abrangentes, tendo em conta numerosas fontes de incertezas. Apesar destes factos conhecidos existem poucos trabalhos disponíveis investigando questões tão relevantes. Neste sentido este trabalho aborda a identificação dos erros humanos em suas inúmeras formas, ou seja, erros de projeto e erros de construção, de acordo com opiniões de especialistas e eventos de colapso de pontes registados. Diferentes erros representam diferentes ameaças à segurança estrutural; como tal o risco relativo dos erros também é investigado. O real impacto dos erros humanos na segurança estrutural é investigado através de três pontes de betão armado, considerando a probabilidade de falha perante um conjunto de incertezas como principal indicador de desempenho. Tal investigação é realizada em duas etapas, uma onde os erros de projeto e construção são introduzidos em cenários onde se entende que eles estão presentes e outra onde a possibilidade de ocorrência de erros de construção é investigada considerando a probabilidade do erro humano e a magnitude do erro. Ocorrências únicas e múltiplas de erros também são discutidas. Modelos de elementos finitos, considerada para fins de análise estrutural não linear, e modelos substitutos são introduzidos como a base das múltiplas análises de fiabilidade estrutural realizadas. Finalmente, a previsão da vida útil de pontes considerando a corrosão induzida por carbonatação e a redução da vida útil das pontes causada por erros de construção são questões também abordadas.The collapse of bridges that have taken place worldwide in the last 50 years has highlighted human error as the main cause of the collapse of bridges. Given the financial, social and phycological implications of such hazardous events, human errors' contribution to the collapse of bridges must be investigated, aiming to understand how their robustness and structural safety are affected. The ageing of bridges leads to safety margin reductions that often expose deficiencies caused by design and construction errors, underling the importance of developing more comprehensive frameworks that consider numerous sources of uncertainty for structural safety assessment purposes. Despite these facts and known needs, few works facing such relevant concerns are available. Accordingly, human errors are identified in their numerous forms, i.e., design errors and construction errors, according to expert opinions and real-world bridge collapse events. Different errors represent different threats to structural safety; thus, their relative risk is also investigated. The actual impact of human errors on structural safety is investigated through one reinforced and two prestressed concrete bridges, using their probability of failure, given a group of uncertainties, as the main performance indicator. Such investigation is performed on two fronts, one where design and construction errors are introduced under scenarios where they are understood to be present, and another where the possibility of occurrence of construction errors is investigated considering probabilistic models to describe human error probabilities and error magnitudes. Single and multiple occurrences of errors are also discussed. Finite element modelling, considered for non-linear structural analysis purposes, and surrogate models are introduced as the backbone of the multiple structural reliability analysis performed. Finally, the service life prediction of bridges considering carbonation-induced corrosion and the service life reduction of bridges due to construction errors are carefully addressed.This work was partially financed by (i) national funds through FCT - Foundation for Science and Technology, under grant agreement “PD/ BD/143003/2018” attributed to the PhD Candidate through the iRail Doctoral program; and (ii) FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020

Avaliação do desempenho de pontes rodoviárias segundo indicadores de robustez e risco face a erros de projeto e construção

Dissertação de mestrado integrado em Engenharia CivilAos numerosos acidentes de pontes que têm ocorrido ao longo dos vários anos, foram associados como principal causa os erros humanos que ocorrem nas fases de projeto, construção e operação. Este trabalho visa a identificação das principais causas de colapso de pontes associado aos erros humanos tanto do ponto de vista de projeto como da construção. Neste sentido utilizar-se-á uma base de dados de colapso de pontes, que aglomera vários casos de colapso desde a década de 60 (Syrkov, 2017), e um inquérito de erros desenvolvido junto de especialistas para identificar os erros que representam um maior risco. Identificados os erros de maior risco, serão determinadas as suas influências no caso de estudo, através dum indicador de robustez. Tal indicador será calculado com base na relação entre o índice de fiabilidade do viaduto isento de qualquer erro ou dano com o índice de fiabilidade da mesma considerando alguns danos, permitindo assim quantificar o impacto do erro no caso de estudo. Para a modelação e análise não linear do caso de estudo utilizar-se-á o software DIANA 10.1, através do qual será determinado o índice de fiabilidade consoante os erros considerados. Com este trabalho, no âmbito da ação COST-TU 1406 pretende-se contribuir para o estabelecimento de um plano de controlo de qualidade mais eficiente, diminuindo assim os casos de colapso e fatalidades que têm sido registados ao longo dos anos.To the bridges failures that have been arising over the years, experts have pointed out as the principal cause of failure the human errors that take place in the design, construction and operation phases. The main goal of this thesis is the identification of the main causes of failure associated with human errors from design and construction stage. Therefore a bridge failure database that includes many cases since the 1960s (Syrkov, 2017) and a human error survey will be used to support this line of work. After the identification of these specific causes of failures, some selective analyses of these human errors will be performed to choose those with higher impact or higher probability of occurrence to be applied to the case study. The effect of human errors in the case study will be quantified using a robustness index that will be calculated, relating the reliability index of the structure without any damage (no human error) to the reliability index of the same structure with some damage, allowing to demonstrate how some human errors can have a huge effect on structures, leading them to fail. The modelling and numerical analysis of the structure will be performed using TNO DIANA software, allowing the calculation of the reliability index of the structures for different human errors. Within the COST action TU-1406, the main goal of this thesis is to give a contribution to the establishment of a roadway bridges quality control plan with higher efficiency leading to the reduction of bridges failure, fatalities and economic loss

Human error–induced risk in reinforced concrete bridge engineering

Throughout the last century and in recent years, several bridge failures have taken place worldwide. Recent studies uncovered that the primary cause of these collapses was human errors in the design, construction, and operation phases. Regardless of this finding, there is still a considerable gap between this information and the known errors and the risk they represent for structural safety. Aiming for a better understanding of human errors, an identification procedure and a qualitative assessment of such errors considering risk-based indicators (probability of occurrence and consequence) was performed. Several brainstorming meetings with design and construction experts led to the identification of 49 relevant human errors, which were listed for further evaluation on a survey. Much more important than identifying and assessing these errors is identifying those that pose a greater threat to safety. Using a decision-making tool (analytical hierarchy process) to process all the information collected in the survey, the errors were ranked according to risk indicators. Furthermore, a qualitative risk assessment is performed, allowing the identification of the errors denoting higher risk for structural safety, according to experts’ opinions.This research was developed at the University of Minho in close cooperation with the following entities: Adão da Fonseca, COST Action TU 1406, GEG, HDP, IABSE, Portuguese Infrastructures, Mota Engil and Soares da Costa. This work was partly financed by: (i) FEDER funds through the Competitivity Factors Operational Programme (COMPETE) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project POCI 01 0145 FEDER 007633; (ii) national funds through FCT - Foundation for Science and Technology, under grant agreement “PD/BD/143003/2018” attributed to the 1st author; and (iii) FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB / 04029/202

Long term evaluation of the structural reliability of an existing concrete prestressed bridge

Reliability is an important factor to determine how safe is a structure. The aim of this study is to use the concept of reliability in order to manage the maintenance and to plan the interventions that could be necessary. The first part includes the calibration of the model, verifying the obtained results. The second part provides a 100-samples nonlinear analysis, considering the statistically important random variables. Each sample is generated considering the mean and standard deviation values of each random variable, using the Hypercube Latin method to couple them. The output is the load factor probability distribution. Using an overload probabilistic curve, the reliability index is computed, according to the Monte Carlo method. The third part illustrates the corrosion effect calculation, using FIB Bulletin 34 guidelines. Once determined the corroded area and the corrosion depth during time, the reliability index is computed, using different time values. The trend of reliability index during time is obtained in relationship with variation of the standard deviation and the load factor values.ERDF -European Regional Development Fund(EAPA_826/2018

Impact evaluation of human-made hazards on terrestrial transport infrastructure assets: modelling variables and failure modes

This work provides an overview of human-made hazards impact on the malfunctioning of terrestrial transportation systems. The impacts evaluation is gathered in four major groups, specifically: human, economic, environmental and political/social impacts. For further characterization or forecast of human-made hazards impact in real case scenarios, a traditional risk assessment framework is proposed by assuming four main steps: i) hazard identification; ii) probability of occurrence; iii) asset vulnerability; iv) impacts. The present work was carried within the SAFEWAY project, which aims at improving the resilience of transport infrastructures, developing a holistic toolset with transversal application to anticipate and mitigate the effects of extreme events at all modes of disaster cycle.H2020 -Horizon 2020 Framework Programme(UIDB / 04029/2020

Avaliação do desempenho de pontes rodoviárias segundo indicadores de robustez e risco face a erros de projeto e construção

Aos numerosos acidentes de pontes que têm ocorrido ao longo dos vários anos, foram associados como principal causa os erros humanos que ocorrem nas fases de projeto, construção e operação. Este trabalho visa a identificação das principais causas de colapso de pontes associado aos erros humanos tanto do ponto de vista de projeto como da construção. Neste sentido, utilizar-se-á uma base de dados de colapso de pontes, que aglomera vários casos de colapso desde a década de 60 [1], e um inquérito de erros desenvolvido junto de especialistas para identificar os erros que representam um maior risco. Identificados os erros de maior risco, serão determinadas as suas influências no caso de estudo, através de um indicador de robustez, calculado com base na relação entre o índice de fiabilidade de um caso de estudo (passagem superior) isento de qualquer erro ou dano com o índice de fiabilidade do mesmo considerando alguns danos, permitindo assim quantificar o impacto do erro no caso de estudo. Para a modelação e análise não linear do caso de estudo utilizar-se-á o software TNO DIANA [2], através do qual será determinado o índice de fiabilidade consoante os erros considerados. Com este trabalho pretende-se contribuir para o estabelecimento de um plano de controlo de qualidade mais eficiente, diminuindo assim os casos de colapso e fatalidades que têm sido registados ao longo dos anos.POFC -Programa Operacional Temático Factores de Competitividade(POCI-01-0145-FEDER-007043)info:eu-repo/semantics/publishedVersio

Reliability based performance assessment of a roadway bridge under seismic actions

External events represent the most common causes of bridge failure which could indicate distress, partial or total collapse (failure of all substantial parts of a bridge). One of the main environmental factors are earthquakes, which have a high impact on bridges due to irregularities presented in both substructure and superstructure and vulnerabilities acquired by the codes used in its design. This article presents a framework to obtain the reliability index of a bridge under seismic events, using response surface method and first order reliability method, based on random variables that affect the structure capacity (pushover analysis) and the seismic loads (peak ground acceleration). The bridge reliability of the case study is updated using visual inspection techniques. Results indicate that the vulnerable zone on the bridge is its shortest pier and the failure could occur due to high shear concentration in the hinge at the bottom of the pier.The authors would like to thank ISISE Institute for Sustainability and Innovation in Structural Engineering (PEst-C/ECl/U14029/2011 FC0M-01- 0124-FEDER-022681). This work was co-financed by the Interreg Atlantic Area Programme through the European Regional Development Fund under SIRMA project (GrantNo. EAPA 82612018)

Impact of construction errors on the structural safety of a post-tensioned reinforced concrete bridge

The ageing of bridge stock in developed countries worldwide and the increasing number of recorded bridge collapses have underlined the need for more sophisticated and comprehensive assessment procedures concerning the safety and serviceability of structures. In many recent failures, construction errors or deficiencies have contributed to the unfortunate outcome either by depleting the safety margin or speeding up the deterioration rate of structures. This research aims to quantify the impact of construction errors on the structural safety of a bridge considering corresponding models available in the literature that probabilistically characterise the occurrence rate and severity of some of these errors. The nominal probability of failure of structures, neglecting construction errors, is typically computed in numerous works in the literature. Therefore, the novelty of this paper lies in the consideration of an additional source of uncertainty (i.e., construction errors) combined with sophisticated numerical methods leading to a more refined estimation of the probability of failure of structures. Accordingly, some benchmark results focussing on error-free and error-included scenarios are established, providing useful information to close the gap between the nominal and the actual probability of failure of a railway bridge.This work is partially financed by (i) national funds through FCT - Foundation for Science and Technology, under grant agreement “PD/ BD/143003/2018” attributed to the 1st author; and (ii) FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB / 04029/2020

Application of quality control plan to existing bridges

The long-term quality assurance of bridges demands an adequate quality control plan detailing the main required activities and assessment tools. This paper presents the application of a quality control plan on two existing reinforced concrete bridges located in Portugal and North Macedonia. Based on the available results from visual inspections and non-destructive tests, defects and corresponding damage processes were identified. The structural safety of the case studies was assessed by means of a reliability index considering the identified damages. The reliability index computation was supported by a nonlinear finite element analysis. The computed reliability index that reflects the actual (‘today’) bridge condition was used as the base information in the preparation of possible maintenance scenarios. Three different maintenance scenarios were considered, namely, the improvement (corrective scenario), reduction (do nothing and rebuilt scenario), or delay in the reduction (preventative scenario) of the performance of the structure. By comparison of normalised net present values of the key performance indicators (reliability, safety, availability and costs), the most appropriate scenarios are found.This work was partly financed by: (i) national funds through FCT - Foundation for Science and Technology, under grant agreement ‘PD/BD/143142/ 2019’ and ‘PD/BD/143003/2018’ attributed to the 1st and 2ndauthor, respectively; and (ii) FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020

International codes in the prediction of load-bearing capacity of slender columns

The bearing-buckling capacity of slender columns is carefully addressed in modern codes by different analytical methods and non-linear advanced numerical methods for structural analysis. This work summarizes an experimental campaign and the safety formats of international codes available for the prediction of slender columns load-bearing capacity. This work is motivated on a round-robin investigation considering numerical simulations supported on non-linear material models and second-order effects (one of the methods suggested in the Eurocode), that proved an expressive overestimation of the load capacity of single slender columns when comparing the numerical results with the experimental ones. Consequently, a high interest in the safety formats of international codes arises, aiming the comparison of the predictions provided by different methods described in design codes from Canada, China, Japan and USA with the European one (namely, the nominal curvature method), as well as the identification of strengths and weaknesses of such methods.The authors would like to acknowledge IABSE COM1 and the IABSE TG1.4 members and international partners for supporting this project