Application of Rough Set Theory to Rule‐type Knowledge Discovery from Field Inspection Data on Highway Bridges

This paper describes an acquisitive method of rule‐type knowledge from the field inspection data on highway bridges. The proposed method is enhanced by introducing an improvement to a traditional data mining technique, i.e. applying the rough set theory to the traditional decision table reduction method. The new rough set theory approach helps in cases of exceptional and contradictory data, which in the traditional decision table reduction method are simply removed from analyses. Instead of automatically removing all apparently contradictory data cases, the proposed method determines whether the data really is contradictory and therefore must be removed or not. The method has been tested with real data on bridge members including girders and filled joints in bridges owned and managed by a highway corporation in Japan. There are, however, numerous inconsistent data in field data. A new method is therefore proposed to solve the problem of data loss. The new method reveals some generally unrecognized decision rules in addition to generally accepted knowledge. Finally, a computer program is developed to perform calculation routines, and some field inspection data on highway bridges is used to show the applicability of the proposed method.

Causes of Structural Failures with Steel Structures

This paper is based on the experience from investigating over 400 structural collapses, incidents and serious structural damage cases with steel structures which have occurred over the past four centuries. The cause of the failures is most often a gross human error rather than a combination of “normal” variations in parameters affecting the load-carrying capacity, as considered in normal design procedures and structural reliability analyses. Human errors in execution are more prevalent as cause for the failures than errors in the design process, and the construction phase appears particularly prone to human errors. For normal steel structures with quasi-static (non-fatigue) loading, various structural instability phenomena have been observed to be the main collapse mode. An important observation is that welds are not as critical a cause of structural steel failures for statically loaded steel structures as implicitly understood in current regulations and rules for design and execution criteria.

Check bridges on vitality

Taking place in different countries the collapses of buildings due to natural and man-made impacts or terrorist attacks have put the issue of survivability of buildings, that is, vitality – the safety of their total integrity in case of failure of individual bearing elements. The present report discusses the possible cases of failure of the individual bearing elements in the bridge constructions for various constructive systems and the considerations on the calculated checking on vitality.

Influence of Human Error on Structural Reliability

In common structural design, random variables, such as material strength or loads, are represented by fixed numbers defined in design codes. This is also referred to as deterministic design. Addressing the random character of these variables directly, the probabilistic design procedure allows the determination of the probability of exceeding a defined limit state. This probability is referred to as failure probability. From there, the structural reliability, representing the survival probability, can be determined. Structural reliability thus is a property of a structure or structural member, depending on the relevant limit states, failure modes and basic variables. This is the basis for the determination of partial safety factors which are, for sake of a simpler design, applied within deterministic design procedures. In addition to the basic variables in terms of material and loads, further basic variables representing the structural model have to be considered. These depend strongly on the experience of the design engineer and the level of detailing of the model. However, in the clear majority of cases [1] failure does not occur due to unexpectedly high or low values of loads or material strength. The most common reasons for failure are human errors in design and execution. This paper will provide practical examples of original designs affected by human error and will assess the impact on structural reliability.

Estimation of Structural Safety for Internally Grouted Post-tensioned External Tendons

In February, 2016, one of the external tendons in pre‐stressed concrete (PSC) box girder bridge in Seoul was failed due to corrosion after 17 years of service. The failure was found during the thawing season regular inspection. Since it was the first tendon failure occurred in South Korea, in‐depth investigation was performed and found that multiple tendons were corroded at many different locations. Seoul City had been preparing for the maintenance of PSC box girder bridges, but the draft maintenance guideline considered overall condition of the bridge and little attention was paid to the condition of tendons. The bridge was evaluated as per the draft guideline and rated as ‘Medium Risk’ although one external tendon was failed. The indices for the evaluation should be properly weighted to prevent failure of tendons.

Design of steel and composite structures for robustness

The paper briefly reports on investigations concerning the robustness of steel and composite structures. When applying the alternate load path method for redistributing the loads resulting from a column loss especially the detailed consideration of the behaviour of beam‐to‐column joints is important. A crucial aspect is the investigation of the available rotation capacity of the joints as well as the required rotation capacity of the joints. Finally a method is presented that can be used in order to verify the rotation capacity for permanent load situation as well as for accidental load situations.

Shortsighted Leadership in Construction

Over the past 50 years there has been a significant decline in the quality of constructed outcomes in the Australian building industry. The decline can be readily attributed structural changes in project delivery methodologies that have been brought about by the focus of some industry participants on time, cost and profit at the expense of quality, durability and the project encapsulated environmental health. The changes have been stimulated by legislative changes that have increased the complexity of compliance while at the same time reducing the oversight of work to ensure compliance. A striking impact of these changes has been to force changes to the leadership of the project delivery process where the focus of the effort is on project economics to the exclusion of meeting the project brief and the projects long term durability.

Qualifications and Internal Checks versus Independent Proof of Structural Design

Against the background of European standardisation of structural engineering principles, there is intense debate about the extent to which self-regulation and internal inspections can replace independent inspection of calculations relating to static equilibrium, project scheduling and execution of construction work by a third party. There is also discussion about whether the likelihood of errors decreases and, to a certain extent, whether errors would be unlikely or would not have a significant effect on the stability of buildings, as engineers become better qualified. This contribution examines both questions and gives examples from the author’s practical experience.

Structural Failure Studies

Case studies of structure failures due to accidental actions are presented in the paper. Bad design does not mean only errors of computation, but incorrect theories or confidence in inaccurate data. The bridge structure failure during concrete pouring due to combination of the above reasons proves this statement. The next example of a sufficiently designed and constructed temporary platform illustrates importance of proper operations. Even an excellently constructed hall could not stand on bad foundations. Some failures are not the result of poor project, but the consequence of unforeseen events that create uncommon loads on structures. But, the main goal of the paper is to help construction engineers, workers, project managers, and regulatory bodies identify problems in construction design, project execution and management of field engineering practise.

A simplified method for evaluation of robustness of bridges

Many theoretical methods for assessing robustness introduced so far, due to their complexity, appear to be almost impossible to use in practical design. Therefore, the present study proposes a simplified method for evaluation of the robustness of bridges. In the proposed methods two strategies for providing robustness are utilised: increasing local resistance in order to prevent the key element from failing; increasing damage tolerance by providing redundancy in order to recompense failure of the element. Accordingly, two separate approaches for evaluating bridge robustness are introduced. Both of them are based on a rating system, where each evaluated component is assigned with a partial factor, which value can vary from 0 to 10. Next, in each approach, all points from partial factors are summed up. The robustness of the bridge can be evaluated by comparing the final value with possible minimum and maximum values. The proposed evaluation method has been implemented in a case study: 118,8 m long four spans prestressed concrete girder overpass. The method appears to be promising in estimating the robustness level in considered bridges. Furthermore, it can provide assistance in identification of the components of the bridge that contribute to its local resistance and redundancy level.