Influential Factors and Structural Reliability

An overall understanding of durability and service life (design life) of both structural and non-structural materials can assist the engineer in making informed, economical decisions on whether undesirable existing conditions are still acceptable or whether rehabilitation is required. Durability is defined here as the relationship between the expected service life and the actual service life of building components, in the absence of uncontrolled defects and deterioration. Understanding the normal (expected) service life of a material or system is essential in determining whether it is suffering expected levels of deterioration, or whether defects are present that may be shortening the service life. This paper will discuss classification and estimation of the design life of structural materials and the standards and publications that address these issues. It will also discuss the issues involved in accepting undesirable existing conditions: is the public served by remedying an existing condition to strict compliance with design standards and building codes? This paper presents a synthesis of the information presented by the authors in Chapter One, "Defects, Deterioration and Durability" of the recently published book Structural Condition Assessment 1 ; for more depth of coverage on the subject matter, readers are referred to this book.

2015

The principles of structural reliability are sufficiently advanced to be used extensively to develop design standards even at international level. The concept of limit states is generally accepted and implemented. Present standards are however to a large extent based on past experience, rather than on quantitative reliability modeling. It appears that reliability principles and models can bridge the gap between probabilistic assessment and operational design. Representative theoretical models are presented to indicate how judgment based reliability concepts can be complemented or replaced by the use of such models. The importance of reliability levels, reference period, design working life, specified characteristic values of basic variables and methods to derive their design values from reliability procedures are demonstrated. On this basis a standardized basis of structural design can be formulated to convert the reliability principles (such as provided by ISO 2394) into operationa...

2000

The main objective of structural design is to insure safety, functional, and performance requirements of an engineering system for target reliability levels and a specified time period. As this must be accomplished under conditions of uncertainty, probabilistic analyses are needed in the development of such reliability-based design of panels and fatigue details of ship structures. The reliability-based structural design formats are more flexible and rational than their counterparts, the working stress formats, because they provide consistent levels of safety over various types of structural components. Such a design procedure takes into account more information than the deterministic methods in the design of ship structural components. This information includes uncertainties in the strength of various ship structural elements, in loads, and modeling errors in analysis procedures.

Structure and Infrastructure Engineering, 2009

A complex interdisciplinary approach to the reliability assessment of reinforced concrete structures is introduced and demonstrated on a real existing bridge structure. The reliability index of the structure decreases during its life cycle due to material degradation. A retrofitting to the desired reliability level should be performed. This procedure is modeled by advanced life-cycle computer simulation. The main feature of the presented approach is the nonlinear finite element analysis of the structure employed for the realistic assessment of structural behavior. A suitable technique of statistical sampling, which allows relatively small numbers of simulations, is used in this context. Different degradation scenarios are analyzed concerning their effect on the structures reliability progression. These studies give a basis for future models including analytical deterioration models combined with in situ monitoring, used to launch the degradation process. Finally the presented methodology for advanced life-cycle analysis shall be integrated in the innovative decision-making tool that supports maintenance planning of engineering structures.

2011

2005

The safety problem in structural engineering can be treated more rationally with probabilistic methods. These methods provide basic tools for evaluating structural safety quantitatively. Uncertainties in loads, material properties, and construction practice, which have been traditionally dealt with by empirical safety factors, can be taken into account explicitly and consistently in probabilistic safety assessment. Based on such methods, this paper introduces a study conducted to develop reliability-based load factors and load combination suitable for use with common reinforced concrete structures in Jordan. The selection of a probabilistic methodology for performing the necessary reliability analysis and the collection and examination of statistical data on structural resistance and loads were involved. The checking equation format for the proposed load criteria was selected, and the load factors and load combinations were computed using a constrained optimization procedure. Compar...

International Journal of Product Development, 2005

Mechanical fatigue subject to external and inertia transient loads in the service life of mechanical systems often leads to structural failure due to accumulated damage. A structural durability analysis that predicts the fatigue life of mechanical components subject to dynamic stresses and strains is a computer-intensive, multidisciplinary simulation process, since it requires the integration of several computer-aided engineering tools and large amounts of data communication and computation. Uncertainties in geometric dimensions result in the indeterministic fatigue life of a mechanical component. Uncertainty propagation to structural fatigue under transient dynamic loading is not only numerically complicated but also extremely expensive. It is, therefore, a challenge to develop a durability-based design-optimisation process and reliability analysis to ascertain whether the optimal design is reliable. The objective of this paper is to develop an integrated CAD-based computer-aided engineering process to effectively carry out design optimisation for structural durability, yielding a manufacturable, durable, and cost-effective product. In addition, a reliability analysis is executed to assess the reliability of the deterministic optimal design. Mechanical Engineers (ASME) and Associate Fellow of American Institute of Aeronautics and Astronautics (AIAA). His research areas are continuum design sensitivity analysis and optimization; physics-based product design of mechanical systems subject to uncertainties; computer-aided engineering. His dedicated efforts in research and service have garnered substantive peer recognition resulting in many notable awards, including the Iowa Regents

Proceedings of International Structural Engineering and Construction, 2015

Previous studies have established that early attention to maintainability during the early design stages of building projects provides for delivering high levels of comfort to building occupants and reducing maintenance budgets. This paper identifies and assesses the set of structural durability design defects that are attributed to lack of maintenance manager’s feedback to the design team. The research confirmed the importance of all the identified design defects based on the assessment of the maintenance experts in the 13 public Saudi Arabian universities that operate and maintain significant building stock in their campuses. The paper presents a set of validated maintainability design review checklist for consideration by design professionals, in order to reduce the likelihood of occurrence of the identified defects. This paper serves to promote awareness among the various stakeholders in the construction industry about the earned benefits of knowledge transfer from the operation...

2003

Mechanical fatigue subject to external and inertia transient loads in the service life of mechanical systems often leads a structural failure due to accumulated damage. Structural durability analysis that predicts the fatigue life of mechanical components subject to dynamic stresses and strains is a compute intensive multidisciplinary simulation process, since it requires an integration of several computer- aided engineering tools