Earthquakes and robustness for timber structures

Major similarities between robustness assessment and seismic design exist, and significant information can be brought from seismic design to robustness design. As will be discussed, although some methods and limitations considered in seismic design can improve robustness, the capacity of the structure to sustain limited damage without disproportionate effects is significantly more complex. In fact, seismic design can either improve or reduce the resistance of structures to unforeseeable events, depending on structural type, triggering event, structural material, among others.European Cooperation in Science and Technology (COST

Earthquakes and robustness

This guideline was prepared within the COST Action E55 "Modelling of the performance of timber structures" WG3 "Robustness of Structures". The main objective of the Action is to provide the basic framework and knowledge required for the efficient ans sustainable use of timber as a structural and building material. Focus is directed on the aspects of design, construction, assessment and maintenance of competitive and high performance timber structures. The Action mainly considers high performance structures where the load-bearing capacity is of predominant interest; for example, structures such as timber bridges, large-span halls and roofs, and also load-bearing elements of other types of timber structures

Introdução à análise probabilística simplificada da segurança estrutural

A análise da segurança de estruturas com vidas úteis diferentes das correntes, de estruturas existentes, de estruturas submetidas a acções invulgares, ou de estruturas reforçadas, é bastante complexa. A abordagem correcta deste problema não pode dispensar a utilização de modelos probabilísticos, que são desconhecidos da maioria dos engenheiros civis. Neste trabalho é apresentada uma breve introdução à análise probabilística simplificada da segurança, dando especial destaque à descrição dos modelos de acções e à análise de exemplos de aplicação

Robustness analysis of traditional timber trusses

In the present work, the safety of existing traditional timber trusses is evaluated, with particular emphasis on the structural robustness. Traditional Portuguese timber trusses are analyzed probabilistically, using the information provided in the JCSS model code, combined with action and resistance models provided in the Eurocodes. Robustness is evaluated through introduction of a localized defect, simulating deterioration, construction error or damages. The comparison between the reliability index considering a defect and the corresponding index for an intact structure is defined as a measure of susceptibility to local damage. The reliability index is computed using Monte-Carlo simulation combined with linear elastic finite elements for different examples.Cost Action E55 “Modelling of timber performance”

Safety evaluation of timber structures through probabilistic analysis

This work presents a procedure for the use of probabilistic modelling techniques in the assessment of safety parameters of existing timber structures, when influenced by two types of actions. The parameters of the models have been defined as probabilistic variables, and Monte Carlo simulation technique was taken into account for safety evaluation. The case study here examined concerns four king post trusses on which a safety evaluation method was conducted to determine a target reliability index. Since the structures presented a high level of deterioration, a model considering the variation of the residual cross-section and the influence of environment in resistance was taken into account. Time dependent deterioration models have also been considered. With the results given by the different used models, it was possible to obtain probabilities of failure and respective reliability indices, as well as time evolution deterioration curves for a deteriorated historical structure.The financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through project PTDC/66527-2006, is gratefully acknowledged. The third author acknowledges the support of FCT through research centre UNIC

Optimum maintenance strategy for deteriorating bridge structures based on lifetime functions

The highway networks of most European and North American countries are completed or close to completion. However, many of their bridges are aging, and in the United States alone a very significant part of the about 600,000 existing bridges is considered to be deficient and must be replaced, repaired or upgraded in the short term. The funds available for the maintenance of existing highway bridges are extremely limited when compared with the huge investment necessary, and must, therefore, be spent wisely. In this paper, a model based on lifetime functions for predicting the evolution in time of the reliability of deteriorating bridges under maintenance is presented. This model uses the probability of satisfactory system performance during a specified time interval as a measure of reliability and treats each bridge structure as a system composed of several components. In this manner, it is possible to predict the structural performance of deteriorating structures in a probabilistic framework. In addition, the optimum maintenance strategy is identified using as objective the minimization of the present value of the life-cycle maintenance cost. An existing bridge is analyzed using lifetime functions and its optimum maintenance strategy is found.U.S. National Science Foundation - CMS-9912525; CMS-0217290.Colorado Department of TransportationDutch Ministry of Transportation, Public Works, and Water Management

Multi-objective probabilistic optimization of bridge lifetime maintenance : novel approach

Due to the increase in deterioration of the existing civil infrastructure, in particular bridge networks, governments and highway agencies are trying to find methods that allow a consistent and rational management of existing bridges. In this paper, a novel approach is presented. This approach uses multi-objective probabilistic optimization over time and defines performance of existing bridges in terms of lifetime condition, safety, and cost. The proposed approach aims at providing a tool for optimal maintenance management policy definition of a large group of similar structures. Consequently, emphasis is put on the use of limited information and low computational cost. Applications to real cases are presented showing the applicability of the method as well as its advantages in terms of reduction of costs and improvements in performance.(undefined

Lifetime multi-objective optimization of maintenance of existing steel structures

In this paper, the lifetime performance of deteriorating structures, defined by their time dependent condition index and reliability index, is analyzed. The effect of preventive and essential maintenance actions on performance and cost in predicted, and the optimal times of application of preventive and essential maintenance actions are found. Due to significant uncertainty in the initial performance, effects of deterioration and of maintenance actions, as well as, times of application and cost of maintenance actions, the analysis is performed in a probabilistic framework. The reduction in performance due to deterioration is simulated using an extension of the model proposed by Frangopol (1998). The probabilistic condition index, reliability index, and cumulative cost profiles are computed using Latin Hypercube simulation. Optimization of times of application is performed using genetic algorithms. Results show the significant importance of preventive maintenance actions in reducing the lifetime cost of existing structures, but also their fundamental role of essential maintenance action in keeping structures safe and serviceable during the entire lifetime

Estudo comparativo entre modelos de previsão de resistência: leis analíticas versus data mining

Neste trabalho apresenta-se um estudo comparativo entre modelos de previsão da resistência de sistemas de polímeros reforçados com fibras (Fiber Reinforced Polymers – FRP) inseridos no betão de recobrimento de elementos de betão. Esta técnica é conhecida por Near-Surface Mounted (NSM). São analisados dois dos mais importantes códigos de projeto existentes e ainda modelos obtidos com recurso a algoritmos de data mining (DM). Os resultados obtidos demonstram que o recurso ao DM pode ser uma alternativa viável aos códigos existentes na previsão da resistência da ligação de sistemas FRP NSM

A review on the bond behavior of FRP NSM systems in concrete

This paper presents a review of current knowledge on the bond behavior of fiber reinforced polymer (FRP) systems inserted in the cover of concrete elements, commonly known as the near-surface mounted technique (NSM). In the first part, by studying the physics of the phenomenon, the typical failure modes, the most common bond tests and two of the most important design guidelines for FRP NSM systems are introduced. In the second part, a database of bond tests composed by 431 records is presented and the accuracy of existing design guidelines is assessed with this data. Lastly, the formulations proposed by these design guidelines are recalibrated based on the experimental results in the database.This work was supported by FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT (Portuguese Foundation for Science and Technology) under the project CutInDur PTDC/ECM/11 2396/2009. The first author wishes also to acknowledge the Grant No. SFRH/BD/87443/2012 provided by FCT