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This paper contributes to the ongoing discussion on the tentative target reliability levels for the design of structures and calibration of codes. The proposed extension of the existing approaches for code optimisation allows a consistent calibration of codes through all levels of design. The basis is taken from the normative decision theory as the rational strategy for taking decisions under risk. The method proposed supports code-making by optimizing reliability elements accounting for i) the safety format adopted in the code, ii) the design level that is regulated, and iii) the differences among the design cases regulated by the same code. Some of the decision theoretical aspects that are object of discussions in the research community are addressed. The work aims at providing a more robust and transparent background to target reliabilities in design standards.

To date, our built environment is broadly developed and maintained on the basis of structural design standards. Most design standards contain simplified semi-probabilistic safety concepts that help daily structural engineering decision making using simple calculus. For few projects, the semi-probabilistic safety concept is replaced by advanced probabilistic methods that allow for reliability-based design. Neither include explicit consideration of optimality criteria. However, for the development and the calibration of the semi-probabilistic and probabilistic safety concepts it is important that societal preferences in regard to risk acceptance and the optimal use of natural resources are explicitly considered. In the present contribution, the development and calibration of semi-probabilistic and probabilistic structural design standards is represented as a formal decision problem allowing an optimal combination of reliability elements to be identified.

The performance to withstand biodeterioration of highly insulated walls is evaluated by applying a probabilistic-based methodology that accounts for the involved uncertainties and investigates their significance. Three approaches to representing the outdoor climate are investigated by varying the method and time duration. The temperature-dependent thermal conductivity of the insulation material is measured, and subsequently, a stochastic model is proposed to represent this property. Deficiencies, considering penetration of wind-driven rain, are accounted for and represented by moisture sources in a parametric way. A sensitivity analysis is performed to identify the influential parameters, and subsequently, simplify the system representation by reducing the number of input variables in order to reduce the computational efforts. The timber ventilated walls show satisfactory performance to withstand biodeterioration unless potential deficiencies are considered. The study demonstrates that the probabilistic-based methodology enables a more systematic approach to evaluate wall constructions. It accounts for the involved uncertainties, provides a clear association of the microbial growth to its likelihood, and enables the identification and significance of the dominant parameters; hence, it delivers a more comprehensive conclusion regarding the performance of constructions.

A framework for calibrating the reliability elements in simplified semi-probabilistic design safety formats is presented. The objective of calibration is to minimize the increase of construction costs, compared to the non-simplified safety format, without reducing the level of structural safety. The framework is utilized for calibrating two simplified safety formats which aim at reducing the number of load combinations relevant in structural timber design. In fact, the load-duration effect makes the design of timber structures more demanding since a larger number of load combinations need to be considered compared with other construction materials. This is the authors' manuscript to the article (preprint).

This paper presents a systematic literature review about the development of criteria and models representing mould growth in wood-based materials. First, results from experimental research regarding factors governing mould growth are discussed; afterwards, they are used to analyse the comprehensiveness of current mould models. The review shows substantial discrepancies between criteria reported for mould growth. Moreover, mould models differ with respect to governing factors and their interrelations, applied methodology, experimental set-ups and nutrients, and how they express mould. Lastly, this paper proposes solutions that account for or reduce uncertainties related to the representation and design against mould occurrence.

A critical analysis of the hysteresis models of wooden connections has led to an alternative analytical formulation of the pinching phenomenon. Starting from the generalized Bouc-Wen model,...

Reinforced concrete structures constitute an essential part of the building infrastructure. This infrastructure is aging, and a large number of structures will exceed the prescribed service period in the near future. The aging of concrete structures is often accompanied by corresponding deterioration mechanisms. One of the major deterioration mechanisms is the corrosion of the reinforcing steel, caused by chloride ions and carbon dioxide exposure. Here, a generic framework for the stochastic modeling of reinforced concrete deterioration caused by corrosion is presented. This framework couples existing probabilistic models for chloride and carbonation initiation with models for the propagation and consequences of corrosion. For this purpose, a combination of structural reliability analysis and Bayesian networks is used to estimate the probability of failure of a reinforced concrete structure. This approach allows the calculation of probabilities of rare events for simple structures in an efficient and consistent way to update the model with new information from measurements, monitoring and inspection results. The generic framework enables a holistic view of the current service life models. Corresponding sensitivity studies, finding optimal decisions for treating deteriorated reinforced concrete structures and temporal changes of structures can also be represented and analyzed within this framework.

Assuming given corrosion states this paper studies the effect of interference of corrosion pits on adjacent rebars on the probability of bending failure of a corroded reinforced concrete beam. Spatial distribution of localised corrosion along a beam is considered in the analyses. The probability of failure is estimated using Monte Carlo simulation. Uncertainties in material properties, geometry, loads, and corrosion damage are taken into account. Statistical data for the extent and location of corrosion is taken from literature and utilized in order to calibrate parameters of corresponding probability distribution functions. Results show that considering possible interference of localised corrosion has substantial influence on the estimated probability of failure. The results are compared with results from two practical methods which appeared not always to be conservative.

A hierarchical model for the variability of material properties in ready‐mixed concrete is formulated. The model distinguishes between variation on the batch, recipe, plant, producer, durability class, strength class, and regional standard level. By considering Bayesian inference and maximum likelihood estimators, the contributions from the different hierarchical levels to the variability can be estimated. The methodology is demonstrated by considering more than 14,000 compressive strength recordings from Norwegian ready‐mixed concrete plants. The results suggest that the compressive cube strength of lab‐cured specimens can be represented by a log‐normally distributed variable with mean 1.28fck,cube and coefficient of variation Vc,cube=0.13. Prior parameters for Bayesian updating are given for a range of strength and durability classes. The application of the results is demonstrated in two examples. Since the durability class gives a required maximum water–binder ratio, and the strength of the concrete is governed by the water–binder ratio, the durability class introduces a strength potential if the concrete is subject to strict durability requirements and low‐strength requirements. It is suggested that the designer should specify a strength class that utilizes this strength potential, and it is expected that a closer collaboration between the designer, contractor, and producer will result in improved concrete specifications. This is the peer reviewed version of an article, which has been published in final form at [https://doi.org/10.1002/suco.201700950]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

The design of cross laminated timber (CLT) structures is not included in the current version of European structural timber design standards of EN 1995 (Eurocode 5, EC 5). Due to the increasing importance of CLT, in different applications such as complete wall or floor elements as well as girders, it is one of the main goals of the currently ongoing revision of EC 5 to provide design principles for CLT structures. In the present paper some general aspects, relevant for the implementation of CLT in European standards in order to be consistent with the general philosophy of the Eurocodes are summarized and discussed. The differences between standard test specimens and structural components as well as the uncertainties related to the production procedure of CLT and the non-standardized test procedure are discussed. An investigation of 12 different test series from five different producers clearly indicates a large variation between different production series. Based on the investigation from the test series a reliability analysis is performed. The results indicate that the same partial safety factor as recommended for glued laminated timber (GLT) is appropriate in order to achieve an acceptable reliability. However, the analysis also indicates the potential for a smaller partial safety factor in the future, in case that the production of CLT is standardized and appropriate standardized test methods for the individual material properties exist.

Connections with metal dowel-type fasteners are important details in timber construction, connecting single members and elements to larger structures. The load-carrying capacity can be described by different failure modes of the fasteners and in the surrounding timber. These failure modes show a dependency on different dimensions and material properties. The failure can be classified into brittle and ductile failure modes based on the deformation capacity. The limited deformation capacity of the brittle failure modes has an impact on the load-carrying capacity of the entire connection with multiple fasteners. The present study takes a critical appraisal of load-carrying capacity and deformation capacity of timber connections and the implementation of their design in the Eurocode 5. By aiming for the ductile failure modes with plastic deformation of the fasteners in the design of the connection, high load-carrying capacities and high reliability can be achieved. For brittle failure modes the reduced resistance and the reduced reliability should be accounted for, especially for connections with multiple fasteners.

Predicting mould growth on facade constructions during design is important for preventing financial loss, and ensuring a healthy and comfortable indoor environment. Uncertainties in predicting mould growth are related to the representation of the biological phenomenon, the climate exposure and the material uncertainties. This paper proposes a probabilistic-based methodology that assesses the performance of facade constructions against mould growth and accounts for the aforementioned uncertainties. A comprehensive representation of mould growth is ensured by integrating several mould models in a combined outcome. This approach enables a more comprehensible and useful illustration between continuous mould growth intensities and their corresponding likelihoods. The outdoor climate exposure is represented by stochastic models derived by real time-series analysis according to autoregressive–moving-average models. The methodology is applied to investigate the influence of several parameters and the performance of several construction assemblies. This paper proposes a method to evaluate the facade performance that can facilitate reliability-based design and optimisation of facade construction.

This paper systematically reviews mould models that are applicable to wood-based materials. Both similarities and differences are observed with respect to governing factors and their interrelations, methodology, experimental set-ups, substrate and extensiveness, and how the result is communicated. Therefore, a generic framework, representing the general computation procedure of all models, is developed considering the factors that govern mould behaviour. This framework, adapted to each model, is used to structure, evaluate and compare current models. This outline supplemented with a comparison table, revealing the models’ extensiveness and differences, establishes a basis to ensure better adequate application of the selected mould model for the case at handd © 2017 The Author(s). Published by Elsevier Ltd.. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

In order to make non-linear finite element analyses applicable during assessment of the global resistance of large concrete structures, there is need for a solution strategy with a low modelling uncertainty. A solution strategy comprises choices regarding force equilibrium, kinematic compatibility and constitutive relations. Relatively large solid finite elements and a fully triaxial material model for concrete were used in the present work. Bayesian inference was applied to results from 38 benchmark analyses. The results indicated that the modelling uncertainty could be represented as a log-normally distributed random variable with mean 1.10 and standard deviation of 0.12. A new method for characterizing the failure mode was developed. The results indicated that the physical uncertainties influenced the estimated parameters of the modelling uncertainty, and that this should be considered when other uncertainties are included in a reliability assessment. © 2016 Elsevier Ltd. This is the authors' accepted and refereed manuscript to the article, locked until 24 September 2018 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

This paper applies a probabilistic-based approach as a methodology to analyze and compare the mould growth computations’ results from three different mould models. This approach, instead of the conventional deterministic ones, offers the advantage of accounting for uncertainties concerning prediction of mould growth. The results are able to demonstrate more realistic and conclusive outcomes that can be applicable to real-life situations. © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC-BY-NC-ND 4.0 license (http://creativecommons.org/licenses/by-nc-nd/4.0/)