Implementing Snow Load Monitoring to Control Reliability of a Stadium Roof

This contribution shows how monitoring can be used to control reliability of a structure not complying with the requirements of Eurocodes. A general methodology to obtain cost-optimal decisions using limit state design, probabilistic reliability analysis and cost estimates is utilised in a full-scale case study dealing with the roof of a stadium located in Northern Italy. The results demonstrate the potential of monitoring systems and probabilistic reliability analysis to support decisions regarding safety measures such as snow removal, or temporary closure of the stadium

Partial factors for the assessment of load-bearing capacity of existing bridges

Rostoucí zatížení dopravou, stárnutí existujících mostů a nákladnost jejich modernizací zvyšují význam metod hodnocení spolehlivosti, které umožní přihlédnout k různým faktorům specifickým pro existující most. Článek vysvětluje postupy úprav dílčích součinitelů v závislosti na znalostech o materiálech a zatížení, zvolené směrné úrovni spolehlivosti a plánované zbytkové životnosti mostu. Praktický příklad ilustruje aplikaci teoretických postupůEver-increasing traffic actions, degradation of bridges and immense costs of their rehabilitations imply needs for the methods of reliability assessment that allow accounting for specific conditions of an existing bridge. The study clarifies the procedures of modifications of partial factors considering knowledge and uncertainties in materials and actions, selected target reliability and required remaining working life of the bridge. A case study indicates the applications of theoretical procedure

Uncertainty in resistance models for steel members

Resistance of steel structures is primarily dependent on material properties, geometry and uncertainties related to an applied model. While materials and geometry can be relatively well described, the uncertainties in resistance models are not yet well understood. In many cases significant efforts are spent to improve resistance models and reduce uncertainty associated with outcomes of the model. However, these achievements are then inadequately reflected in the values of partial factors. That is why the present paper clarifies a model uncertainty and its quantification. Initially a general concept of the model uncertainty is proposed. Influences affecting results obtained by tests and models and influences of actual structural conditions are overviewed. Statistical characteristics of the uncertainties in resistance of steel members are then provided. Simple engineering formulas, mostly based on the EN 1993-1-1 models, are taken into account. To facilitate practical applications, the partial factors for the model uncertainties are derived using a semiprobabilistic approac

Updating material factors for assessment of historic reinforced concrete bridge

This paper is focused on the reliability analysis of an existing reinforced concrete bridge from 1908. The load bearing capacity is assessed in accordance with valid standards using updated partial factors and the partial factors for structural design. Load bearing capacities obtained by these methods are critically compared. The application of the updated partial factors leads to 15 % higher load bearing capacity than the ordinary partial factor method used for structural design

Nejistoty smykové odolnosti železobetonových nosníků s třmínky – porovnání postupů podle EN 1992-1-1 a fib MC 2010

The submitted contribution is focused on the model uncertainty related to shear resistance of reinforced concrete beams with stirrups. Using available test results, effects of basic variables on the model uncertainty are analysed. Considering the section-oriented models provided in EN 1992-1-1 and in the new fib Model Code 2010 are critically compared. Proposed probabilistic description of the model uncertainty consists of the lognormal distribution having the mean and coefficient of variation dependent on the considered model. Strength of shear reinforcement seems to be the most important basic variable for most of the considered models.Příspěvek je zaměřen na modelové nejistoty smykové odolnosti železobetonových prvků s třmínky. S využitím dostupných experimentálních dat se porovnávají nejistoty modelů v EN 1992- 1-1 a fib Model Code 2010. Jsou identifikovány veličiny významně ovlivňující modelovou nejistotu. Teoretický popis nejistot se opírá o lognormální rozdělení s průměrem a variačním koeficientem závislým na použitém modelu. Pro většinu uvažovaných modelů je pevnost smykového vyztužení nejvýznamnější základní veličinou

Reliability and risk acceptance criteria for civil engineering structures

The specification of risk and reliability acceptance criteria is a key issue of reliability verifications of new and existing structures. Current target reliability levels in standards appear to have considerable scatter. Critical review of risk acceptance approaches to societal, economic and environmental risk indicates that an optimal design strategy is mostly dominated by economic aspects while human safety aspects need to be verified only in special cases. It is recommended to specify the target levels considering economic optimisation and the marginal life-saving costs principle, as both these approaches take into account the failure consequences and costs of safety measures

Modelové nejistoty smykové odolnosti železobetonových nosníků se smykovou výztuží podle EN 1992-1-1

The submitted contribution is focused on the model uncertainty related to shear resistance of reinforced concrete beams with special shear reinforcement considering available test results. Variation of the model uncertainty with basic variables is analysed and significant variables are identified for the section-oriented formula provided in EN 1992-1-1. Proposed probabilistic description of the model uncertainty consists of the lognormal distribution having the coefficient of variation of about 0.25 and the mean significantly varying with the strength of shear reinforcement.Příspěvek se zaměřuje na modelové nejistoty smykové odolnosti železobetonových prvků se smykovou výztuží s využitím dostupných experimentálních dat. Analyzuje se závislost modelové nejistoty na základních veličinách pro výpočet smykové únosnosti podle EN 1992-1-1. Jsou identifikovány veličiny významně ovlivňující modelovou nejistotu. Pravděpodobnostní rozdělení modelové nejistoty je lognormální s variačním koeficientem 0.25 a různými průměrnými hodnotami závislými na odolnosti smykové výztuže

Target reliability levels in present standards

The target reliability levels recommended in national and international documents vary within a broad range, while the reference to relevant costs and failure consequences is mentioned only very vaguely. In some documents the target reliability index is indicated for one or two reference periods (1 year, 50 years or life-time) without providing appropriate links to the design working life. This contribution attempts to clarify the relationship between the target reliability levels, costs of safety measures, failure consequences, reference periods and the design working lif

Implication of climate changes on design of structures

The climatic data on which the current generation of the Eurocodes are based are mostly about 20 years old, with some exceptions of recent updates at a national level. The second generation of the Eurocodes for structural design is expected to be nationally implemented within next few years and operational National Annexes should be subsequently developed and the climatic maps revised. Some models for extreme climate actions are still missing within Eurocodes including wind action effects due to non-synoptic storms, which are common in most of the world and are of increasing importance in Europe.The aim of this contribution is to analyse how the impact of anticipated changes in European climate could affect the assessment of design weather parameters, including the partial factor design approach for structures according to Eurocodes, based on current knowledge concerning projectionmodels of future climate in Europe

Reliability of existing reinforced concrete slabs exposed to punching shear

Selected standardised models for the verification of punching shear in reinforced concrete structures are applied for the probabilistic assessment of their reliability level. It appears that the models given in EN 1992-1-1 and prEN 1992-1-1 lead to more realistic estimates of the reliability level of existing reinforced concrete members with respect to punching shear than the models recommended in some national codes. The controlled perimeter has significant influence on the results and should be harmonized in prescriptive documents