78 research outputs found
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
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