Reliability Index Values Research Articles

Probabilistic-based structural assessment of a historic stone arch bridge

A probabilistic analysis approach for reliability-based assessment of masonry arch bridges is presented in this work. The methodology is tested on a medieval in-service construction located in Galicia, northwest of Spain. To estimate its ultimate load-carrying capacity, two different numerical approaches are employed; a three-dimensional non-linear finite element model and a two-dimensional rigid blocks limit analysis model. Aiming to alleviate the computational burden associated with the probabilistic analysis procedure, a surrogate modelling strategy is adopted. A complete understanding of the influence of model input parameters on the limit load of the structure is attained through the employment of global variance-based sensitivity analysis. The reliability assessment procedure is subsequently carried out, allowing to estimate the bridge failure probability. A difference of approximately 33% is obtained between the reliability index values drawn from both structural modelling strategies, so revealing the key role played by transversal effects on the strength capacity of masonry arch bridges. The proposed probabilistic assessment framework might be deemed as a useful tool, from which more reliable and objective information about the actual safety condition of existing masonry arch bridges can be derived, taking advantage of readily available numerical tools, but still demanding an affordable computational effort.

AN EXPLORATORY FACTOR ANALYSIS (EFA) OF BUILDING INFORMATION MODELLING USES TOWARDS BIM ADOPTION FOR BIM-BASED PROJECTS: CONTRACTORS PERSPECTIVE

Building Information Modelling (BIM) is a modelling technology that is associated with a set of processes to produce, communicate, and analyse digital information in a construction life-cycle. BIM is important for various stakeholders including contractors to adopt in order to boost project performance. However, the previous report showed that the adoption of BIM among contractors is still low compared to other stakeholders. This is because the contractors have no profound understanding of BIM and its requirements. Hence, the purpose of this paper is to determine the uses of BIM from the contractors’ perspective by adopting BIM from the planning phase to the construction phase as well as to determine the reliability and validity of the research instrument. A component questionnaire on Building Information Modelling (BIM) had been developed to determine the uses of BIM among contractors in Malaysia. This study was conducted in Selangor and Kuala Lumpur, which involved 100 respondents, in order to affirm the development of valid and reliable instrument. The reliability test and Exploratory Factor Analysis (EFA) were used to measure the instrument to produce an empirical verification of the validity and reliability of the questionnaires. Literature search and a pilot study on contractors involved in BIM-based projects were carried out from which the appropriate items were extracted. From these, twenty (20) items remained and were to be completed in the study: fourteen (14) items were BIM uses from the planning to the designing phase and six (6) items were BIM uses in the construction phase. The fourteen (14) items used to measure from the planning to the design phase comprised existing condition, cost estimation, phase planning, programming, site analysis, design review, design authoring, structural analysis, lighting analysis, energy analysis, mechanical analysis, other engineering analysis, sustainability evaluation (LEED), and code validation. Meanwhile, six (6) BIM uses for the construction phase consisted of 3D coordination, site utilizing planning, construction system design, digital fabrication, 3D control and planning, and record model. All twenty (20) items had high reliability index value, which was between 0.7 and 0.8. Accordingly, the factor analysis outcome resulted in two (2) components, obtained with 40.938% of cumulative variance, while the factor loading for each component ranged from 0.5 to 0.7, reflecting the dimension of the two (2) components. Hence, the result obtained proved that the instrument of this study had high reliability and validity.

The methodology of assigning the reliability index β to determine the safety of structural steel constructions at all operational phases

In order to assess the operational safety of steel constructions, the paper analyzes the principles of calculating the safety of structural steel constructions with consideration for the reliability index β at all phases of constructions operation and the design fundamentals of the reliability index β for both new constructions (at the design stage) and structural steel constructions in the conditions of the long-term operation.The task of safety and reliability calculations, first of all, consists in assigning normalized safety parameter values, i.e. normalizing the reliability index, the value of which should be strictly related to the consequence classes (CC), which are determining for setting the reliability coefficients for further calculations while designing the constructions.The article considers the calculation values β of the reliability index for constructions operated beyond the time limit for operation, with accumulated defects and damages. To improve the mechanism for calculating the reliability index value for the constructions operated beyond the maximum operating limit, with accumulated defects and damages, several tasks were set to determine such values β of the reliability index below which the construction is no longer considered to be operational and to define the reliability index values β for possible performance of renovation works (reconstruction, refurbishment) to strengthen and extend the remaining structural lifetime.Thus, emphasizing all of the aforementioned, the main conclusions to the article should be specified: at the stage of solving the issue of calculating the reliability index for structures being operated over the projected service life, with damages and initial defects accumulated during the operation period, it is required to perform their review and determine two main criteria for solving the issue of determining the reliability index, namely: to set such values of the reliability index below which the structure will be no longer operational, to define and set such values of the reliability index at which it is possible to carry out renovation works on steel structures, their reconstruction or repair. Considering the possibility of changing the reliability index compared to a new structure, given that the residual service life may be shorter than the design one, taking into account the economic factors and factors of probability of losing a person’s life, setting of such reliability index values is necessary for further possibility of the service life extension of a structure and determination of its residual life.

Comparative Study of Structural Reliability Assessment Methods for Offshore Wind Turbine Jacket Support Structures

Offshore wind turbines (OWTs) are deployed in harsh environments often characterized by highly stochastic loads and resistance properties, thus necessitating the need for structural reliability assessment (SRA) to account for such uncertainties systematically. In this work, the SRA of an OWT jacket-type support structure is conducted, applying two stochastic methods to predict the safety level of the structure considering various design constraints. The first method refers to a commercial finite element analysis (FEA) package (DesignXplorer© from ANSYS) which employs direct simulations and the six sigma analysis function applying Latin hypercube sampling (LHS) to predict the probability of failure. The second method develops a non-intrusive formulation which maps the response of the structure through a finite number of simulations to develop a response surface, and then employs first-order reliability methods (FORM) to evaluate the reliability index and, subsequently, the probability of failure. In this analysis, five design constraints were considered: stress, fatigue, deformation, buckling, and vibration. The two methods were applied to a baseline 10-MW OWT jacket-type support structure to identify critical components. The results revealed that, for the inherent stochastic conditions, the structural components can safely withstand such conditions, as the reliability index values were found acceptable when compared with allowable values from design standards. The reliability assessment results revealed that the fatigue performance is the design-driving criterion for structural components of OWT support structures. While there was good agreement in the safety index values predicted by both methods, a limitation of the direct simulation method is in its requirement for a prohibitively large number of simulations to estimate the very low probabilities of failure in the deformation and buckling constraint cases. This limitation can be overcome through the non-intrusive formulation presented in this work.

Optimization design of gear reducer based on multi-attribute decision making and reliability sensitivity

In order to solve the complexity and implicitness of lightweight optimization of the gear reducer, this paper constructs a multi-objective reliability optimization mathematical model of the gear reducer. and to obtain multi-objective Pareto solution, artificial intelligence algorithm is used to optimize structural parameters. Then, through repeatedly changing the structural parameters of the reducer, the experimental simulation analysis is carried out to obtain the maximum working stress. Based on the idea of the weight reduction and miniaturization, the stress state and reliability index values under different structural parameters are compared and analyzed. In order to determine the optimal solution of structural parameters, multi-attribute decision theory is used to determine the solution. Finally, in order to effectively reveal the inherent variation of attribute values and decision results and quantitatively reflect the impact of various structural parameters on system reliability, reliability sensitivity analysis of the gear reducer is carried out by the response surface-Monte Carlo and DPS methods. Thereby, an optimized structure that meets the safety reliability and the appropriate economy is obtained, and this study produces a balanced and improved optimized design that is coordinated with cost, quality, volume, safety and stability.

The Effect of Reliability Index Values on Resulting Reliability-Based Topology Optimization Configurations: Numerical Validation by Shape Optimization

Introduction. The classical topology optimization leads to structural type and general layout prediction and gives a rough description of the shape of both the external and internal structure boundaries. However, Reliability-Based Topology Optimization (RBTO) model produces multiple reliability-based topologies with high levels of performance. The aim of this work is to study the effect of reliability changes on the obtained topologies. Materials and Methods. The developed Gradient-Based Method (GBM) has been used efficiently as a general method for several applications (statics and dynamics). When considering several reliability levels, several topologies can be obtained. In order to compare the resulting topologies, a shape optimization is considered as a detailed design aspect. Results. Numerical applications are carried out on an MBB (Messerschmitt-Bölkow-Blohm) beam subjected to a distributed load. The DTO model is carried out without consideration of reliability concept. However, for the RBTO model, an interval of reliability is considered that produces several topologies. Here, the randomness is applied on geometry and material parameters. The application of the shape optimization algorithm leads to reduced structural volumes when increasing the reliability levels. Discussion and Conclusion. In addition to its simplified implementation, the developed GBM strategy can be considered as a generative tool to provide the designer with several solutions. The shape optimization is considered as a numerical validation of the importance of the different resulting RBTO layouts.

Reliability Analysis and Numerical Simulation of Reinforced Concrete Structure in Port Engineering

Mu, Z.; Mu, H.; Zhang, H.G., and Li, Z.-P., 2019. Reliability analysis and numerical simulation of reinforced concrete structure in port engineering. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 347–351. Coconut Creek (Florida), ISSN 0749-0208.In addition to the normal loss and damage during the service period, the port engineering facilities are also affected by harsh environments such as water erosion, wave erosion, atmospheric corrosion and freezing and thawing. Therefore, it is very important to analyze the reliability of reinforced concrete structures. The reliability analysis of reinforced concrete members is actually based on the fact that the statistical characteristics of the existing loads and structural resistance are known, and the reliability index value of the members is determined through specific calculations to understand the failure probability. Taking the reinforced concrete frame column as an example, the finite element model is established by the simulation software to simulate and analyze the compression of the port structure under the action of ship impact force, ship system force, doorsill machine load, self-weight load and water flow force, the reliability of shear and bending capacity, the analysis results provide the basis for engineering construction and followup research.

Investigation of the Adequacy of Bridge Design Loads in Pakistan

Weight, configuration, and volume of traffic vary from country to country. But, in developing countries like Pakistan, bridges are designed based on codes of developed countries. Hence, these bridges may not have desired safety level. In this study, safety levels of three sample bridges has been investigated in terms of structural reliability index. Live load effects (shear and moments) in girders were determined using weigh-in-motion data (WIM) and were extrapolated to 75 years using non-parametric fit. Two live load models and two strengths, required by 1967 Pakistan Code of Practice for Highway Bridges (PHB Design-Case) and that required by the 2012 AASHTO LRFD Bridge Design Specifications (AASHTO Design-Case) were used in reliability analysis. It is found that actual trucks produce moment and shear in girders 11 to 45 percent higher than live load models of PHB and AASHTO design cases. Values of structural reliability indices vary from 1.25 to 2.50 and from 2.45 to 3.15 for PHB and AASHTO design cases, respectively, and are less than the target reliability index value of 3.50 used in the design codes as benchmark. It is revealed after the research that bridges in Pakistan may not have desired safety level, and current live load models may not be the true representation of service-level truck traffic.

Research on reasonable value of target reliability index for steel main girder of cable-stayed bridge considering durability

This article studies the relationship between the target reliability index and the design life of the main girder of a long-span cable-stayed bridge to provide a theoretical basis for the design of steel girders for such an application. The changes of the bending section modulus under atmospheric corrosion and the residual ultimate stress of the section of a steel box girder under alternating loads are discussed. A resistance attenuation function for a steel girder of a cable-stayed bridge to predict the resistance change of a steel box girder over the service period is proposed, and the change characteristics of the time-varying reliability index of a steel box girder of a cable-stayed bridge are studied. By analysing the relationship between the time-varying reliability index and the evaluating benchmark value of the reliability index, the time point of maintenance and reinforcement is predicted. Based on the change over time of the difference between the time-varying reliability index and the evaluating benchmark value of the reliability index, the relation function between the target reliability index and the service lifetime of a bridge considering resistance attenuation are provided.

Reliability optimization of electrical distribution systems considering expenditures on maintenance and customer interruptions

<p>In this paper, a methodology is proposed which shows enhancement of reliability by optimizing total reliability cost of electrical distribution systems. The total reliability cost consists of cost incurred by utility and customers both. An objective function in terms of failure rates and repair times i.e. primary reliability indices has been formulated which depicts both these costs . Hence, optimization of the objective function will give a balance between these costs with optimized values of primary reliability indices. This optimization has been done considering the constraints of achieving customer and energy based reliability indices below threshold/target values. The methodology has been applied on Roy Billinton Test System- Bus 2 (RBTS-2). The problem has been solved by applying Flower Pollination (FP) algorithm. A comparison has been made with the results obtained by Differential evolution (DE) algorithm also for the system considered.</p>

Validation of technical and vocational teachers’ competency evaluation instrument using the rasch model

This pilot study was conducted with the aim to validate the instrument used in evaluating the competency of teachers in the field of technical and vocational education. This instrument consists of 45 items and is administered to 53 teachers from a selected vocational college. The Rasch Model with the help of the Winstep Version 3.72.3 software has been used in this study for the purpose of checking the functionality of the item and the validity of the instrument. An analysis has been made based on the suitability of items in measuring the construct, item and person reliability and separation index, polarity and residual correlation value. The Rasch analysis showed that the item reliability was valued at 0.92 while the person reliability valued at 0.96 with their item MNSQ between overfit (<0.6) and misfit (>1.4). Based on the findings, there are three items that were dropped because of failing to meet the inspection criteria. The finalized instrument consists of 42 items, in which it is suitable for evaluating the four constructs in the competency evauation of technical and vocational teachers in vocational colleges.

Probabilistic Characterization of Rock Mass from Limited Laboratory Tests and Field Data: Associated Reliability Analysis and Its Interpretation

Probabilistic methods are the most efficient methods to account for different types of uncertainties encountered in the estimated rock properties required for the stability analysis of rock slopes and tunnels. These methods require estimation of various parameters of probability distributions like mean, standard deviation (SD) and distributions types of rock properties, which requires large amount of data from laboratory and field investigations. However, in rock mechanics, the data available on rock properties for a project are often limited since the extents of projects are usually large and the test data are minimal due to cost constraints. Due to the unavailability of adequate test data, parameters (mean and SD) of probability distributions of rock properties themselves contain uncertainties. Since traditional reliability analysis uses these uncertain parameters (mean and SD) of probability distributions of rock properties, they may give incorrect estimation of the reliability of rock slope stability. This paper presents a method to overcome this limitation of traditional reliability analysis and outlines a new approach of rock mass characterization for the cases with limited data. This approach uses Sobol’s global sensitivity analysis and bootstrap method coupled with augmented radial basis function based response surface. This method is capable of handling the uncertainties in the parameters (mean and SD) of probability distributions of rock properties and can include their effect in the stability estimates of rock slopes. The proposed method is more practical and efficient, since it considers uncertainty in the statistical parameters of most commonly and easily available rock properties, i.e. uniaxial compressive strength and Geological Strength Index. Further, computational effort involved in the reliability analysis of rock slopes of large dimensions is comparatively smaller in this method. Present study also demonstrates this method through reliability analysis of a large rock slope of an open pit gold mine in Karnataka region of India. Results are compared with the results from traditional reliability analysis to highlight the advantages of the proposed method. It is observed that uncertainties in probability distribution type and its parameters (mean and SD) of rock properties have considerable effect on the estimated reliability index of the rock slope and hence traditional reliability methods based on the parameters of probability distributions estimated using limited data can make incorrect estimation of rock slope stability. Further, stability of the rock slope determined from proposed approach based on bootstrap method is represented by confidence interval of reliability index instead of a fixed value of reliability index as in traditional methods, providing more realistic estimates of rock slope stability.

RELIABILITY BASED DESIGN OF THE ROCK SIDE SLOPE FOR MIDDLE PLATEAU IN MOKATTAM AREA CONSIDERING OPTIMAL COST VALUE

Design solutions for the problems of the rock side slope stability, in general, are one of themost critical issues in geo-technical engineering profession, due to the fact that the values ofrock parameters are difficult to be considered reliable, because of the uncertainties existing ingeological system. This research aims to introduce reliability based design of the rock sideslope stability considering optimal cost value. The idea for obtaining the optimal cost valuedepends on two main critical parameters. These two main critical parameters are uni-axialcompressive strength (U.C.S) and geologic strength index (G.S.I). Both of them have beencalculated based on statistical calculations of mean and standard deviations. A strengthcriterion is needed to characterize the rockmass in geotechnical engineering. There are threecriteria are used to describe the strength of a material: bilinear Mohr-Coulomb criterion,nonlinear Hoek-Brown criterion and special spalling criterion must be used in special case ofmassive, brittle rocks. Nonlinear Hoek-Brown criterion has been used in this study; becauseof some limitations associated with the use of the Mohr-Coulomb criterion. RocData programhave been utilized for obtaining the Hoek-Brown parameters (m, s), Slide program has beenemployed for calculating the reliability index, factor of safety and probability of failure foreach case study for upper plateau in Mokattam area. The concept of design is based on thenecessity of using reinforcement. If the design of using rock parameters is safe and reliable,there is no need for reinforcement; otherwise design of rock bolts should be used as a supportsystem to improve reliability and factor of safety. The current simplified method has beenutilized to consider the cost of failure to find the optimal length of support and optimalreliability index. The study concluded that the suggested technique of nonlinear Hoek BrownCriterion is effective for helping the designer in finding the optimal length of support thatmeets the optimal reliability index and optimal cost value for two main critical parameters.

The structural reliability analysis using explicit neural state functions

The present study considers the problems of stability and reliability of spatial truss susceptible to stability loss from the condition of node snapping. In the reliability analysis of structure, uncertain parameters, such us load magnitudes, cross-sectional area, modulus of elasticity are represented by random variables. Random variables are not correlated. The criterion of structural failure is expressed by the condition of non-exceeding the admissible load multiplier. In the performed analyses explicit form of the random variables function were used. To formulate explicit limit state functions the neural networks is used. In the paper only the time independent component reliability analysis problems are considered. The NUMPRESS software, created at the IFTR PAS, was used in the reliability analysis. The Hasofer-Lind index in conjunction with transformation method in the FORM was used as a reliability measure. The primary research method is the FORM method. In order to verify the correctness of the calculation SORM and Monte Carlo methods are used. The values of reliability index for different descriptions of mathematical model of the structure were determined. The sensitivity of reliability index to the random variables is defined.

Метод оценки показателя достоверности выходных данных, подготавливаемых средствами автоматизированной системы подготовки данных полета летательных аппаратов

Methods for solving the problem of ensuring the reliability of information have been considered in the works of many domestic and foreign scientists. Nevertheless, when performing some tasks of automation of the activity of the personnel of the governing bodies, it may be difficult to calculate the required value of data reliability due to the complexity of the algorithms for calculating the confidence indicator and difficulties in obtaining adequate input data. A new method for assessing the reliability of aircraft flight data is considered on the basis of the special representation of the data preparing process as a serial connection of technological sections in time and calculating the reliability indicators for each element of the technological section and the technological section as a whole. The structure of a typical technological section includes a documentalist, an operator, hardware, software and a procedure for correcting erroneous data detected by the control procedure. The use of such a process model allows obtaining a simple recurrent algorithm for estimating the data reliability index for any technological section using the reliability index values for the previous technology sections. Having determined the probabilities of data distortion and the time of operation performing by elements of the technological section, it is possible to calculate the values of similar indicators for each elementary data preparation process and the system as a whole. An elementary data preparation process, the essence of which is to update the system database is considered as an example. This stage is the most representative one, since all elements of the technological section are involved in its implementation

Rock Mass Characterization and Stability Evaluation of Mount Rushmore National Memorial, Keystone, South Dakota

AbstractThe purpose of this study was to characterize the rock mass at Mount Rushmore National Memorial (MORU) and to evaluate the stability of the presidential sculptures. The sculptures are carved in granite, but quartz-mica schist and minor outcrops of pegmatite are also present within the site area. We divided the MORU area into four “regions” to collect discontinuity data. Since the sculptures were not accessible during this study, we used light detection and ranging (LiDAR) data and Split-FX software to determine the orientations of both the discontinuities and the slopes on the sculptures. The rock mass characterization results, using both the Rock Mass Rating system and the Q-system, indicate the granite, schist, and pegmatite classify as fair to good rock. Kinematic analysis results indicate that the potential for planar, wedge, and toppling failures exists for various slopes on each of the sculptures. The factor of safety (FS) values against planar and wedge sliding, ignoring cohesion, range from 0.1 to 0.8 and from 0.2 to 1.3, respectively. Since failures have not been observed at the memorial, we back-calculated the amount of cohesion required to raise the FS values to >1. The back-calculation results show that both cohesion and friction contribute to stability of the sculptures. Using the Slide program, we performed an overall slope probabilistic analysis for the slopes on which the MORU sculptures are located. The analysis determines the mean factor of safety (FSM), reliability index (RI), and probability of failure (PF) for the slopes. For the static condition, the analysis resulted in FSM, RI, and PF values ranging from 3.3 to 4.5 percent, 3.3 to 7.8 percent, and 0 percent, respectively. With a seismic load coefficient of 0.14 applied to the slopes, the corresponding values were: 2.6 to 4.1 percent, 2.9 to 4.7 percent, and 0 percent. For both the static and seismic conditions, the results indicate that, overall, the slopes of the sculptures are stable.

ANALISIS KEANDALAN DAN SUSUT DAYA PENYULANG TABANAN SETELAH REKONFIGURASI

The need for electricity in this global era is increasing, so that a more reliable electrical system is needed. A reliable system cannot be separated from interference, so there needs to be a system reliability analysis and power loss to the feeder by configuring the network. This research was conducted to find the reliability index value in the form of interference frequency and duration of interference (SAIFI and SAIDI). In one Tabanan feeder the results obtained exceed the standard so reconfiguration is performed Based on the analysis obtained before reconfiguration, the reliability index for SAIFI is 6,7456 (failure / year) and SAIDI is 11,4767 (hour / year) and power loss by 6,27 %. After reconfiguration of Tabanan feeder, the reliability index was better, for SAIFI is 5.2475 (disturbance / year) and SAIDI is 9,8798 (hour / year), the power loss was 2.82%. Sanggulan feeder is a new feeder reconfiguration result from Tabanan feeder, where the analysis was carried out to find out the reliability index of Sanggulan feeder, it was obtained the SAIFI value of 4.5753 (disturbance / year) and SAIDI of 9.5297 (hour / year) and power loss of 4,80%.

Reliability-based design optimization analysis of a piezoelectric engine

In this paper, we study extensions of the RBDO of the piezoelectric engines with travelling wave taking into account the dynamic contact between the different components (stator and rotor). Generally, the life of these engines is limited by important abrasion of the different components. So, the notion of random variables and the risk of failure must be integrated in the mechanical analysis to ensure the good working of the system. The numerical treatment of the dynamic contact inside the motor is presented with the good choice of relaxation factors. The RBDO is often formulated as a minimization of the initial structural cost under constraints imposed on the values of elemental reliability indices corresponding to various limit states. The classical RBDO leads to high computing time and weak convergence, but a hybrid method has been proposed to overcame these two drawbacks. The efficiency of the hybrid method has been demonstrated on static and dynamic cases with extension to the variability of the probabilistic model. We propose two methods: the dynamic hybrid method and the frequencies hybrid method as extension of the improved hybrid method presented in further works.

Evaluation of the psychometric properties of the Brazilian version of the Oral Health Literacy Assessment in Spanish and development of a shortened form of the instrument.

ObjectiveThe objective of this study was to investigate the psychometric properties of the Oral Health Literacy Assessment in Spanish (OHLA-S) for the Brazilian-Portuguese language using robust analysis and with the results disclose possibilities to develop a shorter and more valid instrument.MethodsOHLA-S is an oral health literacy instrument comprising a word recognition section and a comprehension section. It consists of 24 dental words. It was translated into the Brazilian-Portuguese language (OHLA-B) and its psychometric properties were evaluated in a random sample of 250 adults aged 20–59 years. To assess the dimensionality and factor structure were tested by means of Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). Reliability was assessed using two indicators: Cronbach's alpha and McDonald’s Omega.ResultsEFA and CFA demonstrated that the OHLA-B with 24 items did not present an adequate adjustment of the model, compromising its validity. In addition, reliability values at 0.50 for Cronbach's alpha and 0.67 for McDonald's omega were below the minimum acceptable rate of 0.70. As no support was found for the original structure, we decided to proceed with the withdrawal of individual items and successive reanalysis of the model until the indicators were adjusted in a shorter instrument. A new structure with 15 items produced an instrument with two dimensions and a better goodness of fit than the original instrument. The Alpha and Omega reliability index values increased to 0.83 and 0.80, respectively, and all scores were better in the OLHA-B with 15 items than in the instrument with 24 items.ConclusionOLHA-B with the original structure composed by 24 items did not show acceptable construct validity. The shorter version with 15 items showed more promising results for assessing oral health literacy levels in the Brazilian population.

A comparative study of target reliability index derivation for reinforced concrete structures governed by serviceability limit state

Typical design of reinforced concrete structures is governed by the ultimate limit state (ULS), while serviceability limit state (SLS) is checked. The target reliability index for ULS is recommended based on cost optimization and back calibration of existing practice. Many design cases, such as prestressed concrete, are, however, governed by serviceability conditions and the background for the current recommendations for target reliability index of irreversible SLS as provided by ISO 2394 is unclear. This contribution reviews previously developed generalized framework for determination of SLS target reliability by taking into account a cost ratio and statistical parameters of action‐resistance variable. Target reliability index βt,SLS can be then obtained from the previously introduced table with a minimum effort. A case‐specific approach to the cost optimization with FORM analysis is introduced in order to validate the results of the generic approach. It is found that there is a discrepancy in terms of the obtained value of target reliability index. This can be attributed to the influence of the decision parameter d in the cost optimization process. It affects the probability of failure pf(d) at the different rates for different formulations of SLSs. The nearly linear assumption in the generic formulation may not necessarily apply in other cases, and care should be taken when specifying target reliability index βt,SLS as the effectiveness of the decision parameter must be observed.