From prescription to performance: international trends on concrete specifications and the Brazilian perspective

There are two types of specifications: prescriptive and performance based. The prescriptive specifications focus on materials properties, materials proportions, mixing and transporting procedures and on a variety of processes, such as placing and curing. In these specifications, the concrete desired performance it is not necessarily described. On the other hand, performance specifications stipulate what is required from the product and do not prescribe how the product should be produced. In other words, they focus on the desired performance rather than on the concrete ingredients, materials selection, proportioning or construction methods. These are the responsibility of those individuals who contractually have to comply with the specifications. In this case, con- crete is defined in terms of measurable fresh and hardened properties and durability and as there are no restrictions regarding materials and their proportions in the performance specifications, innovative solutions may be used in order to achieve the performance requirements. Currently, most concrete specifications are predominantly prescriptive with some performance requirements. Nevertheless, there is a consensus that in order to extend the service life of concrete structures, this has to be changed. This paper gives an overview of the international specifica- tions and describes the international efforts on the performance specification implementation in the concrete industry.

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Confidence interval for quantiles and percentiles

Biochemia Medica ◽

10.11613/bm.2019.010101 ◽

2018 ◽

Vol 29 (1) ◽

pp. 5-17 ◽

Cited By ~ 3

Author(s):

Cristiano Ialongo

Keyword(s):

Confidence Interval ◽

Laboratory Medicine ◽

Reference Intervals ◽

Population Parameter ◽

Statistical Tools ◽

Underlying Distribution ◽

Performance Specification ◽

Performance Specifications ◽

And Performance ◽

Sample Estimate

Quantiles and percentiles represent useful statistical tools for describing the distribution of results and deriving reference intervals and performance specification in laboratory medicine. They are commonly intended as the sample estimate of a population parameter and therefore they need to be presented with a confidence interval (CI). In this work we discuss three methods to estimate CI on quantiles and percentiles using parametric, nonparametric and resampling (bootstrap) approaches. The result of our numerical simulations is that parametric methods are always more accurate regardless of sample size when the procedure is appropriate for the distribution of results for both extreme (2.5th and 97.5th) and central (25th, 50th and 75th) percentiles and corresponding quantiles. We also show that both nonparametric and bootstrap methods suit well the CI of central percentiles that are used to derive performance specifications through quality indicators of laboratory processes whose underlying distribution is unknown.

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A New Structured Multimodel Control of Nonlinear Systems by Integrating Stability Margin and Performance

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4036069 ◽

2017 ◽

Vol 139 (9) ◽

Cited By ~ 4

Author(s):

Mahdi Ahmadi ◽

Mohammad Haeri

Keyword(s):

Nonlinear Systems ◽

Controller Design ◽

A Priori ◽

Design Procedure ◽

Stability Margin ◽

Point Tracking ◽

Performance Requirements ◽

Performance Specifications ◽

And Performance ◽

Model Redundancy

This paper deals with a new systematic multimodel controller design for nonlinear systems. The design of local controllers based on performance requirements is incorporated with the concept of local models selection as an optimization problem. Gap metric and stability margin are used as measuring tool and operation space dividing criterion, respectively. The developed method provides support to design a simple structured multiple proportional-integral (PI) controller which guarantees both robust stability and time-domain performance specifications. The main advantages of the proposed method are avoiding model redundancy, not needing a priori knowledge about system, having simple structure, and easing the implementation. To evaluate the presented multimodel controller design procedure, three benchmark nonlinear systems are studied. Both simulations and experimental results prove the effectiveness of the proposed method in set point tracking and disturbance rejection.

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Performance of performance specifications in design-build highway projects

Construction Economics and Building ◽

10.5130/ajceb.v19i2.6659 ◽

2019 ◽

Vol 19 (2) ◽

Author(s):

Jan Bröchner ◽

Johan Silfwerbrand

Keyword(s):

Project Managers ◽

Highway Projects ◽

Innovative Technologies ◽

Performance Requirements ◽

Road Surfaces ◽

Design Build ◽

Innovative Solutions ◽

Performance Specifications ◽

Technical Specifications ◽

Innovation Rate

Design-build contracts with performance-based specifications are believed to raise productivity and the innovation rate. Such specifications for highway and bridge contracts may create risks, be too detailed or difficult to verify. The purpose has been to analyse how performance-based requirements are used in Swedish design-build contracts for highway projects. How contractors are encouraged to provide innovative technologies is emphasized. Generic documents from the Swedish Transport Administration for design-build contracts have been studied, and case studies of six design-build contracts with performance-based requirements have been made. Technical specifications for these contracts have been analysed and interviews held with both client and contractor project managers. Results include that it is along the time axis that major obstacles to innovation arise. Before the contractor is able to develop innovative solutions, the initial design plan restricts the highway geometry. During construction, a mix of performance and prescriptive requirement formulations is more of a challenge than clashes between performance requirements. The client may avoid performance language, more so for bridges than road surfaces, because of concerns with efficient maintenance in the future. It is recommended that performance-based specifications should be less detailed and that a life cycle view of highway projects should support innovative technologies.

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