Sofia M. C. Diniz

Safety evaluation of slender high-strength concrete columns under sustained loads

A realistic analysis of the reliability of slender high-strength concrete (HSC) columns must include the long-term effects of sustained loads. In this paper, the long-term reliability of eccentrically loaded slender HSC columns under sustained loads is evaluated. The reliability of slender reinforced concrete columns representing normal-strength concrete and HSC is investigated. Since most of the variables involved in column design (material properties, geometric characteristics, loads, etc.) are random, probabilistic methods are used in the analysis. The effects of the concrete compressive strength, amount of longitudinal steel, load eccentricity, and slenderness ratio on the column reliability are investigated. It was found that all these factors have a considerable impact on the resulting column reliability.

Avaliação da segurança de vigas de alma senoidal sujeitas à flambagem lateral com torção - parte 1: requisitos básicos

There are no design standards or specifications dealing with all the phenomena involved in the structural behavior of corrugated-web beams. The development of recommendations that might express their behavior more properly, within the concepts and methods of the Theory of Reliability is therefore necessary. In this research, the safety assessment of sinusoidal-web beams for the lateral-torsioned buckling failure mode is performed. To this end, in this first part, the following basic requirements are presented: (i) proposal and validation of the calculation model; (ii) statistics of basic variables. The proposed model is based on an adaptation of the standards ANSI/AISC 360-05 (2005) and ABNT NBR 8800 (2008), in which the corrugated web is neglected on the computation of geometric properties. The statistics of basic variables were obtained from literature and measurements of the actual dimensions of sinusoidal-web shapes manufactured in Brazil.

Model uncertainty in the estimation of the resistance of circular reinforced concrete columns confined by carbon fiber reinforced polymer

Abstract Utilisation of carbon fibre-reinforced polymers (CFRP), for confinement of concrete, has proved to be a viable alternative in the strengthening of reinforced concrete (RC) columns with circular cross-sections. However, a large research effort is still necessary in order to select analytical models that properly estimate the ultimate strength and strain of RC columns confined by FRP and transversal steel (FRP-RC). Different models have been proposed, but most of the available FRP-confinement models have been validated by experimental results of cylinders of plain concrete, not taking into account the influence of longitudinal and transversal steel which occurs in the strengthening of existing RC columns. The statistical description of the ‘model error’, representing uncertainty in the prediction of column resistance, is required information in the reliability analysis of FRP-RC columns. In this study, four representative confinement models are evaluated. A comprehensive experimental database encompassing RC columns with longitudinal and transversal steel confined by CFRP is compiled from the literature. A statistical analysis is performed in order to describe the model errors associated to the estimation of ultimate stress, ξf, and ultimate strain, ξε. For the confinement models considered in this work, the coefficients of variation are in the range 0.23–0.49 (ξf) and 0.54–1.43 (ξε).

Avaliação da segurança de vigas de alma senoidal sujeitas à flambagem lateral com torção - Parte 2: análise de confiabilidade

There are no design standards or specifications dealing with all the phenomena involved in the structural behavior of corrugated-web beams. The development of recommendations that might express their behavior more properly, within the concepts and methods of the Theory of Reliability, is therefore necessary. In this research, the safety assessment of sinusoidal-web beams for the laterallytorsioned buckling failure mode is performed. In this second part, the reliability analysis of such elements, designed according to a procedure that incorporates the calculation model and the load and resistance factors, is performed. Herein, the following are presented: (i) the used reliability method; (ii) the performance functions; (iii) the reliability indexes implicit in the procedure. Based on the results, it is shown that the proposed procedure leads to reliable levels compared to those of plane-web shapes.

Probabilistic Performance Criteria for Tall Buildings Subjected to Wind

Database-assisted design (DAD) for wind loads consists of (1) using simultaneous measurements of wind-induced pressure time histories at a large number of taps on a model structure’s envelope, and (2) using those time histories to estimate the structural response in each member, both for rigid [1] and flexible buildings [2]. DAD allows the development of reliability procedures to estimate probabilities that the structure will satisfy specified performance criteria under extreme winds [3]. In this paper we review relevant material from [2] and outline such a procedure for tall, flexible buildings. The internal forces and their combinations, as they appear in design interaction formulas, are affected by climatological, micrometeorological, aerodynamic, and mechanical parameter uncertainties. The reliability procedure we propose accounts for those uncertainties and integrates information on the directional wind climate and the building’s directional aerodynamics.