Maximiliano Malite

Reliability-based evaluation of design guidelines for cold-formed steel-concrete composite beams

This paper presents an analysis of design guidelines for steel-concrete composite beams, formed by concrete-filled cold-formed steel sections. The study is based on experimental results for connector resistance (push-out) and for four full-scale beam bending tests. The accuracy of analytical design equations is evaluated by comparing their predictions with experimental results. Model bias and model uncertainty of analytical design equations are evaluated. The uncertainty in design variables (steel and concrete resistance, dead and live loads, model errors) is taken into account, and reliability index of code-compliant beams is evaluated. Results show that the models for shear connector and for beam bending resistance are fairly accurate, and represent very little contribution to problem uncertainty and failure probabilities. Results show that for practical beam lengths, full material interaction is guaranteed, and failure is dominated by bending. Reliability indexes of the order of 2.2 to 2.8 are obtained, reflecting reliability of the design procedures studied. These values are low, in comparison to target reliability levels of 3.0 used in code calibration, and should be interpreted carefully in future code revisions.

Bolted Connections in Cold-Formed Steel: Reliability Analysis for Rupture in Net Section

AbstractThis article presents 93 unpublished experimental results for rupture in the net section of bolted connections in cold-formed steel angles and channels. The article includes a study of the strength reduction coefficient in order to account for the shear lag effect. Predictions of connection strength by Brazilian and American design codes are considered. By comparing experimental results with design code predictions, model error (professional factor) statistics are evaluated. Model errors are incorporated in reliability analyses of typical connections to investigate their effects on connection safety. It is shown in the article that model errors have a significant impact on connection safety. Consideration of model errors leads to significant reductions in reliability indices, which are found to be less than the recommended target reliability levels. The model error statistics obtained herein are used to find the resistance factors that would be required to achieve the target reliability index in t...

Estabilidade de cantoneiras de aço formadas a frio submetidas à compressão

The objective of this paper is to examine the stability and strength of concentrically loaded cold-formed steel angles as determined by (i) numerical methods, (ii) experiment, (iii) effective width and (iv) Direct Strength based design methods, in which angles are not pre-qualified sections. The elastic stability of cold-formed steel angle columns is examined primarily with the finite strip method to show that the coincident local-plate/global-torsion mode has some important behavior when multiple buckling half-wavelengths are considered along the length. A series of tests on single and double angles are detailed and the results used to examine existing design methods. The results indicate that the design practice of ignoring local/torsion buckling as a global mode and only considering it as a local mode may not be conservative in some circumstances.

MODELOS NUMÉRICOS DE PERFIS DE AÇO FORMADOS A FRIO COMPRIMIDOS: ÊNFASE ÀS IMPERFEIÇÕES GEOMÉTRICAS INICIAS

Neste trabalho sao apresentadas analises numericas de perfis de aco formados a frio submetidos a compressao centrada. Trata-se de uma investigacao, realizada por meio de elementos finitos, com vistas a analise da influencia de imperfeicoes geometricas iniciais presentes em perfis U simples e U enrijecido, sob os aspectos de sua forma, amplitude e sentido. As imperfeicoes geometricas sao adotadas na forma de modos de flambagem (autovetores) local, global e distorcional obtidos de analises elasticas de autovalor, observando a suscetibilidade a tais modos para cada secao. Primeiramente, as imperfeicoes sao avaliadas de forma isolada e, em seguida, de forma acoplada (conjunta). Para fins de obtencao da forca de colapso, fica examinada a possibilidade de empregar modos de flambagem isolados para representar as imperfeicoes geometricas. Por fim, fica demonstrada a importância de se investigar a influencia do sentido da imperfeicao global na resposta estrutural de barras comprimidas em analises numericas, em que as imperfeicoes sao representadas pela associacao de modos de flambagem.

Monitoring of the Paraná River Bridge during launching

The Paraná River Bridge, a 2600-m-long steel structure with 26 spans of 100 m, is the largest bridge combining highway and railway systems in Brazil, and was erected by incremental launching. Four bridge segments, two 600 m long and two 700 m long, were assembled on the riverbank, then pushed into their definitive positions. Several parameters were monitored during launching, including the stresses at critical points of the steel structure, displacements at the tops of the piers and at the end of cantilever, forces required for launching, and ambient temperature. In this paper, the stresses in the structure, deduced from strains measured by gauges at several points, are compared with the theoretical values.