Abstract

MOLINA HERRERA, Maritzabel  and  ORTIZ PORRAS, Javier Alberto. Behavior of cold-formed thin steel sections (MM) under concentrated loads. Ing. Investig. [online]. 2006, vol.26, n.3, pp.12-25. ISSN 0120-5609.

New sections are continually being developed in the cold-formed steel world to improve the performance of existing sections. M-section development provides an example of improving C-sections' shear resistance and web crippling resistance against C-sections' concentrated loads. C-sections' shear nominal strength can be achieved through locating tow web intermediate stiffeners (M-sections) even though web crippling resistance cannot be increased in the same way. Such intermediate stiffeners mean that M-section stresses and deflections cannot be analysed with traditional material mechanics. Concentrated loads cause this behaviour to become increased; 4 different models and 3 tests for each of then were thus developed, as well as determining M-sections' theoretical resistance (based on 1996 AISI). The values obtained corresponded to maximum resistance load, visual identification of any possible type of failure, deflections (at middle span) and deformations (εx, εy, εxy). Mathematical models were also used for comparing the finite element method and simplified mathematical models' test results for a detailed review of MM-section stress and deformation. These models were calibrated on the test results. After the failure mode was identified for each model, MM-section maximum resistance load was compared to nominal load (according to AISI formulation, also aiding formulating nominal strength calculation). The information obtained from tests and mathematical models was analysed to observe parameter (Δ, σ y τ) tendencies respecting applied load (P). Cyclic tests under pseudo-static loads were performed to study MM-sections' hysteretic behaviour.

Keywords : cold-formed steel; web crippling; stiffeners; hysteresis; finite elements; MM section; concentrated loads.

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