Portal frame

About: Portal frame is a research topic. Over the lifetime, 1778 publications have been published within this topic receiving 7210 citations.

Three-dimensional simulation of nonlinear response of reinforced concrete members subjected to impact loading

Abstract: A triaxial failure criterion was applied with the theory of plasticity to model the behavior of reinforced concrete structures subjected to impact loading The concrete nonlinearity, the cracking in the concrete elements, and the loading and unloading were simulated using an elastic-plastic fracture model The influence of the loading rate on the concrete can readily be introduced by modifying the level of the yield and loading surfaces if the necessary data are available In tension, a smeared crack model was used with a tension-softening model for the retained postcracking stresses The reinforcing bars were represented by tensile stiffeners that were smeared in the appropriate direction over the element cross section Verification of the analytical procedure was carried out using previously published results from scale model tests on a reinforced microconcrete beam and a portal frame, as well as from a test on a full-scale reinforced concrete beam It was found that the maximum impact load, the propagation of the cracks, and the failure modes can be predicted with reasonable accuracy using the proposed approach The approach can be used in the design of reinforced concrete structures subjected to impact loads

Experimental investigation of the use of ferrocement laminates for repairing masonry in filled RC frames

Abstract: An experimental study was carried out to investigate the in-plane strength of masonry infilled reinforced concrete portal frame rehabilitated with ferrocement. A model of a portal frame having masonry infill panel was constructed and tested in the laboratory for this purpose. The load was applied monotonically at the top of the frame till the ultimate capacity was reached accompanied by substantial formation and propagation of cracks. Then both the infill and the frame were repaired by ferrocement coating. After rehabilitation, the frame was tested in the laboratory following the same procedure as for the original frame. The masonry infill frame repaired with ferrocement showed significant improvement in performance and more than original strength was achieved. This reveals the potential use of ferrocement as a retrofitting and strengthening material of the existing infilled frame.

Effect of random material variability on seismic design parameters of steel frames

Abstract: Whereas an increase in material yield stress beyond the code specified characteristic value enhances plastic capacity, it may cause a reduction in overall ductility and energy absorption capability of steel frames. Since quality control of various shapes of sections used on site is difficult to impose, the effect of this random variability on design response parameters should be accounted for in earthquake-resistant regulations. Moreover, the required weak-beam/strong-column design principle in particular, and failure mode control in general, could be undermined if the yield stresses in beam and column assume two opposite extremes in a random sample. This paper addresses the problem of defining the expected range of response parameters in a steel frame with randomly varying yield stress. A simple portal frame is designed using code specified characteristic values and verified by non-linear transient dynamic analysis. The influence of yield stress variability, including the degree of correlation between beam and column material properties, on several response parameters is assessed through a Monte Carlo simulation study. Results are presented from both univariate and bivariate statistical analyses that quantify the relationship between input (material) and output (response) parameters. Assessment of the interdependence of output parameters given a particular model for yield stress variability is also undertaken. It is shown that certain response parameters exhibit more favourable statistical properties than others. Thus, the implications for seismic code design are discussed in the light of these results.

Buckling and Postbuckling of a Symmetrically Loaded Three-Hinged Portal Frame

Abstract: A nonlinear stability analysis based on a variational approach is performed on a symmetric three-hinged rectangular frame symmetrically loaded. The loading consists of two vertical concentrated forces which may be applied eccentrically with respect to the center lines of the columns. By using a perturbation technique the critical loads of the perfect frame corresponding to its first two buckling modes associated with bifurcational instability are established. It is also found that the sway-buckling mode either of the perfect or the imperfect frame is associated with a stable bifurcation point. The effects of loading eccentricity and slenderness ratio upon the critical load are assessed.