Behaviour of reinforced concrete rectangular sections based on tests complying with seismic construction requirementsThe prediction of the seismic behaviour of reinforced concrete elements using numerical models has become a field of growing interest in recent years due to the importance of the effects induced by seismic loads applied to reinforced concrete structures. The simulation of the hysteretic behaviour of the plastic hinges generated in the structure when the seismic load acts requires the use of models that are able to describe the sectional behaviour of structural members. Thus, the main objective of the present paper is the adjustment of several empirical expressions that reduce the computational time needed to simulate the yield and ultimate behaviour of a given reinforced concrete rectangular section under either monotonic or cyclic loading. The expressions are calibrated with a selection of tests, taken from a published database of more than 1000 tests, according to the criterion that the selected specimens comply with the seismic construction requirements of the main international building codes . Owing to their robustness and the acceptable computation time for low-dimensional problems, genetic algorithms are used for this calibration. The equations proposed can be employed by structural engineers for the design and analysis of actual structural elements used in ordinary reinforced concrete buildings located in seismic areas, and provide more accurate results than other expressions.
The design and construction of next-generation telescopes involves the development of new technologies capable of fabricating and testing large dimension mirrors with small f-numbers in order to get rapid surfaces. Secondary mirrors in Cassegrain-type telescopes are convex and hyperbolic. When the dimensions are increased and its f-number is reduced, the difficulty in testing the surface increases exponentially and traditional optical testing is no longer feasible. The present study offers a technique developed to test a mould to be used in fabricating the secondary mirror of the Large Millimeter Telescope (LTM). The mould is a hyperboloid surface with a conic constant of -1.1474, a paraxial curvature radius of 1764.94 mm and a diameter of 1600 mm. Since the telescope will work within wavelengths ranging from 1 to 3 mm, surface errors must be less than 15 µm in rms. The mould was evaluated by measuring the coordinates of 53,824 points on its surface using an advanced coordinates measurement machine (CMM) at the National Institute of Astrophysics, Optics and Electronics (INAOE) in México. From this we obtained the shape of the conic surface that better fits this distribution of points, using a Genetic Algorithms (GA) program developed for this purpose. Finally, the results obtained are shown.
Influencia del tipo de rótula plástica en el análisis no lineal de estructuras de hormigón armadoInfluence of the type of plastic hinge in the non-linear analysis of reinforced concrete structures
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