Reinforced concrete (RC) frames with an open ground floor and various infill distributions have been analyzed for seismic loadings by the finite element method. The infills have been modeled by diagonal struts. Focus is placed on the effects of infill distribution on various structural responses, including (i) the lateral deflection, (ii) the column axial forces, (iii) the column bending moments, (iv) the base shear, and (v) the natural period of the frame. The equivalent static force method (ESFM) and response spectrum method (RSM) for linear structures have been applied, and the results obtained have been compared. It was found that the structural responses do not change appreciably by the ESFM analysis for random infill distributions, while they increase noticeably in the RSM analysis. This manifests the inadequacy of using the ESFM for general purposes, for which modifications were proposed in this paper for the design of RC columns. As the natural period of the RC frame converges with the code equations only for higher amounts of infill, it is necessary to incorporate the amount and distribution of infill in the dynamic analysis of RC frames.
This paper focuses on the stability of fracturing process in reinforced concrete beams and derives a fracture mechanics based transformation between crack opening displacements (COD) and re-bars force. Bridged crack model is adopted which considers distinct phenomena for damage process in concrete and bridging of cracks by re-bars. The derived transformation yields crack profiles for known re-bar force determined by either RC section analysis or computations having fracture mechanics based approach. Inverse of the integral transformation is ill-posed when experimentally collected COD's are not exact. Tikhonov method of regularization is followed to compute re-bar force from COD where the extremals of the Tikhonov functional is determined numerically. A numerical example proving the applicability of this method with different noise levels are demonstrated. It is observed that current method of numerical inverse analysis on external surface COD can satisfactorily determine location and force of re-bars in the beam cross-section within limited tolerance of noise in data. Application of this method enables the maintenance engineers to retrieve inner cross-sectional information from outer measurements in a non-destructive way.
This paper develops a method to determine"bridging law"for continuously aligned fiber composites to understand damage mechanisms from a maintenance engineering point of view. Fracture mechanics approach has been employed to form the integral equation for mathematical simulation of embedded straight cracks and single edge cracks in specimens of infinite or finite width under tensile and bending stresses. Closing pressure was assumed between the crack surfaces due to continuous fibers or aggregates which remain connected to both the crack surfaces. Inverse analysis is performed on crack opening displacement (COD) data to get magnitude and distribution of bridging stresses for fiber composites. Synthetic data were created by forward analysis for certain crack configurations to get exact COD data from a theoretical point of view. To simulate practical situations, data were made noisy by inserting noise of known levels. Exact bridging stress distributions were retrieved by the inverse analysis up to certain level of noisy data which establishes applicability of the method developed here.
The nonlocal elasticity theory and the Euler–Bernoulli (EB) beam theory are used to present closed-form analytical expressions for static bending, axial buckling, and free vibration of nanosized beams resting on an elastic foundation. The differential constitutive relations of Eringen are utilized to represent the small-scale effects of the nanobeam’s mechanical response. The governing equation of motion is derived by employing Hamilton’s principle. Utilizing the Laplace transform approach, analytical expressions of the bending displacements, the critical buckling force, and the vibration frequency of nanobeams with simply supported (S-S), clamped, cantilevered, and propped cantilevered boundary conditions are produced. In order to confirm the correctness of the offered closed-form equations, their outputs are compared to those of the available numerical method solutions. The effects of the Winkler parameter, the Pasternak parameter and the nonlocal parameter on bending, buckling, and vibration characteristics of nanobeams have been explained. Presented analytical expressions and graphical representations demonstrate how increasing Winkler and Pasternak parameters reduce bending displacements while raising the critical buckling load and the natural frequency of nonlocal nanobeams. Benchmark numerical results are also presented to investigate and discuss the effects of all parameters on bending deflections, buckling loads, and natural frequencies of nanobeams.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.