Volume 1 Issue 3
Authors: Elif Cagda Kandemir; Taiji Mazda
Abstract: This paper presents nonlinear viscous damper (NVD) implementation to an existing highway arch bridge structure to prevent pounding effect on abutments. The nonlinear dynamic response analysis performed on finite element model of bridge structure due to severe earthquake excitations showed that the relative displacement response between the bridge deck and the abutments exceeds available distance in normal conditions through the longitudinal direction. As a remedy for suppressing seismic responses, nonlinear viscous dampers were approved to be installed at the end of the deck since they are simple to implement for existing structures in construction field. The transversal behavior has also been investigated to mitigate the corresponding responses by the installation of dampers in order to control the lateral behaviour of the bridge for each direction. The damper capacity in response to seismic responses through transverse direction was also obtained in the same manner as done in longitudinal direction.
Keywords: Highway Arch Bridge; Pounding; Nonlinear Viscous Damper; Energy-equivalent Method; Single Degree-of-freedom System; Finite Element Model
Authors: Claudio Amadio; Chiara Bedon
Abstract: Because of the characteristic of high slenderness ratios, monolithic and laminated glass elements are frequently subjected to buckling phenomena. As regards laminated glass beams and panels, in particular, the effects of possible temperature or time-load variations represent only some aspects that make complex their global structural response. In this context, the paper focuses on the load-carrying behavior of in-plane compressed laminated glass elements. In it, some analytical formulations are presented to describe realistically their typical behavior. As shown, the proposed formulations are in good agreement with experimental and numerical data available in literature. At the same time, they allow to perform a rational buckling verification of such brittle load-bearing elements. Finally, according to the suggestions the Eurocodes give for the verification of traditional structural elements, a series of buckling curves opportunely calibrated are proposed to guarantee the requisites of resistance, serviceability, and durability typically imposed in the design of conventional structural systems.
Keywords: Laminated Glass; In-plane Compressed Beams and Panels; Sandwich Elements; Equivalent Thickness; Buckling Curves
Authors: Mohammad Heydari; Luis Amador-Jimenez
Abstract: Developing reliable safety performance functions (SPFs) capable of estimating expected accident frequencies and identifying hazardous sites is a major concern of departments of transportation. In Bayesian accident data analysis, sites are commonly ranked based on their posterior expected accident frequency in order to be selected for safety countermeasures. The primary objective of this research was therefore to propose an alternative method to evaluate the level of accuracy of an SPF and identify potential hazardous sites, both directly through a single step or measurement. A case study of the Trans-Canada highway in New Brunswick was used applying Bayesian statistics with three different likelihoods: Poisson, hierarchical Poisson-gamma, and hierarchical Poisson-lognormal. As a secondary and validating objective, the above mentioned models were investigated and compared. At the same time, the effect of environmental exposure on the occurrence of accidents was studied. It was found that accident frequencies were slightly affected by environmental conditions. The posterior means of the model parameters indicated that, for the case study, various likelihoods provided roughly similar estimates. However, there were significant differences in the way in which these likelihoods captured the uncertainty around the posterior means through the standard deviation, 95% credible interval, and model-fitting. Moreover, a series of computational and graphical goodness-of-fit measures were examined. In particular, the hierarchical Poisson-gamma likelihood presented the best model-fitting. Furthermore, a measure of relative risk was computed for each site based on the error term presented in Poisson mixture models. The rankings of sites using this measure and the posterior expected accident frequency were generated and compared. A positive covariance between the adopted relative risk factor and the expected accident frequency per segment length was observed. The results and discussions suggested that such a factor can be employed (1) to verify the dependability of SPFs and (2) as an alternative to identify and prioritize potential hazardous sites.
Keywords: Safety Performance Functions; Bayesian Inference; Potential Hazardous Sites; Goodness-of-fit; Relative Risk Factor
Authors: N. Anandavalli; N. Lakshmanan; J. Rajasankar; Amar Prakash
Abstract: In this study, response of Steel-Concrete Composite (SCC) panels subjected to air-blast loading is numerically simulated by conducting finite element analysis. A simplified approach to generate the finite element model of the SCC panels is proposed. In the proposed approach, solid, plate and link elements are used to represent the concrete core, steel cover plates and through-through connectors respectively. Interface between the solid and plate elements are idealized with surface-to-surface contact elements, which take care of the transfer of forces between solid and plate elements. Application of the proposed approach for analyzing the SCC components is validated through two examples. Static response of a SCC beam is obtained by using the proposed approach, which is in close agreement with the experimental results. Dynamic response of a SCC panel with through-through connectors subjected to blast pressure due to an explosion of 200 kg TNT at 5 m is obtained by using the proposed simplified approach. Peak response is verified with the results obtained by using an analytical approach. Parametric studies are carried out by varying the charge weight, thickness of the cover plates and diameter of shear connector of the SCC panel. Thickness of the cover plates is found to affect the peak response in a nonlinear manner, while diameter of shear connector is found to have only marginal influence on the peak response.
Keywords: Steel-Concrete Composite; Blast Loading; Peak Displacement; Overpressure; Time-History
Authors: Fabio De Angelis; Donato Cancellara
Abstract: Masonry buildings are known to be characterized by poor performances during seismic events. In fact, their behavior is not optimal when they are loaded by horizontal forces associated to the seismical actions on the structure. In order to characterize the dynamical properties of masonry buildings when subject to horizontal forces, a masonry building prototype has been realized in the laboratory and an experimental investigation campaign has been conducted with the aim of determining a structural identification of the masonry building prototype. Furtherly, the characterization of the structure is also performed via a numerical analysis of the dynamical behavior of the masonry building. Numerical tests are performed and a finite element model of the masonry building prototype is presented in order to achieve the characterization of the dynamical parameters through a comparative analysis of the experimental and the numerical data. Accordingly, in the present paper an experimental campaign is illustrated which has been performed on a masonry building prototype for studying the structural behavior of the masonry building subject to harmonic horizontal forces of different intensity. A physical model is realized in the laboratory by considering a two-storey masonry building. The structure test is subjected to harmonic horizontal force inputs supplied by a vibrodyne. The experimental results characterize the dynamical effects of the masonry building prototype subject to harmonic forces and illustrate the behavior of the building under the predominant actions of a seismic input. Further a finite element modeling of the masonry building prototype is considered and a numerical analysis is performed for describing the dynamical features of the system. The finite element modeling of the structure has the aim to reproduce the experimental testings of the masonry building subject to the harmonic force inputs. For different monitored nodal points of the finite element mesh, the frequency response functions corresponding to the frequency load inputs are determined. Consequently, a comparative analysis is reported in order to perform the characterization of the suitable dynamical parameters of the structure and to finalize the structural identification of the masonry building. Such comparative analysis between the experimental results obtained on the masonry building prototype and the numerical results obtained with the finite element analysis allows assessing the calibration of the material dynamical parameters for characterizing the dynamical behavior of the masonry structure. The proper assessment of the dynamical parameters of the masonry building allows having a refined structural identification of the masonry building for a better and more accurate simulation of the dynamical behavior of the structure.
Keywords: Experimental Results; Finite Elements; Masonry Building; Numerical Modeling; Structural Identification