27 publications from this institution
Today, due to environmental issues and consequently preserve of natural sources, the need to introduce sustainable and eco-friendly alternatives to constru
After the Northridge earthquake, it became clear that welded flange-bolted web connections for deep beams do not have adequate ductility when subject to seismic loading. Previous experimental tests on two such connections for shallow beams based on “wedge design” had achieved adequate strength and ductility. Such beams have a wedge removed from the web and flanges are then reattached. This study aimed to investigate the strength and ductility of “wedge design” connections for deep beams. The finite element method was used to model two pre-tested post-Northridge connections for deep beams of different depths. Wedge design was then applied on these connections, with results showing inadequate connection ductility. A parametric study was therefore carried out to find the best wedge detail. The effects of using different stiffener configurations and double wedge details on the strength, ductility and initial stiffness of connections were also investigated. Finally, the most effective stiffener configuration for the connection is proposed.
Generally the required strength and stiffness of an I-shaped beam to the box-shaped column connection is achieved if continuity plates are welded to the column flanges from all sides. However, welding the forth edge of a continuity plate to the column flange may not be easily done and is normally accompanied by remarkable difficulties. This study was aimed to propose an alternative for box columns with continuity plates to diminish such problems. For this purpose a double-web I-shaped column was proposed. In this case the strength and rotational stiffness of the connection was provided by nearing the column webs to each other. Finite element studies on about 120 beam-column connections showed that the optimum proportion of the distance between two column webs and the width of the column flange (parameter <TEX>${\beta}$</TEX>) was a function of the ratio of the beam flange width to the column flange width (parameter <TEX>${\alpha}$</TEX>). Hence, based on the finite element results, an equation was proposed to estimate the optimum value of parameter <TEX>${\beta}$</TEX> in terms of parameter <TEX>${\alpha}$</TEX> to achieve the highest connection performance. Results also showed that the strength and ductility of post-Northridge connections of such columns are in average 12.5 % and 54% respectively higher than those of box-shaped columns with ordinary continuity plates. Therefore, a double-web I-shaped column of optimum arrangement might be a proper replacement for a box column with continuity plates when beams are rigidly attached to it.
Sinusoidal voids of the same size at the beam web can be easily created during fabrication of a castellated beam, when a sinusoidal cut shape is used. Such castellated beams are known as Angelina beams and are available in the market place. This study is designed to investigate the efficiency of using single and multi-sinusoidal voids at the beam web area, to enhance the ductility of the post-Northridge connections. For this purpose, a parametric study is carried out to determine the best configuration of such voids using the finite-element method. The investigation is carried out on more than 440 specimens of different design parameters. The optimum size of sinusoidal voids is proposed to achieve both adequate strength of connections and ductility. Present data indicate that creating a single void at the beam web with optimum size is only effective when the beam overall depth is limited to 750 mm, and the ratio of the beam length to the beam overall depth is equal to or greater than 11·5. For deeper and shorter beams, adequate strength of connection and ductility can be achieved when a modified specimen is used, with either multiple same-size voids with web stiffeners or multiple different-sized voids without web stiffeners.
This study aimed to increase the ductility of post-Northridge connections. To achieve this goal the beam web height was reduced by creating an arch shape cut in the beam web. A parametric study was done on the length and the height of the cut portion and its distance to the column face. Parametric studies were done by using different beam lengths and heights. Analytical results showed that the highest connection strength and ductility can be achieved when the center line of the reduced part is at a distance equal to the beam depth from the column face with the arch length equal to two times of the arch height. Results also indicated a remarkable stress and strain concentration at the intersection of the flat and the arch parts of the beam flange. Filleting these locations and adding vertical stiffeners at the beam web were effective to increase the connection ductility and strength respectively.
This study was aimed to propose an integrated formula developed based on artificial neural network and Bilin element of the OpenSEES software to predict the minimum strength requirement of steel moment frames (R) at any performance level (PL) and desired level of probabilistic response (Percentile). For this purpose, numerous equivalent SDOF systems were analyzed by changing ten different parameters including the period of vibration, PL, Percentile and those that affect the shape of the force-displacement capacity boundary of a moment frame. The proposed model was then compared to the one presented in FEMA P440A, which predicts the median R value at dynamic instability performance level, and the latest version of SPO2IDA software (Vamvatsikos and Cornell, 2005), which predicts the whole trend of an IDA curve. In addition to the simple form of the proposed model, results generally indicated that this model is more accurate than the other available models.
Due to the closed shape of box columns and difficult access to its inside for developing a reliable load path regarding rigid I-beam to box columns connections, in this study, some alternatives have been suggested to replace continuity plates. These alternatives are: two triangular plates, two rectangular plates and added stiff web. To evaluate the efficiency of these suggested alternatives, using ANSYS software, several beam-column connections in each alternative have been modeled. Based on the finite element results the behavior of Ibeam connection to steel box column has been studied. Then the effects of suggested stiffeners on connection stiffness, strength and ductility have been investigated. The results showed that each of the suggested methods might be a good alternative for rigid connection with internal uniform continuity plates. However specimens of additional stiffened webs achieved highest connection strength and ductility.
