Authors:Konstantinos Chatzinikos and Charalambos Baniotopoulos
The use of glass-aluminum façades as building envelopes is very common in modern construction. In fact, the advantages of their use have rendered them an optimal choice for building designers. However, glass-aluminum façades are commonly designed using rules of thumb having as a result either their over-dimensioning or an unsafe dimensioning leading to possible damages. The present research study aims to contribute to a pilot methodology that would provide engineers aiming to design glass-aluminum façades with the appropriate technique regarding the modeling and the performance of the aforementioned structures subjected to the imposed critical design loadings (cf. e.g. wind and earthquake). The proposed advanced approach is illustrated by means of a numerical application.
Authors:Khairedin Abdalla, Dimitrios Kaziolas, and Charalambos Baniotopoulos
The present paper deals with the study of the installation behavior of high-strength bolts under friction. For this purpose an experimental program was conducted to evaluate the energy of these bolts that is dissipated due to tightening and loosening. The total number of tested specimens was 100 bolts furnished to the requirements of AASHTO specification M253M. The turn-of-nut tightening method is applied experimentally to evaluate the pretension and the torque for tightening and loosening of bolts. It is mentioned that a number of 56 bolts has 76 mm length while the rest is of 152 mm. The experimental preloading and the lost torque that overcomes friction are compared with the respective analytical values. It is confirmed that the K-nut factor is affected by the type of lubricant and the length of the bolt. Additionally, most of torque is going to overcome friction. The percentage of tightening and loosening torque for both the analytical and the experimental cases is very close.
Authors:Dimitrios Kaziolas, Khairedin Abdalla, and Charalambos Baniotopoulos
It is well known that one of the most popular methods of connecting members in structural steel work is the bolted end-plate connection. Bolted end-plates are simple in their use and construction. But they are extremely complex in term of analysis and behavior since the connection behavior significantly affects the structural frame response and therefore it has to be included to the global analysis and the design of frame. The present paper deals with the structural behavior of full-scale stiffened and un-stiffened cantilever connections of typical I sections. The connection between the extended end-plate to the column flange is achieved by means of high strength bolts in each case. In order to obtain experimentally the actual tension force induced within each bolt, strain gauges were installed inside each one of the top bolts. Thus, the connection behavior is characterized by the tension force in the bolt, the extended end-plate behavior, the moment-rotation relation and the beam and column strains. Thereby, it is important to predict the global behavior of column-beam connections by means of their geometrical and mechanical properties. The experimental test results are compared to those obtained by means of a numerical approach based on the finite element method and is coupled to the theory of non-smooth mechanics. All the arising non-linearities in the connection are described through a non-monotone multi-valued reaction-displacement law. Thus, the problem is formulated as a hemivariational inequality leading to a sub-stationarity problem of the potential or the complementary energy of the connection. This simulation problem is solved by applying a non-convex non-smooth optimization algorithm. The comparison of the results of the experimental testing program with the numerical simulation proves the effectiveness of the proposed numerical method.
Authors:Khairedin Abdalla, Dimitrios Kaziolas, Muneer Badarneh, and Charalambos Baniotopoulos
The aim of the present paper is the experimental and numerical investigation of the unilateral contact effect to the structural response of top and seated angle with double web angle bolted connections. The experimental study is focused on the study of ductility, deformability, moment capacity, bolts prying force and contact zone of these connections. Six full-scale top and seat angles with double web angle bolted connections were tested. Static vertical load was applied until the specimens to reach a condition that cannot resist any additional load after that. In parallel, a finite element analysis was developed to simulate the aforementioned test and in particular, to determine the contact area between the top angles with the column flange, given rise to additional forces, the so-called prying forces. The finite element results were compared to the experimental ones and to those derived theoretically from the application of a model that recently has been proposed in the literature.
Authors:Khairedin Abdalla, Dimitrios Kaziolas, Charalambos Baniotopoulos, and Muneer Badarneh
One of the most usual choices for the connection between the different structural members in steel structures is the bolted connection. The later provide a high level of deformation capacity for the whole structure and a level of stiffness comparable to that of fully welded connections. Top and seated angle with double web angle bolted connections are primarily used for beam-to-column joints. The most important factor for the structural response of beam-tocolumn connections is the rotational stiffness because it affects the behavior of the overall structural steel frame. For this purpose, many experimental tests have been recently conducted to obtain moment-rotation curves. Considering the moment-rotation curves obtained from experimental tests, a simplified analytical model has been suggested to predict the behavior of the connection by fitting techniques. The aim of the present paper is, from one side, the development of a moment-rotation curve for bolted top and seat angle connection with double web angle by means of a proposed theoretical model whose validity checked by comparison with experimental data, and from the other side, the determination of the appearing prying forces in the bolts by means of a simplified and reliable model.