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In bridge design, bridge decks regularly overhang past the exterior girders in arrange to extend the width of the deck whereas constraining the specified number of girders. The overhanging part of the deck comes about in uneven eccentric loads to the exterior girders which are by and large most prominent. These eccentric loads are primarily a result of bridge construction operations as well as the weight of new concrete and other construction live loads. These unbalanced loads can lead to a differential edge deflection of overhang deck and a rotation of the exterior girders. The girder rotation or differential deck deflection can also affect local and global stability of the entire bridge. The objective of this study is to enhance the knowledge and understanding of external girder behavior due to unbalanced eccentric construction loads and to identify the critical factors affecting their rotation. In this article, field data obtained during the construction of two skewed (one with a small skew (3.8°) and the second with a severe skew (24°)) and one non-skewed steel girder bridges are described, and a detailed comparison is presented. The three bridges experienced maximum outward exterior girder rotation during construction which subsequently decreased following construction operations. The field results were used to validate and calibrate the finite element models. The numerical and field-monitored data showed good agreement and can be used to assist bridge designers and construction engineers to design appropriate systems to limit girder rotation during construction. [ABSTRACT FROM AUTHOR]

Different bracing systems are currently being used by bridge contractors to prevent exterior girder rotation that can occur during bridge construction. This rotation is caused by unbalanced eccentric loads from the deck overhang. These eccentric loads cause exterior girders to twist which may result in several problems during construction or over the life of the bridge. Contractors generally use block-and-tie systems which are formed with different combinations of reinforcing bars and timber blocks to limit twisting of the exterior girders. Block-and-tie systems do not always work as expected, and their efficacy in preventing rotation has not been fully evaluated. In this research, different configurations and types of bracing systems are investigated experimentally to compare their effectiveness with the current block-and-tie methodology. Specimens are loaded eccentrically to simulate the overhang load that causes rotation in the field. Forty-five bracing combinations were tested and evaluated by varying the number of bracing elements and spacing among them. The measured rotation values for all cases were obtained experimentally from loaded exterior girder at mid span. The experimental results demonstrated the lack of effectiveness of the current block-and-tie systems. Adjustable diagonal steel pipes, permanent intermediate cross-frames, or both were tested as alternatives and showed notable reductions in girder rotation. Finally, finite element models (FEM) were developed using ABAQUS/standard to replicate the experimental results followed by additional analysis using the validated FE model. The results from the experiment and the FEA highlight deficiencies in the current block-and-tie systems and present three improved rotation prevention systems. [ABSTRACT FROM AUTHOR]

Various petroleum-based polymers are being widely used in the automobile and aviation industries. However, the scarcity of petroleum-based polymers, their lack of biodegradability, and stringent environmental regulations lead researchers to look for green biopolymers/biocomposites as an alternative to petroleum-based polymers. Biopolymers have potential applications in various exterior and interior parts of an automobile, including steering, doors, wheels, electrical components, engine parts, exhaust systems, and so on. Almost all automakers are currently focusing on developing novel biopolymers, and they have successfully used bio-based materials in their newer version of automobiles, eventually replacing petroleum-based polymers. However, biopolymer uses in the aviation industry are not yet widespread because of stricter property requirements. Some advanced biopolymers are applied in interior aircraft panels, waste and drainage systems, engine components, cockpits, portholes, windshields, aircraft tires and inner tubes, exterior lighting, and helicopter windscreens. These materials are expected to substitute traditional plastics with the help of modifying agents, cutting-edge manufacturing technology, and a reliable supply chain of biopolymers. This review discusses the current practices, recent advances, and prospects of biopolymers in automotive and aviation engineering applications. [ABSTRACT FROM AUTHOR]