• Steel and Composite Structures
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• v.32 no.6
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• pp.769-778
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• 2019

The specially prefabricated steel moment connections with pyramid head is one of the significant innovations in the steel structures forms to improve the installation time and simplify the construction procedure. The beams in this structure form are supported by two top and bottom angles and web double angles. Such a configuration despite its advantages increases the welding operation and filed installation time and costs. In this paper, the effect of using beams with channel and I section in three classes of seismically compact, seismically non-compact, and slender section according to width-to-thickness ratio on the behavior of the connection was investigated under monotonic and cyclic loading. Modeling was performed by ABAQUS and verified by the results of an experimental specimen. The findings indicated that using I and channel section instead of angle section reduces the amount of welding materials as well as easing the installation procedure. However, it has no significant effect on the ultimate strength and ductility of the connection. Furthermore, if the beam section is seismically compact, this form is considered as a special moment frame that has a rotation capacity up to 0.04 radians without any reduction in connection moment resistance.

• International journal of steel structures
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• v.18 no.5
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• pp.1639-1653
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• 2018

Bolted connections are suitable due to high quality prefabrication in the factory and erection in the workplace. Prefabrication and modularization cause high speed of erection and fabrication, high quality and quick return of investment. Their technical hitches transportation can be removed by prefabrication of joints and small fabrication of components. Box-columns are suitable members for bolted structures such as welded steel structures with moment frames in two directions etc., but their continual fabrication in multi-story buildings and performing the internal continuity plate in them will cause some practical dilemmas. The details of the proposal technique introduced here, is to remove such problems from the box columns. Besides, some other advantages include new prefabricated bolted beam-to-column connections referred to BBCC. This connection is a set of plates joined to columns, beams, support, and bolts. For a better understanding of its fabrication and erection techniques, two connection and one structural maquettes are made. The present work aims to study the cyclic behavior of connection numerically. To verify the accuracy of model, a similar tested connection was modelled. Its verification was then made through comparison with test results. The behavior of connection was evaluated for an exterior connection using three different support shapes. The effects of support shapes on rigidity, ductility, rotation capacity, maximum strength, four rad rotation strength were compared to those of the AISC seismic provision requirements. It was found that single beams support has all the AISC seismic provision requirements for special moment frames with and without a continuity plate, and box with continuity plate is the best support in the BBCC connection.

• Steel and Composite Structures
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• v.31 no.3
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• pp.217-232
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• 2019

Modular steel buildings consist of prefabricated room-sized structural units that are manufactured offsite and installed onsite. The inter-module connections must fulfill the assembly construction requirements and soundly transfer the external loads. This work proposes an innovative assembled connection suitable for modular buildings with concrete-filled steel tube columns. The connection uses pretensioned strands and plugin bars to vertically connect the adjacent modular columns. The moment-transferring performance of this inter-module connection was studied through monotonic and cyclic loading tests. The results showed that because of the assembly construction, the connected sections were separated under lateral bending, and the prestressed inter-module connection performed as a weak semirigid connection. The moment strength at the early loading stage originated primarily from the contact bonding mechanism with the infilled concrete, and the postyield strength depended mainly on the tensioned strands. The connection displayed a self-centering-like behavior that the induced deformation was reversed during unloading. The energy dissipation originated primarily from frictional slipping of the plugin bars and steel strands. The moment transferring ability was closely related to the section dimension and the arrangements of the plugin bars and steel strands. A simplified strength calculation and evaluation method was also proposed, and the effectiveness was validated with the test data.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.447-450
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• 2005

A prefabricated composite hollow slab with perforated I-beams was suggested for the replacement of deteriorated concrete decks or the construction of new composite bridges with long-span slabs. Composite slabs with embedded I-beams have considerably higher stiffness and strength. For the application of prefabricated composite slabs to bridges, joints between slabs should satisfy the requirements of the ultimate limit state and the serviceability limit state. In this paper, three types of the detail for loop joints were selected and their structural performance in terms of strength and crack control was investigated through static tests on continuous composite slabs. A main parameter was the detail of the joint, such as an ordinary loop joint and loop joint with additional reinforcements. Even though there was no connection of the steel beams at the joints, the loop joints showed good performance in terms of strength. In terms of crack control, the loop joint with additional reinforcements showed better performance. In ultimate limit state, the continuous composite slabs showed good moment redistribution and ductility.

• Steel and Composite Structures
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• v.37 no.3
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• pp.273-289
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• 2020

Due to the unique construction method of modular steel buildings (MSBs) with units prefabricated fully off the site and assembled quickly on the site, the inter-module connection for easy operation and overall performance of the system were key issues. However, it was a lack of relevant research on the system-level performance of MSBs. This study investigated the seismic performance of two-storey modular steel structure with a proposed vertical rotary inter-module connection. Three full-scale quasi-static tests, with and without corrugated steel plate and its combination, were carried out to evaluate and compare their seismic behaviour. The hysteretic performance, skeleton curves, ductile performance, stiffness degradation, energy dissipation capacity, and deformation pattern were clarified. The results showed that good ductility and plastic deformation ability of such modular steel structures. Two lateral-force resistance mechanisms with different layout combinations were also discussed in detail. The corrugated steel plate could significantly improve the lateral stiffness and bearing capacity of the modular steel structure. The cooperative working mechanism of modules and inter-module connections was further analyzed. When the lateral stiffness of upper and lower modular structures was close, limited bending moment transfer may be considered for the inter-module connection. While a large lateral stiffness difference existed initially between the upper and lower structures, an obvious gap occurred at the inter-module connection, and this gap may significantly influence the bending moments transferred by the inter-module connections. Meanwhile, several design recommendations of inter-module connections were also given for the application of MSBs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.38-47
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• 2013

For the joint connection of the precast steel grid composite decks, the prefabricated joint which is composed of concrete shear key and high-tension bolts was already proposed. In this study, for the purpose of increasing the bending stiffness and bending strength of the proposed prefabricated joint section details of the proposed joint are modified, and through experimental tests the bending performance, such as stiffness and strength of a modified joint, is compared with those of the proposed joint. Test and analysis results show that the shear cracks in the concrete shear key are clearly reduced by the strengthening of the shear key using shear studs and additional rebars. According to analysis results of the moment-curvature relationship, bending stiffness of the modified joint is about 47% greater than the stiffness of the proposed joint. Furthermore, the modified joint has about 32% greater bending strength than the proposed joint. Compared to specimens without the joint the modified joint has same or slightly higher bending strength, but about 37% lower bending stiffness.

• Steel and Composite Structures
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• v.29 no.1
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• pp.1-22
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• 2018

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. Welded plate beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is at present limited information concerning their detailed structural behaviour under bending and shear loadings. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections in full scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and weld arrangements conformed with successful commercial practice. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the connections. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. In general, the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided welded plate connection test results are presented in this paper. The behaviour of single sided welded plate connection test results is the subject of another paper.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.14-17
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• 2004

A prefabricated composite hollow slab with perforated I-beams was suggested for the replacement of deteriorated concrete decks or the construction of new composite bridges with long-span slabs. Composite slabs with embedded I-beams have considerably higher stiffness and strength. For the application of prefabricated composite slabs to bridges, joints between slabs should satisfy the requirements of the ultimate limit state and the serviceability limit state. In this paper, three types of the detail for loop joints were selected and their structural performance in terms of strength and crack control was investigated through static tests on continuous composite slabs. A main parameter was the detail of the joint, such as an ordinary loop joint and loop joint with additional reinforcements. Even though there was no connection of the steel beams at the joints, the loop joints showed good performance in ultimate strength. In terms of crack control, the loop joint with additional reinforcements showed better performance. In ultimate limit state, the continuous composite slabs showed good moment redistribution and ductility.

• Steel and Composite Structures
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• v.29 no.5
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• pp.603-622
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• 2018

Precast concrete structures are erected from individual prefabricated components, which are assembled on-site using different types of connections. In the present design of these structures, beam-to-column connections are assumed pin jointed. Bolted billet beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is currently limited information concerning their detailed structural behaviour under vertical loadings. The experimental work has involved the determination of moment-relative rotation relationships for semi-rigid precast concrete connections in full-scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and bolt arrangements conformed to successful commercial practice. Proprietary hollow core floor slabs were tied to the beams by 2T25 tensile reinforcing bars, which also provide the in-plane continuity across the connections. The contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. The flexural strength of the connections in the double-sided tests was at least 0.93 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.94 to 1.94 times the flexural stiffness of the attached beam. In general, the double-sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided bolted billet connection test results are presented in this paper. The behaviour of single sided bolted billet connection test results is the subject of another paper.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.625-633
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• 2003

For the construction of open-topped steel box girder bridges, prefabricated concrete slab could offer several advantages over cast-in-situ deck including good quality control, fast construction, and elimination of the formwork for concrete slab casting. However, precast decks without reinforcements at transverse joints between precast slabs should be designed to prevent the initiation of cracking at the joints, because the performance of the joint is especially crucial for the integrity of a structural system. Several prestressing methods are available to introduce proper compression at the joints, such as internal tendons, external tendons and support lowering after shear connection. In this paper, experimental results from a continuous composite bridge model with precast decks are presented. Internal tendons and external tendons were used to prevent cracking at the joints. Judging from the tests, precast decks in negative moment regions have the whole contribution to the flexural stiffness of composite section under service loads if appropriate prestressing is introduced. The validity of the calculation of a cracking load fur serviceability was presented by comparing an observed cracking load and the calculated value. Flexural behavior of the continuous composite beam with external prestressing before and after cracking was discussed by using the deflection and strain data.