Numerical and Experimental Investigation on Low Damage Steel-Timber Post-Tensioned Beam-Column Connection (original) (raw)
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Experimental studies on full-scale post-tensioned seismic-resistant steel moment connections
Six full-scale interior connection subassemblies of post-tensioned wide flange beam-to-column moment connections were tested. Each was subjected to inelastic cyclic loading up to 4% story drift to simulate earthquake loading effects. Bolted top and seat angles are used in the connection, along with posttensioned high strength strands that run parallel to the beam. These strands compress the beam flanges against the column flange to develop the resisting moment to service loading and to provide a restoring force that returns the structure to its pre-earthquake position. The parameters studied in these experiments were the initial post-tensioning force, the number of post-tensioning strands, and the length of the reinforcing plates. The experimental results demonstrate that the post-tensioned connection possesses good energy dissipation and ductility. Under drift levels of 4%, the beams and columns remain elastic, while only the top and seat angles are damaged and dissipate energy. The lack of damage to the beams, columns, and the post-tensioning enable the system to return to its plumb position (i.e., it self centers). Closed-form expressions are presented to predict the connection response and the results from these expressions compare well with the experimental results.
Buildings
In this study, the seismic responses of moment-resisting steel frames (MRSFs) with welded and post-tensioned connections under 28 artificial seismic sequences (mainshock–aftershock) are compared. For this aim, the mainshock are scaled at different ground motion intensity levels as a function of the spectral pseudo-acceleration corresponding to the fundamental period of vibration of the structure Sa(T1), whereas different intensity levels of the aftershocks are used for a percentage of the peak maximum acceleration of the mainshock. The seismic performance comparison of both structural systems is computed for the maximum, residual inter-story drift and hysteretic energy demands. The results show that post-tensioned frames significantly reduce the structural demands, especially in the case of residual inter-story drifts and hysteretic energy in comparison with moment-resisting steel frames with welded connections. The reductions in the structural response tend to be larger as the inte...
COMPDYN Proceedings, 2021
For the design of dissipative heavy timber frame structures, in the context of modern seismic design approach based on the mechanical triad of strength, stiffness and ductility, brittle timber failure modes can be avoided by integrating hybrid timber-steel system into modern timber connection technology. Thus, the overall seismic performance of timber structures can be improved, entrusting the dissipation function to ad hoc conceived devices, like steel links. With reference to the structural type of Moment Resisting Frames (MRF), steel links located at the ends of the beams are able to provide a significant dissipative capacity, by means of cycles of plastic deformations, while timber members and steel connections, to be designed with an adequate overstrength as respect to the link, behave in elastic field. In this regards, the paper presents the capacity design and the mechanical characterization through monotonic numerical analyses of two different timber beam-to-column joint with steel link for MRF structures, consisting of a timber beam and a steel link connected each other by means of a stiffened end-plate and glued-in steel rods. The proposed design criteria of the joint are validated through the evaluation of performance, by means of nonlinear pushover analyses on the joint refined FEM models, in terms of key parameters, such as ultimate resistance, stiffness, rotation capacity and failure modes. The numerical results confirm the plastic deformation of the link, which large dissipative capacity of the joint corresponds to.
Post-Tensioned Moment Connections for Seismic Resistant Steel Frames
2000
A series of experimental tests were conducted to investigate the behavior of an innovative post-tensioned (PT) top-and-seat-angle wide flange (WF) beam-to- column moment connection for steel moment resisting frames subjected to seismic loading conditions. Nine large-scale specimens were tested. Each specimen represented an interior connection and consisted of two WF beams attached to a column. The parameters investigated in the
Seismic Behavior of Moment-Resisting Frames with Conventional and Innovative Connections
Symmetry
In the last few decades, increasing efforts have been devoted to the development of beam-to-column connections able to accommodate the local ductility demand dissipating, contemporaneously, the seismic input energy. Among the typologies proposed, the so-called RBS (Reduced Beam Section) has gained wide acceptance in the construction market, leading to easy-to-construct and cost-effective solutions. As an alternative, new proposals based on the inclusion of friction devices in beam-to-column joints have recently been made. Such a practice has the merit, in case of destructive events, of exhibiting wide and stable hysteretic cycles concentrating damage in elements that undergo only minor yielding. Both RBS and friction joints have been widely studied, carrying out experimental tests on sub-assemblies investigating their cyclic rotational response. Nevertheless, the available experimental results on full-scale structures equipped with these connections are still quite limited. This is ...
Monotonic Tests on Beam-To-Column Joint with Steel Link for Timber Seismic Resistant Structures
2023
For the design of dissipative heavy timber frame structures, in the context of modern seismic design approach based on the mechanical triad of strength, stiffness and ductility, brittle timber failure modes can be avoided by integrating modern timber connection technology into hybrid timber-steel system. The overall seismic performance can be improved, entrusting the dissipation function to ad hoc conceived devices, as an alternative to connections. Steel links located at the ends of the beams are very promising solutions, which can develop plastic hinges, thus providing a ductile behaviour, with a significant dissipative capacity. Besides timber members, as well as connections, to be designed with an adequate over-strength, can remain in elastic field. In this perspective, the paper illustrates the mechanical characterisation through monotonic tests of two different configurations of timber beam-to-column joint with steel link for heavy timber frames, consisting of a timber element connected to a steel link by means of a steel end-plate and gluedin steel rods. The experimental results indicate a satisfactory agreement with the theoretical ones, therefore the suitability of the system and of the design criteria.
Earthquake Engineering & Structural Dynamics, 2014
This paper investigates the effect of the composite action on the seismic performance of steel special moment frames (SMFs) through collapse. A rational approach is first proposed to model the hysteretic behavior of fully restrained composite beam-to-column connections, with reduced beam sections. Using the proposed modeling recommendations, a system-level analytical study is performed on archetype steel buildings that utilize perimeter steel SMFs, with different heights, designed in the West-Coast of the USA. It is shown that in average, the composite action may enhance the seismic performance of steel SMFs. However, bottom story collapse mechanisms may be triggered leading to rapid deterioration of the global strength of steel SMFs. Because of composite action, excessive panel zone shear distortion is also observed in interior joints of steel SMFs designed with strong-column/weak-beam ratios larger than 1.0. It is demonstrated that when steel SMFs are designed with strong-column/weak-beam ratios larger than 1.5, (i) bottom story collapse mechanisms are typically avoided; (ii) a tolerable probability of collapse is achieved in a return period of 50 years; and (iii) controlled panel zone yielding is achieved while reducing the required number of welded doubler plates in interior beam-to-column joints.
Tubular Web RBS Connection to Improve Seismic Behavior of Moment Resisting Steel Frames
Scientia Iranica
A new type of Reduced Beam Section (RBS) connection, called \Tubular Web RBS (TW-RBS)", is proposed in this research. TW-RBS is made by replacing a part of web with a tube at the expected location of the beam plastic hinge. In addition to an analytical study, the proposed section is numerically studied under cyclic load using ABAQUS niteelement software, and a test specimen is used for the calibration of numerical results. The results show that using TW-RBS not only creates a ductile fuse far from the beamto-column connection components, but it also increases story drift capacity up to 9%. Furthermore, the tubular web, like corrugated sheet, can improve both the out-of-plane sti ness of the beam longitudinal axis and the ange stability condition due to the smaller width-to-thickness ratio of the beam ange in the plastic hinge region. Thus, the tubular web improves lateral-torsional buckling stability of beam. On the other hand, the tubular web provides a better condition than other accordion web with sharp corners in terms of low-cycle fatigue, because change of direction of strain in arc shape of the tubular web section is smaller than the accordion web with sharp corners.
Performance of Seismic Moment Resisting Connections Under Column Removal Scenario | Nist
2008
Beam-to-column moment connections in steel frame construction have been studied extensively for seismic applications. The behavior of such connections, however, has not been studied under the monotonic loading conditions expected in progressive collapse scenarios, in which connections are subjected to combined bending and tension. This paper presents an experimental and analytical assessment of the performance of beam-column assemblies with two types of moment resisting connections under vertical column displacement. The connections considered include (1) a welded unreinforced flange – bolted web connection and (2) a reduced beam section connection. The study provides insight into the behavior and failure modes of the connections, including their ability to carry tensile forces that develop in the beams. The results indicate that these connections can sustain larger rotations under monotonic loading conditions than under the cyclic loading conditions developed for seismic applicatio...