Ductile connection to improve the fire performance of bare-steel and composite frames

PurposeIn order to improve the robustness of bare-steel and composite structures in fire, a novel axially and rotationally ductile connection has been proposed in this paper.Design/methodology/approachThe component-based models of the bare-steel ductile connection and composite ductile connection have been proposed and incorporated into the software Vulcan to facilitate global frame analysis for performance-based structural fire engineering design. These component-based models are validated against detailed Abaqus FE models and experiments. A series of 2-D bare-steel frame models and 3-D composite frame models with ductile connections, idealised rigid and pinned connections, have been created using Vulcan to compare the fire performance of ductile connection with other connection types in bare-steel and composite structures.FindingsThe comparison results show that the proposed ductile connection can provide excellent ductility to accommodate the axial deformation of connected beam under fire conditions, thus reducing the axial forces generated in the connection and potentially preventing the premature brittle failure of the connection.Originality/valueCompared with conventional connection types, the proposed ductile connection exhibits considerable deformability, and can potentially enhance the robustness of structures in fire.

Pedestrian/Bike Bridge over Manzanares River in Madrid

<p>The city of Madrid is making efforts to make the most of the river Manzanares, improving the quality of life of the citizens and increasing the biodiversity. Madrid Rio is the most central and visible side of this work. But there is also a will to extend this enhancement beyond the city center, taking advantage to the fullest extent of the opportunities that a river brings to enhance the urban sustainability of such a big metropolis. The Manzanares Linear Park extends this intervention south along the river. The bridge presented in this work belongs to that linear system; its objective is not just crossing the waterway, since it is a sparsely populated area with other bridges nearby, but rather bringing the trail and the users closer to the river. Limited time was available for design, fabrication and installation of the bridge. This fact had a deep effect on the solution. It is a simple design that consists of three different pieces of similar weight that are manufactured in the workshop and separately brought to the final location where they are quickly assembled by means of pinned connections and without any additional welding on site. Then the whole bridge is craned to its final position.</p>

High Resolution Modeling and Modeling of Connections in Pony-Truss Bridges

Pony-truss bridges are usually modeled using simplifying assumptions, such as pinned connections and analyzing the trusses separately from the rest of the structure. Pony-truss bridges are also generally designated as possessing many Fracture Critical Members (FCM), a characteristic that requires more rigorous inspections. Eliminating or reducing the number of FCM is desirable as it reduces inspection costs. A high-resolution model of a pony-truss bridge was assembled in ABAQUS CAE that explicitly models the behavior of the gusset plates in the connections and the angles in the framed stringer connections. This model indicated alternative load paths that are potential sources of redundancy useful for retrofit or reclassification of bridges with FCM designation. Higher-resolution models of framed stringer connections were also made in ABAQUS CAE using solid elements explicitly modeling the bolted connections. The connections were loaded in tension; what the stringers must hold if they supply an alternative load path for the truss in the event of fracture in the bottom chord. The primary objective of the work described is to provide high-resolution finite element analysis results that can be used to create general behavior for lower-resolution finite element models used in fracture critical analyses to reclassify FCM as non-fracture critical. The results of high-resolution modeling reveal the behavior that is necessary to include in these lower-resolution models, as well as potential alternative load paths. Lower-resolution models are assembled in SAP2000 and matched to the higher-resolution models.

Experimental and analytical investigations on a large floor truss pinned connection

The pinned connection method was used to connect the large-span floor truss to the steel column in Zoucheng International Conference Center project, which played a quite important role to achieve the in-plane rotation and transfer heavy loads directly. Four specimens were tested experimentally to investigate the monotonic and cyclic behavior of this connection method, including two independent pinned connections and two assembled truss connections. The load–displacement curves, deformation development, failure mode, ductility, and energy dissipation capacity were discussed in detail. Besides, the nonlinear multi-scale finite element models of the pinned and truss connections were established. The numerical simulations not only captured the global behavior and local limit states observed in tests but also revealed valuable new information that could not be directly obtained from the tests. The experimental and numerical results showed that both the pinned and truss connections had good ductility, load transfer ability, and ideal rotation capacity with large safety margin, indicating these constructions could be used as references for similar projects.

Experimental testing and design of BRB with bolted and pinned connections

The recent series of damaging earthquakes in Christchurch, New Zealand has encouraged greater recognition of the post-earthquake economic impacts on New Zealand society and higher emphasis on low-damage earthquake resisting systems. Braced frames incorporating Buckling Restrained Braces (BRB) are seen as a significant contender for such a system. This research project focuses on the development of a reliable design procedure and detailing requirements for a generic BRB system. To gauge the performance of the designed system and to ascertain the reliability of the developed procedure, a series of static and dynamic sub-assemblage tests on the BRB frame with two different brace connection configurations were performed. The results are presented and discussed herein. The experimental tests generated stable and near symmetrical hysteresis loops, which is a principal characteristic of a well performing BRB system, albeit with the occurrence of slack in the connections. The experimental test results shows that several improvements need to be made to the proposed design procedure and detailing as outlined throughout the paper; especially the procedural modification to prevent slack from occurring in the two different connection systems. It is envisaged that applications will typically involve use of proprietary braces, however these need to be applied in accordance with the New Zealand design procedure; and determining the appropriate procedure was a key part of this project.