Jointless Structures Research Articles

Compensation Effect of Superconducting Hybrid Trapped Field Magnet

The so-called ring-shape superconducting trapped field magnet has great potential for commercial application due to its flexible size and joint-less structure. However, due to the spatial asymmetry of the structure, the trapped magnetic field has a non-negligible magnetic declination, which becomes the major obstacle to its application. To compensate the magnetic declination, a new concept of superconducting hybrid magnet consisting of the ring-shape magnet and the HTS bulk is proposed. By adjusting the placement of the HTS bulk in the central air gap, magnetic declination can be effectively compensated. Both experiments and 3D numerical model are used to evaluate the magnetic uniformity after compensation. The results show that the proposed hybrid magnet will have an obvious compensation effect on the magnetic declination. And the hybrid magnets have promising applications with requirements on the uniformity of magnetic field such as potable MRI.

Numerical Study on Ring-shape Superconducting Trapped Field Magnet Based on Circuit Model

The so-called ring-shape superconducting trapped field magnet has been proved as a potential candidate to replace commercial permanent magnets in practical industrial applications on account of its jointless structure. In this paper, a circuit method based on Bean model, E-J power law and Faraday law has been built to investigate the magnetization mechanism of ring-shape magnet. The field dependent critical current of superconducting materials has been taken into consideration for further optimization. The numerical model was verified by both finite element method (FEM) and experiments. Compared with other methods, the circuit-based simulation method has the advantages of high efficiency, fast speed and wide applicability. On basis of this method, the paper also studied characteristics of ring-shape magnets under different working conditions to provide a guideline for the magnet design.

Extending the application of integral frame abutment bridges in earthquake‐prone areas by using novel isolators of recycled materials

SummaryIntegral abutment bridges (IABs) are jointless structures without bearings or expansion joints which require minimum or zero maintenance. The barrier to the application of long‐span integral abutment bridges is the interaction of the abutment with the backfill soil during the thermal expansion and contraction of the bridge deck, that is, serviceability, or when the bridge is subjected to dynamic loads, such as earthquakes. The interaction of the bridge with the backfill leads to settlements and ratcheting of the soil behind the abutment and, as a result, the soil pressures acting on the abutment build up in the long term. This paper provides a solution for the aforementioned challenges by introducing a novel isolator that is a compressible inclusion of reused tyre‐derived aggregates placed between the bridge abutment and the backfill. The compressibility of typical tyre‐derived aggregates was measured by laboratory tests, and the compressible inclusion was designed accordingly. The compressible inclusion was then applied to a typical integral frame abutment model, which was subjected to static and dynamic loads representing in‐service and seismic loads correspondingly. The response of both the conventional and the isolated abutment was assessed based on the settlements of the backfill, the soil pressures and the actions of the abutment. The study of the isolated abutment showed that the achieved decoupling of the abutment from the backfill soil results in significant reductions of the settlements of the backfill and of the pressures acting on the abutment. Hence, the proposed research enables extending the length limits of integral frame bridges subjected to earthquake excitations. Copyright © 2016 John Wiley & Sons, Ltd.

Serviceability performance of FRC columns under imposed displacements: An experimental study

This paper presents an experimental campaign aiming to explore the serviceability behaviour of columns of jointless structures reinforced with both conventional rebars and steel fibres recycled from end-of-life tyres. The test set-up is first introduced, involving columns with different reinforcement ratios, squashing load ratios and recycled fibre content. The characteristics, constructability and performance of recycled fibres are discussed. Then the results of the tests are presented and compared with non-fibre reinforced columns, showing improvements in cracking performance. Also, a simplified method of analysis has been compared to experimental results, showing good agreement in the imposed displacement vs. rebar stress behaviour. The main objective of this investigation is to encourage the use of jointless structures by presenting an appealing and sustainable technique to overcome problems such as excessive cracking.

Simplified serviceability design of jointless structures. Experimental verification and application to typical bridge and building structures

In this article an experimental campaign aimed at validating a previously published simplified serviceability design method of the columns of long jointless structures is presented. The proposed method is also extended to include tension stiffening effects which proved to be significant in structures with small amount of reinforcement subjected to small axial loading. This extension allows significant improvement of predictions for this type of element. The campaign involved columns with different reinforcement and squashing load ratios, given that these parameters had been identified as crucial when designing columns subjected to imposed displacements. Experimental results are presented and discussed, with particular regard to cracking behaviour and structural stiffness. Considerations on tension stiffening effects are also made. Finally, the application of the method to typical bridge and building cases is presented, showing the feasibility of jointless construction, and the limits which should be respected.

Serviceability design of columns of long jointless structures

A simplified method for the design or verification of the reinforcement of columns of long jointless structures (usually referred to as integral structures) for serviceability conditions is proposed. The design of the reinforcement of columns of integral structures is generally conditioned by the serviceability limit state (S.L.S.), and in particular by the control of cracking. The main idea behind the method is to simplify the analysis by reducing the behavior of a complex and large structure to that of an isolated column. The proposed method has been tested by comparing its results to a full non-linear analysis of a 200m long reinforced concrete frame. The main aim of the method is to promote the design of integral structures whose development is hindered by the difficulties encountered in their analysis in normal engineering practice.