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Title: The influence of semi-rigid connections on the behaviour of slender structures
Author: Feng, Xiu
ISNI:       0000 0001 3459 4984
Awarding Body: Oxford Brookes University
Current Institution: Oxford Brookes University
Date of Award: 1994
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In the classical analysis and design of slender frame structures, it is normally assumed that the connections of the structures are either rigidly fixed or perfectly pinned. However, the real situation is that most connections often exhibit semi-rigid characteristics. This no doubt has a significant influence on the overall behaviour of the structures such as buckling capacity and deformation. With the aim of evaluating the influence of semi-rigid connections and baseplates on the overall behaviour of slender structures, this thesis is devoted to investigating the properties of semi-rigid connections, particularly the semi-rigid baseplates in pallet racks which are usually used in the storage and materials handling industry, and then evaluating their effects on the buckling and deformation response of the structures. The investigations are carried out with the combination of theory and experiment,a nd with the utilization of a computer approacha nd engineering simplification. The rotational stiffness of baseplatesi s investigatedt heoretically and experimentally aiming at estimating the principal factors that influence the behaviour of baseplates. A beam-compressions pring model is proposedt o calculate the rotational stiffness of baseplates. The compressions pringsa re characterised by the equivalent modulus of subgrade reaction and are used to model the combined action of concrete floor and soil foundation. The initial rotational stiffness of baseplates is determined analytically and the subsequent onlinear rotational stiffness is determinedn umerically using an associatedc omputer program. The investigation showed that the rotational stiffness of baseplatesi s not only dependento n the applied axial loads but also on the subgradew hich supportst he baseplate. The experiments,w hich were conducted in the present work using concrete and timber as subgrade materials to model the effects of different subgrades, support this conclusion. A structural model for buckling analysis is presentedw hich considers the beam-column and column-baseplate semi-rigid connections. The governing equations are derived by the exact analysis of column elements They can be reduced to a transcendental function in terms of buckling load factor. The fundamental critical load of the structure is found from an engineering point of view rather than a purely mathematical point. The domain of the critical load is determined firstly and then a computer iterative approach is developed. The investigation showed that the dependence of buckling loads on the rotational stiffness of semi-rigid connections is significant. A comparison between the predicted results and those of other methods is made. Also proposed is a simplified model for deformation analysis when the structure is subjected to both axial and lateral loads. The second-order analysis is carried out where the P-b effect is considered. The initial imperfection of the structure is taken into account. The Gauss elimination procedure is used to find deformation and ultimate load. The calculated results are compared with those obtained from a finite element analysis computer program LUSAS. As one aspect of the investigation, adjustable telescopic steel props with semi-rigid baseplates are analyzed. The analysis is formulated and programmed in accordance with the new Euro-Norm and the German Standards. The computed results were compared with those of LUSAS and good agreement was achieved. Based on the results obtained, discussion is made on the design of slender frame structuresw ith semi-rigid connections. Also discussed is the procedure for the load capacity check of a slender structure with a given configuration. In addition to the results obtained in the present research about the rotational stiffness of baseplates and about its influence on structural behaviour, the investigation also demonstrated how to evaluate the rotational properties of connections and their effects on buckling and deformation of structures.
Supervisor: Beale, R. G. ; Godley, M. H. R. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Pallet rack structures ; Buckling ; Stability