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Title: Direct design of reinforced concrete structures using nonelastic stress fields
Author: Bensalem, Abdelmadjid
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1993
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This research work is mainly concerned with the service and ultimate load behaviour of reinforced concrete slabs and deep beams designed using nonelastic stress fields. The nonelastic stress fields, at design ultimate load were determined using a finite element procedure using uncracked stiffness, along with von Mises yield criteria. The orthogonal reinforcement was provided based on Wood-Armer and Nielsen-Clark yield criteria, respectively for slabs and deep beams. The experimental study consisted of six simply supported slabs, two of which were additionally supported by a column in the middle and two simply supported deep beams with different span depth ratios. The first and the third slab were designed using 70 and 30% of plasticity stress distribution whereas the rest of the models were designed using 100% plasticity stress distribution. The major parameter varied was the levels of plasticity to observe their effect on the behaviour of the structures studied. A nonlinear finite element program based on plate bending layer approach for slabs and inplane formulation for deep beams was used to study the behaviour of the designed models. The steel is modelled as embedded and smeared and assumed to be elastic perfectly plastic or with allowance for strain hardening. Kupfer-Hilsdrof criterion was adopted as the failure criterion for concrete. Smeared crack approach was used to account for the development of concrete cracks. Good agreement between experimental and numerical results was obtained. Results indicate that all the models designed by this method showed, when tested, satisfactory behaviour both at service load and ultimate load. Both deflections for slabs and crack width for slabs and deep beams were within acceptable limits at service loads. All the models failed in a ductile manner with cracks spread over the structure. For all the models the failure load was above the design ultimate load. It is concluded that the proposed design procedure produces a natural smoothing out of the stress peaks, leading to a reasonably uniform steel distribution over the slab avoiding congestion in the critical areas of slabs, which is desirable in practice. For simply supported deep beams it appears that no significant redistribution of stresses takes place and the use of elastic stress field in the design is sufficient. A nonlinear procedure which treats reinforced concrete as an elasto-plastic material is developed. This is applied to the analysis of inplane and plate bending problems. The results appear encouraging.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available