A comparison investigation into analysis methods to determine the buckling capacity of South African cold-formed steel lipped channel sections
- Authors: Van Vuuren, Johan
- Date: 2020
- Subjects: Buckling (Mechanics) , Steel, Structural , Steel - Cold working , Columns, Iron and Steel , Channels (Structural members)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/480368 , uj:43484
- Description: Abstract: Columns play a critical role in any steel-framed building and, through compression, transfer loads from the elements above to the supporting base. Due to structural failures of compression members, an investigation of the various design methods that are available is presented in this document. With the recent tendency for design codes in South Africa to migrate to the Eurocodes, as seen in the SANS 10160 series [1], it is reasonable to assume that the SANS 10162-2 might be revised based on the Eurocode 3 design procedures. For the design of cold-formed steel compression members, an overestimation may cause increased financial costs and, conversely, an underestimation may cause structural failures. However, there is an urgent need for the body of knowledge to be expanded. Therefore, this research presents the evaluation of buckling capacities of five different column lengths using five different methods: 1) experimental tests; 2) Eurocode 3; 3) SANS 10162-2 through the Direct Strength Method (DSM); 4) simplified Finite Element Analysis (FEA), i.e. only beam modelling elements; and 5) finely graded FEA, i.e. plate modelling elements. All columns have a 75 x 50 x 20 x 2.0 (h x b x c x t mm) cold-formed lipped channel cross-section... , M.Ing. (Structural Engineering)
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Effects of the width-to-thickness ratios of steel plates bonded to the soffit of reinforced concrete beams
- Authors: Rakgate, Sylvester Mokgokone
- Date: 2017
- Subjects: Plates, Iron and steel , Concrete beams , Steel, Structural , Flexure
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242353 , uj:24994
- Description: M.Ing. (Civil Engineering) , Abstract: The use of epoxy-bonded steel plate (EBSP) is becoming a well-known solution in the field of civil engineering around the world for strengthening structural elements such as beams, columns and slabs. This thesis presents an experimental study aimed at investigating the flexural behaviour (structural behaviour) of simply supported under-reinforced concrete (URC) beams, strengthened in flexure by externally-bonded steel plates (EBSP) with varying width-to-thickness ratio. This required an experimental investigation, which took place at the material laboratories at the University of Johannesburg (UJ), South Africa. The experimental program was carried out on 17, 175 x 300 x 3200 mm rectangular reinforced concrete (RC) beams. Two beams were not strengthened with steel plates and they were considered as control specimens, whilst the remaining beams were categorised into three groups with five (5) beams in each group. The first group of beams was externally strengthened with 4 mm steel plates, the second group was externally strengthened with 6 mm steel plates and the third group was externally strengthened with 8 mm steel plates, in flexure. Furthermore, in each group, the width of the bonded steel plate varied from 75 mm to 175 mm, with increments of 25 mm. All the beams were tested simply supported under two-point static loadings until failure over a clear span of 3000 mm. To achieve the goals of this experimental investigation, the load-deflection response, strain distribution at the mid-span of the bonded steel plate, cracking load, crack patterns and associated failure modes of the tested specimens were recorded. From the experimental results, it is observed that the externally bonded steel plates led to an increase in flexural stiffness, maximum load carrying capacity, cracking load, decrease in vertical deflections and crack-widths as compared to the control beams. Furthermore, there is a limit to width-to-thickness ratio of the steel plate which the premature shear or bond failure occurs without beams achieving their full flexural capacity.
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Repair of cracked reinforced concrete beams with adhesive bonded steel plates
- Authors: Ngidi, Sandile Daniel
- Date: 2017
- Subjects: Concrete beams - Maintenance and repair , Reinforced concrete construction , Plates, Iron and steel , Steel, Structural
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269693 , uj:28652
- Description: M.Ing. (Civil Engineering) , Abstract: Concrete structures often suffer from cracking and deterioration caused by factors such as impact and dynamic loading, static overload and construction faults. This requires immediate repair to prevent further degradation and to restore structures integrity. Externally bonded steel plates are used to repair such damaged concrete structures in a number of projects in various parts of the World, but their overall performance is still not fully understood. The main objective of this study is to investigate the flexural behaviour of pre-cracked reinforced concrete beams, repaired by bonded steel plates on their soffit, using epoxy adhesives. This implied an experimental investigation, which took place in Material Laboratory of the Department of Civil Engineering Science at the University of Johannesburg. Twelve full-scale beams of 175 mm wide x 300 mm deep x 3200 mm long were pre-cracked, repaired with steel plates and tested to failure in flexure under a two-point loading. Two variables were included in this investigation, namely; plate size and loading conditions. The plate size was varied by changing its width, which ranged from 75 mm up to 175 mm, in increments of 25 mm and the beams were pre-cracking at serviceability load and at 85% of the maximum load. During the experiments, the following aspects were evaluated and recorded regarding the response of tested beams: flexural strength, stiffness, maximum deflections and failure modes. Externally bonding the steel plate to the pre-cracked reinforced concrete (RC) beams resulted in increased stiffnesses and maximum load capacities up to 153% and decreased in the maximum midspan deflections up to 38%. The strength and rigidity of the repaired beams were found to increase with increasing the width-to-thickness ratio of the steel plate from 12.5 to 29.17. The results also showed that bonded external steel plate can only enhance the maximum load capacity of the repaired beams to a limited extent. There exists a limit in the width-to-thickness ratio for which the load can increase. The experimental results showed that the structural integrity of the repaired beam not only can it be restored but also enhanced. The bonded external plate contributed more to the control of maximum load capacities than to the control of deflections.
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Effect of steel area reduction on flexural behaviour of spalled concrete beams
- Authors: Mutheiwana, Maanda Emmanuel
- Date: 2014-05-29
- Subjects: Concrete beams , Steel, Structural , Concrete - Deterioration , Flexure
- Type: Thesis
- Identifier: uj:11220 , http://hdl.handle.net/10210/10813
- Description: M.Tech. (Civil Engineering) , Every year, millions of Rands are being spent in rehabilitation, repairs and maintenance of reinforced concrete structures projects around the country due to corrosion. There are a number of studies and investigations that have been done recently to address the effect of corrosion on reinforced concrete structures. Concrete provides an ideal environment for steel, supplying both physical and chemical protection from corrosive attack. The effect of corrosion on reinforced concrete structures contributes to the reduction of steel cross sectional area, weakening the bond strength between steel and concrete and thereby reducing the ductility, deflection capacities and load carrying capacity of the structure. In this research, five series of three samples each of reinforced concrete beams were fabricated, some with reduced cross-sectional area and with exposed bars to simulate loss of bonding through spalling. The structural performance of these beams was tested in terms of maximum load carrying capacity, deflections and ductility ratio. The main conclusions are as follows: As little as 1 % loss in mass of tension steel resulted in a load carrying capacity decrease of 6.9 % Beam deflection increased by a factor of 1.5 times when the steel mass loss level was 14% 5 % steel loss in mass resulted in a 16.5 % decrease in relative ductility.
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Local buckling of axially loaded type 3CR12 corrosion resisting steel built-up columns
- Authors: Human, Johannes Jurie
- Date: 2014-02-12
- Subjects: Steel, Structural , Reinforced concrete , Reinforcing bars
- Type: Thesis
- Identifier: uj:3914 , http://hdl.handle.net/10210/9278
- Description: M.Ing. , Design parameters for ferritic type stainless steel structural members do not exist and is needed. This study attempts to find design parameters for ferritic type stainless steel compression elements. The ferritic type stainless steel under consideration in this study is Type 3CR12 corrosion resisting steel, which is a modified Type 409 stainless steel. The purpose of this study was to determine the limiting web width-to-thickness and flange width-to-thickness ratios for the prevention of local buckling in axially loaded hotrolled Type 3CR12 corrosion resisting steel columns. Experimental data was obtained in an ongoing study on the limiting width-to-thickness ratios for elements in compression. No conclusion on this aspect can be reached at this stage of the investigation
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The local buckling strength of stainless steel beam webs subjected to a stress gradient
- Authors: Van Tonder, Pierre
- Date: 2012-09-10
- Subjects: Buckling (Mechanics) , Strength of materials , Steel, Structural , Steel, Stainless
- Type: Mini-Dissertation
- Identifier: uj:9820 , http://hdl.handle.net/10210/7224
- Description: M.Ing. , In this study the results on the local buckling strength of web elements in lipped channel beams are presented. The steels chosen for this study are AISI Type 304, 430 and Type 3CR12 stainless steels. Lipped channels with varying web height-to-thickness ratios were tested in pairs with the lips and flanges facing inward in a four point loading configuration. It was found that the theoretical results is a good representation of the experimental results if the plasticity reduction factor was set equal to 1.
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