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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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Methods for flexural strengthening of reinforced concrete elements using steel plates

  • Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
  • Date: 2014
  • Subjects: Concrete beams , Plates, Iron and steel , Reinforced concrete , Flexure
  • Type: Article
  • Identifier: http://ujcontent.uj.ac.za8080/10210/380017 , uj:5078 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13649
  • Description: When reinforced concrete elements are incapable of safely sustaining the anticipated load, flexural strengthening may be necessary. Two major construction methods have been reported in literature for strengthening reinforced concrete (RC) elements in bending. These methods include Externally Bonded Reinforcement (EBR) and Near Surface Mounting (NSM). The aim of this paper is review these methods, including the extensive surface preparation that must be performed on bonded elements. Previous investigations have shown that these techniques are effective in salvaging old and distressed reinforced concrete structures. This paper identifies the problems associated with the utilisation of steel plates as strengthening material for RC elements in EBR and NSM techniques.
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Identifying the effects of excessive deflection in reinforced concrete beam

  • Authors: Ogbeifun, E. , Pretorius, J. H. , Mbohwa, Charles , Ogbeifun, E
  • Date: 2014
  • Subjects: Reinforced concrete construction , Concrete beams , Floors, Concrete - Design and construction
  • Type: Article
  • Identifier: uj:5084 , http://hdl.handle.net/10210/13655
  • Description: In framed reinforced concrete structure, the beams transfers the dead and live loads to the column and then to the foundation. When there are observed structural failure in the systems supported by the beam, especially where the beam has a large unsupported clear span at a lower level, before any further detailed investigations are initiated, the functional state of the beams should be ascertained. The correct diagnosis of the source of problem is essential for the design of effective rehabilitation scheme. Simple visual inspection corroborated with field test for true horizontality of the beam can provide the lead information that will guide the client on the scope of further investigations. The case study method of qualitative research was adopted to address the research questions, while the research data was collected by reviewing previous investigation reports on a three-storey building, physical inspection and conducting simple site experiment to identify the lead information. The research outcome reveals that the multiple cracks observed in the partition walls especially in the second floors were as a result of excessive deflections in the beams supporting the first and second floors. Based on recommendation, subsequent investigation confirmed this lead information and appropriate rehabilitation scheme was adopted.
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Repair of reinforced concrete beams with adhesive Bonded steel plates

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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Cold-formed circular hollow sections under axial compression

  • Authors: Dundu, Morgan , Chabalala, Vongani
  • Date: 2014
  • Subjects: Columns, Concrete , Concrete slabs , Reinforced concrete construction , Concrete beams , South African Design Standards
  • Type: Article
  • Identifier: uj:5068 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13639
  • Description: Two series of experiments were carried out to investigate the behaviour of pinned-ended circular hollow section (CHS) columns, subjected to axial compressive load. A total of 30 columns were tested in this investigation; 20 columns in Series 1 and 10 columns in Series 2. The outside diameter-to-thickness ratio (d/t) and the slenderness ratio (KL/r) ranged from 29.7 to 46.4 and 20.8 to 82.2 for Series 1, respectively, and from 55.0 to 62.9 and 10.7 to 34.9 for Series 2, respectively. In general, Series 1 columns failed by overall flexural buckling and, whilst Series 2 columns failed by local ring-type buckling. The test strengths of the columns were compared with the strengths predicted by the South African design standard (SANS10162-1) and the European design standard (EN 1993-1-1).
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Compression tests of Mi Panels

  • Authors: Bukasa, G. M. , Dundu, M.
  • Date: 2014
  • Subjects: Reinforced concrete construction , Concrete beams , Flexure , Concrete - Deterioration
  • Type: Article
  • Identifier: uj:5073 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13644
  • Description: A number of compression tests of Mi Panels are presented. The use of lightweight Mi Panels as building system allows the reduction of construction time and waste in the building environment. The compression tests are performed to simulate the behaviour of the wall, when subjected to vertical loads from the roof. Two LVDTs were placed at mid-height of the panels during the compression tests, to record the lateral displacement. Mi Panels failed by fracturing into two parts at mid-height. No cracks in the panel were observed before overall flexural buckling failure. The tests showed that the panels are capable of carrying the required loads, and can be used in place of brick walls.
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Flexural tests of Mi Panels

  • Authors: Bukasa, G. M. , Dundu, M.
  • Date: 2014
  • Subjects: Concrete beams , Flexure , Fiber cement , Fiber-reinforced concrete
  • Type: Article
  • Identifier: uj:5074 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13645
  • Description: Two series of flexural tests on 2700x600x75 mm Mi Panels are presented. The inner core of these lightweight panels is made from mixing polystyrene beads called Neopor, high strength cement, and water. A chemical is used as binding agent to bond the inner core to the external fibre cement sheets of 4.5 mm thickness. The experimental programme consists of two series of tests with different loading conditions; the first series has line loads at one-third point from each end support and the second series has line loads, at quarter and three quarter span of the panels. All flexural tests are performed to simulate the behaviour of the wall, when subjected to wind loads. Although the panels failed by fracturing, the tests showed that the panels are capable of carrying the required loads.
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