Master of Science in Structural Engineering Design / Master of Science in Structural Engineeringhttp://dl.lib.uom.lk/handle/123/157592024-03-28T13:52:08Z2024-03-28T13:52:08ZSteel portal frame design for deconstruction and reuseSurendra KIhttp://dl.lib.uom.lk/handle/123/214092023-10-13T01:48:15Z2022-01-01T00:00:00ZSteel portal frame design for deconstruction and reuse
Surendra KI
Today, the world over, much emphasis is focused on the use of sustainable materials
in infrastructure. One of the main attributes that has led to the widespread use of steel
in infrastructure is that is considered sustainable. Steel meets the 3R concept of
Sustainability, Reduce, Reuse and Recycle. While steel components are 100%
recyclable, the manufacture of stronger and better quality steel products has enabled
the design and construction of structures using reduced quantities of steel. Due to
scarcity of raw material, conservation of energy coupled with escalation of steel prices,
it is prudent to design steel structures that can be re-used, thus extending the life cycle
of steel. This is an aspect that has hitherto not received sufficient consideration by
structural engineers.
The focus of this thesis is on extending the life cycle of steel components, with
particular emphasis on the design of single span steel portal framed structures by
considering the aspects of deconstruction and re-use. The scope of the study was
limited to a span range of 20m to 40m and eaves heights of 4m and 6m and typical
vertical action of 10kN/m.
The adoption of haunches hinders the re-use of the rafter. An innovation recently
adopted facilitating the re-use of rafters is that of replacing the haunch at the eaves
with a steel knee brace pinned at either end to the column and rafter. This concept was
investigated and found to be viable within this range of span and eaves heights.
Optimum locations for knee brace connections were found to be 10% of span length
at the rafter end and 3% of the span length from the rafter axis at the column end.
These initial studies indicate that greater attention should be paid on the aspect of
deconstruction and re-use of steel at the preliminary stages of design in order to extend
the life cycle of steel components and thereby enhance the sustainability of steel
structures.
2022-01-01T00:00:00ZDevelopment of earthquake resistant design guidelines for bridges in Sri LankaKumara MAChttp://dl.lib.uom.lk/handle/123/210072023-10-13T00:58:49Z2022-01-01T00:00:00ZDevelopment of earthquake resistant design guidelines for bridges in Sri Lanka
Kumara MAC
Sri Lanka is an island located on the Indo-Australian tectonic plate and the location of the country is far away from the plate boundary where inter-plate earthquakes are possible to occur. However, there are earthquake records during the recent past which have considerable magnitude. Moreover, intraplate earthquake risk is there which is possible to occur without prior warning. Therefore, Sri Lanka is no longer be considered safe from seismic threats.
With the increasing demand to improve the road network in the country, it is necessary to reconstruct existing bridge structures. However, there are no seismic design guidelines to use for bridge design procedure in Sri Lanka.
This study is therefore aims to formulate earthquake-resistant design guidelines for bridges in Sri Lanka. For the purpose of formulating the design guideline, bridge classification into three different important classes is proposed based on the relevant classifications in similar codes such as EN 1998-2:2005 , IS 1893-3:2014 and AS 5100.2-2004. Important factors and return periods are proposed based on the guideline given in EN 1998-1:2004. Further, Elastic response spectrums for rock or hard soil are selected based on the available response spectrum for Sri Lanka. However, there is no response spectrum defined for medium soil and soft soil. Therefore, it is proposed to use the response spectrum available in IS 1893-1:2002 for medium and soft soil since soil and rock types are more similar when both countries lie on the same tectonic plate.
This study proposed a seismic analysis approach for bridges using either EN 1998-2:2005 or AS 5100.2-2004. Moreover, suitable design parameters such as peak ground acceleration values are proposed to select according to the available national data.
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There are three case studies carried out to illustrate the use of developed guidelines for seismic analysis of bridges in Sri Lanka. Three Case studies were carried out for bridges in the category of important class I, important class II and important class III by using the design codes of AS 5100.2-2004, IS 1893-3:2014, and EN 1998-2:2005. For case study 1, base shear values were calculated using the static lateral force method of analysis and three different design codes provided different results of 50kN, 51kN, and 36kN. For case studies 2 and 3, static analysis was carried out using selected three design codes, and response spectrum analysis was carried out according to EN 1998-2:2005 using the response spectrum defined for rock or hard soil of Sri Lanka. Base shear values of the static analysis results provide different values for three design codes. However, a comparison of the results of response spectrum analysis and fundamental mode method of analysis for Eurocode 8-part2 as the basis of analysis, provided similar fundamental period values and base shear values for both methods.
Results of the case studies illustrate that when the design basis is Eurocode 8-Part 2, it provides an average or lower result of base shear value. Since Eurocode 8 provides an opportunity to use it with national choices, it is more suitable to use EN 1998-2:2005 with a national annex for bridge design. Therefore, a developed guideline with national parameters can be used for the seismic design of bridges in Sri Lanka.
2022-01-01T00:00:00ZCost Implications of adopting eurocodes for steel concrete composite bridges in Sri LankaAbeysuriya ANhttp://dl.lib.uom.lk/handle/123/200842023-11-07T04:40:11Z2022-01-01T00:00:00ZCost Implications of adopting eurocodes for steel concrete composite bridges in Sri Lanka
Abeysuriya AN
Construction of concrete bridges gained popularity after the introduction of pre-stressed concrete in 1950s, due to low cost of maintenance and locally available construction material. The concrete bridge industry was developed, so that reinforced and pre-stressed concrete bridges were designed and constructed in Sri Lanka.
Steel being imported material that require maintenance, steel bridge industry was not developed. Although with present high-grade steel, durable protective systems, steel composite bridges offer competitive designs for longer spans, locations with poor ground conditions, accessibility problems due to congested traffic and remote locations.
BS5400-2 (1978) and R.D.A Bridge design Manual remained as the main bridge design standards during past few decades up-to-date. Pre-tensioned beams used in the road network are still produced, and bridges are designed for these standards. BS design standard need to be replaced with Eurocode standard since BS standards will not be updated in future. This study selected UK National Annex for traffic loads (NA to BSEN 1991-2:2003) to compare with current BS 5400-2 loading adopted in Sri Lanka.
Standard simply supported bridge decks with two traffic lanes (carriageway 7.4m) and two footways on either side considered in this study. Standard pre-tensioned concrete beam deck spans 9.04m – 24.54m and composite designs made for this study for spans 31.5m – 50m considered in the comparison of traffic loads of BS5400-2 (1978 & 2006) and Eurocode UK National Annex. Culverts and existing bridge span up to 9.0m were not considered to maintain the simplicity of this study.
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In order to compare deck costs, existing concrete decks were estimated based on Highway Schedule of Rates (HSR) and past construction data. Designs and estimates were prepared for recommended UKNA loading for steel composite bridges for spans 11.5m – 50m. The cost information provided from a steel fabricator and published data together with past construction data were considered in the estimation of composite decks.
This study recommends suitable UKNA loading, to replace current BS loading and identifies economical span range for steel composite bridges designed, when compared with existing concrete bridge types for prices prevailed in 2020. Identical costing process could be repeated with latest prices and HSR rates to for comparison of cost between concrete and steel concrete composite decks in future years.
2022-01-01T00:00:00ZExperimental analysis of curved RC beams strengthened with carbon fibre for flexural and shear capacity enhancementPremalal RPDShttp://dl.lib.uom.lk/handle/123/201242023-11-07T06:04:52Z2022-01-01T00:00:00ZExperimental analysis of curved RC beams strengthened with carbon fibre for flexural and shear capacity enhancement
Premalal RPDS
Among the concrete strengthening applications, Carbon Fibre Reinforced Polymer (CFRP) systems offer better mechanical properties than other alternatives, such as stronger tensile strength, stiffness, and durability. Most of the studies have been focused on strengthening or retrofitting straight Reinforced Concrete (RC) beams using CFRP, fewer on the horizontally curved out of plane loaded RC beams, which are present in novel featured structures worldwide. In contrast to straight beams, the curved beam behaviour possess combined effect of bending, torsion and shear where CFRP application requires a careful selection based on the intended capacity enhancement.
The experimental program includes total 6 nos. of RC beam specimens of fixed curvature casted, 2 beams weak under shear and 2 beams weak under flexure and their control beams. The CFRP strengthening was applied as relevant to evaluate the effectiveness of flexural and shear enhancement. The NSM CFRP plate application and end anchored NSM CFRP for flexure strengthening along with 450/1350 oriented CFRP fabrics at beam sides and increased area of fabric for shear strengthening was focused. The specimens were tested using four point bending test and the ultimate failure load, crack patterns, failure modes and deflection was observed.
The experimental results under flexure concluded that NSM CFRP enhance flexural strength according to the initial cracking load observations. Where end anchored CFRP fabric provided it contribute to additional flexure strength and reduce overall deflection by 23%. Ultimate load carrying capacity of NSM CFRP retrofitted beams were enhanced by 12.1% and 8.4% for respective application. NSM CFRP retrofitted beams showed, lesser crack density and widths. Propagation of the crack which was in the direction of NSM CFRP plate corners is restrained with the use of end anchored CFRP, although its effect over shear capacity enhancement is insignificant. The experimental flexural enhancements are 28.8% and 29.3% less than the theoretically predicted values by ACI 440.2R-17 guide, respectively for NSM CFRP only and end anchored beams, which may have occurred due to the contribution of additionally induced torsional stresses.
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The experimental results under shear concluded that ultimate load carrying capacity of shear retrofitted beams were enhanced by 20 % and 30%. The influence of CFRP retrofitting is higher when the CFRP application area is increased at inner shear span. The experimental shear enhancements are 35.4% and 20.3% less than the theoretically predicted values by ACI 440.2R-17 guide, respectively for side laminated and extra side laminated beams. The intermediate debonding and induced additional torsional stresses may have caused this capacity reduction.
2022-01-01T00:00:00Z