CERIS - 2011

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Browsing CERIS - 2011 by Author "Baskaran, K"

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    State of the art of concrete paving blocks in Sri Lanka (CPBs)
    (Department of Civil Engineering, University of Moratuwa, 2011) Baskaran, K; Gopinath, K; Ratnayake, N
    It is in the last five years that the stakeholders of concrete paving blocks (CPBs) are awakening to engineer the CPBs in Sri Lanka. Although large scale production of CPBs has already flourished in Sri Lanka, their adherence with stringent standards (both Sri Lankan and International) remains dubious. This reluctance to meet the performance and durability criteria according to codes of practices, curtails the life span of concrete block paved roads to a greater extent. The scope of the present paper is limited to verifying whether the local concrete paving blocks are made on par with international standards. Sample blocks were obtained from local CPB manufacturers and investigated.Though these blocks met the criteria in Sri Lankan Standard for CPBs for strength classes 2, 3, 4 roads, none of them met the compressive strength criteria for strength class 1 roads. Besides, tensile strength requirement specified in the BS EN 1338: 2003 was met by none of the blocks tested. Since, Sri Lankan Standard is planned to incorporate splitting tensile strength as the dominant measure to assess paving blocks in the near future, this study also attempted to identify a mix proportion to meet the splitting tensile strength requirement specified in BS EN 1338: 2003. When CPBs were casted using CPB making machine, an intolerable strength deviation was observed. A series of tests were conducted to explore the reasons for this.The outcome of which would help the small scale manufacturers to keep strength variations within a tolerable range, when they are using CPB making machines.
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    Strength assessment of steel towers
    (Department of Civil Engineering, University of Moratuwa, 2011) Baskaran, K; Jeneevan, G; Jayasinghe, JPLM; Hettiarachchi, HHANC; Ratnayake, N
    In the recent Abstract: past, considerable number of tower failures happened in telecommunication sector and power transmission sector in Sri Lanka. However, no lessons were learnt and there is still a vacuum in strength assessment of towers. The objectives of this research are conducting data survey on failed towers in Sri Lanka and identifying causes, analysing failed electric transmission towers using finite element analysis and finding the causes for the failures and developing simple methods to check tower capacity based on available simplified models. Four telecommunication towers and a transmission tower were considered to identify the failure reasons. Structural analysis of a transmission tower was done using a finite element analysis package, SAP2000. A manual method to analyse 3D trusses was developed by combining unit load method and tension coefficient method. To ensure the validity of proposed analysis methods, a simple tower model was erected, structural analysis was done using both SAP 2000 package and manual method, failure loads were predicted using SAP 2000 package, loading was conducted and results were analysed. It is concluded that preliminary structural analysis with a specialised or a common structural analysis package, has to be incorporated into prevailing steel tower design procedures. Frequently admitted reason for telecommunication tower failures is tornados. However, nowadays towers are being overloaded with antennas without proper consultation. Therefore it is essential to carry out a detailed technical failure analysis to identify the reasons of failures. All these procedures and results obtained are discussed in detail in this paper.
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    Strength enhancement in concrete confined by spirals
    (Department of Civil Engineering, University of Moratuwa, Sri Lanka., 2011-12) Kaneswaran, U; Reginthan, J; Perera, HMP; Baskaran, K; Ratnayake, N.
    The strength and ductility of the concrete Abstract: can be enhanced by confinement.lt can be achieved in many ways. Using spirals is one of the ways to enhance the strength by confinement. The confinement effect in concrete by spirals can be applicable to enhance the load carrying capacity of columns and shear carrying capacity of beams and flat slabs. This effect prevents structures from catastrophic failures during earthquakes. In this research study, experiments were conducted to determine the anchorage depth of the spiral, the shear enhancement in beams due to confinement by spirals and increment in failure load of flat slab panels a when spiral is used as a shear resistor. The actual shear carrying capacity and theoretical shear carrying capacity of the beams were checked using average integration method and discrete method.The experimental results indicated that the shear carrying capacity of the beam was enhanced by 35.7% for 30mm pitch spiral, 26.8% for 45mm pitch spiral and 16.1% for 60mm pitch spiral. The actual shear carrying capacity based on the experimental results matched closer to the value obtained by the average integration method. The failure load of the flat slab panel was increased by 12.3% when spiral was used as shear resistor.