CERS - 2014

Permanent URI for this collectionhttp://192.248.9.226/handle/123/17777

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item: Conference-Abstract
Proceedings of the Civil Engineering Research Symposium 2014 (Pre Text)
(2014) Hettiarachchi, MTP
item: Conference-Full-text
Investigation of movements in block masonry walls
(Department of Civil Engineering, University of Moratuwa, 2014-03) Nandapala, K; Peiris, A; Senavirathna, R; Nanayakkara, D; Hettiarachchi, MTP
One of the main concerns in block masonry is cracking, mainly due to thermal and moisture movement. There are some standards which give guidelines and recommendations to control cracking, but these cannot be directly used for local masonry due to the differences in properties of masonry units used, environmental conditions and the construction techniques. This experimental study is mainly carried out to investigate the extent of movement in block masonry and also to find the influence of mortar mix, initial condition of blocks, type of blocks used and wall thickness on movement in block masonry. Sixteen blockwork panels were constructed to study the selected test parameters on movement in block masonry. The movement was monitored for a period of one year, using dial gauges which were permanently fixed to each panel. From the results, it is found that the movement in block masonry is influenced by the initial moisture condition of the blocks. A significant influence of mortar mix and thickness of wall on movement is not seen from the experimental results. It was observed that the movements reached the maximum values within 8 ~ 9 months after construction of blockwork panels. It is found that the highest shrinkage strain of 0.02% is recorded in the masonry panel constructed with saturated solid blocks and 1: 6 mortar mix.
item: Conference-Full-text
Rapidly deployable structures for the tourism industry in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2014-03) Mustapha, MSN; Lewangamage, CS; Thompson, LM; Hettiarachchi, MTP
This research involves the concept of creating rapidly deployable ecofriendly cabanas for the tourism industry in Sri Lanka. The cabanas are to be pre-fabricated; thus could be purchased off the shelf and assembled at site. The tourism Industry in Sri Lanka has witnessed rapid growth since May 2009 and the concept of deployable structures could benefit largely in improving the accommodation facilities in the country. The primary objective of this research is to conceptualize the design of a structure such that it could be dismantled within three days and re-assembled within three days without the use of any heavy machinery. The structure is expected to be eco-friendly, and energy' efficient. Furthermore all elements of the structure could be transported by a single container. This research explains the potential advantages of having deployable structures in Sri Lanka's tourism industry such as speedy construction, transportability, reusability, low initial investment, instant cash flows, promoting the concept of effective and efficient land use and ecofriendly tourism. In addition important considerations such as membrane selection, floor truss arrangement, footing arrangement, arched beams as well as sustainability are also discussed. This research finally analyses a real life example of a deployable structure for the tourism industry and the content of this research includes primarily the knowledge gathered during the design phase of this project. This research is presented with the sole intention of disseminating information that would be considered useful in such future projects that could uplift and enhance the tourism industry in Sri Lanka.
item: Conference-Full-text
Pros and cons of using structurally insulated panels in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2014) Jayathilake, L; Baskaran, K; Hettiarachchi, MTP
Structurally Insulated Panels (SIPs) are extensively used in energy efficient buildings all over the world. SIPs can be simply introduced as a building material consisting of an insulating layer in between two structural wythes. Since SIP technology is fairly new to Sri Lanka, only few studies have been carried out to check thesuitability of SIP technology in Sri Lanka. SIPs can be used as walling materials, roofing materials and for slab construction instead of conventional building materials such as burnt clay bricks, cement sand blocks or conventional reinforced concrete slabs. This paper describes an experiment carried out to determine the thermal performance of SIP wall, Cement block wall and Burnt clay brick wall model houses. Further,this presents the results obtained from a computer simulation regarding the cooling loads required for above mentioned models. A cost comparison has been done to evaluate the costs of various wall construction techniques used in Sri Lanka. As a whole, this paper describes pros and cons of using SIPs in Sri Lanka.
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Comparative study on strengthening methods of steel towers
(Department of Civil Engineering, University of Moratuwa, 2014-03) Ganadhiepan, G; Baskaran, K; Hettiarachchi, MTP
Steel towers are widely used in the telecommunication and power transmission sectors. Failure of these towers causes direct and indirect losses and disruption to the services provided by those towers. As a result, industries and general public face difficulties and the productivity of the country also gets affected. Considerable number of tower failures has taken place in both power transmission and telecommunication sectors of Sri Lanka in the recent past but only a little amount of studies has been done so far. Testing at least a tower in a transmission line is mandatory in the power transmission sector of Sri Lanka. Generally these tests are carried out at the Structural Engineering Research Centre in Chennai. It has been observed that several towers fail prematurely under normal loading conditions during full scale tests, indicating lack of strength of towers. The objectives of this study are analysing tested towers using finite element method and comparatively studying different techniques of strengthening of towers. A general purpose finite element analysis program SAP2000 was used for the modelling and analysis of towers. Finite element model of a tower which has been tested to full scale was developed and validated in SAP2000. Then different methods of strengthening were carried out to the validated model to comparatively study the effect of each method on the strength of the tower. The findings are presented in this paper.
item: Conference-Full-text
Study on waterproofing methods used for concrete slabs
(Department of Civil Engineering, University of Moratuwa, 2014-03) Fonseka, R; Baskaran, K; Ekanayake, LL; Hettiarachchi, MTP
A building or a structure requires waterproofing, if the building materials are not watertight enough on their own. Therefore, waterproofing has become an essential component of a structure to protect its aesthetic appearance, prevent structural damages and for the safety of the occupants. For concrete slabs, major objective will be to stop the water intrusion into the interior of the building at various locations under various exposure conditions. Accordingly the type and the method of waterproofing required may vary with the location and exposure conditions. In the construction industry, many commercially available materials are used for waterproofing ground slabs, roof slabs and bathroom floors. In this research, field surveys were done to identify the types of waterproofing material, different methods of applications and quality controlling measures regarding to waterproofing. Furthermore, issues related to waterproofing were studied to identify common problems which can be arrived in a functioning building. Then the rectifying methods and their performance related to such issues were also studied. A laboratory test serieswas performed on commercially available waterproofing materials to check their suitability. After applying waterproofing materials ontest specimens, they were checked for water absorption under laboratory conditions for 24 hours. Furthermore specimens with integral admixtures were tested for compressive strength to identify any increase in their compressive strength due to crystalline formation.
item: Conference-Full-text
Modelling of structural failures in RC beam elements using ANSYS
(Department of Civil Engineering, University of Moratuwa, 2014-03) Rokilan, M; Baskaran, K; Hettiarachchi, MTP
Simulation of failures using Abstract: laboratory experiments will be expensive and time consuming. To overcome these problems making use of finite element methods and advantages of computational software are key considerations. However, proper simulation of structural behaviour is a key factor in the use of FEM analysis. Worldwide a lot of research studies have given attention in this context but in Sri Lanka, concern on this point is considerably less. This paper contains: identification of type of elements like solid-65 and link-8, material models, boundary conditions and other relevant modelling parameters suitable to model structural failures in RC structural elements using ANSYS. Further it seeks to identify the suitability of discrete modelling of reinforcement model. The initial crack formation, failure load and load-displacement curve of beams from laboratory experiments are compared with the nonlinear finite element models using ANSYS to ensure accuracy of model parameters. The accuracy of model is further checked with mesh density and analysis type by conducting different model analysis by changing the parameters and the observations are reported. This paper concludes simulation of flexural failure can be done using ANSYS by small displacement static analysis (equilibrium equations are constructed based on initial position) or large displacement static analysis (equilibrium equations are constructed based on deflected position). However simulation of shear failure is a difficult task since ANSYS has limitations in modelling shear failure using large displacement analysis or small displacement analysis. Further difficulty to converge a solution can be reduced by large displacement static analysis.
item: Conference-Full-text
Study of torsional buckling behavior of carbon nanotubes using molecular dynamics simulations
(Department of Civil Engineering, University of Moratuwa, 2014-03) Dodangoda, MT; Dilrukshi, KGS; Hettiarachchi, MTP
An accurate study of mechanical behavior of CNTs is vital to understand their response under mechanical loading in their applications. Much experimental and analytical work has been done to quantify the mechanical properties of CNTs over the past two decades. However, limited studies have been reported related to torsional behavior and estimation of shear modulus. The reported values of shear modulus of CNTs in the literature also shows considerable variations revealing the effects of the method used in the predictions. This paper reports the study carried out to investigate the effect of different parameters in estimating shear modulus and torsional buckling behavior of CNTs using molecular dynamic (MD) simulation method. MD simulator called largescale atomic/molecular massively parallel simulator (LAMMPS) is used in this regards. The effects of potential function (REBO and AIREBO) used to define atomic interaction and ratios of the CNT considered in simulation were studied with respect to Armchair and Zigzag CNTs with different diameters. The results of the studyrevealed that the effect of the CNT aspect ratio for estimating the shear modulus can be eliminated by using the CNTs with aspect ratio above 12. However, potential function use for the simulations has considerable impact on the results.
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Investigation of the properties of limestone concrete
(Department of Civil Engineering, University of Moratuwa, 2014-03) Hemadasa, MBC; Dilrukshi, KGS; Hettiarachchi, MTP
More than seventy percent of the volume of concrete is occupied by aggregates. AggreSates w^h undesirable qualities will have an adverse effect on durability and structural performance of concrete. Though gneiss is normally used as coarse aggregates in production of concrete, due to their unavailability in the region, limestone is used as coarse aggregate for production of concrete in Northern Sri Lanka, without appropriate investigations. In this study, impact of limestone aggregates on concrete properties such as slump, initial setting time compressive strength, flexural strength, etc. were investigated under laboratory conditions and the results were compared with the concrete made with normal aggregates. Two types of limestone aggregates were used for this purpose, red limestone which was collected from YValikamam west, Jaffna and white limestone, which was collected from Chavakachcheri area. Abstract: It was found that water absorption of limestone aggregates is 50% higher than that of the normal aggregates. Also, workability and compaction ability in limestone concrete are significantly lower for a given w/c ratio compared to normal aggregate concrete. However, compressive strength and flexural strength are found to be the same as the normal aggregates. Also, results indicate that red limestone aggregates have better performance than the white limestone aggregates.
item: Conference-Full-text
Determination of suitability of the limestone aggregates as coarse aggregate for concrete
(Department of Civil Engineering, University of Moratuwa, 2014-03) Perera, MUD; Dilrukshi, KGS; Hettiarachchi, MTP
The use of limestone in the construction industry has been increasing due to its potential as aggregate. Some of the benefits of limestone include good strength, low possibility of alkali-silica reaction and the decrease in drying shrinkage in concrete. In the northern part of the Sri Lanka, limestone is used as aggregate in concrete due to its availability'. The aim of this research is to observe, evaluate, compare and discuss general characteristics of the limestone aggregate in the northern part of Sri Lanka and check the suitability of the limestone as coarse aggregates in concrete. There are two different kinds of limestone there, namely Red limestone and white limestone. Then experiments are conducted for both kinds of limestone together with the normal coarse aggregates. The properties of density, water absorption, particle size distribution, Flakiness Index, Los Angeles Abrasion Value, Aggregate Impact Value, Aggregate Crushing Value and Soundness of the aggregate are observed. The results are compared with the properties of the coarse aggregates and then suitability of limestone aggregates is evaluated.
item: Conference-Full-text
Evaluation of seismic performance of existing reinforced concrete buildings in Sri Lanka using pushover analysis approach - a case study
(Department of Civil Engineering, University of Moratuwa, 2014-03) Milinda, ALDN; Lewangamage, CS; Hettiarachchi, MTP
Evaluation of seismic performance of existing buildings is vital to reduce their seismic vulnerability. Performance can be evaluated by the interaction between structure's capacity and the probable seismic demands. After the evaluation, suitable retrofitting methods can be used to enhance performance by modifying the capacity. In this paper the performance of a four storied reinforced concrete building was was SAP2000 finite element analysis software package was used to obtain the capacity curve of the building. The performance was evaluated using the capacity spectrum method proposed by ATC40 under the application of seismic demands derived from ATC40 document and AS1170.4 (2007) standard.Results showed that the performance of the building is satisfactory in both X and Y directions for all seismic demands determined using ATC40 document and ASH70.4 (2007).
item: Conference-Full-text
Condition assessment of steel bridges in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2014-03) Chathuranga, KADK; Lewanagamage, CS; Hettiarachchi, MTP
The majority of steel bridges in Sri Lanka have been built more than 100 years ago. Most bridges have been subjected to changes such as deterioration due to corrosion, mechanical damage due to fatigue and repair due to maintenance. Therefore condition evaluation of such bridges is vital to ensure public safety. This paper presents condition assessment of selected steel bridges in Kaluthara district. The task is pursued through visual observations. Two mathematical models have been developed in this research to evaluate the condition of bridges. The Analytical Hierarchy Process was applied to obtain the priority vector of bridge elements and important factor of bridge elementswere used to obtain the overall bridge condition index. The modified overall bridge condition index is employed to assess the bridge condition. The results obtained from four selected steel bridges are presented in this paper.
item: Conference-Full-text
Study on elastic modulous of carbon nanotubes using molecular dynamic simulations
(Department of Civil Engineering, University of Moratuwa, 2014-03) Perera, LNPT; Dilrushi, KGS; Hettiarachchi, MTP
CNTs are cylindrical nanostructures having a range of potential applications in nanotechnology. Therefore, an accurate study of mechanical behavior of CNTs is vital. Elastic modulus is an important parameter which is used to predict the mechanical performance of CNT. Molecular Dynamics (MD) is a widely used numerical method which provides a proper balance between accuracy and efficiency in studying nano systems and estimating mechanical properties of CNTs. This study has focused on studying the effect of potential function and Length/Diameter ratio of CNT during the prediction of elastic modulus using MD simulations. Study was done by MD simulations of CNTs subject to tensile test using LAMMPS (large-scale atomic molecular massively parallel simulator) molecular simulator. Most commonly used potential functions; REBO (Reactive Empirical Bond Order) and AIREBO (Adaptive Intermolecular Reactive Empirical Bond Order) were used on studying their influence on CNTs of Zigzag and Armchair chiralities. Results revealed that effect of aspect ratio can be eliminated by using the value CNT of Length/Diameter more than 12. Also, irrespective of the chirality, the surface elastic modulus calculated using the AIREBO potential function was higher than that of REBO potential. Both predict higher elastic modulus value for Zigzag CNTs than Armchair CNTs with negligible variation of values with the increase of CNT diameter.
item: Conference-Full-text
Local construction companies and mega projects: foreign presence in the Sri Lankan construction industry
(Department of Civil Engineering, University of Moratuwa, 2014-03) Jayasooriya, NK; Ekanayake, L; Hettiarachchi, MTP
The Sri Lankan Construction Industry has been booming for the past few years, with the emergence of several mega projects. Mega Projects are currently led by foreign consultancy and construction companies with the foreign aid, and this has caused several concerns in the local construction industry. This research identifies the issues and constraints relating to the local construction companies, when entering into Mega Projects. Further appropriate solutions for the identified issues have also been provided in the research, with the required justification. The research methodology comprises literature review, incorporated with a one to one discussion with the professionals in the industry, including Engineers, Architects,Managers, CEOs, Government Officials, Banking Sector representatives, Foreign Construction Company representatives, and a questionnaire survey carried out with 32 professionals related to the construction Industry. As a conclusion, the research provides the best course of action, for the two major issues identified, with justifications and the research would be a base for the future research to further conduct thorough research on the solutions identified in this research.
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Traffic engineering solutions for minimizing delays and risks at roundabouts
(Department of Civil Engineering, University of Moratuwa, 2014-03) Devasurendra, KW; Perera, L; Bandara, S; Hettiarachchi, MTP
Introduction of a roundabout is a proven method of minimizing delays and risks at an intersection simply due to the reduction in number of conflict points, implementation of give way rule, single directional circulation and reduced speed due to the lateral displacement. However, there arestill opportunities and desires for improvements in reducing the delav and increasing the safety at roundabouts. The safety risk and delay is significant when vehicular volume is high. Roundabout performance can degrade if precautions are not taken eitherduring the design or the operation phases. Therefore this study is focused on seeking traffic engineering solutions to minimize the delav and risk of accidents at roundabouts to be implemented at design and construction stages. During the study, it was realized that a solution should be obtained through both literature reviews and data analysis. Therefore a comprehensive literature review was carried out on related sub topics. Crash and geometric data were collected for two normal roundabouts and analysed. Increasing the diameter of the central island up to the required level specified by the guidelines, decreasing the approach curve radius, elevating the circulating carriageway with respect to the approach carriage by introducing a ramp for the entering vehicles are proposed for the roundabouts as traffic engineering solutions.
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Engineering solution to minimized delays and safety risk at Dehiwala flyover
(Department of Civil Engineering, University of Moratuwa, 2014-03) Yahampath, B; Bandara, S; Perera, L; Hettiarachchi, MTP
Traffic congestion is one of the most imperative problems in almost all countries Flyovers are usually used all over the world to address the traffic congestion, especially at intersections. Advantages of grade separation are; less interruption to traffic flow, higher speed and reduces the scope for accidents. In Sri Lanka also flyovers are used to address the delavs and the safety risk at highly congested intersections. Dehiwala intersection was also replaced by a flyover in order to eliminate the traffic congestion. However, congestion and accident trends have not been reduced yet. There are many factors that contribute to increased congestion levels especially during peak periods and the issues behind the increase in accidents at Dehiwala junction. Engineering solutions based on traffic and highway engineering principles can effectively be used to improve the traffic flow and reduce traffic accidents at this location. Accident data analysis, speed and travel time surveys were used to compare the conditions at present and before construction of the flyover. Moreover vehicle movement pattern, road geometry and adjacent land use activities can be used to evaluate the impact to the Dehiwala flyover. Geometry of the road need to be improved as it will not generate significant speed difference between two adjacent sections as well as not generate bottlenecks at the entrances of the flyover. Stopping of buses within 75m from the junction and vehicle parking within 50m range from the intersection need to be discouraged by using regulatory methods.
item: Conference-Full-text
Water treatment using sludge blanket clarifiers
(Department of Civil Engineering, University of Moratuwa, 2014-03) Nithini, TAS; Rathnayake, N; Hettiarachchi, MTP
A sludge blanket clarifer is a treatment unit combining flocation and upward flow sedimentation, which is more efficient compared to the conventional sedimentation tank. It has the abiltiy to treat the water at a faster rate, resulting in less space requirement. The performance of the blanket appears to directly depend on the raw water quality, coagulant concentration, temperature and up flow velocity. However, there are no direct relationships available to help the operators to adjust these variables to obtain satisfactory performance of the clarifier. Hence it is ksential to identify a characteristic that can be used as an indicator to monitor the sludge blanket. A study of literature showed that a parameter called "sludge cohesion coefficient (SCC)" of sludge has been used in France (Degremont, 1991) to characterize the sludge blanket. However, the procedure given was not clear, and parameters to characterize performance of sludge blanket clarifiers in the tropical environments could not be found in the literature studied. Therefore this research was conducted to study the behaviour of a sludge blanket using the parameter SCC, which was done in two stages. During first stage development of a standard test procedure and introduction of cohesion coefficient ranges which be expected under tropical climatic condition were done. Under this stage several laboratory tests conducted and a test procedure was finalized. In the second stage, using the developed test can were procedure, SCC of synthetic raw water samples was measured to develop relations between the SCC and other variables. Results showed that there is an optimum range of alum dose that produced the sludge blanket with the highest SCC under controlled raw water conditions.
item: Conference-Full-text
Hydraulic performance of rubble mound breakwaters
(Department of Civil Engineering, University of Moratuwa, 2014-03) Hettiarachchi, SSL; Odara, MGN; Godagedara, TH; Herath, HHHB; Hettiarachchi, MTP
Breakwaters are widely used to mitigate the adverse impacts of ocean wave action. Breakwater failures that occurred during late seventies and early eighties, have highlighted the need for further investigations on breakwaters in terms of their hydraulic performance. This paper presents the hydraulic performance of conventional rubble mound rock armoured breakwaters and concrete armoured rubble mound breakwaters, statically stable berm breakwaters and reshaping berm breakwaters based on the re-analysis of large scale model tests.
item: Conference-Full-text
Tsunami hazards: energy dissipation and impact mitigation using bio shields
(Department of Civil Engineering, University of Moratuwa, 2014-03) Jayawardena, DMSS; Hewageegana, VH; Ratnasooriya, AHR; Hettiarachchi, MTP
Tsunamis can cause severe destruction in coastal areas. Though the tsunami hazard itself cannot be mitigated nor eliminated, the vulnerable element can be protected by a variety of mitigation measures. Bio shields, including coral reefs, coastal sand dunes and vegetation have been known to provide protection against tsunami inundation. The protection provided by bio shields was evident after the Indian Ocean Tsunami in 2004 in many of the countries affected.*In view of these circumstances, attention was focused in this study to identify the capacity of protection provided by bio shields. Small scale physical model tests have been carried out to identify the mitigation characteristics of bio shields in the form of coastal vegetation. This study focused on detailed analysis of the results obtained by model tests. The protection capacity offered by the vegetation was assessed by considering two aspects, namely energy dissipation and reduction in the extent of inundation.

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