Master of Engineering in Structural Engineering Design

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item: Thesis-Abstract
Comparative study on code based analysis of steel moment resisting connections
(2015-02-22) Kodikara, KANT; Baskaran, K
Moment resisting connections are usually designed as simple or continuous although the actual behavior is known to fall between these two extreme cases. The use of semi- continuous connection results substantial savings in steel weight of the overall construction. Extended endplate and Flush end plate connections are the widely used type of connections in steel frame construction. To understand the real behavior of semi- continuous connection, full scale laboratory test is the most accurate approach, but it is time consuming and costly to undertake. Therefore other methods were developed to predict the capacity of connections. Thus, in this study three EEP and three FEP connections were analyzed using two standards (BS 5950 Part 1: 2000 and EC 3– with UK national application document). A method proposed by Steel Construction Institute (SCI) was taken into account for analyzing. The results obtained from the numerical analysis were then compared with the existing experimental test results on the resistance of moment and mode of failure to determine the accuracy of numerical analysis. Comparison between the results from numerical analysis and experiment results satisfactorily agreed.
item: Thesis-Abstract
Computerized optimization of the base width of transmission towers in Sri Lanka
(2015-02-22) Ganeshwaran, R; Hettiarachchi, MTP; Baskaran, K
Transmission line towers were mainly used in electrification works in all over the world. Optimization of base width of the transmission towers becomes necessary in order to reduce the cost and to avoid public objection. The use of narrow width tower becomes essential, as the land value appreciates drastically in Sri Lanka. This research is to design the transmission towers with reduced base width to minimize the coverage land with optimum weight and adequate strength. There were number of models selected with 14.2m base width and analyzed by reducing the width in steps from 1m to 3.2m. For this purpose computerized model analysis software named PLS Tower was used. Accordingly cost analysis was carried out for different steel prices and the cost of land. As per this study Optimum base width of 6.2m was found considering both the land & steel price. When compared with the towers used in Sri Lanka, it was found that the narrow width towers designed from this study showed a considerable amount of saving in cost and favourable impact on environmental issues.
item: Thesis-Full-text
Cost comparison between conventional and flat slab structures
Hewavitharana, N; Baskaran, K
In present era,conventional Reinforced Concrete(RC) frame buildings are commonly used for the construction. The use of flat slab building provides many advantages over conventional RC frame building in terms of architectural flexibility,use of space,easier form work and shorter construction time. In the present work conventional and flat slab four story buildings are considered for cost comparison. In this research flat slab building andnormal symmetric RCframe buildings of different spans have been studied. The cost of construction for these buildings has also been compared. To find out the cost of reinforcement, formwork, concrete on structural elements slab,beam,columns are considered.For modeling and analysis of conventional and flat slabstructures,SAP 2000 software is used.The dead loads, live loads are considered as per British Standard. The investigation shows that weight of flat slab structure is less compared to conventional slab structure. The cost of flat slab structure is less by around 12%-16% as compared to conventional slab. This study concludes that flat slab structures are the best suited for high rise buildings as compared to conventional slab structures,in terms of costof material.
item: Thesis-Full-text
Design bending moment in concrete box structures : a comparative analysis between shell and soild element models
Rasikamal, AADI; Baskaran, K
Concrete box structures are mainly used in railway and highway projects as culverts or frame bridges. Structural engineers prefer to do finite element method (FEM) analysis using shell or frame element models to obtain bending moment diagram (BMD) for design. Structures are modelled center to center supports in shell element models. BMD of general shell element models are continuous throughout the center to center spans and maximum support moment occurs at center of supports. ACI design practice recommends selecting bending moment at face of the support as design value, but BS design practice is different and obtains bending moment value at center of the support for designs. Some literature suggests tedious bending moment correction according to the stiffness of the members of the joint. In general shell element modeling, inside rigidity of supports is not considered. However general shell element models can be modified at support region to represent the rigidity of the support area. Previously tested concrete box structure was modelled using general shell, modified shell and solid elements. Results of solid element model are much closer to experimental results at supports and spans than other models. This result validated that solid element of box culvert can be used as a base for comparison of general and modified shell models. In this study, BMD of general shell, modified shell and solid element models relevant to concrete box structures were compared to load combinations relevant to Sri Lankan Railways. The results show that BMD of solid and modified shell elements are much more similar than the general shell models. Support design bending moment can be obtained from modified shell models with reliability without confusion of center or face value to select for the design as for the general shell element models.
item: Thesis-Abstract
Design/strengthening of reinforced concrete pier heads
Wickramasinghe, WR; Baskaran, K
In a developing country like Sri Lanka, it is very important to develop infrastructure to facilitate investments. In this context special emphasis should be given to the road development sector. Therefore highway projects playa major role in infrastructure development. Southern Transport Development Project is a major ongoing highway project in Sri Lanka. Package 2 of that project having 22 highway bridges and five of them are multi span structures. The intermediate supports of those structures are hammerhead piers which are having pier heads in the range of 4-5m cantilever lengths. After erection of post tensioned girders the deck slab and the diaphragms were cast in stages to make the deck slab continuous over the piers. During construction cracks of significant widths were appeared at both ends of the pier heads. In investigating the causes for cracking it was found that, 75% of main reinforcement and 65% of shear links were curtailed in the pier head over the stem area by the designer according to the instructions of the Engineer of the project. Therefore this research focuses on the curtailment of main reinforcement and shear links of a hammerhead pier. Further, the other aspect of this study is to discuss different strengthening solutions which can be applicable to this type of under-reinforced hammerhead pier. In this regard, different cantilever lengths of three dimensional hammerhead pier models were analysed with shell elements in two different orientations using the structural analysis package SAP2000. The reinforcement and shear link requirement of the pier cross head over the stem-area was calculated and the percentage of curtailment possible is presented in this report. Finally, different solutions for strengthening a hammerhead pier are-also discussed.
item: Thesis-Abstract
Economical falsework solutions for concrete arch bridges
(2014-05-20) Jayakody, JAVS; Baskaran, K
The arch bridge is very strong. It looks like half a circle. Arch bridges used to be made of stone. The problem was that until the last block was in place, these bridges were unstable and could fall down. Construction field in Sri Lanka has lot of arch shape structures such as Buddhist Temples, Muslim mosque etc therefore aesthetic view of arch shape bridges are better than other shapes. Traditionally, arch bridges were constructed of stone, brick or mass concrete since these materials are very strong in compression and the arch could be configured so that tensile stresses did not develop. Contractors are not motivated to construct arch bridges due to difficulties of construction. If there is a simple method to construct an arch bridge it is economical and quick because of flow of the stream or flood will not be disturbed to the construction. Heavy machineries or advanced technology does not matter and local labour force can be utilized. In the locations which are inaccessible to transport material or heavy machineries, concrete arch is a solution with a suitable falsework. Most bridges in Sri Lanka are constructed over water ways therefore during the construction period finding a supporting base to construct an arch structure is very hard. Also river beds are located far below from the deck level of bridge and erection of stable falsework support will be another difficult task. These are the problems in arch bridge construction within the available technology of construction in Sri Lanka and tend to existing arch bridges are limited to short spans. The objective of this research was to obtaining an economical solution for this problem. In point form the scope of this research includes • find the possible methods to construct concrete arch bridges. • materials have to be used for falsework for construction of concrete Arch Bridges. • Types of Trusses possible to use as falsework. At the design stage of concrete arch bridge, suitable falsework truss also should be designed to get the support to construct the bridge. Similar to benefit of scaffoldings to building construction, falsework truss also will be benefited to arch bridge construction. It will facilitate to select different models of falsework truss for construction of various types of concrete arch bridges with higher spans or different curvatures. Steel trusses design for falsework is ideal solution because mainly simplicity of its erection process. Another option is a timber falsework for the construction of concrete arch bridge. Cost of the timber falsework is obviously high where the locations of long span of arch bridges or high level difference between river and deck of bridge. Within the Types of steel trusses economical one also has to be identified because of their cost of material and cost of fabrication. The types of steel trusses commonly used are Howe truss, Modified Howe truss, Pratt Truss or Warren Truss. Structural analysis computer software SAP 2000 was used to analyse trusses to achieve the objectives of the research. Based on the analysis of this research Modified Howe truss fabricated by steel angle iron is successful as economical falsework solution to the construction of concrete arch bridges in Sri Lanka.
item: Thesis-Full-text
Evaluation of seismic capacity of existing highway bridges in Sri Lanka
Aluthapala, UL; Lewangamage, CS; Baskaran, K
Sri Lanka is an island located in the Indian Ocean and it lies in the large Indo-Australian plate seemingly far away from any of the plate boundaries. Therefore, many people believe that this fortuitous scenario makes Sri Lanka safe from earthquakes. But an intra-plate earthquake can occur anywhere at any time. Some geologists pointed out that the Indo Australian plate is being separated into two and its boundary lies 500km away from the southern coast of the country. Therefore, Sri Lanka has a moderate risk to face an earthquake. There are over 4000 bridges on National Road Network with length varying from 3.0m to 500.0m. These bridges have varying widths about 3.0m to 25.0m and some of these have been constructed more than 50 to 100 years back. They were constructed using steel concrete composite or steel. These bridges have not been designed for seismic loads and they have not been detailed for seismic effects. Therefore, it is a must to evaluate the seismic capacity of those bridges and retrofit those if necessary. This study was focused to develop a priority list (Bridge Rank) for the purpose of further investigation on seismic capacity. It was also focused to carry out a case study for a selected bridge from the developed priority list to find out its seismic capacity. Bridges on the “A” class roads with the overall length of the bridge is greater than 25m were considered in this study. To develop the priority list for thesebridges, the method given in the “Seismic Retrofitting Manual for Highway Bridges” published by the Federal Highway Administration (Report No. FHWARD- 94-052) was used. The parameters required to input to the above methodology were obtained from the previous research findings and the bridge inventory that is maintained by the Planning Division of RDA, Sri Lanka. The bridges considered under this study have low risk to fail due to possible earthquake loadings with local conditions since the bridge rank is between 0 to 24 on the scale of 100. Bridge No 1/1 on PeliyagodaPuttalam road (Japanese Friendship Bridge) was selected for further investigation from the developed priority list since it gives the bridge ranking 12. A response spectrum analysis was carried out to find the actions of the bridge during an earthquake. For the analysis of the bridge, a Finite Element Model was developed using SAP 2000. Codes of practices for Australian standards were used to find out the seismic capacities of the substructure and the actions of superstructure was compared with the originally designed actions. The bridges considered under this study have low risk to fail due to possible earthquake loadings since the bridge rank is between 0 to 24 on the scale of 100. It is proposed to replace the bridge bearings of the bridge no 1/1 on PeliyagodaPuttalam road based on the results of the case study.
item: Thesis-Full-text
Feasibility study on polyurathene sandwich panel for domestic construction
Fernando, WB; Baskaran, K
The place to live is the third need of mankind. Everybody try to build up a suitable mean to meet their own requirements. The Sri Lankan need always changes drastically after two decades from initial construction as the social and economical changes in the society. The use of none renewable material for short period may degrade the scarce resources. And also generate ample amount of green house gasses, which lead the global warming. Therefore in time to come, we have to switch to renewable material or reusing material. There are some materials, those are produced from garbage. This creates regenerative products on earth resource extraction circle. The polyurethane sandwich panel is a reusing material which is produced from garbage. This thesis is on feasibility study on polyurethane sandwich panel for domestic constructions. The product establishment is a derivation as a regenerative product to meet the human need of this scenario. Additionally there is a shortage of skilled labour in the country. And the cost of labour for domestic construction is a considerable portion. The time consumed for domestic construction is more than months. Therefore by introduction of polyurethane sandwich panels for domestic constructions may resolve the major problems in the domestic construction field in the country. The aim of this thesis is to introduce an engineered solution from polyurethane sandwich panel to aforesaid problems. The only drawback is the less fire rating. But currently produced materials meet the legislative and regulatory stipulations. The science and technology on this field is to be improved in time to come. The sandwich panels are having very high stiffness compared to weight and a cost effective product. Polyurethane sandwich panel material may last more than two decades without much maintenance. The polyurethane sandwich panels are used for the construction of walls and ceiling on the cold room constructions as a good thermal barrier. This thesis is to see the validity on cold room construction material for the domestic constructions. The material properties changes from supplier to supplier. Therefore it is very difficult to adopt the standard practice in design. Even though “European Recommendations for Sandwich Panels Part 1; Design”;[14] has released on year 2000. The publication has been criticized by various researches such as Narayan Pokharel and Mahen Mahendran on their publication to “Thin Walled Structures” [13]. In addition the both published documents’ equation ranges on “European Recommendations for Sandwich Panels Part 1; Design” [14] and “Thin Walled Structures” [13] do not comply with the encountered polyurethane insulative sandwich panel. Therefore the serviceability limit published by “European Recommendations for Sandwich Panels Part 1; Design” [14] has been incorporated for design serviceability limit checking. This thesis is on feasibility study of sandwich material for house constructions by means of walls, slabs and roofs. The typical two-story house and the two story cluster houses are modelled to see the engineering viability under standard loadings. The outcome revealed that the construction up to two stories is safe. Therefore further studies in this stream shall be followed in future. As per the project outcome on the clause 6.6; it reveals that the domestic constructions up to two stories may be possible under some form of local capacity enhancement methods adapted to high stresses applied locations. The economical analysis is also made in Chapter five. Accordingly the cost on individual houses and cluster houses do not change and it revealed that there is more than 41% saving compared to the conventional constructions.
item: Thesis-Full-text
Investigation of structural defects in government hospital buildings in Sri Lanka
Dilrukshi, ALA; Baskaran, K
Sri Lanka has a free of charge health care system heavily subsidized by the government. The national health system of Sri Lanka is guided by the concept ofthe welfare state. The major armed conflict, which started in 1983 came to an end in May 2009 affecting almost all the sectors in the whole country. At present, Sri Lanka aspires to become a higher middle income country. It faces the challenge of becoming a high performer in all sectors affected. Social health protection is hailed to be placed high on the national agenda. Within this context safety of built environment ofthe government hospital sector too is one ofthe most important matter and the upgrading ofaesthetic aspect ofthe built environment is also a long await need. A government hospital complex is a main component ofmajor cities all over the country. But the common perception of government hospitals is attributed to the unpleasant experience due to the poor condition of built environment rather than the valuable and highly committed service being provided free of charge to the society. This particular study was conducted to investigate structural defects in Government Hospital Buildings (GHBs). Government Hospitals in Western province were selected for visual observation and photographic survey based on convenience and by judgement ofthe fact that over utilization of hospitals in Western province. Also, it was highly important being aware ofthe local and international picture referring to past studies regarding the same area ofstudy. As the chiefstructural material ofmost ofthe GHBs is Reinforced Concrete (RC), attention was drawn to refer to cracking inherent to RC as well. Observations and information gathered were carefully reviewed. Direct and indirect causes of defects could be identified based on the historical data and the observations made. Further the attention was drawn on the current practice of Designing ofHospital Buildings in Sri Lanka and an attempt was made to find whether structural and performance issues identified and the maintainability aspect are addressed at the initial design stage. It was revealed that there is neither detailed registry ofGHBs nor detailed building audit ofdefects being earned out. The main reason for immerging poor quality building either by new construction or renovation work is the lack ofsupervision ofthe work by competent personnel. The Attention on setting up a well-structured Building Management Division which is entrusted clearly with the entire responsibility regarding the GHBs is identified as a necessity in upgrading the condition ofGHBs. A special attention on performance and maintainability aspect ofGHBs at the initial design stage has hardly been paid rather than adopting the common practice of designing of all' types of buildings. Despite the constraints in vertically expanding, the government hospital buildings observed are at an acceptable structural condition thus not requiring complete demolition.
item: Thesis-Abstract
Production of self compacting concrete using rice husk ash
(2014-08-22) Jeevasangar, S; Baskaran, K
Self compacting concrete flows into formwork and around obstructions under its own weight to fill it completely and self compact (without any need for vibration), without any segregation and blocking. The elimination of the need for compaction leads to better quality concrete and substantial improvement of working conditions. The current study revolves around self compacting concrete made out of locally available material. The objectives of this research were obtaining proper mix designs for grade 50 concrete using rice husk ash and evaluating the fresh and the hardened concrete properties of the mix designs. In the first stage, ten different self compacting concrete mix compositions were made by using ten percentage of rice husk ash with respect to total weight of cement and obtained mix designs to satisfy the consistency, workability, passing and filling ability. In the second stage, harden concrete properties were evaluated for the particular mix design. In this dissertation, experimental details of several trial mixes and attempts taken to satisfy the fresh concrete properties for grade-50 self compacting concrete are presented. The attempts taken to investigate the hardened concrete properties have shown for one trial mix. Cost analysis showed that the cost of ingredients of SCC-02 self compacting concrete mix with rice husk ash is 22.70% more than the SCC-00 self compacting concrete mix with fly ash.
item: Thesis-Abstract
Strength assessment of axially loaded RC column strengthened by steel cages
(2015-09-17) Thenuwara, TATE; Baskaran, K
In reinforced concrete buildings the columns are the main vertical elements, which sustain and carry the entire weight. Hence they should be capable to withstand the loads transferring from the beams and slabs without any failure. Any deficiency of the column may cause total collapse of the structure and it may lead to destruction of human life and also physical damages to other structures. But due to reasons such as change in use, design, number of floors, addition of other installations or deterioration, it is often necessary to strengthen RC columns in buildings during construction or post construction. Three main methods; concrete jacketing, steel jacketing and composite jacketing are used to strengthen RC columns. Concrete jacketing is popular in Sri Lanka but it is worth to implement steel jacketing in the construction industry due to the easiness of the usage. The composite jacketing cannot be implemented due to high cost. Hence the aim of the present study is to encourage the use of steel jacketing in Sri Lanka. To have economical use of steel, angles and strips can be used to strengthened RC columns. The objective of the present study is to check whether EUROCODE 4 (2004) or BS 5400-5 (1979) can be used to evaluate the load carrying capacity in compression for RC columns strengthened with steel angles and strips. The experimental results from foreign and local researches were gathered and compared with the calculated theoretical values. The ratio between gross capacity without safety factor and experimental value is ranging 0.95 to 1.05 based on EC4 and 0.96 to 1.06 based on BS 5400 5 in the experiment II of Ester G with five strips and it is 0.84 based on EC4 and 0.85 based on BS 5400 5 in the experiment I of Ester G. with seven strips. But, for the experiment of Kumaranjan A. the ratio between gross capacity without safety factor and experimental value is ranging 0.97 to 1.03 for seven and five strips. The ratios between theoretical ultimate values of BS 5400 5 and EC4 are varying from 0.87 to 0.88 in experiment done by Ester G. and 0.84 in the experiment done by Kumaranjan A. The experimental values are higher than the theoretical ultimate values and the safety factor of 1.1 to 1.6 is for EC 4 and 1.36 to 1.85 is for BS 5400 5. It is confirmed that the safety factor of the both codes have sufficient provisions for the capacity of strengthen RC columns using steel cages. Also, when using seven strips the capacity has increased but it is not quantified using the codes calculations. It is recommended to test the real size columns with several L angles sizes with load on it while strengthening to simulate a constructed column in a building. Also, an experimental study by varying the number of strips connected to the cage would lead to identify the limits of the enhancement of strength capacity.
item: Thesis-Abstract
Strength assessment of reinforced concrete structures under effect of corrosion
(2014-08-14) Kurumbalapitiya, KASL; Baskaran, K
Main types of reinforced concrete structures such as buildings, bridges, transmission poles which were built specially in the last century, are reaching end of their life span and need strength assessment for their continuous safe use. Strength assessment has to be done as the capacity requirements of a structure can change with changes in technology and life style, change in use, deterioration of structures due to corrosion of reinforcement, chemical attack, thermal effects, shrinkage effects, construction tolerances etc. The easy but expensive solution for the older building is to replace existing building with a new one but this is very uneconomical. The alternate and practicable solution is the assessment of load carrying capacity and then strengthening of the structure. One of the major causes that would lead to deterioration of reinforced concrete structures is the corrosion of reinforcement. Damage to the concrete structures occurs in the form of cover cracking, reduction in rebar cross-section, deterioration of bond between reinforcement and concrete. Premature failure of reinforced concrete structures can therefore be prevented by proper control and monitoring of reinforcement corrosion. The assessment of structural behavior of corrosion affected structures would help in making certain decisions pertaining to the inspection, repair, Strengthening, replacement and demolition of such structures. Corrosion of reinforcing steel and subsequent concrete deterioration is a major problem Faced by the construction industry. Different methods have been utilized to study the response of corroded reinforced concrete. Tests have been widely used as a means to analyze individual elements and the effects of corrosion on concrete strength under loading while this is a method that produces real life response, it is extremely time consuming, and the use of materials can be quite costly. The use of finite element analysis to study these components has been used in recent years. However, limited work is available for the estimation of the flexural strength of corrosion-damaged members. ANSYS is used to perform the non linear finite element analysis in this research and is a general purpose finite element modeling package for numerically solving a wide variety of mechanical problems. These problems include static/ dynamic, structural analysis (both linear and nonlinear), heat transfer, and fluid problems, as well as acoustic and electromagnetic problems. The objectives of the research study are to study non-corroded and corroded reinforced concrete beams using finite element analysis to understand the response of non corroded and corroded reinforced concrete beams and to develop computer models to predict the behavior of the corroded reinforced concrete beam to examine the structural behavior of non-corroded and corroded reinforced concrete beams and to establish a methodology for applying computer modeling to non-corroded and corroded reinforced concrete beams. This research is carried out for two case studies. Finite element models were developed to simulate the behavior of beams from linear through nonlinear response and up to failure, using the ANSYS 11. SOLID 65, LINK 8 element represent concrete and discrete reinforcing steel bars respectively, based on each component actual characteristics, non linear material properties are defined for both elements. Comparisons were made for load-deflection curves at mid span and crack patterns at failure. Conclusions from the current research efforts are included. It is concluded that the finite element analyses could be used to realistically predict the flexural behavior of non-corroded reinforced concrete and corroded reinforced concrete beams.
item: Thesis-Full-text
Study improvements to the structural performances and cost optimization of existing telecommunication poles
Kumara, WAKB; Baskaran, K
Presently SLT invests huge capital on production of RCC poles to draw various types of telecommunication cables and hence explores the possibilities of minimizing the investment on production of RCC poles by introducing economized pole design or modifying the existing RCC poles with less production cost. There are numerous problems associated with conventional telecommunication posts currently being used in practice such as prone to corrosion in coastal belt areas. Much difficult to maintain uniform quality throughout the pole length due to manual practices of concrete mixing, bar bending, formwork etc., this will further aggravate due to lack of skilled personals for operation. In such a situation life span of the final products are doubtful. Manufacturing processes are often been carried out by subcontracting labour groups so that they can produce maximum number of poles in very limited period to cater for the demand. At the same time they are trying their best to make maximum profit, result is sub standard products. Sri Lanka Telecom currently invest huge sum of money for the production of telecommunication posts in an yearly basis as demands are high, therefore Sri Lanka Telecom is compelled to invest additional amount to investigate and overcome the above problems in sought of producing good quality products with optimum cost. External forces encountered by the telecom poles are bending, axial forces, torsion forces or a combination of those three forces. These primary influences may be accompanied by shearing forces and sometimes by torsion. Effects due to changes in temperature, shrinkage, creep of the concrete, and the possibility of damage resulting from overloading, local damage, abrasion, vibration, chemical attack and similar causes may have also to be considered. An efficiently designed poles are one in which the weight, loads and forces are transmitted to the foundations by the economical means consistent with the intended use of the pole and the nature of the ground situation. The objective of this research work is to study on current designs and their pros and cons, applicable standards, manufacturing process and simulation of structural performance of poles under recommended loading criteria by modern analytical tools. At the initial stage of study variety of sections are analysed under applicable loading criteria to select most suitable one. Sections considered for analysis are square solid section with pre-stressed reinforcement, square hollow section with normal and prestressed reinforcement, circular section with normal and pre-stressed reinforcement, circular hollow section with normal and pre-stressed reinforcement. SAP2000 finite element programme was used to analyse the poles under different loading conditions as specified. Circular hollow section with pre-stressed reinforcements gave the best option and optimum results for the requirements with respect to structural performances, weight and cost. As a result of this research study, most economical solution has been recommended to overcome the above difficulties. Usual casting practices are revised to spun casting technique with pre-stressed reinforcements and high grade concrete. This will result in finding the superior structural performances, high quality, comparatively low cost and less weight product. Few samples of the new designs are cast and been tested to witness their structural behaviours under the laboratory conditions. Finally the current and proposed designs are compared to demonstrate the weight reduction. Structural details and specifications for new designs are prepared under different height category of poles to suit manufacturing facilities.
item: Thesis-Full-text
Study on behavior of concrete fins against blast pressure
Prasad, RMB; Baskaran, K
Designing structures against blast loading is becoming more and more important as the number of terrorists attacks are increasing day by day. It is necessary to protect the structures against a credible blast load to ensure the safety of the occupants. In this context, blast resisting facades are incorporated in buildings to avoid the blast pressure waves entering into the building as the highest damage is done by the pressure waves when compared with the fragments moved by an explosion. Pressure waves could damage the axially loaded elements and it may lead to progressive collapse of the structure. This study investigated the behaviour of concrete fins and they were categorized depending on the failure mode which is based on the occupancy levels such as immediate occupancy, life safety and collapse prevention. Concrete fins were analysed using Sap2000 software by taking into account the material nonlinearity and loading nonlinearity. Weight of blasting materials, standoff distance, fin spacing, fin size and reinforcement ratios were varied to create different analysis cases. When the standoff distance was 50m, all the analysis cases were in immediate occupancy level, and it was found that standoff distance of 25m is as the manageable distance in blast. However, standoff distance of 10m resulted many analysis cases exceeded the collapse prevention limit. It was identified that standoff distance of 25m as the manageable limit with respect to the safety and the cost.
item: Thesis-Full-text
Study on structural design of highway box structures
Chinthaka, SSLD; Baskaran, K
I would like to express my sincere gratitude to my research supervisor Dr.K.Baskaran, Senior Lecturer, Department of Civil Engineering, University of Moratuwa, Sri Lanka for his guidance, suggestions and continuous support throughout my M.Eng. research work. I am also much grateful to the Head of the Department of Civil Engineering, the Course Coordinator of Master of Structural Engineering, and the staff of the Department of Civil Engineering for their valuable guidance and cooperation given in many ways. I also extend my sincere gratitude towards my employer, Road Development Authority (RDA) for granting leave to follow this course and other assistances provided for my research works. I would like to take this opportunity to convey my sincere gratitude to Mr.L.V.S.Weerakoon (Project Director, Central Expressway Project, RDA), Dr.Ruwan (Head , Structural design office, Central Expressway Project, RDA),for the assistance extended to me in numerous ways throughout, and Dr.Naveed Anwar (AIT,Thailand/International Consultant for Central Expressway Structural design works ) for the guidance given in finite element modelling. Finally, I thank for all my colleagues and family members for the valued cooperation and encouragement received to complete my M. Eng. Program successfully.
item: Thesis-Abstract
Study on waterproofing methods of roof top slabs
(2015-09-17) Duleeka, KP; Baskaran, K
This research reports a study on waterproofing methods of roof top slabs in Sri Lanka. Waterproofing has become an essential component of a structure to protect its aesthetic appearance, prevent structural damages and for the safety of the occupants. Accordingly the type and the method of waterproofing required may vary with the location & exposure conditions. In the construction industry, many commercially available materials are used for waterproofing roof slabs. Under this research, field surveys were carried out to identify the types of waterproofing material, different methods of applications & quality controlling measures related 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 series was performed on commercially available waterproofing materials to check their suitability. For this both liquid applied waterproofing materials and admixture type waterproofing materials were used. Three specimens were prepared using each waterproofing materials. They were checked for water absorption under laboratory condition for 24 hrs. Two types of water absorption tests were done to study the effectiveness of the selected waterproofing materials. Furthermore specimens with integral admixtures were tested under compressive strength test to identify any increase in their compressive strength due to crystalline formation. Finally from the experiment it is concluded that liquid applied waterproofing systems perform better than the integral waterproofing systems. Among the used waterproofing materials, K11 flex waterproofing coating showed better performance than the other materials. And also compressive strength has been slightly increased of specimens with admixtures.

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