Department of Structural and Construction Engineering
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Item Alternative clay bricks inspired from termite mound biomimicry(Elsevier, 2022-06) Sanga, Reuben; Kilumile, Mernad; Mohamed, FatmaAs the world is witnessing vast pollution during material production, construction and demolition processes of buildings there is a need to seek for alternative materials that will reduce the environmental impact. The present study borrows inspirations from termite’s technique to create a material for constructing a naturally cemented mound structure. The studied termite mound was built from a mix of soil particles and termites saliva containing mucopolysaccharides and cellulase enzyme that digests cellulose into beta-glucose or shorter polysaccharides and oligosaccharides. These polysaccharides are found to be a source of soil stabilization and gluing property. In the process to mimic termites’ activities clay bricks were produced from a mix of clay soil and cassava flour in a form of hot cassava paste as a source of polysaccharides at 1.5%, 3%, 4.5% and 6% weight of soil. Brick samples created presented an optimal value at 1.5% cassava flour with compressive strength higher than that of burnt clay bricks at 4.28 MPa.Item Analyses of Deteriorating Old Masonry Buildings; Characterisation of Materials for Establishment of their Compatible Repairs(2015) Makunza, John K.; Kumaran, Senthil G.Most of the Governmental and religious building structures in Rungwe district are masonry structures built during the German East Africa period. These structures are deteriorating despite of various efforts on their repair intervention using modern cements and paints. This paper studies the types of mineral binders used, composition and physical characteristics of these in-situ mortar materials for the purpose of deciding on their appropriate compatible repair materials. Field observations and investigations, laboratory materials testing and review of the literature showed that the in-situ mortar materials constituted of sub-hydraulic lime mineral binders to natural sand (1:3) mortars. Currently there are no producers of hydraulic lime in Africa and a limited production worldwide. Mix design and analysis of locally available hydrated lime plus pozzolana natural sand (1:3) mortar material have shown compatibility in chemical and major physical properties and characteristics with the substrate in-situ hardened sub-hydraulic masonry mortars. Therefore use of these repair mortars is recommended for compatible repairs to these masonry structures and as a regional alternative to cement based materials for low rise masonry structures.Item Analysis of Factors Affecting Pavement Markings and Pavement Marking Retroreflectivity in Tennessee Highways(University of Tennessee at Chattanooga, 2015) Malyuta, Daniel A.Pavement markings are lines drawn on a pavement surface to provide vital information to road users pertaining to lane restrictions and vehicle movements, which if adhered to, results in improved safety and smooth travelling to road users. Pavement markings’ visibility is quantified into a parameter called retroreflectivity, which is a measure of how well the markings can be seen by road users. The importance of the factors affecting pavement markings differs from one publication to another, which cause the effective management of pavement markings a difficult process. In addressing this concern, this thesis investigated factors affecting pavement markings and marking retroreflectivity in Tennessee highways using retroreflectivity data collected on asphalt highways. Quantifiable factors affecting pavement markings retroreflectivity are analyzed, and linear degradation models are developed using regression analysis. The analysis shows that age and traffic have significant impacts on pavement marking retroreflectivity degradation.Item Application of Non-Destructive Testing in Evaluating Reinforced Concrete Structural Elements in Buildings(2008) Rubaratuka, Ignas A.; Ndumbaro, P.Of recent a large nllmber of existing rei"forced concrete bllildings have reqllired reconstruction, renovation and improvement. This tendency poses a "w"ber of problellls that have to be solved, the main aile being to determine the actual strength condition of the structural components/elements of the bllilding. It includes determ inatioll of the quality of materials used, specificatiol/ orthe types (/I/d description of apparent fa II Its and damages and extent of wear of the bllilding. To undertake this evaluation, non - destructive testing methods are IIsed. In this paper, applications of lion - destructive testing methods to determine the strength state of reinforced concrete colllll1ns with corbels and to establish their structural strength so as to deterl7line the capacity of a mobile crane to be installed is olltlined.Item Assessment of Strength Compliance with Standards for Tanzania Eucalyptus Wood Poles Treated with Copper-Chromium-Arsenic Compounds(2007-07) Mrema, Alex L.Samples of copper-chromium arsenic compounds (CCA) treated Eucalyptus poles for power transmission were sampled from a lot following Militmy Standard MlL-STD 105D, Single sampling, Tightened Inspection, Acceptable Quality Level (A QL) of 4 as provided for in the South African Standard SABS 754: 1994 from lots containing 151-500 poles. Samples were randomly selected from a lot. Maximum fiber stresses were evaluated taking into account the actual taper in each pole. The cantilever loading test was peiformed on the samples following SABS 754:1994. It was found out that the average taper for the poles was smaller than that assumed in the standard due to the dijJerent pole growth characteristics and environment in Tanzania and that the average modulus of elasticity obtained for the poles was lower than the average assumed in SABS 754: 1994. The poles also showed excessive deflections at working loads. It is recommended to the Tanzania Bureau of Standards that although SABS 754: 1994 ;s meant to be used for eucalyptus poles grown ill Southern Africa south of the Sahara that are treated with creosote or CCA there is a need to review it to take into aCCOl/nt the actual characteristics of the poles grown in Tanzania where they are normally grown in highland areas with higher rainfall and colder climates.Item Assessment of the Accuracy of Approximate Methods in the Analysis of Plane Frame Structures(2004) Rubaratuka, Ignas A.Item Behavior of Wood in Transverse Compression(1994) Pellicane, P. J.; Bodig, Jozsef; Mrema, Alex L.A finite element analysis program exists to evaluate the stress distribution in wood members subjected to perpendicular-to-grain (transverse) compression. In this study, the program was used to perform parameter studies to evaluate the effects of key variables on the distribution of stresses and the maximum stress concentrations in wood subjected to transverse compression. These variables included: specimen geometry (length/depth), loading geometry (loaded length/specimen length), and material properties (ratio of moduli of elasticity of the wood in the direction of loading/perpendicular to loading). The results showed that a complex state of stress exists in members even when the load is distributed over the entire specimen surface. In particular, numerically-determined stresses nearly 3.5 times the nominal stress were found for certain combinations of input parameters. In addition, an empirically-derived equation is presented that estimates the magnitude of maximum stress concentration as a function of the three parameters investigated. The equation was developed with the use of multiple regression techniques and had a correlation coefficient of 0.958.Item Cement Bonded Wood Wool Boards from Podocarpus Spp. For Low Cost Housing(2006) Mrema, Alex L.This paper gives results of a preliminary study on the properties of cement bonded woodwool boards manufactured as composites by using wood wool (excelsior) from podocarpus spp. wood species and ordinary Portland cement. Two main parameters were varied during the investigation and these were the width of the wood wool and the cement to wood wool ratio. Results show that the optimum mix proportion is three parts of cement to two parts of wood wool by weight and that a smaller excelsior width gives higher board strengths. The results from tests on flexural strength, compressive strength and tensile strength far exceeded the requirements of the German Standard DIN 1101:1989. Results of water absorption and swelling were, however, higher than those specified in the standard but this was attributed to insufficient pressure on the boards during manufacture an anomaly which can be corrected. The potential uses of the boards are in basements, floor units, permanent shuttering, partitioning, sound insulation in walls, ceilings and floors, roofs, sound barriers and thermal insulation. Further research is required to investigate the use of different wood species and different mineral binders.Item Challenges of the Quality of Reinforced Concrete Buildings In Dar es Salaam(International Journal of Engineering Research & Technology, 2013-12-13) Rubaratuka, Ignas A.In Dar es Salaam, most of the buildings are constructed using reinforced concrete due to non ? availability of other durable materials and the strength and protection concrete provide against aggressive weather conditions. Despite of these advantages, still reinforced concrete constructed buildings in Dar es Salaam are facing quality problems which are mainly caused by lack of national building codes and standards, design deficiencies such as lack of design details and accuracy, unsatisfactory quality of concrete ingredients, inappropriate construction technology, lack of quality control measures and inadequate supervision on construction sites.Item Comparison of the Properties of Portland Cement and Portland Limestone Cement(2010) Mrema, Alex L.A study was made in one of the cement factories in Dar es Salaam, Tanzania, where Ordinary Portland Ce-ment (CEM I 42.5N) and Portland limestone cement (PLC) (CEM II/A-L/32.5R) are produced and conform-ing to the Tanzania Standard TZS 727 (Part1): 2002, which is equivalent to EN 197 published by the com-mittee for European normalization (CEN). A comparison was made between the two types of cements in terms of physical, chemical and mechanical properties. It was found out that they all complied with the standards, that there was no significant difference in their setting times and that the Portland cement had higher strengths than the PLC. Also it was observed that there was a slightly lower water demand for the same consistency when compared to OPC and hence there is an improvement of the cohesiveness of a con-crete mix when PLC is used. It was concluded, however, that the two cements are different and that using the two cements interchangeably as is done in Tanzania is wrong because they do not have equivalent strengths and therefore equivalent performance since the PLC is not optimized.Item Corrosion Control of Steel Reinforcement in Reinforced Concrete Buildings: a Case Study in Dar es Salaam(2011) Rubaratuka, Ignas A.Item Defects in Reinforced Concrete due to Environmental Conditions and Concrete Treatment: a Case Study at the University of Dar es Salaam(1999) Rubaratuka, Ignas A.; Mulungu, D.Item Design Considerations for Blast Resistant Commercial/Civilian Buildings(2009) Rubaratuka, Ignas A.Item Dynamic Analysis of Forced Non-linear Oscillations in Mechanical Systems(1997) Rubaratuka, Ignas A.Item Dynamic Stability of Forced Non-linear Oscillations in Mechanical Systems(1999) Rubaratuka, Ignas A.Item Earth Building in Tanzania – Use of Soil Stabilized Bricks and Blocks(2005-06) Mrema, Alex L.This paper presents experimental results of investigations done on the use of stabilized earth (soil) for the manufacture of bricks and blocks. The soil used was clayey sand of low plasticity. Two types of stabilizers were used to make stabilized bricks and these were cement and a combination of cement and lime. Different stabilizer proportions were employed. Results of tests carried on these bricks at 28 days indicate an optimum mix proportion of 7% cement if cement is used alone and an optimum mix proportion of 5% each if a combination of lime and cement is used as a stabilizer. With these stabilizer contents we obtain bricks of strengths of at least 2.5N/mm2 with acceptable functional capabilities in a wall for low cost housing. To make bricks comparable in strength with those made of cement and sand with a minimum strength of at least 3.5N/mm2 for load bearing walls as suggested in the Tanzania Standard, TZS 283:1986, the optimum mix proportion was found to be 8.5% cement and 7% each if cement and lime is used in combination. It is suggested that further research on the effectiveness of the various other stabilizers like bitumen, gypsum, ash/sand, and cow dung is required for the different types of soils commonly found in Tanzania.Item Feasibility of Lightweight Aggregate Concrete for Structural and Non-Structural Works in Tanzania(2013-09) Mrema, Alex L.There has been serious land degradation in Tanzania due to extensive exploitation of granite aggregates even in areas where there is plenty of natural lightweight aggregates. Many Engineers have resorted to using normal weight aggregates in construction not only due to the feeling that lightweight aggregates (LWA) are too weak for structural purposes but mainly due to lack of knowledge of the design procedures for lightweight aggregate concrete (LWAC). Structures made of normal weight aggregates have higher dead loads which demand reduced span lengths, deeper structural members, more reinforcement and increased foundation area when compared to those made of LWAC. In Tanzania there are major deposits of LWA in areas of previous volcanic eruptions namely Kilimanjaro, Mbeya and Arusha and these remain largely un-exploited. Research was done to investigate the feasibility of using scoria and pumice aggregates in structural lightweight concrete. The aggregates were obtained from Kilimanjaro and Mbeya respectively. A mix design for grade 20 concrete was performed for both aggregates. It was found out that it was possible to use the scoria aggregates for structural concrete but not the pumice without mineral additives or chemical admixtures. Using pumice aggregates without any additives, the strengths obtained were less than 17 MPa which is the minimum strength acceptable for structural LWAC. It was concluded that the use of scoria aggregates for structural LWAC was feasible and that the pumice aggregates could be used for non-structural LWAC. Further research is required to find alternative deposits of pumice with better strengths for use in structural LWAC as the strengths of these aggregates vary from place to place and even within the same locality. Structural and Construction Engineers in Tanzania are now in a position to design and use LWAC as the design procedures have now been elaborated. The use of light weight aggregates especially in areas where these deposits are present will reduce the current costs of transport of normal weight aggregates from long distances and this will also protect the environment.Item Item Importance of Planned Maintenance Systems for Buildings(1997) Rubaratuka, Ignas A.Item Importance of sPStructural Fire Protection in Reinforced Concrete Buildings: A Case Study of Ex- NASACO Building(2004) Rubaratuka, Ignas A.