This study experimentally investigated the effect of connecting vertical plates and horizontal plates and their combinations to single and double pipes on scouring under pipes. Experiments were performed in a laboratory flume 13 m long, 0.4 6m wide, and 1 m deep. Results showed that attaching a 0.25D vertical plate under a single pipe prevented scouring under it. Further, in order to control scouring under pipes using a horizontal plate, regardless of the number of pipes and their distance from each other, the plate should extend 0.5D upstream and downstream of the pipes. A combination of horizontal and vertical plates under pipes showed that in cases where the length of the horizontal plate was not enough to prevent the formation and development of scour under the pipes, the addition of vertical plates on both sides of the horizontal plate can protect the pipes against scouring.
This paper presents the major causes of deterioration and discusses the factors, which can improve the durability of concrete structures. This paper also presents the results of an extensive experimental investigation for the reuse of industrial by product materials such as blast furnace slag (BFS) and silica fume (SF) in producing high performance concrete. Producing of high strength concrete has a worthy priority field of study worldwide, their production is largely expanded the last two decades. Potential applications of light weight high strength concrete are in producing thin durable sections and in strengthening and repairing defaulted structures. It is shown that it is possible to develop a concrete matrix of high strength and excellent durability by taking the advantage of the interactions of cementitious system and the Portland-cement slag system is shown to offer a good example of this nature. However, development of light weight strength and performance concrete will be necessary to protect the concrete from aggressive and unfriendly environmental and climatic conditions. Lightweight concrete can significantly reduce a dead load of structural concrete elements compared to normal-weight concrete. Self-curing concrete is one of the innovative concretes that can be cured without using conventional curing regimes. Lightweight concrete is made from lightweight coarse aggregates instead of natural coarse aggregates. It has gained popularity due to its lower density and superior thermal insulation properties. In this investigation, the durability of lightweight self-curing concrete under the attack of sulfates and chlorides was studied. The effects of sulfates (as 20% concentrated sodium sulfates solution) on compressive, splitting tensile and flexure strengths after different ages (2, 4, and 6 months) were studied. The effects of chloride attack (as 20% concentrated sodium chloride solution) were studied on bond and flexure strengths after two ages (2 and 4 months). Also, the flexure behavior of the lightweight aggregate self-curing reinforced concrete beams is studied under a four-point load system before and after chloride attack. Test results indicated that dolomite then crushed concrete followed by Addibor can be used as coarse aggregates for structural self-curing concrete under chlorides or sulfates Using lightweight aggregates (Addipor-55) or lightweight bricks as a replacement of dolomite can be used to produces lightweight self-curing concrete with satisfied durability characteristics under chlorides or sulfate attack.
In this paper, the author performed two centrifuge model tests at the University of Science and Technology of Hong Kong for two cases where the tunnel was located at cover over diameter (C/D) of 1.5 and 3.3 to investigate the passive failure and deformation mechanism due to tunneling in two-layer soils, sand and clay. The tests were carried out on a 1/100 scale miniature model. The experimental process simulated the progress of the tunnel face with a speed of 0.2mm/s (equivalent to 15m per day in practice), and displaced to 40mm then stopped. Linear variable differential transformers (LVDTs) are used to measure the ground transitions during the testing process. The particle image velocimetry (PIV) technology measures the movement of soil in front of the tunnel face. The loadcells attached to one end of the tunnel face in order to obtain the passive pressure exerted on the tunnel face. As the tunnel face displacement, the ground in front of the tunnel face is shifted forward, while the ground which is far from the surface of the tunnel is pushed outward, effected on the ground and thus causes the ground to emerge so form a breakout. The partial failure mechanism in front of the tunnel face is similar to localised cutting mechanism. When the observation failure mechanisms are idealized by continuous lines, the failure mechanism of ground in front of the tunnel face is shaped like a funnel.
Determination of the flow velocity and shear stress is fundamental for river restoration projects. There are few studies in estimation of these parameters in the presence of 3D pool and riffle which are dominant bed forms in coarse-bed Rivers. Considering the interaction of 3D bed forms and the flow characteristics in the presence of wall vegetation, the present study aims to determine the velocity distribution, shear velocity, and shear stress in a laboratory scale. Accordingly, the effects of sediment sizes and various discharges on velocity and shear stress distributions and the validity of logarithmic law were assessed in a straight laboratory flume 13 m long, 0.45 m wide, and 0.6 m deep. Experiments were conducted in 4 runs over 3D pool and riffle where the natural vegetation were used along one side of the flume wall. Results showed that the logarithmic law remains valid for relative depths Z/H= 0.36 and 0.84 where Z is distance from the bed and H is the flow depth, in different sections of 3D pool and riffle. The location of maximum velocity changed with increasing the flow discharge. The maximum velocity value occurred at higher relative depths in the pool section rather than in the riffle one. Higher flow velocity values were observed near the water surface in pool section and near the bed in riffle section, respectively. The investigation of shear stress revealed that the maximum and minimum shear stress values occurred in the pool and riffle flows, respectively, and the presence of vegetation led to a change in the location of maximum shear stress. When the median size of the bed particles decreased, less change was observed in the shear stress values.
The UK as a welfare state spends about 30% of the gross domestic product on social expenditures. The acute and biting shortage of housing, particularly social and affordable housing is responsible for the spiralling house prices and rents leading to an affordability crisis. Evidence-based research shows that the UK needs to build over 300,000 houses a year to meet the rising demand, particularly from young adults and families with low-to-middle incomes. As a result, there has been a worrying increase in overcrowding, homelessness, evictions and rent arrears. This research study aimed to investigate prefabrication, also known as modular construction as a solution to tackling the housing crisis in the UK. A mixed method approach was used to collect raw data. As such, five major construction firms were selected as the case study organisations for the research study. The respondents had a senior position in the organisations. The data collection methods that were adopted are qualitative (interviews) and quantitative (questionnaires). The data were analysed using thematic analysis in which emergent themes were identified throughout the interviews and the questionnaires. Findings suggested that the housing crisis is not about houses; instead, it is about individuals. Perceptions about prefabricated houses among the low, middle and high-income earners are largely negative whose implication is that individuals would rather wait to build traditional homes in the future than opt for a prefabricated home. Although traditional home ownership is slipping out of reach for the majority, the demand for prefabricated homes is still low. In urban areas, modular construction is practised on a small scale with the main market limitations being the small size of the domestic market and the existing building regulations which prohibit the use of inflammable materials in urban areas. Moreover, it was found that prefabricated homes may provide short-term and long-term solutions to the housing crisis since they address and resolve some of the most critical issues associated with traditional housing but not limited to high costs, longer construction periods and uncertain budgets.
In the past few years, the housing sector has witnessed an increase in the application of modern methods of construction (MMC) in the construction processes to address the existing housing shortage and improve the quality of buildings. However, despite the widely reported benefits of such methods, their uptake within the industry has been limited. This paper reports the findings made from a research that sought to investigate the effectiveness of MMC in terms of cost and time. A questionnaire survey was applied whereby five of the top construction companies in the country and 30 academicians it the field of construction were interviewed. The results obtained indicate that the current utilisation of MMC in the large and medium-sized housing companies is insufficient, but the level is expected to increase due to the growing pressure to improve on cost, time, quality, productivity, wastages, and health and safety of the workers. However, the perceived higher capital cost compared to the traditional method has been a major hindrance to the adoption of MMC. Despite this, as for a revolution in the construction industry of using modern construction methods, off-site MMC is not every company choice of construction form due to its higher capital and initial costs. This paper recommends a set of strategies that can be used to address the uncertainties surrounding the effectiveness of MMC and improve its usage among the construction companies.
The purpose of this study was to assess the significant factors contributing to the extension of time within the road construction sector in Ghana. A quantitative study was conducted within the road agencies in the Sunyani Metropolis namely; Ghana Highway Authority, Department of Urban Roads and the Department of Feeder Roads. A total number of sixty-two (62) questionnaires were administered to management professionals (quantity surveyors, contract managers and engineers) for this study. Relative Importance Index, the mean score and One-Sample test were used for analysing the data. Adverse weather conditions, changes to the original contract scope, and suspension of work revealed to be the most significant factors contributing to extension of time in road construction contracts in Ghana. The researchers recommend that there should be clear guidelines for extension of time known to all the major stakeholders of road construction projects in Ghana to contribute to the effective management of time claims within the road construction sector.
In this research, optimum design of reinforced cement concrete (RCC) ribbed slab, also known as waffle slab according to the Indian RCC code (IS 456:2000) is presented. The objective function is the combined cost of the reinforcement, concrete and formwork which sums up the cost of the ribbed slab. The structure is analyzed using the direct design method. The objective function is developed after studying the ribbed slab in detail. The optimization process is carried out for different grades of concrete. The comparative results for different grades of concrete are enumerated and laid out in the tabulated form. Optimization for reinforced cement concrete (RCC) ribbed slab is illustrated and the results of the optimum design and conventional design are compared. Optimization problem is a constrained nonlinear programming problem (NLPP). The mathematical model is analyzed by using MATHEMATICA software. From the analysis, it was found that savings up to 25 percent can be obtained by optimizing the reinforced concrete ribbed slab.
This research aimed to identify how road networks can be managed and maintained using geographic information systems to find the most cost-effective solutions. We produced a database containing road information and analysed the data to produce a model for road-maintenance management. Maintenance can improve the condition of roads and prolong their life. Therefore, a model need to be created and adopts specialized information about the condition of roads, which can then be used to determine the road maintenance process. A pavement-management maintenance system collects and monitors information on the current condition of roads, in addition to determining maintenance priorities. Such a system can also be designed to create a set of procedures aimed at maintaining asphalt roads with an appropriate level of service. In this research, a 35-kilometre stretch of governorate roads was used as the basis for the model. The aim of this study was to use geographic information systems (GISs) to create a database of the structural condition of roads and defects, capable of evaluating the need for maintenance work. A GIS database and PMMS model could be achieved by evaluating pavement-maintenance needs through performing an inventory and condition survey for roads and determining the most cost-effective actions for the roads based on their condition. The roads in question were found to require different types of maintenance, which were described according to the severity and extent of the asphalt pavement distress. About 30% of the agricultural road from Qena to Qift was found to be in need of maintenance action in the form of reconstruction.
Road condition is an enabler factor for both economic success and quality of life. In order to determine road condition, a model for pavement condition index is required. The condition index can be determined using roughness alone or by using both roughness and distress data. When roughness parameter is used alone, it may not predict well the condition of the entered network because in some cases, data for such parameter is missing during data collection. Also, measuring pavement condition index using roughness is quite complex because it depends on the vehicular characteristic and pavement situation. In addition, when key code is not properly configured, some data loss occurs, causing improper determination of condition index. The objective of this article is to improve estimation of pavement condition index using both IRI and distress parameters. A total of nine parameters were chosen including potholes, crack, rutting, patching, ravelling, overall condition, drainage, bleeding and shoulder condition. The weight score of each parameter was computed using mean value from statistical data collected from professional and experienced experts in pavement management. Nevertheless, the baseline data for modelling was obtained from Road Maintenances Management System database repository of Tanzania National Roads Agency. The result from roughness parameter for condition index was compared with those from both roughness and distress parameters. The sensitivity analysis of the parameters used in determination of road condition was also carried out where roughness was used as baseline indicator. The result of using roughness parameters in estimating pavement condition shows that 67.86% of the paved network was good, 13.12% was fair and 0.23% was poor while. On the other hand, combined parameters were used, the analysis showed that 92.38% was good, 7.38% was fair and 0.24% was poor. The higher difference was noted in trunk paved roads which was about 24.52%. It is concluded that estimation of Pavement Condition Index using combined parameters is very reliable and yields correct results compared to those using single parameter. Also, it is noted that sensitivity of roughness, patching, wide crack, ravelling, rutting in determining the road condition index are almost the same. However, bleeding and potholes have higher sensitivity than others.
Chloride induced reinforcement corrosion is the major cause of premature deterioration of reinforced concrete structures in the chloride-laden Niger Delta region of Nigeria. This study evaluated the extent of deterioration of an existing 45 years old concrete quay structure. The methodology adopted for the study includes conducting a visual inspection on the structure to determine the current condition of the structure and the nature of testing required. Next, several non-destructive tests were carried out to determine the compressive strength, nature of corrosion and the impact on the structure. Water samples were also collected for chemical analysis, to ascertain the corrosion inducing compounds present in the surrounding seawater. The results indicated that the quay structure suffered from chloride-induced corrosion, imposed by the surrounding seawater. Measurement of the level of corrosion carried out on steel reinforcement samples obtained from the quay showed a high-level of corrosion, with rates of 0.65 uA/cm3, evident by an average weight loss of 47% per meter length of steel. Compressive strength obtained via rebound hammer test showed average concrete strength loss of 28% from the original as-built strength of 40 N/mm2. The results showed that the rate of corrosion and strength deterioration depended on the nature and length of exposure. Elements of the structure that were exposed to tidal exposure conditions experienced greater levels of deterioration compared to elements that were continuously submerged.
Investigation of the ground conditions is used for the economical design of the sub- structural elements. It is also necessary to obtained sufficient information on type, characteristics and distributions of a soil and rock underlying at a site of proposed structures for feasibility and economic studies for the proposed project. Thus the purpose of this article was to investigate engineering properties of the soils Wolkite University. To achieve the objective samples from different parts of the compound were collected and laboratory tests were done on the collected samples. The grain size analysis test result showed that the dominant proportion of soil particle in the research area is clay, which have clay content ranging from 5.4 – 40 5%, silt faction 17.6 - 60.7%, sand fraction 14.5 - 54.6% and gravel content from 0.0 – 24.8%. The result of Atterberg Limit test on the soil in the research area showed a liquid limit ranging from 29 – 73%, plastic limit ranging from 21 – 35% and plastic index from 13 – 34%. The specific sravity ranges from 2.40 to 2.70. Free swell test conducted on the samples collected shows range from 18 – 50%. From the compaction test results the maximum dry density (MDD) of wolkite University soil ranges from 1.20 to 1.62 g/cm3 and the optimum moisture content ranges 17.5 to 36.5 percent. According to the Unified Soil Classification System, the soil is categorized as silt and silty sand. Finally one-dimensional consolidation test was done and it shows that the area under investigation is over consolidated in its natural state, have compression index ranging from 0.33-0.40, recompression index ranging from 0.017-0.066, and coefficient of permeability ranging from 10-7 to 10-9 cm/sec.
Construction industry involves the application of different construction materials and equipment that makes the industry to consume big capital budget. Concrete is one of the construction materials which is the composition of cement, coarse aggregate, fine aggregate and water. Among the production processes of concrete, curing is a vital process to give the concrete it’s final strength. To attain the required final strength of concrete suitable amount and quality of water should be applied. Curing usually conducted by application of enough water on the casted structure for the required days of curing. But the application of the usual watering method for the areas like Assosa town is very difficult since there is a high scarcity of water in the town. The main objective of this study is to compare the compressive strength of C25 concrete cured by water curing and shrinkage reducing admixture (Polyethylene glycol 4000). And specifically to determine the physical properties of ingredients used in mix designing process, to determine compressive strength of C25 concrete cured by water immersion (CCWI), cured by water sprinkling (CCWS) and cured by self-curing admixture (Polyethylene glycol 4000) (CCS) and finally to compare the curing capacity of CCWI, CCWS and CCS, C25 concretes based on the determined compressive strength results. Based on the 28th day mean compressive strength results, CCWI, CCWS and CCS samples attained 33.53Mpa, 28.8Mpa and 34.37Mpa compressive strength results respectively. According to the observed change in compressive strength from the 7th to 14th to 28th days of curing CCS samples shows higher increment in compressive strength than both CCWI and CCWS samples which indicates better curing capacity.
The objective was to investigate partial replacement of single and mixed coloured waste glass bottle powder for cement in concrete technology. Ordinary Portland cement in concrete mix was replaced with bottle glass waste powder of 30%, 50% and 70% respectively during mixing. A mix design ratio of 1:2:4 with water-to-cement ratio of 0.6 and design strength of 20MPa was used. Concrete cubes of sizes 150mmx150mmx150mm were cast and slump tested. Compressive strength density and percentage of water absorption test for concrete curing ages at 7- and 28-days were determined respectively. The slump test results showed decreasing slump values with increasing proportions of glass bottle waste powder. Further tests on the concrete specimen showed decreased compressive strength, density and percentage of water absorption values as glass bottle waste powder in concrete increased as compared to the control concrete mix. Replacement of glass bottle powder of 30% for cement in the concrete showed an enhanced performance when compared with the other percentage ratios used as well as the control mix. The study therefore recommends a 30% glass bottle waste powder to replace cement. The study recommends a study of the replacement over a longer period to verify the properties obtained.
The aims of this research is to assess the situation of the urban water supply and build hydraulic network model with all possible scenario used to meet water supply with demand. In this study, data of Water production and consumption, the pressure zones or topography and customers’ meter reading (water billed) approaches was used to evaluate the daily consumption and production. Also, the prevalence of water connection per family, per capital consumption and the level of mode of services have been used in assessment of water supply coverage. In the town, the distribution of mode of services; house connection, yard connection and public tap were 5%, 60% and 35% respectively. Also average per capital consumption is 34.5 l/c/d, whereas the average of water connection per family was 0.527 (52.7%) connection per family. In the modeling, the system has been modified using the design criteria of velocity and pressure. Areas with high pressures in the existing system have been identified and efficient hydraulic network model was provided. In this process of modeling and analysis; the tools such as Microsoft excel and Water CAD v6.5 was used.
The paper analyzes the causes and mechanisms for sliding in the settlement Mahmutovic, municipality of Sapna, that threatened three residential buildings. After the investigations carried out (four exploratory boreholes B-1 to B-4) and detailed engineering-geological mapping, a detailed engineering and geological map of the landslide was prepared. Based on the established properties of the landslide (size, volume, type of landslide), the causes and mechanisms of sliding, it was proposed measures of remediation landslide. After simulations on numerical models, using the PLAXIS 2D v8.5 software package, it is suggested to build a retaining wall on the counterfort, making of drainage systems in the form of fish bones and regulation of the roof water and fecal water in the appropriate receiver or drainage system.
The term landslide is well known to the general public and it is associated mainly with negative news of material and human casualties. This is why they are often mentioned in the media when they are already happened. Landslides are defined as the movement of soil or rock masses down the slope. It includes all forms of movement from landsliding, rolling of stones, falling rocks, rotational and translational sliding to the flow of different materials. Movements take place mainly on curved sliding surfaces. Moving of the mass on or along the slope (sliding) can be slow and barely noticeable in time, but it can also be very fast and destructive. The causes of landslides occurrence may be different, but in general, a landslide occurs when the active forces (mainly gravity) exceed the strength of soil materials and rocks that form the slope. Causes include factors that increase the effects of traction forces and factors that contribute to the weak or reduced strength of the slope material. Recently, mostly caused by extreme precipitation in a relatively short time, the numerous landslides in BiH have been activated. This paper presents the status and realization of landslide rehabilitation projects in Sarajevo Canton (SC).
While solving waste management (WM) planning problems, it may often be preferable to generate several quantifiably good options that provide multiple, contrasting perspectives. This is because WM planning generally contains complex problems that are riddled with inconsistent performance objectives and contain design requirements that are very difficult to quantify and capture when supporting decision models must be constructed. The generated alternatives should satisfy all of the stated system conditions, but be maximally different from each other in the requisite decision space. The process for creating maximally different sets of solutions is referred to as modelling-to-generate-alternatives (MGA). Simulation-optimization approaches have frequently been used to solve computationally difficult, stochastic WM problems. This paper outlines a stochastic multicriteria MGA approach for WM planning that can generate sets of maximally different alternatives for any simulation-optimization method that employs a population-based solution algorithm. This algorithmic approach is computationally efficient because it simultaneously produces the prescribed number of maximally different solution alternatives in a single computational run of the procedure. The efficacy of this stochastic MGA method is demonstrated on a “real world” waste management facility expansion case.
Most of the RCC columns are designed as short columns in practice. With the advancement of structural engineering concept and availability of high strength materials now it is increasing to apply slender column in some situations. Unlike short column, slender column design procedure requires so many criteria to reach a final design. In this study the behavior of slender column was studied. Different factors related to slender column performances are discussed here. This study will help the designer to predict the slender column performances in different situations. This study covers the discussion of sway frame, non-sway frame, P-Delta effect, story drift & displacement, earthquake load and some other necessary parameters as a whole. Some important comparisons also studied at the end.
The paper proposes a simple method which optimises the design of plane, rigid no sway frame structures based on the system buckling load. It is centred on either maximising the buckling load or minimising the weight of the structure, or both; and to have all stories buckling at the same time. The approach to calculate the system buckling load is derived and also presented. The optimisation method is applied to various frames examples and the results are compared to that obtained from a system buckling analysis performed with ANSYS finite element analysis (FEA) software. The proposed optimisation procedure proved successful for no sway multi-story rigid frames, as validated by the acceptable percentage differences of below 5% from the FEA analysis.
