Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 46035

Civil and Environmental Engineering

Comparison of Mechanical and Thermal Properties of Concrete Containing Petroleum and Biopolymer Aggregate
This paper is about the development of a stable and reproducible ultra-lightweight concrete with the inclusion of expanded poly-lactic acid (EPLA) beads as replacement for expanded polystyrene (EPS) and assessing the feasibility of EPLA as a lightweight aggregate that will deliver advantages such as eco-friendly concrete and non-petroleum polymer aggregate. Nine mixes using different mix proportions were prepared. The variables used in this study include polymer types, EPLA ratio, EPS ratio, perlite ratio and curing regimes. The engineering properties considered include workability, density, compressive strength, tensile strength and thermal conductivity. The experimental results show that an increase in EPLA and EPS ratio resulted in a reduction of density, compressive strength and tensile strength. In addition, the bio-polymer aggregate was degraded and shrank in the alkaline environment of concrete. The rate of degradation was increased as the curing method changed from air curing to water curing. Furthermore, a simple method is proposed to estimate the required water-cement ratio and cement content for ultra-lightweight concrete.
Evaluation of Fresh, Strength and Durability Properties of Self-Compacting Concrete Incorporating Bagasse Ash
Self-compacting concrete is an engineered concrete that flows and de-airs without additional energy input. Such concrete requires a high slump which can be achieved by the addition of superplasticizers to the concrete mix. In the present work, bagasse ash is utilised as a replacement of cement in self-compacting concrete. This serves the purpose of both land disposal and environmental concerns related to the disposal of bagasse ash. Further, an experimental program was carried out to study the fresh, strength, and durability properties of self-compacting concrete made with bagasse ash. The mixes were prepared with four percentages (0, 5, 10 and 15) of bagasse ash as partial replacement of cement. Properties investigated were; Slump-flow, V-funnel and L-box, Compressive strength, Splitting tensile strength, Chloride-ion penetration resistance and Water absorption. Compressive and splitting tensile strength tests were conducted at the age of 7 and 28 days. Rapid chloride-ion permeability test was carried at the age of 28 days and water absorption test was carried out at the age of 7 days after initial curing of 28 days. Test results showed that there is an increase in the compressive strength and splitting tensile strength of the concrete specimens having up to 10% replacement level, however, there is a slight decrease at 15% level of replacement. Resistance to chloride-ion penetration of the specimens increased as the percentage of replacement was increased. The charge passed in all the specimens containing bagasse ash was lower than that of the specimen without bagasse ash. Water absorption of the specimens decreased up to 10% replacement level and increased at 15% level of replacement. Hence, it can be concluded that optimum level of replacement of cement with bagasse ash in self-compacting concrete comes out to be 10%; at which the self-compacting concrete has satisfactory flow characteristics (as per the European guidelines), improved compressive and splitting tensile strength and better durability properties as compared to the control mix.
A Construction Management Tool: Determining a Projects Schedule Typical Behaviors Using Cluster Analysis
Delays in the construction industry are a global phenomenon. Many construction projects experience extensive delays exceeding the initially estimated completion time. The main purpose of this study is to identify construction projects typical behaviors in order to develop a management tool. Being able to know a construction projects schedule tendency will enable evidence-based decision-making to allow resolutions to be made before delays occur. This study presents an innovative approach that uses Cluster Analysis Method to support predictions during Earned Value Analyses. A clustering analysis was used to predict future scheduling, Earned Value Management (EVM), and Earned Schedule (ES) principal Indexes behaviors in construction projects. The analysis was made using a database with 90 different construction projects. It was validated with additional data extracted from literature and with another 15 contrasting projects. For all projects, planned and executed schedules were collected, and the EVM and ES principal indexes were calculated. Since all projects have different construction times, to standardize and compare the data, the values of estimated completion time were considered over 10 equal parts, that is, ten tenths. A complete linkage classification method was used. In this way, the cluster analysis made considers that the distance (or similarity) between two clusters must be measured by its most disparate elements, i.e. that the distance is given by the maximum span among its components. Finally, through the use of EVM and ES Indexes and Tukey and Fisher Pairwise Comparisons, the statistical dissimilarity was verified, and four clusters were obtained. It can be said that construction projects show an average delay of 35% of its planned completion time. Furthermore, four typical behaviors were found, and for each of the obtained clusters, the interim milestones and the necessary rhythms of construction were identified. In general, detected typical behaviors are: (1) Projects that perform a 5% of work advance in the first 2 tenths and maintain a constant rhythm until completion (greater than 10% for each remaining tenth), being able to finish on the initially estimated time. (2) Projects that start with an adequate construction rate but suffer minor delays culminating with a total delay of almost 27% of the planned time. (3) Projects which start with a performance below the planned rate and end up with an average delay of 64% and (4) projects that begin with a poor performance, suffer great delays and end up with an average delay of a 120% of the planned completion time. The obtained clusters compose a tool to identify the behavior of new construction projects by comparing their current work performance to the validated database, thus allowing the correction of initial estimations towards more accurate completion schedules.
Predicting Long-Term Performance of Concrete under Sulfate Attack
Cement-based materials have been using in various reinforced concrete structural components as well as in nuclear waste repositories. The sulfate attack has been an environmental issue for cement-based materials exposed to sulfate bearing groundwater or soils, and it plays an important role in the durability of concrete structures. The reaction between penetrating sulfate ions and cement hydrates can result in swelling, spalling and cracking of cement matrix in concrete. These processes induce a reduction of mechanical properties and a decrease of service life of an affected structure. It has been identified that the precipitation of secondary sulfate bearing phases such as ettringite, gypsum, and thaumasite can cause the damage. Furthermore, crystallization of soluble salts such as sodium sulfate crystals induces degradation due to formation and phase changes. Crystallization of mirabilite (Na₂SO₄:10H₂O) and thenardite (Na₂SO₄) or their phase changes (mirabilite to thenardite or vice versa) due to temperature or sodium sulfate concentration do not involve any chemical interaction with cement hydrates. Over the past couple of decades, an intensive work has been carried out on sulfate attack in cement-based materials. However, there are several uncertainties still exist regarding the mechanism for the damage of concrete in sulfate environments. In this study, modelling work has been conducted to investigate the chemical degradation of cementitious materials in various sulfate environments. Both internal and external sulfate attack are considered for the simulation. In the internal sulfate attack, hydrate assemblage and pore solution chemistry of co-hydrating Portland cement (PC) and slag mixing with sodium sulfate solution are calculated to determine the degradation of the PC and slag-blended cementitious materials. Pitzer interactions coefficients were used to calculate the activity coefficients of solution chemistry at high ionic strength. The deterioration mechanism of co-hydrating cementitious materials with 25% of Na₂SO₄ by weight is the formation of mirabilite crystals and ettringite. Their formation strongly depends on sodium sulfate concentration and temperature. For the external sulfate attack, the deterioration of various types of cementitious materials under external sulfate ingress is simulated through reactive transport model. The reactive transport model is verified with experimental data in terms of phase assemblage of various cementitious materials with spatial distribution for different sulfate solution. Finally, the reactive transport model is used to predict the long-term performance of cementitious materials exposed to 10% of Na₂SO₄ for 1000 years. The dissolution of cement hydrates and secondary formation of sulfate-bearing products mainly ettringite are the dominant degradation mechanisms, but not the sodium sulfate crystallization.
The Influence of Oil Palm Empty Fruit Bunch Fibre Geometry on Mechanical Performance of Cement Bonded Fibre Boards
The mechanical properties of cement bonded fibreboards theoretically influenced by several factors like density, water-cement ratio, fibre to cement ratio and geometry of fibre have been discussed by previous researchers. This experimental research work was conducted to explore the role of EFB Fibre geometry on the mechanical performances of cement boards. The experiment work designed for 1300 Kg/m³ density boards consist of two parts, first is cement boards mixed with different length of EFB; retain 7 mesh (R4M), retain 14 mesh (R14M) and retain 80 mesh (R80M). subsequently, second part is based on the cement boards fabricated from mixed of 6 different percentage lengths of EFB known as SA, SB, SC, SD, SE and SF. The ratio of EFB to cement was 3:1, while water used in the system was 35% with added of 3% Calcium Chloride (CaCl₂) as an additive. Whereas, water and additive were calculated based on cement weight. The mechanical properties were investigated in this study like modulus of elasticity (MOE), modulus of rupture (MOR) and internal bonding (IB). It was observed that the higher presence of shorter EFB (R80M) in cement boards, the lower mechanical properties were produced. The boards fabricated with heterogeneous fibre length, SE (35% R4M + 45% R14M + 20% R80M) produced the highest mechanical properties with MOE of 4859.5 N/mm², MOR of 10.06 N/mm² and IB of 0.36 N/mm². The properties of MOE and MOR for boards fabricated from SE mixture were satisfied the minimum requirement of British standard.
Numerical Study on Pretensioned Bridge Girder Using Thermal Strain Technique
The transfer of prestress force from prestressing strands to the surrounding concrete is dependent on the bond between the two materials. It is essential to understand the actual bond stress distribution along the transfer length to determine the transfer zone in pre-tensioned concrete. A 3-D nonlinear finite element model has been developed to simulate the transfer of prestress force from steel to concrete in pre-tensioned bridge girders through thermal strain technique using commercially available package ABAQUS. Full-scale bridge girder has been analyzed with thermal strain approach where the damage plasticity constitutive model has been used to model concrete. Parameters such as concrete strain, effective prestress, upward camber and longitudinal stress have been compared with analytical results. The discrepancy between numerical and analytical values was within 20%. The paper also presents a convergence study on mesh density and aspect ratio of the elements to perform the finite element study.
Seismic Performance of a Framed Structure Retrofitted with Damped Cable Systems
In this work, the effectiveness of damped cable systems (DCS) on the mitigation of earthquake-induced response of a framed structure is investigated. The seismic performance of DCS is investigated using fragility analysis and life cycle cost evaluation of an existing building retrofitted with DCS, and the results are compared with those of the structure retrofitted with viscous dampers. The comparison of the analysis results reveals that, due to the self-centering capability of the DCS, residual displacement becomes nearly zero in the structure retrofitted with the DCS. According to the fragility analysis, the structure retrofitted with the DCS has smaller probability of reaching a limit states compared to the structure with viscous dampers. It is also observed that both the initial and life cycle costs of the DCS method required for the seismic retrofit is smaller than those of the structure retrofitted with viscous dampers.
Implementing Building Information Modelling to Attain Lean and Green Benefits
Globally the built environment sector is striving to be highly efficient, quality-centred and socially-responsible. Built environment sector is an integral part of the economy and plays an important role in urbanization, industrialization and improved quality of living. The inherent challenges such as excessive material and process waste, over reliance on resources, energy usage, and carbon footprint need to be addressed in order to meet the needs of the economy. It is envisioned that these challenges can be resolved by integration of Lean-Green-Building Information Modelling (BIM) paradigms. Ipso facto, with BIM as a catalyst, this research identifies the operational and tactical connections of lean and green philosophies by providing a conceptual integration framework and underpinning theories. The research has developed a framework for BIM-based organizational capabilities for enhanced adoption and effective use of BIM within architectural organizations. The study was conducted through a sequential mixed method approach focusing on collecting and analyzing both qualitative and quantitative data. The framework developed as part of this study will enable architectural organizations to successfully embrace BIM on projects and gain lean and green benefits.
Numerical Study for Compressive Strength of Basalt Composite Sandwich Infill Panel
In this study, we investigated the buckling performance of basalt fiber reinforced polymer (BFRP) sandwich infill panels. Fiber Reinforced Polymer (FRP) is a major evolution for energy dissipation when used as infill material of frame structure, a basic Polymer Matrix Composite (PMC) infill wall system consists of two FRP laminates surrounding an infill of foam core. Furthermore, this type of component is for retrofitting and strengthening frame structure to withstand the seismic disaster. In-plane compression was considered in the numerical analysis with ABAQUS platform to determine the buckling failure load of BFRP infill panel system. The present result shows that the sandwich BFRP infill panel system has higher resistance to buckling failure than those of glass fiber reinforced polymer (GFRP) infill panel system, i.e. 16% increase in buckling resistance capacity.
Wind Fragility for Soundproof Wall with the Variation of Section Shape of Frame
Recently, damage due to typhoons and strong wind are on the rise. Considering this issue, we evaluated the performance of soundproofing walls based on the strong wind fragility by means of numerical analysis. Among the components of the soundproof wall, aluminum frame was the most vulnerable member; thus, we have considered different section of aluminum frame in the determination of wind fragility. Wind load was randomly generated using Monte Carlo Simulation method. Moreover, limit state was based on the test standard of road construction soundproofing wall. In this study, the strong wind fragility was determined by considering the influence factors of wind exposure category, soundproof wall’s installation position, and shape of aluminum frame section. Results of this study could be used to determine the section shape of the frame that has high resistance to the wind during construction of the soundproofing wall.
Wind Fragility for Honeycomb Roof Cladding Panels Using Screw Pull-Out Capacity
The failure of roof cladding mostly occurs due to the failing of connection between claddings and purlins, which is the pull-out of screw connecting the two parts when the pull-out load, i.e. typhoon, is higher than the resistance of the connection screw. As the typhoon disasters in Korea are constantly on the rises, probability risk assessment (PRA) has become a vital tool to evaluate the performance of civil structural. In this study, we attempted to determine the fragility of roof cladding with the screw connection. Experimental study was performed to evaluate the pull-out resistance of screw joint between honeycomb panels and back frames. Subsequently, by means of Monte Carlo Simulation method, probability of failure for these type of roof cladding was determined. The results that the failure of roof cladding was depends on their location on the roof, for example, the edge most panel has the highest probability of failure.
Buckling Resistance of Basalt Fiber Reinforced Polymer Infill Panel Subjected to Elevated Temperatures
Performance of Basalt Fiber Reinforced Polymer (BFRP) sandwich infill panel system under diagonal compression was studied by means of numerical analysis. Furthermore, the variation of temperature was considered to affect the mechanical properties of BFRP, since their composition was based on polymeric material. Moreover, commercial finite element analysis platform ABAQUS was used to model and analyze this infill panel system. Consequently, results of the analyses show that the overall performance of BFRP panel had a 15% increase compared to that of GFRP infill panel system. However, the variation of buckling load in term of temperature for BFRP system showed a more sensitive nature compare to those of GFRP system.
Reliability Based Maintenance Management Methodology to Minimise Life Cycle Cost of Water Supply Networks
With a large percentage of the countries’ total infrastructure expenditure attributed to water network maintenance, it is essential to optimise maintenance strategies to rehabilitate or replace underground pipes before failure occurs. The aim of this paper is to provide water utility managers with a maintenance management approach for underground water pipes, subject to external loading and material corrosion, to give the lowest life cycle cost over a predetermined time period. This reliability based maintenance management methodology details the optimal years for intervention, the ideal number of maintenance activities to perform before replacement and specifies feasible renewal options and intervention prioritisation to minimise the life cycle cost. The study was then extended to include feasible renewal methods by determining the structural condition index and potential for soil loss, then obtaining the failure impact rating to assist in prioritising pipe replacement. A case study on optimisation of maintenance plans for the Melbourne water pipe network is considered in this paper to evaluate the practicality of the proposed methodology. The results confirm that the suggested methodology can provide water utility managers with a reliable systematic approach to determining optimum maintenance plans for pipe networks.
Damage Assessment in Arch Bridges using Vibration based Techniques
Most structures are built to have a long life. However, during this long life, damage can be incurred due to structural deterioration, environmental effects and random actions such as impacts. Early damage assessment and required retrofitting will enable the continued safe and efficient functioning of structures. In this context, vibration based techniques have emerged with the potential for reliable damage assessment. This study develops a Multi-Criteria Approach based on vibration characteristics for detecting and locating damage in arch bridges. Steel arch bridges are one of the most aesthetically pleasing bridge types in which damage detection has been rarely studied. In particular, the arch rib and struts (or columns in deck type bridges), which are important structural components, have received little attention in damage detection. This study will therefore focus on damage detection in arch bridge structural components using indices based on modified Modal Flexibility (MF) and Modal Strain Energy (MSE) methods which depend on variations in the vibration characteristics of the bridge. The capability in precise damage detection of the proposed method is demonstrated through analyses of two existing full scale long span arch bridges. The study is carried out through numerical simulations of validated deck type and through type arch bridge models with the use of data from previous experimental testing. Data obtained from finite element analyses of the healthy and damaged arch bridge models are applied into the modified MF and MSE algorithms for detecting and locating the damage. Results demonstrate that the proposed multi criteria method is capable of detecting and locating damage in the arch rib and vertical columns of deck type arch bridges.
Characteristic on Compressive Strength of Blast Slag and Fly Ash Hybrid Geopolymer Mortar
Geopolymer mortar is produced by alkaline activation of pozzolanic materials such as fly ground granulated blast-furance slag (GGBFS) and fly ash (FA). Its unique reaction pathway facilitates rapid strength development in comparison with hydration of ordinary Portland cement (OPC). Geopolymer can be fabricated using various types and dosages of alkali-activator, which effectively gives a wider control over the performance of the final product. The present study investigates the effect of types of precursors and curing conditions on the fresh state and strength development characteristics of geopolymers, thereby comparatively exploring the effect of precursors from various sources of origin. The obtained result showed that the setting time and strength development of the specimens with the identical mix proportion but different precursors displayed significant variations.
Causes of Variation Orders in the Egyptian Construction Industry: Time and Cost Impacts
Variation orders are of great importance in any construction project. Variation orders are defined as any change in the scope of works of a project that can be an addition omission, or even modification. This paper investigates the variation orders that occur during construction projects in Egypt. The literature review represents a comparison of causes of variation orders among Egypt, Tanzania, Nigeria, Malaysia and the United Kingdom. A classification of occurrence of variation orders due to owner related factors, consultant related factors and other factors are signified in the literature review. These classified events that lead to variation orders were introduced in a survey with 19 events to observe their frequency of occurrence, and their time and cost impacts. The survey data was obtained from 87 participants that included clients, consultants, and contractors and a database of 42 scenarios was created. A model is then developed to help assist project managers in predicting the frequency of variations and account for a budget for any additional costs and minimize any delays that can take place. Two experts with more than 25 years of experience were given the model to verify that the model was working effectively. The model was then validated on a residential compound that was completed in July 2016 to prove that the model actually produces acceptable results.
Estimation of Subgrade Resilient Modulus from Soil ‎Index Properties
Determination of Resilient Modulus (MR) is quite important for ‎characterizing materials in pavement design and evaluation. The main ‎focus of this study is to develop a correlation that predict the resilient ‎modulus of subgrade soils from simple and easy measured soil index ‎properties. To achieve this objective, three subgrade soils representing ‎typical Khartoum soils were selected and tested in the laboratory for ‎measuring resilient modulus. Other basic laboratory tests were ‎conducted on the soils to determine their physical properties. Several ‎soil samples were prepared and compacted at different moisture ‎contents and dry densities and then tested using resilient modulus ‎testing machine. Based on experimental results, linear relationship of ‎MR with the consistency factor "Fc" which is a combination of dry ‎density, void ratio and consistency index had been developed. The ‎results revealed that very good linear relationship found between the ‎MR and the consistency factor with a coefficient of linearity (R2) more ‎than 0.9. The consistency factor could be used for the prediction of the ‎MR of compacted subgrade soils with precise and reliable results.‎
Effectiveness of Crystallization Coating Materials on Chloride Ions Ingress in Concrete
This paper aims to evaluate the effectiveness of different crystalline coating materials concerning of chloride ions penetration. The concrete ages at the coating installation and its moisture conditions were addressed; where these two factors may play a dominant role in the effectiveness of the used materials. Rapid chloride ions penetration test (RCPT) was conducted at different ages and moisture conditions according to the relevant standard. In addition, the contaminated area and the penetration depth of the chloride ions were investigated immediately after the RCPT test using Chemical identifier, 0.1M silver nitrate AgNO₃ solution. Results have shown that the very low chloride ions penetrability, for the studied crystallization materials, were investigated only with the old age concrete (G1). The significant reduction in chloride ions penetrability was illustrated after 7 days of installing the crystalline coating layers. Using images analysis method, imageJ software, is more reliable to describe the contaminated area of chloride ions, where it considered in the images analysis; the distribution of aggregate, heterogeneous of cement mortar and color variation of concrete.
Re-Analyzing Energy-Conscious Design
An energy-conscious design for a classroom in a hot-humid climate is reanalyzed. The hypothesis of this study is that use of photovoltaic (PV) electricity generation in building operation energy consumption will lead to re-analysis of the energy-conscious design. Therefore, the objective of this study is to reanalyze the energy-conscious design by evaluating the environmental impact of operational energy with PV electrical generation. Using the hierarchical design structure of Eco-indicator 99, the alternatives for energy-conscious variables are statistically evaluated by applying a two-stage nested (hierarchical) ANOVA. The recommendations for the preferred solutions for application of glazing types, wall insulation, roof insulation, window size, roof mass, and window shading design alternatives were changed (for example, glazing type recommendations were changed from low-emissivity glazing, green, and double- glazed windows to low-emissivity glazing only), whereas the applications for the lighting control system and infiltration are not changed. Such analysis of operational energy can be defined as environment-conscious analysis.
Flexural Behavior of Reinforced Concrete Beams Strengthened with Carbon Fiber Reinforced Polymers Sheets
Carbon fiber reinforced polymers (CFRP) have been widely used as a strengthening material for reinforced concrete structures. This paper describes the flexural behavior of five reinforced concrete (RC) beams strengthened with CFRP sheets. One beam was a control beam without strengthening whereas the other four beams were strengthened using CFRP sheets with different strengthened techniques. This included externally bonded technique (EB) with one and two layers of CFRP sheets, near surface mounted (NSM) using two rolled FRP sheets, and hybrid technique (EB and NSM). After applying the strengthening materials, the beams were tested using two point loading setup. Three strengthened beams failed by CFRP debonding and one failed by CFRP rupture. All the strengthened beams showed an increase in the ultimate capacity compared with the control beam. This increase ranged between a minimum value of 32% in the NSM with rolled CFRP sheets and a maximum value of about 58% in the beam strengthened with the hybrid technique.
Kinematic Simulation of Angulated Scissor Structures
Deployable structures are designed to undergo specifically desired motions through exciting their internal mechanisms. One of the most efficient types of these structures is scissor structure. The basic unit of these structures is called duplet. A duplet consists of two hinged bars called uniplets connected at an intersection point by a pivotal connection. These uniplets might be of straight, angulated or multi-angulated shapes. Using angulated uniplets results in reducing the number of structure components and the complexity of joints. This led to important progress in the design of large deployable scissor structures. A numerical incremental-iterative procedure based on the force-method is presented and used to simulate the motion of angulated scissor structures. A cornerstone of the procedure is the formation of the structure equilibrium matrix, where important static/kinematic characteristics are obtained from the matrix subspaces and used in the simulation analysis. An approach has been developed to derive the equilibrium matrix of two-dimensional angulated uniplet composed of two elements or more. An algorithm is applied to split the rigid body mechanism components, arising due to the absence of rigid foundation, from the resulting mechanism modes. The numerical procedure has been programmed using MATLAB, and the program has been verified through several verification examples.
Reliability Analysis of Corrosion Affected Steel Pipes with Longitudinal Surface Cracks
Corrosion or manufacture defects can cause surface cracks in steel pipes. This paper presents a reliability based methodology for the assessment of corrosion affected steel pipe cracking. Based on the recently derived elastic fracture toughness model for steel pipes with longitudinal surface cracks, a linear elastic fracture mechanics failure criterion is employed for steel pipes. A stochastic model of the load effect is developed, and the first passage probability theory is employed to quantify the probability of failure. A case study is carried out to demonstrate the use of the proposed methodology, after which sensitivity analysis is conducted to examine the effects of the random variables on the failure probability. The methodology presented in this paper can assist pipe engineers and asset managers in developing a risk-informed and cost-effective strategy for better management of corroded steel pipes.
Service Life Prediction of Tunnel Structures Subjected to Water Seepage
Water seepage is one of the most common causes of damage in tunnel structures, which can cause direct and indirect e.g. reinforcement corrosion and calcium leaching damages. Estimation of water seepage or inflow is one of the main challenges in probabilistic assessment of tunnels. The methodology proposed in this study is an attempt for mathematically modeling the water seepage in tunnel structures and further predicting its service life. Using the time-dependent reliability, water seepage is formulated as a failure mode, which can be used for prediction of service life. Application of the formulated seepage failure mode to a case study tunnel is presented.
A Probabilistic Study on Time to Cover Cracking Due to Corrosion
Corrosion of steel in reinforced concrete structures is a major problem worldwide. The volume expansion of corrosion products causes concrete cover cracking, which could lead to delamination of concrete cover. The time to cover cracking plays a key role to the assessment of serviceability of reinforced concrete structures subjected to corrosion. Many analytical, numerical, and empirical models have been developed to predict the time to cracking initiation due to corrosion. In this study, a numerical model based on finite element modeling of corrosion-induced cracking process is used. In order to predict the service life based on time to cover initiation, the numerical approach is coupled with a probabilistic procedure. In this procedure, all the influential factors affecting time to cover cracking are modeled as random variables. The results show that the time to cover cracking is highly variables. It is also shown that rust product expansion ratio and the size of more porous concrete zone around the rebar are the most influential factors in predicting service life of corrosion-affected structures.
Effects of in-Situ Upgrading Project on Private Investment, Land Value, and Residents’ Satisfaction in Afghanistan: A Case Study of Formally and Informally Developed Areas in Kabul
Cities in Afghanistan have been rapidly urbanized, but many parts of the cities have been developed without a detailed land use plan or infrastructure. In other words, they have been informally developed without the government’s leadership. The new government started the In-situ Upgrading Project in Kabul to upgrade roads, the water supply network system, and the surface water drainage system on the existing street layout, with financial support of international agencies since 2003. This project is appropriate as an emergency improvement for living life, but not as essential improvement to living conditions and infrastructure problems because the life ages of the improved facilities are as short as 10–15 years and residents cannot get land tenure in the unplanned areas. Meanwhile, the Land Readjustment System (LRS) conducted in Japan has advantages that rearrange irregularly shaped land lots and develop the infrastructure. This study aims to investigate the effects of the in-situ Upgrading Project on private investment, land price, and residents’ satisfaction with projects in Kart-e-Char where properties are registered and Afshar-e-Silo Lot1 where the properties are unregistered. These projects are located 5 km and 7 km from the CBD area of Kabul. This study discusses whether LRS should be applied to the unplanned area based on questionnaire and interview responses by experts experienced in the In-situ Upgrading Project and with knowledge of LRS. The analysis results reveal that, in Kart-e-Char, a lot of private investments have been made in the construction of medium-rise buildings for commercial and residential purposes, land values have incrementally increased since the project, and residents are commonly satisfied with the road pavement and drainage systems but dissatisfied with electricity and water supplies as well as the lack of public facilities (e.g., parks and sport facilities). In Afshar-e-Silo Lot1, basic infrastructures such as paved roads and surface water drainage systems have been improved by the project. After the project, a few three- and four-storied residential buildings had been built with very low-level private investments, and significant increases in land prices were not evident after the project. The residents are satisfied with the paved roads, drainage system, and little increase of land price, but there is still no drinking water supply system or tenure security; moreover, there is a lack of public facilities, such as parks, sport facilities, mosques, and schools. The results of the questionnaire and interviews with the four engineers highlight the problems to be solved in unplanned areas if LRS is applied - namely, land use differences, types and conditions of infrastructure to be installed by the project, and time spent for consensus building among the residents under the projects’ budget limitation.
Model of Elastic Fracture Toughness for Steel Pipes with External Longitudinal Cracks
The most common type of cracks that appear on metal pipes is longitudinal cracks. For steel pipes, the existence of plasticity eases the stress intensity at the crack front and consequently increases the fracture resistance of steel. It should be noted that linear elastic fracture mechanics (LEFM) has been widely accepted by engineers. In order to make the LEFM applicable to steel material, the increase of fracture toughness due to plasticity should be excluded from the total fracture toughness of the steel. This paper aims to develop a model of elastic fracture toughness for steel pipes with external longitudinal cracks. The derived elastic fracture toughness is a function of crack geometry and material properties of the cracked pipe. The significance of the derived model is that the well-established linear elastic fracture mechanics can be used for steel material in predicting the fracture failure.
Laboratory Calibration of Soil Pressure Transducer for a Specified Field Application
Nowadays soil pressure transducers are widely used to measure the soil stress states in laboratory and field experiments. The soil pressure transducers, investigated here, are traditional diaphragm-type earth pressure cells (DEPC) based on strain gauge principle. It is found that the output of these sensors varies with the soil conditions as well as the position of a sensor. Therefore, it is highly recommended to calibrate the pressure sensors based on the similar conditions of their intended applications. The factory calibration coefficients of the EPCs are not reliable to use since they are normally calibrated by applying fluid (a special type of oil) pressure only over load sensing zone, which does not represent the actual field conditions. Thus, the calibration of these sensors is utmost important, and they play a pivotal role for assessing earth pressures precisely. In the present study, TML soil pressure sensor is used to compare its sensitivity under different calibration systems, for example, fluid calibration, and static load calibration with or without soil. The results report that the sensor provides higher sensitivity (more accurate results) under soil calibration system.
An Experimental Study on Service Life Prediction of Self: Compacting Concrete Using Sorptivity as a Durability Index
Permeation properties have been widely used to quantify durability characteristics of concrete for assessing long term performance and sustainability. The processes of deterioration in concrete are mediated largely by water. There is a strong interest in finding a better way of assessing the material properties of concrete in terms of durability. Water sorptivity is a useful single material property which can be one of the measures of durability useful in service life planning and prediction, especially in severe environmental conditions. This paper presents the results of the comparative study of sorptivity of Self-Compacting Concrete (SCC) with conventionally vibrated concrete. SCC is a new, special type of concrete mixture, characterized by high resistance to segregation that can flow through intricate geometrical configuration in the presence of reinforcement, under its own mass, without vibration and compaction. SCC mixes were developed for the paste contents of 0.38, 0.41 and 0.43 with fly ash as the filler for different cement contents ranging from 300 to 450 kg/m3. The study shows better performance by SCC in terms of capillary absorption. The sorptivity value decreased as the volume of paste increased. The use of higher paste content in SCC can make the concrete robust with better densification of the micro-structure, improving the durability and making the concrete more sustainable with improved long term performance. The sorptivity based on secondary absorption can be effectively used as a durability index to predict the time duration required for the ingress of water to penetrate the concrete, which has practical significance.
Investigating the Effect of Using Amorphous Silica Ash Obtained from Rice Husk as a Partial Replacement of Ordinary Portland Cement on the Mechanical and Microstructure Properties of Cement Paste and Mortar
from rice husk as a partial replacement of ordinary Portland cement (OPC) on the mechanical and microstructure properties of cement paste and mortar. ASA was used in partial replacement of ordinary Portland cement in the following percentages 3 percent, 5 percent, 8 percent and 10 percent. These partial replacements were used to produce Cement-ASA paste and Cement-ASA mortar. ASA was found to contain all the major chemical compounds found in cement with the exception of alumina, which are SiO2 (91.5%), CaO (2.84%), Fe2O3 (1.96%), and loss on ignition (LOI) was found to be 9.18%. It also contains other minor oxides found in cement. Consistency of Cement-ASA paste was found to increase with increase in ASA replacement. Likewise, the setting time and soundness of the Cement-ASA paste also increases with increase in ASA replacements. The test on hardened mortar were destructive in nature which include flexural strength test on prismatic beam (40mm x 40mm x 160mm) at 2, 7, 14 and 28 days curing and compressive strength test on the cube size (40mm x 40mm, by using the auxiliary steel platens) at 2,7,14 and 28 days curing. The Cement-ASA mortar flexural and compressive strengths were found to be increasing with curing time and decreases with cement replacement by ASA. It was observed that 5 percent replacement of cement with ASA attained the highest strength for all the curing ages and all the percentage replacements attained the targeted compressive strength of 6N/mm2 for 28 days. There is an increase in the drying shrinkage of Cement-ASA mortar with curing time, it was also observed that the drying shrinkages for all the curing ages were greater than the control specimen all of which were greater than the code recommendation of less than 0.03%. The scanning electron microscope (SEM) was used to study the Cement-ASA mortar microstructure and to also look for hydration product and morphology.
Increasing Sustainability by Using the Potential of Urban Rivers in Developing Countries with a Biophilic Design Approach
Population growth, urban development and urban buildup have disturbed the balance between nature and the city and these factors have caused that the side of the urban rivers lose their quality. While in the past, the sides of urban rivers were considered as urban green space. Urban rivers and their sides that have environmental, social and economic values are important to achieve sustainable development. So far, efforts have been made at various scales in various cities around the world to revitalize these areas. On the other hand, Biophilic design is an innovative design approach in which attention to natural details and relation to nature is a fundamental concept. The purpose of this study is to provide an integrated framework of urban design using the potential of urban rivers (In order to increase sustainability) with a biophilic design approach to be used in the cities in the developing countries. The methodology of the research is based on the Collection of data and information from research and projects including study on biophilic design, investigations and projects related to the urban rivers, and a review of the literature on sustainable urban development. Then studying the boundary of urban rivers is completed by examining case samples. Eventually, integrated framework of urban design, to design the boundaries of urban rivers in the cities of developing countries is presented regarding the factors affecting the design of these areas. The result shows that according to this framework, the potential of the river banks is utilized to increase not only the environmental sustainability but also social, economic and physical stability with regard to water, light, and the usage of indigenous materials and etc.