International Science Index

International Journal of Structural and Construction Engineering

Seismic Vulnerability Assessment of Existing Unreinforced Masonry Buildings
The construction of unreinforced masonry buildings (URM) has been done based on some ‘typical’ models and prior to the seismic code in many countries. Moreover, construction and material production many depend on local practice, thus showing significant variation in workmanship, material quality, and also lacking quality control. This vague in the material properties increase concern of seismic assessment of URM buildings. This study presents a seismic assessment of a typical masonry building in Tirana one of the most populated cities in Balkans. The assessment was carried out based on actual material properties obtained from existing buildings. Elastic modulus and shear modulus of masonry units obtained from existing building material test were modified by diagonal shear test of 1.2m x 1.2m masonry unit. Specimens for diagonal shear test were constructed based on existing building material properties, and the test was carried out according to ASTM. The Equivalent Frame Method (EFM) was used for modeling of the structure, and pushover analysis was performed to obtain the buildings capacity. The study shows that a modification of shear modulus and elastic modulus by diagonal shear test is necessary to reach more accurate assessment of URM building. The assessment results of the typical masonry structure indicated the high vulnerability of these structures in the case of a strong seismic event.
Development of Interaction Diagram for Eccentrically Loaded Reinforced Concrete Sandwich Walls with Different Design Parameters
Sandwich sections have a very complex nature due to variability of behavior of different materials within the section. Cracking, crushing and yielding capacity of constituent materials enforces high complexity of the section. Furthermore, slippage between the different layers adds to the section complex behavior. Conventional methods implemented in current industrial guidelines do not account for the above complexities. Thus, a throughout study is needed to understand the true behavior of the sandwich panels thus, increase the ability to use them effectively and efficiently. The purpose of this paper is to conduct numerical investigation using ANSYS software for the structural behavior of sandwich wall section under eccentric loading. Sandwich walls studied herein are composed of two RC faces, a foam core and linking shear connectors. Faces are modeled using solid elements and reinforcement together with connectors are modeled using link elements. The analysis conducted herein is nonlinear static analysis incorporating material nonlinearity, crashing and crushing of concrete and yielding of steel. The model is validated by comparing it to test results in literature. After validation, the model is used to establish extensive parametric analysis to investigate the effect of three key parameters on the axial force bending moment interaction diagram of the walls. These parameters are the concrete compressive strength, face thickness and number of shear connectors. Furthermore, the results of the parametric study are used to predict a coefficient that links the interaction diagram of a solid wall to that of a sandwich wall. The equation is predicted using the parametric study data and regression analysis. The predicted α was used to construct the interaction diagram of the investigated wall and the results were compared with ANSYS results and showed good agreement.
Minimum Weight Design of Cold-Formed Steel Beams According to Eurocode 3
Cold-formed steel has an advantage of great flexibility of its cross-sectional shapes and sizes that are available to the construction industry. This is one of the most desirable features of thin-walled cold-formed steel members. Furthermore, such members generally have high strength and stiffness to weight ratio. This makes cold-formed steel members economical and at the same time very easy to erect and install. In addition, cold-formed steel is very durable, easy to transport and handle, and can be easily recycled. More importantly, they could be shaped to nearly any open cross sections. This allows for the use of formal optimisation strategies to find optimum cross sectional shapes for the members. This study deals with the minimum weight design of simply supported cold-formed steel beams subjected to uniformly distributed load. The beam composed of two thin-walled cold-formed steel back-to-back lipped channel sections. The connection between the lipped channels (i.e. C sections) was assumed to be rigid. For the optimisation process, Generalised Reduced Gradient (GRG) technique was implemented which is embedded within Excel Solver add-in tool. GRG method was adopted because of its robustness and efficiency in dealing with a wide range of engineering optimisation problems as demonstrated by several works available in the literature. Equally important, the GRG is part and parcel of Microsoft Excel which means that there is no need to pay for extra licence to run any optimisation problem. The design variables were considered to be the width (b), web depth (h) and lip depth (c) of the C section. The constraint functions were based on the provision and design requirement according to Eurocode 3 (EC3). Several design parameters were taken into account, namely, the thickness (t) of the section, yield strength, load intensity and span of the beam. Results of the optimum design charts were presented for various practical cases to reflect the effect of the design parameters on the optimum section. Following a comprehensive investigation of the minimum weight design of the beam, it was concluded that the effect of yield strength on the gross area of the section is insignificant compared to the intensity of the load. On the other hand, noticeable increase of section depth, hence the gross area of the section as the beam span length increases from 5 m to 9 m.
Non-Chronological Approach in Crane Girder and Composite Steel Beam installation: Case Study
The time delay and structural stability are major issues in big size projects, due to several factors. Improper planning and poor coordination lead to delay in construction, which sometimes lead to reworking or rebuilding. This definitely increases the cost and time of project. This situation stresses the structural engineers to plan out of the limits of contemporary technology utilizing non-chronological approach with creative ideas. One of the strategies to solve this issue is through structural integrity solutions in a cost-effective way. We have faced several problems in a project worth 470 million USD and one such issue is crane girder installation with composite steel beams. We have applied structural integrity approach with proper revised planning schedule to solve the problem efficiently with minimal expenses.
Finite Element Investigation on Effect of Bolt Arrangements in Structural Behavior of Cold-Formed Beam
This paper presents a numerical investigation onto the structural behaviour of cold-formed steel (CFS) through plates bolted connections. A finite element study was carried out to investigate the effect of different bolt arrangements of CFS beam-to-column connections on structural characteristics of CFS beam sections such as stiffness, ductility, and energy dissipation under monotonic loading. Results from nonlinear FE analysis using three type of CFS sections (flat flange, segmental flange, and curved flange) with different thickness show that regardless of CFS sections, using different bolt arrangement has negligible effects on moment-rotation curve of CFS beams with a thin thickness. On the other hand, in thicker sections (6mm thickness), bolt arrangement has significant effects on the moment-rotation behaviour of CFS beams. Indeed, regardless of bolt arrangements, the segmental and curved flange beams have close moment-rotation behaviour and using these sections instead of flat flange sections significantly improves the moment-rotation behaviour of CFS beams.
A Decision Support System for Financial Processes of Infrastructure Construction Projects
A decision support system for the financial process of infrastructure construction projects is really important for the EPC contractor in managing the entire structure of the power project. The study of this topic is done by the help of Topsis method. Previous studies on this were limited to only start part of the project. But this paper provides the entire decision support system along with financials for the entire phase of the power project. This paper actually proposes a decision support system that actually assesses the various aspect of the financial processes of the newly constructed power plant project or which deals with the construction phase of the power project. The proposed model helps the organization to take suitable decision regarding the progress of the power project. This will help in the planning, management and other aspects of the ongoing construction project. Results show that this Topsis method framework can actually help the EPC contractor to analyze in detail about the finance part i.e. the cash flow etc. and about the planning activities for the successful execution of the project in all aspects such as timely commission, maintaining profitability of the project for the organization even after the stage of the completion of the project.
Improving Inelastic Capacity of Cold-Formed Steel Beams Using Slotted Blotted Connection
The focus of this paper is to incorporating the slotted bolted connection into the cold-formed steel (CFS) beams with aim of increasing inelastic bending capacity through bolt slip. An extensive finite element analysis was conducted on the through plate CFS bolted connections which are equipped with the slotted hole. The studied parameters in this paper included the following: CFS beam section geometry, the value of slip force, CFS beam thickness. The numerical results indicate that CFS slotted bolted connection exhibit higher inelastic capacity in terms of ductility compare to connection with standards holes. Moreover, the effect of slip force was analysed by comparing the moment-rotation curves of different models with different slip force value. As a result, as the slip force became lower, there was a tendency for the plastic strain to extend from the CFS member to the connection region.
Effect of Hooked-End Steel Fibres Geometry on Pull-Out Behaviour of Ultra-High Performance Concrete
In this study, a comprehensive approach has been adopted to examine in detail the effect of various hook geometries on bond-slip characteristics. Extensive single fibre pull-out tests on ultra-high performance matrix with three different W/B ratios and embedded lengths has been carried out. Test results showed the mechanical deformation of fibre hook is the main mechanism governing the pull-out behaviour. Furthermore, the quantitative analyses have been completed to compare the hook design contribution of 3D, 4D and 5D fibres to assess overall pull-out behaviour. It was also revealed that there is a strong relationship between the magnitude of hook contribution and W/B ratio (i.e., matrix strength). Reducing the W/B ratio from 0.20 to 0.11 greatly optimizes the interfacial transition zone (ITZ) and enables better mobilization, straightening of the hook and results in bond-slip-hardening behaviour.
Innovation in Lean Thinking to Achieve Rapid Construction
Lean thinking holds a potential for improving construction sector. Therefore, this concept should be adopted by construction players and academicians in the real industry. Bridging from that, a learning process for construction players regarding this matter should be the agenda in gaining the knowledge as a preparation for their career. The lean principles give opportunities of reducing lead times, eliminating non-value adding activities, reducing variability and are facilitated by methods such as pull scheduling, simplified operations and buffer reduction. Thus, drive for rapid construction. Rapid construction is a systematic approach in enhancing efficiency to deliver project using time reduction while lean is the continuous process of eliminating waste, meeting or exceeding all customer requirements, focusing on the entire value stream and pursuing perfection in the execution of a constructed project. The methodology presented is shown to be valid through literature, interviewing and questionnaire. The result shown majority of construction players unfamiliar with lean thinking and they agreed that it can improve the construction process flow. With this background knowledge established and identified, best practices and recommended action are drawn.
The Capacity of Bolted and Screw Connections in Cold-Formed Steel Truss Structure Through Analytical and Experimental Method
Designing of cold-formed steel capacity connections often based on the formula used for hot rolled steel. It makes the result of the actual capacity connection doesn’t accurate anymore. When the hot rolled steel receives the axial load pull, it will have different characteristics. As the result, there will be failure result when designing Truss structure made of hot rolled steel. This research aims to determine the capacity of actual cold-formed steel connections section which is loaded by the axial tensile force. It will test the appeal of the connection using bolt grafting tool and screw grafting tool. The variations of the test will be on the type of connection (single and double slap), the number of the connection tools and connection configuration. Bold and screw connections failure mode observed in this research are different each other. Failure mode of bolted connections includes sliding pivot plate, tearing at the plate and cutting of the bolt head. While the failure mode of screw connections includes tilting, hole-bearing, pull over and cutting the screw body out. This research was conducted using a laboratory test of HW2-600S Universal Testing Machine model with ASTM E8. It has done in the materials testing laboratory of Mechanical Engineering Department, Faculty of Engineering UNNES. The results obtained through the laboratory diversification towards theoretical calculations using the standards specified in ISO 7971-2013 Cold-Rolled Steel Structures. Based on the research, it can be concluded that the effective connection in receiving force strength is bolted connections neither single nor double plate. The method used is by applying 4 bolts through 2 parallel lines configuration. Furthermore, this connection deals with the consequences of holding the highest Pmaks, lowest failure risk and getting a little kind of mode of failure.
The Effect of Air Entraining on Compressive Strength of Fiber Reinforced Concretes
Freeze-thaw cycles are one of the greatest threat to concrete durability. Lately protection against this threat excites scientist’s attention. Air-entraining admixtures widely have been used to be able to produce freeze-thaw resistant at concretes. The use of air-entraining agents (AEAs) enhances not only freeze-thaw endurance but also the properties of fresh concrete such as segregation, bleeding and flow ability. This paper examines the effects of air-entraining on compressive strength of concrete. Air-entraining is used between 0.05% and 0.4% by weight of cement. One control and four fiber reinforced concrete mix are prepared and three specimens are tested for each mixes. It is concluded from the test results that when air entraining is increased the compressive strength of concrete reduce for all mixes with AEAs.
Ultrasonic Pulse Velocity of Hybrid Fiber Reinforced Concretes
Because of the easy applying and not costing too much ultrasonic pulse velocity (UPV) is one of the most used non-destructive technique to determine concrete characteristics along with impact-echo, Schmidt rebound hammer (SRH) and pulse-echo. This article investigates the relationship between UPV and compressive strength of hybrid fiber reinforced concretes. Water/cement ratio (w/c) was kept at 0.4 for all concrete mixes. Compressive strength of concrete was targeted at 35 MPa. UPV testing and compressive strength tests were carried out at the curing age of 28 days. The UPV of concrete containing steel fibers has been found to be higher than plain concrete for all the testing groups. It is decided that there is not a certain relationship between fiber addition and strength.
Use of Waste Marbles in Self Compacting Lightweight Concrete
In this study, the effects of waste marbles as aggregate material on fresh and hardened characteristics of self compacting lightweight concrete are investigated. For this purpose, self compacting light weight concrete are produced by waste marble aggregates are replaced with fine aggregate at 5%, 7.5%, and 10% ratios. Fresh concrete properties, slump flow, T50 time, V funnel, compressive strength and ultrasonic pulse velocity of self compacting lightweight concrete are determined. It is concluded from the test results that using of waste marbles as aggregate material by replacement with fine aggregate affects positively fresh and hardened concrete characteristics of self compacting lightweight concretes.
Establishing the Optimum Location of a Single Tower Crane Using a Smart Mathematical Model
Due to the great development in construction and building field, there are many projects and huge works appeared which consume many construction materials. Accordingly, that causes difficulty in handling traditional transportation means (ordinary cranes) due to their limited capacity; there is an urgent need to use high capacity cranes such as tower cranes. However, with regard to their high expense, we have to take into consideration selecting what type of cranes to be utilized which has been discussed by many researchers. In this research, a proposed technique was created to select the suitable type of crane and the best place for crane erection, in addition to minimum radius for requested crane in order to minimize cost. To fulfill that target, a computer program is designed to numerate these problems, demonstrating an example explaining how to apply program and the result donated the best place.
Bending Tests for the Axial Load Identifications in Space Structures with Unknown Boundary Conditions
This paper presents the extension of a static method for the axial load identifications in prismatic beam-columns with uncertain length and unknown boundary conditions belonging to generic space structures, such as columns of space frames or struts and ties of space trusses. The non-destructive method requires the knowledge of the beam-column flexural rigidity only. Flexural displacements are measured at five cross sections along the beam-column subjected to an additional vertical load at the mid-span. Unlike analogous dynamic methods, any set of experimental data may be used in the identification procedure. The method is verified by means of many numerical and experimental tests on beam-columns having unknown boundary conditions and different slenderness belonging to three different space prototypes in small-scale. Excellent estimates of the tensile and compressive forces are obtained for the elements with higher slenderness and when the greatest possible distance between sensors is adopted. Moreover, the application of larger values of the vertical load and very accurate displacement measurements are required. The method could be an efficacious technique in-situ, considering that safety inspections will become increasingly important in the near future, especially because of the improvement of the material properties that allowed designing space structures composed of beam-columns with higher slenderness.
Seismic Performance Evaluation of Structures with Hybrid Dampers Based on FEMA P-58 Methodology
In this study, a hybrid energy dissipation device is developed by combining a steel slit plate and friction pads to be used for seismic retrofit of structures, and its effectiveness is investigated by comparing the life cycle costs of the structure before and after the retrofit. The seismic energy dissipation capability of the dampers is confirmed by cyclic loading tests. The probabilities of reaching various damage states are obtained by fragility analysis, and the life cycle costs of the model structures are computed using the PACT (Performance Assessment Calculation Tool) program based on FEMA P-58 methodology. The fragility analysis shows that the probabilities of reaching limit states are minimized by the seismic retrofit with hybrid dampers and increasing column size. The seismic retrofit with increasing column size and hybrid dampers results in the lowest repair cost and shortest repair time. This research was supported by a grant (13AUDP-B066083-01) from Architecture & Urban Development Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government.
Tensile Force Estimation for Real-Size Pre-Stressed Concrete Girder using Embedded Elasto-Magnetic Sensor
The tensile force of Pre-Stressed Concrete (PSC) girder is the most important factor for evaluating the performance of PSC girder bridges. To measure the tensile force of PSC girder, several NDT methods were studied. However, conventional NDT method cannot be applied to the real-size PSC girder because the PS tendons could not be approached. To measure the tensile force of real-size PSC girder, this study proposed embedded EM sensor based tensile force estimation method. The embedded EM sensor could be installed inside of PSC girder as a sheath joint before the concrete casting. After curing process, the PS tendons were installed, and the tensile force was induced step by step using hydraulic jacking machine. The B-H loop was measured using embedded EM sensor at each tensile force steps and to compare with actual tensile force, the load cell was installed at each end of girder. The magnetization energy loss, that is the closed area of B-H loop, was decreased according to the increase of tensile force with regular pattern. Thus, the tensile force could be estimated by the tracking the change of magnetization energy loss of PS tendons. Through the experimental result, the proposed method can be used to estimate the tensile force of the in-situ real-size PSC girder bridge.
Numerical Simulation and Experimental Study on Cable Damage Detection Using an MFL Technique
Non-destructive testing on cable is in great demand due to safety accidents at sites where many equipments using cables are installed. In this paper, the quantitative change of the obtained signal was analyzed using a magnetic flux leakage (MFL) method. A two-dimensional simulation was conducted with a FEM model replicating real elevator cables. The simulation data were compared for three parameters (depth of defect, width of defect and inspection velocity). Then, an experiment on same conditions was carried out to verify the results of the simulation. Signals obtained from both the simulation and the experiment were transformed to characterize the properties of the damage. Throughout the results, a cable damage detection based on an MFL method was confirmed to be feasible. In further study, it is expected that the MFL signals of an entire specimen will be gained and visualized as well.
Visualization of Corrosion at Plate-Like Structures Based on Ultrasonic Wave Propagation Images
A non-contact nondestructive technique using laser-induced ultrasonic wave generation method was applied to visualize corrosion damage at aluminum alloy plate structures. The ultrasonic waves were generated by a Nd:YAG pulse laser, and a galvanometer-based laser scanner was used to scan specific area at a target structure. At the same time, wave responses were measured at a piezoelectric sensor which was attached on the target structure. The visualization of structural damage was achieved by calculating logarithmic values of root mean square (RMS). Damage-sensitive feature was defined as the scattering characteristics of the waves that encounter corrosion damage. The corroded damage was artificially formed by hydrochloric acid. To observe the effect of the location where the corrosion was formed, the both sides of the plate were scanned with same scanning area. Also, the effect on the depth of the corrosion was considered as well as the effect on the size of the corrosion. The results indicated that the damages were successfully visualized for almost cases, whether the damages were formed at the front or back side. However, the damage could not be clearly detected because the depth of the corrosion was shallow. In the future works, it needs to develop signal processing algorithm to more clearly visualize the damage by improving signal-to-noise ratio.
Simulation and Experimental Study on Tensile Force Measurement of PS Tendons Using an Embedded EM Sensor
The tensile force estimation PS tendons is in great demand on monitoring the structural health condition of PSC girder bridges. Measuring the tensile force of the PS tendons inside the PSC girder using conventional methods is hard due to its location. In this paper, an embedded EM sensor based tensile force estimation of PS tendon was carried out by measuring the permeability of the PS tendons in PSC girder. The permeability is changed due to the induced tensile force by the magneto-elastic effect and the effect then lead to the gradient change of the B-H curve. An experiment was performed to obtain the signals from the EM sensor using three down-scaled PSC girder models. The permeability of PS tendons was proportionally decreased according to the increase of the tensile forces. To verify the experiment results, a simulation of tensile force estimation will be conducted in further study. Consequently, it is expected that both the experiment results and the simulation results increase the accuracy of the tensile force estimation, and then it could be one of the solutions for evaluating the performance of PSC girder.
Study on Buckling and Yielding Behaviors of Low Yield Point Steel Plates
Stability and performance of steel plates are characterized by geometrical buckling and material yielding. In this paper, the geometrical buckling and material yielding behaviors of low yield point (LYP) steel plates are studied from the point of view of their application in steel plate shear wall (SPSW) systems. Use of LYP steel facilitates the design and application of web plates with improved buckling and energy absorption capacities in SPSW systems. LYP steel infill plates may yield first and then undergo inelastic buckling. Hence, accurate determination of the limiting plate thickness corresponding to simultaneous buckling and yielding can be effective in seismic design of such lateral force-resisting and energy dissipating systems. The limiting thicknesses of plates with different loading and support conditions are determined theoretically and verified through detailed numerical simulations. Effects of use of LYP steel and plate aspect ratio parameter on the limiting plate thickness are investigated as well. In addition, detailed studies are performed on determination of the limiting web-plate thickness in code-designed SPSWs. Some practical recommendations are accordingly provided for efficient seismic design of SPSW systems with LYP steel infill plates.
Application of GIS-Based Construction Engineering: An Electronic Document Management System
This paper describes the implementation of a GIS to provide decision support for successfully monitoring the movements and storage of materials, hence ensuring that finished products travel from the point of origin to the destination construction site through the supply-chain management (SCM) system. This system ensures the efficient operation of suppliers, manufacturers, and distributors by determining the shortest path from the point of origin to the final destination to reduce construction costs, minimize time, and enhance productivity. These systems are essential to the construction industry because they reduce costs and save time, thereby improve productivity and effectiveness. This study describes a typical supply-chain model and a geographical information system (GIS)-based SCM that focuses on implementing an electronic document management system, which maps the application framework to integrate geodetic support with the supply-chain system. This process provides guidance for locating the nearest suppliers to fill the information needs of project members in different locations. Moreover, this study illustrates the use of a GIS-based SCM as a collaborative tool in innovative methods for implementing Web mapping services, as well as aspects of their integration by generating an interactive GIS for the construction industry platform.
Risk Based Building Information Modeling (BIM) for Urban Infrastructure Transportation Project
Building Information Modeling (BIM) is a holistic documentation process for operational visualization, design coordination, estimation and project scheduling. BIM software defines objects parametrically and it is a tool for virtual reality. Primary advantage of implementing BIM is the visual coordination of the building structure and systems such as Mechanical, Electrical and Plumbing (MEP) and it also identifies the possible conflicts between the building systems. This paper is an attempt to develop a risk based BIM model which would highlight the primary advantages of application of BIM pertaining to urban infrastructure transportation project. It has been observed that about 40% of the Architecture, Engineering and Construction (AEC) companies use BIM but primarily for their outsourced projects. Also, 65% of the respondents agree that BIM would be used quiet strongly for future construction projects in India. The 3D models developed with Revit 2015 software would reduce co-ordination problems amongst the architects, structural engineers, contractors and building service providers (MEP). Integration of risk management along with BIM would provide enhanced co-ordination, collaboration and high probability of successful completion of the complex infrastructure transportation project within stipulated time and cost frame.
Optimum Switch Temperature for Phase Change Materials in Buildings
To avoid or at least to attenuate the global warming, it is essential to reduce the energy consumption of the buildings where the biggest potential of savings exists. The impending danger can come from the increase in the needs of air conditioning not only because of the climate warming but also the fast equipping of emerging or developing countries. Passive solutions exist and others are in promising development and therefore, must be applied wherever it is possible. Even if they do not always avoid the resort to an active cooling (mechanical), they allow lowering the load at an acceptable level which can be possibly taken in relay by the renewable energies. These solutions have the advantage to be relatively less expensive and especially adaptable to the existing housing. However, it is the internal convection resistance that controls the heat exchange between the phase change materials (PCM) and the indoor temperature because of the very low heat coefficients of natural convection. Therefore, it is reasonable to link the switch temperature Tm to the temperature of the substrate (walls and ceiling) because conduction heat transfer is dominant. In this case, external conditions (heat sources such as solar irradiation and ambient temperatures) and conductivities of envelope constituents are the most important factors. The walls are not at the same temperature year round; therefore, it is difficult to set a unique switch temperature for the whole season, making the average values a key parameter. With this work, the authors’ aim is to see which parameters influence the optimum switch temperature of a PCM and additionally, if a better selection of PCMs relating to their optimum temperature can enhance their energetic performances.
Identification of Factors Affecting Labor Productivity in Construction Projects of Iran
Labor productivity is very important and gained special concerns among professionals in the construction industry, worldwide. Productivity improvements on labors achieve higher cost savings with minimal investment. Due to the fact that profit margins are small on construction projects, cost savings associated with productivity are crucial to become a successful contractor. This research program studies and highlights the factors affecting labor productivity in Iranian construction industry. A questionnaire was used to gather the relevant data from respondents who involve in managing various types of projects in wide areas in Iran. It involved ranking 57 predefined factors divided into 5 categories: Human/Labor; Financial; Management; Equipments/Materials and Environmental. Total 62 feedbacks were analyzed through the Relative Importance Index (RII) technique. The top ten factors affecting construction labor productivity in Iran are: 1) Professional capability of contractor project manager, 2) skills of contractor’s project management team, 3) professional capability of owner project manager, 4) professional capability of Consulting Project manager, 5) discipline working, 6) delay payments by the owner, 7) material shortages, 8) delays in delivery of materials, 9) turnover power of the owner, 10) poor site management. Recommendations have been made in the study to address these factors. The research has direct benefits to key stakeholders in Iranian construction industry.
A Study on the Reinforced Earth Walls Using Sandwich Backfills under Seismic Loads
Reinforced earth walls offer excellent solution to many problems associated with earth retaining structures especially under seismic conditions. Use of cohesive soils as backfill material reduces the cost of reinforced soil walls if proper drainage measures are taken. This paper presents a numerical study on the application of a new technique called sandwich technique in reinforced earth walls. In this technique, a thin layer of granular soil is placed above and below the reinforcement layer to initiate interface friction and the remaining portion of the backfill is filled up using the existing insitu cohesive soil. A 6 m high reinforced earth wall has been analysed as a two-dimensional plane strain finite element model. Three types of reinforcing elements such as geotextile, geogrid and metallic strips were used. The horizontal wall displacements and the tensile loads in the reinforcement were used as the criteria to evaluate the results at the end of construction and dynamic excitation phases. Also to verify the effectiveness of sandwich layer on the performance of the wall, the thickness of sand fill surrounding the reinforcement was varied. At the end of construction stage it is found that the wall with sandwich type backfill yielded lower displacements when compared to the wall with cohesive soil as backfill. Also with sandwich backfill, the reinforcement loads reduced substantially when compared to the wall with cohesive soil as backfill. Further, it is found that sandwich technique as backfill and geogrid as reinforcement is a good combination to reduce the deformations of geosynthetic reinforced walls during seismic loading.
Testing Method of Soil Failure Pattern of Sand Type as an Effort to Minimize the Impact of the Earthquake
Nowadays many people do not know the soil failure pattern as an important part in planning the under structure caused by the loading occurs. This is because the soil is located under the foundation, so it cannot be seen directly. Based on this study, the idea occurs to do a study for testing the soil failure pattern, especially the type of sand soil under the foundation. The necessity of doing this to the design of building structures on the land which is the initial part of the foundation structure that met with waves/vibrations during an earthquake. If the underground structure is not strong it is feared the building thereon more vulnerable to the risk of building damage. This research focuses on the search of soil failure pattern, which the most applicable in the field with the loading periodic re-testing of a particular time with the help of the integrated video visual observations performed. The results could be useful for planning under the structure in an effort to try the upper structure is minimal risk of the earthquake.
Examination of Occupational Health and Safety Practices in Ghana
Occupational Health and Safety (OHS) issues has been a major challenge to the Ghanaian government. The purpose of the study was to examine OHS practices in Ghana. The study looked at various views from different scholars about OHS practices in order to achieve the objective of the study. Literature review was conducted on OHS in Ghana. Findings from the study shows Ministry of Roads and Transport (MRT) and Ministry of Water Resources, Works and Housing (MWRWH) are two government ministries in charge of construction and implementation of the construction sector policy. The Factories, Offices and Shops Act 1970, Act 328 and the Mining Regulations 1970 LI 665 are the two major edicts. The study presents a strong background on OHS practices in Ghana and contribute to the body of knowledge on the solution to the current trends and challenges of OHS in the construction sector.
Assessment of Human Factors Analysis and Classification System in Construction Accident Prevention
Majority of the incidents and accidents in complex high-risk systems that exist in the construction industry and other sectors have been attributed to unsafe acts of workers. The purpose of this paper was to asses Human Factors Analysis and Classification System (HFACS) in construction accident prevention. The study was conducted through the use of secondary data from journals, books and internet to achieve the objective of the study. The review of literature looked into details of different views from different scholars about HFACS framework in accidents investigations. It further highlighted on various sections or disciplines of accident occurrences in human performance within the construction. The findings from literature review showed that unsafe acts of a worker and unsafe working conditions are the two major causes of accident in the construction industry.Most significant factor in the cause of site accident in the construction industry is unsafe acts of a worker. The findings also show how the application of HFACS framework in the investigation of accident will lead to the identification of common trends. Further findings show that provision for the prevention of accident will be made based on past accident records to identify and prioritize where intervention is needed within the construction industry.
Design Flood Estimation in Satluj Basin-Challenges for Luhri Hydro Electric Project, Himachal Pradesh-India
Introduction: Design Flood studies are essential for proper planning and functioning of water resource projects. Design flood estimation for the Luhri Hydro Electric Project (LHEP), located in State of Himachal Pradesh, India, on the river Satluj, was a big challenge in view of the river flowing in Himalayan region from Tibet to India, having a large catchment area of varying topography, climate and vegetation. No data was available for the part of river in Tibet as gauging was not possible at many locations. Discharge data was available for the river at Khab and Wangtu only, upstream of Nirath Dam of LHEP. The estimation of design flood using standard methods was not possible. This challenge was met using two different approaches for upper and lower catchment vis-a vis Flood Frequency Approach and Unit Hydrograph Approach. Methodologies Adopted: i) Wangtu: Flood Frequency Approach Upto Wangtu/Nathpa, design flood was estimated using Flood Frequency analysis for return period 1 in 10,000 years. The flood peaks were taken from daily observed discharges at Wangtu, therefore the observed flood peaks were increased by 10% to make them instantaneous. A Design Flood of 4717 cumec was obtained at Wangtu. ii) Wangtu to Nirath: Unit Hydrograph (Hydrometrological) Approach. The method is based upon the catchment response to the rainfall pattern observed (Probable Maximum Precipitation -PMP) in a particular catchment area and is found to be very convenient and sufficiently accurate for practical purposes. The design flood computation mainly involves estimation of a design storm hyetograph and derivation of catchment response function. A unit hydrograph is assumed to represent the entire catchment area. The main advantage of the hydrometrological approach is that it gives a complete flood hydrograph and this allows making a realistic determination of its moderation effect while passing through a reservoir or a river reach. These studies were used to arrive at Probable Maximum Flood (PMF) for the catchment area below Wangtu using a PMP value of 23.2 cm. The PMF so obtained was 10096 cumec. Final Result: The total Design Flood value obtained was (4717 + 10096) 14813 cumec. Conclusion: Even though, several factors are relevant when deciding about the method to be used for design flood estimation, data availability and the purpose of study are the most important factors. Since, in general, water resource development cannot wait for the hydrological data of adequate quality and quantity to be available, flood estimation has to be done using whatever data is available. Depending upon the type of data available for a particular catchment, the method to be used is to be selected.