Showing papers in "Ksce Journal of Civil Engineering in 2016"

Public transportation and sustainability: A review

Abstract: Public transportation is often framed as a key component of building sustainable cities. Conversely, the social, economic, and environmental impacts of transport are framed as critical issues that can challenge the sustainability of cities and regions. This paper presents a critical literature review of the relationship between public transportation and sustainability. First the paper offers a review of key sustainable transportation concepts and how public transport contributes to sustainability goals. Second, the paper reviews past studies that analyse sustainable transportation in order to develop recommendations for planning, engineering, and researching sustainable public transport. Finally, the paper concludes by offering suggestions for future research into the sustainability performance of public transit.

A Stereovision-based Crack Width Detection Approach for Concrete Surface Assessment

Abstract: To quantitatively evaluate crack width of concrete structures surface, this paper presents a stereovision-based crack width detection method. Compared with the traditional visual inspection with single camera, this approach uses a pair of cameras to capture cracks images for recovering 3D coordinates of crack edge, and does not needs scale attached to concrete surface for converting measurement unit. A novel Canny-Zernike combination algorithm is utilized to obtain the image coordinates of crack edge in the left crack image, this combination algorithm can achieve 0.02 subpixel precision. The 3D coordinates of crack edge are acquired by projecting crack edge curve on concrete surface where cracks are located. The crack width is assessed by the minimum distance between two sides of crack edge. The detection tests are conducted on three concrete beams destroyed in static test, and the crack width of two inspection zones on each beam is acquired. Experimental results indicate that the stereovision-based crack width detection approach can accurately measure the crack width compared with the crack width gauge or the vernier calliper. This verifies the proposed method is applicable and useful for assessing the crack width of concrete surface.

An Analogy between Various Machine-learning Techniques for Detecting Construction Materials in Digital Images

Abstract: Digital images and video clips collected at construction jobsites are commonly used for extracting useful information. Exploring new applications for image processing techniques within the area of construction engineering and management is a steady growing field of research. One of the initial steps for various image processing applications is automatically detecting various types of construction materials on construction images. In this paper, the authors conducted a comparison study to evaluate the performance of different machine learning techniques for detection of three common categorists of building materials: Concrete, red brick, and OSB boards. The employed classifiers in this research are: Multilayer Perceptron (MLP), Radial Basis Function (RBF), and Support Vector Machine (SVM). To achieve this goal, the feature vectors extracted from image blocks are classified to perform a comparison between the efficiency of these methods for building material detection. The results indicate that for all three types of materials, SVM outperformed the other two techniques in terms of accurately detecting the material textures in images. The results also reveals that the common material detection algorithms perform very well in cases of detecting materials with distinct color and appearance (e.g., red brick); while their performance for detecting materials with color and texture variance (e.g., concrete) as well as materials containing similar color and appearance properties with other elements of the scene (e.g., ORB boards) might be less accurate.

An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: Secondary flow and bed shear stress

Abstract: High flow velocity near the free surface in rivers is due to the presence of shear stress near the bed and its absence on the free surface. This phenomenon results in unsteadiness of the vertical velocity profile. Moreover, secondary flows in river bends cause velocity variations, accordingly leading to changes in shear stress near the bed. The present study evaluates and analyzes the effect of streamlines variations, maximum velocity distribution, and secondary flow strength on bed shear stress distribution along a 180 degree sharp bend built in the Hydraulic Laboratory of Persian Gulf University. Results suggest of the occurrence of maximum secondary flow strength at the second half of the bend. The evaluation of bed shear stress distribution using the TKE, modified TKE, and Reynolds methods at turbulent boundary layer demonstrated that the maximum shear stress occurred from the entrance of the bend to the bend apex area near the inner wall. Moreover, comparison of the Reynolds shear stress method at distances of 5 and 15% of the flow depth from the bed indicated that the maximum shear stress occurring at the lower layer moved from the 40 degree cross section to 60 degree cross section at the upper layer.

Strength and durability properties of geopolymer concrete made with Ground Granulated Blast Furnace Slag and Black Rice Husk Ash

Abstract: This paper presents an experimental study on the strength and durability properties of Geopolymer concrete prepared using Ground Granulated Blast Furnace Slag (GGBS) and Black Rice Husk Ash (BRHA). The Geopolymer concrete was prepared with GGBS as the primary binder instead of cement and BRHA was replaced with GGBS at various proportions such as 10%, 20% and 30%. The effect of curing temperature on the compressive strength of Geopolymer concrete was studied in addition to the flexural and split tensile strengths. Studies on the durability performance under Sorptivity, Rapid Chloride Permeability Test and Accelerated corrosion were also made. The test results show that the strength of Geopolymer concrete increases with increase in curing temperature. Addition of BRHA in Geopolymer concrete beyond 10% retards the strength development yet the strengths are well above the target for up to 20% replacement levels. At the same time, addition of BRHA significantly improves the durability with reduced sorptivity and chloride permeability when compared to the control concrete. Higher corrosion initiation and delayed cracking time were observed up to 20% BRHA replacement in Geopolymer concrete.

Utilisation of Waste Plastic in Bituminous Mix for Improved Performance of Roads

Abstract: The use of waste plastic as a partial aggregate replacement in bituminous mix products often suffers from weak bonding between the plastic surface and the bitumen This work reports on the use of plastic waste and chemical additives in order to improve the performance of the volumetric and mechanical properties of bituminous mixtures The selected recycled waste plastics were used as partial aggregate replacement in bituminous mix product The plastics were treated using a strong oxidising mixture of dichromate and sulphuric acid while the bitumen was treated with a cross linking agent, polyethyleneimine Three modified bituminous mixtures were prepared and the stiffness results (from Retained Stiffness after Water Immersion Test) were compared with the control bituminous mixture Over the ten measurement cycles it was observed that the stiffness increased by 10% for the chemically modified bituminous mixtures This improvement is attributed to an increase in the bonding forces between the aggregates and the bitumen Furthermore, a mechanism is proposed in order to explain the effect of the chemical additives on the increase in the stiffness of the bituminous mixture

The energy efficiency of China’s regional construction industry based on the three-stage DEA model and the DEA-DA model

Abstract: China’s construction industry has constantly been confronted with the problems, such as high resource consumption, serious pollution and low energy efficiency. Thus, improving the energy efficiency of the construction industry and reducing its energy consumption can not only promote the sustainable development of the socio-economy and eco-economy, but also enhance the overall development level of the construction industry. In the context, the objectives are to put forward a set of systematic methodologies for measuring the energy efficiency of the regional construction industry and analyzing its change trends. First, the energy efficiency index system of the construction industry and its influencing factors are constructed through the literature review. Second, two research methods (the three-stage Data Envelopment Analysis (DEA) model and the Data Envelopment Analysis-Discriminant Analysis (DEA-DA) model) are applied to analyze the energy efficiency in 30 provinces of China and the change trends from 2003 to 2011. The results indicate that after eliminating the influence of the environment factors and random errors, the energy efficiency values of the construction industry in most of the provinces were improved. The mean of China’s energy efficiency of the construction industry in each year was approximately 0.92. Except Shandong with the lowest values, the mean of the other provinces was over 0.8, which reflected that the energy management and utilization levels in the construction industry were relative mature. However, the energy efficiency in most of provinces fluctuated constantly during these nine years, with the peak in 2004 and a downward trend in the overall efficiency after 2004. From the regional aspect, the energy efficiency of the construction industry in the eastern, central and western regions decreased successively; as the development level of the local economy had less significant effects on the energy efficiency, the gaps among the three regions were not obvious.

Bed load sediment transport estimation in a clean pipe using multilayer perceptron with different training algorithms

Abstract: Due to the presence of solid matter in the flow passing through sewer pipes, determining the minimum velocity that prevents sediment deposition is essential. In this study, the Multilayer Perceptron (MLP) network optimized with three different training algorithms, including variable learning rate (MLP-GDX), resilient back-propagation (MLP-RP) and Levenberg-Marquardt (MLP-LM) is studied in terms of ability to estimate sediment transport in a clean pipe. The results indicate that for all algorithms, model ANN(d) that uses volumetric sediment concentration (C V ), median relative size of particles (d/D), ratio of median diameter particle size to hydraulic radius (d/R) and overall sediment friction factor (λ s ) as input parameters, is more accurate than the other models. In predicting Fr, the results of MLP-LM (R 2 = 0.98, RMSE = 0.02 and MAPE = 5.13) are better than MLP-GDX (R 2 = 0.96, RMSE = 0.03 and MAPE = 5.9) and MLP-RP (R 2 = 0.95, RMSE = 0.26 and MAPE = 5.74). A comparison of the model selected in this study with existing equations of sediment transport in sewer pipes also indicates that ANN(d)-LM (RMSE = 0.025 & MAPE = 5.78) perform better than existing equations.

Optimal design of labyrinth spillways using meta-heuristic algorithms

Abstract: The labyrinth spillway continues to be a popular type of the control structures. The focus of the present study is that on the optimization of the shape of the labyrinth spillway through the minimization of the construction costs because the use of it is a suitable solution in the rehabilitation process of existing reservoirs. An Adaptive Neural Fuzzy Inference System (ANFIS) model was developed to determine the discharge coefficient of the labyrinth spillway as a function of the angle between alignment of the crest and direction of flow, the relative depth of flow over spillway and its crest height. Differential Evolution (DE) algorithm and Genetic Algorithm (GA) were adopted to minimize the spillway cost as the objective function by considering certain hydraulic conditions as the constraints of the optimization procedure. The results indicated that DE and GA can respectively reduce 19.3% and 16.6% the construction cost of a real benchmark design.

Engineering properties and microstructural characteristics of foundation silt stabilized by lignin-based industrial by-product

Abstract: This paper presents details of a study that deals with determination of engineering properties and microstructural characteristics of a foundation soil (silt) sedimented in Jiangsu Province of China when it is stabilized by lignin-based industrial by-product. A series of laboratory tests were carried out with respect to evaluate the effect of lignin content and curing time on the overall soil properties including Atterberg limits, pH, unconfined compressive strength, stress-strain characteristics, secant modulus, and California bearing ratio. In addition, scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry studies were conducted to understand the microstructural characteristics and stabilization mechanism of the stabilized silt. The results reveal that lignin has a great potential to improve engineering properties of silt and shows a promising prospect as a new environmentally friendly soil stabilizer. Curing time and lignin content have significant influence on the basic engineering properties and microstructural characteristics of the lignin stabilized silt. The optimum content of lignin for foundation silt in Jiangsu Province of China is approximately 12%. The precipitated cementing material is formed after stabilization of lignin with a period of curing. The stabilized silt switches over its response from a brittle to ductile material in the presence of lignin. Peak analysis results of the pore-size distribution curves demonstrates that the lignin stabilized silt exhibits bimodal behavior when the lignin content less than 8%, whereas it displays unimodal type when the lignin content is more than or equal to 8%. These observations provide enhanced understanding of lignin-based industrial by-product as a soil stabilizer at the foundation construction.

A comparison of Artificial Neural Networks (ANN) and Local Linear Regression (LLR) techniques for predicting monthly reservoir levels

Abstract: Storage dams play a very important role in irrigation especially during lean periods For proper regulation one should make sure the availability of water according to needs and requirements Normally regression techniques are used for the estimation of a reservoir level but this study was aimed to account for a non-linear change and variability of natural data by using Gamma Test, for input combination and data length selection, in conjunction with Artificial Neural Networking (ANN) and Local Linear Regression (LLR) based models for monthly reservoir level prediction Results from both training and validation phase clearly indicate the usefulness of both ANN and LLR based prediction techniques for Water Management in general and reservoir level forecasting in particular, with LLR outperforming the ANN based model with relatively higher values of Nash-Sutcliffe model efficiency coefficnet (R2) and lower values of Root Mean Squared Error (RMSE) and Mean Biased Error (MBE) The study also demonstrates how Gamma test can be effectively used to determine the ideal input combination for data driven model development

Experimental and numerical investigation of the effect of blast-induced vibration from adjacent tunnel on existing tunnel

Abstract: Since the new tunnel is close to existing tunnel, the vibration wave induced by blasting endangers the safety and stabilization of the surrounding rock and the lining of existing tunnel. In the tunnel blasting vibration monitoring and safety prediction, Peak Particle Velocity (PPV) and vibration frequency are used widely as safety standards. To investigate the effect of blast-induced vibration from adjacent tunnel on existing tunnel, field monitoring experiments and a numerical method that is Finite Element Method (FEM) were adopted to study the blasting vibration velocity and vibration frequency of existing tunnel. Combined blasting vibration velocity with vibration frequency, the paper studied axial and radial blasting vibration velocity distributions and the corresponding Power Spectral Density (PSD) distributions of the existing tunnel under the effect of blast-induced vibration from adjacent subway tunnel. And the parameters of constitutive model and blasting loads were also discussed. It is shown that field monitoring experiment and numerical simulation can optimize blasting excavation program and provide a reference for other similar engineering projects.

Characteristics of desulfurized rubber asphalt and mixture

Abstract: This paper investigated the modification mechanism of the desulfurized rubber asphalt, and compared its performances with those of crumb rubber asphalt. The microstructures of desulfurized rubber asphalt and crumb rubber asphalt were identified by using the scanning electron microscope technology, component analysis and infrared spectrum analysis. Conventional and Strategic Highway Research Program (SHRP) performance tests were conducted to evaluate the performances of desulfurized rubber asphalt and crumb rubber asphalt. Mixture performance tests were also performed to characterize the high temperature rutting resistance, low temperature cracking resistance, moisture stability and fatigue life of the desulfurized rubber asphalt mixture and crumb rubber asphalt mixture. It was found that the modification mechanisms of desulfurized rubber asphalt and crumb rubber asphalt are different. The desulfurized rubber can integrate into the asphalt while the crumb rubber mainly exists incompatibly in asphalt. This difference results in the various performances between the desulfurized rubber asphalt and crumb rubber asphalt. Both crumb rubber and desulfurized rubber can improve the performance of asphalt binder and mixture, but the desulfurized rubber asphalt has much lower viscosity and better storage stability than the crumb rubber asphalt. The preparing temperature of the desulfurized rubber asphalt mixture can be reduced by 10∼20°C compared to the crumb rubber asphalt mixture. Moreover, without the interference of solid rubber particles, the desulfurized rubber asphalt can be used in dense-graded asphalt mixture while crumb rubber asphalt mixture tends to use gap gradation with high asphalt content.

Kinetics of nitrate adsorption and reduction by nano-scale zero valent iron (NZVI): Effect of ionic strength and initial pH

Abstract: Kinetic models for pollutants reduction by Nano-scale Zero Valent Iron (NZVI) were tested in this study to gain a better understanding and description of the reaction. Adsorption kinetic models and a heterogeneous catalytic reaction kinetic equation were proposed for nitrate removal and for ammonia generation, respectively. A widely used pseudo-first-order reaction model was a poor fit for nitrate removal in an iron-limiting condition and for ammonia generation in an excess iron condition. However, in this study, pseudo-first-order and pseudo-second-order adsorption kinetic equations were a good fit for nitrate removal; in addition, a Langmuir-Hinshelwood kinetic equation was able to successfully describe ammonia generation, regardless of the NZVI dose, the ionic strength, and the initial pH. These results strongly indicate that nitrate reduction by NZVI is a heterogeneous catalytic reaction, and that that the kinetic models can be used in diverse conditions. The kinetic parameters correlate well with the reaction condition, unless the NZVI dose was greatly increased or unless the NZVI surface was significantly changed at a very high initial pH.

Mechanical properties of oil palm shell lightweight aggregate concrete containing palm oil fuel ash as partial cement replacement

Abstract: The increasing in greenhouse gas emissions, as well as solid waste disposal from the cement manufacturing industry and the Malaysian palm oil industries respectively contributes towards the undesirable 6°C Scenario envisioned by the International Energy Agency The utilization of Palm Oil Fuel Ash (POFA) as partial cement replacement in the production of Oil Palm Shell (OPS) Lightweight Aggregate Concrete (LWAC) would significantly reduce cement consumption and amount of disposed landfill waste In this investigation, the effect of POFA content as partial cement replacement towards the compressive strength of OPS lightweight aggregate concrete has been conducted A total of six OPS LWAC mixtures were prepared with varying the percentages of POFA viz 0%, 10%, 20%, 30%, 40% and 50% to determine the best replacement of POFA as partial cement replacement The ashes were ground to enhance their pozzalanicity The best replacement of POFA-20 was then used to investigate the mechanical properties of OPS LWAC such as compressive strength, flexural strength and modulus of elasticity The concretes containing POFA were placed in different types of curing regimes namely water, air, sprayed and natural weather curing before subjected to compressive strength test and flexural strength test at the age of 28, 60, 180,270 and 365 days The compressive strength was conducted in accordance with the BS EN12390-3 whilst the flexural strength test was carried out in accordance with the BS EN 12390-5 It was found that water curing is the best method amongst others OPS LWAC with POFA exhibits the highest results of compressive strength, flexural strength and modulus of elasticity The production of extra C-S-H gel resulting from better pozzolanic reaction for water cured OPS LWAC with POFA has contributed to the densification of the internal structure that in turn enhances the concrete strength

A review of sustainable network design for road networks

Abstract: The Network Design Problem (NDP) is a strategical decision-making problem in planning, designing, and managing road networks with the aim to make efficient use of limited resources for optimizing the road network performance. Sustainability development is a major concern of various social-economic systems throughout the world. As a critical component of sustainable development, transportation systems should be designed to make positive contributions to the economic, environmental, and social sustainability of the served regions and communities. This requirement significantly uplifts the challenges on the modeling and the analysis of NDP. In this paper, we provide a review on the sustainable road NDP. Specifically, an overview on the three dimensions of sustainable development (i.e., economic, environmental, and social) is first provided, focusing on their representative performance measures relevant to road NDP. Then, we review the existing studies with the classification system of economy and environmentoriented sustainable NDP, economy and equity-oriented sustainable NDP, and three-dimensional sustainable NDP. Future research directions are suggested for advancing the methodological advancement and practical applications of sustainable transportation NDP.

Travel Behavior Analysis using Smart Card Data

Abstract: Electronic fare payment systems have gained much popularity in large public transport systems across the world. Though their main purpose is to collect the revenue and improve passenger’s comfort, they also generate huge amount of detailed and accurate data on onboard transactions which is of extreme importance for transit planners for efficient short-term and long-term transit operation and service planning. This paper attempts to utilize the smart card data as an input for large-scale activity based public transport simulation for analyzing travel behavior pertaining to transit users, using an open source agent-based transport simulation package, MATSim. Transit vehicles are optimized based on input demand generated by smart card and a high temporal resolution of waiting time and its components at different stations is extracted which is very important in managing the frequency and headway of transit vehicles. Since no card swipe is needed for transfers within subway system in Seoul, the data is not readily available to detect frequent transfer locations. However, after validating the boarding and alighting volumes at different stations, a methodology is presented to calculate within subway transfer volumes at different stations. We suggest that by improving the statistical analysis and utilizing advanced data mining techniques, smart cards can effectively generate the microsimulation travel demand models.

Unit Modular In-Fill Construction Method for High-Rise Buildings

Abstract: A modular construction method includes factory-prefabricated room-sized volumetric units. Although low-rise buildings have been constructed worldwide using this method for more than 30 years, it is a relatively new technology in high-rise construction. There are three basic methods of constructing high-rise buildings using modular construction: the core method, the core-and-podium combination method, and the modular in-fill method. While the first two have been used in the USA and in several European countries, the third method, introduced in 2011 by an international cruise ship development firm, is a rather new approach for which there are few case histories. Although the modular in-fill method is being used to construct several dormitories in Korea through public–private partnerships with the Korean government, there have been few applications of this method to construction of high-rise buildings. Therefore, its applicability and construction feasibility should be verified. As a pilot study to test the applicability of the modular in-fill method, a 12-story residential building was built in Korea. This paper describes a case study of the pilot project. The advantages and disadvantages of the method and its applicability in terms of cost effectiveness and construction schedule management were evaluated. The results of this study provide a reference base for advancement of the in-fill method based on an analysis of problems that arose during the construction process for the pilot project.

Theoretical solutions for a circular opening in an elastic–brittle–plastic rock mass incorporating the out-of-plane stress and seepage force

Abstract: Seepage force is simplified as seepage volumetric force in the stress field along the radial direction. Out-of-plane stress and seepage force are incorporated, and the theoretical solutions for stress, displacement, and plastic radius of a circular opening for the elastic-brittle-plastic and elastic-plastic rock mass are proposed based on the Mohr–Coulomb (MC) and generalized Hoek-Brown (HB) failure criteria. The presented solution and Wang’s solution (2012) are compared, and the corrected version of the proposed method is validated. Numerical examples of the proposed method based on the MC and generalized HB failure criteria reveal that the distributions of stress and displacement in the surrounding rock of the tunnel are significantly influenced by seepage force and out-ofplane stress. Displacement and plastic radius when seepage force and out-of-plane stress are considered are larger than those when the seepage force is not considered; the regulations of stress, however, run opposite. The results of displacement and plastic radius based on the generalized HB failure criterion are larger than those based on the MC failure criterion.

A survey on production planning system in construction projects based on Last Planner System

Abstract: Production planning has a critical role in obtaining project success through improving the reliability of workflow. Previous studies have shown the effectiveness of production planning in construction projects. This study aims to examine the current practice of production planning system in Vietnam Construction Industry (VCI) based on the Last Planner System (LPS). An assessment framework for production planning procedures has been employed according to the previous studies. Questionnaire survey, case study and expert survey were employed in this study. The results of analysis have indicated that most of production planning procedures at team workshop step and weekly work plan step in VCI are well performed; whereas most of procedures at lookahead plan step are superficially performed. Master schedule and weekly work plan are the most used plans when executing a construction project. Tool for constraints analysis and tool for measurement of percent plan completed are highly employed. ‘Low understanding of the concepts of LPS’ and ‘language and culture issues’ are the largest and smallest barriers respectively. ‘Indirect cost savings’ is the most beneficial factor if the present barriers are removed. This study then proposed some relevant solutions to enhance the performance of production planning processes in VCI.

The evaluation of three-dimensional effects on slope stability by the strength reduction method

Abstract: The analysis of slope stability problems may often require considerable attention for 3D effects, such as the curvature of the slope, the contribution of the piles and the local loading of the slope by the structures. In this paper, the effect of each contributing factor on the global stability of a 3D slope was carefully and comprehensively investigated by making use of a field case. However, the conclusions drawn from these analyses are not specific to a single case study. Using a couple of hundred analyses that were run within the context of this paper, some guidelines were provided and the influence of each factor on the factor of safety was clearly stated. The results indicated that, the influence of plan curvature can be defined with a unique relationship based on the factor of safety of the slope which is itself directly proportional to the radius of curvature of the slope. Considering the case of local loading on top of the slope, the loading distance and the size of the numerical domain on the shape of the failure mechanism were investigated in this paper and these effects could be demonstrated in the light of the results. Moreover, the influence of piles on slope stability was studied not only for the common “no surcharge case”, but also for different loading conditions in order to optimize the effective pile location. The effect of the pile cross-sectional shape was also discussed in order to optimize the CPU time. Thus, the results of this study are intended to reveal some key issues and bring insight into the design processes.

A synthesis of peak picking method and wavelet packet transform for structural modal identification

Abstract: Damage identification problem involves detection, localization and assessment of the extent of damage in a structure so that the remaining life could be predicted. Visual or nondestructive experimental damage detection methods such as ultrasonic and acoustic emission ones are based on a local evaluation in easily accessible areas, and therefore, they require a certain prior knowledge of the damage distribution. With the purpose of providing global damage detection methods applicable to complex structures, techniques based on modal testing and signal processing constitute a promising approach for damage identification. These methods examine changes in the dynamic characteristics of structure, such as natural frequencies and mode shapes to detect the structural damage. Modal parameters including natural frequencies, mode shapes and damping ratios are known as essential parameters for analyzing the dynamic behavior of a structure. This paper deals with identification of modal parameters of structures using a two-step algorithm. In the proposed method, free vibration response of structure is decomposed using wavelet packet transform. Then, decomposed signal, which has the same energy with the main signal, is used for modal parameter identification using peak picking method. The performance of the proposed method is verified against the results of an experimental benchmark problem.

Integrating sustainability into construction project portfolio management

Abstract: Construction project portfolio management has a large impact on many companies as they are often confronted with having more projects to select from than the resources available to execute them. Selecting the wrong projects will lead to wasted resources and loss of benefits which may have been gained by focussing on other projects. While there have been many discussions surrounding portfolio theory, there is currently a lack of framework which integrates sustainability into construction project portfolio management. This paper departs from existing frameworks (which focus more on monetary gains in projects) by proposing robust methods to account for sustainability across two critical stages: I. Screening; II. Optimal portfolio selection. Under the screening stage, sustainability project criteria are proposed followed by the use of second order moment thinking to account for uncertainty in sustainability measurements. The outputs from the screening stage are then used for developing an efficient frontier which facilitates the selection of an optimal portfolio from a sustainability perspective. The originality of this paper is that it aims to integrate sustainability thinking into construction project portfolio management which has not been attempted.

Damping effects of the passive control devices on structural vibration control: TMD, TLC and TLCD for varying total masses

Abstract: Three passive vibration control devices that consist of a Tuned Mass Damper (TMD), a Tuned Liquid Damper (TLD) and a Tuned Liquid Column Damper (TLCD) are experimentally investigated in this paper. A scaled three-story steel building structure coupled with each device is employed to evaluate the damping effect of each controller. This research experimentally presents that the mass and damping of passive devices are the key factors in structural vibration suppressing. Fast Fourier Transform (FFT), frequency modes and the total mass of devices are used to calculate the Power Spectral Density (PSD) values. As a benchmark, a rigid mass has been attached in the same way on the top floor of the structural model and then the experimental tests are conducted. Results of the comparison between responses of coupled Mass-Structure systems and the control structural systems identify the effects of the mass and damping on the mitigation of structural vibration for each control strategy.

Blasting excavation induced damage of surrounding rock masses in deep-buried tunnels

Abstract: Blasting excavation disturbance is an important influencing factor related to the initiation and the evolution of the surrounding rock damage zone in deep-buried tunnels. Based on the excavation of auxiliary tunnels in the Jinping II Hydropower Station, the effect of blasting excavation disturbance on the surrounding rock damage zone in deep-buried tunnels is studied by means of in-situ rock mass acoustic velocity detection and numerical simulation. The results of the field detections and the numerical analyses show that under the disturbance of blasting excavation, the tunnel surrounding rock Excavation Damage Zone (EDZ) is mainly caused by the in-situ stress redistribution of surrounding rocks after excavation unloading, and the blasting load and the transient unloading of excavation loads are also important factors for the development of the surrounding rock EDZ. The dynamic damage effect caused by the transient unloading of excavation load is more remarkable when the surrounding rock masses under a high in-situ stress.

Triaxial test research on mechanical properties and permeability of sandstone with a single joint filled with gypsum

Abstract: In this study, the mechanical properties and permeability variation in single joint rock samples filled with a gypsum layer were investigated. In order to simulate the inclined infilled joint, the solid cylinders were saw-cut at the dip angles of 90°, 60°, 45°, 30° or 0° with respect to the samples’ axes, and then joined together with gypsum. Triaxial compression experiments with permeability measurements were then performed using these prepared samples. The results indicated that the peak strength and failure modes change with the inclined angles. In comparison with the theoretical analysis of rock with a clean joint, infilling has a marked influence on the mechanical properties to some extent. In regards to the initial permeability, the results showed decreases of approximately two orders of magnitude with the increasing of the prefabricated joint angle, and the initial permeability of the samples with a prefabricated joint were all larger than the intact sample. The evolutionary trends of the permeabilities in triaxial compression in the sandstone samples were shown to be varied with a joint filled with gypsum at different angles, due to the fact that the changes of the inner structure are quite different during the loading process.

Estimation of freight demand at Mumbai Port using regression and time series models

Abstract: Forecasting future freight demand at a seaport is important for its planning and development. India has 13 major ports which handle 75% of the total seaport freight. Among the 13 major ports, Mumbai Port, ranked at number three in the country for the year 2013-14, handles about 11% of the total freight at major seaports in India. The focus of this paper is on developing inbound and outbound demand forecasting models for Mumbai Port. The models are developed using additive regression and time series techniques. In regression analysis economic indicators, Gross Domestic Product (GDP) and Crude Oil Production (CRLP) are found to be significant. The multivariate models performed better than the univariate models. The validation of time-series models resulted in error of less than 5%. Both multivariate regression and time-series models are used to forecast freight demand for the years 2014- 15 through 2017-18. The regression models are producing more optimistic forecasts than the time series models. The elasticity analysis suggested that Mumbai’s inbound freight will be growing almost with India’s GDP growth rate, the outbound freight, however, will experience slower growth than that of inbound.

Numerical modeling of train-induced vibration of nearby multi-story building: A case study

Abstract: In recent years, ground vibration has become a popular research topic due to the growing construction close to vibration sources and the attentiveness of people about living conditions. Thus, vibrations caused by the passage of the train near buildings play an important role. In prediction of train-induced vibrations, many experimental and theoretical methods have been proposed. In order to study the vibration near the railway at Qaemshahr, a 2D finite element analysis employed for modeling of the train movement and its effect on the adjacent building. The validation of the numerical model was done by the high-speed train running measurements. The results show that the vibration level decreases by increasing the track centerline to building distance and decreasing train speed. The frequency of vibration up to 12 Hz was present in the incident wave field and the dominating part of the frequency content was between 2.5 and 5.5 Hz. The building foundation bending moment variations caused by train-induced vibrations was negligible. The track centerline to building edge distance of 18 m was seemed to be an acceptable value to reduce the annoyance and environmental effects caused by train-induced vibrations.

Signal optimization and coordination for bus progression based on MAXBAND

Abstract: A new bandwidth-based approach for bus lane systems is proposed to optimize and coordinate signals and achieve bus progression along urban streets. Elements of the bus systems, such as bus speed, locations of bus stops, and dwell time, were considered to be relevant variables in the proposed approach, which is based on the classic MAXBAND program. First, to establish the bus progression model, intersections along the main street are categorized based on the locations of the bus stops. Second, mixed integer linear programming is employed to construct models that adhere to the following two basic principles: (a) optimizing the bandwidth for each group of intersections and (b) connecting the central lines of green bands for adjacent groups. A software package is then utilized to obtain the global optimal solutions for the model, and a time-space diagram can be created based on the results. Finally, a case study is presented to illustrate the application of the proposed approach. The results show that the proposed approach generates significant improvements in not only the operational performance of the bus lane system but also the average performances of all passengers in the entire traffic system.

Coefficient of restitution and kinetic energy loss of rockfall impacts

Abstract: This paper presents the results of the coefficient of restitution and the kinetic energy loss rate obtained by lab experiment, two parameters that are crucial for rockfall impact. However, various definitions of coefficient of restitution exist and the most appropriate one is still not formed and obtained. In addition, the energy variation during the rockfall impacts has important significance in practical design. In this research, two kind shapes of blocks including plate and strip were adopted in the laboratory testing and the block material was tested before, indicating that the material has sufficient strength to prevent shattering during the impact. Furthermore, an apparatus specifically built for this study was established including a base, a slope and a releasing device. The falling testing was performed using plate and strip block while the falling height as well as the slope angle and releasing height were altered during the tests in order to estimate the effect of each parameter on the coefficients of restitution and energy loss rate. It was observed that collision reflection angle is less than impact angle for all, suggesting energy loss in collision. Impact angle decreases with increasing slope angle while there was no obvious effect of releasing height and releasing angle on impact angle. The relevant coefficient of restitution was found to decrease with impact angle, and the kinetic energy loss rate increased. Finally, the kinetic energy before and after the impact was found to significantly affect the COR and energy loss rate and the results can provide basis for mitigation measures.