فهرست مطالب

Civil Engineering - Volume:16 Issue:8, 2018
  • Volume:16 Issue:8, 2018
  • تاریخ انتشار: 1397/05/10
  • تعداد عناوین: 10
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  • Indexing Crash Worthiness, Crash Aggressivity, and Total Secondary Safety for Major Car Brands: A Case Study of Iran
    Ali Tavakoli Kashani *, Hessam Arefkhani Pages 857-869
    A growing body of research is being conducted all over the world to evaluate and compare the safety impacts of different car brands. This issue has also received a considerable attention among the safety experts in Iran, where the number of road fatalities is around 16,500 lives per year. This study aims at indexing crash worthiness, crash aggressivity, and total secondary safety of the 20 most prevalently used passenger car brands of Iranian fleet. For this purpose, the data pertaining to 167,759 crashes and 335,518 drivers involved in those crashes that occurred in Iran from 2009 to 2012 were used. Binomial logistic regression model was applied to define the above-mentioned indices based on driver’s injury severity level. The results showed that most of the domestic brands have a poorer performance than the foreign ones in all three indices. Furthermore, it was revealed that Kia and Suzuki have a better performance and Sepand and Pride have a poorer performance compared to the other brands. Our findings might also be integrated with the findings of other similar studies around the world. This could be helpful for car manufacturers both in Iran and across the world to benchmark the best performing car brand in vehicle safety domain and improve the designing of their own car brands.
    Keywords: Crash worthiness, Crash aggressivity, Total secondary safety, Car brand, Iran, Driver's injury severity
  • Semi-Active Control of Structures Equipped With MR Dampers Based on Uniform Deformation Theory
    Reza Karami Mohammadi *, Samin Najarzade Pages 871-885
    Optimization based on uniform deformation theory (UDT) was proposed as a new technique in the field of optimum design of structures. In this paper, the concept of UDT has been utilized for semi-active control of buildings equipped with magneto-rheological (MR) dampers. Based on UDT, a method for determining the optimum control voltage using a polynomial controller has been presented. The coefficients of the polynomial controller have been determined by minimizing the standard deviation of the maximum inter-story drifts of a structure and by utilizing the Particle Swarm Optimization (PSO) algorithm. The proposed controller based on UDT has been applied to control three- and six-story nonlinear shear buildings subjected to various earthquakes. The performance of this controller was evaluated regarding the uniform distribution of the maximum inter-story drifts and the reduction of the structural responses. Using this method, the maximum inter-story drifts of the structures were remarkably uniform in comparison to the uncontrolled structures. In addition, the maximum structural responses, especially the maximum inter-story drifts of the structures, significantly decreased.
    Keywords: Semi, active control, Magneto, rheological damper, Uniform deformation theory, Polynomial controller, Particle swarm optimization
  • Experimental Study on the Long-Term Behaviour of RBPC T-Beams
    Guohui Cao *, Wang Zhang, Jiaxing Hu, Kai Zhang Pages 887-895
    This study compares the mechanical properties of the retard-bonded and conventionally bonded prestressed concrete (RBPC and BPC, respectively) under uniform loads. Results show that the prestressed strands and concrete of the RBPC T-beams are firmly bonded with harden of retard-bonded materials, thereby exhibiting the same mechanical properties as that of the BPC beams. The growth rate of the long-term deflections of the RBPC T-beam is slightly lower than that of the BPC T-beam. Given the effect of concrete shrinkage, creep and time variation of prestress loss, the regular patterns of deflection growth of the RBPC T-beam mid-spans are analysed based on the age-adjusted effective modulus method, method of equivalent prestress load and calculation model of prestress loss. Accordingly, the long-term deflection development curves of the RBPC T-beam mid-spans under self-weight, prestressing force and external loads are obtained. Calculation results are in good agreement with the test results. This method has immense applicability for the computation of the RBPC T-beams, and can be used to estimate the long-term deflection growth of regular patterns of the RBPC components.
    Keywords: Retard, bonded, Prestressed concrete, Beams, girders, Deflection, Creep
  • The Effect of Alkaline Solution-to-Slag Ratio on Permeability of Alkali Activated Slag Concrete
    Kiachehr Behfarnia *, Majid Rostami Pages 897-904
    This study investigated the effect of alkaline solution-to-slag ratio on permeability of Alkali Activated Slag Concrete (AASC). Permeability of concrete has a direct impact on its durability, so, in this study, a series of tests were arranged to examine the effect of alkaline solution-to-slag ratio on water impermeability, chloride permeability, short-term and total water absorption, and compressive strength of AASC specimens. In experimental study, four concrete mixes with alkaline solution-to-slag ratios of 0.4, 0.45, 0.50, and 0.55 were considered. One mix made by ordinary Portland cement was also considered for comparison of the results. In general, AASC outperformed the Portland cement concrete. In addition, the results showed that the alkaline solution/slag ratios of 0.45 are the optimum value for AASC mixes from the durability and permeability point of view. Based on the results, there is only a slight difference between short-term water absorption and total water absorption of AASC samples.
    Keywords: Alkali activated concrete, Chloride, Water impermeability, Water absorption, Alkaline solution, to, slag ratio
  • Impact of Two Connection Types on the Behavior and Losses of a Steel Hotel Building Under Strong Winds in Mexico
    David De Leon *, Gerardo Lazcano Pages 905-916
    Two connection types are examined under a life-cycle point of view, for a regular framed steel hotel building located in Mexico under a strong wind hazard, to compare their cost-effectiveness and provide practical recommendations. Although FEMA has fragility curves for housing facilities under strong winds, there are no curves for medium height or tall buildings like the one used to illustrate the formulation. The critical connections were identified through a series of preliminary analyses of the ten stories building, which were performed under scenario wind velocities, and a detailed finite-element model was used to evaluate the connection limit state and the failure probability at both levels: the connection and the overall building. The cost-effectiveness of bolted and welded connections was examined, as alternative designs, through the calculation of the expected life-cycle cost. Envelope damages are explicitly considered as façade components and windows are usually damaged and cause important losses. In addition, the potential loss of contents is assessed as a consequence of water infiltration after the building envelope is damaged, and the expected business interruption losses, from the repairs required, are included in the cost analysis. The correlation coefficient between wind velocity and rainfall intensity, given the occurrence of a hurricane, is calculated and incorporated on the simulation of rainfall intensity. Recommendations to mitigate losses are proposed in terms of the fragilities found and the cost of mitigation measures. It is shown that low-cost improvements, on the façade and windows anchorage conditions, strongly reduce the expected losses and the cost–benefit of these measures decreases as the building importance increases.
    Keywords: Steel connection types, Expected life, cycle cost, Wind hazard, Water infiltration, Fragility curves
  • Fragility Curves of Regular and Irregular Moment-Resisting Concrete and Steel Frames
    Fadzli Mohamed Nazri *, Chee Ghuan Tan, Siti Nur Aqilah Saruddin Pages 917-927
    This study presents the fragility curves of regular and irregular moment-resisting frames using different heights, materials, and ground motion records. The concrete and steel frames used in this study differed in terms of height, namely, 3, 6, and 9 stories. Each type of frame was designed based on Eurocode 2 and Eurocode 3 with the aid of Eurocode 8 for earthquake loading. Incremental dynamic analysis (IDA) was conducted for the three selected ground motion records using SAP2000 software as the main tool. The IDA curves were compared to the five levels of the limit state of FEMA 356: operational phase (OP), immediate occupancy, damage control, life safety, and collapse prevention (CP). Based on the analysis of fragility curves, irregular frames exhibited a higher probability of reaching OP and CP levels compared with regular frames.
    Keywords: Regular frame, Irregular frame, Incremental dynamic analysis (IDA), Limit state, Fragility curve
  • Sefficiency of a Water Use System: The Case of Kano River Irrigation Project, Nigeria
    Muhammad Tajuri Ahmad, Naim Haie *, Haw Yen, Nasser A. S. Tuqan Pages 929-939
    Northern Nigeria is part of the semi-arid region of Africa experiencing water scarcity. The ever increasing population and climate change have placed a considerable pressure on Kano River Irrigation Project (KRIP), a major water user on Kano River, the most upstream tributary of Yobe River flowing directly to Lake Chad which is an important transboundary basin in West Africa. Performance of KRIP was evaluated using meso-level of the new and innovative Sefficiency (sustainable efficiency) framework, which incorporates quantity, quality, and beneficial aspects of water use in a comprehensive and systemic manner. Two major stakeholders were contacted, namely, farmers and water managers, and their views on the value of water flows were registered through interviews. The results indicated that useful consumption relative to effective consumption of farmers is significantly lower than management, showing a higher relative consumptive impact on both KRIP and Kano River. In addition, the useful outflow per unit of useful inflow is lower according to the farmers relative to the managers. Water managers underscore the importance of pollution impacts, give relevance in allocating water to downstream users including environmental flows, and contributing to groundwater recharge, whereas farmers do not. Flawed classical efficiency in use globally gives much lower values than meso-efficiency. For proper policy analysis in KRIP, the paper recommends using meso-efficiency with technologies to derive better data and to educate farmers on the importance of pollution and return flow.
    Keywords: Water management, planning, Irrigation management, Nigeria, Sefficiency (sustainable efficiency), Stakeholder participation, Downstream impacts, Tiga dam
  • Bi-stakeholder Conflict Resolution-Based Layout of Construction Temporary Facilities in Large-Scale Construction Projects
    Xiaoling Song *, Zhe Zhang, Jiuping Xu, Ziqiang Zeng, Charles Shen, Feniosky Pe, Ntilde, A-Mora Pages 941-964
    Planning a layout of construction temporary facilities (CTFs), a specific construction site layout problem, is crucial to the successful completion of large-scale construction projects. Despite considerable research undertaken, mutual relationships and conflicts between the layout planner and other pre-planning task stakeholders (i.e., for the scheduling of construction activities or the material purchase) are not yet addressed in the layout process. Resolving conflicts is crucial to the layout optimization and this study is among the first to plan appropriate CTF layouts by taking bi-stakeholder conflict resolution into account. A new bi-level mathematical method is developed based on the resolution of conflicts between the CTF layout planner and the material purchase stakeholder, and thus providing an example for future layouts with bi-stakeholder conflicts. In this method, a bi-level programming model is first established to model layout-related goals, constraints, and conflicts. Second, a bi-level genetic algorithm is proposed to solve the model for appropriate layouts. To demonstrate the applicability of the proposed method, the method is applied to design a CTF layout for the construction of a practical dam project. The results demonstrated that an appropriate layout and a satisfactory purchase plan were determined, and conflicts between the CTF layout and the material purchase were prevented. The contributions of the method are the ability to capture the mutual conflicts of the CTF layout and the material purchase in the bi-level model, the capacity to develop a more efficient and realistic layout, and the practicality to guide planners in other situations.
    Keywords: Layout of CTFs, Material purchase, Layout planner, Stakeholder, Conflict resolution
  • Effects of High Temperature on Mechanical Properties of Polyvinyl Alcohol Engineered Cementitious Composites (PVA-ECC)
    Qiang Du *, Jing Wei, Jing Lv Pages 965-972
    The influence of elevated temperatures on the mechanical properties of polyvinyl alcohol engineered cementitious composites (PVA-ECCs) was investigated in this study. A comparison of the compressive strength, flexural strength, compressive strain capacity, and modulus of elasticity of specimens with/without PVA fiber (volume dosage of PVA fiber: 2%) was conducted. The microstructure of PVA-ECC exposed to different high temperatures was studied using scanning electron microscopy (SEM). Based on previous thermal analysis tests of PVA fibers, all specimens were subjected to 20, 100, 200, 300, and 400 °C for 6 h. The experimental results showed that the compressive strength, flexural strength, and modulus of elasticity decreased as the temperature increased, whereas the compressive strain capacity increased with temperature. PVA incorporation significantly increased the flexural strength initially but accelerated the rate of strength reduction at high temperatures. The investigation of the PVA-ECC microstructure provides a fundamental reason for the decrease in the macro-mechanical properties. These findings provide guidance for the engineering applications of PVA-ECC to resist high temperatures.
    Keywords: High temperature, PVA, ECC, Mechanical properties, Microstructure
  • Mix Design and Recycled Aggregates Effects on the Concrete's Properties
    Safiullah Omary, Elhem Ghorbel *, George Wardeh, Minh Duc Nguyen Pages 973-992
    An experimental program was carried out to study the properties of concretes with C25/30 and C35/45 resistance classes designed using natural aggregates and recycled ones provided from construction and demolition waste (C&DW). Eight mixtures were prepared with different incorporation ratios of fine and coarse recycled aggregates. The physical and mechanical characteristics were measured and their evolution regarding to the paste volume, the equivalent replacement ratio and the quality of the interface between recycled aggregates and new paste has been investigated. Scanning Electron Microscopic observations have revealed a good quality of the interface. It was found that water porosity is more dependent on the equivalent replacement ratio than on the volume of the new paste. The same conclusions are reported for the electrical resistivity which has been related to the water porosity. Based on experimental results, it has been found that the Archie’s law predicts the electrical resistivity as a function of water porosity for all type of concrete. The effect of mix design parameters and aggregates properties on the compressive strength has been investigated and a model is proposed on the basis of Féret’s expression through experimental results and data points available in the literature. The modified expression is related to the aggregate fragmentation resistance expressed by the Los Angeles coefficient (LA). The Féret’s coefficient can be taken equal to 6.4 if LA ≤ 20% and it is inversely proportional to LA otherwise. With regard to the splitting tensile strength, it can be correlated to the electrical resistivity through a power law relationship. The elastic modulus, the peak and the ultimate strains are than rewritten as functions of the compressive strength and the replacement ratio to model the full stress–strain curve under uniaxial compression. Furthermore, the validity of using EC2 to model the evolution of all mechanical properties with age is ensured.
    Keywords: Concrete, Recycled aggregates, Mechanical properties, Porosity, Electrical resistivity