فهرست مطالب

Civil Engineering - Volume:17 Issue: 5, May 2019

International Journal of Civil Engineering
Volume:17 Issue: 5, May 2019

  • تاریخ انتشار: 1398/02/21
  • تعداد عناوین: 13
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  • Seismic Evaluation of Tall Unstiffened Steel Plate Shear Wall (SPSW) Systems with Emphasis on Reversal Phenomenon in the Higher Mode Pushover Curve
    Ebrahim Kosari, Mehdi Poursha *, Karim Abedi Pages 523-540
    This paper attempts to study the seismic behavior of tall unstiffened steel plate shear wall (SPSW) systems with an emphasis on the higher-mode pushover analysis and to elaborate the relevant pushover curve. Improved pushover analyses (IPAs) including the modal pushover analysis (MPA) and the modified modal pushover analysis (MMPA) are used for the frames in which the higher-mode effects are substantially important. The conventional pushover analysis using the FEMA load distributions is also implemented. To achieve this goal, mid-rise (10 and 15-story) and high-rise (20 and 30-story) SPSW systems are investigated. To consider a detailed behavior of SPSWs in analyses, a three-dimensional (3D) finite element modeling is used. An interesting result is obtained that the higher-mode pushover analysis results in a reversal in the pushover curve for all of the unstiffened SPSW systems studied in this investigation that this phenomenon is rare in performance-based seismic engineering. The results provide evidence that among the above-mentioned pushover analyses, the MPA procedure is accurate enough for the seismic evaluation of tall SPSW systems. Furthermore, the MPA is computationally time efficient in comparison with the nonlinear response history analysis for this kind of structures with 3D finite element modeling in which there exist a large number of frame and shell elements.
    Keywords: Unstiffened steel plate shear wall (SPSW), Reversal phenomenon, Higher modes effect, Pushover curve, Nonlinear 3D finite element modeling, Modal pushover analysis (MPA), Modified modal pushover analysis (MMPA)
  • Finite Element and Experimental Investigation on the Flexural Response of Pre-tensioned T-Girders
    Mohammad Maghsoudi, Ali Akbar Maghsoudi * Pages 541-553
    A number of analytical and numerical approaches exist for modeling concrete structural members. Finite-element analysis (FEA) is a numerical method that is widely applied to concrete structures based on the use of the nonlinear behavior of materials. The challenge of modeling prestressed concrete structures lies in the treatment of the interface between concrete and prestressing tendons. The FEA-modeling technique discussed in this study is based on general-purpose finite-element packages. This study describes FEA of full-scale high-strength self-compacting concrete, HSSCC pre-tensioned T-girders and its comparison with experimental results. Three 9 m length fully pre-tensioned bridge girders, PHSSCC were designed and cast using HSSCC. The girders were instrumented to monitor deflection, pre-tensioned losses, tendon, steel bar, and concrete strains. The girders were then load tested (until failure), predominantly under flexure, and their service and ultimate results including cracking, flexural stiffness, flexural strength, and different ductility indexes were investigated and compared with FEA results. The software package ABAQUS was used to simulate girders and their bonding conditions to verify the accuracy of FEA. A very good agreement was achieved for numerical and experimental crack patterns. The comparison of finite-element modeling (FEM) and experimental results of load-upward and downward deflections indicated satisfactory agreement throughout the load history of the beams until failure. Comparing FEM and experimental results, reasonable agreement was observed for the two methods of ductility indexes. Finite-element modeling tends to overestimate stress in prestressed tendons at the ultimate state of specimens.
    Keywords: FEA, Pre-tensioned, High-strength self-compacting concrete, Flexural, Ductility, ABAQUS
  • New Form of Equivalent Constitutive Model for Combined Shell Particle Composites and Its Application in Civil Air Defense
    Zhong, bao, YeYong, chi Li, Kai Zhao *, Rui, yuan Huang, Yong, liang Zhang, Xiao, wang Sun Pages 555-561
    In this study, the new combined shell particle composites are designed and manufactured, and simulation-blasting tests are conducted using a new material as the distribution layer of a civil air defense project. Tests show that this type of new distribution layer is highly capable of weakening blasting shock waves. Because of this distribution layer being a complicated, heterogeneous structural material, and numeric simulation of the problem is difficult, even impossible, so we present a new form of equivalent constitutive model to simulate the dynamic behavior of it under blast. The material parameters are optimized by comparing and achieving the best acceptable agreement of the calculated and experimental results, both for the peak stresses and the stress history curves at the same points. Results show that the differences between the calculated peak stresses of the equivalent constitutive model and test results are less than 8%. The stress history curves for calculated and experimental results are of similar evolution characteristics. The numerical simulation results of the stress pulsewidth at three measured points are relatively close to the experimental ones, and the calculated mean stresses at three measured points are also close to the experimental ones, the errors are about 10%. Therefore, for the purpose of engineering application our equivalent constitutive model might be seen an acceptable model.
    Keywords: Shell particle composites, Equivalent constitutive model, Experimental research, Numerical calculation, Optimize material parameters
  • Fire Structural Response of the Plasco Building: A Preliminary Investigation Report
    Behrouz Behnam * Pages 563-580
    The fire-induced collapse of the 16-story Plasco building in Tehran city in January 2017 caused many deaths and serious injuries. This paper investigates the structural response of the building during that fire to understand how the building became unstable. As documented, the fire initiated on the tenth floor, and then involved stories 11–14 through a vertically traveling fire. As the occupancy type of the building had changed over time, the analysis was performed based on an estimated fire load density of 1900 MJ/m2 on the day of the catastrophe. The results showed that the structure was able to resist the applied loads when the fire remained within stories 10 and 11. When the fire involved stories 10–14, however, the structure began to fail, starting with the failure of the ceiling trusses. The results also indicated that as the columns were protected by a layer of masonry, they were able to tolerate their applied loads. The analysis was also re-performed based on a fire load density of 511 MJ/m2, which is the fire load recommended by most fire codes for a similar occupancy type. The results showed that no structural failure would have occurred under that fire load. This study indicates that changing the occupancy type of a building without adopting proper mitigation strategies can be catastrophic.
    Keywords: Plasco building, Structural fire, Thermal analysis, Fire load, Structural collapse
  • Influence of Abutment Slope Angle Variety on the Deformation and Stress of the Concrete-Faced Rockfill Dam During Initial Impoundment
    Ruihu Song, Junrui Chai*, Zengguang Xu, Yuan Qin, Jing Cao Pages 581-595
    Favorable valley terrain for building dams is gradually decreasing. The primary objective of this study is to investigate the influence of abutment slope angle variety on the deformation and stress of concrete-faced rockfill dam (CFRD). First, the effect of abutment slope angle on perimeter joint deformation is investigated using CFRD monitoring data in China. A normalized deformation index (CDS) is proposed to evaluate the relationship between perimeter joint deformation and the steepest abutment slope angle. Results indicate that perimeter joint deformation increases nonlinearly with the steepest abutment slope angle. Then, numerical analysis is conducted on Miaojiaba CFRD under three types of abutment slope variety from upstream to downstream. We focus on the effect of abutment slope angle variety from upstream to downstream on CFRD behavior. In the analysis, the terrain shape line is assumed to be constant at the downstream slope foot, and the abutment slope angle increases linearly from upstream to downstream. The Duncan–Chang E–B model is used in nonlinear analysis for rockfill, and the slab–rockfill interfaces are modeled using contact elements with Coulomb friction. An influence sphere is proposed for the different types of abutment slope angles. Results indicate that face slab deformation is more dependent on abutment slope angle than rockfill deformation.
    Keywords: Valley terrain, Abutment slope angle, Concrete-faced rockfill dam, Deformation Stress
  • Predicting the Shear Behavior of Reinforced Concrete Beams Using Non-linear Fracture Mechanics
    Vahid Broujerdian*, Hossein Karimpour, Sobhan Alavikia Pages 597-605
    This paper deals with the challenging problem of predicting the load carrying capacity of reinforced concrete shear-critical beams. To simulate the cracking behavior of concrete, the discrete crack approach based upon non-linear fracture mechanics is used. An algorithm with two pathways of implementation has been proposed so as to implement fictitious crack model to analyze reinforced concrete beams using finite-element method. The merit of the proposed algorithm is its capability to recognize and to incorporate them in the analysis procedure. The proposed method is capable of predicting simultaneous multiple shear cracks, load-deformation behavior, and ultimate shear capacity of reinforced concrete beam. The obtained results show a good compliance with the available experimental benchmark studies on reinforced concrete beams failed in shear. As one of the important aspects of shear capacity is the size effect issue, some large-scaled test beams have been numerically simulated using the proposed algorithm and the results have been compared with that of ACI 318-11 building code as well as the well-known modified compression field theory (MCFT). The comparison corroborated the robustness of the proposed algorithm in detecting the well-known shear-scaling phenomenon. In the same time, the comparison emphasized on the weakness of the current codes of practice to overestimate the shear capacity of large-scaled beams owing to not taking the size effect into account.
    Keywords: Reinforced concrete, Beam, Shear, Fictitious crack model, Finite element
  • Flow Pattern Around Attractive, Vertical, and Repelling T-Shaped Spur Dikes in a Mild Bend Using CFD Modeling
    Mohammad Vaghefi *, Parisa Radan, Maryam Akbari Pages 607-617
    This piece of research presents flow pattern around a T-shaped spur dike in repelling, attractive, and vertical positions in a 90° mild. To this aim, SSIIM CFD software, one of the most powerful software applications in hydraulic engineering field, was employed. In this research, Navier–Stokes equations and k–ε turbulent model were used for solving the flow field. The numerical results were verified using the experimental data. The comparison between the results of numerical simulation and experimental data collected by ADV velocimeter indicated a desirable agreement. The numerical results showed that the dimensions of the vortex at the downstream side of the spur dike reduced by increasing the angle of the spur dike. Moreover, the secondary flow strength value was the maximum for attractive and then repelling modes. Variation of the secondary flow strength for repelling, attractive, and vertical modes ranged from zero to 45, 35, and 25% respectively. Although the range of the secondary flow values in vertical mode for both numerical and experimental models was identical and about 0–25%, less than a 5% error between these two models demonstrated that the amount had been reasonable. By determination of flow separation zones, it was observed that, for all the three modes, the separation zone length increased by increasing the elevation. In addition, the lengths of the separation and reattachment zones were equal to 1.2–2.7 and 1.57–4.18 times the spur dike wing length.
    Keywords: T-shaped spur dike, Attractive, repelling spur dikes, 90° bend, Flow pattern, Numerical model, SSIIM
  • Discharge Characteristics Analysis of Queued-up Vehicles at Signal-Controlled Intersections Under Heterogeneous Traffic Conditions
    Satyajit Mondal, Ankit Gupta * Pages 619-628
    Characteristics of discharge vehicle play a significant role in the concept of capacity estimation and designing of a signal-controlled intersection. Highway Capacity Manual (HCM) (Transportation Research Board of the National Academics, 5th edn, Washington, DC, 2000) presents a methodology for analysing signalized intersection considering details of each parameter for a lane-based car-dominated traffic stream, with limited applicability for the mixed traffic conditions. The present study analyses the departure headway characteristics of queued vehicles where a decreasing trend is observed with increase in vehicle position with a saturation headway of 2.05 s/veh. The distributions of departure headways are also analysed, and hypothesis result shows that the departure headways at each vehicle position follow a particular log-normal distribution with varying mean and variance. An optimization technique is framed to find out the discharge of vehicles through minimizing the difference between observed flow and ideal flow proposed by HCM (2000). Dynamic passenger car units (PCU) are also estimated through minimizing the Theil’s coefficient for accurate estimation of discharge pattern for mixed traffic conditions. The result shows that optimized discharge pattern is close to the ideal one with maximum saturation flow of 1908 PCUs/h (HCM proposed 1900 PCUs/h). A comparative analysis is done between the obtained flow value and flow value proposed by several guidelines and studies to check its suitability for mixed traffic stream.
    Keywords: Departure headway, Discharge rate, Mixed traffic, Passenger car unit, Signalized intersection
  • Theoretical and Experimental Study on the Bond–Slip Relationship in Prestressed CFST Beams
    Yulin Zhan*, Lei Zhang, Renda Zhao, Qiang Zhang, Zengqiang Duan, Jiale He Pages 629-643
    Concrete-filled steel tube (CFST) beams are widely used in civil engineering, especially for bridges and tall buildings, because of their strength, stiffness and durability. Good bonding at their interface is essential for ensuring that steel and concrete can work well together. However, if interfacial slippage does occur it not only hinders the plasticity of a beam’s performance in full section but also weakens its strength and stiffness. To study the mechanism of slip occurrence and its impact, eight prestressed CFST rectangular beams were tested under monotonic loading. Slippage was measured during the entire loading procedure. Based on the elasto-plastic theory, a nonlinear finite element model, considering slippage is developed in this paper. The results show that slippage occurred when the concrete began to crack. This plays an important role in the overall performance of a beam after the steel has yielded. The maximum slip occurred near the section of quarter-span. To some extent, the slip curves generated by this model agreed with the test results, and it could be used to predict the bending capacity of prestressed CFST beams.
    Keywords: Prestressed concrete-filled steel tubes, Finite element model, Bond-slip relationship
  • An Improved Test for Generating Rapid, Accurate, and Reliable Crack Permeability Data for Cementitious Materials
    Damian Palin *, Yu Mo, Virginie Wiktor, Henk Marius Jonkers Pages 645-652
    Presented is a modified test for generating crack permeability data for cementitious materials. Single-parallel cracks were generated in mortar specimens. The width of the cracks was analysed through stereomicroscope and computer tomography, and the water permeability of the cracks was determined. Reduction factors and crack flow models were generated, and the reliability of those predictions was assessed. Cracks analysed through stereomicroscope produced reliable crack permeability predictions (r2 = 0.97–0.98), highlighting the importance of testing multiple (≥ 7) replicates. The modified test produced accurate cracks (i.e., cracks that were within 20 µm of their desired crack width) and was easy to use allowing rapid permeability data (i.e., 10 h for 21 specimens) to be generated. The modified test will be of great use for those wanting to generate rapid, accurate, and reliable crack permeability data for cementitious materials.
    Keywords: Cementitious materials, Microcracking, Defined crack widths, Water permeability, Reliability Durability
  • Erratum to: Passive Methods for the Fast Seismic Characterization of Structures: The Case of Silea Bridge
    Otello Bergamo *, Massimiliano Pignat, Carmine Puca Page 653
  • Erratum to: Comparative Numerical Research on the Seismic Behavior of RC Frames Using Normal and High-Strength Reinforcement
    X. L. Chen, J. P. Fu*, F. Xue, X. F. Wang Page 655
  • RETRACTED ARTICLE: Assessment of Pedestrian Refuge Islands on Vehicle Speed Changes and Pedestrian Safety: Case Study in Tehran
    Arash Sadrayi, Mahmoud Saffarzadeh*, Amin Mirza Boroujerdian Page 657
    The authors have retracted this article (1) due to significant overlap with previously published articles by the same authors (1, 2). All authors agree to this retraction. The online version of this article contains the full text of the retracted article as electronic supplementary material. 1) Arash Sadrayi, Mahmoud Saffarzadeh, Amin Mirza Boroujerdian, Assessment of Pedestrian Refuge Islands on Vehicle Speed Changes and Pedestrian Safety: Case Study in Tehran, International Journal of Civil Engineering 2) Arash Sadrayi and Amin Mirza Boroujerdian, Assessment of Pedestrian Refuge Islands on Vehicle Speed Changes and Pedestrian Safety: Case Study in Tehran, Journal of Traffick and Logistics 3) Arash Sadrayi; Mahmoud Saffarzadeh; Amin Mirza Boroujerdian, An Assessment of the Impact of Pedestrian Refuge Islands on Vehicle Speed Changes and Pedestrian Safety: Case Study in Tehran International Journal of Transportation Engineering.