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Rehabilitation in Civil Engineering - Volume:12 Issue: 1, Winter 2024

Journal of Rehabilitation in Civil Engineering
Volume:12 Issue: 1, Winter 2024

  • تاریخ انتشار: 1402/06/20
  • تعداد عناوین: 9
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  • Effect of wind loading pattern on shear lag phenomenon in framed-Tube Building
    Ashish Singh *, Sasankasekhar Mandal, Piyush Gaikwad Page 2

    High-rise tubular buildings experience the shear lag phenomenon due to wind load. This phenomenon results in tension in upper storey columns that may adversely affect building stability. Shear lag varies with many factors such as building layout, outer peripheral columns spacing, and load applied to the building. Therefore, it is essential to accurately analyze the shear lag phenomenon by considering these factors, especially, with due emphasize on the pattern of the applied wind loading. This paper attempts to study the effect of wind loading pattern on the shear lag phenomenon. Six load cases are taken from American and Canadian codes to analyze the wind load effects on a 40-storeyed tubular building. The results indicate that axial force distribution changes significantly with change in the loading patterns of the building. A difference in axial force distribution is observed between torsional and non-torsional load cases. Axial force in columns in the case of uniform loading is more significant as compared to partial loading cases. Due to loading on half of the face, axial force distribution becomes unsymmetrical, and a minimum axial force in corner columns is observed. Also, notable differences can be seen in the axial force distribution of load cases having both direction loadings compared to single direction loadings. Axial force distributions in cases of both face loading are unsymmetrical for the central column.

    Keywords: Codal provisions, Framed tube, Shear lag phenomenon, Torsional Wind load, Wind loading
  • A Simple Solution for Estimating the Smear Effect Permeability Ratio using Finite Element Method
    Rufaizal Che Mamat *, Azuin Ramli Page 3

    The installation of a vertical drains system beneath the embankment results in enhanced soil consolidation in soft soil. This article explores the behaviour of soft soil stabilized with prefabricated vertical drains (PVDs) beneath embankments through finite element analysis. A multi-drain analysis, which varied the smear effect permeability ratio using both equivalent and plane strain models, was performed. Back-calculation of the permeability ratio of the smear effect is employed to adjust the model parameters. The analytical formulation employed the Cam-clay concept in combination with the smear effects. The study revealed that PVDs installation in the soft soil beneath the embankment increased the settlement rate and improved pore water pressure dissipation. Accurate prediction requires the estimation of the equivalent horizontal permeability using appropriate values of the smear effect permeability ratio. Incorporating the smear effect into the numerical analysis of vertical drains improved prediction accuracy. The article proposes a new approach for estimating the smear effect permeability ratio for soft soil stabilized with PVDs.

    Keywords: Soft soil, Smear zone, Road embankment, Prefabricated vertical drains, finite element method
  • Biaxial loading capacity of H-type reinforced concrete electric poles
    Abolfazl Eslami *, Moein Ramezanpour, Ehsan Hematpoury Farokhy, Mohammad Dehghani Sanij Page 5

    H-type reinforced concrete poles are nowadays widely used as an economical and cost-effective substitute for wooden poles in power transmission lines. Although these poles are frequently subjected to biaxial loading in real field application, their biaxial interaction curves yet await detailed investigation. The current study was aimed at developing the biaxial bending interaction curves for H-type utility poles considering the measurements stipulated by the relevant standards and codes. Towards this, two commonly used H-type electric poles (i.e., 9 and 12 m ones with a normal strength of 400 kgF) were constructed, cured, and loaded at angles of 0, 30, 60, and 90 degrees with respect to their minor principal axes. The experimental results were described in terms of load-displacement curves, developed strains, cracking pattern, failure modes, and biaxial loading interaction curve. The obtained interaction diagrams can be reliably used to estimate the loading capacity of electric poles under biaxial loading in real field applications.

    Keywords: H-type pole, Reinforced Concrete, Loading capacity, Bi-axial bending, Interaction curve
  • An Experimental Study on Bond Behavior of Rebar and High-Performance Fiber Reinforced Cementitious Composite (HPFRCC) at High Temperatures
    Salim Karimpour, Rahmat Madandous, Malek Mohammad Ranjbar *, Habib Akbarzadeh Bengar Page 6

    In this work, it was attempted to explore the bond behavior of rebars in high-performance fiber-reinforced cementitious composite (HPFRCC) consisting of hybrid fibers with 1 and 2% by weight of binder for steel and 0.1, 0.2, 0.3, and 0.4% by weight of binder for polypropylene (PP) and polyvinyl alcohol (PVA) fibers along with the compressive and tensile strengths after exposure to high temperature. From 19 mix designs, four superior ones which experienced lower reduction in compressive strength at 400 and 600 oC was selected in order to investigate the bond behavior of rebar in HPFRCC specimens using direct pullout and RILEM beam tests. The experimental results revealed that the HPFRCC specimens with 1% steel fiber combined with 0.2% PP fiber and 0.3% PVA fiber, separately, had the minimum compressive strength loss at 400 and 600 °C. For the HPFRCC with 2% steel fiber, the higher compressive strength at the given temperatures was observed for those with 0.3% PP and 0.2% PVA fiber, separately. The specimens with higher compressive strength at the given temperatures were those that had 2% steel fibers, 0.3% PP, and 0.2% PVA fibers. The specimen with 1% steel fibers and 0.3% polypropylene fibers had a greater tensile strength with a value of 14.2 MPa compared to other specimens. Furthermore, the bond capacity of rebar in HPFRCC continues to decline with temperature rise up to 600 °C to the point where this reduction for the chosen specimens is approximately 62% of the bond strength of the specimens at the room temperature (i.e., 23 °C). The maximum pull-out force has a significant relationship with the type and proportion of fibers, as demonstrated by the RILEM beam's results. Compared to specimens containing PP fibers, those with PVA fibers at high temperatures were able to tolerate higher bond strength.

    Keywords: Bond behavior, HPFRCC, PVA fibre, RILEM test, Pullout Test
  • Numerical Study of Concentric Brace Equipped with the Eccentric Fuse for Strengthening Buildings.
    Mohammad Ali Kafi *, Asadullah Attal Page 7

    Concentric bracing with ease of design and execution and low construction cost represents the widely used system for resisting the structures to lateral forces. The diverse lateral load-bearing system has a variety of types, characterized by its main performance properties as bearing capacity, stiffness, performance ductility, and energy dissipation. Studies revealed that the brace system is a valuable option for retrofitting existing steel and reinforced concrete structures. However, the bracing system suffers a weakness called axial buckling of the brace under critical compressive load, reducing bearing capacity and interrupting energy dissipation. To address this imperfection and induce the seismic response of the concentrically braced frames, several methods proposed to optimize the performance of concentric braces as; using ductile connections, incorporating shear dissipators, hydraulic or mechanical dampers, frictional dissipators, and restrained braces to avoid buckling. Therefore, in this study, an innovative geometry of brace-to-frame connection is investigated to enhance the concentric brace's performance. The local dissipative fuse system is used to connect the steel channels with the gusset plate at one or both ends and at the time of the earthquake the dissipator yields before the brace buckles and forms a flexible plastic hinge, consuming a significant amount of earthquake energy. Similar studies have been performed earlier but the valuable tensional capacity of the braces was affected. Thus, the innovative method aims to maintain the tensional capacity of the brace in addition to buckling prevention and energy dissipation. Also, the dissipators have a post-earthquake ability to easily provide and replace. Consequently, the numerical work performed in this study effectively prevents buckling, and enhanced energy dissipation while maintaining the full tensional functionality of the brace.

    Keywords: ductility, Buckling, Energy Dissipation, Seismic response, Off-axial innovative connection
  • Numerical study of the effect of transverse reinforcement on compressive strength and load-bearing capacity of elliptical CFDST columns
    Ali Mohammed Ali *, Sima Besharat Ferdosi, Laith Kareem Obeas, Alwaleed Khalid Ghalib, Meisam Porbashiri Page 8

    During this research, the buckling behavior of elliptical CDFST columns is investigated numerically in Abaqus Software using transverse reinforcements in the outer tube of the column. For this purpose, an elliptical CFDST column is simulated in Abaqus Software and it is subjected to compressive loading. The transverse reinforcements are validated and placed in the outer tube of the elliptical CFDST column, and parameters such as thickness, reinforcement dimensions and distance between them vary within the range of 4, 6, 8 mm; 2, 4, 6 cm and 2, 4 and 6 cm, respectively and a total of 27 models will be analyzed during the research. The results obtained from this study are in good agreement with the results of previous studies and showed that the finite element method can provide accurate behavior of these columns. The results of this study showed a 15 to 40% increase in load-bearing capacity with the highest compressive strength in elliptical CFDST columns using transverse reinforcements. Also, the effect of increasing the thickness and dimensions on load-bearing enhances by 20% and 15%, respectively while the effect of increasing distance between transverse reinforcements reduces the bearing capacity by 10%. The maximum axial strength was observed in CFDST columns with transverse reinforcements.

    Keywords: CFSDT column, Buckling behavior, Abaqus software, Elliptical column, Transverse reinforcement
  • Structural damage identification through an optimal sensor placement approach and the modal strain energy-based index
    Seyed Mohammad Seyedpoor *, Reza Yahyapour, Ali Asghar Mofdi, Saeed Fallahian Page 9

    In this study, an efficient method for determining the accurate location of damage to structures is introduced using an optimal sensor placement (OSP) and modal strain energy-based index (MSEBI). The research is implemented in two main stages. In the first stage, a correlation function between the reconstructed mode shapes using the iterated improved reduced system (IRS) method and the complete mode shapes of a structure is defined and then the function is minimized via the binary differential evolution (BDE) algorithm to find the optimal sensor placement of the structure. In the second stage, the location of damage is determined using MSEBI based on the optimum place of sensors obtained already. In order to assess the efficiency of the proposed method, two standard examples, including a two-dimensional (2-D) frame structure with 45 elements and a 2-D truss with 47 elements, are examined. Numerical results, considering different conditions, demonstrate that the integration of OSP method and MSEBI can provide an efficient tool for accurate and rapid identification of the damage location. The parametric study shows that the proposed method has a low sensitivity to the number of modes and noise level, and it can properly identify damage by considering a few modes and the high level of noise.

    Keywords: Damage identification, optimal sensor placement, Modal strain energy, iterated improved reduced system
  • Presenting a Statistical Model of Fatigue Prediction for the Effect of Loading Frequency on Reflective Cracks Propagation on Asphalt Layers Improved by Geosynthetics
    Saeid Asadi, Gholamali Shafabakhsh * Pages 18-33

    So far, several methods have been proposed for delaying the reflective cracks in pavements. Despite substantial money spent annually on these types of maintenance methods to control reflection cracking in road pavement, none of them has successfully prevented such damage and only delayed crack propagation in improved asphalt overlays. However, some of these methods have been more effective in preventing the initiation of reflective cracks and reducing the severity of their damage in restored pavements. One of the best methods to deal with this issue is using geosynthetic products. The present study investigates the performance of two different types of geocomposites in the reinforcement of asphalt overlays in delaying reflective cracks compared to control samples. To this end, laboratory and statistical studies were performed at different temperatures and loading frequencies. The results showed that using type-I geocomposite will be most effective in increasing fatigue life. On the other hand, among the mentioned factors, the temperature rise will have the most negative effect on the fatigue performance of geocomposite layers in asphalt overlays. Finally, a high-accuracy statistical model of fatigue life based on temperature, frequency, and geocomposite type is presented (i.e., R² and Adjusted R² of 0.987 and 0.981, respectively).

    Keywords: Reflection cracking, Geocomposite, Temperature, Loading frequency, Fatigue, Statistical analysis
  • Effect of Near-Fault Earthquake Characteristics on Seismic Response of High-Rise Structures with Triple Friction Pendulum Isolator
    Ali Majdi, Mohammadreza Mashayekhi *, Ataallah Sadeghi Movahhed Pages 47-62

    Pulses of near-fault earthquakes are very effective in the seismic response of the Triple Friction Pendulum Isolator (TFPI). In previous studies, the effect of original bi-directional pulses components on the isolated tall buildings by TFPI was neglected. Also, the effect of changing the design parameters of TFPI on preventing seismic disaster in this type of building is unknown. For this reason, a 10 stories moment steel structure mounted on TFPI was designed. Then, the seven pairs of bidirectional near-fault earthquake records without and with removal pulses were applied to the isolated structure. The results show that the seismic responses on the base level decrease by reducing the velocity pulse amplitude (AP) and increasing the velocity pulse period (TP), also if the period of the isolators (TM) is being higher than TP, the seismic responses on the upper floors reduce. Moreover, Increasing the geometrical dimensions of the TFPI can significantly reduce the seismic effect of near-fault earthquake with pulses.

    Keywords: High-Rise Building, Triple friction pendulum isolator, Near-Fault earthquakes, Pulse characteristic