International Journal of Structural Engineering (6 papers in press)

Regular Issues

• Effect of superplasticiser mixing time on pumping characteristics of concrete mixtures  
  by Quang-Nhat Pham, Van-Nhan Vu, Phu-Anh-Huy Pham 
  Abstract: This article discusses experimental results related to the assessment of concrete slump and pump parameters utilising varying proportions of superplasticisers at two distinct time intervals: the initiation of mixing and the end of curing period. The test findings indicate that the pumpability of concrete mixes depends on the specific superplasticiser ratio used during each designated time. Furthermore, the slump of concrete mixes exhibits notable recovery when utilising a specific admixture ratio at the end of the concrete curing process. Additionally, the friction parameters, represented as shear stress (r) and viscous surface friction (n), exhibit improvement with the gradual incorporation of admixture content at different stages of the concretes curing period. The optimal proportion of admixture introduced at mixing initiation falls within the range of (20 / 40)%. Importantly, the addition of additives in various stages during the concrete mixing period, at judicious ratios, does not have adverse effects on concrete strength.
  Keywords: contact slip threshold; superplasticiser; admixture; concrete pumping; concrete slump.
  
  
• Soil-structure interaction using equivalent support stiffness in response of cooling towers  
  by Sachin R. Kulkarni 
  Abstract: The idealisation of support boundary conditions for the hyperbolic shape cooling tower shell has significant influence on static and dynamic response of the shell. The sensitivity of the support boundary conditions on the static response of the cooling towers is investigated. Studies on soil-structure interaction (SSI) on static response of cooling tower shell available in the literature are largely focussed on meridional and hoop forces for a particular value of soil stiffness under consideration. The current study focuses on effect of SSI on static response of hyperbolic cooling tower shell for the practical range of soil stiffness values. It is observed that with the decrease in soil stiffness, the vertical displacement of tower shell increases with no significant change in meridional and hoop forces, indicating rigid body displacement rather than deformation. The applicability of equivalent support stiffness concept developed by the authors earlier is investigated to evaluate the static response of the shell on column supports including SSI. The study also includes the redistribution of membrane forces and column forces due to loss of column support at a location.
  Keywords: boundary condition; soil-structure interaction; SSI; static response; equivalent support stiffness.
  DOI: 10.1504/IJSTRUCTE.2024.10064894
   
  
• Experimental investigation on the compressive behaviour of concrete confined by glass fibre geogrid mesh  
  by Seyed Shaker Hashemi, Seyedahmadreza Rezaei, Mohsen Matin, Mohammad Vaghefi 
  Abstract: The study aims to experimentally investigate glass fibre reinforced geogrid (GFRG) mesh confined concrete behaviour. The utilised mesh in this study has openings of 20 mm, weighing 240 gr/m², and a tensile strength of 60 KN/m. For this research, 42 standard cylindrical concrete specimens with a diameter of 150 mm and a height of 300 mm were constructed. These specimens were created in both unconfined and confined states, with GFRG mesh confined concrete. The specimens had varying hoop layer counts (1, 1.5, and 2 layers) with concrete covers of 10 mm and 20 mm. After fabrication and curing, the specimens were tested to evaluate their ductility, energy absorption, and compressive strength under various confinement layers and concrete covers. The results revealed that the incorporation of GFRG mesh confined concrete to induce confinement leads to a slight decrease of approximately 3% in confinement strength at 28 days. Ductility and post-cracking behaviour improved, leading to a 20% increase in energy absorption.
  Keywords: confined concrete; compressive behaviour; glass fibre reinforced geogrid; GFRG.
  DOI: 10.1504/IJSTRUCTE.2024.10064895
   
  
• Analysing the dynamic behaviour of a functionally graded beam subjected to a moving force under varied boundary conditions  
  by Mohamed Bouamama, Abbes Elmeiche, Azzeddine Belaziz, Abdelhak El Hannani, Hammoudi Abderazek 
  Abstract: In this article, the dynamics of both free and forced vibrations in functionally graded materials (FGM) beams are explored by examining various physical and geometrical parameters under different boundary conditions. The beam's material properties feature an upper ceramic facet and a lower metal facet, which vary continuously through the thickness direction following a power law function for the functionally graded materials (P-FGM). The external force is determined by a moving concentrated force, with or without considering the inertial effects of the transient load. The governing differential equations are derived through a theoretical formulation using the logarithmic shear function of the beam (LSDBT). For the study of free vibrations, an analytical method is employed, which involves separating variables and applying the modal approximation method of Rayleigh-Ritz. Numerical calculations are used to analyse forced vibrations, utilising Newmark's temporal method. A parametric investigation is conducted on different beam configurations to assess the impact of various parameters on the dynamic responses of the beam. The results from our proposed model demonstrate a strong agreement with the findings in the literature, validating the effectiveness and accuracy of our approach.
  Keywords: FGM beams; free vibration; forced vibrations; moving force; eigenfrequencies; LSDBT.
  DOI: 10.1504/IJSTRUCTE.2024.10064896
   
  
• Damping impact with different water level on structural behaviour of elevated water towers  
  by Taha Yasin Altıok, Muhammet Ensar Yiğit, Cansu Beril Eser, Ali Demir 
  Abstract: Water towers with tall and delicate geometry are highly susceptible to seismic actions. This study aims to develop a fast, reliable and cost-effective method for examining the seismic behaviour of such structures, by taking a reinforced concrete water tower with known material parameters and dimensions as an example. The impact of water absorption on structural response under dynamic loading at empty, half full and full capacity was investigated. Ideal finite element models of the water tower were constructed using operational modal analysis. Linear time history analyses were conducted using the finite element software. The structure was modelled with the Lagrangian approach, while the fluid was modelled using the Eulerian approach in finite element analysis. The coupled Eulerian Lagrangian technique was employed for the analysis. Results obtained from the analyses indicate that an increase in tank fill level led to enhanced structural damping, resulting in reduced displacement and stress values.
  Keywords: elevated water tower; coupled Eulerian Lagrangian technique; operational modal analysis; OMA; damping of water; fluid mechanics.
  DOI: 10.1504/IJSTRUCTE.2024.10064897
   
  
• Integrating FTA, FMEA and Delphi technique in addressing major defects for high rise residential complex - a lesson learned from a large-scale apartment project  
  by Jason Lim, Elia Oey, Michael Simbung 
  Abstract: In the context of high-rise residential projects, managing defects is crucial for process efficiency and customer satisfaction. Using a case study of a nine-tower apartment complex in The Greater Jakarta Area, this study intends to analyse and prioritise failure modes as well as offer action plans for dominant defects for high rise residential complexes. It does this by integrating four analysis techniques: failure mode effect analysis (FMEA), Pareto analysis, fault tree analysis (FTA), and the Delphi method. The research identifies four primary defects using Pareto analysis. FTA and FMEA help uncover failure modes, failure effects, root causes, and existing controls. By involving a panel of experts, the Delphi technique establishes the risk priority number (RPN) for each failure mode. The findings highlight top six specific failure modes related to door and framework, wall and masonry work, ceramic tiling work, and painting work. Action plans are proposed to mitigate these defects in high-rise residential projects.
  Keywords: Delphi; defect; fault tree analysis; FTA; failure mode effect analysis; FMEA; Pareto.
  DOI: 10.1504/IJSTRUCTE.2024.10064898