International Journal of Structural Engineering (5 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 (τ) and viscous surface friction (η), exhibit improvement with the gradual incorporation of admixture content at different stages of the concrete's 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.
  DOI: 10.1504/IJSTRUCTE.2024.10066776
   
  
• A review of fluid-structure-soil interaction in elevated water tanks  
  by Jyoti B. Chouhan, Anand M. Gharad 
  Abstract: Water, a vital resource for sustaining life, requires proper storage. Elevated water tanks are constructed to serve this purpose. These tanks must operate reliably, even during and after earthquakes. Analysing the hydrodynamic behaviour of elevated water tanks is challenging due to the complex fluid-structure-soil interaction involved. The interaction between the tank and the surrounding soil structure, influenced by soil properties such as elasticity, cohesion, and angle of friction, significantly impacts the tank's performance. This paper presents recent studies focused on modelling the fluid-structure-soil interaction analysis of elevated water tanks. The objective of this study is to provide an overview of the fluid-structure-soil interaction concept for the analysis of elevated water tanks. A systematic literature review was conducted to select and categorise publications that include experimental and analytical studies on fluid-structure interaction, soil-structure interaction, and fluid-structure-soil interaction.
  Keywords: elevated water tanks; EWTs; fluid-structure interaction; FSI; soil-structure interaction; SSI; fluid-structure-soil interaction.
  DOI: 10.1504/IJSTRUCTE.2024.10066780
   
  
• Experimental and numerical investigations of cracking onset time of Nkolomdom's (Cameroon) gneiss rock, during its breaking by a non-explosive expanding material  
  by Lucas Djondanbe Yadang, Hervé Joël Tchognia Nkuissi, Frank Ferry Kamgue Tiam, André Chamgoué Cheage, Luc Leroy Mambou Ngueyep, Theodore Tchotang 
  Abstract: In this paper, a non-explosive expansive material (NEEM) is used to fragment gneiss rock. The main objective is to evaluate the minimum cracking time (TOC) of this rock. For this, 45 rock blocks are selected and fragmented using the expansive cement blasting method. The minimum time for cracking to appear for each sample is studied. The multiple parameter linear regression method is used to establish a mathematical model of the minimum time for cracking to appear as a function of five parameters, namely the diameter of the borehole, the spacing between two holes, the ambient temperature, the temperature of the mixing water and the quantity of mixing water. The established model is then used to optimise this minimum cracking appearance time by the genetic algorithm method. The experimental result revealed a minimum time of 6 hours. A correlation coefficient of 0.804006634 is obtained with the established model. Optimisation by genetic algorithms (GA) revealed a minimum crack appearance time of 2 hours and 39 minutes.
  Keywords: blasting; non-explosive expansive material; NEEM; gneiss; cracking; multiple parameters linear regression; genetic algorithms; GAs.
  DOI: 10.1504/IJSTRUCTE.2024.10066779
   
  
• Strengthening and retrofitting of low strength reinforced concrete slabs with high strength overlay: experimental and numerical investigation  
  by Asad Ullah Qazi, Ali Murtaza Rasool, Muhammad Faheem Ud Din Afzal, Asif Hameed, Nadeem Mahmood, Noor Yaseen 
  Abstract: The study examined the effect of high-strength overlay on the flexural strength of low-strength reinforced concrete (RC) slabs weakened by inadequate curing conditions and aimed to validate these findings through numerical simulations. Although the concrete was specified to be 28 MPa, the slabs were cast with 18 MPa concrete. Eight 100 mm thick slabs were tested using the third-point loading test; two failed in the compression zone without any strengthening. The remaining six were reinforced with a 50 mm overlay of 35 MPa compressive strength: two with anchors, two with epoxy, and two with both anchors and epoxy. Additionally, two unstrengthened slabs were retrofitted, one with anchors and the other with epoxy. Results showed that strengthening and retrofitting increased the flexural capacity by 70% and shear capacity by 10%. The failure mechanism shifted from compression in unstrengthened slabs to shear in strengthened and retrofitted slabs. Numerical analysis corroborated the experimental results.
  Keywords: experimental testing; numerical analysis; low strength rc slabs; high strength overlay.
  DOI: 10.1504/IJSTRUCTE.2024.10066781
   
  
• Automated calibration of recorded ground motions for nonlinear response history analysis of isolated bridges  
  by Xuan Dai Nguyen, Van Tu Nguyen, Ba Thang Phung, Hoang Nguyen, Thanh Dong Nguyen 
  Abstract: Time history analysis of isolated bridges is frequently complicated and involves numerous steps, especially ensuring the suitability of the accelerogram as input data. The use of commercial software to analyse structural models can lead to difficulties in controlling the analytical conditions. This study aims to accurately and effectively automate the nonlinear time-history analysis of isolated bridges using a developed subprogram. There are two specific parts to the proposed algorithm, including calibration of the accelerograms and nonlinear analysis of structures. The subprogram was developed in MATLAB for rapid and effective analysis of nonlinear structures. The concordance of the calibrated accelerograms was evaluated by comparing the response spectrum of selected accelerations with the results using SeismoMatch and the target spectrum. The accuracy of nonlinear analyses is confirmed using SAP2000 software. It shows that the proposed method offers good agreement and is a powerful tool for the time-history analysis of isolated structures.
  Keywords: ground motion calibration; calibration of ground motion; linear spectral matching method; nonlinear time-history analysis; automated calculation; seismic analysis.
  DOI: 10.1504/IJSTRUCTE.2024.10066778