This article introduces simulations of theoretical material with controlled properties for the evaluation of the effect of key parameters, as volumetric fractions, elastic properties of each phase and transition zone on the effective dynamic elastic modulus. The accuracy level of classical homogenization models was checked regarding the prediction of dynamic elastic modulus. Numerical simulations were performed with the finite element method for evaluations of the natural frequencies and their correlation with E_d through frequency equations. An acoustic test validated the numerical results and obtained the elastic modulus of concretes and mortars at 0.3, 0.5 and 0.7 water–cement ratios. Hirsch calibrated according to the numerical simulation (x = 0.27) exhibited a realistic behavior for concretes of w/c = 0.3 and 0.5, with a 5% error. However, when the water-to-cement ratio (w/c) was set to 0.7, Young’s modulus displayed a resemblance to the Reuss model, akin to the simulated theoretical triphasic materials, considering matrix, coarse aggregate and a transition zone. Hashin-Shtrikman bounds is not perfectly applied to theoretical biphasic materials under dynamic situations.

This paper provides guidelines for cyclic loading bending test simulation and modal analysis of a reinforced concrete I-beam. For this purpose, experimental and numerical cyclic bending test were performed. In the experimental study, the natural frequencies of the structure in the intact and damaged states were measured. The simulation of the cyclic bending test was done with Concrete Damaged Plasticity model (CDP), implemented in Abaqus finite element software. Based on the experimental results, different constitutive models for concrete were evaluated. In order to evaluate the dynamic behavior of the structure in the numerical model, the automatic calibration of the finite element model by Genetic Algorithm (GA) was used. With the calibrated numerical model, methodologies for estimating the overall damage of the structure based on its dynamic properties were proposed. The results confirm that the well-designed numerical model is able to efficiently represent the cyclic loading bending test. In addition, the proposed global damage estimates demonstrate the coherence between numerical and experimental models.

This paper significantly extends investigations into internal damping ratios in both undamaged and damaged conditions for normal-strength concretes (NSCs) and high-strength concretes (HSCs). This study examines concretes with compressive strengths ranging from 42 to 83 MPa. Cyclic loads were applied using a servo-controlled hydraulic testing machine, and for each cyclic step, the dynamic elastic modulus ($E_d$) and internal damping ratio ($\xi$) were determined through acoustic tests. The results show that the normal-strength concretes ($f_c=42$ MPa) exhibited an undamaged internal damping ratio of $\xi =0.5\%$, reaching a maximum of $\xi =2.5\%$ at a damage index of 0.8. Conversely, the high-strength concrete mixtures ($f_c=83$ MPa) showed an undamaged internal damping ratio of $\xi =0.29\%$, with a peak value of $\xi =0.93\%$ at a damage index of 0.32. The initial internal damping values are influenced by porosity and transition zones, which affect the material behavior under cyclic loads. Progressive damage leads to increased Coulomb damping due the cracking process. Few studies have quantified and comprehended the internal damping ratio under cyclic loading-induced damage, and this research advances our understanding of NSC and HSC behavior under dynamic excitation and damage evolution, especially in impact scenarios.

Recently, the feasibility of producing cementitious nanocomposites has been widely investigated. Cement-based nanocomposites with the incorporation of nano silica [¹ 1 L. U. D. Tambara et al., “Effect of the nanosilica source on the rheology and early-age hydration of calcium sulfoaluminate cement pastes,” Constr. Build. Mater., vol. 327, pp. 126942, Jul. 2022, http://dx.doi.org/10.1016/j.conbuildmat.2022.126942. http://dx.doi.org/10.1016/j.conbuildmat.... 2 Q. Fu, X. Zhao, Z. Zhang, W. Xu, and D. Niu, “Effects of nanosilica on microstructure and durability of cement-based materials,” Powder Technol., vol. 404, pp. 117447, May 2022, http://dx.doi.org/10.1016/j.powtec.2022.117447. http://dx.doi.org/10.1016/j.powtec.2022.... ]-[³ 3 M. Kooshafar and H. Madani, “An investigation on the influence of nano silica morphology on the characteristics of cement composites,” J. Build. Eng., vol. 30, pp. 101293, Sep. 2020, http://dx.doi.org/10.1016/j.jobe.2020.101293. http://dx.doi.org/10.1016/j.jobe.2020.10... ], carbon nanotubes [⁴ 4 L. Silvestro, A. S. Ruviaro, P. R. Matos, F. Pelisser, D. Z. Mezalira, and P. J. P. Gleize, “Functionalization of multi-walled carbon nanotubes with 3-aminopropyltriethoxysilane for application in cementitious matrix,” Constr. Build. Mater., vol. 311, pp. 125358, Oct. 2021, http://dx.doi.org/10.1016/j.conbuildmat.2021.125358. http://dx.doi.org/10.1016/j.conbuildmat.... 5 L. Silvestro, G. T. S. Lima, A. S. Ruviaro, P. R. Matos, D. Z. Mezalira, and P. J. P. Gleize, “Evaluation of different organosilanes on multi-walled carbon nanotubes functionalization for application in cementitious composites,” J. Build. Eng., vol. 51, pp. 104292, Feb. 2022, http://dx.doi.org/10.1016/j.jobe.2022.104292. http://dx.doi.org/10.1016/j.jobe.2022.10... 6 J. Huang, D. Rodrigue, and P. Guo, “Flexural and compressive strengths of carbon nanotube reinforced cementitious composites as a function of curing time,” Constr. Build. Mater., vol. 318, pp. 125996, Nov. 2022, https://doi.org/10.1016/j.conbuildmat.2021.125996. https://doi.org/10.1016/j.conbuildmat.20... ]-[⁷ 7 F. Gao, W. Tian, Z. Wang, and F. Wang, “Effect of diameter of multi-walled carbon nanotubes on mechanical properties and microstructure of the cement-based materials,” Constr. Build. Mater., vol. 260, pp. 120452, Nov. 2020, http://dx.doi.org/10.1016/j.conbuildmat.2020.120452. http://dx.doi.org/10.1016/j.conbuildmat.... ], graphene [⁸ 8 G. Mishra, A. Warda, and S. P. Shah, “Carbon sequestration in graphene oxide modified cementitious system,” J. Build. Eng., vol. 62, pp. 105356, Jul. 2022, http://dx.doi.org/10.1016/j.jobe.2022.105356. http://dx.doi.org/10.1016/j.jobe.2022.10... 9 X. Kong, R. Wang, T. Zhang, R. Sun, and Y. Fu, “Effects of graphene oxygen content on durability and microstructure of cement mortar composites,” Constr. Build. Mater., vol. 354, pp. 129121, Jul. 2022, http://dx.doi.org/10.1016/j.conbuildmat.2022.129121. http://dx.doi.org/10.1016/j.conbuildmat.... ]-[¹⁰ 10 A. G. Alex, A. Kedir, and T. G. Tewele, “Review on effects of graphene oxide on mechanical and microstructure of cement-based materials,” Constr. Build. Mater., vol. 360, pp. 129609, Nov. 2022, http://dx.doi.org/10.1016/j.conbuildmat.2022.129609. http://dx.doi.org/10.1016/j.conbuildmat.... ], and nano titanium [¹¹ 11 M. Orakzai, “Hybrid effect of nano-alumina and nano-titanium dioxide on mechanical properties of concrete,” Case Stud. Constr. Mater., vol. 14, pp. e00483, Jun. 2021, http://dx.doi.org/10.1016/j.cscm.2020.e00483. http://dx.doi.org/10.1016/j.cscm.2020.e0... 12 L. Ingrisova and P. Hajek, “Contribution of TiO2 and ZnO nanoparticles to the hydration of Portland cement and photocatalytic properties of High Performance Concrete,” Case Stud. Constr. Mater., vol. 16, pp. e00965, Nov. 2022, http://dx.doi.org/10.1016/j.cscm.2022.e00965. http://dx.doi.org/10.1016/j.cscm.2022.e0... ]-[¹³ 13 D. Jegatheeswaran, S. M. Subash, C. S. Ravi, B. Rajalakshmi, and D. Z. Rahman “Investigational work on self-cleaning cement mortar with titanium dioxide in partial replacement of cement,” Mater. Today Proc., vol. 65, no. Pt 8, pp. 3161-3165, 2022, https://doi.org/10.1016/j.matpr.2022.05.356. https://doi.org/10.1016/j.matpr.2022.05.... ] stand out in the scientific field. Incorporating nanomaterials aims to produce composites with properties that focus on applicability (e.g., self-sensing application) or enhance mechanical properties. However, the application of these nanomaterials is conditioned to some limitations associated with the synthesis in large quantities to consolidate their incorporation in mortars and concretes. Therefore, most studies of nanomaterials are carried out in cementitious pastes [¹⁴ 14 L. Silvestro and P. J. P. Gleize, “Effect of carbon nanotubes on compressive, flexural and tensile strengths of Portland cement-based materials: a systematic literature review,” Constr. Build. Mater., vol. 264, pp. 120237, Dec. 2020, http://dx.doi.org/10.1016/j.conbuildmat.2020.120237. http://dx.doi.org/10.1016/j.conbuildmat.... ].

Composite slabs have gained popularity in modern high-rise construction due to their superior load-bearing capacity and reduced self-weight. The vulnerability of the unprotected steel deck under fire conditions poses serious challenges, as the rapid reduction in steel strength and stiffness can compromise structural resistance and accelerate fire spread. This study presents a comprehensive numerical simulation to assess the fire behaviour of a novel composite slab and a new proposal for a simplified method. Three insulation techniques are investigated: a steel shield for the thinner part, a steel shield with the cavity filled with mineral wool, and a mineral wool plate applied from below. The simplified method is proposed to evaluate the fire resistance using new empirical coefficients, recalibrated within the framework of the prEN 1994-1-2 to allow for precise temperature predictions in steel components under standard fire. The numerical model, validated against experimental results, shows that the steel shield insulation extends the time to reach critical temperatures by approximately 25%. In contrast, mineral wool insulation proved to be substantially more effective by reducing temperatures in the UPPER 2 region by up to 89% compared to uninsulated slabs, after 60 min of fire exposure. This significant temperature reduction increases the load-bearing capacity during 60 min of fire exposure by 29%, also resulting in a potential reduction of approximately 22% in carbon emissions. The findings underscore and highlight the potential of these insulation systems to enhance the overall safety and resilience of composite slabs under fire, offering valuable insights for structural fire design.