Abstract Reducing greenhouse gas (GHG) emissions from the built environment is essential to address the climate crisis. In Brazil, significant emission reductions may be achieved through revision of reinforced concrete design safety factors, which were defined empirically in the 1970s. This paper shows that reducing the dead load factor from 1.4 to 1.3 and increasing the live load factor from 1.4 to 1.5 can reduce GHG emissions by approximately 7% while improving structural safety. This study is exploratory and its estimate is based on the analysis of a single ten story regular building, composed of slabs, beams and columns; therefore, the findings should be verified for other structural configurations. Nevertheless, the proposed partial safety factor revision results in net cost-negative GHG emission savings due to reduced material consumption and is immediately applicable and scalable throughout Brazil, representing a potential strategy for reducing GHG emissions.
Abstract This article proposes a bridge deterioration index to support infrastructure management for Brazilians bridges. It begins with a review of current practices, covering inspection, evaluation, prediction models, safety, and prioritization. Next, it presents the index methodology, applied to 2,134 bridges in Brazil. The results identified twelve bridges in critical condition requiring immediate intervention. Additionally, the index enables better planning of future inspections and intervals. This approach aims to promote proactive maintenance and enhance infrastructure safety using historical data. However, caution is advised in interpreting the results, especially for extreme cases, recommending further investigations for more informed decision-making.
Abstract This study presents a comparative analysis of the performance and accuracy of predictive models for capillary absorption and water saturation in cementitious materials. Water absorption data from the literature are evaluated using formulations based on the power law, stretched exponential function, Weibull distribution, and the enhanced Terzaghi model to describe the temporal dynamics of water penetration and characterize the transport mechanisms involved. The ability of each model to represent the distinct phases of the absorption process is evaluated, with emphasis on anomalous water absorption, characterized by an initial rapid flow in capillary pores followed by a slower flow in gel pores. The distinction between these flows is essential for describing the interaction between the microstructure of cementitious materials and the evolution of absorption over time. The results provide a quantitative basis for assessing the suitability of the models in predicting the transition between absorption and saturation stages, contributing to the improvement of concrete durability modeling under real-world conditions and to the revision of technical standards. The results of the modeling and statistical analyses show that Weibull-type and stretched exponential models more accurately describe water absorption in concrete, while the square-root-of-time method produces significant errors.
Abstract This study evaluated the microstructural and mechanical impacts of incorporating specific furniture industry wastes (Eucalyptus wood ash and sewage treatment plant sludge) as partial Portland cement replacements. Pastes and mortars were prepared with 5%, 10%, 25%, and 50% substitution levels of either residue. A comprehensive methodology was applied, correlating macroscopic performance (workability, compressive strength) with continuous hydration kinetics (calorimetry, Ultrasonic Pulse Velocity) and microstructural evolution (SEM, XRD, FTIR). Results demonstrated that replacing 5% of cement with wood ash increased compressive strength by up to 28% compared to the reference series, driven by enhanced C-S-H formation. However, 50% ash substitution caused a 73% strength reduction, primarily attributed to a dilution effect, as the ash particles lacked the fineness required for a physical filler effect. Regarding the sewage sludge, low dosages (up to 10%) acted as a set retarder without significantly hindering overall hydration. Conversely, high sludge levels (50%) led to a severe loss of workability and an 85% drop in strength. Microstructural analyses revealed that the sludge's highly porous morphology and elevated organic content absorbed free water, critically inhibiting cement hydration.
Abstract This study investigates the influence of recycled concrete aggregates (RCA) on the elastic modulus of concrete, considering mixtures produced with 30%, 50%, and 100% replacement levels of natural coarse aggregates. In addition, steel fibers were incorporated at a constant dosage to improve post-cracking behavior. The main objective is to evaluate the relationship between static and dynamic moduli of elasticity and to assess the applicability of the Popovics-based formulation for estimating static modulus from dynamic measurements. Results indicate that increasing RCA content leads to a reduction in both compressive strength and static modulus of elasticity, as well as an increase in result dispersion due to material heterogeneity. The dynamic modulus showed lower sensitivity to replacement levels. The Popovics-based model systematically underestimated the static modulus, with discrepancies increasing for higher RCA contents. These findings highlight the need for calibration of empirical models when applied to recycled aggregate concretes.
Abstract This paper presents two models for designing waffle slabs against punching shear at edge column connections subject to moment transfer perpendicular and parallel to the slab's free edge. The suggested design models modify the ACI-318-25 code in three ways by replicating the loss of shear surface area of waffle slabs on the code shear critical section, implementing a modified concrete shear strength equation, and introducing a factor to account for the moment transfer for edge column-waffle slabs connections subjected to punching shear. They are verified with the test results of flat slabs from the literature and then applied to predict the punching shear of waffle slabs. The models agree well with the test results of waffle slabs and the test results of flat slabs.
Abstract The study of the behavior of gravity dams under seismic actions has, over time, been little explored in engineering projects in Brazil. In Brazil, although the occurrence of large magnitude earthquakes is uncommon, seismicity is not zero, especially in passive margin areas with intraplate seismicity. This study presents a method for evaluating the probability of seismic fragility of a dam's structural system. The method is based on computational simulation procedures involving pseudo-dynamic analyses and kriging modeling to establish the probabilistic characterization of the structure's safety factors, taking into account uncertainties in parameters related both to material properties and loading conditions, as well as ground motion characteristics. Stress analysis revealed critical concentration near the gallery, with maximum tensile stresses of 2.69 MPa and compressive stresses of -2.39 MPa. In stability assessment, all sliding safety factors exceeded the minimum design threshold (1.0), with the most critical case observed in the intermediate section under full reservoir conditions (1.05). Probabilistic analysis indicated failure probabilities ranging from 10−3 to 3.74 × 10−2 and reliability indices between 1.60 and 3.09, identifying the dam-foundation section as the most vulnerable and the intermediate section as the most resilient. The results highlight that foundation stiffness plays a decisive role in dam response, amplifying dynamic effects through multidomain interaction. Overall, the integration of numerical modeling with probabilistic methods proved effective for identifying critical sections, quantifying uncertainties, and supporting monitoring and reinforcement strategies. This approach strengthens dam safety management, contributing to failure prevention and mitigation of potential socio-economic impacts.
Abstract This study focuses on analyzing a fire-induced spalling risk assessment methodology for sprayed concrete for tunnel linings and investigates the thermal behavior of sprayed concrete. Sprayed concrete specimens with various polypropylene (PP) microfiber contents and different saturation conditions were exposed to fire. The internal temperature distribution was monitored during the fire tests and the occurrence of spalling was evaluated with quantitative parameters. The results show that lower contents of PP microfibers could not prevent spalling damage, which contributed to the rapid increase in the temperature profile in the material. The increase in temperature was employed to create novel criteria for verifying spalling. The increase in moisture content of specimens intensified the occurrence of spalling. The analysis of the temperature distribution in the sprayed concrete confirmed that the saturated condition is critical for the occurrence of spalling. Therefore, performing tests only in the saturated condition is in favor of safety and unifies this variable in the evaluation. Experimental and numerical data also showed that sprayed concrete has a lower thermal conductivity than cast concrete, which must be incorporated into guidelines for the design of sprayed concrete structures. Therefore, the novelties of this paper are the proposal of a unified saturation condition and temperature-based criteria for verifying spalling, and a preliminary parametrization for sprayed concrete thermal conductivity, which are lacking in literature. The results represent an important step towards a safe application of sprayed concrete in tunnel linings and in the development of a standardized test methodology that can contribute to better assess the complex behavior of fire in tunnels and further aid the development of future projects.
Abstract This research makes a novel and relevant contribution to the field of steel–concrete composite structures by investigating the behavior of Puzzle-shaped (PZ) and Clothoid-shaped (CL) shear connectors, which act as load-transfer devices in circular concrete-filled steel tube (CFST) columns with slender cross-sections. An experimental program was conducted in which loads were applied to the connectors embedded in slender CFST columns, and the results were compared against prediction models provided by current design codes. Experimental results showed that CL connectors achieved greater strength and stiffness than PZ connectors, while both exhibited ductile response. Damage investigation revealed concrete shear dowels and transverse cracking around the connections. The current calculation method used for CL and PZ connectors was developed for composite beams. Its direct application to CFST columns yielded inconsistent results concerning the behavior and strength of the connectors. Therefore, this study proposed a new calculation procedure for connectors in CFST columns, allowing a better approximation to the experimental results.
Abstract Prestressed hollow-core slabs are widely utilized in construction due to their high structural efficiency and low self-weight. However, the time-dependent behavior of concrete, particularly shrinkage and creep, introduces uncertainties that can compromise the serviceability and durability of these structures. This study experimentally evaluated the prestress transfer length and time-dependent strains of concrete used in hollow-core slabs, correlating the results with the provisions of NBR 6118, NBR 14861, and BS EN 1992-1-1:2023. The methodology involved testing slabs produced on industrial casting beds, with monitoring of shrinkage and creep strains under realistic production and environmental conditions. Additionally, the long-term deflection of a slab subjected to sustained loading was assessed. Results indicated that the mean prestress transfer length exceeded normative values. Moreover, the BS EN 1992-1-1:2023 standard demonstrated better agreement in estimating shrinkage and creep strains compared to experimental data. Long-term deflection was predicted with good accuracy, showing deviations of less than 10%. It is concluded that adjustments to the model proposed in the NBR 6118 standard are required to better represent the time-dependent behavior of concrete in hollow-core slabs, accounting for actual production and exposure conditions.
Abstract This study investigates the use of synthetic fibers—glass, polyester, polypropylene, and polyethylene—in reinforced concrete beams to assess their contribution when the structural element is subjected to shear stress. The methodology began with the characterization of the concrete constituents (cement, fine and coarse aggregates, and fibers), following the EPUSP-IPT Concrete Dosing method. Subsequently, the beams were cast as follows: one (1) reference beam without added fibers and twelve (12) beams with added macrofibers—three (3) beams for each fiber type (fiberglass, polyester, polypropylene, and polyethylene). Shear performance was then evaluated through experimental beam failure testing. Glass and polyester microfibers contributed to post-peak or post-cracking stability, reducing the likelihood of sudden failure. Their contribution to shear strength gain was 15.1% for VFV01 (beam with 0.024% glass microfiber) and 21.6% for VFPO02 (beam with 0.032% polyester microfiber), both relative to the reference beam (VR). Regarding the polypropylene and polyethylene macrofibers, it was observed that increasing the fiber content in the concrete mix led to greater ductility. Among the tested fiber contents, 0.36% and 0.48% polyethylene and 0.16% polypropylene represented critical percentages, indicating values close to the optimal fiber content. This suggests that the composite's load-bearing capacity approached the matrix failure threshold. Therefore, this study demonstrates that fiber reinforcement can be effectively used to control and enhance the shear performance of structural concrete. This composite presents itself as a promising partial substitute for transverse reinforcement—namely, stirrups in beams—by reducing the likelihood of sudden failure. Glass, polyester, polypropylene, and polyethylene fibers, at certain percentages, contributed to increased shear strength and toughness of the concrete.
Abstract High-strength concrete (HSC) provided significant advances in civil construction due to its superior strength, efficiency, and durability against environmental attacks. However, given the high cement content, low water-to-cement ratio, and the presence of mineral additives, it is crucial to prevent the development of induced tensile stresses that can lead to autogenous shrinkage. This shrinkage may result in cracking of structural elements, thereby compromising durability. One method explored to reduce autogenous shrinkage in HSC is the use of superabsorbent polymers (SAP) as internal curing agents. In this context, this work aims to analyze the influence addition of SAP and nano silica (NS) on the durability of Portland cement microconcrete. For this, the experimental program consisted of three mixtures of high-strength microconcrete: one containing 0.3% SAP, another containing 0.3% SAP and 1% NS, and one used as a reference with a water/cement ratio equal to 0.35. The behavior of concrete in its hardened state was assessed through the execution of the following tests: simple axial compression strength, modulus of elasticity, water absorption by capillarity and immersion, electrical resistivity, and chloride migration. The results indicate that incorporating SAP does not lead to a reduction in the mechanical properties or durability of the microconcretes; instead, it enhances these properties. Additionally, while the addition of NS causes a negligible increase in modulus and strength values at 28 days, it significantly boosts compressive strength at earlier ages. The microconcrete containing SAP and NS showed the best performance in the durability tests, indicating that the addition of NS further enhanced the concrete's durability. It was confirmed that the dense microstructure typical of HSC is maintained even with the presence of pores formed by the SAP desorption process. This is because these pores are larger and isolated, rather than smaller and interconnected.
Abstract This study presents a structural fire safety assessment of existing concrete bridges in federal highways in Brazil through a diagnostic analysis based on design standards and structural performance benchmarking under fire situations. Despite lower fire incidence compared to buildings, bridges face significant risks from vehicle-related fires, leading to long operational interruptions and economic losses. Brazilian and international standards lack specific guidelines for bridge fire design, creating a critical gap in the standards towards the infrastructure resilience. A case study of typical concrete bridges (isostatic spans: 10–20 m) was conducted, employing thermal-structural simulations using the hydrocarbon fire curve (H-curve) and simplified methods from Eurocode 2-1-2 and ABNT NBR 15200. Results showed that bridges constructed prior to 1960 (Group 1) exhibit fire resistance for ≤60 minutes, while post-1985 bridges (Group 3) withstand up to 180 minutes. The 500°C isotherm and Brazilian methods demonstrated good agreement with established zone methods, validating their applicability for prescriptive design for ordinary reinforced concrete bridges. Older bridges, designed for outdated load bridge models, showed insufficient resistance under current traffic loads (TB-450), requiring immediate traffic interruption at the fire starting. It is important to highlight that the current TB-450 load model represents a significant increase in traffic intensity and vehicle weight compared to previous standards, reflecting the current reality of Brazilian highways. The hydrocarbon curve showed practical for routine scenarios, avoiding complex CFD modeling. The study highlights the urgent need for Brazil to adopt bridge-specific fire safety rules and integrate fire resilience into maintenance programs. Retrofitting older structures and updating protocols of bridging management is the rational solution to withstand risks evolution, ensuring long-term safety and functionality of critical infrastructure.
Abstract This research aims to present a proposal for an analytical equation capable of representing the correlation between compressive strength and dynamic modulus of elasticity as a function of heating temperature, by means of a surface plane for a range of strengths of mortars for structural masonry. Three types of industrialized mortars were chosen based on their reference compressive strengths (4, 10 and 14 MPa), subjected to heating temperatures of 300, 600 and 900 °C, and experimental tests to evaluate compressive strength and dynamic modulus of elasticity. The data obtained were correlated with studies that used similar methodologies (strength ranges of mortars, heating temperatures, specimen shape, heating rate), aiming to establish a behavior standard for mortars for structural masonry subjected to high temperatures.
Abstract The increasing construction of twin tunnels necessitates a thorough understanding of their mechanical interactions with transverse galleries and surrounding rock mass. This study presents a 3D finite element analysis of the intersection zone between deep twin tunnels and a transverse gallery, incorporating time-dependent effects such as concrete creep, shrinkage, and rock mass creep. The computational model is verified against prior numerical studies, demonstrating its reliability in predicting lining internal forces. Furthermore, a comparative analysis between different rock mass friction angles highlights their influence on deformations and pressures in the perimeter of the lining, which are important for design or reinforcements decisions in tunnels-gallery intersection zone. Results reveal significant anisotropy in lining pressures and wall deformations, influenced by lining type (elastic or viscoelastic) and rock mass friction angle. Maximum deformations occur at the tunnel crown, indicating horizontal ovalization, while minimum deformations, and corresponding peak pressures, appear near the tunnel sidewall. Higher friction angles reduce convergence and pressures at these locations, mainly at the end of construction. Viscoelastic lining exhibits greater long-term redistribution of both deformations and pressures. The study highlights the critical role of 3D modeling and time-dependent material behavior for tunnel design in this zone.
Abstract Ultra-high performance concrete (UHPC) has emerged as a promising material in civil construction due to its excellent mechanical properties. However, its dense microstructure makes it highly susceptible to explosive spalling under elevated temperatures, limiting its application in fire-exposed environments. The incorporation of polypropylene (PP) fibers has been widely investigated as a strategy to mitigate this phenomenon, although the literature presents a broad range of dosages with varying levels of effectiveness. In this context, the present study evaluated UHPC mixtures containing medium (2.7 kg/m3) and high (8.1 kg/m3) PP fiber contents—based on literature classifications—to assess their influence on workability, mechanical performance, spalling behavior, and residual compressive strength after exposure to 700 °C. The addition of fibers significantly affected the fresh-state consistency, with flow reductions of 13.6% and 44.4% for the medium and high dosages, respectively. Despite these changes, the mechanical performance before heating remained statistically unaffected. In contrast, spalling occurred in all reference specimens (without fibers), while both fiber-reinforced mixtures effectively prevented the phenomenon, indicating that even the medium dosage was sufficient for mitigation. This behavior is attributed to the melting of PP fibers during heating, which promotes microcrack formation and facilitates the release of internal vapor pressure. This mechanism is further supported by the observed mass loss of approximately 9% in both mixtures after thermal exposure.
Abstract Cement and sand mortar is the main material used for coatings in Brazil. This is due to its low cost, availability of raw materials, and easy application. Determining the drying time is crucial for initiating subsequent stages, such as painting, which can only begin once the material is fully dried. Otherwise, various defects may appear in the substrate-paint interface. In this study, the efficiency of using phenolphthalein to determine the moment when the mortar reaches a dry state was evaluated. Thus, the materials used were characterized through X-ray diffraction and scanning electron microscopy. Furthermore, the workability and compressive strength parameters were determined for the coating without additives (ARG0) and for the material containing phenolphthalein (ARG3). It was found that using the additive at a 3% proportion yielded promising results, indicating the presence of moisture in the material by changing the surface tone of the sample until it dried. Regarding the compressive strength of the material, values of 12.03±1.65 MPa were obtained, making its application viable. Finally, comparing the ARG0 composite with ARG3, there was a reduction of 35 and 28 minutes in the initial and final setting times, respectively. Moreover, the microstructure and crystalline structure showed no changes when comparing both materials.
Abstract In many developing nations, most of the transportation infrastructure was constructed during the 1960s. Many bridges, having been operational for more than 50 years, have shown no signs of structural deterioration. In most cases, there are no project records, requiring engineers to assess these structures. The safety analysis of these structures, using the same criteria as for new constructions is proved unsatisfactory, given that the allowable deviations in design could be greater for structures already built, with high construction quality control, justifying a long period of good service. The current Brazilian code for bridges includes provisions for reducing partial safety factors for existing structures with many years of good service, based on the Eurocode prEN 1990-2 proposal. Applying reliability theory, this study evaluates the extent to which improved construction quality—defined as minimizing construction deviations and material property variability—can justify the good performance observed over the years. Furthermore, it explores the possibility of reducing the reference period for accidental loads from 50 years for new constructions to a shorter period. It is demonstrated that the reduction in load safety factors resulted in acceptable increases in reliability indices, maintaining safety in situations of bending and shear in reinforced concrete superstructures, even with the moving load increasing over time. Thus, it is possible to avoid the need for costly strengthening of structures that continue to perform well.
Abstract: This study evaluated the effect of heating on the mechanical properties of reactive powder concrete (RPC) with water-to-cement ratios (w/c) of 0.18 and 0.21 after 91 days of curing, as well as the reduction in potential damage from heating by incorporating polypropylene fibers (PPF) with substitution contents of 0%, 0.15%, and 0.30% by volume. After cooling, tests were conducted on axial compressive strength, diametral tensile strength, ultrasonic pulse velocity (UPV) and mass variation. Explosive spalling was observed in all samples without fiber addition at temperatures of 400 °C, 600 °C, and 800 °C with higher intensity for samples with lower w/c. The addition of 0.30% fiber content was found to be satisfactory in mitigating spalling while the addition of 0.15% did not fully inhibit the occurrence of the phenomenon. An increase in axial compressive strength of up to 61% was observed after exposure to a temperature of 300 °C and remained at this level even when exposed to a temperature of 800 °C. It was found that, in order for RPC to minimally resist spalling and maintain considerable residual mechanical strength, the use of polypropylene fibers as passive protection was essential.
Abstract This study presents a comprehensive numerical investigation into the punching shear behavior of flat reinforced concrete slabs incorporating recycled concrete aggregates (RCA). Using the ABAQUS/CAE finite element software, nonlinear simulations were conducted based on the Concrete Damaged Plasticity (CDP) model. Three slab configurations with 0%, 30%, and 100% RCA replacement were analyzed and calibrated against experimental results to ensure numerical accuracy. The validation process included mesh sensitivity, dilation angle, and viscosity parameter assessments, achieving excellent agreement between numerical and experimental peak loads, with deviations below 5%. Parametric analyses evaluated the influence of slab thickness and column dimensions on punching shear capacity. The findings support the structural feasibility of RCA in flat slabs and contribute to the development of more sustainable and reliable design practices in structural engineering.
