Abstract This study investigates the flexural behavior of reinforced concrete (RC) footings supported on natural soil and internally strengthened using steel mesh fabrics (SMFs) as a novel alternative to conventional steel bars. Despite the widespread application of SMFs in structural retrofitting, their use as internal tensile reinforcement in RC footings remains largely unexplored. To address this gap, an experimental program involving ten small-scale square footings was conducted to evaluate the influence of SMF quantity, layering patterns, bar-mesh hybrid configurations, and mesh geometry on structural performance under flexure. The results demonstrate that replacing conventional steel bars with SMFs of equal reinforcement weight increased the ultimate load by up to 22.5% and enhanced the energy absorption capacity by up to 237%. Increasing the number of SMF layers raised the ultimate load from 120 kN (one layer) to 175 kN (three layers), corresponding to a 45.8% increase, while ductility decreased due to stiffness growth. Hybrid bar–mesh configurations showed superior performance, where the fan-shaped layout achieved an ultimate load of 161 kN and an energy absorption capacity of 2056 kN·mm, representing increases of 34.2% and 121.6%, respectively, compared to the single-layer mesh specimen. Moreover, partial-area SMF reinforcement beneath the column zone improved load capacity by up to 20% with limited reduction in ductility. Complementary numerical analysis using a validated 3D finite element model was conducted to assess critical variables, including mesh shape, reinforcement layout, and soil–structure interaction. The numerical simulations closely aligned with experimental results, providing deeper insight into stress distribution and deformation behavior. The findings confirm that SMFs offer a structurally efficient and economical alternative for enhancing the flexural performance, ductility, and energy dissipation of RC footings.
Systems of building construction. Including fireproof construction, concrete construction
Ronald Wilfred Asiimwe, Sam Bulolo, Micheal Kyakula
Abstract This paper presents the results of a comprehensive study investigating the fire resistance of a novel steel–timber–concrete (STC) hybrid slab system. The research combines both an experimental approach to evaluate the structural performance of the STC slab under realistic fire conditions and a numerical approach to evaluate the thermal temperature gradients based on natural fire temperatures obtained from the experiment, Eurocode parametric curve (ECPC) temperatures, ISO 834 (International Organization for Standardization, 1999) temperatures and ASTM E119 (American Society for Testing and Materials, 2020). Experimental and numerical model parameters and specifications were informed by a baseline study on building designers and contractors utilising STC slab systems in Uganda, ensuring relevance to practical applications. A 4 × 3 m slab model was constructed, featuring a 75-mm concrete topping cast on an expanded metal lathe fixed to 100 × 100 mm Eucalyptus grandis beams spaced 600 mm centre to centre. These timber beams were simply supported on I-beams, which in turn were supported by SHS 75 × 75 x 5 mm columns. A natural fire scenario, as per Eurocode specifications, was implemented in a contained structure with burnt clay brick walls. The experimental investigation demonstrated that the STC slab could withstand a natural fire for over one hour while maintaining its load-carrying capacity. A numerical simulation was conducted using ABAQUS-CAE, a Finite Element Model program, to analyse the slab's response under both the experimentally obtained natural fire temperatures and the Eurocode parametric curve. The numerical results showed strong consistency with the experimental observations. Based on these findings, the STC slab successfully meets the East African code recommendations for an R60 fire rating, highlighting its potential for safe and sustainable construction.
Systems of building construction. Including fireproof construction, concrete construction
Abstract This paper presents an experimental study on the behavior of low-strength concrete columns confined with cold-formed steel under axial compression. The laboratory test specimens consist of four groups of rectangular concrete stub columns in the size of 130 $$\times $$ × 200 mm cross section and 300 mm height; the first group composes of the unconfined specimens, while the other three contain the confined specimens under 0%, 25% and 50% sustained axial loads. The jackets are made of two G450-grade channel cold-formed steel sections of 2.4 mm thickness welded together. No bonding material is used between the core concrete and the steel jacket. From the results, it is found that the cold-formed steel jacketing can increase the axial strengths of the unconfined concrete specimens by approximately 40-65%. The strength increase comes mainly from the confinement action, as only small axial deformation is detected in the jacket. Based on the given amount of prescribed preloads in this study, the presence of preload in the column does not have a significant effect on the increase in strength of the confined concrete columns. The measured strength enhancement ratio and the confinement ratio of the tested specimens are compared using five existing strength predictive equations. The performance of the unbonded cold-formed steel jacketing technique adopted in the stub columns is observed to closely conform with the predictive confinement model of the concrete-filled tubes.
Systems of building construction. Including fireproof construction, concrete construction
Jian-cheng Zhang, Xue-guo Jiang, Zi-kang Jia
et al.
Abstract The seismic behavior of steel reinforced ultra-high strength concrete (SRUHSC) composite frame was investigated through finite element analysis (FEA) modeling. A FEA model for the seismic analysis of the SRUHSC frame was first established and verified with test results. The numerical model was subsequently used to study the seismic performance of the SRUHSC frame, including the P-Δ skeleton curves, the stiffness degradation, the failure mode, the subsequence mechanisms of plastic hinges and the stress–strain distribution. Finally, a parametric study was carried out to investigate the effect of salient parameters on the behavior of the SRUHSC frame. It was found that with the increment of the concrete strength, yield strength of steel, and linear stiffness ratio of beam to column, the horizontal load-bearing capacity and the elastic stiffness of the structure were improved, but there was no significant effect on the ductility. With the increment of the volume stirrup ratio and structural steel ratio, the horizontal load-bearing capacity and the ductility of the structure were both improved. However, with the increment of the axial-load ratio, there was no obvious change in the elastic stiffness of the structure, but the horizontal load bearing capacity and the ductility of the structure decreased obviously. In addition, the accuracy of a concrete constitutive model in the different degrees of constraint for the SRUHSC frame proposed by the authors was verified with the FEA model.
Systems of building construction. Including fireproof construction, concrete construction
Abstract In this study, concrete specimens were fabricated based on domestically manufactured materials, and long-term exposure tests were conducted in a domestic coastal environment. This study analyzes the long-term compressive strength characteristics of concrete mixed with admixtures. The mixed materials used were divided into blast furnace slag and fly ash. The blast furnace slag and fly ash were, respectively, produced by replacing ~ 30% and ~ 15% of the cement. The compressive strength was measured at 28 day, 1 year, and 10 years of age and compared with that of ordinary concrete. In addition, the long-term compressive strength results obtained in this study were compared with those of concrete mixed with admixtures reported in the literature. The strengths of the ordinary specimen at 1 year and 10 years of age increased by ~ 10 MPa and ~ 22 MPa compared with those at 28 day of age. However, concrete mixed with admixtures yielded compressive strength increases of ~ 5 MPa and ~ 26 MPa at 1 year and 10 years of age, respectively, compared with those at 28 day of age. A comparison of the compressive strengths of concrete mixed with admixtures reported in the literature (based on age) and those obtained in this study showed that there was an initial strength difference in the range of 10–25%. However, the compressive strength at 10 years of age was almost similar to those reported in the literature with differences of less than 5%. These findings confirmed that when using pozzolanic admixtures, the development rate of the initial strength may vary owing to various factors; however, the long-term strength converges within a certain range.
Systems of building construction. Including fireproof construction, concrete construction
Abstract In typical steel fiber-reinforced concrete, the fibers are randomly distributed and oriented throughout the matrix, and a magnetic field can effectively align these randomly oriented fibers. To predict the extent to which the steel fibers contained in mortar can be aligned by a magnetic field, an analytical steel fiber orientation efficiency factor model was proposed as a function of the magnetic induction intensity and exposure time. To verify the applicability of the proposed model, experiments were conducted for various magnetic induction intensities and exposure times with normal mortars and mortars in which some or all the sand was replaced with steel slag. The experimental results demonstrate that the proposed model allows predicting the degree of alignment of steel fibers under magnetic fields. However, this model can only be applied to a normal mortar. In the case of mortar containing steel slag, it is confirmed that the steel slag, which is a ferrous material, reduces the magnetic induction intensity, reducing the degree of alignment of steel fibers in the mortar.
Systems of building construction. Including fireproof construction, concrete construction
Sergey M. Dymov, Maxim V. Vishchekin, Aleksandr M. Aleksandrov
et al.
The article considers theoretical and practical aspects of forest firefighter’s head protection. The main dangerous factors affecting the firefighter when extinguishing a forest fire are identified. Variants of possible practical solutions are given. The forecast for the development of the normative document of GOST R type for forest firefighter’s helmets and a model of a universal forest firefighter’s helmet is determined.
Systems of building construction. Including fireproof construction, concrete construction
Ivan V. Volkov, Evgeniy A. Zaplatov, Vladimir L. Zdor
et al.
The article discusses the features of tests to determine the response temperature, inertia and resistance to elevated temperatures of thermal fire detectors with response temperature over 160 ºС, that is, belonging to class H according to GOST 34698–2020 “Fire Detectors. General technical requirements. Test methods”.
It is noted that tests to determine the resistance of high-temperature fire detectors to elevated temperatures should be carried out in two stages, since such detectors, as a rule, are two-component, consisting of a sensitive element and a processing unit. These components have different elevated temperature limits, indicated in the technical documentation for specific types of detectors, at which their functionality remains intact.
It was concluded that it is necessary to amend the current edition of GOST 34698–2020.
Systems of building construction. Including fireproof construction, concrete construction
Seung-Hee Kwon, Jung-Soo Lee, Kyungtaek Koh
et al.
Abstract This study investigates the strain softening behavior of high-performance fiber-reinforced cementitious composites (HPFRCCs) under uniaxial compression. HPFRCC mixtures with different compressive strengths ranged from 120 to 170 MPa were prepared. The measurement method of feedback control on loading rate based transverse displacement was applied. Stress–strain and stress−inelastic displacement curves were plotted and analyzed with the results in the literature. It was found that the post-peak energy absorption of HPFRCC considering inelastic deformation was about 3–7 times higher than conventional concrete. Based on the experimental results in the present work, fitting models on post-peak stress–strain/−displacement curves were considering for different aspect ratios proposed.
Systems of building construction. Including fireproof construction, concrete construction
Ahmed M. Maglad, Walid Mansour, Bassam A. Tayeh
et al.
Abstract Fracture parameters of fiber concrete (FC) are currently a hot research area. Fracture mechanics is the field of solid mechanics that helps to study the type and propagation of cracks in materials. It uses methods of calculating the driving force on a crack and characterizes the material's resistance to fracture. Behavioral characteristics are determined by crack mouth opening displacement and the load–deflection method. This research identifies the fracture parameters of 33 notched simply supported beams made by recycled aggregate cement concrete with steel fiber. The recycled aggregate ratio in concrete has been altered to determine the effect on the mechanical and fracture properties. For determining fracture parameters, a 3-point bending single-edge notched fracture test was used. The results indicated that the steel fiber-reinforced concrete made with recycled aggregate showed similar performance and fracture characteristics compared to normal concrete. Thus, adding steel fibers to various concrete mixes considerably improved the fracture characteristics, while the brittleness was reduced with increased steel fiber content. Linear regression analysis also showed the accuracy of mechanical strength results as the value of R-square was close to unity. Displacement, ultimate load, brittleness (B), fracture toughness (K IC), crack mouth opening displacement (CMOD), fracture energy (G F), modulus of elasticity (E), and characteristic length (l ch), were determined for both conventional and recycled aggregate specimens. The “work of fracture"—by definition the formula—is the most reliable to calculate the fracture energy as the nonlinearity is related to the performance of FC.
Systems of building construction. Including fireproof construction, concrete construction
Hyun-Sub Yoon, Seung-Jun Kwon, Yong-Sik Yoon
et al.
Abstract Concrete sewage structures are difficult to maintain since they are constructed under the ground and their surfaces inside are exposed to various deteriorations such as acid and sulfate ingress. In this study, their repair costs were evaluated both deterministically and probabilistically considering the extended service life through repairing of conventional repair mortar and a newly developed bacteria repair material. Unlike the conventional deterministic method, the probabilistic manner evaluates repair cost continuously, taking into account variations in the initial service life and extended service life through repair. For the work, variations in the sulfate ion diffusion coefficient and protection parameters (cover depth and repair layer thickness) were obtained experimentally. Based on the target service life (60 years), the repair cost increased to 123% as the maintenance-free period (MFP) decreased by half, and decreased to 77% as the MFP increased to 1.5 times. As the extended service life through repair decreased by half, the repair cost increased to 180% due to the increasing repair frequency. When the repair-extended service life increased to 1.5 times, the repair cost decreased to 73%. Considering exterior sulfate concentrations (120 and 200 ppm) and entire sewage pipelines (3268 m), the bacteria repair material showed the lowest repair cost (1376 K$ and 1498 K$ with the deterministic and probabilistic method, respectively) since the repair-service life increased from 10.4 to 25.3 years and the number of repairs decreased from 9 to 4 due to the low diffusion coefficient of the bacteria repair material.
Systems of building construction. Including fireproof construction, concrete construction
Abstract Reinforced concrete structural walls (RCSWs) are one of the most efficient lateral force-resisting systems used in buildings, providing sufficient strength, stiffness, and deformation capacities to withstand the forces generated during earthquake ground motions. Identifying the failure mode of the RCSWs is a critical task that can assist engineers and designers in choosing appropriate retrofitting solutions. This study evaluates the efficiency of three ensemble deep neural network models, including the model averaging ensemble, weighted average ensemble, and integrated stacking ensemble for predicting the failure mode of the RCSWs. The ensemble deep neural network models are compared against previous studies that used traditional well-known ensemble models (AdaBoost, XGBoost, LightGBM, CatBoost) and traditional machine learning methods (Naïve Bayes, K-Nearest Neighbors, Decision Tree, and Random Forest). The weighted average ensemble model is proposed as the best-suited prediction model for identifying the failure mode since it has the highest accuracy, precision, and recall among the alternative models. In addition, since complex and advanced machine learning-based models are commonly referred to as black-box, the SHapley Additive exPlanation method is also used to interpret the model workflow and illustrate the importance and contribution of the components that impact determining the failure mode of the RCSWs.
Systems of building construction. Including fireproof construction, concrete construction
Abstract The technology of vibratory mixing has been applied to improve the compressive strength of cement-stabilized macadam (CSM). The aim of this study is to investigate the effect of vibration acceleration and cement dosage on the unconfined compressive strength and density of CSM. The mixtures with four cement dosages (2%, 3%, 4%, and 5%) were prepared by conventional mixing (0 g) and vibratory mixing (1 g, 2 g, and 3.5 g). The unconfined compressive strength was tested under different mixing methods. And the microstructure of CSM was analyzed by scanning electron microscope. The results indicate that samples using vibratory mixing have higher strengths, lower coefficient of variation, and denser microstructures, compared with the conventional compulsory mixing. Compared with 15% in conventional mixing, the strength variable coefficient of CSM is less than 10% in the vibratory mixing method. As the cement dosage and the vibration acceleration increase, the unconfined compressive strength increases. However, cement dosage has a more significant influence on improving the unconfined compressive strength than the mixing method. With the increase of every 1% in cement dosage, the 7-day strength of conventional mixing and in vibratory mixing average increased by 59% and 38%, respectively. However, the maximum improvement rate of the UCS value is 20–56.7% when vibration acceleration increased from 0 to 1 g. Especially when cement dosage is high, the effect of vibratory mixing on improving strength is limited. Besides, vibratory mixing reduces the original cement dosage by over 1.6% with the qualified unconfined compressive strength at vibration acceleration of 2 g, which is recommended in construction practice.
Systems of building construction. Including fireproof construction, concrete construction
Statement of the problem. Low-rise construction is characterized by a relatively low cost and a possibility of forming effective insulating structure shells. Frames and massive walls are used as load-bearing structures, it is also possible to use concrete. Taking into account the current realities, the most relevant is the orientation of systems to the use of domestic materials including those capable of functioning effectively in harsh climatic conditions. Results. It was established that the properties of polyethylene foam and products based on it make it possible to recommend this material both in facade and roof insulation systems as well as in those in contact with the ground. It was found out that polyethylene foam causes almost no changes in the properties under freezing conditions down to minus 70 °C and in the range of sign-variable temperatures from -60 to +70 °C. With prolonged contact with water or water-saturated soil, the properties of the material are also stable. Conclusion. The use of rolled polyethylene foam is promising both in terms of the properties of the material itself and in view of the possibility of forming seamless insulating shells. The formation of seamless insulating shells creates practically impenetrable heat-vapor- and water-insulating barriers along the perimeter of the insulated object. The study of the properties of polyethylene foam in various operating conditions and insulation systems was the goal of the research described in the article. Methods approved by domestic standards were adopted as the basis for the research.