Hasil untuk "Systems of building construction. Including fireproof construction, concrete construction"

Oleg V. Streltsov, Evgeny V. Bobrinev, Elena Yu. Udavtsova et al.

The issues of occupational safety and health in fire divisions have been studied. Regulatory documents regulating the activities of fire personnel and their safety have been reviewed. The structure of injury hazards of the operational staff of the FPS of the Ministry of Emergency Situations of Russia is analyzed. The main causes of injuries among FPS operational staff are the following: the risk of falling from a height – 24 %; the risk of falling due to loss of balance – 15 %; the risk of ground structure collapse, including the risk of exposure to fragments from collapsed buildings, structures, etc. – 12 %. There are the following main causes of fatalities among FPS operational staff: the risk of ground structure collapse – 24 %, the risk of sudden disruptions to normal conditions, including the risk of mental stress – 13 %, the risk from contact with highly hazardous substances – 12 %.

Yan Qiao, Weihua Zhang, Jinsheng Cheng et al.

Abstract This study investigates the bond–slip behavior of newly poured concrete and reinforcement bars under traffic-induced vibrations in bridge widening. Center pull-out tests were conducted on C60 concrete specimens with HTRB400 steel bars to examine the effects of bar diameter, vibration frequency, amplitude, and anchorage length. Based on the experimental data, the bond–slip constitutive model of newly poured concrete-reinforcement bars was developed. Test results indicated that larger bar diameters reduced ultimate bond stress and relative slip. Specimens with 8 d (d is the diameter of reinforcement bar) anchorage length exhibited lower bond strength than those with 5 d. Vibration amplitude had minimal influence on bond behavior, while higher frequencies decreased bond stress but increased slip. The constitutive model can provide a reliable prediction of bond behavior under dynamic disturbances. The findings offer practical insights for bridge widening projects, ensuring structural integrity under traffic loads.

S. I. Haruna, Han Zhu, Yasser E. Ibrahim et al.

Abstract Polyurethane-based polymer concrete (PUC) has become a popular material for pavement repair. However, its compressive strength (f c) is essential to achieve effective repair work. This study predicted the compressive strength and evaluated the non-destructive test (NDT) properties of the PUC mixtures, prepared by mixing aggregate-to-polyurethane (PU) at 80/20, 85/15, and 90/10 ratios by weight. The experimental datasets from mechanical and NDT tests were utilized to train machine learning (ML) models, including multilinear regression (MLR), artificial neural network (ANN), support vector machine (SVM), Gaussian regression process (GPR), and stepwise regression (SWR) models for estimating the f c. Moreover, scanning electron microscopy (SEM) was employed to evaluate the microstructure of PUC. Feature selection tools were used to explore optimal input variables for estimating the (f c) of the PUC samples. The PUC-10 specimen revealed a maximum ultrasonic pulse velocity (UPV) value of 3.05 km/h. The microstructure analysis shows micro-voids with crack propagation between the aggregate and PU binder in the specimen containing 10% PU after testing. All the developed models showed high prediction accuracy. In addition, SVM outperformed other models at the training phase with R 2 values of 0.9614, and ANN demonstrated the highest performance at the testing phase with R 2 values of 0.9502.

Nima Khodadadi, Emad Golafshani, Hossein Roghani et al.

Abstract Glass fiber-reinforced polymers (GFRP) are widely applied to enhance the strength of concrete columns due to their lightweight and high-strength characteristics. This study presents the development of a metaheuristics-guided machine learning (ML) model for predicting the compressive strength (CS) of GFRP-confined concrete columns (GFRP-CC). Traditional predictive models, primarily based on Linear or nonlinear regression, are often limited by narrow data scopes and methodological constraints. To address this gap, we propose an innovative ML model, leveraging an extensive database of 319 experimental results compiled from 41 peer-reviewed articles spanning 1991–2024. Using an artificial neural network (ANN) combined with five metaheuristic algorithms, the study aims to reduce the dependency on costly and time-intensive laboratory testing. The model development considered eight key parameters: diameter of the compression member (D), height of the compression member (H), compressive strength of unconfined concrete (f′ co), GFRP reinforcement ratio (ρ f ), tensile modulus of elasticity of GFRP (E f ), ultimate tensile strength of GFRP (f f ), nominal thickness of GFRP reinforcement (t f ), and number of GFRP layers. Among the tested models, the Stochastic Paint Optimizer (SPO)-ANN model demonstrated the highest accuracy, achieving a coefficient of determination of 0.9630 with minimal error values. To ensure transparency and interpretability, SHapley Additive exPlanations (SHAP), Olden methodologies, and Partial dependence were employed to elucidate the relative importance of contributing features. Critical factors influencing the CS of GFRP-CC included the thickness of GFRP reinforcement, tensile strength, and layer count. A user-friendly graphical interface was developed to facilitate practical adoption, enabling researchers and practitioners to model CFRP-CC compressive strength efficiently. This work represents a paradigm shift in concrete research, emphasizing sophisticated, data-driven methodologies that bridge the gap between experimental data and practical applications.

Tarik S. El-Salakawy, Amr A. Gamal, Mohamed Essam Sayed

Abstract The use of hybrid GFRP and steel bars as main reinforcement increases the flexural capacity of T-section concrete beams and reduces ductility. Adding recycled rubber to the concrete mix would further enhance the ductility of the hybrid system. Evaluation of the concrete's flexural capacity and ductility is the main goal of the current investigation using normal concrete (NC) and rubberized recycled concrete (RRC). Eight T-beams have been experimentally investigated in this research, two beams were reinforced with steel bars and GFRP bars with zero percentage of crumb rubber (C.R). The remaining beams were reinforced with different combinations of GFRP and steel bars with rubberized concrete mixes with partial substitution of sand with recycled crumb rubber by (0%, 7.5%, 10%, and 12.5% replacements by volume) particle size 1.0 to 2.0 mm. The ductility index for the tested hybrid rubberized T-beams (HRTB) BRH1, BRH3a, BRH5, BRH2, BRH4, and BRH6, were higher than BH1 and BH2 by 28.2%, 35.47%, 65.38%, 23.76%, 30.04%, and 56.95% indicating that increasing the percentage of C.R. has a direct effect on increasing the ductility index. The ultimate failure load for the tested HRTB BRH1, BRH3a, and BRH5, decreased by 11.68%, 14.29%, and 17.47% compared to the hybrid T-beam BH1. The energy dissipation decreased for HRTB BRH1, BRH3a, BRH5, BRH2, BRH4 and BRH6 by 7.88%, 12.36%, 17.17%, 8.12%, 12.96%, and 18.28 compared to hybrid T-beams BH1 and BH2. This indicates that the existence of the very weak C.R. was not able to dissipate the energy properly within the concrete matrix. Good agreement was found between the numerical model and experimental results in terms of crack pattern, ultimate loads and deflections.

Jun-Jie Zeng, Xin-Chao Lin, Sheng-Zhao Feng et al.

Abstract Ultra-high performance engineered cementitious composite (UHP-ECC), which is known for its exceptional compressive strength, tensile strength, and ductility, has been emerged as a promising option for repairing and strengthening reinforced concrete (RC) structures. The bond between UHP-ECC and normal concrete is the key issue for the material to be successfully implemented. This paper presents an experimental investigation focused on understanding the tensile and shear behavior of the bonding interface between UHP-ECC and concrete. A total of 78 specimens were prepared and tensile splitting tests and push-out tests were carried out. The study examined key parameters including the strength of the concrete substrate, the roughness of the interface, and the moisture condition at the interface. Various failure modes are observed in the specimens under tensile splitting force and direct shear force, and it is found that the influence of the key parameters varied depending on the type of failure mode. In specimens experiencing full interface debonding or interface failure combined with substrate cracks, the roughness of the interface and the moisture degree have a significant impact on the tensile and shear strength. Conversely, in specimens with full substrate disruption, the strength of the substrates plays a more significant role. Additionally, the study reveals that the grooving treatment is highly effective in improving the shear strength of the interface, but its impact on enhancing the tensile strength is comparatively less pronounced. Prediction models for the tensile and shear strength of the interface are established and verified against the test results. The proposed models provide valuable insights into the behavior of the UHP-ECC to concrete interface and can aid in predicting its performance in practical applications.

Yoseok Jeong, Ilkeun Lee, Jaeha Lee et al.

Abstract As the number of heavy vehicles on the road continues to increase, collisions involving heavy vehicles and concrete median barriers (CMB) occur more frequently than in the past. Consequently, there is a growing need for research into more stringent design standards and improvements to the current CMB and their performance under harsh conditions. High-performance CMB is required to in order to withstand such conditions. This paper presents the results of numerical simulations and full-scale field tests to develop a high-performance CMB. To facilitate the development of the high-performance CMB, the concept of a deformable CMB was applied to the rigid CMB. A new apparatus called the shock absorber composed of dowel bars surrounded by empty space were introduced to make the rigid CMB deformable. In order to prevent local failure at the top of the barrier from a sudden high increase in impact energy, the deformable CMB was strengthened by adding reinforcements and widening the top based on the results of numerical simulations. The full-scale field tests were conducted on the proposed deformable CMB and took into account three appraisal areas: (1) structural adequacy, (2) occupant risk, and (3) vehicle trajectory after collision. The results of these tests showed that the deformable CMB contained and redirected the vehicle without allowing it to penetrate or override the deformable CMB. No detached elements, fragmentation, or other debris from the barrier were present. Therefore, the proposed high-performance CMB fulfilled all of the requirements of the crash test guideline.

Pawel Sikora, Ahmed M. El-Khayatt, H. A. Saudi et al.

Abstract This work examines the influence of iron oxide nanoparticles (Fe3O4 NPs) on neutron and gamma-ray radiation shielding characteristics of Portland cement paste. Experimental evaluations were supplemented with theoretical studies using NXCom program. Portland cement pastes with 5, 10, 15, 20, and 30 wt% of nanomagnetite cement replacement were produced. Moreover, rheological, early strength development, compressive strength, and mercury intrusion porosimetry (MIP) tests were performed. The results showed that increasing the amount of Fe3O4 NPs in a mix leads to a gradual increment in measured viscosity and yield stress. High nano-Fe3O4 content substantially impeded the early strength development process and led to a decrement in the 7- and 28-day compressive strength of cement paste. The MIP studies exhibited a gradual increment in total porosity, and average pore volume, as nano-Fe3O4 content was increased. All the macroscopic cross-sections of slow, fast and thermal neutrons constantly increased as a result of the addition of magnetite nanoparticles, with their variations being markedly linear. Similarly, gamma attenuation test results indicated that the addition of Fe3O4 powder enhances the shielding capability of paste in the energy range of interest (0.08–2.614 MeV). In conclusion, Fe3O4 nanoparticles can be successfully used in producing lead-free cementitious composites with improved gamma-ray and neutron shielding properties. However, certain drawbacks related to an increment in matrix porosity and thus a decrement in mechanical performance should be taken into account.

Sherif H. Al-Tersawy, Sahar E. Zakey, Rasha A. El-Sadany et al.

Abstract The main objective of the present work is to evaluate using alkaline wastewater from pot factories (recycled NaOH solutions with variant concentrations and pH values) along with waste powders possessing pozzolanic properties, such as supplementary cementitious materials and stone waste dust in concrete under normal manufacturing conditions. An extensive analysis of the chemical components and the physical properties of the used materials was achieved. Both supplementary cementitious materials and stone waste dust materials were used as 0%, 10%, 20%, or 30% partial cement replacements using either tap water or alkaline wastewater to make samples for physical, mechanical, and microstructure testing. Thermodynamic modeling was used to evaluate the effect of the flushed alkaline industrial water and the powders on the hydration products. The results showed an increase in the workability of the mixes made with alkaline wastewater, an increase in water absorption for samples made with alkaline wastewater at the age of 28 days, and a relative decrease in compressive strength at 3 and 28 days, respectively. Despite the reduction in mechanical strength, most samples made with alkaline wastewater and 10%, 20% supplementary cementitious materials, or stone waste dust materials gave an accepted concrete grade. The microstructure analysis showed a slight change in pores distribution, pores values, and hydration products at 3 and 28 days. The thermodynamic analysis provided insight into data on the effect of supplementary cementitious materials, stone waste dust materials, and alkaline wastewater on hydration products. Finally, the combination of these wastes in concrete production showed satisfactory conclusions.

Maxim V. Vishchekin, Sergey M. Dymov , Dmitry Yu. Rusanov et al.

The article discusses the issue of application of fire escape chutes and rigid fire escape chutes to rescue people from low heights in case of fire. These rescue means are compared according to the main characteristics. Recommendations for practical use are indicated.

Siyao Wang, Mei-Ling Zhuang, Xiang Xue

Abstract This study presents experimental and numerical methods to reveal concrete structures’ crack propagation and intersection laws under static and dynamic loads. Firstly, a numerical simulation method was established using the user-defined material subroutines to solve the free crack surface contact problem of concrete structures. Secondly, three-point bending tests of concrete beams containing double cracks of different approaching angles were carried out based on the digital image correlation (DIC) technology to study the intersection and propagation of cracks. Finally, the fracture processes of double-crack concrete beams and concrete gravity dams with and without a longitudinal crack were simulated and analyzed under static and dynamic loads. The numerical results were compared with the test results to verify the effectiveness and accuracy of the proposed method in simulating crack intersection and propagation in concrete structures. Results indicate that the crack intersection affects the fracture path of concrete structures, weakens their bearing capacity, and accelerates the failure of the structures. The proposed simulation method provides an effective technical approach for crack propagation prediction and safety evaluation of engineering structures.

Jorge E. Egger, Fabian R. Rojas, Leonardo M. Massone

Abstract Low cycle fatigue life of high-strength reinforcing steel bars (ASTM A706 Grade 80), using photogrammetry by RGB methodology is evaluated. Fatigue tests are performed on specimens under constant axial displacement with total strain amplitudes ranging from 0.01 to 0.05. The experimental observations indicate that buckling of high-strength reinforcing bars results in a damaging degradation of their fatigue life performance as the slenderness ratio increases, including an early rebar failure as the total strain amplitude increases since it achieves the plastic range faster. In addition to this, the results show that the ratio of the ultimate tensile strength to yield strength satisfies the minimum of 1.25 specified in ASTM A706 for reinforcement. On the other hand, the RGB methodology indicates that the axial strains measured by photogrammetry provide more accurate data since the registered results by the traditional experimental setup do not detect second-order effects, such as slippage or lengthening of the specimens within the clamps. Moreover, the RGB filter is faster than digital image correlation (DIC) because the RGB methodology requires a fewer computational cost than DIC algorithms. The RGB methodology allows to reduce the total strain amplitude up to 45% compared to the results obtained by the traditional setup. Finally, models relating total strain amplitude with half-cycles to failure and total strain amplitude with total energy dissipated for multiple slenderness ratios (L/d of 5, 10, and 15) are obtained.

Olga D. Ratnikova, Natalia V. Peregudova, Pavel P. Kononko et al.

The article analyzes the normative legal documents in the field of organizing voluntary activities. The analysis of legislation and organizational and methodological documents, which provide a unified approach to the organization of the activities of voluntary organizations, allows the Russian Emergencies Ministry to coordinate and plan voluntary activities most effectively.

Maxim V. Vishchekin, Sergey M. Dymov, Dmitry Yu. Rusanov et al.

The article discusses the historical perspective of changing the normative approach to periodic inspection of equipment for rescue from height. The depth of survey does not exceed 37 years. The scope of survey is limited by the departmental affiliation to fire service.

Na Zhang, Jian Zhou, Guo-wei Ma

Abstract Strain-hardening cementitious composites (SHCCs) reinforced with both basalt and steel fibers are expected to possess the advantages of both fiber materials and exhibit desirable mechanical properties. In this study, we experimentally investigated the dynamic mechanical properties of an SHCC reinforced with inorganic fibers of basalt and steel for different strain rates (101 to 102 s−1) using a 50-mm-diameter Split-Hopkinson pressure bar. The effects of the strain rate on the dynamic compressive strength and dynamic splitting strength as well as the dynamic increase factor and energy absorption characteristics of the SHCC were analyzed. The results showed that all the mechanical indices increased with an increase in the strain rate. The dynamic increase factors of the compressive strength and splitting strength increased linearly with the decimal logarithm of the strain rate. Further, the addition of the basalt and steel fibers resulted in a significant increase in the strain-rate sensitivity of the dynamic mechanical behavior of the SHCC, with the effect of the steel fibers being more pronounced than that of the basalt fibers. Although the basalt and steel fibers had varying effects on the strain-rate sensitivity of the dynamic mechanical behavior of the SHCC based on the fiber content, there were significant positive correlations between the type and content of the fibers used and the strain-rate sensitivity.

Yujing Lv, Wenhua Zhang, Fan Wu et al.

Abstract The previous researches on the degradation process of concrete under sulfate attack mainly focus on non-damaged concrete. It may lead to an excessive evaluation of the durability of the structure, which is detrimental to the safety of the structure. In this paper, three different damage degrees of concrete specimens with non-damaged (D 0) and initial damage of 10% (D 1) and 20% (D 2) were prefabricated and subjected to sulfate attack and wetting–drying cycles. With the increase of sulfate attack cycles (0, 30, 60, 90, 120, 150 cycles), the changes in mass loss, relative dynamic modulus of elasticity, and the stress–strain curve were studied. The results show that the mass of the D 0 specimen had been increasing continuously before 150 sulfate attack cycles. The mass of D 1 and D 2 had been increasing before 60 cycles, and decreasing after 60 cycles. At 150 cycles, the mass loss of D 0, D 1, D 2 were − 1.054%, 0.29% and 3.20%, respectively. The relative dynamic modulus of elasticity (RDME) of D 0 specimen increases continuously before 90 sulfate attack cycles. After 90 cycles, the RDME gradually decreases. However, for D 1 and D 2 specimens, the RDME began to decrease after 30 cycles. The damage degree has an obvious influence on the compressive strength and elastic modulus. For the D 0 specimen, the compressive strength and elastic modulus increased continuously before 90 cycles and decreased after 90 cycles. The compressive strength and elastic modulus of D 1 and D 2 specimens began to decrease after 30 cycles. The stress–strain curves of concrete with different initial damage degrees were established, and the fitting results were good. Finally, based on the analysis of experimental data, the degradation mechanism of concrete with initial damage under the sulfate wetting–drying cycle was discussed.

Xiang-guo Wu, Xiao-kai Chen, Shi-yan Yu et al.

Abstract The proper assembly of underground precast concrete structures is often critical in the construction of underground structures. In particular, interfacial waterproofing between precast concrete segments is a key factor influencing use, safety, and life span. Current practice is to incorporate waterproofing rubber strips in the design. During the installation process, compressive stress is applied to the strip by post-tensioning to achieve performance. For this paper, lateral constraint compression tests were carried out on composite rubber seal strips that utilize putty. Special waterproofing and sealing test devices were designed to investigate corresponding relationships between water pressure and compressive stress (or strain). A relationship between water resistance pressure and compression stress and strain of the putty-based composite rubber strip was proposed based on the series tests and the control target of the minimum compression strain of the putty composite rubber strip was then suggested. Finally, full-scale waterproofing tests on tunnel joints were conducted. The experimental results provide a scientific reference for the engineering application and design of composite sealing rubber strips putty for underground post-tensioned precast concrete structures.

Han-Soo Kim

Abstract Differential axial shortening (DAS) in a tall building can produce adverse effects on its structural and nonstructural elements. Therefore, DAS should be considered in the design phase and appropriate measures should be taken to reduce its unfavorable effects. In this study, the utilization of outriggers, which has been originally designed to reduce lateral displacements, is proposed to reduce DAS. The optimum locations of outriggers that minimize the maximum DAS are determined by an optimization method. The integrality requirement posed by the outrigger locations, which should be given as integer numbers, is resolved by piecewise quadratic interpolation with discrete analysis results. The proposed optimization method stably yielded optimum solutions for a total of 24 design cases. The optimum design results show that although the maximum DAS decreases as the number of outriggers increases, the maximum DAS does not decrease significantly when the number of outriggers is greater than 2.

Sahyeon Lee, Seung Yup Jang, Chan Young Kim et al.

Abstract The rapid-hardening method employing the injection of calcium sulfoaluminate (CSA) cement mortar into voids between preplaced ballast aggregates has recently emerged as a promising approach for the renovation of existing ballasted railway tracks to concrete tracks. This method typically involves the use of a redispersible polymer powder to enhance the durability of the resulting recycled aggregate concrete. However, the effects of the amount of polymer on the mechanical and durability properties of recycled ballast aggregate concrete were not clearly understood. In addition, the effects of the cleanness condition of ballast aggregates were never examined. This study aimed at investigating these two aspects through compression and flexure tests, shrinkage tests, freezing–thawing resistance tests, and optical microscopy. The results revealed that an increase in the amount of polymer generally decreased the compressive strength at the curing age of 28 days. However, the use of a higher polymer ratio enhanced the modulus of rupture, freezing–thawing resistance, and shrinkage resistance, likely because it improved the microstructure of the interfacial transition zones between recycled ballast aggregates and injected mortar. In addition, a higher cleanness level of ballast aggregates generally improved the mechanical and durability qualities of concrete.

Hugo Biscaia, Noel Franco, Carlos Chastre

Abstract The durability performance of stainless steel makes it an interesting alternative for the structural strengthening of reinforced concrete. Like external steel plates or fibre reinforced polymers, stainless steel can be applied using externally bonded reinforcement (EBR) or the near surface mounted (NSM) bonding techniques. In the present work, a set of single-lap shear tests were carried out using the EBR and NSM bonding techniques. The evaluation of the performance of the bonding interfaces was done with the help of the digital image correlation (DIC) technique. The tests showed that the measurements gathered with DIC should be used with caution, since there is noise in the distribution of the slips and only the slips greater than one-tenth of a millimetre were fairly well predicted. For this reason, the slips had to be smoothed out to make it easier to determine the strains in the stainless steel and the bond stress transfer between materials, which helps to determine the bond–slip relationship of the interface. Moreover, the DIC technique allowed to identify all the states developed within the interface through the load–slip responses which were also closely predicted with other monitoring devices. Considering the NSM and the EBR samples with the same bonded lengths, it can be stated that the NSM system has the best performance due to their higher strength, being observed the rupture of the stainless steel in the samples with bond lengths of 200 and 300 mm. Associated with this higher strength, the NSM specimens had an effective bond length of 168 mm which is 71.5% of that obtained for the EBR specimens (235 mm). A trapezoidal and a power functions are the proposed shapes to describe the interfacial bond–slip relationships of the NSM and EBR systems, respectively, where the maximum bond stress in the former system is 1.8 times the maximum bond stress of the latter one.