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

Yanzhong Ju, Tong Shen, Dehong Wang

Ji-Hyun Kim, Andres Salas-Montoya, Young-Chan Kim et al.

Abstract The aim of this research is to propose a novel technique to improve the performance of structural concrete member using recycled aggregate by creating a core–shell hybrid concrete instead of intermixing natural aggregate concrete with recycled aggregate concrete. The technique involves layered casting of a recycled aggregate concrete with natural aggregate concrete, either as a core or as a shell, to prove whether this core–shell hybridization approach has a potential to facilitate the utilization of recycled aggregate for structural concrete. Various core–shell combinations were made using w/c 0.3 and 0.5 concretes, and compressive strength, elastic modulus, and chloride ion diffusivity of the hybrid specimens were measured. This paper also investigated the effects of two-stage mixing approach on properties of recycled aggregate concrete and hybrid concrete. It was found that placing stronger NAC at the outer shell provided higher compressive strength and elastic modulus of core–shell hybrid concrete. Placing NAC at the outer shell also provided lower chloride ion diffusivity as it acted as a diffusion barrier. It is recommended to place a stronger and more durable natural aggregate concrete in the shell to have better mechanical properties and durability. A synergetic effect of hybridization was observed from elastic modulus, not from the compressive strength. It was also found that compressive strength and elastic modulus of core–shell hybrid concrete were successfully estimated using those of control concrete specimens.

Fahimeh Yavartanoo, Chang-Soo Kim, Thomas H.-K. Kang

Abstract Using fiber-reinforced polymer (FRP) has gained widespread acceptance as an effective method for strengthening masonry walls in seismic zones. This research focuses on analyzing the in-plane behavior of dry-stack masonry walls reinforced with embedded FRP bars, providing a cost-efficient solution. Three reinforcement layouts, including horizontal, vertical, and diagonal, each with varying numbers of bars, were investigated. Alongside various FRP materials such as carbon, aramid, and glass fibers, the study also encompasses titanium and stainless steel bars to ensure a comprehensive assessment. Two-dimensional nonlinear finite element models were proposed using ABAQUS software, employing a micro-modeling strategy to investigate the performance of retrofitted walls. The modeling approach was validated by comparing it with existing experimental data. The lateral response of the walls under vertical loads was evaluated using pushover and cyclic analysis methods for different arrangements and materials of bars to find the most efficient model. The findings indicated that vertically aligned S-Glass FRP outperforms other models in enhancing wall overstrength, stiffness hardening, and energy dissipation capacity.

Jian-Hua Jiang, Fu-Liang Ma, Si-An Chen et al.

Abstract To promote the resource utilization of construction solid waste and realize the sustainable development of building materials, it is an effective way to develop the recycled aggregate concrete. This study first examined the pretreatment effect of 5% water glass solution on recycled coarse aggregates (RCAs) by soaking them for varying durations. Then, the dynamic compressive performance tests were conducted on the pretreated recycled coarse aggregate concrete (PRCAC) using the split Hopkinson pressure bar device, considering the effects of the soaking duration of RCAs, the incorporation ratio of pretreated RCAs (PRCAs), and the calcium leaching. The results indicate that the water glass treatment improves the pore structure of RCA, reducing its water absorption, crushing index, and porosity. After 12 h of soaking in the water glass solution, the water absorption, crushing index, and porosity of RCA decreased by 13.7%, 11.3%, and 11.2%, respectively. Dynamic compressive strength and dynamic increase factor (DIF) of PRCAC are sensitive to strain rate, and increase with the increase of the strain rate. The dynamic compressive strength of PRCAC exhibits a positive correlation with the incorporation ratio of PRCAs and a negative correlation with the duration of calcium leaching. Additionally, the sensitivity of PRCAC to strain rate is negatively correlated with the incorporation ratio of PRCA and positively correlated with leaching duration. As the soaking duration of RCAs increases, the dynamic compressive strength of PRCAC first increases and then decreases. The degree of strength degradation of PRCAC due to calcium leaching decreases as the soaking duration of RCAs increases. The above research findings contribute to the improvement of the performance of recycled concrete and the correct evaluation of its dynamic mechanical properties.

Ahmed M. Yousef, Mohamed E. El Madawy, Karim Abd El-Hady

Abstract Ledge beams are employed as the primary girders in numerous existing bridges, parking garages and high-rise buildings. No experimental investigations have been reported on Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) ledge beams yet. This paper presents an experimental and numerical program to investigate UHPFRC ledge beams with various ratios of ledge tie reinforcement. The experimental program included eight full-scale ledge beams constructed from UHPFRC with concrete cube compressive strength of 146.1 MPa. The results revealed that failure modes of tested specimens depend mainly on ledge tie reinforcement. Increasing the ledge tie reinforcement ratio in specimens led to a significant enhancement of the ultimate strength and overall stiffness. The presence of ledge ties at the minimum ratio specified by the codes contributed to an approximate 65.0% increase in the ultimate load. The estimated failure modes for specimens using (AASHTO–LRFD 2020) and Strut-and-Tie Model (STM) according to (ACI 318-2019) were identical with experiments, while the predictions of (PCI 2020) were not identical with 50.0% of the experimental results. The predictions of ultimate strength of specimens based on the equations of (PCI 2020) and STM according to (ACI 318-2019) were conservative. A three-dimensional numerical model was proposed to predict the complete response of the tested UHPFRC ledge beams.

Ahmed Hamoda, Mohamed Emara, Mizan Ahmed et al.

Abstract Reinforced concrete (RC) deep beams often necessitate openings in their web to facilitate building utilities. These openings compromise the shear resistance of the beams and, therefore, should be strengthened in their critical shear zone. This study proposes externally bonded high-performance concrete (HPC) mortars layers strengthened with steel wire mesh to strengthen the shear capacity of high-strength RC deep beams with openings within their shear span. To facilitate this, an experimental program consisting of testing ten high-strength RC deep beams was carried out. The test parameters include the effects of opening, types of HPC mortars, namely, engineered cementitious composites (ECC) and ultra-high-performance fiber-reinforced concrete (UHFRC) mortars, the configuration of the opening (circular, square), and the size of the openings. Two strengthened beams were fabricated without openings, while the remaining incorporated various opening configurations. The results demonstrated the shear performance of the beams increases using the proposed strengthening technique. The increases in ultimate load capacity ranged from 5 to 68%, elastic stiffness improved between 8 and 97%, and energy absorption capacity enhanced from 7 to 127%. Increasing the opening size reduces the strength, stiffness, and energy absorption capacity of the beam. Furthermore, beams with circular openings exhibited better performance than their square counterparts. The specific design and strengthening strategies employed effectively improve their load-bearing capacity concerning the opening size ratio. Application of the HPC mortars with higher compressive and tensile strength further results in the improvement of their shear performance. In addition, a finite element model (FEM) was developed to simulate the performance of tested beams and compare the accuracy of the FEM against the test results. It was found that the adaptation of the Concrete Damage Plasticity (CDP) model with the parameters adopted in this study can accurately predict the behavior of the tested beams. An average error of only 4% was obtained for the experiment-to-predicted load for cracking and ultimate load. Furthermore, based on the parametric study performed on beams with circular openings strengthened with ECC layers, it is proposed that for practical design purposes the thickness of the ECC layer to the thickness of the beam (t ECCC/t beam) ratio should not exceed 0.32.

Alevtina V. Novikova, Anna N. Varlamkina, Artur N. Katargin et al.

The article considers the main issues of improving the provisions of the technical regulations of the Eurasian Economic Union «On requirements for fire safety and fire extinguishing equipment» (EAEU TR 043/2017), the development and implementation of interstate standards in development of the provisions of EAEU TR 043/2017. The problems of harmonization of requirements between regulatory documents in the field of construction and fire safety are studied. There is provided the information on the development of national standards and sets of rules in development of the provisions of Federal Law 123-FZ.

Yan Chen, Guangjing Xiong, Xiaohua Zhao

Senghong Khol, Soo-Yeon Seo, Hai Van Tran et al.

Abstract Shear strengthening of reinforced concrete beams using near-surface mounting (NSM) method with fiber-reinforced polymer (FRP) strips is more effective because of improved bond strength, better fire resistance and high maintainability. However, the surface preparation for NSM method is a difficult process where the beam–slab corner is not accessible by the rotary blade of the groove-making equipment. Consequently, the application of NSM method becomes more difficult to apply. Therefore, in this study, the effect of reducing in NSM length on the shear strength has been investigated by reinforcing only a part of the height, not the entire web of beam, referred to as the partial-length NSM method (PLNSM). Half scaled five RC T-beams were made and tested under symmetrical four-point static loading system. All except one was strengthened in shear in which the effect of reduced NSM length was balanced by inclining the partial-length NSM strips (IPLNSM). Furthermore, to mitigate the detrimental effect of reduced lengths of NSM strips, the retrofitting was enhanced by additional externally bonded reinforcement (EBR) method using CFRP sheets. The results showed that there was no significant negative effect of reduced NSM length on the strength of the strengthened specimens, and by providing inclined NSM strips, significant improvement in the strength was observed. Additionally, the hybrid approach combining the inclined partial length NSM (IPLNSM) and EBR method showed improvement in strength and deflection capacity. Lastly, when compared with the currently available design procedures, it was found that the available formulation can predict the design strength of PLNSM and IPLNSM reinforcement, thus making them a viable option for retrofitting reinforced concrete beams.

Tesfaye Alemu Mohammed, Yonathan Muche Kasie, Eleyas Assefa et al.

Abstract Concrete’s weak tensile strength renders it susceptible to cracking under prolonged loads, leading to reduced load-bearing capacity and reinforcing bar corrosion. This study investigates the effectiveness of microbial-based self-healing in high-strength concrete, focusing on two bacterial strains: Sporosarcina koreensis and Bacillus. Results demonstrate significant enhancements in micro- and macro-physical properties of high-strength bacterial concrete with Bacillus flexus and S. koreensis, surpassing the control. Bacillus flexus-infused concrete exhibits a remarkable 21.8% increase in compressive strength at 7 days and 11.7% at 56 days. Similarly, S. koreensis-treated concrete shows 12.2% and 7.4% increases at 7 and 56 days, respectively. Enhanced crack healing occurs due to calcite precipitation, confirmed by X-ray diffraction and scanning electron microscopy. Both bacterial strains achieve crack closure within 42 days, with widths of 259.7 µm and 288.7 µm, respectively. Moreover, bacterial concrete from these strains excels in durability against water, acid, and salt exposure, surpassing control concrete. These findings emphasize microbial-based self-healing’s potential in high-strength concrete, providing a practical strategy to enhance structural resilience and extend concrete infrastructure lifespan.

Zahid Hussain, Jesús D. Ortiz, Seyed Arman Hosseini et al.

Abstract The current provisions for development length in the ACI 440.11 code disregard the confinement effect provided by stirrups on the bond strength of longitudinal bars and require splice lengths that pose implementation challenges. Given the significant improvement in GFRP material properties, this study investigated the bond strength of sand-coated GFRP bars and proposed a new factor to include the effect of stirrup confinement on the bond-strength provisions. The experimental program involved 16 GFRP-reinforced concrete (RC) beams having a width of 300 mm, and depth 440 mm, consisting of two repetitions for every configuration, subjected to four-point loading. The test parameters comprised lap-splice length and stirrup spacing in the lap-spliced zone. Out of 16 GFRP-RC beams, two beams were reinforced with two M16 (No. 5) continuous bars and six with varying lap-splice lengths [i.e., 40, 60, and 80 bar diameters (db)] without confining stirrups. To evaluate the effect of confining stirrups, eight beams were reinforced with two M16 (No. 5) lap-spliced longitudinal bars (i.e., 40 and 60 db) and M13 (No. 4) stirrups spaced at 100 mm (4 in.) and 200 mm (8 in.) center-to-center. Based on experimental results, stirrup confinement clearly increased the bond strength, reduced longitudinal bar slippage, and increased splitting stress. The beams with a splice length of 60 db and stirrups on 100 mm (4 in.) centers achieved 57% higher capacity than those with the same lap-splice length but without stirrups. Further, the ACI 440.11 equation overestimated the bond strength of sand-coated GFRP bars but yielded conservative results with closely spaced stirrups. CSA S6:25 predicted bond-strength values that were close to the experimental results compared to CSA S6:19, and CSA S806:12.

O. Molodid, O. Kovalchuk, V. Skochko et al.

Inthe first 100 days of the full-scale armed aggression of Russia's armed forces against Ukraine, more than 1600 rocket strikes were carried out, not including other shelling.In this regard, numerous buildings and structures suffered various damages. Using the developed "Methodology of surveying and registration of its results", surveyors developed a procedure for surveying many buildings and structures in a short period. KNUCA (Kyiv National University of Construction and Architecture) specialists inspected multi-apartment, communal, and administrative buildings in the Borodiankavillageinthe Kyiv region.Based on the results of the surveys, damage to buildings was systematized depending on their causes, namely explosions, and their impact on structures – explosive shock wave, fire, and bullet or shrapnel damage. The direct damage caused by the explosive shock wave included: destruction, cracking, distortion, and declination from the axis of symmetry, damage to window glasses and frames, for brick structures: knocking out (individual bricks or sections of the wall), protrusion (indentation) and displacement of masonry elements, cracks in masonry and spilling of seams between building elements.The direct damage to structures from shrapnel and bullet injuries includes: through holes, splinters, damage to coatings and the roofing layer, jamming of structures, et cetera.The direct damage to structures caused by thermal effectsincludes fire damage, including irreversible thermal elongation of reinforcement and destruction of concrete; damage to the finishing layers; destruction of window and door frames and their filling; the collapse of the roof; destruction of wooden walls and ceilings. KNUCA specialists established that buildings suffer significant damage and destruction when an aerial bomb hits. The most destructive effect is the damage caused by multiple launch rocket systems (MLRS), artillery weapons, and tanks. However, buildings (building structures) suffer minor damage when hit by Armory Personnel Carriers (APVs) and small arms.

Deepak Prasad, Arunabh Pandey, Brind Kumar

Pedram Ghassemi, Vahab Toufigh

Yuyu Wang, Jiaxin Pan

N. Emami, J. Heinonen, B. Marteinsson et al.

Traditionally, the emissions embodied in construction materials have not been considered important; however, they are becoming crucial due to the short time-frame in which the emissions should be reduced. Moreover, evaluating the environmental burden of construction materials has proven problematic and the reliability of the reported impact estimates is questionable. More reliable information from the construction sector is thus urgently needed to back and guide decision-making. Currently, the building sector environmental impact assessments predominantly employ commercial software with environmental impact databases and report results without knowledge about the impact of the software/database choice on the results. In this study, estimates for the embodied environmental impacts of residential construction from the two most widely used life cycle assessment (LCA) database-software combinations, ecoinvent with SimaPro software and GaBi, are compared to recognize the uniformities and inconsistencies. The impacts caused by two residential buildings of different types, a concrete-element multi-story residential building and a detached wooden house, both located in Finland, were assessed, including all building systems with a high level of detail. Based on the ReCiPe Midpoint method, fifteen impact categories were estimated and compared. The results confirm that the tool choice significantly affects the outcome. For the whole building, the difference is significant, around 15%, even in the most widely assessed category of Climate Change, and yields results that lean in different directions for the two cases. In the others, the estimates are entirely different, 40% or more in the majority of the categories and up to several thousand percentages of difference. The main conclusion is that extensive work is still urgently needed to improve the reliability of LCA tools in the building sector in order to provide reliable and trustworthy information for policy-making.

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

The article discusses the possibility of using the rescue equipment from height for firefighters to provide anti-terrorist protection of objects. The main requirements for rescue equipment are indicated.

Gholam Reza Khayati, Zahra Rajabi, Maryam Ehteshamzadeh et al.

Abstract The use of reinforced concrete is common in marine structures. Failure of reinforcement due to corrosion has detrimental impacts on nearly all of these structures. Hence, proposing an accurate and reliable model was imperative. The goal of this paper is to develop a new hybrid model by combining Particle Swarm Optimization (PSO) with Dragonfly Algorithm (DA) for Adaptive Neuro-Fuzzy Inference System (ANFIS) to predict the corrosion current density (C 11) of marine reinforced concrete. The neuro-fuzzy-based methods have emerged as suitable techniques for encountering uncertainties associated with the corrosion phenomenon in marine structures. To the best of our knowledge, this is the first research that predicts the C 11 through a model integrating fuzzy learning, neural learning rules, and meta-heuristics. 2460 data are collected from 37 regions in Persian Gulf. The input parameters are age, concrete repairing history, height above the sea level, distance from sea, concrete compressive strength, rebar diameter, concrete cover depth, concrete electrical resistivity, chloride ion concentration and pH. The proposed rules for the estimation of C 11 based on collected dataset are assessed based on the several metrics such as R 2, efficiency, mean absolute percentage error (MAPE), and median of absolute error (MEDAE). According to the results, ANFIS-PSO–DA enables to predict C 11 by R 2 (0.92), MAPE (1.67), MEDAE (0.14), and EF (0.97). The results of sensitivity analysis revealed that concrete compressive strength and pH are the most effective parameters on the corrosion current density of reinforced concrete.

Elena N. Baranovskaya , Petr A. Leonchuk, Stanislav A. Zuev et al.

The application of the method of local variations for solving applied problems including fire protection problems may involve possible difficulties (both analytical nature and numerical implementation). The issue concerning optimal placement of emergency exits along one or both sides of a long corridor arises when designing central-corridor residential buildings. The article considers the uniform distribution of outputs for both wide and narrow corridors and also presents the corresponding criterion. Calculations are given for a one-dimensional mathematical problem when emergency exits are placed only on the one side of the corridor, and for a two-dimensional one when emergency exits are placed on both sides and the influence of opposing emergency exits is taken into account. The non classical max (min) problem is formulated for calculations., The numerical version of its solution was proposed using the method of local variations since there were not found an algorithms for its solution in the literature. The paper considers the optimal arrangement of emergency exits on the longitudinal sides of the corridor with given length and width. Test variants for a small number of emergency exits (with a known solution) confirmed the correctness of the chosen algorithm as well as calculation using the created program on the TurboPascal-7 language. For the subsequent use of this method it is necessary to further test it for corridors of various configurations and a larger number of evacuation exits that exit into the specified corridor. The results of preliminary testing generally showed the possibility of applying the chosen approach to solving specific applied tasks.

Valeriy G. Shamonin, Stanislav A. Zuev, Petr A. Leonchuk et al.

When designing corridor-type buildings there is a question about the optimal placement of evacuation exits along one or both sides of a long corridor. The previous paper [1] considered the issue of uniform distribution of exits for both wide and narrow corridors, and there was presented the corresponding criterion. The present paper is a continuation of the work [1]. It considers the optimal arrangement of EEs on both sides of a piecewise rectangular corridor in residential and office buildings (letters P) if such device is not provided in the project. In this case, the requirement of maximum distance of EEs from each other minimizes the mixing of human flows during a fire. The nonclassical Maximin problem (maxmin) is formulated, for the solution of which there is proposed a numerical method of direct search – MLV. Calculations were carried out according to the developed program in the TurboPascal-7 language.