Abstract This study explores the structural behavior of axially loaded reinforced concrete (RC) walls with openings strengthened using glass fiber (GF) or welded wire mesh (WWM) reinforced engineered cementitious composites (ECC). Eleven instrumented specimens were constructed, prepared, and tested up to collapse. The primary factors investigated included opening size and shape, wall slenderness ratio, and the type of reinforcement employed for strengthening. Both square and circular openings were introduced, while the sizes were 0.25 and 0.20 of the wall’s width. Two wall heights were designed leading to slenderness ratios of 7.5 and 9.4. Both GF and WWM were employed to reinforce the ECC layer for strengthening the walls around the openings. Finite-element modeling (FEM) was conducted using Abaqus to simulate the load–displacement response, employing validated material models for concrete, reinforcements, and ECC layers. Experimental and numerical results confirmed that walls with ECC strengthening demonstrated significant enhancements in ultimate load capacity and stiffness compared to unstrengthened samples. Among the strengthening techniques, WWM embedded in the ECC layer yielded the highest ultimate load and energy absorption. A parametric study was performed to assess the influence of ECC layer thickness, indicating that increased thickness improved load capacity, with diminishing returns observed beyond 25 mm. The relationship between ECC thickness and ultimate load was represented by a third-degree polynomial equation with high accuracy. This study features the potential of ECC with embedded WWM as an efficient strengthening solution for reinforced concrete walls with openings.
Systems of building construction. Including fireproof construction, concrete construction
Vitaly I. Sibirko, Valentina S. Goncharenko, Tatyana A. Chechetina
et al.
There are represented the data on all fires in which member of volunteer fire service participated, as well as on fires where volunteer fire service members were the only participants from among fire service brigades either in cities and urban-type settlements or in rural areas. There are considered the dynamics as well as the total number of fires for 2014-2021, including distribution by fire objects, data on the use of fire-fighting equipment and nozzles at fires by the members of volunteer fire service and other kinds of fire services in 2021. The data of the number of people rescued per 100 fires are represented. Conclusions are drawn on the need to increase the resource availability and training level of volunteer firefighters.
Systems of building construction. Including fireproof construction, concrete construction
Shiva Safari Taleghani, Amir Masoud Salehi, Mojtaba Mehraein
et al.
Abstract In this study, the workability and mechanical characteristics of concrete containing different types of fibers and cement substitutes of concrete under standard, thermal, and sulfate environment curing conditions were compared. Normal concrete was made with a water-to-cement ratio of 0.43, and high-performance concrete was produced with smaller water-to-cement ratios (0.38, 0.33, and 0.28). Macro steel fibers in three different amounts and with two length sizes (60 mm and 30 mm), including polypropylene fibers (PP), and high-performance polypropylene fibers (HPP) in combination with steel fibers, blast furnace slag, and silica fume were used as cement substitutes. The tests performed include slump tests, compressive, flexural strength, and Brazilian tensile and microstructure images. Results showed that thermal curing (without moisture) reduces compressive, tensile, and flexural strength compared to standard curing conditions, and using the steel fibers this weakness was not reduced. In standard curing, by adding steel fibers, the mechanical properties increase significantly, and by increasing the percentage of steel fibers, the mechanical properties also improve. Concretes with a combination of different types of fibers did not favorably affect the mechanical properties of concrete compared to steel fiber concretes.
Systems of building construction. Including fireproof construction, concrete construction
Abstract Ceramsite aerated concrete blocks (CACB) are widely used in reinforced concrete frame infill walls due to their green, energy-saving, waste utilization, and thermal insulation characteristics. Investigations into building projects in areas with low seismic intensity and frequent typhoons have found that the cracking of CACB infill walls is severe, which hinders the use of this material. This article was dedicated to studying the reasons and development process of cracks in CACB infill walls, and proposing solutions. First, a 13 story framework building was analyzed using PKPM software to study the inter-story drift ratio under local reference wind pressure and gust wind pressure. Then, three full-scale models were made for quasi-static tests under horizontal loads to study the correlation between inter-story drift ratio and infill wall cracking. Experimental studies have shown that the inter-story drift ratio was 1/2149 and 1/2347 for infill wall frames with and without windows, respectively, when CACB infill walls cracked. Comparing PKPM analysis and experimental results, it could be seen that when the building was subjected to local reference wind pressure, the inter-story drift ratio was 1/2433, which was smaller than the cracking inter-story drift ratio. When subjected to the wind pressure corresponding to the gust wind, the structural deformation was much greater than the cracking inter-story drift ratio. Therefore, it could be concluded that the main reason for diagonal cracks in CACB infill walls was the unreasonable use of reference wind pressure in current design. To avoid the diagonal cracks, gust wind pressure should be used as the horizontal load instead of reference wind pressure in design. Simultaneously to improve both structural construction measures and material crack resistance to avoid cracking of CACB infill walls.
Systems of building construction. Including fireproof construction, concrete construction
Abstract To investigate the effect of preload on jacketed members, a method has been proposed to evaluate the strength of these members by considering the preload. The strain distribution resulting from the preloading was determined using the root-finding technique. This distribution was then applied to the core section, and an optimization technique was employed to derive the interaction diagram of the jacketed section. The proposed method is validated through experiments on columns and beams subjected to preloading and jacketing. A parametric study examined the effects of various preload levels as well as the geometry and characteristics of the jacketed section. The analysis results indicated that the effect of the preload resulted in a variation of 86–106% of the original strength in a typical square jacket cross-section. Notably, there was no significant difference in the effect of the preload across various other jacket cross-sections.
Systems of building construction. Including fireproof construction, concrete construction
Anatoly N. Garashchenko, Sergey P. Antonov, Aleksandr V. Vinogradov
et al.
The results of tests on the radiant heating stand for structural fire protection samples made of gypsum boards «GIPROK-IGNIS» are presented when reproducing standard and hydrocarbon exposure modes. The possibility of obtaining additional data on the effectiveness of gypsum boards, as well as on the effect of moisture contained in them on the properties and features of fire protection heating, is demonstrated. The results of thermocouple measurements have been obtained, which can be used to clarify the effective thermophysical characteristics necessary for thermal engineering calculations of structures with fire protection plates «GIPROK-IGNIS».
Systems of building construction. Including fireproof construction, concrete construction
Abstract Concrete pouring in winter is critical to both concrete manufacturers and end users owing to the possibility of concrete damage due to cold weather. In this context, various methods have been used to prevent frost damage to concrete in winter, including adjusting the concrete mix using a chemical admixture and heat-curing with tents. Of these methods, the insulated-gang-form approach does not require concrete-mix adjustment via a chemical-admixture addition. Furthermore, its positive effect on the initial quality of concrete during concrete construction in winter has previously been confirmed. In this study, the power consumption of the conventional gang form was compared with that of the insulated gang form to evaluate the efficiency of the two protection methods. A thermal vision camera was used to examine the surface heat loss of the gang forms after concrete pouring. The insulated gang form significantly outperformed the conventional one through its significantly reduced power consumption and reduced surface heat loss. These findings can contribute to the standardization of insulated gang form application to concrete protection in cold-weather conditions.
Systems of building construction. Including fireproof construction, concrete construction
Mei-Ling Zhuang, Jinsheng Cheng, Dongsong Fei
et al.
Abstract Based on the available experimental data, fiber models for four prefabricated fiber-reinforced concrete beam–column joint specimens with grouted sleeve connections are first developed in OpenSees software. Then, the simulated seismic performance of the specimens is compared with the experimental results. Finally, the effects of axial load ratio and shear-to-span ratio on the seismic performance of the specimens are further investigated numerically. The results indicate that Concrete02 material model and Reinforcing Steel material model can accurately simulate the constitutive relationship of concrete and reinforcing steel, respectively; the beam–column joint elements can accurately simulate different damage behaviors of the joint zone. Fiber-reinforced concrete can significantly improve the seismic performance of the specimens. The relative errors of the simulated seismic performance indexes are about 15%. It is recommended that the optimum value of shear-to-span ratio for prefabricated FRC BCJs is 2.0–2.5. The effect of axial load ratio on the seismic behavior of PBCJs-CM is very small, and can be negligible in the case that the prefabricated FRC BCJs has a moderate value of shear-to-span ratio. The fiber model developed in this article can provide a numerical simulation basis for subsequent studies of prefabricated fiber-reinforced concrete beam–column joint specimens with grouted sleeve connections.
Systems of building construction. Including fireproof construction, concrete construction
Abstract The temperature stress in mass concrete structure is relatively high during construction, which usually leads to temperature cracks. To solve this problem, concrete blocks are usually placed by setting wide slots. Connecting the truncated steel bars at the position of the wide slots by welding or extruding sleeves has many disadvantages. To solve the problem of temperature-induced stress loss, a new type of slightly curved arc HRB400 (SCAHRB400) steel bars was proposed without cutting off the steel bars in this article. Tensile tests and numerical simulations were performed for five types of SCAHRB400 steel bars considering geometric and material nonlinearity. Based on the test results and numerical simulation results, the equivalent stress–strain relationships of SCAHRB400 steel bars were established, and the emergence of the plastic zone of SCAHRB400 steel bars in the tensile process were observed, the tensile properties of SCAHRB400 steel bars were analyzed and discussed. The test results indicate that SCAHRB400 steel bars are prone to local yielding near the crown of large arches and at the connection of horizontal and arc sections. The numerical simulation equivalent stress–strain curves have good regularity. The equivalent stress–strain curves of slightly curved arc HRB400 and HRB335 steel bars have the similar changing law. When the stress is small, the tensile stiffness and compressive axial stiffness of slightly curved arc HRB400 and HRB335 steel bars are similar; when the stress is large, the axial stiffness of SCAHRB400 steel bars is greater than that of slight curved arc HRB335 steel bars. Through test and numerical simulation studies, the theoretical basis can be established for the engineering application of new slightly curved arc steel bars in mass concrete.
Systems of building construction. Including fireproof construction, concrete construction
Abstract This study is a part of the study to simplify the reinforcing details of reinforced concrete (RC) structural members by substituting the conventional reinforcement with hooked-end steel fibers (SFs). This paper investigates the effects of SF strength, dosage and aspect (l/d) ratio on the compressive and flexural behaviors of normal strength concrete with specified compressive strength of 30 MPa. In this study, hooked-end SFs of high strength (2000–2400 MPa) and normal strength (1100–1200 MPa) were used with three l/d ratios of 64, 67 and 80. Hooked-end SFs were incorporated with three dosages of 20 kg/m3 (0.25 vol.%), 40 kg/m3 (0.50 vol.%) and 60 kg/m3 (0.75 vol.%). Eighteen steel fiber reinforced concrete (SFRC) mixes were mixed. To evaluate the compressive and flexural performance of each SFRC mixture, three SFRC cylindrical and prismatic specimens for each mixture were manufactured and tested, respectively. The test results that the inclusion of hooked-end SFs had little effect on the compressive strength, while it improved the toughness of concrete. Hooked-end SFs were also found to be effective in enhancing the flexural performance of concrete. The dosage and properties (strength and l/d ratio) of SFs significantly affect the residual flexural tensile strength (f R1 and f R3) at serviceability (SLS) and ultimate limit state (ULS) defined in fib Model Code 2010 (MC2010).
Systems of building construction. Including fireproof construction, concrete construction
Vladimir A. Sorokin, Irina F. Zenkova, Oleg I. Fedulkin
The article considers the license requirement fulfillment which provides that a license applicant or license holder has a minimum list of equipment, in conditions of changes in the list of works and services included in the activities of installation, maintenance and repair of fire safety equipment of buildings and structures. The issue concerning alteration to the register of licenses under these conditions is examined. The peculiarities of implementation of licensing control are briefly considered.
Systems of building construction. Including fireproof construction, concrete construction
Abstract The main objective of this study is to investigate the structural performance of reinforced concrete (RC) beam specimens strengthened with 3D-fiberglass as compared with fiber-reinforced polymers (FRP) sheets. For this purpose, six RC beams were fabricated, strengthened, and tested under a four-point bending machine. One of the beams served as the control beam (REF), while the others were strengthened with carbon FRP (RCFRP), glass FRP (RGFRP), 3D-fiberglass and epoxy resin (R3DTR), 3D-fiberglass and epoxy resin extended to the sides (R3DTRB), and 3D-fiberglass and concrete repair (R3DTG). Failure mode, crack development, flexural capacity, ductility, the effectiveness of wrapping configurations, and the performance of epoxy resin in comparison with concrete repairer were studied between various beams. The results attest to the better performance and effectiveness of 3D-fiberglass over FRP in terms of flexural capacity, crack pattern, and ductility. The R3DTR and RGFRP specimens, compared to the control specimen, had the highest and lowest flexural capacity growth, with 19% and 8.4%, respectively. In addition, the failure modes observed in this study were in good agreement with the failure modes present in ACI.440.2R-17. Moreover, finite element (FE) models were proposed to predict the residual capacity of the specimens strengthened with FRP, using Abaqus software.
Systems of building construction. Including fireproof construction, concrete construction