Journal of building engineering最新文献

The use of prefabricated mass concrete blocks have gained increasing attention in construction industry. However, excessive temperature due to hydration can easily cause cracks, and the development of strength influences the lift and transportation time, thus affecting the efficiency of the precast yard. In this paper, the temperature field of three-graded mass concrete was simulated using Midas Civil, and compared to the measured results. In addition, the strength of concrete at different ages and locations was tested with different methods, and the influence of temperature inside the mass concrete on strength was explored. The results show that the finite element simulation basically agrees with the experimental temperature and can provide scientific guidance for the construction of three-graded mass concrete. The compressive strength of the specimens under the same conditions is consistent with that of the surface core samples of solid concrete blocks, and the rebound strength at different ages is lower than the compressive strength of the surface core samples. The temperature inside mass concrete has both positive and negative effects on the formation of concrete microstructure, high temperature can promote cement hydration and pozzolanic effect of fly ash to form more compact C-S-H gel. But under prolonged high temperature conditions, it can also cause morphology of CH to be coarse and loose, forming scattered needle shaped AFt. At different ages, the compressive strength of the core samples inside the concrete block is greater than that of the surface core samples. As the age increases, the concrete strength at the core location with the highest temperature may not necessarily be the highest. As the age increases, for example, at 7 days, the concrete strength at the core location with the highest temperature is 6.46 % higher than that at the surface, while the concrete strength is 15.6 % lower than that at locations with relatively lower temperatures.

Good bonding properties in the interfacial transition zone (ITZ) between the substrate and the repair material are critical to the success of the repair, and a good repair material can act as a protective layer to reduce the impact of fire on the structure. In this paper, Ordinary concrete (OP), geopolymer mortar (GP), and basalt fiber reinforced geopolymer mortar (GPb) were poured as the three repair materials on the roughened surface of the old substrate. The bonded specimens were exposed to temperatures of 23 °C, 200 °C, 400 °C, 600 °C and 800 °C for 1 h. The interfacial bond strength of the bonded specimens was tested by slant shear test, and the physical phase change of the repair material and the microstructure of the ITZ were analyzed by microscopic test. The results showed that the mechanical properties and high temperature resistance of ITZ were best when the old substrate interfaces were grinded and grooved and GPb was used as the repair material. Compared with S-OP, the bond strength of S-GPb was 26.92 %, 27.43 %, 46.50 %, 44.26 %, and 97.02 % higher at different temperatures. The increase in interfacial bond strength can be attributed to three mechanisms: (1) Mechanical interlocking with the old substrate with a rough surface. (2) The increase in temperature accelerates the volcanic ash reaction, and the formation of hydration products further fills the voids at the ITZ, maintaining the strength and compactness of the ITZ. (3) The addition of basalt fibers can form an anchoring effect at the interface, reducing the risk of interfacial spalling and cracking caused by material shrinkage in the ITZ.

Self-compacting concrete (SCC) is currently gaining traction as a replacement to conventional vibrated concrete. Its distinct microstructure leads to varied mechanical behaviour under different curing temperatures. In the past various supplementary cementitious materials (SCMs) were used in SCC to investigate their respective effects on the performance. However, there has been no systematic studies conducted to determine the effect of different curing temperature on the sensitivity reaction of rice husk ash (RHA) in SCC. This research focuses on high-strength SCC with SCMs such as RHA, silica fume (SF), fly ash (FA), and ground granulated blast-furnace slag (GGBS), exploring their applicability for concrete structures under varying curing temperatures. Heat of hydration, compressive strength and open porosity of SCC specimens were assessed at various temperature. Results indicate high curing temperatures expedite the hydration and pozzolanic reaction, refining the microstructure and increasing the early-age concrete strength, but compromising the long-term performance, potentially mitigated by the use of SCMs. Conversely, lower curing temperature, impedes hydration leading to gradual strength gain, particularly with SCMs, yet yielding significant strength increases at later concrete age. SCMs presence and curing temperature significantly influence maturity function-based strength predictions, impacting strength trends in the samples studied.

Cost-efficient measurement of room-level heat output from hydronic radiators is a major barrier to large-scale implementation of Economic Model Predictive Control (EMPC) in residential space heating for demand-side management. This paper therefore presents a novel EMPC strategy for hydronic radiators that relies on measurements of radiator pipe temperatures as a proxy for the radiator heat output, thus eliminating the need for costly flow-based meters at each radiator in a building. Simulation-based experiments indicate that the proposed proxy-based EMPC matches the performance of its heat-based counterpart. The proxy-based EMPC achieved a 16.6 % cost reduction compared to the heat-based EMPC's 16.8 %, with no comfort violations in both cases. Furthermore, the strategy shows resilience towards uncertainties in the user-estimated radiator exponent and maximum heating capacity. The proposed EMPC scheme also allows system operators to fine-tune the balance between cost savings and return temperatures using the proxy's upper limit. The findings presented in this paper suggest that the proposed proxy-based EMPC scheme provides a practical pathway for broader applications of EMPC in hydronic-based space heating with the prospect of unlocking significant load shifting potential, cost savings for end-users, and enhanced efficiency in individual and collective energy systems.

Fire alarm systems in metro stations play an important role in safeguarding lives and properties. The design process for these systems is complex and time-consuming due to the diversity of device types, wide distribution of device locations, and numerous compulsory design codes. This paper proposes an automatic design framework for fire alarm systems aimed at enhancing design efficiency. The framework includes five automated processes: information preprocessing, device arrangement, system loop generation, device wiring, and result generation. By converting the computer-aided design (CAD) results into building information models (BIM), building information and related professional device information are obtained, addressing the need for fire alarm system (FAS) design to integrate with multiple disciplines. The process can also automatically arrange FAS devices according to design specifications. Optimization algorithms, such as Ant Colony Algorithm and Prim Algorithm, are used to determine the device connection order and solve the problems of obstacle avoidance and orthogonal connections between two points. Compared to traditional design methods, the proposed automatic design framework for fire alarm systems in metro stations can not only satisfy the mandatory design requirements but also avoid the cumbersome and repetitive design process, providing new solutions for designers. Additionally, it can reduce wire length and save on construction costs. Using a real metro station as a case study, it is calculated that the automatic design can save between 8 % and 48 % of the wire length.

Recent advanced architectural algorithms, such as real-time optimization control and fault diagnostics, have garnered significant interest for their ability to reduce building energy consumption and improve equipment maintenance efficiency. However, deploying these algorithms in actual buildings often involves significant manual effort and time to align building data points with algorithmic requirements. In response, standardized ontologies like the Brick Schema have been introduced. This ontology streamlines the representation of building topology, equipment, and data points, as well as algorithm inputs, enabling quicker algorithm integration and deployment. Despite these advancements, manually constructing Brick models from scratch remains time-consuming, laborious, and prone to errors, presenting a new challenge in rapid model development. To overcome these issues, some researchers have turned to universal BIM formats, such as IFC/Revit, for accelerated Brick modeling. Nevertheless, the prevalence of errors in human-generated BIM models often impedes effective conversion. To efficiently convert imperfect IFC models into Brick models, this paper presents a novel BIM to Brick methodology comprising three key steps: IFC inspection and repair, IFC to Brick semantic modeling, and dataset mapping. This method ensures high-quality reuse of even imperfect IFC models. Our case study demonstrates that this method can produce an ideal Brick model from a flawed BIM model, meeting the semantic metadata requirements specified by the BuildingMOTIF tool. This innovative approach substantially reduces the effort required to generate Brick models, effectively handling the inaccuracies and noise inherent in real-world BIM.

Conventional eccentrically braced frames (EBFs) exhibit significant residual deformations following major earthquakes, necessitating costly repairs for the damaged structures. This study proposed a novel self-centering Y-eccentrically braced frames (SC-YEBFs) system to enhance the seismic resilience. A theoretical mechanical model which takes into account its components is formulated to predict the lateral load behavior of SC-YEBFs. The pseudo-static experiments were conducted on four specimens, and the resulting observations and analyses demonstrate that the shear links effectively function as ductile fuses, dissipating a significant portion of the input energy to safeguard the main frame from damage. Furthermore, the self-centering joint exhibits a hinge-like behavior with remarkable self-centering characteristics. The structural reparability of all specimens was found to be exceptional during major seismic events. By increasing the initial prestress and sectional area of steel strands, the self-centering performance can be further enhanced. The damaged shear links could be easily detached by loosening bolts, and the consideration of prestress loss is nonnegligible to ensure an exceptional self-centering performance. The proposed theoretical model predicted the mechanical properties of SC-YEBFs, including lateral stiffness, energy dissipation, and self-centering mechanism, through a comparison with experimental results. Moreover, the theoretical model was utilized to propose an equivalent simulation method for simulating self-centering joint and shear link using Connector function in ABAQUS software, while establishing a simplified frame finite element model for further analysis.

Perforated solar screens are extensively utilized as a shading solution for fully glazed buildings and transparent envelope systems. While uniform perforated solar screens have been traditionally employed, the growing trend towards non-uniform screens highlights their potential to enhance architectural aesthetics through varied perforation patterns on building facades. However, the effects of non-uniform screens in daylighting performance have been rarely investigated. This study aims to assess the effects of non-uniform perforated solar screens on daylighting performance, encompassing daylight availability, uniformity, and annual glare probabilities. A comparative analysis was conducted using simulation studies for eight distinct non-uniform perforation patterns against a uniform perforation scenario. Orthogonal experiment and data envelopment analysis were employed to identify the influential factors and evaluate the overall performance. The results suggest that non-uniform perforated solar screens with specific perforation patterns significantly outperform uniform screens in terms of daylighting performance, at equal perforation ratios. Specifically, two non-uniform prototypes, namely (h) periphery-center and (f) bottom-top, demonstrated exceptional performance. Furthermore, the perforation pattern was identified as the most significant geometrical factor affecting the overall performance of daylighting and glare discomfort. The results of this study may inform the design of perforation patterns to enhance daylighting performance in non-uniformly perforated solar screens. The novelty of this research lies in establishing a framework for evaluating the influence of non-uniform perforation patterns on indoor daylighting and visual comfort.

In contrast to the beam-column joints found in traditional assembled steel structures, modular steel structures feature inter-module and intra-module connections within their joints. While existing research has largely focused on the mechanical properties of inter-module connections, the impact of intra-module connection stiffness on the performance of modular steel joints remains unclear. This study introduces a novel corner-fitting-reinforced fully bolted joint specifically designed for modular steel structures. A series of experiments were conducted, including a flexural test on bolted intra-module connection to determine its initial rotational stiffness, and four groups of lateral static tests on full-scale modular steel joints with varying intra-module connection stiffnesses. These tests aimed to characterize mechanical properties such as load-carrying capacity, lateral stiffness, strain development, and ductility. The study elucidates the influence of intra-module connection stiffness on the lateral stiffness of modular steel joints. Furthermore, a refined finite-element (FE) model of the corner-fitting-reinforced fully bolted joint was developed. Simulation results showed good agreement with experimental findings., with an average error of less than 10 % for ultimate load-carrying capacity prediction. The FE model also, analyzed the stress-strain development of the corner fitting throughout the process. The study establishes a theoretical analysis model for the corner-fitting-reinforced fully bolted joint and derives a theoretical formula for the initial lateral stiffness of the modular steel joint, considering semi-rigid intra-module connections. This formula aligns well with both experimental and FE results, with a maximum error of 15 %. Finally, the study delves into the force-transfer mechanism of the corner-fitting-reinforced fully bolted joint, providing valuable insights for its design.

As a fast-growing grass, bamboo has received a great deal of attention due to the excellent mechanical performance. The unique properties of bamboo come from its natural composite structure - a kind of natural fiber reinforced composites, which is composed of bamboo fibers (reinforcement) and parenchyma tissue (matrix). Based on raw bamboo, man-made bamboo fibrous composites such as engineered bamboo and bamboo fiber reinforced polymeric composites have emerged. These materials eliminate some inherent shortcomings of bamboo, which can provide more stable material performance and achieve dimension alteration according to requirements. All of these bamboo fibrous composites have orthotropic structure, the mechanical properties of which in the longitudinal direction far exceed that in the transverse direction, and the tensile strength and compressive strength can reach 111–114.8 and 104.7–115.7 MPa respectively. Besides, the interfacial zone between fiber and matrix is weak, in which some defects are usually existed, such as micro-cracks and adhesive voids. As a result, cracks in the composites are inevitable, which are easy to extend in the longitudinal direction and result to fracture failure. Consequently, fracture studies become necessary for evaluating the crack-resistance ability of bamboo fibrous composites. This paper systematically introduces the previous research works on the fracture properties of bamboo fibrous composites. Firstly, this paper summarized the test methods for different fracture modes including Double cantilever beam (DCB), Single-edged notched beam (SENB), Compact tension (CT), etc., meanwhile the corresponding calculation theories such as Compliance calibration (CC), Modifed compliance calibration (MCC) and Modified beam theory (MBT) are also elucidated. Subsequently, the fracture behaviors and mechanisms of various bamboo fibrous composites are analyzed, in which the fracture parameters and crack-resistance capabilities are compared. In addition, considering the limitations of current research, the future research in need on the fracture properties of bamboo fibrous composites are discussed, the conclusion can be used in providing important reference for the safety evaluation of bamboo fibrous composites.