Journal of building engineering最新文献

Although the application of ultra-high performance seawater sea-sand concrete with limestone calcined clay cement (UHPSSC-LC³) provides a promising solution for sustainable marine structures, research on the mechanical properties of UHPSSC-LC³ is quite limited, and no research has been conducted on its chloride resistance performance. In this study, the effect of four curing regimes (i.e. standard curing, 20 °C seawater curing, 40 °C fresh water curing, and 80 °C fresh water curing) on the compressive and flexural strength of UHPSSC-LC³ is experimentally investigated. Rapid chloride migration test and chloride titration test are conducted to determine the chloride diffusion and distribution of UHPSSC-LC³, considering the effects of curing conditions and calcined clay (CC) dosage. In addition, XRD analysis is performed to show the differences in the composition of UHPC, UHPSSC, and UHPSSC-LC³. The obtained results demonstrate that UHPSSC-LC³ attains higher mechanical strength than UHPC and UHPSSC under various curing conditions. The incorporation of LC³ makes the free chloride concentration of UHPSSC-LC³ close to that of UHPC, especially when the heated water curing is applied. The free chloride concentrations of UHPSSC- LC³ cured with 40 °C and 80 °C water are only 10.1 % and 2.9 % higher, respectively, than that of UHPC cured under standard condition. Besides, UHPSSC-LC³ achieves the lowest chloride ion diffusion rate, which is 40.4 % lower than that of UHPSSC, due to the denser matrix resulting from the carboaluminate products and the pozzolanic effects of the calcined clay. Furthermore, the application of heated water curing regimes is recommended for UHPSSC-LC³ when the early strength and chloride resistance are the main concerns.

Reducing the radon emission rate on the surface of self-compacting concrete prepared from industrial solid waste is crucial to lowering the risk of human lung cancer. This study prepared four types of self-compacting concrete with a composite cementitious system of silica fume and molybdenum tailings. The effects of various curing temperatures (0 °C, 20 °C, 40 °C, and 60 °C) and amounts of molybdenum tailings substitution on the pore structure, microstructure, compressive strength, and radon emission characteristics of self-compacting concrete were studied. Additionally, using Low-Field Nuclear Magnetic Resonance (LF-NMR), a segmented fractal analysis of the pore structure of self-compacting concrete within various pore size ranges was carried out. The findings suggest that raising the curing temperature and using a suitable quantity of molybdenum tailings enhance self-compacting concrete's compressive strength and the microstructure's density, while decreasing the porosity and radon emission rate. The variation in the micro-pore structure resulting from the aggregation of C-S-H gels strongly correlates with the radon emission rate. This association is evident through decreased porosity and increased fractal dimensions D₁ and D₂. This results in a denser microstructure of self-compacting concrete, weakening the connectivity of microcracks and pore throats, thereby reducing the transport pathways for free radon and lowering the radon emission rate.

The interface between new and old concrete plays a significant role in reinforced concrete engineering due to its size effect and weak strength. To investigate the size effect of tensile strength in new-to-old concrete, splitting tensile tests and computed tomography (CT) scans on composite specimens were conducted. Specimen size, interface roughness, volume fraction of polyvinyl alcohol fiber and adhesive were considered. The tensile bonding strength initially increases and then decreases with interface roughness and fiber content, while size effect on the strength shows a downward trend before rising. The adhesive notably enhances the tensile bonding strength and weakens its size effect. The interface roughness, polyvinyl alcohol fibers and interface agents influence the size effect by modifying the bonding area, specimen uniformity, and characteristic structure of the interface region. At an interface roughness of 5.5 mm and a polyvinyl alcohol fiber content of 0.5 %, the maximum strength was achieved and the maximum attenuation of size effect occurred. The size effect laws of tensile bonding performance were presented based on the Weibull statistical theory, Bažant energy theory and Carpinteri multi-fractal theory. The experimental values exhibit good consistency with the predictions from the size effect models.

The significant negative impact of embedding nano-ZnO in cementitious materials on setting-time and compressive-strength limited its application despite its remarkable self-cleaning properties. Therefore, this study presents a proposal to employ nano-ZnAl₂O₄-spinel instead of nano-ZnO in an attempt to eliminate such defects while maintaining self-cleaning behaviour. Seven mixes were prepared: alkali-activated slag (AAS, control, 0 wt%nano-particles), while other specimens were modified with 0.25, 0.5 and 1 wt% nano-ZnO or nano-ZnAl₂O₄-spinel. The results proved the efficacy of nano-ZnAl₂O₄-spinel in shortening setting-time and improving the compressive-strength at early/later ages compared to nano-ZnO. The AAS-modified with 0.5 wt%nano-ZnAl₂O₄-spinel (optimum dose) have an acceptable setting-time (within standard limit) and the highest compressive-strength in between AAS (control) and other modified with nano-ZnO. The XRD showed that forming Zn(OH)₂ (isolated-barrier) and zinc-alumino-silicate-hydrate is the reason behind the retardation effect and inadequate compressive strength of AAS-modified with nano-ZnO. The TGA/DTG and SEM clarified that the filling/nucleation-site/reactivity effects (high surface-area) of nano-ZnAl₂O₄-spinel cause generating a massive amount from various strength-giving-phases that form compact structures. Regarding the antimicrobial activity, the specimens containing nano-ZnAl₂O₄-spinel have a superior bacterial resistivity similar to others containing nano-ZnO. Finally, it is concluded that nano-ZnAl₂O₄-spinel is preferred to nano-ZnO in developing self-cleaning binding materials with acceptable fresh/hardened properties.

The load resistance of masonry infilled panels in upgrading the steel frame to mitigate progressive collapse was quantified experimentally and analytically in the current study. Four 1/2-scale steel subframes were tested, including two bare subframes without infilled panels for reference and two infilled subframes to assess the effects of infilled panels. Two types of connection were investigated in current study: welded connection and top and seat angle connection. The test result showed that infilled panels provided a greater improvement in initial stiffness and peak load of the steel subframe with top and seat angle connections compared to the infilled steel subframe with welded connections. On the premise that the connections retained their integrity, the strut mechanism of infilled panels could change from a diagonal strut mechanism forming in the whole panel to an off-diagonal strut mechanism formed in the remaining intact corner region with increasing vertical deflection. A novel equivalent multi-strut modelling method was proposed for the prediction of the infilled panel behavior with an acceptable level of accuracy. This model incorporates the shifts in the position of plastic hinges, which were influenced by the specific types of connection and the load-resisting mechanisms of the infilled panel. The analysis result demonstrated that the model slightly overestimated the load resistance of infilled panels within the steel frame with simple connections and slightly underestimated the load resistance of infilled panels within steel frame with semi-rigid or rigid connections.

Accurately predicting players’ thermal comfort in large sports spaces for real-time window and HVAC operations presents significant challenges due to non-uniform thermal distributions. Standalone building energy simulation (BES) typically assumes the entire targeted space as a uniform thermal zone, which fails to capture these variances. Conversely, Computational Fluid Dynamics (CFD) simulation can predict indoor thermal environments with precision but often struggles with determining accurate boundary conditions. This study introduces a coupled BES and CFD simulation method tailored for real-time window and HVAC control in sports spaces. A case study was conducted in a prototypical national fitness hall to evaluate the effectiveness of the proposed method. The thermal comfort and cooling energy results from the co-simulation-based control were compared with those from standalone EnergyPlus simulation-based control and fixed-schedule window and HVAC operations, which served as baselines. The results indicate that the proposed method enhanced thermal comfort by 68.5 % compared to constantly-scheduled window operations and achieved daily energy savings of up to 43.5 % versus constantly-scheduled HVAC operations. Furthermore, significant discrepancies in Average Predicted Mean Vote ($\overline{PMV}$) or Average Adaptive Predicted Mean Vote ($\overline{aPMV}$) as well as daily cooling energy consumption between the BES-CFD co-simulation and standalone EnergyPlus simulation were identified, ranging from -0.53 to 1.83 for $\overline{PMV}$ ($\overline{aPMV}$) and -2444.6 to 1266.5 kWh for cooling energy. This study contributes novel methods for real-time window and HVAC control in sports buildings towards thermally comfortable and energy-efficient sports environments.

Accurate measurement of chloride ion diffusion coefficient, without external interference, is essential for obtaining data that closely reflects practical conditions. The diffusion constants of chloride ions within fly ash-based geopolymer concrete (FGPC) with a one-dimension immersion method employed to record the time taken for diffusion to occur over a specific distance were investigated in this work. The results showed a clear relationship between the diffusion constant and the strength of FGPC. Within the same strength of FGPC, the diffusion distance (thickness) is proportional to the square root of diffusion time. The minimum diffusion constant is approximately 8.90 × 10⁻¹¹ m²/s which is close to the result in an immersion test. The method employed in this study is demonstrated to be both feasible and applicable for assessing the diffusion constant of chloride ions in FGPC quickly. It promotes a rapid evaluation method to predict the diffusion process under practical conditions.

Climate change, driven by fossil fuel dependence, presents a significant challenge for the construction industry, particularly in energy-intensive regions like arid climates. This research investigates the potential of integrating machine learning and parametric optimization to enhance the energy efficiency of spatial structure domes in such environments. Focusing on a sports pavilion in Kerman, Iran, the study examines the crucial role of cladding systems in building energy performance. Employing a rigorous four-phase methodology, the research optimizes dome cladding materials for hot, dry climates using a dual objective function: energy cost and material cost. The process involves a comprehensive literature review, data-driven material selection, advanced energy simulations, and optimization analysis. Parametric modeling tools (Rhino, Grasshopper, Honeybee) facilitate the comparative analysis of various cladding systems. Multivariate Polynomial Regression (MPR) enables predictive modeling of energy consumption and material costs, streamlining the design process for architects. The optimized solution is a hybrid cladding model composed of 10 % polycarbonate and 90 % aluminum. Analysis reveals that the hybrid system offers superior energy optimization compared to pure aluminum (4.58 %) and polycarbonate (5.70 %). While polycarbonate has a lower initial material cost, the hybrid system achieves a balance between material expenditure and long-term energy efficiency. This highlights the importance of considering life-cycle costs when evaluating building envelope materials. This research advances a framework that leverages machine learning and parametric design for building envelope optimization. This framework empowers architects and engineers to create energy-efficient structures within arid environments, promoting a more sustainable built environment.

Recycling construction waste is a viable tactic for advancing environmentally friendly building methods. With regard to concrete applications, the purpose of this research is to determine whether it is feasible to use recycled fine concrete aggregates (RFA) in lieu of natural fine aggregates (NFA) and to lessen the environmental impact of natural resource depletion and landfill space. A sustainable steel fiber-reinforced concrete was created by replacing NFA with RFA at the replacement ratio of 0 %, 50 %, and 100 %. Steel fibers (SF) were also included to mixes at three different contents of 0, 25 and 50 kg/m³ in order to further improve the qualities of the concretes. Thus, the aim of this paper is to appraise how the addition of FRA affects the mechanical, freeze-thaw, fresh, and non-destructive qualities of concrete. Nine concrete mixtures were cast, and tests were made to evaluate the following properties: flowability, fresh concrete unit weight, tensile and compressive strengths, elastic modulus, surface hardness, crack mouth opening displacement (CMOD), freeze and thaw performance, sulfate resistance and abrasion. Moreover, microstructure properties of concrete were also analyzed. The outcomes revealed that the mechanical, flexural, and durability performances of the concrete mixtures were enhanced by substituting RFA for NFA. The mixture with 50%RFA and 50 kg/m³ SF gained maximum compressive strength of 44.82 MPa which was 20.7 % greater than the reference mixture (RFA0F0). The mixture containing 100 % RFA and 25 kg/m³ SF had the highest elastic modulus and showed an approximately 33 % augmentation in elastic modulus as per the reference mixture. The mixture with 100%RFA and 50 kg/m³ SF exhibited the largest tensile strength indicating 60 % tensile strength enhancement as per the reference mixture. Combined use of RFA and 50 kg/m³ SF in concrete mixtures had the best abrasion and freeze-thaw resistance. SF incorporated concrete mixtures with RFA exhibited worse sulfate resistance. This study contributed significantly to global resource efficiency and environmental preservation by shedding light on the sustainable use of RFA and SF in the making of concrete. The results made important contributions to global research and promote environmentally friendly building methods all throughout the world.

The development of resilient lateral load-resisting systems is essential for multi-story and high-rise timber buildings in earthquake-prone areas. In this paper, an attempt is made to integrate dual-tube self-centering buckling-restrained braces (DT-SCBRBs) to glulam frames, aiming to improve their structural resilience to earthquakes. To assess the seismic effectiveness of such a DT-SCBRB glulam frame, nonlinear time-history analyses (NLTHAs) were conducted on a series of prototype DT-SCBRB glulam frames with different building heights and design parameters of DT-SCBRBs. The seismic performance of these prototype structures was evaluated in terms of maximum inter-story drift ratios (MaxISDRs), residual inter-story drift ratios (ResISDRs), and inter-story drift uniformity. The results show that the frame with lower post-tensioning-to-yielding ratios of DT-SCBRBs tended to exhibit lower MaxISDRs but could sometimes lead to higher ResISDRs under major earthquakes. Low deformability of tendons could result in tendon fracture under major earthquakes. The ResISDRs of all the prototype frames were lower than 0.5 %, the drift limit for the “Repairable” performance level. Compared to minor and moderate earthquakes, the DT-SCBRB glulam frames deformed more uniformly during major earthquakes. Incremental dynamic analyses (IDAs) were also conducted on these prototype structures, developing a database to quantify performance levels of DT-SCBRB glulam frames. The MaxISDRs of 0.5 %, 0.7 %, and 2.6 % were recommended for immediate occupancy (IO), life safety (LS), and collapse prevention (CP) limit states of DT-SCBRB glulam frames.