Journal of building engineering最新文献

This study investigates the efficacy of saliency mapping algorithms in capturing the visual priorities of building inspectors for structural damage assessment. Our work established a ground truth dataset by implementing eye-tracking technology to capture the gaze patterns of building inspectors. Further, it enables a detailed evaluation of the saliency models’ ability to reflect experts' visual attention during inspection tasks. Our comparative analysis assesses the performance of three saliency models— EnDec, DeepGaze, and SALICON— against this ground truth data, using conventional saliency metrics such as Area under the Curve, Similarity, Normalized Scanpath Saliency, Correlation Coefficient, and Kullback-Leibler Divergence. Our findings reveal that while the SALICON model demonstrates a marginally better performance and highlights areas where these models fall short, particularly in accurately reflecting the critical visual properties of inspectors, this insight is crucial for advancing the field. By highlighting these limitations, we have drawn attention to the need for developing more specialized saliency models tailored to the unique demands of building inspection tasks. Thus, the study not only fulfills its objectives of comparative analysis but also contributes to the broader discourse on improving automated structural inspection systems. This study highlights the need to develop specialized computer vision models to address specific building inspection challenges. By identifying strengths and improvement areas, this research contributes valuable insights and highlights the potential and current limitations of applying computer vision techniques to real-world building inspection tasks.

Time-space-dependent stress and strain distribution within steel bar-mortar composites is key for shrinkage and cracking prediction of Reinforced-Concrete (RC) members. A novel system was designed to investigate the restraint of steel bars on the early-age shrinkage while digital image correlation was also employed to analyze spatial strain distribution. The measured restraint degree increases with the reinforcement ratio and maintains stable after about 36 h. Restraint effects is interfered by micro-cracks, because of which the calculated restraint degree matched the measured one better after being modified by a coefficient concerning reinforcement ratio. The overall restrained stress shows a three-stage process affected by the bonding evolution. The strain spatially undergoes a three-region distribution along the steel bar induced by the shear transfer and a two-region distribution on the cross-section aligning with the interface gradient. This study demonstrates a quantitative analysis on the steel bars restraint parameters and its evolution.

This paper discusses the flexural behavior of carbonated recycled aggregate concrete (RAC) beams through experimental data. We produced fifteen beams, each varying in recycled aggregate replacement ratios: 0 %, 30 %, 50 %, 70 %, and 100 %. Each replacement ratio included three beams, amounting to different levels of carbonation: non-carbonated, partially carbonated, and completely carbonated. Post accelerated carbonation processes; flexural testing was conducted. The findings reveal that beams incorporating varying amounts of recycled coarse aggregates (RCA) but maintaining identical carbonation levels exhibited a minor reduction in the cracking moment, with negligible variations in ultimate flexural strength and deflection. Moreover, beams sharing the same RCA replacement ratio demonstrated increased cracking moment, ultimate flexural strength, and stiffness with advancing carbonation levels, while deflection tended to decrease. Based on these findings, predictive models for cracking moment and ultimate flexural strength of carbonated RAC beams were developed. Comparisons between experimental outcomes and numerical simulations, particularly within the RAC50 group, indicated nearly identical results.

Two-dimensional particle morphology indices face challenges in accurately depicting the characteristics of three-dimensional (3D) manufactured sand (MS), which does not effectively guide the selection of MS for high-performance concrete (HPC). This study aimed to obtain a quantified comprehensive evaluation of actual MS particle groups with specific gradations by thoroughly analysing 3D geometric characteristics. Two representative MS samples were selected for exploration, and river sand (RS) was used as the control. A random selection of sand particles was screened on six sieve levels ranging from 0.15 mm to 4.75 mm. Using X-ray computed tomography and associated image processing technologies, 3D models of these particles were generated, and MATLAB was used to extract their 3D morphology information. Subsequently, the change rules and validity of current 3D particle morphology indicators were examined, focusing on shape, angularity, and texture. Moreover, a comprehensive morphology index, C_m, was proposed by considering the effects of gradation and particle shape classification. The results showed that shape indices more accurately reflected particle characteristics, notably, a higher proportion of spheroid particles, a lower aspect ratio, and greater sphericity correlated with improved particle shape; contrary to traditional beliefs, the angularity index suggested that greater roundness did not necessarily equate to more rounded particles owing to the influence of the proportion of spheroid and cubic particles; meanwhile, texture indices showed minimal difference in the mean values of the 3D fractal dimension for the three types of sand. The proposed index C_m effectively differentiated the particle morphology states of the three sands, with higher C_m values indicating superior particle morphology. The smaller the difference between the C_m values of MS and RS, the better substitute of MS for RS.

Solar photovoltaic thermal (PVT) collectors incorporating phase change material (PCM) as an active-passive cooling approach represent a promising solution for thermally managing PV panels. This needs to be experimentally evaluated in harsh outdoor conditions. Therefore, this study examined the electrical and thermal performance of solar PVT systems in comparison to a reference PV panel during six distinct summer days in Riyadh, Saudi Arabia. A thermal camera was utilized to precisely capture the difference in temperature variations between the two PV panels over the study periods and to examine different options for the PVT collector. On Day 3, near noon, the highest solar irradiance of 1019 W/m² led to the highest power of the PVT, with an increase of 5.75 % over the reference panel. The highest ambient temperature of 47.69 °C was recorded on Day 1 with 901.4 W/m² irradiance, providing 10.58 % electrical efficiency of the PVT, an increase of 5.9 %. On Day 6, the PVT module was equipped with eight rectangular metal conduits that were filled with PCM with a transition temperature range of 41–48 °C. This simple-to-implement design added additional passive cooling for the system through the exterior surface of the metal conduits, along with the PCM contribution. The PTV-PCM option led to the best performance, with an 8.05 % improvement in electrical power and efficiency over the reference PV and 71.16 % and 81.50 % thermal and combined PVT efficiencies, respectively. The importance of cooling the PV panel in such challenging circumstances was illustrated by the 2 %–3.24 % increase in electrical output for every 1 °C decrease in the temperature of the cells.

Traditional Tibetan architecture is an important part of the Chinese architecture. Many of the Tibetan structures are suffering from different types of damages after hundreds of years of service. The structural arrangement, types of damage and failure modes of these timber structures have been investigated on site. Tilting of structural members is found to be the most common type of damage. This paper studies the limiting inclination angle of a single-column supporting assembly of these structures before its collapse for proactive maintenance and restoration. A method to estimate the limiting tilt angle of the column is proposed based on the relationship between the lateral force, F, at the column head and the tilt angle, θ, of the column. Simplified analytical models of this column assembly in a traditional Tibetan timber building under in-plane and out-of-plane loadings respectively are proposed. The behavior of the constituting column foot joint, column-Queti joint and Queti-beam joint are analyzed in detail to obtain the global deformation and M-θ relationship of the column assembly under different loads. The F-θ relationship of the column assembly from the intact state to collapse is then obtained. A verified finite element model of the column assembly is adopted as reference to validate the performances of the proposed models throughout the loading process. Comparison of the F-θ curves obtained from the analytical models and the simulated results demonstrates the validity and accuracy of the proposed models. They may be adopted for a quick analysis of practical structures to estimate their limit states for health monitoring, maintenance and strengthening of structures.

Constrained by the inadequate percentage of ultraviolet in solar irradiation and the low transmittance of photocatalytic layer, the purification and thermal performance of photocatalytic-Trombe wall (PC-TW) need to be improved urgently. To address this, a novel passive method to regulate PC-TW performance using horizontal fins was proposed. Aiming at this innovation, by numerical method, a three dimensional model was constructed to investigate the impact of relative fins height h* and spacing s*, and the mechanism about how these parameters affect the performance was also discussed. The results indicate that: under natural ventilation strategy, compared with PC-TW without fins, the thermal efficiency η_th, purification efficiency η_HCHO and total efficiency η_total are improved to some extent and there exist optimal fins parameters. However, horizontal fins will instead lower the efficiencies when h* exceeds 0.4. Under forced ventilation strategy, the increase in h* contributes to all efficiencies, making η_HCHO increasing monotonically, while η_th and η_total present a parabolic trend. In addition, the increase in s* lowers the improved efficiencies but can still keep them in a high range. For different ventilation strategies, considering the performance and manufacturing cost, the suggested h* and s* are 0.2 and 2.5. h* and s* respectively regulate the performance by affecting the size and amount of vortex between adjacent fins, and h* has a greater impact on the performance than s*. This study not only paves a new approach for performance regulation of PC-TW, but also provides theoretical basis for structural design and operation of PC-TW with fins.

Increasing population density and urbanization have intensified the need for high-rise buildings in recent years. The seismic resistance of high-rise buildings should be carefully concerned in seismic regions, especially for super high-rise buildings which are most vulnerable to long-period earthquakes. This paper introduced the model design of a 499 m super high-rise mega frame-double core tube composite structure and presented the shaking table test results of the 1/50 scaled structural model. This super high-rise building possesses many conducive merits to resist seismic hazard, including steel reinforced concrete members, high-strength concrete and double core tube. In the test, there were three groups of long-period earthquakes and four incremental seismic intensity levels considered. The test phenomena indicated that the coupling beams of exterior tube were the first line of defense to resist seismic actions. The existence of inner tube improved the shear resistance of this building and there was no observed shear damage on the walls. Based on the instrumented data, the vibration characteristics, acceleration, displacement and strain responses of the structure were reported. The seismic performance of this super high-rise building meets the requirements of design specifications and its collapse resistance capacity is physically proved under severe earthquakes. However, the whiplash effect of acceleration is serious on the roof due to the reduction of mass and constraint for the mega column end. Furthermore, the inter-story drifts and strain responses of trusses in the top region are significantly larger. For the seismic measurement, great attentions should be paid to the exterior coupling beams and structural members in the top region of this super high-rise building. The presented work provides well experimental confirmation and reference for super high-rise buildings with mega frame-double core tube composite system.

The accumulation of carbide slag (CS), red mud (RM), and municipal solid waste incineration fly ash (MSWIFA) has led to significant environmental pollution issues, necessitating urgent resource utilization. Building upon the previously developed CS-MSWIFA synergistic activation RM-slag cementitious system, this study aims to further incorporate iron tailings sand and polypropylene fibers to prepare fiber-reinforced concrete. The systematic investigation focuses on the influence of cementitious material types, aggregate types, fiber shapes, lengths, and dosages on the impact resistance of concrete. Furthermore, an impact damage evolution equation and life prediction model were developed based on the two-parameter Weibull distribution. Results indicate that the type of cementitious material and aggregate has minimal influence on the impact resistance of concrete, while the addition of fibers significantly enhances its impact resistance, shifting the failure mode from brittle to ductile. Mesh polypropylene fibers with a length of 12 mm and a volume dosage of 1.0 % demonstrate excellent impact resistance, with initial and final crack numbers reaching 78 and 105, respectively. This represents an increase of 136.4 % and 200.0 % compared to the control concrete without fibers. The findings of this study offer new avenues for the resource utilization of solid waste and provide theoretical foundations and technical support for the potential application of solid waste based fiber-reinforced concrete in structural engineering.