The effects of replacing calcined clay with sewage sludge ash (SSA) treated under room temperature and high temperature ranging from 500 °C to 900 °C in limestone calcined clay cement (LC3) have been investigated in this paper. The optimal calcination temperature for SSA was found to be 800 °C based on the results of strength and microstructure observations. The main inorganic components of sludge ash are Fe₂O₃, SiO₂, Al₂O₃, and CaO, which are very similar to the components of calcined clay in LC3, but with a very high content of Fe₂O₃ (55–61%) and P₂O₅ (9–10%). With different levels of the replacement of calcined clay with calcined SSA, setting time, compressive strength, XRD, TG/DSC, and SEM analyses of the modified LC3 pastes were conducted to identify the chemical compositions, physical properties, hydration products, microstructure, and the heavy metal contaminants within the pastes, which were compared to the results for normal LC3 paste. The incorporation of SSA significantly altered the morphologies of Ca(OH)₂ and CaCO₃, as well as modified the microstructure of the LC3 paste. In comparison to the pure OPC group, the LC3 pastes containing SSA exhibited a reduced Ca(OH)₂ content and an increased CaCO₃ content. Furthermore, the modified LC3 pastes with calcined SSA effectively facilitated the immobilization of heavy metal ions in SSA. The findings indicate the potential viability of utilizing calcined SSA as a replacement for calcined clay in LC3.

Sludge is a semi-solid waste generated during the process of wastewater treatment. Due to the addition of polymerized ferric chloride in the flocculation process, the sludge produced by the sewage treatment plant in Liaocheng Jiaming Industrial Park contains a high content of iron oxide. In this paper, chemical analysis and particle size analysis of local sludge and sludge ash were conducted. In order to assess the potential of substituting cement as cementitious material with different dosages of sludge or sludge ash with high iron oxide content, setting time, compressive strength, microscopic analysis using microscopic testing (XRD, TG/DTG, SEM) and a toxicity characteristic leaching procedure (TCLP) were analyzed. These procedures determined the physical properties, compressive strength, hydration products, microstructure, and heavy metal contaminants of cement slurries replaced by local sludge or sludge ash with different dosages of high iron oxide content. The results show that less than 5% of local sludge or sludge ash can be incorporated into cement slurry as an alternative cementitious material for solid waste disposal.

Surrounding rock pressure, water pressure, and joint roughness are the important factors that affect the fractured rock mass seepage. It is of great significance to quantify the influence of these factors through experiments. In this study, rock fracture joint surfaces were measured. Next, 3D coordinates of joint surfaces were extracted with using the Geomagic software, and joint roughness was described using the mean variance of protrusion height and equidistant fluctuation angle, which were acquired through calculation. Stress-seepage coupling test was then conducted on the samples on a triaxial apparatus, and the effects of confining stress and water pressure on the permeability of single-fracture rock were investigated. On the basis of the relationship between the parameters in data fitting expression and the mean variance of protrusion height and equidistant fluctuation angle, the calculation formula of the permeability coefficient including joint roughness, confining pressure, and seepage pressure difference was derived.

In situ dynamic testing is conducted to study the dynamic characteristics of the wooden structure of the North House main hall. The velocity response signals on the measurement points are obtained and analyzed using the self-interaction spectral method and stochastic subspace method, yielding natural frequencies, mode shapes, and damping ratios. This study reveals that the natural frequencies and damping ratios are highly consistent between the two methods. Therefore, to eliminate errors, the average of the results from both modal identification methods is taken as the final measured modal parameters of the structure. The natural frequencies of the first and second order in the X direction were 2.097 Hz and 3.845 Hz and in the Y direction were 3.955 Hz and 5.701 Hz. The modal frequency in the Y direction of the structure exceeds that in the X direction. Concurrently, a three-dimensional finite element model was established using ANSYS 2021R1, considering the semi-rigid properties of mortise–tenon connections, and validated based on in situ dynamic testing. The sensitivity analysis indicates adjustments to parameters such as beam–column elastic modulus, tenon–mortise joint stiffness, and roof mass for finite element model refinement. Modal parameter calculations from the corrected finite element model closely approximate the measured modal results, with maximum errors of 9.41% for the first two frequencies, both within 10% of the measured resonant frequencies. The adjusted finite element model closely matches the experimental results, serving as a benchmark model for the wooden structure of North House main hall. The validation confirms the rationality of the benchmark finite element model, providing valuable insights into ancient timber structures along transportation routes.

In the paper, a simple-supported wooden beam is used as the research object to identify the damage of the wood beam by finite element analysis and experimental research. First, ANSYS was used to establish the solid finite element model of the wood beam before and after the damage, and then the discrete wavelet transform was performed on the curvature mode of the wood beam before and after the damage, and the wavelet coefficient difference index was obtained after obtaining the high frequency wavelet coefficients. Then, the damage location of the wood beam was judged according to the sudden peak of the wavelet coefficient difference index, and the damage degree of the wood beam was estimated by fitting the relationship between the wavelet coefficient difference index and the degree of damage. Finally, the index was verified by the wooden beam test. The results show that the wavelet coefficient difference index can accurately identify the damaged location of the wood beams. The degree of damage to the wood beams at the damage location can be quantitatively estimated by fitting the relationship between the wavelet coefficient difference index and the degree of damage at the damage location. The research results provide a theoretical basis to identify wooden beam damage.

This study completely investigates the damage detection problem based on strain modal characteristics using simply supported wooden beams as the research object. First, modal analysis was performed, and finite element models of both damaged and undamaged timber beams were created using ABAQUS. Second, a number of strain modal characteristics (strain modal, strain modal difference, and strain modal curvature difference) were used to identify the damage to the wooden beam construction. Lastly, the modal parameters of the wooden beam under various damage scenarios were ascertained using damage identification experiments, and the test results were contrasted with those obtained from a numerical simulation. The findings showed that, while each of the three damage identification indices has a distinct identification effect, they can all locate the damage to wooden beams. Strain mode curvature difference > strain mode difference > strain mode is the order of them. The results of this study can be used as a reference to identify damage to timber beams in the future.