Ultrasonic pulse velocity (UPV) and rebound hammer (RH) tests are often used for assessing the quality of concrete and estimation of its compressive strength. Several parameters influence this property of concrete as ...Ultrasonic pulse velocity (UPV) and rebound hammer (RH) tests are often used for assessing the quality of concrete and estimation of its compressive strength. Several parameters influence this property of concrete as the type and size of aggregates, cement content, the implementation of concrete, etc. To account for these factors, both of the two tests are combined and their measurements are calibrated with the results of mechanical tests on cylindrical specimens cast on site and on cores taken from the existing structure in work progress at the new-city Massinissa El-Khroub Constantine in Algeria. In this study;the two tests cited above have been used to determine the concrete quality by applying regression analysis models between compressive strength of in situ concrete on existing structure and the nondestructive tests values, the combined method is used, equations are derived using statistical analysis (simple and multiple regression) to estimate compressive strength of concrete on site and the reliability of the technique for prediction of the strength is discussed for this case study.展开更多
The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economic...The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength.Furthermore, the Poisson's ratio has no correlation with any of the direct and indirect test results.展开更多
We used the finite element method (FEM) to investigate the stress profiles of vertebrae in patients who underwent balloon kyphoplasty (BKP) for vertebral fracture. BKP is often performed for persistent pain after vert...We used the finite element method (FEM) to investigate the stress profiles of vertebrae in patients who underwent balloon kyphoplasty (BKP) for vertebral fracture. BKP is often performed for persistent pain after vertebral fractures. However, fractures are frequently reported in the adjacent vertebrae after BKP. The purpose was to clarify the mechanism of fractures that occur in the adjacent vertebrae after BKP. The subjects were two patients (first case: 74-year-old woman;second case: 88-year-old woman) who had BKP for osteoporotic vertebral fractures (L1). A bone analysis software program, Mechanical Finder, was used to construct three-dimensional finite element models (T11-L3) from computed tomographic (CT) digital imaging and communications in medicine (DICOM) data. Moment loadings were examined to evaluate stress concentrations on the vertebrae. Young’s moduli were lower in the second case than in the first case at all vertebral levels. Maximum Drucker-Prager stresses after BKP were larger in the second case than in the first case for compression, flexion, extension, and axial rotation. Strain energy density decreased in L1 and increased in the adjacent ver-tebrae. Our results suggest that post-BKP fractures of the adjacent vertebrae not only are due to bone fragility, but also can be caused by increased rigidity in the vertebrae filled with bone cement, which increases stress concentration on the adjacent verte-brae and raises the likelihood of fracture.展开更多
文摘Ultrasonic pulse velocity (UPV) and rebound hammer (RH) tests are often used for assessing the quality of concrete and estimation of its compressive strength. Several parameters influence this property of concrete as the type and size of aggregates, cement content, the implementation of concrete, etc. To account for these factors, both of the two tests are combined and their measurements are calibrated with the results of mechanical tests on cylindrical specimens cast on site and on cores taken from the existing structure in work progress at the new-city Massinissa El-Khroub Constantine in Algeria. In this study;the two tests cited above have been used to determine the concrete quality by applying regression analysis models between compressive strength of in situ concrete on existing structure and the nondestructive tests values, the combined method is used, equations are derived using statistical analysis (simple and multiple regression) to estimate compressive strength of concrete on site and the reliability of the technique for prediction of the strength is discussed for this case study.
基金CDC/NIOSH for their partial funding of this work
文摘The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength.Furthermore, the Poisson's ratio has no correlation with any of the direct and indirect test results.
文摘We used the finite element method (FEM) to investigate the stress profiles of vertebrae in patients who underwent balloon kyphoplasty (BKP) for vertebral fracture. BKP is often performed for persistent pain after vertebral fractures. However, fractures are frequently reported in the adjacent vertebrae after BKP. The purpose was to clarify the mechanism of fractures that occur in the adjacent vertebrae after BKP. The subjects were two patients (first case: 74-year-old woman;second case: 88-year-old woman) who had BKP for osteoporotic vertebral fractures (L1). A bone analysis software program, Mechanical Finder, was used to construct three-dimensional finite element models (T11-L3) from computed tomographic (CT) digital imaging and communications in medicine (DICOM) data. Moment loadings were examined to evaluate stress concentrations on the vertebrae. Young’s moduli were lower in the second case than in the first case at all vertebral levels. Maximum Drucker-Prager stresses after BKP were larger in the second case than in the first case for compression, flexion, extension, and axial rotation. Strain energy density decreased in L1 and increased in the adjacent ver-tebrae. Our results suggest that post-BKP fractures of the adjacent vertebrae not only are due to bone fragility, but also can be caused by increased rigidity in the vertebrae filled with bone cement, which increases stress concentration on the adjacent verte-brae and raises the likelihood of fracture.
