Flexural Strength Evaluation of Multi-Cell Composite T-Shaped Concrete-Filled Steel Tubular Beams.

The multi-cell composite T-shaped concrete-filled steel tubular (MT-CFST) element is an innovative structural form. It has great potential for construction applications because of favorable advantages over traditional composite elements. The flexural strength of MT-CFST beams was investigated in this study to provide recommendations in line with existing design codes. First, formulations to evaluate the flexural strength of MT-CFST beams were derived based on the Unified Theory and plastic stress distribution method (PSDM). For the Unified Theory-based formula, a modified confinement effect factor that considers the shape of a cross-section was proposed. An experimental study on the flexural behavior of six MT-CFST beams as well as two hollow section counterparts was conducted. The influence of bending moment direction, concrete infill, wall thickness, and cross-section sizes were investigated. The accuracy of the proposed formulations was verified against the test results and numerical results from finite element modeling. The comparisons showed that the formula in line with the Unified Theory provided more accurate predictions with reasonable conservatism for the studied MT-CFST beams.

Scattered Dose to Ovary From Radiotherapy for Neuroblastoma in Female Children.

PURPOSE: To measure the scattered dose to ovary from radiotherapy for neuroblastoma in female children and to evaluate the relevant risks for radiation-induced ovarian damage. MATERIAL AND METHODS: Radiotherapy for child neuroblastoma was simulated on the water phantom. The scattered dose to ovary is measured by ionization chamber on the linear accelerator with 3-dimensional conformal radiation therapy and intensity-modulated radiation therapy treatment producing 6MV and 10MV X-rays. The treatment planning procedure was carried out on a computer system (TPS, Oncentra). Optimization of the number and orientation of beams were performed in order to minimize the ovarian dose. RESULTS: For the target dose of 21.6 Gy, the scattered dose to ovary was ranged from 1.3 to 46.8 cGy depending on the treatment method and the energy of the beams. The ovarian dose of intensity-modulated radiation therapy is 1.32 to 1.64 times higher than that of 3-dimensional conformal radiation therapy. The ovarian dose of 6MV beam's energy is 1.52 to 1.64 times higher than that of 10MV beam's energy. For the radiotherapy, the scattered dose of ovaries on phantom by ionization chamber was 1.40 to 2.32 times higher than that on TPS calculated. CONCLUSION: The dosimetric data suggest that pediatric radiotherapy is not associated with a risk for permanent damage to the ovaries in female children. Through choosing the beams' energy and treatment plan's method, the scattered dose of ovaries can be reduced. The risk for development of hereditary disorders in offspring conceived after exposure is low.

[A bi-isocentric irradiation technique in radiotherapy for nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: Although the problem of fields gap in radiotherapy for nasopharyngeal carcinoma (NPC) was solved by mono-isocentric technique, the dose distribution was heterogeneous with "hot" and/or "cold" spots. This study was to explore the best way to solve the problems of both fields gap and dose distribution using bi-isocentric technique. METHODS: Mono-isocentric and bi-isocentric irradiation techniques were used to simulate irradiation, respectively. Mono-isocentric irradiation technique was used to design the beam-split facio-upper neck field and the tangential low neck-supraclavicular field at the match plane. Bi-isocentric irradiation technique was used to design the facio-upper neck field and the tangential low neck-supraclavicular field at the match plane, namely the upper border of the tangential field and the lower border of the facio-upper neck fields. RESULTS: Both mono-isocentric and bi-isocentric irradiation techniques were conformed well to QA at the junction of the neighboring portals, without "hot" or "cold" spots, by dosimetry. But the CADplan Three Dimensions Treatment Planning System showed that the dose distributional uniformity of sagittal plane in nasopharynx was much better in bi-isocentric technique than in mono-isocentric irradiation technique, without cold region in gross tumor volume (GTV) and/or hot region in normal tissue. CONCLUSIONS: Bi-isocentric irradiation technique takes a perfect match-plane and a satisfied dose distributional uniformity.