ABSTRACT
In this study, the hysteretic behavior of a novel frictional energy dissipation steel truss (FED-ST) is examined. The proposed FED-ST incorporates a friction damper with brass as the friction material into the top chord of traditional truss to improve the seismic performance of the staggered truss framing systems. A FED-ST specimen with a scale of 1:2.5 was subjected to a hysteresis test. The hysteretic behavior, ductility, and energy dissipation capability were analyzed considering the test findings. It is demonstrated that the FED-ST specimen has favorable ductility and an energy dissipation capacity that is 7.3 times more than that of a conventional truss specimen. The test findings were then used to compare and validate a finite element (FE) model. The FE analysis results are in strong agreement with the test results, demonstrating the validity of the modeling approach. To further investigate the impact of the cover plate width on the behavior of the FED-ST, preliminary parametric research was also carried out.
ABSTRACT
To improve the seismic performance of a staggered truss steel framing system, the basic force unit in the truss system is replaced by a friction energy dissipation truss. The difference between a friction energy dissipation truss and an ordinary truss is that the upper chord is a friction energy dissipation composite chord. In this paper, we investigate the effects of the number of bolts and the friction surface on the energy dissipation capacity of the chord by a quasi-static test on six composite chord specimens at a scale of 1:2. The results show that the hysteresis curves of friction energy dissipation composite chords are ideal rectangles, and the energy dissipation capacity is excellent. The more bolts there are in the specimen, the slower the energy dissipation capacity of the chord decreases. Among the different friction surface specimens, the energy dissipation capacity of the aluminum friction plate specimen decays the fastest, while the energy dissipation capacity of the shot-blasted treated specimen decays substantially after the first cycle. Friction plates can improve the stability of the hysteresis properties. Based on the test results, this paper proposes a calculation method for the ultimate bearing capacity of the composite chord, which provides a basis for the design of a friction energy dissipation truss. In addition, we studied the effects of different bolt clamping forces and slotted bolt hole lengths on the energy dissipation capacity of composite chords by establishing a finite element analysis. It was shown that as the clamping force of the bolt increases, the energy dissipation capacity of the specimen becomes stronger but the stability decreases. The energy dissipation capacity of the chord is close to a linear relationship with the slotted bolt hole lengths; thus, increasing the slotted bolt hole lengths within the allowable range of inter-story drifts can enhance the energy dissipation capacity of the chord. Finally, we propose the design method of the angle steel by analyzing the force of the chord.
ABSTRACT
Phyllostachys edulis (P. edulis) bamboo is the most widely distributed and used bamboo species, and it is an ideal building material. With the in-depth implementation of the sustainable development strategy, modern bamboo structures have broad application prospects in green buildings. In order to promote the efficient utilization of bamboo resources and facilitate the design and application of bamboo structures, the bending strength test and classification of P. edulis bamboo were carried out, the factors affecting the reliability were analyzed, and the design values of the bending strength of P. edulis bamboo were proposed based on the reliability analysis. The research results show that dividing P. edulis bamboo into three levels (grade I, grade II, and grade III) can achieve efficient use of P. edulis bamboo resources; 75% fitting data points and normal distribution were used to analyze the reliability of the bending strength of P. edulis bamboo. The analysis of factors affecting reliability makes the calculation of strength design values more reliable. The reliability increases with the increase of the load ratio and the partial factor for resistance. Under the same load ratio and reliability, the partial factor for resistance of the combination of constant load and snow load is the largest, and the partial factor for resistance of the combination of constant load and office building load is the smallest. Under the same load combination and reliability, the partial factor for resistance decreases as the load ratio increases. Under the same load ratio and load combination, the partial factor for resistance of grade III is the largest, and grade I is the smallest. The bending strength design values of grade I, grade II, and grade III are 29.54 MPa, 29.62 MPa, and 30.63 MPa, respectively. This paper innovatively proposed the design values of bending strength of P. edulis bamboo based on classification. The P. edulis bamboo grading method established in this paper and the bending strength design values of P. edulis bamboo proposed can provide references for the design and engineering application of bamboo structures.
ABSTRACT
BACKGROUND: Total flavonoids of Rhizoma drynariae (TFRD), a Chinese medicine, is widely used in the treatment of orthopedic diseases. However, there are few basic and clinical studies on the effect of TFRD on induced membrane technique (Masquelet technique). PURPOSE: This trial is to explore effects of TFRD on vascularization of the induced membrane, and mineralization of the bone graft in rats with femoral bone defects. STUDY DESIGN AND METHODS: Forty-eight Sprague-Dawley rats were randomly divided into high dose group (H-TFRD), medium dose group (M-TFRD), low dose group (L-TFRD) and control group (control). The segmental bone defects were established with 12 rats in per group. The polymethyl methacrylate (PMMA) spacer was implanted into the femoral bone defect of rats in the first-stage surgery. About 4 weeks after first-stage surgery, induced membranes of 6 rats in each group were selected. The blood vessels and angiogenesis-related factors in the induced membrane were analyzed by hematoxylin-eosin (HE) and masson staining, western blot, qPCR and immunohistostaining. The remaining rats in per group underwent second-stage surgery (bone grafting). Twelve weeks after the bone grafting, the bone tissues was examined by X-ray, micro-computed tomography (Micro-CT), HE staining and enzyme-linked immunosorbent assay (ELISA) to evaluate the growth of the bone graft. Meanwhile, the TFRD-containing serum was collected from rats to culture osteoblasts in vitro. Cell Counting Kit-8 (CCK-8) method, Alizarin Red S (ARS) staining, western blot and immunofluorescence were used to detect effects of TFRD on the osteoblasts' proliferation and BMP-SMAD signaling pathway. RESULTS: Compared with the L-TFRD and control groups, the number of blood vessels and the expression of angiogenesis-related factors (VEGF, TGF-ß1, BMP-2, PDGF-BB and CD31) were higher in the H-TFRD and M-TFRD groups. The Lane-Sandhu X-ray score, bone mass and growth rate of the bone graft in the H-TFRD and M-TFRD groups were significantly better than those in the L-TFRD and control groups. In addition, medium and high doses of TFRD significantly increased the expression of BMP-SMAD pathway proteins (BMP-2, SMAD1, SMAD4, SMAD5 and RUNX2) in rat serum and bone graft. In vitro, after osteoblasts were intervened with TFRD-containing serum from the H-TFRD and M-TFRD groups, the cell viability, the number of mineralized nodules and the phosphorylation of BMP-SMAD pathway proteins were markedly increased. CONCLUSION: TFRD could promote the formation of blood vessels and the expression of angiogenesis-related factors during the formation of the induced membrane. During the growing period of bone graft, it could facilitate the growth and mineralization of bone graft in a dose-dependent manner, which is partly related to the activation and phosphorylation of BMP-SMAD signaling pathway.
ABSTRACT
[This corrects the article DOI: 10.3389/fphar.2021.675470.].
ABSTRACT
Total flavonoids of Rhizoma drynariae (TFRD), a Chinese medicine, is widely used in the treatment of fracture, bone defect, osteoporosis and other orthopedic diseases, and has achieved good effects. Purpose of this trial was to explore efficacy of TFRD on bone graft's mineralization and osteoblasts' differentiation in Masquelet induced membrane technique in rats. Forty male Sprague-Dawley rats were randomly divided into high dose group (H-TFRD), middle dose group (M-TFRD), low dose group (L-TFRD) and control group (control). The critical size bone defect model of rats was established with 10 rats in each group. Polymethyl methacrylate (PMMA) spacer was implanted into the defect of right femur in rats. After the formation of the induced membrane, autogenous bone was implanted into the induced membrane. After 12 weeks of bone graft, bone tissues in the area of bone graft were examined by X-ray, Micro-CT, hematoxylin-eosin (HE) and Masson trichrome staining to evaluate the growth of the bone graft. The ß-catenin, c-myc, COL1A1, BMP-2 and OPN in bone graft were quantitatively analyzed by Western blot and Immunohistostaining. Osteoblasts were cultured in the medium containing TFRD. Cell Counting Kit-8 (CCK-8) method, Alkaline phosphatase (ALP) and Alizarin Red S (ARS) staining, Western blot, RT-PCR and other methods were used to detect the effects of TFRD on the proliferation of osteoblasts and the regulation of Wnt/ß-catenin signaling pathway. In vivo experiments showed that the growth and mineralization of bone graft in TFRD group was better. Moreover, the expression of Wnt/ß-catenin and osteogenesis-related proteins in bone tissue of TFRD group was more than that in other groups. In vitro experiments indicated that osteoblasts proliferated faster, activity of ALP was higher, number of mineralized nodules and proteins related to osteogenesis were more in TFRD group. But blocking Wnt/ß-catenin signaling pathway could limit these effects. Therefore, TFRD could promote mineralization of bone graft and differentiation of osteoblasts in a dose-dependent manner during growing period of the bone graft of induced membrane technique, which is partly related to the activation of Wnt/ß-catenin signaling pathway.
ABSTRACT
OBJECTIVE: To compare clinical efficacy of autologous platelet-rich plasma combined with bone grafting and bone grafting in repairing bone defects on the second phase of induced membrane. METHODS: From January 2013 to September 2017, clinical data of 35 patients with bone defects treated by induced membrane technique were retrospectively analyzed. According to different surgical methods, the patients were divided into two groups. In group A, there were 18 patients, including 11 males and 7 females, aged from 17 to 61 years old with an average of(40.4±13.4) years old, the length of bone defect ranged from 3.6 to 18.0 cm with an average of (9.5±4.4) cm; and treated with platelet-rich plasma combined on the second-stage operation. In group B, there were 17 patients, including 11 males and 6 females, aged from 21 to 56 years old with an average of(43.1±12.3) years old, the length of bone defect ranged from 3.1 to 16.3 cm with an average of (9.1±3.7) cm; and treated with simple bone grafting. Operation time, amount of intraoperative blood loss, fracture healing time, the number of bone healing, the number of infection, and the number of complications were compared between two groups. RESULTS: All patients were followed up for 13 to 39 months with an average of(21.3±1.2) months. Operation time and blood loss in group A was(76.11±25.00) min, (78.89±14.91) ml, and in group B was (65.29±29.66) min, (79.41±20.45) ml; there were no statistical difference between two groups(P>0.05). According to imaging results, clinical healing time of bone in group A was (28.78±9.40) weeks, (36.17±9.68) weeks in group B, and had difference between two groups (t=2.294, P=0.028); there was no statistical difference in numbers of fracture healing between group A (17 cases) and group B (14 cases) (χ²=0.430, P=0.512). One patient in group A occurred infection and 6 patients in group B occurred infection, and had statistical difference between two groups (χ²=4.833, P=0.028). Two patients in group A occurred complications and 9 patients in group B occurred complications, which had difference between two groups (χ²=7.098, P=0.008). CONCLUSIONS: In the induction membrane technique, autologous platelet-rich plasma combined with bone grafting has obvious advantages in treating bone defects, shortening fracture healing time and reducing incidence of complications.