Mechanical Property of Beam-to-Column Connection of Steel Structures With All-Steel Buckling-Restrained Braces

To avoid brittle fracture and plastic yielding of steel beam-to-column connections under earthquakes, a new beam-to-column connection of steel structures with all-steel buckling restrained braces (BRBs) is proposed. The all-steel BRB is connected to the steel beam and column members through pins to form a new connection system. Taking the T-shaped beam-to-column connection steel structure as the research object, two structural types with an all-steel BRB installed on one side (S-type) and two sides (D-type) are considered. Theoretical equations of the connection system’s initial stiffness and yield load are derived through the mechanical models. The yield load, main strain distribution, energy dissipation, and stiffness of the connection system are investigated through quasi-static tests to verify the connection system’s seismic performance. The tests revealed that the proposed new connection system is capable of achieving a stable hysteresis behavior. At the end of loading, the beam and column members are not damaged, and the plastic deformation is concentrated in the plastic energy dissipating replaceable BRB, and the beam and column basically remain elastic. The proposed equations approximately estimated the load response of the proposed connection system. The results show that the damage mode of this new connection system under seismic loading is BRB yielding, with an elastic response from the beam-column members.

FLEXURAL SIMULATION ANALYSIS OF RC T-GIRDERS STRENGTHED WITH POLYURETHANE CEMENT-PRESTRESSED STEEL WIRE ROPES

To verify the effectiveness of polyurethane cement-prestressed steel wire ropes for flexural reinforcement of reinforced concrete T-girders, this paper conducts flexural test research on 12 pieces of T-girder specimens. Through the ABAQUS finite element program to build a model for numerical simulation, the results show polyurethane cement prestressed steel wire rope reinforcement can significantly increase the yield load and ultimate load of reinforced girders. Taking a girder in the test (20mm reinforcement thickness of polyurethane cement) as an example, yield load and ultimate load increased by 61.5% and 102.3% compared to unreinforced girder. The finite element model calculation results of T-girder bending reinforcement are in good agreement with the bending reinforcement test, and the error is only about 2%. For different strength concrete, the yield load increases slightly with the increase of concrete strength. For T-girders with different reinforcement ratios, the bearing capacity of strengthened girders changes significantly with the increase of longitudinal reinforcement ratio. The yield load of girders with reinforcement ratio of 1.82% and 1.35% is 29.84% and 65.85% higher than that of girders with reinforcement ratio of 0.91%. The yield deflection is 13.18% and 3.99% higher than that of girders with reinforcement ratio of 0.91%. It can be concluded that the bending reinforcement method of polyurethane cement prestressed steel wire ropes can effectively strengthen the main girder and ensure the structural safety.

Yield Load Solutions for SE(B) Fracture Toughness Specimen with I-Shaped Heterogeneous Weld

The objective of this work was to investigate the fracture behavior of a heterogeneous I-shaped welded joint in the context of yield load solutions. The weld was divided into two equal parts, using the metal with the higher yield strength and the metal with the lower yield strength compared to base metal. For both configurations of the I-shaped weld, one with a crack in strength in the over-matched part of the weld and one for a crack in the under-matched part of the weld, a systematic study of fracture toughness SE(B) specimen was carried out in which the crack length, the width of the weld and the strength mismatch factor for both weld metals were varied, and the yield loads were determined. As a result of the study, two mathematical models for determination of yield loads are proposed. Both models were experimentally tested with one strength mismatch configuration, and the results showed good agreement and sufficiently conservative results compared to the experimental results.

Bearing Capacity of Concrete Filled Steel Tube Circular Arch under the Six-Point Uniformly Distributed Loading and Its Engineering Application

The influence of rise-span ratio on the bearing performance of concrete filled steel tube (CFST) circular arch was studied in this paper, three groups of CFST circular arch specimens with different rise-span ratios (0.154, 0.207, and 0.26) were selected, the six-point uniformly distributed loading was performed, and bearing performance experiments on CFST circular arch specimens with fixed ends were carried out. In this study, the ultimate bearing capacity and deformation failure characteristics of CFST circular arch specimens were obtained. The comparative analysis shows that the deformation evolution of CFST circular arch specimens has experienced compaction stage, elastic stage, elastic-plastic stage, and plastic stage. In the elastic-plastic and plastic deformation stages, the circular arch shows good ductility and bearing capacity. The bearing capacity of the circular arch is significantly affected by the rise-span ratio. Compared with circular arch specimens with a rise-span ratio of 0.154, the yield load of specimens with a rise-span ratio of 0.207 and 0.26 is increased by 50.8% and 61.5%, and the ultimate bearing capacity is increased by 42.7% and 68.3%, respectively. The larger the rise-span ratio, the greater the yield load and ultimate bearing capacity of the specimen and the stronger the deformation resistance of circular arch. The numerical simulation on the bending resistance process of circular arch was performed by ABAQUS to present the compression failure process of steel tube and core concrete. The simulation results are in good agreement with the experimental results. The experimental and simulation results show that the circular arch first yields at the inner side of the arch foot, and the curvature of different positions of the specimen is no longer consistent. When the ultimate bearing capacity is reached, the steel pipe at the arch foot obviously heaves, and the hooping effect of the steel pipe on the concrete is invalid. Based on the above research results, a closed composite support scheme of “bolt mesh shotcrete + vertical elliptical CFST support + steel fiber concrete shotcrete layer + reinforced anchor cable” was proposed for the extremely soft rock roadway and successfully applied in the Qingshuiying coal mine.

Tibial nerve stimulation increases vaginal blood perfusion and bone mineral density and yield load in ovariectomized rats

ABSTRACTHuman menopause transition and post-menopausal syndrome, driven by reduced ovarian activity and estrogen levels, are associated with an increased risk for symptoms including but not limited to sexual dysfunction, metabolic disease, and osteoporosis. Current treatments (both hormonal and non-hormonal) are limited in efficacy and may have adverse consequences, so investigation for additional treatment options is necessary. Previous studies have demonstrated that tibial nerve stimulation or electro-acupuncture near the tibial nerve are minimally invasive treatments that increase vaginal blood perfusion or serum estrogen in the rat model. In this study we examined the effects of twice weekly tibial nerve stimulation (0.2 ms pulse width, 20 Hz, 2x motor threshold) under ketamine-xylazine anesthesia in ovariectomized (OVX) female Sprague Dawley rats on menopause-associated physiological parameters. Rats were split into three groups (n = 10 per group): 1) intact control (no stimulation), 2) OVX control (no stimulation), and 3) OVX stimulation (treatment group). Tibial nerve stimulation did not increase serum estradiol levels, but transiently increased vaginal blood perfusion during stimulation for up to 5 weeks after OVX and increased areal bone mineral density and yield load of the right femur (side of stimulation) compared to the unstimulated OVX control. Additional studies to elucidate the full potential of tibial nerve stimulation on menopause-associated symptoms under different experimental conditions are warranted.SummaryPercutaneous tibial nerve stimulation increases vaginal blood perfusion, areal bone mineral density, and femur yield load in an ovariectomized rat model of menopause.

Knots Tied With High–Tensile Strength Tape Biomechanically Outperform Knots Tied With Round Suture

Background: Tape-type suture material is well-accepted in arthroscopy surgery. Purpose: To compare the knot security of a high–tensile strength round suture and high–tensile strength tape with commonly used arthroscopic knots. Study Design: Controlled laboratory study. Methods: We compared the performance of No. 2 braided nonabsorbable high-strength suture with that of 1.3-mm braided nonabsorbable high-strength tape. Five commonly used arthroscopic knots were investigated: the Roeder knot; the Western knot; the Samsung Medical Center (SMC) knot; the Tennessee knot; and a static surgeon’s knot. Seven knots were tied for each combination of knots and suture types. Knots were tied on a 30-mm circumferential metal post, and the suture loops were transferred to a materials testing machine. After preloading to 5 N, all specimens were loaded to failure. The clinical failure load, defined as the maximal force to failure at 3 mm of crosshead displacement, yield load, and stiffness, were recorded. A 2-way analysis of variance was used to determine differences between the groups. Results: Both suture type and knot type significantly affected the clinical failure load, yield load, and stiffness ( P = .002). The high-strength tape resulted in a significantly greater clinical failure load than the high-strength suture in the case of the Roeder knot, Western knot, and SMC knot ( P = .027, .005, and .016, respectively). When the high-strength round suture was used, the Roeder knot, Western knot, and SMC knot resulted in significantly smaller clinical failure loads compared with the Tennessee knot ( P = .011, .003, and .035, respectively) and the static surgeon’s knot ( P < .001 for all). When the high-strength tape was used, the Roeder knot, Western knot, and SMC knot resulted in significantly smaller clinical failure loads compared with the static surgeon’s knot ( P = .001, .001, and .003, respectively). Conclusion: The results of this study indicated that arthroscopic knots tied using 1.3-mm high-strength tape biomechanically outperformed knots tied using a No. 2 high-strength suture. While the static surgeon’s knot exhibited the best biomechanical properties, the Tennessee knot resulted in generally better biomechanical properties among the arthroscopic sliding knots. Clinical Relevance: Elongation and loosening of tied knots possibly affects the clinical results of repaired constructs.

Experimental research on shear performance of single bolt joints of bamboo curtain plywood

This paper focuses on the shear resistance of the bolted connection between steel plate and bamboo curtain plywood. From the fifteen groups of specimens, the performance grade, bolt diameter and end distance of bolts have an influence on the ultimate bearing capacity of joints and the yield load of joints and the yield load is 65%∼75% of the ultimate load. The initial stiffness of the node increases with the bolt diameter increasing. Provide certain materials and theoretical references for bamboo in the future design and research.

Biomechanical Comparison of a Prepared Thick Fresh Frozen Irradiated Fascia Lata Allograft to the Native Superior Capsule (212)

Objectives: Superior Capsule Reconstruction (SCR) has been described as treatment option for irreparable tears of the superior rotator cuff. Reported outcomes on the success of the surgery have been variable, with graft choice seeming to be one of the most important factors. Fascia Lata (FL) allograft has been proposed as a potential option as it provides adequate graft thickness while avoiding the morbidity of an autograft harvest. The purpose of this study was to compare the biomechanical characteristics of an SCR with FL allograft (FL-SCR) to a native superior capsule in a cadaveric specimen. Methods: Eight cadaver shoulder specimens were used. Each specimen was tested with a custom shoulder system twice. Initial testing was performed after the specimen was dissected of all soft tissue except for the native superior capsule. Subsequent testing was performed after FL-SCR was done. All allografts were fresh frozen and irradiated. Capsule and graft dimensions were recorded before testing. Biomechanical values recorded were cyclic and load to failure for both the native capsule and FL-SCR, and fixation displacement for the SCR-FL construct. A Paired T-test was performed to compare the biomechanical values of the native superior capsule to the FL-SCR. Results: The mean thickness of the NSC was 2.4 ± 0.6 mm and 7.4 ± 1.2mm for the FL graft. The native superior capsule had an average linear stiffness of 94.5 ± 20.4 N/mm, yield load of 386.9 ± 63.6 N, ultimate load of 444.9 ± 67.7 N and energy absorbed of 1418.4 ± 248.8 N-mm. The FL-SCR construct had an average linear stiffness of 28.0 ± 1.6 N/mm, yield load of 123.8 ± 54.3 N, ultimate load of 369.0 ± 43.4 N and energy absorbed of 5021.2 ± 755.1 N-mm. Comparing the two groups there was a statistically significant difference for stiffness (P = 0.013), yield load (P = 0.03) and energy absorbed (P = 0.003). There was no statistically significant difference between ultimate load. The total displacement of the FL-SCR fixation was 5.8 ± 0.6 mm after 1 cycle, 8.5 ± 0.7 mm after 30 cycles, 11.4 ± 1.8 mm at the yield load and 29.5 ± 1.8 mm at the ultimate load. For the failure mode, 8/8 NSC specimens failed at the mid-substance. The FL-SCR, 3/8 specimens failed at the suture tendon interface and 4/8 had medial anchor pull out. Conclusions: Performing SCR with FL allograft in a cadaver model creates a construct that is sufficiently strong enough to withstand normal physiologic loading of the shoulder, although it does not fully re-create the biomechanical characteristics of a native shoulder superior capsule.

Test and Numerical Analysis on Damaged Steel Beam Strengthened with Prestressed CFRP Sheet

This paper presents the experimental and numerical analysis of damaged steel beams strengthened with prestressed CFRP sheet or only strengthened with CFRP sheet. The test results showed that damaged level had a significant effect on the stiffness, yield load, and ultimate bearing capacity. And using prestressing CFRP sheet to strengthen damaged steel beam could increase the ultimate bearing capacity. The numerical analysis results showed that the damaged level had a significant effect on the stiffness and ultimate bearing capacity. The strengthened steel beam with the damaged level could exceed the steel beam without damage by about 10% in the ultimate bearing capacity. The ultimate bearing capacity would increase about 8% when the flange or web thickness increased per 1 mm. The ultimate bearing capacity would increase about 3% when the thickness or width of CFRP sheet increased per 0.05 mm or 10 mm. The bearing capacity would increase about 1.5% when the prestressed degree increased about 7%.

In Vitro Testing of 2 Adjustable-Loop Cortical Suspensory Fixation Systems Versus Interference Screw for Anterior Cruciate Ligament Reconstruction

Background: It is not clear whether the mechanical strength of adjustable-loop suspension devices (ALDs) in anterior cruciate ligament (ACL) reconstruction is device dependent and if these constructs are different from those of an interference screw. Purpose: To compare the biomechanical differences of 2 types of ALDs versus an interference screw. Study Design: Controlled laboratory study. Methods: ACL reconstruction was performed on porcine femurs and bovine extensor tendons with 3 types of fixation devices: interference screw, UltraButton (UB) ALD, and TightRope (TR) ALD (n = 10 for each). In addition to specimen testing, isolated testing of the 2 ALDs was performed. The loading protocol consisted of 3 stages: preload (static 150 N load for 5 minutes), cyclic load (50-250 N at 1 Hz for 1000 cycles), and load to failure (crosshead speed 50 mm/min). Displacement at different cycles, ultimate failure load, yield load, stiffness, and failure mode were recorded. Results: In specimen testing, displacement of the ALDs at the 1000th cycle was similar (3.42 ± 1.34 mm for TR and 3.39 ± 0.92 mm for UB), but both were significantly lower than that of the interference screw (7.54 ± 3.18 mm) ( P < .001 for both). The yield load of the UB (547 ± 173 N) was higher than that of the TR (420 ± 72 N) ( P = .033) or the interference screw (386 ± 51 N; P = .013), with no significant difference between the latter 2. In isolated device testing, the ultimate failure load of the TR (862 ± 64 N) was significantly lower than that of the UB (1879 ± 126 N) ( P < .001). Conclusion: Both ALDs showed significantly less displacement in cyclic loading at ultimate failure than the interference screw. The yield load of the UB was significantly higher than that of the other 2. The ultimate failure occurred at a significantly higher load for UB than it did for TR in isolated device testing. Clinical Relevance: Both UB and TR provided stronger fixation than an interference screw. Although difficult to assess, intrinsic differences in the mechanical properties of these ALDs may affect clinical outcomes.