Deformation Recovery Ability Research Articles

Static and fatigue behavior of shear connectors for a steel-concrete composite girder

As the key part of a steel-concrete composite bridge, the mechanical properties shear connectors that have direct impacts on the bearing capacity of the whole bridge. Angle connectors and twin-perfobond rib (T-PBL) connectors are commonly used in long-span steel-concrete composite bridges. Considering the convenience of construction, a new type of shear connector, the channel connector, is proposed. Push-out tests on three groups of 12 shear connector specimens under monotonic and repeated loads were carried out, and the static and fatigue behavior of the three different shear connectors were compared and analyzed. The results show that the ultimate bearing capacity of channel connectors is the largest, while that for the angle connectors is the second largest and that for T-PBL connectors is the smallest. With the increase in cyclic loading times, the ratio of residual deformation to plastic deformation shows a significant upward trend. The deformation recovery ability of the specimens decreases gradually, and the stiffness deteriorates continuously. The stiffness degradation of channel connectors is the slowest, and the stiffness degradation of angle connectors and T-PBL connectors is faster. The energy dissipation of T-PBL connectors is the largest, while the energy dissipation of angle and channel connectors is the same. The channel connectors proposed in this paper can be used as good shear connectors in steel-concrete composite bridges because of their strength improvement and their certain energy dissipation capacity. In addition, the 3D non-linear finite element models based on the three kinds of shear connectors is established to simulate the whole loading process by using the general finite element software ABAQUS. The results of finite element analysis are in good agreement with the experimental results, which can be used as a powerful supplement to the experimental research.

Experimental study on cyclic behavior of composite beam with corrugated steel web considering different shear-span ratio

This paper proposes an innovative use of corrugated steel plates as the webs of the crossbeam in the tower of a suspension bridge to get better seismic performance. Three 1/4-scaled models of composite beam with corrugated steel webs considering different shear-span ratio were fabricated to conduct quasi-static test. The structural behaviors including failure modes, hysteretic curves, ductility, strength and stiffness degradation, energy dissipation capacity, deformation recovery ability, shear force distribution and strain responses were investigated. Test results indicate that the specimen with large shear-span ratio presents ductile flexural failure, and the hysteretic curve is stable and plump with slight pinching, which indicates good energy dissipation performance. However, the specimen with small shear-span ratio fails due to brittle shear buckling of corrugated steel web, showing remarkable pinching phenomenon and poor hysteretic behavior. With the increase of shear-span ratio, the load-carrying capacity and lateral initial stiffness are reduced, but the ductility and energy dissipation ability are improved significantly. The energy dissipation capacity of such composite beam is better than that of the RC structures, the strength degradation is slight for the specimen with a proper shear-span ratio, and the deformation recovery ability is good for all test specimens. The corrugated steel web carries about 80% of the shear force and shear stress uniformly distributed along the web height. The test results demonstrate that the composite beam with corrugated steel web of a reasonable shear-span ratio can be applied in anti-seismic structure with superior energy dissipation performance. In addition, simplified formulas were proposed to evaluate the flexural strength and shear buckling strength of a composite beam with corrugated steel webs, the calculated results agree well with the test results, verifying the accuracy of these proposed formulas.

Polyurethane foams from chlorinated and non‐chlorinated metathesis modified canola oil polyols

ABSTRACTThe product of 1‐butene metathesis of canola triacylglycerol (CMTAG), with shortened structures, terminal double bonds (50% of the total), and oligomers (40% dimer and trimer, and 10% higher oligomers) was used to synthesize novel polyols and polyurethane foams. A non‐chlorinated (Pol‐1) and a chlorinated polyol (Pol‐2) having OH value (170 and 190 mg KOH/g, respectively) were synthesized from CMTAG by epoxidation followed by hydroxylation, and epoxidation followed by hydrogenation, respectively. Both polyols remained liquid below ambient temperature and demonstrated physical characteristics such as viscosity which allowed for the facile preparation of polyurethane foams. The foam obtained with Pol‐1 was relatively soft (∼0.32 MPa at 10% strain) and very flexible (recovery ∼90%); whereas, the foam obtained with Pol‐2 was semi‐rigid (∼1.1 MPa at 10% strain and recovery of 64%). The higher strength and rigidity of Pol‐2 foam compared to Pol‐1 foam is chiefly attributable to the effect of the bulky chlorines on the crosslink density. Importantly, this work highlights that one can improve and control jointly the mechanical properties and deformation recovery ability of bio‐based foams by combining primary functional groups, oligomers, and high molar volume molecules in the polyols. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46616.

Self-healing and moldable material with the deformation recovery ability from self-assembled supramolecular metallogels.

A self-assembled non-covalent metallogel system with self-healing, deformation recoverable, moldable and bottom-up load-bearing properties was prepared using tetrazolyl derivatives and Pd(OAc)2.

Fabrication and Characterization of Porous Tubular Silk Fibroin Scaffolds

Silk fibroin (SF) has been one of promising resources of biotechnology and biomedical materials due to its unique properties. Here, different sizes of porous tubular scaffolds were fabricated from a SF aqueous solution with the addition of poly(ethylene glycol diglycidyl ether) (PGDE). The scaffolds were generally flexible and transparent at the wet state with a pore size of 81–128 μm and porosity of 90–96%, depending on the concentrations of SF and PGDE. The mechanical properties measurement showed that the tubular SF scaffolds had satisfying tensile and compression properties, especially the excellent deformation–recovery ability. FT-IR spectra indicated that the SF in the tubular scaffolds was in a β-sheet structure, and no PGDE characteristic band was observed, suggesting that the PGDE could be removed from the scaffolds by soaking in deionized water. The cell compatibility of scaffolds was evaluated, and no obvious cytotoxicity to mouse L-929 fibroblasts was detected.

Superelasticity decay of porous NiTi shape memory alloys under cyclic strain-controlled fatigue conditions

This paper presents some recent results on fatigue and pore deformation behavior of a porous superelastic NiTi shape memory alloy (SMA), fabricated by capsule-free hot isostatic pressing, under cyclic compression strain; and a systematical comparison was made with that of the dense NiTi SMA. The results show that the porous NiTi SMA has very good deformation recovery ability, in terms of a linear superelasticity as high as 4%. Under a high-cyclic strain level applied, the irrecoverable pore deformation occurs, which results in residual strain; and the degradation of superelastic effect only occurs in the first fatigue cycle, thereafter the good linear superelasticity is maintained. It has been shown that the fatigue of the porous NiTi SMA occurs at a relatively lower strain level compared with the dense one.