Quantized wrinkles and fracture of stiff membranes on soft films

Stiff membranes on soft substrates may wrinkle and fold during compression1-11, but the strong post-buckling nonlinearity3,12 and the propensity of overall bending of these systems4,9,11 under large compression make the intriguing morphological evolution ill-controlled and less understood. Here, we present a simple peeling strategy that controllably makes stiff nanomembranes on soft microfilms wrinkled, then folded with a preset period, and ultimately fractured into regular ribbons. The fold and fracture periods exhibit a quantized, stepped dependence on the microfilm thickness, with the period doubled per step. The controlled wrinkle-to-fold-to-fractures transitions can be quantified by both computations and a scaling law, showing generality to different forms of compressive loading. This quantized wrinkle evolution deepens our understanding of complex behaviors of such natural and artificial systems as cerebral cortexes, skins, and coating materials, and opens a way to advanced manufacturing by fracturing large-area nanomembranes into uniformly shaped microflakes.

Seismic design of liquid-containing concrete structures

The seismic design of structures is a requirement for any places [sic] where earthquake [sic] occurs, and the design is based upon the codes that vary according to the jurisdictions in which the code was developed for. This study introduces and assesses the document ACI 350.3-06 which was developed by the ACI Committee to guide the design of liquid containing structures, and compares to other codes such as ACI 350.3-01 and NZS 3106 of New Zealand Standard. The importance of liquid containing structures cannot be stressed further, as it is apparent in nuclear applications. The failure of tanks could be due to many reasons: 1) Shell buckling, caused by axial compression due to overall bending. 2) Roof damage as a result of sloshing of the upper portion of the containing liquid due to insufficient provision of freeboard. 3) Failure of inlets and outlets due to their inability to accommodate the deformations of the flexible tank. 4) Differential settlement or failure of supporting soil. The pressures resulted from earthquake [sic] can cause catastrophic disaster, and they [sic] are the impulsive and convective mode which exerts pressures on the walls of the tank. The hydrodynamic model used to estimate these pressures in the ACI 350.3-06 document has also adopted earlier works from Housner, Veletsos, and Shivakumar. Throughout the years, the code has transformed tremendously, and this study shows that the codes are very similar in many ways, yet their differences can yield significantly different results. Furthermore, the results from the various codes are illustrated using the same example, and the validity of the results are determined as well. The effects on seismic design due to the types of structure, whether the tank is rigid or flexible, and the support system are also introduced; moreover, their absences and the variations in the estimation of seismic parameters in some codes are also shown to have a large effect on the load estimation.

Seismic design of liquid-containing concrete structures

The seismic design of structures is a requirement for any places [sic] where earthquake [sic] occurs, and the design is based upon the codes that vary according to the jurisdictions in which the code was developed for. This study introduces and assesses the document ACI 350.3-06 which was developed by the ACI Committee to guide the design of liquid containing structures, and compares to other codes such as ACI 350.3-01 and NZS 3106 of New Zealand Standard. The importance of liquid containing structures cannot be stressed further, as it is apparent in nuclear applications. The failure of tanks could be due to many reasons: 1) Shell buckling, caused by axial compression due to overall bending. 2) Roof damage as a result of sloshing of the upper portion of the containing liquid due to insufficient provision of freeboard. 3) Failure of inlets and outlets due to their inability to accommodate the deformations of the flexible tank. 4) Differential settlement or failure of supporting soil. The pressures resulted from earthquake [sic] can cause catastrophic disaster, and they [sic] are the impulsive and convective mode which exerts pressures on the walls of the tank. The hydrodynamic model used to estimate these pressures in the ACI 350.3-06 document has also adopted earlier works from Housner, Veletsos, and Shivakumar. Throughout the years, the code has transformed tremendously, and this study shows that the codes are very similar in many ways, yet their differences can yield significantly different results. Furthermore, the results from the various codes are illustrated using the same example, and the validity of the results are determined as well. The effects on seismic design due to the types of structure, whether the tank is rigid or flexible, and the support system are also introduced; moreover, their absences and the variations in the estimation of seismic parameters in some codes are also shown to have a large effect on the load estimation.

Experimental and Numerical Study of Lattice Girder Composite Slabs with Monolithic Joint

This paper studies the behavior of lattice girder composite slabs with monolithic joint under bending. A full-scale experiment is performed to investigate the overall bending resistance, deflection and the final crack distribution of latticed girder composite slab under uniformly distributed load. A finite element model is given for the analysis of the latticed girder composite slabs. The effectiveness and correctness of the numerical simulations are verified against experimental results. The experimental and numerical studies conclude that the lattice girder composite slabs conform to the requirement of existing design codes. A parametric study is provided to investigate the effects of lattice girder with following conclusions: (a) the lattice girder significantly increases the stiffness of the slab when comparing with the precast slab without reinforcement crossing the interface; (b) the additional reinforcement near the joint slightly increases the stiffness and resistance, while it prevents damage near the joint.

Physico-mechanical and joint performance of bamboo veneer products manufactured by mould pressing

Bamboo can be processed into engineering materials with excellent properties by reasonable processing methods. In this study, the performance of mould-pressed bamboo (MBP) veneer products was examined. The physical mechanical properties and connection properties of MPB were tested, and the application performance of the MPB was analyzed. The results show that MPB has a comprehensive property of high internal bonding and good dimensional stability, and its density and mechanical properties are similar to those of wood dimensional stock. The overall bending strength, bending modulus, and compression strength of MPB were 29.0 MPa, 6.83 GPa, and 15.6 MPa, respectively. While the overall carrying capacity was relatively low, the connection performance of BPM was good. Thus, it can be used as a connector or substructure.

Low-velocity impact of multilayer sandwich beams with metal foam cores: Analytical, experimental, and numerical investigations

This paper uses the analytical, experimental and numerical methods to investigate the low-velocity impact response of fully clamped multilayer sandwich beams with metal foam cores struck by a heavy mass. Using the quasi-static method, analytical solutions for dynamic response of the fully clamped multilayer sandwich beams are derived including the interaction between bending and stretching induced by large deflections. Effects of local denting and core strength on the overall bending are considered. The low-velocity impact experiments and numerical calculations are carried out to validate the analytical model. The present analytical model captures experimental and numerical results reasonably. It is shown that the energy absorption of multilayer sandwich beams increases with decrease of multilayer factor and increase of the core strength.

Assessing fragility of a reinforced concrete element to snow avalanches using a non-linear mass-spring model

This paper presents an assessment of the fragility of a Reinforced Concrete (RC) element subjected to avalanche loads within a reliability framework. In order to obtain accurate numerical results with supportable computation times, we propose a light and efficient Single-Degree-Of-Freedom (SDOF) numerical model for an RC element. The model represents the behavior of an RC wall, summing up the main physics involved. Non-linearity was taken into account by a moment-curvature approach, which describes the overall bending response until collapse. The SDOF model was validated by a finite element as well as yield line theory analyses. It was then embedded within a reliability framework to evaluate the failure probability as a function of avalanche pressure. Several reliability methods were implemented and compared, suggesting that non-parametric methods provide significant results at a moderate level of computational burden. The sensitivity to material properties, such as tensile and compressive strengths, steel reinforcement ratio, and wall geometry was also investigated. Finally, the obtained fragility curves were discussed with respect to the few proposals available in the snow avalanche engineering field. This systematic approach will prove useful in refining formal and practical risk assessments and could be applied to other phenomena that also lack fragility curves.

Simplified Analytical Methods to Analyze Lock Gates Submitted to Ship Collisions and Earthquakes

This paper presents two simplified analytical methods to analyze lock gates submitted to two different accidental loads. The case of an impact involving a vessel is first investigated. In this situation, the resistance of the struck gate is evaluated by assuming a local and a global deforming mode. The super-element method is used in the first case, while an equivalent beam model is simultaneously introduced to capture the overall bending motion of the structure. The second accidental load considered in this paper is the seismic action, for which an analytical method is presented to evaluate the total hydrodynamic pressure applied on a lock gate during an earthquake, due account being taken of the fluid-structure interaction. For each of these two actions, numerical validations are presented and the analytical results are compared to finite-element solutions.

The Effects of Jacquard Woven Fabric Constructional Parameters and Elastane Yarn on Bending Rigidity

In this research, the bending property of jacquard woven fabrics and the effects of weft density, weft yarn count, weave, and Lycra inclusion in weft yarn on this property were investigated. Viscose filament warp yarn and polyester and polyester/Lycra weft yarns were used for weaving fabrics, and 4/1 and 7/1 satin weaves with the same jacquard design were used as the ground weave. Experimental results show that the bending rigidities of the fabrics in the warp directions increase as the weft density increases and the weft yarn gets thicker. The bending rigidities of the fabrics woven with a 4/1 satin weave in the warp direction are higher compared to the bending rigidities of the fabrics woven with a 7/1 satin weave in the same direction. Similar to the bending rigidities in the warp direction, as the weft density increases and the weft yarn gets thicker, the bending rigidities of the fabrics in the weft directions increase. When the weft yarn includes Lycra, the bending rigidity values of the fabric decrease in the weft direction. Additionally, similar to the bending rigidity in the warp direction, the jacquard woven fabrics with a 4/1 satin weave have a higher bending rigidity in the weft direction compared to the jacquard woven fabrics with a 7/1 satin weave. It was observed that when the weft density increases, the overall bending rigidities of the fabrics increase. Despite fabrics woven with a polyester/Lycra weft yarn having a thicker weft yarn and heavier weight with the same weft density and weave compared to fabrics woven with a polyester weft yarn, the bending rigidity values in the weft direction have a lower overall fabric bending rigidity.