Failure mechanism of single-layer saddle-curve reticulated shells subjected to erathquakes

p. 345-354In order to have a good understanding of the failure mechanism of single-layer saddle-curve reticulated shells under earthquake motion, dynamic failure mode of single-layer saddlecurve reticulated shells under earthquake motion is discussed with accumulation of material damage introduced to analyze the failure of these shells under dynamic actions. Based on the comprehension of the mechanical behaviours and structural full-range characteristic responses in an example, dynamic strength failure due to excessive development of plastic deformation is a mainly failure mode for single-layer saddle-curve reticulated shells subjected to earthquakes. Then, a method is proposed for determination of failure state. The relationships between structural responses under ultimate load and different structural parameters are investigated through simulation.Zhi, X.; Fan, F.; Shen, S.; Fan, Q. (2009). Failure mechanism of single-layer saddle-curve reticulated shells subjected to erathquakes. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/652

Review on building life cycle assessment from the perspective of structural design

The resource-related, environmental and ecological problems raised by building construction activities have drawn a wide range of concerns among researches, especially in China. Those problems have become prominent. In last decade, the building life cycle emissions and energy efficiency have been researched widely. Most of the studies focus on the assessment models and emission analysis based on the available project data and statistical data. Very few of them study the emissions from the view of structure design, which can reduce the building emission at source. This review summarizes and examines different models proposed for the building life cycle assessment, focusing on the model scopes, assumptions, and their applications from the view of structure design. A great attention is given to the data used in the current studies. Finally, a variety of future research directions of building life cycle assessment are discussed

Modeling of the Snowdrift in Cold Regions: Introduction and Evaluation of a New Approach

Unbalanced, or non-uniform, snow loads caused by snow drifting or sliding in cold regions with heavy snowfalls, can be a serious problem for the building industry. However, the methods for predicting snow distribution still need to be improved. Field observation is the most direct and reliable method to study snow distribution, but because the natural environment is uncontrollable and varies dramatically, sometimes conclusions may be confused under the influence of the many variables in the investigation. This paper proposes a snowing experiment approach using an outdoor snow–wind combined experiment facility for the study of snow distribution. The facility can produce a stable and controllable wind field and snowfall environment. Experiments which focused on snowdrift around a building were conducted during the winter to make an evaluation of the repeatability and reliability of the new approach. Finally, from the analysis of results, it was demonstrated that the experimental facility was stable and that the similarity criterion adopted for the snowing pattern was reliable. Especially, the minimum value of the friction speed ratio was suggested to ensure the test accuracy

Wrinkling simulation of membrane structure

p. 2083-2092Due to a high ratio of load carrying capacity to self weight, membrane is widely used in various applications such as gossamer space structures One major design issue that is inherent to membrane structures is the formation of wrinkling patterns. In this paper, a geometrically nonlinear, updated Lagrangian shell formulation is employed using the ABAQUS finite element code to simulate the formation of wrinkled deformations in thinfilm membranes. Two effective modeling strategies are introduced to facilitate convergent solutions of wrinkled equilibrium states. Several numerical studies are carried out, and the results are compared with recent experimental data. Good agreement is observed between the numerical simulations and experimental data.Sun, X.; San, B.; Wu, Y.; Shen, S. (2010). Wrinkling simulation of membrane structure. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/726

Strength and Damping Properties of Cementitious Composites Incorporating Original and Alkali Treated Flax Fibers

This experimental investigation focused on the mechanical and damping properties of raw and alkali treated flax fibers reinforced cementitious composites. The objective of this study was to research the influence of flax fiber for the damping properties of cementitious composites. The mechanical strengths were obtained using compressive and flexural tests and damping properties were measured using a dynamic mechanical analysis. Structural modifications to the treated flax fibers were analyzed using scanning electronic microscopy and mercury intrusion porosimetry. Results showed that cement compressive strength was decreased, and flexural strength was increased by the addition of untreated flax fibers. Alkali treatment improved the mechanical strength of flax reinforced cement. The addition of flax fibers improved cement damping properties, and the damping effect of untreated flax fibers was greater than that of alkali treated fibers. The loss tangent of the cementitious composites reinforced with raw and alkali treated flax fibers at an amount of 1 wt % of cement was improved by 45.83% and 37.5% at 20 Hz, respectively. The damping properties of flax fiber was attributed to friction between elementary fibers and between adjacent fiber cell walls and slipping between the fiber and matrix. Callouses, pectin, and lignocellulose in untreated flax fiber contributed to damping and their removal by alkali treatment was the main reason why untreated flax fibers had a greater damping effect as compared to alkali-modified flax fibers

Failure modes for reticulated domes under diverse impact

p. 1813-1822FE models of both the single-layer Kiewitt-8 reticulated domes with a span of 60m and the cylindrical impactor were developed incorporating ANSYS/LS-DYNA. Afterward, fourteen groups impact are simulated by changing the impact position or impacted angle on reticulated dome, and impact velocity and mass of impactor are changed for each group impact. On the basis of large numbers of numerical simulations, characteristics of dynamic response for reticulated dome under impact are shown. And four failure modes (Members slightly damaged, Local collapse of dome, Global collapse of dome, Members shear failed) are presented for single-layer Kiewitt-8 reticulated dome under diverse impact. The distributing of failure modes for the fourteen types impact are different from each other, and the adverse position and angle are summrized.Fan, F.; Wang, D.; Zhi, X.; Tan, S.; Shen, S. (2009). Failure modes for reticulated domes under diverse impact. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/681

Pre-Operative chemotherapy response assessed by contrast-enhanced MRI can predict the prognosis of Enneking surgical margins in patients with osteosarcoma

The method used to evaluate the response of osteosarcoma to preoperative chemotherapy before specimen resection is still unclear. The purpose of this study was to identify factors that contribute to overall survival (OS) and to discuss their roles in making a decision regarding Enneking surgical margins. Patients (109) with pathologically confirmed Enneking stage IIB osteosarcoma were retrospectively analyzed. Univariate and multivariate survival analyses were performed. Patient characteristics and chemotherapy-induced contrast-enhanced MRI changes were considered as potential factors. Changes in the tumor volume and the relative necrosis ratio measured by MRI were independent risk factors predicting the OS of patients who underwent limb-salvage surgery. For those in whom the tumor volume had decreased (VolRati