Road Drainage Infrastructure Diagnostics and Deficiency Indexing in ENSO-Vulnerable Andean Corridors: A STEM–PjBL Field Assessment

Reliability-Based Design and Quality Control of Bored Piles

Understanding and interpreting aircraft structural and engine failure modes at a material level is important from the standpoint of employing superior fracture‐resistant materials and predicting remaining useful life based on the micromechanics of materials. Failure modes can be understood by observing the fracture surface of a component from a low magnification to several orders of magnitude of magnification. It is also important to know the chemical composition of the material, primary, and secondary processing methods used to fabricate the product form. To predict the fracture modes, knowledge of operational environment and loads is required. Recently, there has been an increasing interest and need to design structural health monitoring systems to maintain systems based on the system condition. Instead of time‐based maintenance, the new paradigm is to perform condition‐based maintenance. Therefore, knowledge of material and structural failure modes is essential to incorporate this new approach. To perform the system health diagnosis, collaborative work between nondestructive evaluation (NDE) and structural health monitoring researchers is critical to build new health monitoring systems in the future. This article broadly discusses and summarizes failure modes of a few structural metallic alloys and polymer‐based composites used in aerospace structures.

Structural fire design, until recently, has only assumed uniform fires inside the compartment, and the assessment of structural failure has been often based on a critical temperature criterion. While this criterion, to some extent, may be able to indicate the temperature at which the structural element is near to failure, it is based on standard fire tests and, therefore, its validity is limited to individual members exposed to uniform temperatures. It is unclear how representative a critical temperature criterion is of structural failure in the case of multi-story structures, particularly in the case of non-uniform fires such as travelling fires. Therefore, the aim of this study is to assess the validity of the critical temperature criterion for structures exposed to non-uniform fires and compare it to uniform fires. A generic 10-storey steel framed building is modelled using the finite element software LS-DYNA. In total, 117 different scenarios are investigated to cover a wide range of conditions of interest for design of modern steel buildings, varying the fire exposure (travelling fires, Eurocode parametric fires, ISO-834 standard fire, and SFPE standard), floor where the fire is burning, beam section size, and applied fire protection to the beams. For the different fire exposures considered, the analysis predicts structural failure at different times, in different locations and floors, and different failure mechanisms. Moreover, it is shown that there is no single worst case fire scenario: different fires can lead to failure in different structural ways. The comparison of the various structural and thermal failure criteria (ultimate strain, utilization, mid-span deflection, and critical temperature) show that there is no consistency between them, revealing a far more complex problem than reported in the literature. Lastly, this work has illustrated that the critical temperature criterion does not predict accurately the structural failure in time, space or failure mode of steel structures subjected to both uniform and non-uniform fires. Structural failure can only be predicted by advanced structural analysis, and, therefore, heat transfer analysis alone is not sufficient for design. Nevertheless, it was shown that the use of the critical temperature leads to conservative results for simple steel structures. For the sake of comprehensive design, a range of different fire scenarios, including both uniform and non-uniform, should be part of the analysis such that all likely structural responses and failure modes can be considered.

There could be multi-failure modes in the course of working of the structure system including slender bar members. For example, strength failure, fatigue failure and buckling failure, especially sudden buckling failure would bring large disaster to structure. In this paper, according to Fatigue and Damage Mechanics theory, safe margin expression of the different failure mode of structure (static strength, fatigue and buckling) is given firstly, then by analyzing different failure mode of structural element under static and fatigue loads, and failure mode of the calculating element is confirmed by comparing the failure probability value of different failure mode. In the course of searching for significant failure paths, not only is failure mode that stiffness matrix of structure is zero considered, but also buckling failure mode of compressed residual structure is considered too, so that failure analysis is more reasonable. In the end, the reliability calculating method of the structural system is given, and the validity of the method proposed in this paper is explained combining an example.

On the influence of manufacturing parameters on buckling and modal properties of sandwich composite structures

The importance of the severe accident mitigation under beyond design-basis events (BDBEs) was realized to achieve the nuclear safety through the Fukushima accident. Failure mode estimation of essential components in nuclear facilities is necessary to take appropriate measures against the severe accident conditions. The failure mode of piping systems exposed to excessive seismic loading was found to be ratchet deformation followed by fatigue failure through many experimental tests in the past, whereas the failure of Test #37 of Pipe-fitting dynamic reliability program (PFDRP) conducted by EPRI was unexpected and its failure mechanism remains unclear, as it was often suspected to have been failed in plastic collapse. In the past research, the constant stress on the structure such as a dead-weight was revealed to significantly affect the failure mode and failure level of structures under seismic excitation. In this study, the constant stress components which can increase due to the ratchet deformation during a seismic excitation is focused and is analytically examined to clarify the effects on the failure mode of structures by using a cantilever structure with various dead-weight conditions and a constant cycles of sinusoidal waves which essentially represents the seismic loading with specific frequency ratios to establish the failure estimation of a structure exposed to seismic loading.

Dynamic response and failure characteristics of the fluid-filled concave multicell structure under combined blast and fragments loading

Research on determining solid structure critical load and failure mode

Traditional methods for structural damage evolution and failure mode analysis usually depend on specific failure path analysis, which is inefficient and time-consuming to implement for complex structures. In this paper, an efficient failure path-independent methodology for structural damage evolution and failure mode analysis of framed structures is proposed based on the elastic modulus reduction method. The element bearing ratio, uniformity of element bearing ratio and reference element bearing ratio are defined in terms of the homogeneous generalized yield function of spatial beam element, while a dynamic criterion is presented to identify the highly stressed elements. Subsequently, a self-adaptive strategy of elastic modulus adjustment is developed to reduce the elastic moduli of the highly stressed elements for simulation of structural damage evolution. Finally, the reduction rate of elastic moduli of the highly stressed elements is presented to determine the failed sections among the failure elements in the last iteration, based on which the potential failure mode is identified. The applicability, computational accuracy and efficiency of the proposed methodology are validated by comparing with the elasto-plastic methods through two numerical examples.

This article reports an experimental study carried out with the aim of quantifying performance and failure modes of sandwich structures when subjected to impulsive blast loading. In particular, performance enhancement with respect to solid panels of equal mass per unit area is assessed. Likewise, the optimal distribution of the mass per unit area in the design of sandwich structures is investigated by comparing the behavior of sandwich structures with various distributions of face sheets thickness. By employing a previously developed FSI experiment, the study confirmed that usage of sandwich structures is beneficial and that performance enhancements, in terms of maximum panel deflection, as high as 68% are possible. The study also confirms theoretical and computational analyses suggesting that use of soft cores maximizes the benefits. Another interesting aspect revealed by this work is that the level of enhancement is highly related to the applied normalized impulse. The same distribution of mass per unit area between face sheets resulted in different normalized maximum deflection. A better performance enhancement was achieved at lower impulses. Here again, failure modes and their sequence seem to be the directly related to this finding. The work here reported clearly reveals a number of important features in the study of lightweight structures and points out to the synergies between structure geometry, materials, manufacturing methods, and threat levels as manifested by the strength of the impulse. Further theoretical and computational studies accounting for experimentally observed failure modes and its interdependence with the fabrication methods is needed to achieve additional predictive capabilities.

In designing new type of structures, it is very difficult to evaluate the safety factors due to lack of previous design data and operational experiences. To solve the above mentioned problem, much attention is being focussed on rational reliability-based design approaches.This paper deals with Weight-Optimal Reliability-Based Design (WORBD) of stiffened plates subjected to structural reliability constraints taking into account of the effect of local buckling and interactive behavior between local and global buckling.Present method is compared with the existing optimal design method based only on safety factors. Numerical simulation reveals that the present method leads to lighter structure (4% reduction in weight compared to the existing optimal design) with the same reliability index. For larger structures (eg. ship structures) with more number of structural members and possible failure modes, the present WORBD procedure will be an efficient tool in designing cost-effective rationalized economic design.

In response to growing interest in lightweight, high-strength wood-based engineering materials, a lattice core sandwich structure made of plywood and birch dowels with improved relative density in its core was designed and fabricated. Flatwise and edgewise compressive experiments were performed to investigate the mechanical behavior of the sandwich structure. The effect of relative density on the mechanical properties and failure mode of the structure under flatwise compression was discussed. The theoretical and experimental flatwise compression test results showed good agreement. The results of the edgewise compressive tests of the sandwich structure indicated that face sheet wrinkling, crushing, and macro-shear buckling of the core were the main failure modes. The wood-based lattice sandwich structure has potential applications in the construction industry as beam and plate structures for buildings.

Super-elasticity and deformation mechanism of three-dimensional pillared graphene network structures

Built-up CFS column is a type of structure that can be classified as an industrialized building system. This column has been widely used in the construction industry. It has relatively lightweight, easy to fabricate and provide efficient installation, thus suitable for the construction with difficulty inaccessibility. However, the main issue that arises from the built-up CFS column is its bearing capacity. The ultimate strength and displacement of the built-up CFS column are prominently governed by its section properties such as size and thickness. Therefore, this study intends to investigate the effects of section properties on the structural behaviour and failure mode of built-up CFS columns. The built-up CFS column was modelled in the three-dimensional using WELSIM, taking into account the nonlinearities of geometry, material criterion and contact surface. It was found that the built-up CFS column attains ultimate strength of 53.33 kN to 210.6 kN and displacement around 1.33 mm to 2.98 mm. When the size and thickness of square hollow sections are increased, the ultimate strength increases simultaneously but the displacement shows a decrement trend. Under compression force, it was observed that the built-up CFS column suffers distortional and flexural buckling as well as connector and stiffener failures.

Transient fracturing of solder joints subjected to displacement-controlled impact loads