Energy-based Assessment Research Articles

Energy-Based Assessment of the Ultimate Limit State of a Physically Nonlinear Structure

The paper addresses issues of nonlinear analysis of load-bearing structural members. It highlights the main distinction from the traditional approach, which involves a two-step procedure where static and dynamic analyses are separated from the local reliability check of design sections. In contrast, the nonlinear analysis employs a single-step analysis and a global assessment of the structural behavior while simultaneously checking the performance of all sections. It is proposed to use the work done by external forces as a measure for determining the ultimate load. An incremental procedure is analyzed, through which the equilibrium state curve is constructed and this work is calculated. The paper highlights the issue of numerical instability in the computational process as it approaches the failure load. As a way to address this problem, it is suggested to consider a state of the structure as ultimate when it significantly loses its ability to resist the increasing load (loss of resistance). The paper proposes a method for finding design combinations of independent load cases, based on the energy approach, which offers sufficient applicability. It is noted that in the case of nonlinear (global) analysis, the selection of a design load combination should be based not on a local criterion but on a global one, which defines the composition of loads and actions constituting the design combination. The energy of deformation is suggested as such a criterion. The algorithm for searching for dangerous load combinations relies on a plausible hypothesis that the energy-based composition of load combinations leading the system to its ultimate state, due to the global nature of energy assessments, will be the same as in the case of linear analysis. This algorithm enables to solve the problem without resorting to an exhaustive evaluation of all possible load combinations.

A fundamental study on energy-based assessment of Shinkansen railway noise in Japan

This study examines the assessment of environmental noise standards for the Shinkansen in Japan, which predominantly relies on averaging the highest noise levels, specifically L_(A,Smax) obtained from actual measurements taken at key locations along the Shinkansen routes. In contrast, the international approach, based on Europe, typically involves energy-based evaluations that calculate noise exposure over time using estimated values. By investigating the correlation between L_(A,Smax) and energy-based noise levels (L_AE), including data from the latest Shinkansen model, the N700S, this research aims to explore the potential for adopting energy-based noise assessments in Japan, aligning with international methodologies. Additionally, it compares the relationship between measured L_AE and L_(A,Smax) with that of estimated L_(A,Smax) and measured L_(A,Smax). The study also examines the calculation equations by derivingL_(A,Smax) from L_AE and considers factors contributing to the increase in Root Mean Square Error (RMSE), such as differences in routes, distances from the track surface to the measurement points, vehicle types, and the influence of building clusters.

Energy-Based Assessment of Liquefaction Behavior of a Non-Plastic Silt Based on Cyclic Triaxial Tests

Earthquakes cause cyclic shear deformations in soil and build-up of excessive pore water pressure as a result of undrained loading, accompanied with rearrangement of soil particles and degradation in stiffness of the soil due to decrease in effective stresses. During loading, the onset of soil liquefaction is defined as a stress state in which the excess pore water pressure is equalized to the total stress. From this point of view, assessment of the pore water pressure development pattern under cyclic loading has been one of the most salient research topics in geotechnical and earthquake engineering. In this study, results of a series of cyclic triaxial tests on non-plastic silt specimens consolidated under 100 kPa effective isotropic consolidation pressure were used to question the modelling ability of pore pressure development models previously proposed for sands. Tests were performed on specimens of 6 different initial relative densities (Dr) ranging between 30-80% and 10 different cyclic stress ratios (CSR). The key parameters of pore water pressure development and shear deformation in the energy-based model used are relative density, cyclic stress ratio and number of cycles. The results revealed that, these energy-based models have a strong potential in evaluation of pore water pressure development pattern of non-plastic silts. Test results also show that the increase in relative density and decrease in CSR causes a ladderlike behavior among pore water pressure and cyclic shear strain, which is relevantly rendered by energy-based models.

Developing a novel energy-based approach for measuring mental workload

Minimal research has been conducted to develop non-invasive processes for quantifying and evaluating worker mental workload - a critical concern - at the task level in the construction industry. One reason for this gap in research is the complex and dynamic nature of the construction process, which makes construction work more complicated to measure and predict compared to work in other industries. This paper presents a novel approach and corresponding conceptual model to quantify and evaluate construction worker perception of mental workload at the task level using the energy concept. A conceptual process for assessing mental workload (MWL), i.e., the feeling of stress, pressure, and being overwhelmed due to the task nature, factors, conditions, and resources that accompany the performance of the task, was developed from extant research and interviews. The Delphi method was utilized to characterize the energy-based model and provide initial verification. The results from the literature review, expert insight, and four rounds of the Delphi survey revealed 14 constituents, 51 components, and one metric for each component to measure the level of MWL felt by a worker. These constituents, components, and metrics were used to develop a model for measuring construction worker MWL. This study contributes to knowledge by developing a novel non-invasive method for assessing potential task-level MWL using an energy-based model. The energy-based assessment model contributes to practice by providing a tool that could be used to measure the potential impact of construction tasks on workers perceived mental workload.

Energy-Based Assessment and Driving Behavior of ACC Systems and Humans Inside Platoons

Evidence in the literature shows that automated and human driving modes demonstrate different driving characteristics, i.e., headway policy, spacing policy, reaction time, comfortable acceleration, and others. These differences alter observed traffic dynamics and have an impact on energy consumption. This paper assesses the energy footprint of commercially implemented adaptive cruise control (ACC) systems and human drivers in car-following formation via different models using empirical observations on very similar driving cycles and/or routes. Most importantly, it initiates a critical discussion of the findings under the behavioral properties of each mode. Findings show that: ACC systems propagate an increasing energy consumption upstream, while human drivers do not; they succeed in maintaining a constant time-headway policy, operating very reliably; they develop a strong bond with their leader compared to their human counterparts; the two modes (humans and ACCs) are operating in different phase-space areas with room for improvement. Overall, findings show that ACC systems must be optimized to achieve a trade-off between functional requirements and eco-driving instructions.

Energy-Based Assessment of the Cyclic Behavior of Sand Stabilized with Colloidal Silica

Energy-Based Assessment of the Cyclic Behavior of Sand Stabilized with Colloidal Silica

Energy-based assessment of reinforced concrete walls with two outriggers

In this paper, different kinds of energy dissipation in reinforced concrete (RC) core–wall systems with two buckling-restrained braced outriggers, subjected to forward-directivity near-fault and ordinary far-fault earthquakes, have been compared. The level of the first outrigger was fixed at the top and the second outrigger was placed at different levels. In the non-linear model, two approaches for the RC core–wall were considered: the extended plastic hinge (EPH) approach and the four plastic hinges approach (4PH). In the 4PH approach, only four plastic hinges are allowed in the RC core–wall, one at the base, another adjacent to and beneath the top outrigger, and two others at the level's adjacent second outrigger. For the EPH approach, the plasticity can extend anywhere in the core–wall. Principally for the EPH approach, at the base of core–wall and adjacent to the top outrigger, as well as above and below the second outrigger level, more inelastic energy demands occur due to the large moment demand resulting from seismic load. On average for both EPH and 4PH approaches, the inelastic energy at the base from far-fault records is almost 1.5 times the corresponding value from near-fault records.

Energy-based assessment of cyclic liquefaction behavior of clean and silty sand under sustained initial stress conditions

In practical engineering, sand deposits containing some finer particles usually sustain an initial static shear stress. This study investigates the sustained initial stress effect on liquefaction response of saturated sand through conducting cyclic undrained triaxial tests. The obtained response of sand samples containing a small amount of silty fines is compared to that of clean sand under similar relative densities. The results exhibit that various stress conditions result in two response patterns named as cyclic mobility and residual deformation accumulation. It is shown that the addition of silty fines can either enhance or reduce the cyclic liquefaction resistance of sand, depending on the fines content, while the sustained initial stress plays a beneficial role in resisting cyclic failure for samples with or without the addition of fines under otherwise identical testing conditions. It is also found that the dissipated energy accumulated in both the silty and clean sand follows a power-law relationship to the generated residual pore pressure during cyclic loading. A unified relationship is further established between the liquefaction resistance and dissipated energy, which may be useful for developing an energy-based assessment of in-situ soils using strength data from laboratory experiments. • The liquefaction behavior of clean sand is compared to that of silty sand under similar relative densities. • The static shear stress is shown to play a beneficial role in resisting cyclic failure. • An energy-based relationship is proposed by relating the residual pore pressure to the normalized energy. • A unified correlation is established between the dissipated energy and cyclic resistance.

An Energy-Based Assessment of Expected Benefits for V2H Charging Systems through a Dedicated Dynamic Simulation and Optimization Tool

Electricity from renewable energy sources represents the most promising way to decarbonize energy systems. A grid connection of car Electricity Storage Systems (ESSs) represents an opportunity to tackle issues regarding electricity production non-programmability, only if sufficiently smart bi-directional Vehicle to Grid technologies (V2G) are widely implemented. Fully Bi-directional grid capabilities are still poor and must be increased, both physically and in terms of management and billing possibilities (in the so-called smart-grid paradigm). However, some V2G technologies may be already implemented in smaller individual contexts: so-called Vehicle to Home, V2H technologies. Starting from these considerations, within the frame of an Italian publicly funded research project, the authors categorized and described many possible application contexts and developed an open-source dynamic simulation (fully available under request for the scientific community) to identify most promising conditions. To this aim, they also synthetized and tested an effective energy optimization algorithm which will soon be implemented on a prototypal wireless V2H device, built by ENEA in cooperation with Cassino University, in Italy. The performances of the system were assessed evaluating electricity auto-consumption and home auto-feeding ratios. Simulations show that very relevant performances can be obtained, up to the values 69% for electricity auto-consumption and 82% of home auto-feeding.

Energy-Based Assessment of Liquefaction Resistance of Rooted Soil

AbstractPlant roots have been shown to improve the soil resistance to liquefaction upon cyclic loading. However, the effect of roots and their orientations on any changes in soil anisotropy and the...

New formulae for capacity energy-based assessment of liquefaction triggering

Liquefaction of loose saturated soil deposits is a hazardous type of ground failure occurring under earthquake excitations. Therefore, an accurate estimation of liquefaction potential is extremely important in geotechnical engineering. In the current study, a new model is proposed which estimates the level of strain energy needed for liquefaction initiation. A compiled database containing cyclic tests gathered from previously published works was used to develop new models to predict liquefaction potential. M5′ algorithm was used to find the best correlation between parameters. It was shown that not only the derived formulas are acceptably accurate but also they feature a very simple structure in comparison with available formulas in the literature. The proposed equations are accurate, physically sound and uncomplicated. Furthermore, safety factors were given for different levels of risk, which can be useful for engineering practice. In addition, the influence of different predictors on the liquefaction potential was evaluated and also the significance of input variables was assessed via sensitivity analysis. Finally, a new model was introduced for preliminary estimation of liquefaction potential.

Energy-based assessment of brittle fracture in VO-notched polymer specimens under combined compression-shear loading conditions

This research presents some experimental, numerical, and theoretical results on brittle fracture of disk-type test specimens weakened by V-notches with end-holes under mixed mode I/II loading with negative mode I contributions. First, 54 fracture tests are conducted on VO-notched Brazilian disk specimens made of the general-purpose polystyrene under mixed mode I/II loading with negative mode I contributions. Then, two energy-based brittle fracture criteria, namely the averaged strain energy density and averaged strain energy density based on the equivalent factor concept are proposed to predict the experimentally obtained fracture loads of the tested general-purpose polystyrene specimens. Additionally, the fracture initiation angles of the tested VO-notched Brazilian disk specimens are predicted by using averaged strain energy density criterion. The finite element analyses, as well as the experimental observations, show that although brittle fracture in the specimens under mixed mode I/II loading takes place from the applied load side of the notch border by local tensile stresses, the notch bisector line and the other sides of the notch border sustain compressive stresses. In fact, this phenomenon states the concept of mixed mode I/II loading with negative mode I contributions. Finally, it is shown that good agreement exists between the experimental results and the theoretical predictions of the two energy-based fracture criteria.

Effect of surgical defect localization on ultimate load-bearing capacity of human femur: finite-element energy-based assessment

Abstract Elastic properties and toughness of cortical bone tissue are non-uniformly distributed over its anatomical quadrants. This can have an effect on the bone’s load-bearing capacity after a surgical resection associated with a removal of tumor-like lesions followed by formation of a sectorial bone defect. The purpose of this work is to evaluate the ultimate load-bearing capacity of the femur with the post-resection defect, taking into account various types of distributions of elastic properties and toughness in different quadrants of a cross section of the bone. The elasticity modulus of the bone tissue in the longitudinal direction of the femur is determined based on a nanoindentation test of a human femoral bone specimen. Based on numerical simulations, it is established that the most dangerous – with regard to the occurrence of a pathological fracture – is the localization of the post-resection defect, when a remaining fragment of the bone tissue is located in the anterior quadrant. In this case, the value of the ultimate load is significantly lower compared to that for other variants of localization of the post-resection defect. A non-uniform distribution of fracture toughness in the cross-section of the femur has a greater effect on the magnitude of the ultimate load than non-uniformity of elastic properties. This should be taken into account when evaluating the ultimate load, since averaging the toughness over the bone’s cross-section can result in overestimations. Neglecting non-uniformity of toughness can lead to an incorrect assessment of the ultimate load and to wrong recommendations for postoperative rehabilitation of a patient.

Review of Out-of-Plane Seismic Assessment Techniques Applied To Existing Masonry Buildings

ABSTRACTObservations after strong earthquakes show that out-of-plane failure of unreinforced masonry elements probably constitutes the most serious life-safety hazard for this type of construction. Existing unreinforced masonry buildings tend to be more vulnerable than new buildings, not only because they have been designed to little or no seismic loading requirements, but also because connections among load-bearing walls and with horizontal structures are not always adequate. Consequently, several types of mechanisms can be activated due to separation from the rest of the construction. Even when connections are effective, out-of-plane failure can be induced by excessive vertical and/or horizontal slenderness of walls (length/thickness ratio). The awareness of such vulnerability has encouraged research in the field, which is summarized in this article. An outline of past research on force-based and displacement-based assessment is given and their translation into international codes is summarized. Strong and weak points of codified assessment procedures are presented through a comparison with parametric nonlinear dynamic analyses of three recurring out-of-plane mechanisms. The assessment strategies are marked by substantial scatter, which can be reduced through an energy-based assessment.

Non-invasive, energy-based assessment of patient-specific material properties of arterial tissue.

The mechanical properties of human biological tissue vary greatly. The determination of arterial material properties should be based on experimental data, i.e. diameter, length, intramural pressure, axial force and stress-free geometry. Currently, clinical data provide only non-invasively measured pressure-diameter data for superficial arteries (e.g. common carotid and femoral artery). The lack of information forces us to take into account certain assumptions regarding the in situ configuration to estimate material properties in vivo. This paper proposes a new, non-invasive, energy-based approach for arterial material property estimation. This approach is compared with an approach proposed in the literature. For this purpose, a simplified finite element model of an artery was used as a mock experimental situation. This method enables exact knowledge of the actual material properties, thereby allowing a quantitative evaluation of material property estimation approaches. The results show that imposing conditions on strain energy can provide a good estimation of the material properties from the non-invasively measured pressure and diameter data.

An Energy-Based Assessment on Dynamic Amplification Factor for Linear Static Analysis in Progressive Collapse Design of Ductile RC Frame Structures

Progressive collapse is a mechanical process that exhibits nonlinear and dynamic characteristics. The nonlinear dynamic effect on the progressive collapse resistance demand can be accurately evaluated by the nonlinear dynamic (ND) method. In engineering practice, however, the simplified and easy-to-use linear static (LS) method is often adopted. That is accomplished by using a dynamic amplification factor (DAF) to correct the LS resistance demand to approximate the true ND resistance demand. In this paper, the analytical expression of the DAF is established based on the energy conservation principle. The collapse-resisting substructure is firstly simplified as a single-degree-of-freedom (SDOF) equivalent. Then the energy conservation equation and the static balance equation of the SDOF equivalent are established to obtain the ND and LS demands. Finally, the DAF is obtained by dividing the ND demand by the LS demand. The DAF is validated through a series of the numerical examples including a SDOF system, a 3-storey planar frame and an 8-storey 3-D RC frame model structures.

RETRACTED: Effects of fly ash and TiO2 nanoparticles on rheological, mechanical, microstructural and thermal properties of high strength self compacting concrete

Abstract In the present study, strength enhancement and durability-related characteristics along with rheological, thermal and microstructural properties of high strength self compacting concrete (HSSCC) containing nano TiO 2 and industrial waste ash namely as fly ash (FA) have been investigated. With this respect, Portland cement was replaced by up to 15 wt% waste ash and up to 5 wt% TiO 2 nanoparticles and the properties of HSSCC specimens were measured. It was found that with the aim of energy saving and recycling of waste materials, addition of FA as a natural pozzolan can improve the rheological, mechanical and durability properties of concrete at higher ages. TiO 2 nanoparticles as a partial replacement of cement up to 4 wt% could accelerate C–S–H gel formation as a result of increased crystalline Ca(OH) 2 amount at the early age of hydration and hence improve the microstructure of concrete leading to improved durability-related properties and strength enhancement of the concrete. Several empirical relationships for predicting flexural and split tensile strength of concrete based on compressive strength for HSSCC containing FA and nano TiO 2 at different ages have been obtained. Finally, an energy-based assessment of strength enhancement of nano-containing concrete has been presented.

Energy-based assessment of ductile tearing in a thin sheet aluminium alloy

This paper deals with several issues in ductile tearing assessment. One of them is the contrasting of energy-based parameters, namely, the Essential Work of Fracture (EWF) [B. Cotterell, J.K. Reddel, The essential work of plane stress ductile fracture, International Journal of Fracture 13 (1977) 267–277], wet, and the Energy Dissipation Rate (EDR) [C.E. Turner, A re-assessment of ductile tearing resistance (Part I and II). In: Fracture Behaviour and Design of Materials and Structures 1990; Proc. ECF 8; 2: 933–949 and 951–968], R. We intend to answer the following questions: (i) Is there a reasonable correlation between wet and R? (ii) Is there any correlation between their constituents? and, finally, (iii) Are the energy- and displacement-based characterizations of slant crack growth under uncontained yielding consistent with each other?