Simplified Analytical Procedure Research Articles

SSI‐induced seismic earth pressures on an integral abutment bridge model: Experimental measurements versus numerical simulations and code provisions

AbstractIntegral abutment bridges (IABs) generate strong soil–structure interaction (SSI) effects due to their high structural stiffness and transmission of inertial and thermal loads generated at the deck directly to the abutments. Despite an increasing number of experimental and numerical studies available in the literature, there is a lack of consolidated methodologies to model dynamic SSI phenomena for IABs, particularly in seismic regions where uncertainties associated with the induced ground motions render the problem harder to tackle. This study proposes an advanced strategy to model the seismic response of IABs, accounting for dynamic interaction between the structure, the abutment and the foundation, including piles and earth retaining walls. To this end, detailed finite‐element studies were carried out employing OpenSees to simulate a recent experimental campaign on a scaled IAB model in a soil container (SERENA) carried out at EQUALS Lab, University of Bristol, in the framework of SERA/H2020 project. An extensive dataset in terms of recorded accelerations, displacements, strains and settlements are available from these tests, including earth pressures which are back‐calculated from bending strain measurements. The objectives of this paper are threefold: firstly, the model parameters are explored and assessed critically by comparing the results from the numerical simulations against the experimental data; secondly, once the model is deemed sufficiently representative of the experiments, earth pressures are obtained numerically, as these are not directly measured in the tests; thirdly, the estimated static and dynamic earth pressures on the abutment wall are compared with the predictions of two simplified analytical procedures currently under consideration for inclusion in the new Eurocode 8. The results indicate that records and predictions match well for frequencies of up to 40 Hz at model scale (about 8 Hz in prototype scale) and confirm that the proposed modelling strategy can be used in practical applications. The quasi‐elastic model proposed in this study is shown to provide dependable predictions for cases involving moderate strains in real‐life applications.

Effect of facing stiffness on reinforced soil walls under surcharge loading–unloading

This paper investigates the impact of facing stiffness on the performance of geosynthetic-reinforced soil (GRS) walls under surcharge loading–unloading. Data from two instrumented physical model tests are utilised considering two different facing stiffness (block and wrapped). After the end of construction, the physical models were loaded and unloaded, step by step. They were comprehensively instrumented to monitor the load mobilised along with the reinforcements, horizontal toe load, lateral facing displacement, vertical displacement at the top of the walls and horizontal stress behind the block faces. In addition, a simplified analytical procedure is proposed in order to determine the maximum reinforcement load under surcharge unloading. The results show that the toe restraint at the base of the block-faced wall highly controls the performance of GRS wall with structural facing. When there is no toe resistance, irrespective of the facing type, the walls present, in general, similar performance under surcharge loading and unloading. Furthermore, during surcharge unloading, the reinforcement load near the face may be less affected in the wrapped-face wall compared with the block-faced wall. Moreover, the maximum reinforcement loads during surcharge unloading were fairly captured using the proposed procedure.

Mycobacterium detection method combining filtration, immunomagnetic separation, and electrochemical readout in a portable biosensing device

This study addresses a straightforward and highly sensitive approach for detecting Mycobacterium fortuitum. The method involves a combination of filtration and direct immunomagnetic separation to isolate the bacteria retained on filters for further electrochemical magneto immunosensing in a handheld device. Unlike conventional methods involving pre-enrichment by culturing, this approach employs a simplified preconcentration technique, which includes filtration of large water samples, up to 100 mL, followed by a one-step process of immunomagnetic separation and labeling. After a 60-min, during which the filter with the retained bacteria and all the reagents (including modified magnetic particles and enzymatic conjugates) are incubated, the resulting product is directly drop into a cartridge, capable of performing magnetic actuation and washing. The electrochemical readout is carried out on a portable battery-operated device within 30 seconds. Remarkably, the immunosensor demonstrates an outstanding limit of detection of 5 CFU mL−1 in hemodialysis water processing 100 mL of sample. This achievement is remarkable considering the short and simplified analytical procedure, compared to the traditional isolation and culturing of mycobacteria, which typically takes 2 weeks.

SPH AND ANALYTICAL MODELING OF AN URBAN FLOATING STRUCTURE FOR COASTAL EXPANSION

The development of large-scale floating structures is recognized by the American Society of Civil Engineers as a critical step towards resilient coastal cities for climate change adaptation (ASCE, 2019). Yet, a lack of design guidelines acts to limit their development at the community scale. In response, we demonstrate and validate the applicability of a simplified analytical procedure against numerical solutions to elucidate the dynamics of a freely-floating pontoon-building system. This effectively presents a pathway towards the evaluation of structural requirements for the realization of floating cities as a sustainable alternative to traditional land reclamation.

Simplified analytical procedure to calculate the impact behaviour of steel parking-structure columns

The steel supporting frame of automatic mechanical garages is called a parking structure. Presently, for these novel structures, the design codes are without giving detailed guidelines to predict the response of their impacted column. Thus, this paper presents a simplified analytical procedure to calculate the impact behaviour of the column. The proposed method is based on the co-rotational rigid body model and follows the energy-balance principle. Compared with the previous analytical method, it specially targets the parking-structure column and can be used to conveniently and quickly calculate the column transverse displacement with considering the effects of the surrounding structural members and axial loads on the column. The research covers the situation where the column is subjected to the impacts at a low velocity, critical velocity, and overcritical velocity. Primarily, an approach is developed to simplify the overall parking structures. On that basis, the calculation formula for the critical impact velocity, i.e. the velocity that results in the formation of plastic hinges in the column, is derived. To predict the behaviour of the column under the impact beyond the critical impact velocity, the simplified analytical procedure is provided and then its accuracy is examined by validated numerical models. Eventually, according to the procedure, some suggestions are given to improve the design of the column after parametric analyses. It is recommended that control the axial-load levels of the column, particularly the column with a small section area, as well as set stiffeners on the column within the height of 1000 – 1500 mm.

Simplified design procedures for the structural analysis of reinforced concrete columns in fire

Simple analytical procedures are described to predict the structural behavior (axial displacements and failure) of reinforced concrete (RC) columns exposed to fire. The analyses assume a concentric load (no initial eccentricity) or an equivalent axial load to take into account first and second order effects. The main objective is to provide reliable and straightforward tools for a preliminary assessment of the structural integrity of RC columns. The procedures compute the total displacements and the failure (time and type) of RC columns with different concrete strengths (normal to ultra-high performance), shapes, fire incidences, load levels and initial eccentricities. The results of 24 experimental tests from different authors are predicted and compared with the analytical solution. The displacements are estimated by the introduction of EN 1992-1-2 (2004) stress–strain curves and a simplified bilinear constitutive law that takes into account the Load Induced Thermal Strain (LITS) as a reciprocal to the modulus of elasticity. In general, a good agreement with the experimental time vs. displacement curves was obtained. Failure is predicted with the adoption of the nominal stiffness method (EN 1992-1-2, 2004) to take into account the second order effects. Sectional analyses (axial-bending equilibrium) and simplified analytical procedures assuming an equivalent axial load replacing the axial-bending force (force equilibrium) are carried out. The results of both analyses were very close, indicating the reliability of the simplified procedure. The prediction of the fire resistance time demonstrated a good approximation, on the safe side, with the experimental data. The results are compared with the EN 1992-1-2 (2004) prescriptive formula.

Simplified Lateral Torsional Buckling (LTB) Analysis of Glass Fins with Continuous Lateral Restraints at the Tensioned Edge

Within multiple design challenges, the lateral torsional buckling (LTB) analysis and stability check of structural glass members is a well-known issue for design. Typical examples can be found not only in glass slabs with slender bracing members but also in facades and walls, where glass fins are used to brace the vertical panels against input pressures. Design loads such as wind suction give place to possible LTB of fins with LR at the tensioned edge and thus require dedicated tools. In the present investigation, the LTB analysis of structural glass fins that are intended to act as bracers for facade panels and restrained via continuous, flexible joints acting as lateral restraints (LRs) is addressed. Geometrically simplified but refined numerical models developed in Abaqus are used to perform a wide parametric study and validate the proposed analytical formulations. Special care is spent for the prediction of the elastic critical buckling moment with LRs, given that it represents the first fundamental parameter for buckling design. However, the LR stiffness and resistance on the one side and the geometrical/mechanical features of the LR glass members on the other side are mutually affected in the final LTB prediction. In the case of laminated glass (LG) members composed of two or more glass panels, moreover, further design challenges arise from the bonding level of the constituent layers. A simplified but rational analytical procedure is thus presented in this paper to support the development of a conservative and standardized LTB stability check for glass fins with LR at the tensioned edge.

Bearing capacity-relative density behavior of circular footings resting on geocell-reinforced sand

Geocell reinforcement (GR) improves load-deformation behavior of shallow foundations. A series of instrumented large-scale plate load tests was performed to ascertain such improvements and to correlate that to the relative density (Dr ) of geocell-reinforced sand (GRS). Variable effects on stiffness, bearing capacity (BC), load dispersion and strain-stress behaviors are discussed. The extensive tests made it possible to arrive at a simplified analytical procedure for predicting the BC of circular footings on GRS, taking into account probable shear failure mechanisms and monitored GR deformation. These results allowed the validation and generalization of the procedure reduced from an equivalent-layer BC model considering ‘confinement’ and ‘stress dispersion’ effects on the failure mechanism. Load dispersion angle and strains increase with increasing the sand Dr resulted in significant stress reduction below the GR. This was found most beneficial for the higher densities ranges. The proposed analytical approach can confidently be used for practical design purposes.

Bioaccumulation of Mercury in Marine Algae from Dakar Coast (Senegal) and Galician Rias (Spain)

Algae samples from Dakar coast (Senegal) and Galician Rias (Spain) were analyzed by cold vapor atomic absorption spectrometry (CV-AAS) to assess the bioaccumulation of mercury in the two aquatic systems. In this work, the contents of inorganic mercury and total mercury were determined. Simplified analytical procedures (microwave digestion and ultrasonic assisted extraction) were used for sample preparation. A reference material (BCR-60) was used to validate the analytical procedures used for sample preparation. The results of the analysis show that the total mercury contents found in algae samples from the Galician Rias are relatively similar to those found in algae samples from the Dakar coast. However, the inorganic mercury content of the algae from Pontevedra Ria was considerably higher than that found in the algae samples from Vigo Ria. The distribution was observed for inorganic mercury and total mercury, indicating that inorganic mercury is the major mercury species that bioaccumulates in marine algae. The inorganic mercury contents were always approximately equal to those of total mercury in the algae samples and a satisfactory correlation (p <0.0001; r = 0.9997) was obtained between them. Finally, the ANOVA analysis indicates that no significant difference (F = 0.165; p = 0.809) was found between the algae of the two aquatic systems (Dakar coast and Galician Rias).

An integrated performance‐based design framework for building‐foundation systems

AbstractThis paper presents a framework for the inclusion of transient and residual foundation deformations within performance‐based seismic design of buildings. A refinement of existing displacement‐based design procedures is proposed that reduces iteration when obtaining the expected peak foundation rotation. Empirical equations are developed based on numerical time‐history analyses that provide an estimation of foundation residual deformations based on the foundation peak rotation. Additional complexities due to deformation within the foundation are discussed regarding how they influence the design and building performance. The design framework is complemented by a simplified analytical design procedure (i.e., hand calculations) to design building‐foundation systems. A design example is given for a six‐storey concrete wall building, which is analyzed by time‐history analysis to demonstrate the application and accuracy of the design procedure.

Total Mercury and Methylmercury Distribution in Paguellus bellottii Fish from Soumbedioune Beach, Senegal

Paguellus bellottii fish proceeding from Soumbedioune beach (Senegal) were analyzed to evaluate their contents of total mercury and methylmercury. Simplified analytical procedures (microwave digestion and ultrasonic assisted extraction) were used for sample preparation. The total mercury content in fish varied between 0.0626-0.3542 µg/g, dry weight. The ANOVA analysis allows to conclude that significant differences (p &lt;0.05) were not found between Paguellus bellottii fish from Soumbedioune beach. However, the mercury levels obtained were always lower than the European legislation limits for fish. The ratio methylmercury/total mercury varied between 42.3-42.8 % in fish tissues. A satisfactory correlation (p&lt;0.0001; r = 1) was found between total mercury and methylmercury results.

Static force-based seismic analysis of reinforced concrete frames having weaker beam-column joints

Shake table tests were conducted on three 1:3 reduced scale two-story RC frames having weaker beam-column joints. The models were subjected to multi-levels input acceleration time histories to understand the seismic behaviour of test models. The models incurred severe damages in beam-column joint panels, forming shear hinging in joint panels, and were found in the incipient collapse state under input excitation below the design level excitation. Elastic hypothetical structures were considered having fundamental frequency that of test structures, which were subjected to actually recorded input excitation, in order to assess the seismic demands (base shear force and lateral roof displacement) using simplified analytical static procedure. The analytically predicted demands were correlated with the measured inelastic response, in order to calculate seismic response parameters (force reduction factor R and displacement modification factors Cd ). On average, R = 2.0 and Cd = 1.86 were obtained for the considered structures. The derived seismic response parameters can be employed in the analytical static force-based procedure for the seismic vulnerability assessment of RC frame structures having weaker beam-column joints. Example study is presented for the vulnerability assessment of considered structure using the proposed analytical static force procedure and the derived seismic response parameters.

Dissipation in sheathing-to-framing connections of light-frame timber shear walls under seismic loads

The present study is concerned with the seismic analysis and design of light-frame timber shear walls, with focus on the energy dissipation ensured by sheathing-to-framing connections under in-plane lateral loads. In this perspective, a suitable parametric finite element model for light-frame timber shear walls is first developed using the software OpenSees. By means of such model, the equivalent viscous damping of the wall is assessed numerically, together with the damping factor adopted within the capacity spectrum method. Furthermore, the optimal layouts of slender (1.2 m × 2.4 m/3.94 ft × 7.88 ft) and squat (2.4 m × 2.4 m/7.88 ft × 7.88 ft) light-frame timber shear walls are found by solving a multi-objective optimization problem in which racking capacity and total material cost are optimized simultaneously (this task is accomplished via simple enumeration because of the low cardinality of the design variables set). So doing, it is shown that the total material cost of the optimal (non-dominated) wall configurations has a strong influence on the racking capacity whereas it does not affect the equivalent viscous damping ratio, which remains almost constant. A novel simplified analytical procedure for predicting the capacity curve of light-frame timber shear walls is finally proposed.

Proposition of a simplified analytical design procedure for lattice girder slabs with shuttering in cold-formed steel lipped channel section

ABSTRACT This paper presents an analytical procedure to determine the resistance of a new composite ribbed lattice slab system, composed by a lipped channel cold-formed steel (CFS) profile in minor bending fastened to a lattice girder by plastic connectors, as well as light filling elements and additional rebar. Motivated by the lack of standardized procedures for such system, this paper combines slab design prescriptions to create a computational tool that estimates load capacity and required propping during construction, serving as a basis for a design catalogue. Finally, a strong limitation of unpropped construction due to the low performance of the cold-formed profile under minor axis bending was observed, being the system able to reach spans up to 1.5 m between props in general.

Sulfur heat transfer behavior in vertically-oriented and nonuniformly‑heated isochoric thermal energy storage systems

Elemental sulfur thermal energy storage (SulfurTES) is a promising low-cost solution for many medium to high temperature (300–1200 °C) TES applications. Demonstrations of SulfurTES have shown that the heat transfer behavior of sulfur in isochoric tubes is critical to system thermal performance. Previous studies have elucidated and quantified the sulfur heat transfer rate for idealized uniform charge and discharge; however, nonuniform conditions are more likely to be encountered in practice and need to be understood. This paper uses experimental and computational efforts to investigate sulfur heat transfer as well as exergy and energy performance in vertically-oriented tubes for two nonuniform thermal charge scenarios: top-heating and bottom-heating. In comparison with uniform thermal charge, the top-heating causes significant thermal stratification of sulfur that helps the SulfurTES system achieve superior exergetic performance. In contrast, the bottom-heating causes rapid mixing between hot and cold sulfur resulting in high charge rates. Both nonuniform charge strategies could be utilized during the operation of the SulfurTES system to improve system performance as well as provide operational flexibility. Using the computational results, this article originally develops two simplified analytical procedures to estimate the energy and exergy performance of sulfur in tubes of different sizes under top- and bottom-heating. The current study provides significant qualitative and quantitative heat transfer descriptions and design bases for SulfurTES systems and encourages further investigations into the complicated thermal performance for other thermal storage applications.

A SIMPLIFIED ANALYTICAL PROCEDURE FOR SEISMIC ANALYSIS OF TIMBER LIGHT-FRAME SHEAR WALLS

The seismic performance of timber light-frame shear walls is investigated in this paper with a focus on energy dissipation and ductility ensured by sheathing-to-framing connections. An original parametric finite element model has been developed in order to perform sensitivity analyses. The model considers the design variables affecting the racking load-carrying capacity of the wall. These variables include aspect ratio (height-to-width ratio), fastener spacing, number of vertical studs and framing elements cross-section size. A failure criterion has been defined based on the observation of both the global behaviour of the wall and local behaviour of fasteners in order to identify the ultimate displacement of the wall. The equivalent viscous damping has been numerically assessed by estimating the damping factor which is in use in the capacity spectrum method. Finally, an in-depth analysis of the results obtained from the sensitivity analyses led to the development of a simplified analytical procedure which is able to predict the capacity curve of a timber light-frame shear wall.

A Simplified Analytical Method for Stabilizing Micropile Groups in Slope Engineering

Stabilizing micropile groups is a light retaining structure constructed quickly and safely for slope reinforcement in practice. To carry out engineering design of any structure, a simplified analytical procedure for a micropile group with consideration of stability of the piled slope is presented. According to the upper bound theorem of kinematical limit analysis, an analytical method is proposed to evaluate the net thrust force on a micropile group with 3 × 3 layout of piles and the slip surface of the piled slope for a specified factor of safety. Then, internal forces of the micropile group can be computed using plane rigid frame model for the part of the structure above the slip surface under the net thrust force and beam-on-elastic-foundation model for the rest part. A laboratory model test and corresponding 3D-numerical simulation are conducted to verify the proposed method. Moreover, analysis of a practical slope shows that flexural rigidity of a micropile and micropile numbers of a group have a great effect on internal forces of micropiles. In particular, the internal forces are relatively sensitive to pile numbers in a group. However, micropile length and spacing in plane in a group have little effect on the internal forces, which is rather different from traditional stabilizing piles with a large cross section.

Multivariate optimization and validation of a procedure to direct determine acetonitrile and ethanol in radiopharmaceuticals by GC-FID

A fast and simplified analytical procedure was developed and validated for the direct determination of organic solvents (acetonitrile and ethanol) in radiopharmaceuticals samples ([18F]FMISO, [18F]FES and [18F]FLT) by gas chromatography coupled with flame ionization detection (GC-FID). Optimization studies were performed with the aid of two-level full factorial design. The optimum conditions were located using Derringer's desirability function. Procedure validation assured the compliance of the assay to Brazilian regulatory agencies standards (ANVISA and INMETRO). Values for LOD and LOQ were commensurate with the level at which the impurities must be controlled. Good linearity was achieved (R ≥ 0.990) for acetonitrile and ethanol concentrations ranging from 0.003 to 0.09% (w/v) and 2.1 to 11.0% (v/v), respectively. Accuracy and precision assessments were performed using samples fortified with standards (spiked samples). The developed procedure proved to be selective, sensitive, accurate (95.9–117.8% of nominal values) and precise (RSD ≤ 9.7%). The validated procedure was successfully used to assess organic solvents levels in a Brazilian radiopharmaceuticals samples manufactured by Radiopharmaceutical Research and Production Unit of Nuclear Technology Development Center (CDTN), in Belo Horizonte (Brazil). The analytes could be well resolved in 1.5 min and accurately determined in three different types of radiopharmaceuticals. This procedure is applicable to samples even with high ethanol content up to 11% (v/v). Other advantages include no sample preparation, short chromatographic separation time and minimum manual operation. As results, the proposed procedure can be useful in the routine analysis for the determination of acetonitrile and ethanol in radiopharmaceutical samples.

A simplified non-linear structural analysis of reinforced concrete frames with masonry infill subjected to seismic loading

Structural performance of both new and existing building structures under seismic actions can be assessed with a wide range of nonlinear static procedures and time history dynamic analysis available in literature. Most of these procedures, such as time history dynamic analysis, are complex as they require sophisticated finite element modelling. Reinforced concrete (RC) frames with masonry infill, for example, pose great challenge in modelling both the composite material behaviour and their interactions. With significant effort directed towards sustainable infrastructure development, a simplified nonlinear analytical procedure for evaluation of RC infill frames subjected to incremental horizontal loading is developed that can be used easily in integrated structural performance and sustainability evaluation. The method, developed on the premise of truss analogy and utilising the pushover analysis, assumes that all structural members of the RC frame are truss elements with homogeneous material properties derived on the basis of a pure axially loaded system and the infill masonry is converted into strut elements. Stiffness modification through evaluation of nonlinear stress-strain states is employed to generate the overall force-deformation behaviour of the structural system. Experimental data available in literature is used to validate the procedure.

An approach of steel plate hybrid bonding technique to externally bonded fibre-reinforced polymer strengthening system

The strengthening efficiency of externally bonded fibre-reinforced polymer to concrete structure is usually limited owing to the unexpected debonding of fibre-reinforced polymer laminates. In this study, a new steel plate hybrid bonding technique was developed to supply additional anchorage for traditional externally bonded fibre-reinforced polymer strengthening system. With this approach, the fibre-reinforced polymer debonding can be effectively prevented. Moreover, the stress concentration, which probably results in a premature fracture of fibre-reinforced polymer laminates as that performed for available hybrid bonding anchorage techniques, can be eliminated by introducing a steel plate between the mechanical fasteners and fibre-reinforced polymer strips. To verify the effect of this new method, 21 carbon fibre–reinforced polymer–strengthened beams were studied on the flexural behaviours. Test results showed that, compared to available hybrid bonding anchorage techniques, steel plate hybrid bonding is more capable of making the full use of fibre-reinforced polymer laminates and further enhance the ultimate capacity and ductility of externally bonded fibre-reinforced polymer–strengthened beams. Based on the experimental results, the effect of interfacial treatment, ply of carbon fibre–reinforced polymer and mechanical fastener spacing on the failure mode and ultimate load ratio were discussed. Eventually, a simplified analytical procedure was proposed and verified to estimate the flexural resistance of steel plate hybrid bonding – fibre-reinforced polymer–strengthened beam.