Value Of Reduction Factor Research Articles

Strength of masonry made of ceramic brick with ground and unground surfaces (comparison of Russian and European norms)

Introduction. In recent years, much attention has been paid to the issues of reducing labor costs and increasing the reliability of test results of masonry ceramic wall products (brick, stone, and blocks). It is noted that when determining the masonry strength limit, the levelling of brick support surfaces is performed with mortar. However, when levelling the support surfaces by grinding, the masonry strength limit is artificially overestimated by at least one grade. In order to increase the reliability of erected buildings and structures, Note 1 to Table 6.1 of SP 15.13330.2020 “Masonry and reinforced masonry structures” gives an indication of the need to introduce appropriate correction factors in determining the strength of masonry. In the previous version of the SP, the values of reduction factors were adopted without appropriate justifications.Aim. To justify reduction of design compression resistance of masonry made of ceramic soft-mud brick (when determining its compressive strength with grinding of supporting surfaces) in order to increase the reliability of erected buildings and structures.Materials and methods. Comparison of normative and calculated values of the strength of masonry made of ceramic soft-mud brick on conventional mortar according to the norms of the Russian Federation, as well as Britain and Germany, on the basis of which the European norms have been developed.Results. The conducted comparison of British, German, and Russian norms showed that the calculated values of masonry strength given in the norms of European countries are lower than those in the norms of the Russian Federation due to higher safety factors.Conclusions. The decrease in the design compressive strength of masonry made of ceramic soft-mud brick by 10 % (when grinding the supporting surfaces to determine the compressive strength) is recognized as reasonable.

Stable Slope Design Based On Limit Equlibrium Method (Lem) And Finite Element Method (Fem) At Pit X, Lahat, South Sumatra

Coal mining process using open pit mining method is closely related to slope stability. A slope whose stability is disturbed will have a higher potential for landslides. The slope stability analysis in this research is conducted by Limit Equilibrium Method (LEM) with the calculation of Morgenstern-pice slice method and Finite Element Method (FEM) with the calculation of Shear Strength Reduction. The highwall simulation was modeled with a Bench height of 10 meters, Bench width of 6.5 meters and bench tilt angle varying between 30°, 45°, 60° and groundwater condition using steady state FEA. From the results of the LEM analysis on the highwall with a bench tilt angle of 30 °, 45 °, 60 ° has a safety factor value of 1.005; 0.76; 0.584. While the results of the FEM analysis on the highwall with a bench tilt angle of 30 °, 45 °, 60 ° have a Strength Reduction Factor value of 0.98; 0.72; 0.57. Comparison of the safety factor values of the two methods has an average difference of 1-2%. This is because the FEM takes into account the stress-strain in the material which describes how the material behaves. The stable slope design based on LEM is a highwall slope with a Bench slope angle of 22° which has a safety factor value of 1.478 and based on FEM is a highwall slope with a Bench slope angle of 22° which has a Strength Reduction Factor value of 1.42.

Use of Recycled Construction and Demolition Waste (RCDW) in Geosynthetic-Reinforced Roadways: Influence of Saturation Condition on Geogrid Mechanical Properties

Replacing natural aggregates in infrastructure with recycled construction and demolition waste (RCDW) works helps to meet the requirements established by sustainable development. This environmentally friendly proposal undoubtedly becomes better when it is carried out with geosynthetics, providing better technical performance and positive economic impacts. However, the chemical characteristics of RCDW may result in the degradation of the geosynthetics and, therefore, must be assessed and quantified. This study aims to assess the chemical degradation caused by RCDW for the mechanical properties of two types of polymeric geogrids (polyester and polyvinyl alcohol). The study evaluates the influence of the RCDW saturation condition in the chemical degradation and the possible synergism between the launching damage (drop height) and chemical degradation. Watertight tanks were constructed to maintain the geosynthetic reinforced layers in flooded, dry and open-to-environment conditions, simulating paved and unpaved roads. The occurrence of degradation was evaluated and quantified by reduction factors related to the properties of interest using statistical analysis. The results have shown a significant influence of chemical degradation on the geogrid characteristics (especially tensile strength and secant tensile stiffness), which increased when the specimens were subjected to prior launching process simulation. The reduction factor values reported herein encourage the combined use of these materials (geogrid and RCDW) and highlight the importance of assessing the chemical degradation for the design purposes of geosynthetic-reinforced roadways with alternative materials.

Prediction of non-woven geotextiles’ reduction factors for damage caused by the drop of backfill materials

The need for sustainable solutions in geotechnical works has encouraged the investigation of recycled construction and demolition wastes (RCDW) as backfill material. The possible damages caused by the launching (dropping) process of this “new” backfill material (RCWD) must be quantified for its combined use with geosynthetics. This study evaluated the influence of the backfill's grain-size distribution and the geotextile's mass per unit area in the damages caused by the launch of RCDW material and aimed to provide a prediction equation of the reduction factors. Five RCDW materials were launched from 1.0-m and 2.0-m height over five non-woven polyester needle-punched geotextile and specimens were exhumed to be tested under tensile. Databases were created with the results and subjected to machine learning to obtain a prediction equation for the reduction factor's values. The results show that the damages caused by the dropping height are complex. The 1.0-m increase in the drop height and the increase in the geotextile's mass per unit area cannot be associated with an increase in the damage. The geotextiles were more affected by the backfills with uniform gradation. A reduction factor's prediction equation is presented considering the three variables investigated (geotextile, drop height and backfill material classification). The artificial neural network is a more interesting solution than multiple linear regression since it does not possess several application criteria and provides more accurate predictions.

COMBINED METHOD OF BULK MATERIAL SHIELDING EVALUATION FOR 200 MEV HIGH ENERGY NEUTRON SOURCE USING PHITS MODELLING AND PARTIAL DENSITY

Neutron encounters difficulties in shielding protection. Thus, many researchers have performed simulation and experimental research on neutron shielding materials. The characteristic of materials is highly dependent on neutron energy. The evaluation of neutron shielding for various materials, such as iron, concrete, aluminum, and borated polyethylene (BPE), was conducted in this paper through simulation using a Monte Carlo code of PHITS 3.27 and calculation via partial density method. A mono-energetic neutron source with an energy of 200 MeV is emitted perpendicular to the shielding material with a thickness of 105 cm. The parameters measured in this analysis include flux, fast neutron removal cross-section, neutron depth dose, ambient dose H*(10) equivalent, and neutron dose reduction factor (RF). Results show that iron is a good material against high-energy neutron and secondary photon radiation at the energy range with the highest removal cross-section and the lowest RF value (0.39), followed by concrete, BPE, and aluminum. The integrated fluence and effective dose profiles were consistent with previous results in the literature. Benchmarking calculation of neutron dose RF was conducted with other publications and was in good agreement within the value range.

Vision‐based seismic damage detection and residual capacity assessment for an RC shaking table test structure

AbstractIn this paper, the existing postearthquake performance assessment framework for reinforced concrete (RC) building structures is improved by adding a new feature of the computer vision‐based damage detection. In this framework, visible seismic damage is classified and quantified from photographs of damaged RC components using the developed deep convolutional network (CNN) Damage‐Net of semantic segmentation, and then the mechanical property degradation factors of components determined from the detected damage states are used to update the numerical model. Pushover analysis of the updated model assesses the residual capacity of the damaged structure. Large‐scale shaking table tests of a three‐story RC building structure, which was heavily instrumented with sensors and recorded with a large volume of photographs, were used as a case study to demonstrate the improved postearthquake performance assessment framework. The vision‐based approach accurately detected multicategory seismic damage of the test structure and effectively estimated the residual crack widths and angles under various lighting, image acquisition, and surface conditions. The updated model, which incorporated the mechanical property degradation of the damaged components, provided accurate estimate on the fundamental vibrational frequencies of the damaged structure after various levels of seismic motion shaking, which matched well with the system identification results. Using the mechanical property reduction factor values recommended by FEMA 306 & Chiu et al., pushover analysis of the updated models provided residual capacity curves that reasonably captured the measured hysteretic responses of the structure. In addition, the damage states of components as estimated by the vision‐based methods were also compared with the measured plastic hinge rotation data. The successful implementation of the vision‐based assessment in this test case indicates its potential for application in the postearthquake evaluation of buildings.

Effects of Electrical Pulse Width and Output Irradiance on Intense Pulse Light Inactivation.

The effects of electrical pulse width and output irradiance on the inactivation effect of intense pulse light (IPL) are studied in this paper. The measured radiant efficiency of pulsed xenon lamp can be more than 50%, and its irradiance can reach levels 100-times greater than that of a low-pressure mercury lamp. Staphylococcus aureus is used in inactivation experiments. When the irradiance and dose are both constant, there is no significant difference in inactivation efficiency when the pulse width is changed. However, a narrow pulse width corresponding to high irradiance at the same single-pulsed dose displays better inactivation effect. Experimental results are compared between the xenon lamp and low-pressure mercury lamp. The reduction factor (RF) value of the xenon lamp is more than 1.0 higher under the condition of both the same dose and irradiance. In order to achieve the same RF value, the dose of continuous-wave light must be at least three-times greater than that of pulsed light. The spectral action of the pulsed light is also studied. It is confirmed that UVC plays a major role across the whole spectrum. The experimental results show that extreme high-pulsed irradiance presents the main contributing factor behind the excellent bactericidal effect of IPL.

Durability of FRP bars and FRP bar reinforced seawater sea sand concrete structures in marine environments

• Combination of the alkaline and marine environments aggravates the degradation of mechanical properties of FRP bars. • The variability of mechanical properties of FRP bars shows an increasing trend. • Bearing capacities of FRP bar reinforced SSC components decrease and the failure mode changes. • Environmental reduction factors in current codes are conservative. Fiber reinforced polymer (FRP) is one of the alternatives to steel, and can be directly used in seawater sea sand concrete (SSC). But FRP material still has durability problems in corrosive environments, which is one of the hot and difficult issues of current research. Based on the existing literature, this paper combs the degradation of the long-term property of FRP bars and the durability of FRP bar reinforced SSC (FRP-SSC) structures in the marine environment. The combination of the alkaline environment of concrete and the salt ions in sea sand and seawater aggravates the dissolution of the resin and debonding of the fiber-resin interface of FRP bars (particularly for BFRP bars). Therefore, the mechanical properties of FRP bars degrade with high variability which leads to the reduction of bonding between SSC and FRP bars. Additionally, the bearing capacity of FRP bar/steel-FRP composite bar (SFCB) reinforced SSC components in marine environments decreases, and the failure mode of components changes. The current codes use environmental reduction factors in the durability design of FRP bar reinforced concrete structures. But the values of reduction factors are conservative. Finally, it is pointed out that the quantification of variability for the mechanical property of FRP bars after long-term service, and the time-dependent reliability-based design methods of components are needed for further studies.

The efficacy and safety of electrolyzed water against Covid-19 as an alternative hand sanitizer.

Aim To investigate the efficacy of electrolyzed water against viruses and its safety to the skin. Methods Virus culture was carried out at level-3 Bio-Safety (BSL3) facilities. The test material was prepared at room temperature mixed with one part virus suspension and one organic load. As an antiseptic and disinfectant control, 0.7% formaldehyde was used. Cytotoxic effects of electrolyzed water were performed on Vero cells. In order to assess the safety of electrolyzed water, a skin sensitivity test was conducted for electrolyzed water exposure. Results Electrolyzed water has a higher value of reduction factor than antiseptic and disinfectant control, formaldehyde, and it was statistically different from control. Cytotoxicity test results on Vero cells showed that electrolyzed water demonstrated safety in Vero cell viability. As many as 58 participants who met the inclusion criteria took electrolyzed water sensitivity test to the skin. The sensitivity test showed that participants with reactions to electrolyzed water were all female, with a mean age of 32.6 years. The patch-test was positive in 3 of 4 participants who reacted to the product. Conclusion Electrolyzed water is effective as a new antiseptic and disinfectant against viruses and safe for human skin.

Reliability-based assessment and optimization for the two-way shear design of lightweight reinforced concrete slabs using the ACI and EC2

Recent brittle two-way shear failures have made assessing strength models a topic of interest. In addition, the economic alternatives have made lightweight reinforced concrete slabs (LWRCS) a popular choice of construction in many areas around the world. However, researchers have rarely tackled the two-way shear strength models of LWRCS using accurate structural reliability analysis methods. Most of the research investigations evaluated the performance of the two-way shear strength models for the LWRCS with respect to an experimental database using statistical measures. While it did not implement structural reliability methods, which could include the variability due to the following: (1) the governing variable’s random distribution; (2) the size of the experimental database; and (3) errors in measurements, construction, and design. Thus, this current study aims to apply structural reliability methods for the two-way shear of LWRCS. Two internationally renowned design codes were selected using an extensive experimental database. A brief outline of existing structural reliability methods is presented and compared. A selected reliability method was used to assess the reliability of the design-chosen codes. The reliability and sensitivity indices were calculated for the American and European design code provisions of two-way shear of lightweight concrete and compared with each other as well as international standard reliability. The American design code were found to be less reliable compared with the European, which might be due to not considering the flexure reinforcement ratio in the model. In addition, model accuracy is the main factor affecting reliability, however, the variability of basic parameters including concrete density, concrete strength and cross section depth have larger effect compared to flexure reinforcement ratio and loading area dimensions. Moreover, in order to achieve target reliability indices value of 3.8, 3.7, or 3.6 a reduction factor value of 0.8, 0.75, or 0.70 could be implemented. These findings could be helpful in design code developments. However, the results are limited to the selected variability of the random variables.

Assessment of Strength Reduction Factor on Concrete Moment Frames According to the New Venezuelan Seismic Code

Nonlinear static analysis is a validated tool for the seismic evaluation of existing and new structures, specifically for reinforced concrete buildings. In order to assess the performance of reinforced concrete frames designed according to the new Venezuelan seismic code, configurations of low-, medium-, and high-rise concrete buildings are subjected to 20 different load patterns considering the nonlinear behavior according to FEMA P695. A total of 140 concrete frame models were analyzed using modal response spectrum analysis and nonlinear static pushover analysis. The parameters considered for analyzing the models were the response reduction factor (R), the overstrength factor (RΩ), and the ductility factor (Rµ). The results showed a performance controlled by ductile failure mechanisms in low-rise models unlike combined failure mechanisms with columns with plastic hinge in high-rise models. Reduction factor values between 4 and 14 were obtained. In addition, the pushover curves were affected by the load patterns; therefore, it was necessary to identify the representative patterns, refusing the rest of the patterns. A statistical adjustment was performed using a log-normal distribution. The strength reduction factor specified in the new Venezuelan code was higher than the values obtained for the 95% confidence levels according to the distribution assumed in the reinforced concrete frames models. Finally, the strength reduction factor more representative is R = 4.

Probabilistic calibration of the strength reduction factor for the design of rectangular short concrete columns reinforced with FRP bars under eccentric axial loading – Update of ACI 440 rules

The design of concrete columns reinforced with fibre-reinforced polymer (FRP) bars is currently debatable. The present study proposes a reliability-based approach with the objective of calibrating the optimal strength reduction factor for the design of short rectangular FRP-RC columns under eccentric axial loading according to the ACI-440 guide. The reliability approach relies on a fast hybrid first-order reliability method (FORM)-based response-surface (RS) method. The results of such a hybrid approach have been validated using a Monte Carlo importance sampling (MC-IS) technique. The uncertainty of geometrical, material and loading variables is considered through various dedicated statistical distribution laws. Several design parameters have been considered: load eccentricity, aspect ratio of the concrete section, reinforcement ratio, live to dead load ratio, strength of concrete, and grade of FRP bars. In addition, Top-Bottom and Uniform reinforcement configurations, which are preferred for high- and small-load eccentricities, respectively, are considered. To ensure the generalization of the approach, full combinations between the design parameters are performed, resulting in more than 10 5 structural classes. Thus, calibrated strength reduction factors can cover a wide range of design situations. After demonstrating the possible inappropriateness of ACI-440 rules, the study proposes a novel approach to choose the strength reduction factors based on a quadratic function of the live-to-dead load ratio and load eccentricity. Eventually, the study presents recommendations for the selection of reduction factors distinguishing small and high load eccentricity and concludes with a working example. • A probabilistic calibration of the strength reduction factor given by ACI 440.1R-15 rules is implemented. • More than 100 000 structural classes and two reinforcement configurations are studied to provide a general safety factor. • Live to dead load and load eccentricity to section height ratios significantly affect the strength reduction safety factor. • Recommendation to update strength reduction factor value at 0.6, to be compliant with reliability requirements is made.

Post-buckling Strength of Welded Steel I-Girders with Corrugated Webs

Steel I-section-plate girders with corrugated webs have been used worldwide as they provide more stability and light beam features in practical design. It is known from previous investigations that due to having numerous favourable properties, the corrugated-web beams have been used in different areas of structural engineering. Considering the raising popularity of using CWBs in steel design, some practical aspects of CWBs need to be investigated further, in which post-buckling strength is one of the most critical strengths that should be precisely estimated. To fulfill this requirement regarding the post-bucking strength determination for structural designers community, a numerical investigation has been conducted in this study to determine the moment capacity reduction factors for steel I girders with corrugated-web profile and to compare reduction factor values extracted from EN 1993-1-5 (Design of steel structures part 1–5: Plated structural elements, Eurocode 3, Brussels, 2006), AS4100 (Steel structures, Standard Australia, Sydney, 1998), and finite element analysis. Theory of Ultimate Limit State design has been adopted in accordance with AS4100 (1998) along with considering geometric and material non-linearity in the numerical analyses in SAP2000 software. Eventually, the results of the parametric study have been compared and discussed leading to presenting practical recommendations on the design of CWBs for bending strength.

Response Reduction Factor For Different Heights of RC Structure

Seismic analysis is considered as an important parameter for any structural design. The strength and ductility of frame members in seismic design depends on the response reduction factor. In this paper four symmetrically framed structures are considered of different heights under the critical zone condition. The primary emphases of this work is regarding calculation of response reduction factor values attained from designing RC framed structures. The results are computed by applying non-linear static pushover analysis. SAP-2000 software is used for analyzing the non-linear behaviour of the structure.

Geogrid installation damage caused by recycled construction and demolition waste

Using recycled construction and demolition waste (RCDW) in geosynthetic reinforced soil (GRS) structures presents attractive environmental and economic aspects. However, bearing in mind installation damage can be responsible for significant changes in geosynthetic tensile-strain behavior, the damage caused by the RCDW must be assessed and quantified. This study aims to investigate the occurrence of mechanical damage during the installation of geogrids with RCDW backfill material using an in-field test facility. In order to understand the mechanisms related to the damage, the influences of the dropping height and compaction method were investigated. Statistical analysis using the Student's t-distribution was carried out to validate the occurrence of damage and calculate reduction factors for geogrids’ tensile strengths. Results revealed that dropping processes reduced the geogrid ultimate tensile strengths, but the compaction methods caused the highest reductions. The reduction factor values encourage the design of GRS structures with RCDW, an interesting option to satisfy the technical and economic aspects required for these structures in agreement with the environmental concerns.

Displacement-Based Design of RC Frames Using Design Spectra of Indian Code and Its Seismic Performance Evaluation

A set of 4-, 8-, 12-, and 15-storied reinforced concrete moment resisting frames were analysed and designed by direct displacement-based design method and performance-based plastic design method. The design spectra of Indian Standard IS 1893:2016 have been used for the calculation of base shear after its proper synchronization with respect to both the methods. The seismic performance evaluation was done by nonlinear static pushover analysis, and the parameters of comparison were (a) pushover curves, (b) storey drifts and (c) response reduction factor. Results show satisfactory performance of both the methods in terms of capacity and deformation. The response reduction factor values obtained for both approaches are greater than the IS 1893:2016-specified value which indicate the enhanced ductility for both methods.

Lateral-Torsional Buckling Behaviour of Triangularly Corrugated Web Beam

Lateral torsional buckling (LTB) is a common failure mode of large span beams. In this phenomenon, the beam becomes unstable along the unbraced length. This instability of beams can be identified by out-of-plane deflection and twisting. In this paper LTB strength of triangularly corrugated web beams under bending condition is investigated. Examined steel beams consist of two flanges and a thin triangularly corrugated web, connected by automatic welding. In the literature, the LTB strength problem of steel beams was dealt with mostly for steel beams with plate, sinusoidal and trapezoidal corrugated webs. Researches of the LTB behaviour of beams with triangularly corrugated webs were found out to be very limited. A parametric study is carried out for various beam spans and corrugation densities. A general-purpose finite element program (ABAQUS) was used. The corrugation densities adopted in this study represent practical geometries, which are common used for such structures in building practice. Plot showing the influence of compressed flange slenderness on value of reduction factor for LTB is presented. It is determined that existing buckling curves poorly describe the change of reduction factor depending on slenderness of compressed flange for triangularly corrugated web beams. Finally, recommendations were proposed for the design of simple supported steel beams with corrugated webs against lateral torsional buckling in accordance with numerical results.

Buckling behavior of steel column with triangularly corrugated web

The paper presents a study of behaviour of axially loaded columns that consist of two flanges and a thin triangularly corrugated web, connected by automatic welding. In the literature, the buckling behaviour of steel columns was dealt with mostly for members with plate webs. Researches of that problem for columns with corrugated webs were found out to be very limited. A parametric study is carried out for various column slenderness and corrugation densities. A general-purpose finite element analysis software ABAQUS was used. The corrugation densities adopted in this study represent practical geometries, which are commonly used for such structures in building practice. Plot showing the influence of section slenderness on value of reduction factor for lateral buckling is presented. It is determined that existing buckling curves poorly describe the dependence of the reduction factor on slenderness for axially compressed members with triangularly corrugated webs. Finally, recommendations were proposed for the design of pin-ended columns with corrugated webs at lateral buckling in accordance with numerical results.

Accuracy Assessment of Nonlinear Seismic Displacement Demand Predicted by Simplified Methods for the Plateau Range of Design Response Spectra

The nonlinear seismic displacement demand prediction for low‐period structures, i.e., with an initial fundamental period situated in the plateau of design response spectra, is studied. In Eurocode 8, the computation of seismic displacement demands is essentially based on a simplified method called the N2 method. Alternative approaches using linear computation with increased damping ratio are common in other parts of the world. The accuracy of three methods for seismic displacement demand prediction is carefully examined for the plateau range of Type‐1 soil class response spectra of Eurocode 8. The accuracy is assessed through comparing the displacement demand computed using nonlinear time‐history analysis (NLTHA) with predictions using simplified methods. The N2 method, a recently proposed optimization of the N2 method, and the Lin and Miranda method are compared. Nonlinear single‐degree‐of‐freedom systems are subjected to several sets of recorded earthquakes that are modified to match design response spectra prescribed by Eurocode 8. The shape of Eurocode 8 response spectra after the plateau is defined by a constant pseudovelocity range (1/T). However, the slope of this declining branch may be specified using precise spectral microzonation investigation. However, the N2 method has been found to be particularly inaccurate with certain microzonation response spectra that are characterized by a gently decreasing branch after the plateau. The present study investigates the impact of the slope of the decreasing branch after the plateau of response spectra on the accuracy of displacement demand predictions. The results show that the accuracy domain of the N2 method is restricted to strength reduction factor values around 3.5. Using the N2 method to predict displacement demands leads to significant overestimations for strength reduction factors smaller than 2.5 and to significant underestimations for strength reduction factors larger than 4. Fortunately, the optimized N2 method leads to accurate results for the whole range of strength reduction factors. For small values of strength reduction factors, up to 2.5, the optimized N2 method and the Lin and Miranda method both provide accurate displacement demand predictions. However, the accuracy of displacement demand prediction strongly depends on the shape of the response spectrum after the plateau. A gently decreasing branch after the plateau affects the accuracy of displacement demand predictions. A threshold value of 0.75 for the exponent of the decreasing branch (1/Tα) after the plateau is proposed. This issue should be considered for the ongoing developments of Eurocode 8.

Seismic duration effect on damping reduction factor using random vibration theory

Damping Reduction Factor plays a key role in scientific literature and Technical Codes, but till now existing formulations present differences and inconsistences probably because obtained by integration of real recorded events, thus sensible to specific used data. This paper investigates the relation between damping reduction factor and earthquake duration by means of random vibration theory. A stochastic process, that is non-stationary and filtered, is used to model a seismic event. The modulation function is suitably chosen to describe earthquakes characterized by different durations. The stochastic process peak theory allows to calculate damping reduction factor after the definition of the probabilistic response of a simple linear visco-elastic oscillator. The variability with seismic duration for different soil conditions and damping ratios is investigated. The study points out that damping reduction factor is more sensitive to seismic duration in the range of high period and on rigid soil with respect to other conditions. The results show that, if damping ratio or effective duration values are increased, the damping reduction factor value diminishes.