Current Design Guidelines Research Articles

Current design guidelines’ streetscape improvement for visual perception and walkability: A case study of Sejong City, Republic of Korea

This study explores how recent design guidelines have focused on the visual variety of streetscapes making them more attractive. To date, this topic has been one of the most challenging parts of constructing walkable streets. We evaluated the streetscape features of Sejong City, recently constructed as Republic of Korea's new capital city, and investigated their relationships with design guidelines. Consequently, we identified three principal reasons related to the design guidelines for the visual monotony in the street produced by the most up-to-date design guidelines compared with an ordinary street. First, the design guidelines cannot restrict the construction of large-scale buildings on the street, hindering visual changes caused by the zoning ordinance regulations because zoning regulations took priority when it comes to urban planning and regulatory governance. Second, design standards intending for a consistent street wall of buildings, which were used only in regard to the street enclosure standard, produced less spatial diversity and indistinct building bases, presenting weak vertical articulation. Third, applying the uniform standards for each building created repetitive architecture despite design standards for visual variety, such as recessed top floors, arcades, and retail uses for the ground floors facing a street.

Numerical Parametric Study and Design of Pultruded GFRP Composite Channel Columns

This article reports the finite element (FE) investigation of the axial capacities of pultruded fiber-reinforced polymer (PFRP) composite channel columns. The nonlinear finite element model (FEM) was developed by using the ABAQUS package for glass fiber-reinforced polymer (GFRP) composite channel columns, which included geometric and initial geometric imperfections. The developed FEMs were verified against an experimental result available in the literature for GFRP channel columns. The validated FEMs were used to carry out the parametric study comprising 61 FE models to investigate the effect of different geometries, plate slenderness and the length of members on the axial capacities of GFRP pultruded channel columns. The results obtained from the parametric study were used to examine the accuracy of the current Italian guidelines, American pre-standard and the Direct Strength Method (DSM) proposed in the literature for GFRP channel profiles. Based on the obtained results, the suitability of the current design guidelines is assessed and, also, a new set of design equations is proposed to estimate the axial capacity of the pultruded GFRP channel columns. The new proposed set of reliable design equations witnessed a less scattered and a high degree of accuracy in determining the axial load capacity of the pultruded GFRP composite channel columns.

Fourier Series Approximation of Vertical Walking Force-Time History through Frequentist and Bayesian Inference

The increased ambition of architects coupled with advancements in structural materials, as well as the rapidly increasing pressure on civil engineering sector to reduce embodied carbon, have resulted in longer spans and more slender pedestrian structures. These structures often have one or more low natural frequencies in the range of human walking accompanied with low modal masses and damping ratios. Thus, they are prone to excessive and often resonant vibrations that may compromise the serviceability limit state. Principally the uncertainty in prediction of the vibration serviceability limit state mainly originates from unreliable estimates of pedestrian loading. The key rationale behind this situation is the limited mathematical characterisation featuring in current design codes and guidelines pertinent to pedestrian-induced loading. The Fourier approximation is typically used to describe individual walking forces. Historically, such models are based on limited experimental data and deterministic mathematical descriptions. Current industry used load models featured in design codes and guidelines have been shown to incorporate inherent bias through limited intra-subject variation and poor correlation with real walking loads. This paper presents an improved Fourier model of vertical walking force across multiple harmonics, presented in a Bayesian and Frequentist statistical parameterisation. They are derived using the most comprehensive dataset to date, comprising of over ten hours of continuous vertical walking force signals. Dissimilar to previous Fourier models, the proposed models attempt to encapsulate the surround energy leakage around harmonic integers with a singular value. The proposed models provide consistently lower force amplitudes than any previous model and is shown to be more representative of real walking. The proposed model provides a closer approximation of a structural acceleration than any other similar Fourier-based model. The proposed model provides further evidence to combine the so called high and low frequency load models.

Influence of reinforcement design on seismic stability of full-height panel MSE walls

A numerical study was carried out to investigate the seismic stability of mechanically stabilized earth (MSE) walls using a finite element limit analysis (FELA) approach. The numerical method was validated using results from shaking table tests and limit equilibrium (LE) analysis. A series of parametric analyses was subsequently carried out to examine the influences of reinforcement design on seismic stability and failure mechanisms in full-height panel MSE walls. Results of the study indicate that, as opposed to the linear or bilinear failure mechanisms typically assumed in current design guidelines, more complex failure geometries could form in the backfills that involve extended reinforcement, which can be captured and analyzed using the FELA method employed in this study. The results also confirm the current consensus that placing longer reinforcement layers at the top of the wall (i.e. tapering-down arrangement) can help improve its seismic stability. However, in shorter walls or when high-strength reinforcement is used, a tapering-up reinforcement arrangement could also lead to increased seismic stability.

Effects of Vertical Ground Motion on Pedestrian-Induced Vibrations of Footbridges: Numerical Analysis and Machine Learning-Based Prediction

Current codes and guidelines for the dynamic design of footbridges often only specify the pedestrian-induced excitations. However, earthquakes may occur during the passing stage of pedestrians in earthquake-prone regions. In addition, modern footbridges tend to be slender and are sensitive to vertical ground motions. Therefore, we investigate the effects of vertical ground motion on pedestrian-induced vibrations of footbridges. A total of 138 footbridges with different materials, dimensions, and structural types are considered as the target structures. The classical social force model combined with the pedestrian-induced load is used to simulate crowd loads for the scenarios with six typical pedestrian densities. Furthermore, 59 vertical ground motions with four seismic intensities are taken as the seismic inputs. An amplification factor is introduced to quantify the amplification effects of vertical ground motion on human-induced vibrations of footbridges. Four machine learning (ML) algorithms are used to predict the amplification factor. The feature importance indicates that the scaled peak ground acceleration, the pedestrian density, and the bridge span are the three most important parameters influencing the amplification factor. Finally, the vibration serviceability of the footbridge subjected to both crowd load and vertical ground motion is assessed.

Fluidelastic instability of a curved tube array in single phase cross flow

Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6x9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability.

Experimental analysis of corroded RC continuous beams rehabilitated by ICCP-SS under unsymmetrical loading

In this study, a total of 14 corroded reinforced concrete (RC) continuous beams rehabilitated by a dual function system—Impressed Current Cathodic Protection-Structural Strengthening (ICCP-SS) with carbon-fabric reinforced cementitious matrix (C-FRCM), were tested under in-plane bending (resulted from unsymmetrical loading) to investigate the influences of corrosion rate, layer of carbon fabric mesh, complete wrapping as the end anchorage and loading scheme. The flexural behaviour including failure modes, load-carrying capacities, load-deflection curves and ductilities of the specimens were carefully studied. The design flexural strengths were calculated based on the current design guidelines, which were compared with the experimental results. It’s shown from the experimental data of five-point bending tests that beams strengthened with C-FRCM had higher yielding loads and ultimate loads than corroded beams without rehabilitation. However, the ductility of RC continuous beams was weakened by the C-FRCM strengthening method and its anodic polarization process, in particular for the specimens with more layers of carbon fabric meshes in prefabricated C-FRCM plates and complete wrapping as the end anchorage. Under unsymmetrical loading scheme, the delamination failure of concrete cover was observed and the application of complete wrappings was found to improve the ductility of the specimen. Comparison of the measured and predicted moment capacities showed that the current design guidelines generally underestimate the moment capacities of C-FRCM strengthened RC continuous beams, especially the specimens further strengthened by complete wrapping.

Research and Design Considerations for Presentation of Non-Safety Related Information via In-Vehicle Displays during Automated Driving

As automated vehicles become more prevalent on roadways, it is necessary to study driver behaviors in interacting with such systems. With higher levels of vehicle automation, drivers may become less engaged with the roadway environment. As a result, how to effectively bring non-safety related information (e.g., guide and service sign content) to a driver’s attention is an open research question. In this review, we summarize current literature on three domains of research, including: (1) the design and effectiveness of traditional road signage, (2) human factors considerations in vehicle automation design, and (3) current design guidelines for in-vehicle information presentation. Based on the review, including empirical studies, we identify knowledge relevant to communicating road signage information in automated vehicles. We propose a framework highlighting various factors that could determine the effectiveness of in-vehicle messaging. The framework is intended to motivate future research on development of in-vehicle interfaces for highly automated driving.

Investigations of the long-term extreme buffeting response of long-span bridges using importance sampling Monte Carlo simulations

Several studies have shown that site measurements of the buffeting responses of long-span bridges do not always agree with predictions from analytical models. The observed discrepancy is believed to be explained by the variability in the wind’s turbulence field, which is ignored in the current design guidelines. Additionally, the guidelines neglect the true variability in the buffeting response, as this parameter is considered to be deterministically dependent on the mean wind speed only, and a single short-term-averaged wind condition is assumed to be representative of the bridge’s behaviour over its lifetime. Such assumptions underestimate the design buffeting response. Alternatively, a full long-term analysis is regarded as the most accurate approach to handling extreme response estimations. Applications of this analysis in the wind engineering literature are scarce due to its large computational demand. With the objective of alleviating such demand, this paper proposes a full long-term analysis framework based on importance sampling Monte Carlo (ISMC) simulations and investigates, for the first time, the extreme buffeting response of a suspension bridge in its design phase with this framework. The results were compared with available formulations based on reliability methods and numerical integration. The proposed ISMC framework requires fewer simulations than the other formulations while maintaining a good degree of accuracy. The results show that the estimated extreme response is 30% larger than the current design guidelines suggest, showing the importance of considering the turbulence parameters' and loading effects' variabilities when calculating extreme responses.

Public open space in high density cities: the case of Hong Kong

ABSTRACT Using a combination of empirical research methods such as spatial analysis and on-site observation, this article aims to shed light on the physical and social characteristics of 27 Public Open Spaces (POSs) in Central and Western Districts in Hong Kong. This study will contribute to a better understanding of their role, function and usage, so as to help establish a broader strategy for the revitalisation and upgrading of these important public resources. The results of the analysis indicate that a large percentage of the POSs examined have several shortcomings that may contribute to their low usage, and which render them unattractive. Poor accessibility, outdated design principles, the absence of active frontages and a lack of flexibility in the use of the space are some of the factors that the rigid application of planning policies have produced over the years. As such, this study suggests that a revision of current urban design guidelines, in light of the shortcomings that they have inadvertently generated, could establish a new direction in the provision and management of POSs in Hong Kong, providing new opportunities to create a more sustainable and people-friendly urban environment.

Stochastic Continuous Modeling for Pillar Stress Estimation and Comparison with 2D Numerical, and Analytical Solutions in an Underground Stone Mine

Pillar collapses are events that due to their severe consequences can be classified as high risk. The design of pillars in underground room-and-pillar operations should migrate to risk-based design approaches. The authors of this work proposed a risk-based pillar design methodology that integrates stochastic discrete element modeling for pillar strength estimation, and stochastic finite volume modeling (FVM) for stress estimation. This paper focuses on the stochastic FVM component for stress estimation. The mining and geomechanical aspects of a case study mine (CSM) are described and pillar stresses are estimated by using three approaches: (1) analytical solutions, (2) 2D finite element modeling, and (3) 3D finite volume modeling. This operation extracts a 30° dipping deposit, which makes current underground stone mine design guidelines inapplicable for this CSM. This work compares results from each stress estimation approach and discusses uses the point estimate method as a simplified stochastic approach to evaluate the effect of rock mass elastic properties variability on pillar stress distribution. Results from this work show that the three estimation approaches lead to different estimations, possibly, due to the wide range of assumptions each estimation approach considers. It was also determined that the horizontal to vertical stress ratio has a significant impact on pillar stress magnitude. Therefore, it is recommended to perform in situ stress measurements, or assume worst-case-scenario values to account and reduce uncertainty due to this parameter. The stochastic stress estimation approach used in this paper provides results that can integrate a risk-based pillar design framework.

Machine Learning Models for Predicting Shear Strength and Identifying Failure Modes of Rectangular RC Columns

The determination of shear strength and the identification of potential failure modes are the crucial steps in designing and evaluating the structural performance of reinforced concrete (RC) columns. However, the current design codes and guidelines do not clearly provide a detailed procedure for governing failure types of RC columns. This study predicted the shear strength and identified the failure modes of rectangular RC columns using various Machine Learning (ML) models. Six ML models, including Multivariate Adaptive Regression Splines (MARSs), Naïve Bayes (NBs), K-nearest Neighbors (KNNs), Decision Tree (DT), Support Vector Machine (SVM), and Artificial Neural Network (ANN), were developed to calculate the shear strength and to classify the failure modes of rectangular RC columns. A total of 541 experimental data samples were collected from literature and utilized for developing the ML models. The results reveal that the ANN and KNNs models outperformed other ML models in predicting the shear strength of rectangular RC columns with the R2 value larger than 0.99. Additionally, the KNNs model achieved the highest accuracy, mostly 100%, for identifying the failure modes of rectangular RC columns. Based on the superior performance of the ANN and KNNs models, a graphical user interface was also developed to rapidly predict the shear strength and failure modes of rectangular RC columns.

An appraisal of the Vierendeel mechanism capacity of cellular beams with sinusoidal openings

The aim of this research is to investigate the performance of castellated beams with sinusoidal openings against Vierendeel mechanism (VM). Material nonlinear finite element (FE) analyses were conducted in two beams subjected to four-point bending with geometries selected to exhibit the desired plastification mode. Results of simulations revealed failure mode associated with the formation of four predominant plastic hinges along with shear yielding of the web-post necked region. Differently from the usual castellated beams with hexagonal or cellular openings, the critical hinges did not form at the ‘corners’ around a single opening, but at the innermost and outermost ‘corners’ at shear span. A significant stress redistribution could also be observed during the plastification process. The observation of a unique diagonal stress pattern along the web of the analyzed beams inspired the development of a simple two-dimensional model to predict the performance. A simplified nonlinear procedure was successfully developed to assess the evolution of plastification process with loading, with good agreement with the FE model and with an experimental result reported elsewhere in literature. Finally, it is shown that the current design guidelines for castellated beams (hexagonal and cellular) are not readily applicable to beams with sinusoidal openings for assessment of VM capacity.

A climate classification for corrosion control in electronic system design

Climate factors such as humidity and temperature have a significant impact on the corrosion reliability of electronic products. Given the huge geographical variability in climate conditions globally, a climate classification is a useful tool that simplifies the problem of considering climate when designing electronics packaging. Most current guidelines for electronic product design rely on the Köppen–Geiger classification first developed by Köppen over a century ago. Köppen devised a set of heuristics to separate climates to match different vegetation types. These climate classes are unlikely to be the optimal for electronic product design. This paper presents a new climate classification using parameters important for corrosion reliability of electronics. The classification is based on real climate data measured every 3 h during a 5-year period at over 9000 locations globally. A key step is defining relevant features of climate affecting corrosion in electronics. Features related to temperature are defined, but also the amount of time that the difference between Temperature and Dew Point is less than 1, 2 or 3 ℃. These features relate to the risk of condensation in electronic products. The features are defined such that diurnal, seasonal and yearly variation is taken into account. The locations are then clustered using K-means clustering to obtain the relevant climate classes. This data-driven classification, based on key features for corrosion reliability of electronics, will be a useful aid for product design, reliability testing and lifetime estimation.

The convergence or divergence of design characteristics in determining the recall and persuasiveness of seaside destination slogans

Current slogan design guidelines mainly focus on the unilateral effectiveness of the design characteristics (i.e., recall or persuasiveness). The underlying academic conjecture is that the recall and persuasiveness of slogans are driven by the same design characteristics. This study empirically tests the validity of this conjecture. We use slogans of China's seaside destinations and investigate the influences of eight design characteristics on the combined effects of recall and persuasiveness. The moderation of destination familiarity reveals that the driving characteristics of recall and persuasiveness converge to a certain extent in familiar destinations' slogans; but diverge substantially in unfamiliar destinations' slogans. The contributions of this study are twofold. From a theoretical perspective, verifying the conditional effects of important design characteristics prevents the separation of recall and persuasiveness in destination slogan research. From a managerial perspective, different methods of slogan design can be developed for familiar and unfamiliar destinations.

High step‐up active switched coupled inductor DC‐DC converter with voltage multiplier

AbstractHigh step‐up DC‐DC converters are commonly used in new energy applications such as DC microgrid, photovoltaic cell, and fuel cell. Thus, this article introduces a new nonisolated high step‐up DC‐DC converter based on active switched coupled inductor with a voltage multiplier cell. The proposed converter presents low current and voltage stress across the switches owing of the dual active switches structure. Besides that, by the voltage multiplier cell (one diode and one capacitor), the voltage gain of proposed converter is increased. In addition, it can be highlighted that the proposed converter has low component count, simplicity of operation in continuous and discontinuous conduction mode, and energy stored in the leakage inductor that is recycled in the capacitor of voltage multiplier cell. This article discussed the principle of operation, the ideal and nonideal voltage gain, external characteristic, voltage and current stress, design guidelines, and performance comparison with previous high step‐up converters. Finally, a prototype circuit with input power 300 W, input voltage 30 V, and output voltage 400 V was built in the laboratory to verify the theoretical evaluation, and the maximum achieved efficiency was 95.35% at nominal power 300 W.

Large-Scale Open-Jet Testing: A new frontier in structural wind Engineering

This study aims to meet the widely reported challenges associated with building aerodynamics by testing large-scale models in flows that exhibit complete turbulence (low- and high-frequency spectral content) at high Reynolds numbers. We tested 1:5 and 1:10 scale models of the Silsoe cube at multiple locations in the Louisiana State University (LSU) open-jet facility. The paper investigates the velocity-related parameters and the statistical quantities of roof pressures to yield a suitable scale and testing location in the facility. Moreover, we compare measured surface pressures with those from Tokyo Polytechnic University’s (TPU) wind tunnel and the Silsoe full-scale data to validate the results. We attempt to generate both small- and large-scale turbulence by employing the concept of flow without boundaries. The paper reveals the open-jet facility’s promising capabilities to produce mean and peak pressures on buildings, which accurately conform with the full-scale counterparts. The results suggest that the open-jet facility can generate realistic wind loads on low-rise buildings, a fundamental step towards reconciling current design guidelines for the evolution of code and standard provisions.

Resilient Characteristics of Polymer Emulsion-Treated Sandy Soil

The current pavement design guidelines, for example, Mechanistic-Empirical Pavement Design Guide (MEPDG), heavily rely on the resilient moduli of pavement materials. Some locally available pavement materials may not meet the design requirements and often require the application of efficient stabilizers. Therefore, the characterization of natural and treated subgrade soils using resilient modulus is important for the design of durable flexible pavements. A research study was designed and conducted to investigate the effect of polymer emulsion treatment on the resilient characteristics of sandy soil, which is used in constructing highways and airport surfaces. A commercially available polymer emulsion was used to stabilize cohesionless soil, and an attempt was made to understand the influence of polymer emulsion dosage and curing time on the strength and resilient characteristics of treated soil mixtures. Several laboratory tests were conducted on mixtures prepared with different dosages and curing times to evaluate the improvement in unconfined compressive strength and resilient moduli properties of treated sandy soil. Multiple regression analyses were conducted on resilient moduli test results using two- and three-parameter models and identified the best model exhibiting a good fit with the experimental data. A case study was demonstrated using the resilient moduli of untreated and polymer emulsion-treated soil to determine the thickness of airfield pavement. Overall, the outcome of the study is expected to assist the state and federal agencies in stabilizing and using problematic sandy soils for constructing various pavement structures.

Sensitivity analysis of geometrical design parameters on the performance of conical plain bearings for use as main bearings in wind turbines

The failure of a wind turbine’s main bearing causes very high repair costs, as the entire drivetrain has to be disassembled with the help of an external crane. Just the costs for a crane for an offshore turbine can sum up to 200.000€ per day [1]. In contrast, segmented hydrodynamic plain bearings offer the advantage that individual bearing segments can be replaced on the tower without the use of an external crane, which offers great potential for savings in repair costs. However, this application requires new, innovative plain bearing concepts for which the current design guidelines are not applicable. This paper presents a simulation-based design approach for a plain bearing concept with conical sliding surfaces. Such a simulation-based approach with a multi-objective optimization is necessary, because due to the geometric complexity the manual, iterative design process is not efficient. In this paper, a bearing geometry optimized in terms of load distribution and friction losses was developed by applying this approach.

AWWA Water Science Author Spotlight

Having published an article in AWWA Water Science, Amir Alansari answered questions from the publication's editor-in-chief, Kenneth L. Mercer, about the research. Critical Elements of Flocculation in Drinking Water Treatment Amir Alansari and James Amburgey I'm a water treatment specialist at Stantec at their office in Winston-Salem, N.C. My research focus is primarily on coagulation chemistry and process optimization. Lately I've been working on developing new digital tools for predicting optimal coagulation conditions using artificial intelligence. It was a $5,000 stipend to participate in the Research Experiences for Undergraduates (REU) program over the summer at the University of North Carolina at Charlotte. I was in the civil and environmental engineering program and stumbled into the world of water treatment by chance. Amir won first place in the ACE19 student poster contest. Dr. Amburgey had the biggest influence on my career and on everything I have accomplished so far. I completed all three civil engineering degrees (bachelor's, master's, doctorate) working with him at the same university. In total, I spent 12 years under his mentorship, during which time I was able to freely follow my curiosity and work on whatever I wanted. The best advice I got from him was to use the time I had in graduate school to grow my skill sets as a researcher and an engineer as much as possible. My coauthor and I read a paper that was published in 1992 in Journal AWWA by Han and Lawler, where they mathematically showed that mechanical mixing played an insignificant role in the flocculation process. We recognized the implications of their work on the recommended design guidelines for flocculation; however, an extensive literature review did not yield any conclusive evidence that supported or challenged their theory. Our article presents results from a series of experiments we performed to measure the effects of various flocculation parameters (e.g., mixing duration) on settled and filtered water-turbidity removal efficiency and determine whether Han and Lawler were correct. I try my best to have a positive impact on the lives of people around me. I'd like to think that my work is contributing to the body of knowledge, even if it is a tiny contribution. Many of our current design guidelines are based on work done about four to six decades ago. There have been a lot of scientific and technological advancements since then. I believe water treatment design could benefit from a 21st-century overhaul, which would require a renewed research interest and collective effort from the research community, regulators, consulting engineers, and industry. The current funding model does not favor this type of research. It considers topics such as coagulation as matured topics, with nothing left to discover. Our research highlighted the benefits of optimizing coagulation conditions (via jar tests) using filtered turbidity as the performance metric instead of settled water turbidity. We found that jar-test mixing conditions had a significant effect on settled turbidity removals. This means that operators no longer have to “calibrate” their jar test procedures to get their results to match the full-scale process. It simplifies the optimization process by reducing the number of variables to just two—coagulant dose and coagulation pH—which ultimately means they can achieve better treatment performance while minimizing chemical usage. To learn more about Amir's research, visit his AWWA Water Science article, available online at https://doi.org/10.1002/aws2.1213.