Bridge Barriers Research Articles

Research on finite element simulation and full-scale-vehicle crash test of B750HL bridge barrier

How to raise the bridge barrier with a concrete base height of only 51 cm to SS level of protection is not yet studied. In order to effectively retrofit an existing concrete barrier design to meet new crash testing criteria, the structural dimensions and concrete strength of the existing bridge barrier were investigated, and finite element simulation analysis was carried out, and simulation suggested the existing barrier was insufficient. Based on the structural dimension design principles of bridge barriers, the existing structure of bridge barrier was designed after adding lightweight and high-strength B750HL material crossbeams and posts on top of the concrete base, and the bearing capacity of the bridge barrier was calculated based on the yield line theory. Then, a finite element simulation analysis model was established to study and analyze the blocking, guiding, and cushioning functions of the improved design of bridge barrier. Finally, full-scale-vehicle crash tests were conducted with the SS-level small car, bus, and tractor-van trailer for this bridge barrier design scheme. This paper is the world’s first to use B750HL steel as the material for the crossbeam and post of a bridge barrier with a concrete base height of only 51 cm. According to the research results, the B750HL bridge barrier, which was designed based on the calculation of structural dimension design and yield line theory, effectively reduces the increased constant load on the bridge deck caused by the extra crossbeams and posts. At the same time, it can reduce material costs and save engineering costs. After being verified by finite element simulation crash tests and full-scale-vehicle crash tests, the protective capacity of the B750HL bridge barrier was proven to meet the SS-level evaluation requirements of the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013). The research findings of this paper is that the finite element simulation crash tests can effectively simulate full-scale-vehicle crash test, and the finite element simulation crash tests is reliable. If the safety performance of the barrier in the finite element simulation crash tests meets the requirements, the probability of passing the full-scale-vehicle crash test is higher. Therefore, a design scheme is proposed for the B750HL bridge barrier to improve hybrid bridge barriers at a height of 51 cm or more based on various design methods.

Development and research of a SS-level universal double-beam assembled bridge barrier

A wide variety of bridge barriers are used on highways. The bearing capacities of different types of deck slabs are measured in this study by applying the yield line theory to determine the worst-case scenario. An improved configuration for the worst-case barrier base and deck slab is developed, namely the universal double-beam assembled bridge barrier, which can enhance the safety performance of exiting concrete-base bridge barriers. According to the simulated impact test results, the new barrier meets SS-level requirements in terms of containment, redirective, and buffering performance as specified in the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013). The barrier structure’s compatibility with various bases is also analyzed. SS-level impact tests are conducted on real vehicles, including cars, buss, and trucks. The results show that the safety performance of the new barrier configuration reaches SS-level, and the barrier is universally compatible with concrete bases with a height of 63 cm and above.

GFRP reinforced concrete curb: design, economic and regulatory considerations

This paper discusses the use of GFRP reinforcement application for concrete curb design and bridge barrier replacement projects. Unlike conventional steel bars, Glass Fiber Reinforced Polymer rebars have the considerable advantage of not being susceptible to corrosion, preserving the durability of the structures and reducing the maintenance costs during the service life of the bridge. An additional advantage is the low specific weight of the GFRP, which makes it possible to speed up the installation of the reinforcements on site, ensuring greater safety for operators. The paper compares, in terms of structural performance and overall costs, two curbs of the same geometry, one reinforced with classic steel bars, the other with GFRP bars, providing evidence that current code provisions can be practically implemented in typical design situations.

The golden gate bridge barrier is completed

The Golden Gate Bridge will finally erect a barrier at the end of this year. The death toll since its completion in 1937 is about 2000. Two a month still jump to their deaths. The bridge is tragically known as the number one suicide site in the world.

Parametric Study on the Aerodynamic Characteristics of Wind Guide Barriers for a Train–Bridge System

This paper presents a new type of wind guide barrier (WGB). Through wind tunnel experiments, the key parameters of three types of WGB were studied, as well as their effects on the aerodynamic characteristics of a high-speed train and blunt body box girder system, while the bridge deck wind field was investigated. The results show that the shielding effect is the main factor affecting the windproof performance of the WGB. When the WGB is installed, the mean wind pressure distribution on the train is comparable to that of using a vertical wind barrier while reducing barrier resistance and the resistance of the bridge–barrier system. At the same time, the WGB can guide the oncoming flow, resulting in an increase in the streamwise and vertical wind velocity ratios on the bridge deck, as well as an increase in the maximum aerodynamic coefficient on the train.

Structural intervention at one bridge decreases the overall jumping suicide rate in Victoria, Australia.

There is clear evidence that installing safety barriers is effective in preventing jumping suicides from high-risk bridges with only moderate displacement to other nearby bridges. However, the impact of barriers on jumping suicides across broader geographical areas is not well understood. We examined patterns in jumping suicides across the state of Victoria, Australia, after a safety barrier was installed at the West Gate Bridge which, before the installation of the barrier, was the site of approximately 40% of Victoria's jumping suicides. We used negative binomial regression analyses on Victorian data from 2000 to 2019 to compare rates of jumping suicides at the West Gate Bridge, other bridges and non-bridge jumping locations before, during and after the West Gate Bridge barrier installation. We conducted linear regression analyses to examine whether the distance travelled from the deceased's usual residence to the location of their jumping suicide changed between the before, during and after barrier installation periods. After installation of the barrier, there were no jumping suicides at the West Gate Bridge (rate ratio [RR]=0.00, 95% credible intervals [95% Cr]=0.00-0.0001) and there was strong evidence that the rate of jumping suicides at all locations declined by 65% (RR=0.35, 95% Cr=0.22-0.54). At other bridges, there was also evidence of a reduction (RR=0.31, 95% Cr=0.11-0.70), but there was no evidence of a change at non-bridge locations (RR=0.74, 95% Cr=0.39-1.30). After installation of the safety barrier at the West Gate Bridge, jumping suicide in Victoria decreased overall and at other bridges, and did not appear to change at non-bridge locations. Our findings show that when barriers are installed at a site responsible for a disproportionately high number of jumping suicides, they are not only highly effective at the site where the barriers are installed but can also have a prevention impact beyond the immediate locale at similar sites.

Experimental research and application of old combined bridge barriers with non-standard sections

To improve the protective performance of old combined bridge barriers with non-standard sections, this article has improved the guardrail scheme. The newly improved guardrail is evaluated by finite element simulation, yield line theory calculation, and a crash test to see whether it reaches class SA protection. The results show that the blocking, redirecting, and buffering functions of the improved scheme meet the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013), and its protection class reaches class SA. The bridge barrier with strict deformation control cannot be evaluated by the yield line theory calculation alone. Thus, the evaluation should be assisted with finite element simulation and a crash test. The improved scheme has been successfully applied to engineering practice. With simple construction, safety, and reliability, the scheme effectively reduces engineering costs and improves the protective performance of old combined bridge barriers with non-standard sections.

Research and Design of a Wing-Wall-Free Guardrail in Transition Between the Subgrade and the Bridge

Considering the difficulty and high cost of guardrail installation in the transition between the highway subgrade and the bridge, this paper proposes a wing-wall-free guardrail based on comprehensive research. It has carried out a performance analysis of material Q690 before proposing the scheme. It is found that this type of material has high yield strength and tensile strength as well as high plasticity. Accordingly, the guardrail structure of the transition section of the wing-wall-free guardrail is designed, and the DYNA numerical simulation is carried out to optimize the structure. Moreover, vehicle crash tests are used to verify the performance of the newly designed guardrail. The results of the above-mentioned research methods are as follows: the vehicle crash tests show that the wing-wall-free guardrail can reach a protection level of Grade SB, with a collision energy of 280 KJ. All performance indicators meet the industry standards. The guardrail can be used in the transition between W-beam subgrade guardrails and concrete or combined bridge barriers. This proposed guardrail is beautifully designed with low cost and great conveniency for installation and maintenance.

0356 Does Unconscious Socioeconomic Bias Influence Tele-evaluation of Obstructive Sleep Apnea? A Tele-Equity Exploratory Analysis

Abstract Introduction Telemedicine, once of limited scope, has become common and widespread due to the present and ongoing SARS-CoV-2 pandemic. Center to home delivery, the most common model, allows for convenient and efficient care. Concurrent with this groundshift, there is increasing attention to disparities in medical services, and how these disparities may impact patient outcomes. Telemedicine could be used to help bridge barriers to timely quality care, however, patient access and longstanding institutional biases may limit the potential. Healthcare providers must actively develop systems to ensure that telemedicine is optimized for people across the income spectrum. This exploratory analysis examined how economic disparities in patients being evaluated for obstructive sleep apnea may be associated with providers’ clinical impressions. The objective was to study the inter-method reliability of pre-test probability of obstructive sleep apnea assessed via telemedicine and in-person evaluations, and to compare that reliability between income classes. Methods This is a secondary analysis of a pre-pandemic interrater reliability study, conducted between March 2017 and January 2019. Our researchers completed a randomized, blinded study comparing the pre-test probability of obstructive sleep apnea between an in-person physician and a separate physician seeing the same patient via televideo conferencing. Patients referred to the University of Rochester (UR) Sleep Center were eligible for the study. Women and men 30-70 years old were invited to participate. The patients were not necessarily referred to the center for evaluation of sleep disordered breathing. Patients with dementia, hearing or visual loss, severe psychiatric or developmental illness, or not fluent in English were excluded. Patients had adequate computer literacy, access to high speed internet, and a computing device with appropriate video camera and microphone.The primary objective of the original study was to assess the interrater reliability between the in-person and telemedicine raters for pre-test probability of sleep apnea (high, moderate, or low). Providers used clinical judgement from the history and examination to determine pre-test probabilityFor this present analysis, we assessed the inter-method reliability separately for strata defined by reported annual income level: low income (< $50,000), middle income ($50,000-$100,000), and high income (> $100,000). Reliability was quantified for each stratum using weighted kappa statistics given the ordinal nature of the outcome variable, pre-test probability of obstructive sleep apnea (high, moderate, or low). Weighted kappa statistics were compared between the income strata (high vs. middle, high vs. low, middle vs. low). The operant statistic assumed an approximate standard normal distribution under the null hypothesis of equal kappa values in the two income strata. The Bonferroni method was used to adjust the p-values for the three pairwise comparisons performed among the three income strata. Results Data from 53 patients were avaiable for this analysis. 11 of these patients were in the low income group, 22 in the middle income, and 16 were in the high income group. 9 patients did not include their income bracket, and were not included in the analysis. Inter-method reliabilities, assessed using weighted kappa, were 0.83 (low income), 0.24 (middle income), and 0.66 (high income). When comparing between the strata, the kappa statistics were significantly different (p=0.005) between the low and moderate income groups. There was a trend between the high and moderate income groups that did not meet statistical significance (p=0.07). Conclusion The intermethod reliability was substantial in the low income stratum, moderate in the high income stratum, and slight in the middle income group based on the kappa statistic. There was a significant difference in the reliability values of telemedicine versus in-person assessments between the low and middle income brackets, and there was a trend between the high and moderate groups. Since the raters were unaware of the patients’ income levels, this association might suggest possible unconscious bias in evaluating for OSA. It may also suggest that beyond access to telemedicine technology, the quality of the care may also be influenced by socioeconomic factors. With telemedicine in its early stages, it is important to develop this technology that will minimize biases that could result from patients’ economic fortunes. Support (If Any) The study was funded by a grant from the American Academy of Sleep Foundation (AASM Foundation grant #163-FP-17).

A study into the alkali-silica reactivity of recycled concrete aggregates and the role of the extent of damage in the source structures: Evaluation, accelerated testing, and preventive measures

This paper covers the expansion of new concrete containing recycled concrete aggregates (RCA) produced from bridge barriers suffering different levels of damage due to alkali-silica reaction (ASR). RCA sourced from high-deterioration concrete produced a higher expansion than natural aggregate or RCA from low-deterioration concrete, although the difference is not high. The expansion of lab-prepared cylinders with RCA was higher than that of cores extracted from the old concrete elements. The standard accelerated mortar bar test and a modified version thereof customized to accommodate RCA's properties, including high absorption, was effective in predicting the expansion of concrete prisms containing natural reactive aggregates or RCAs cast with different cementing blends. Also, the Concrete Micro Bar Test used with suggested expansion limits at 28 and 56 days was found effective in predicting the expansion of concrete prisms at one or two years for samples with and without preventive measures.

Wind Tunnel Study on Aerodynamic Characteristics of the Train on Viaducts with a New Type of Wind–Noise Barrier Under Cross Wind

Traditional noise barriers are often designed only by considering its noise reduction effects, but designer ignores that it may transfer too much aerodynamic force to the bridge. In order to meet the wind resistance and noise reduction requirements of the elevated lines crossing an urban area at the same time, a new type of wind–noise barrier (NT-WNB) is proposed. The noise reduction effect is evaluated by a numerical method, and the influence of the wind–noise barriers’ rotation angle on the aerodynamic characteristics of a train–bridge system was studied by sectional model wind tunnel tests. The results show that the NT-WNB has effective noise reduction in the frequency range of 500–1600 Hz, and the noise reduction can be increased when install barriers with upward incline blade. Although an angle combination type of wind–noise barrier can optimize the lateral force and the lift of the train at the same time, which may cause high turbulence in the corresponding area. The NT-WNB can reduce the wind load of the bridge–barrier system by 22%, which is more conducive to the safety of the bridge and the barrier.

Structural Behavior of Novel Precast TL-5 Bridge Barriers Using Ultrahigh-Performance Fiber-Reinforced Concretes

Structural Behavior of Novel Precast TL-5 Bridge Barriers Using Ultrahigh-Performance Fiber-Reinforced Concretes

Faith in localisation? The experiences of local faith actors engaging with the international humanitarian system in South Sudan

Localisation, as it aims to shift power in the humanitarian system, will involve the increased inclusion of local faith actors, those national and local faith-affiliated groups and organisations that are often first, and last, responders in crises and have been responding in humanitarian contexts for many years, but often in parallel to humanitarian coordination mechanisms. In primary research in South Sudan with local faith actors and international humanitarian actors, this article aims to examine the inroads and barriers to local faith actor involvement in the humanitarian system and the realisation of localisation with local actors such as these. The research is based on an ethnographic study in which researchers were imbedded in a humanitarian project that aimed to help bridge divides between local faith actors and the international humanitarian system. The findings are based on one-on-one and group interviews with 89 participants from a range of international and local, and faith and secular, organisations. Findings indicate that local faith actors are active in responding to crises and want to be linked to the humanitarian system, but they feel distanced from it and pigeonholed as local faith actors. Formalisation through the appropriate registration systems and then training and networking with the humanitarian system helped them build legitimacy and feel confident to participate in humanitarian coordination. International humanitarian actors can help bridge barriers by understanding and connecting with the local faith actors and challenging their own assumptions about who local faith actors are.

Phylogeography of the Fiddler Crab Tubuca arcuata (Crustacea: Brachyura: Ocypodidae) in East Asia and Northern Vietnam.

The fiddler crab Tubuca arcuata (Crustacea: Ocypodidae: Gelasiminae) is widely distributed across East Asia and northern Vietnam. Particularly, this species inhabits estuarine mangroves and mudflats of the East Asian continent, as well as the main islands of Japan and the Ryukyus. By comparing sequences of the mitochondrial 16S, cytochrome oxidase subunit I (COI), and control region genes, two main clades of this species were elucidated. The northern (N) clade was mostly restricted to the region north of the Taiwan Strait, whereas the wide (W) clade could be found throughout the entire range inhabited by this species. Based on the distribution of the ancestral haplotypes of COI and the divergence time of the two clades, our findings suggest that the land bridge barrier present in the Taiwan Strait during glaciations might have played an important role in their cladogenesis, approximately 0.93 million years ago. Here, we propose that the distribution of the ancestral haplotype of the W clade in the Ryukyus and the main islands of Japan was determined by the Paleo-Kuroshio Current, whereas the modern distribution pattern is shaped by the modern Kuroshio Current and other warm currents during the crab reproduction season in the summer.

Analysis of Chloride Deterioration and Structural Safety Evaluation of Bridge Barriers

Recently, there has been an increase in the chloride deterioration of bridges on urban highways owing to the excessive usage of deicing agents in winter, thus necessitating repair and maintenance measures to ensure the durability of concrete. In this study, the status of the damages occurring in the concrete barriers, such as walls and median partitions, of bridges on urban highways in Seoul was investigated. After collecting a total of 306 cores from various sites, a chloride analysis test was performed on a total of 918 samples obtained by dividing each core into three parts. The results were analyzed using the depth, upper and lower parts of the barrier, damage conditions, and route. In addition, the safety of the structure was evaluated in the case of repair by removing the corroded reinforcing bars (main reinforcing bars and spacers) directly exposed to chloride.

Translation: A Key Component of a Hundred-Year Project

The Emory-Tibet Science Initiative (ETSI) has embarked on a historic endeavor of introducing a systematic and sustainable science education program within the traditional Tibetan monastic institutions. His Holiness the Dalai Lama, who conceived and supports this initiative, calls it a hundred-year project. From the very beginning, translation from English to Tibetan has been an integral part of this project because of the need to prepare course materials as well as to facilitate on-site classes and lab activities in the Tibetan language. Our translation process involves not just conveying novel and foreign concepts across cultures but doing so with a scientific language peppered with technical terms that are not readily representable in the target language. In addition to the linguistic barriers, cultural and technical ones further complicate the process of communication. A case in point is the concept of life, or correlation versus causation, or the view that consciousness is an emergent property of the brain, where each construct has its corresponding but differing concept in Tibetan Buddhism. When engaging with such existing parallel yet divergent terms or concepts, the translators must strike a delicate balance and avoid forsaking the distinctive characteristics and connotations involved. In this article, the ETSI translation team shares its journey—highlighting the needs felt, challenges faced, and solutions sought. We discuss the translation principles guiding our work and the handling of such scientific features as graphs, acronyms, units, chemical names, and formulas. We hope our work will inspire other similar projects around the globe and encourage them to continue bridging barriers to cross-cultural dialogues, promoting cross-fertilization of knowledge for human flourishing.

Beyond Spatial Proximity: The Impact of Enhanced Spatial Connectedness from New Bridges on Entrepreneurship

Various strands of work have explored how spatial proximity helps (metaphorically) bridge barriers to resource mobilization and foster knowledge transfer. However, much of that work takes spatial connectedness as a given. We argue that spatial connectedness is a distinct construct that affects the extent to which spaces are not just proximate but are actually able to link people, ideas, resources, and knowledge together. We explore one such source of connectedness—physical (not metaphorical) bridges. We find that the opening of newly built bridges enhances startup founding in the local geographic community. Beyond their impact on startup founding, newly built bridges also influence the organizing process for such ventures. This includes a positive impact on the entry of prospective founders into entrepreneurship and an increase in the number of early-stage investors. The subsequently founded ventures are also more likely to engage in recombination and to cross industry boundaries. We explore scope conditions around industry and connective heterogeneity. We also test for robustness to various modeling approaches. The discussion highlights contributions of these findings to the study of entrepreneurship, as well as of organizations and the institutional fields in which they operate.

Instrumentation Results of New Manual for Assessing Safety Hardware Crash Tested Barriers for William P. Lane, Jr. Bridge

Two new bridge barriers were crash tested in accordance with AASHTO Manual for Assessing Safety Hardware (MASH) guidelines for future use on the William P. Lane Bridge over the Chesapeake Bay: (1) a combination barrier consisting of a reinforced concrete parapet with a top steel rail evaluated for Test Level 4 (TL-4); and (2) a combination barrier consisting of a steel parapet with a top steel rail evaluated for test levels TL-4 and TL-5. For the first test configuration, the reinforced concrete barrier was attached to a representative overhang deck slab using anchor rods. In the vicinity of the vehicle impact points, load cells were installed to measure forces in anchor bolts, and strain gauges were attached to reinforcing bars to resolve measured strain data into forces through the overhang deck slab. In the second test configuration, the steel barrier was supported by evenly spaced representative floorbeams using a bolted base plate connection. Strain gauges were attached to elements of the barrier at support locations adjacent to the vehicle impact point to evaluate force transfer through the barrier system into the base plate connections. Linear potentiometers were installed to measure lateral dynamic deflection of the barrier near the vehicle impact region. This paper presents the analysis results of the force, strain, and displacement data measured in the barrier and deck structural components during crash load testing.

Unsupervised Machine Learning for Robust Bridge Damage Detection: Full-Scale Experimental Validation

This study focused on the development of damage detection indices using unsupervised Machine Learning with data obtained from tests of a full-scale bridge deck mock-up. Measured structural response to different live loads at various damage levels was analyzed and a detection tool, termed a novelty index, was developed. Three levels of damage were induced into the structure: crash-induced damage to the concrete barrier; “sawcutting” the entire height of the barrier; and extending the sawcut through the deck. Bridge response to passage of vehicles at various speeds was recorded for the undamaged structure and after introduction of each damage level. The main novelty of this work is development of the novelty index, its application and validation against measured field data from a full-scale field test of a mock-up bridge subjected to varying levels of damage. Data was incorporated into health monitoring frameworks previously developed by the authors (1, 2) and the viability of using Singular Value Decomposition (SVD) and Independent Component Analysis (ICA) as damage sensitive features were explored. Novelty indices were subsequently developed using two approaches: Left Singular Vectors (LSVs) of measured response, commonly known as Proper Orthogonal Modes (POMs); and Independent Component Modes (ICMs). It was shown that a novelty index based on POMs was relatively insensitive to vehicle load variability and speed when compared to ICMs. It was also shown that novelty indices based on POMs could detect the lowest amount of induced damage, which was caused by a crash into a bridge barrier. Damage induced by the collision did not lead to visible barrier cracks; however, a quantitative assessment indicated damage levels like damage caused by a “sawcut” of the barrier. This study shows that the proposed method has the potential to be a robust damage detection tool; however, its application for detecting damage types other than the one studies herein needs to be further investigated due to statistical nature of SVD.

Optimal design for the connector of bridge prefabricated concrete barriers.

The current optimization research on the connectors of prefabricated barriers uses experimental comparisons only and lacks theoretically based optimization methods as guidance. The primary objective of this study was to propose an efficient optimization approach to the connector design of prefabricated bridge barriers. This paper presents an efficient two-stage optimization approach to the connector design of prefabricated bridge barriers. In the first stage, the hybrid cellular automaton algorithm is used to perform dynamic topology optimization on the connector, and the best material distribution in the design domain is obtained. In the second stage, a kriging metamodel and genetic algorithm are combined to further optimize the size of the connector structure. With a prefabricated bridge as the engineering background, finite element models of a barrier system under impact load caused by a car crash were established. The above approach is utilized to optimize the design of the barrier connector. Results showed that the optimized connector structure greatly improved the overall performance of the barrier system while reducing the material consumption and costs. The proposed optimization approach can determine the optimal material distribution and size of the connector structure, thus providing guiding significance for the design and construction of connectors of prefabricated components.