Concrete Barriers Research Articles

Diffusive Transport of Dissolved Gases in Potential Concretes for Nuclear Waste Disposal

In many countries, the preferred option for the long-term management of high- and intermediate level radioactive waste and spent fuel is final disposal in a geological repository. In this geological repository, the generation of gas will be unavoidable. In order to make a correct balance between gas generation and dissipation by diffusion, knowledge of the diffusion coefficients of gases in the host rock and the engineered barriers is essential. Currently, diffusion coefficients for the Boom Clay, a potential Belgian host rock, are available, but the diffusion coefficients for gases in the engineered concrete barriers are still lacking. Therefore, diffusion experiments with dissolved gases were performed on two concrete-based barrier materials considered in the current Belgian disposal concept, by using the double through-diffusion technique for dissolved gases, which was developed in 2008 by SCK CEN. Diffusion measurements were performed with four gases including helium, neon, methane and ethane. Information on the microstructure of the materials (e.g., pore size distribution) was obtained by combining N2-adsorption, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and water sorptivity measurements. A comparison was made with data obtained from cement-based samples (intact and degraded), and the validity of existing predictive models was investigated.

Comparison of Modified Yield-Line and Punching Shear Capacities for Concrete Traffic Barriers and Bridge Rails

The traditional, triangular yield-line method used by most departments of transportation for analyzing concrete traffic barriers and bridge rails has been largely unchanged since 1978. Testing of concrete barriers since this time has indicated that the triangular yield-line method is not qualitatively representative of observed damage patterns and is overconservative. Further, the conversion from NCHRP Report 350 to the crash test criteria from the Manual for Assessing Safety Hardware (MASH) will result in increases to lateral impact loads; therefore, overconservative analysis practices may result in many concrete barriers being unnecessarily deemed inadequate. In this research, alternative analysis methods for concrete barriers were extracted from an extensive literature review of concrete barrier investigations. These methods were applied to a sample of eight concrete barriers to demonstrate and compare their effects on capacity estimates. Alternative methods included trapezoidal yield-line mechanisms, effects of impact heights lower than the top of the barrier, punching shear evaluation, and consideration of expected material strengths. Capacity estimates of the selected barriers were increased by an average of 47 percent when alternative methods were cumulatively applied. Although the traditional method does not consider punching shear, the capacity of one of the eight barriers was controlled by punching shear rather than by yield-line flexure. With the alternative methods applied, seven of the eight barriers were deemed adequate relative to the increased lateral loads corresponding to MASH criteria for Test Levels 2 through 5. By contrast, if analyzed according to the traditional method, three of the eight barriers would have been deemed insufficient considering MASH loads.

Internet of things application for smart construction assets

Internet of things (IoT) devices allow data to be communicated efficiently using low power to a central server to report location, movement, temperature and environmental attributes. With improvements in device connectivity distance, improved link margins, reductions in IoT hardware platform costs and the availability of higher-capacity batteries, non-powered temporary construction equipment (e.g. concrete barriers) can become smart and trackable. For this study, a long-range (LoRa) sensor platform is connected through an IoT low-power wide-area network (LPWAN) to test the feasibility of tracking construction equipment related to transportation. The signal strength relative to distance is analysed along with the radio-frequency signal attenuation of the signal strength through construction materials. The preliminary results show that a commercially available LoRa sensor with an omnidirectional antenna operating on an LPWAN can transmit up to 1310 m at grade. It is expected that these types of sensor platforms can be applied to other types of non-powered construction equipment to introduce smart functionalities. From the study, it was determined that it is feasible to deploy a LoRa-based sensor network to track non-powered temporary construction equipment. The study also demonstrated that a cost-effective poly(vinyl chloride) housing could be effective after 300 freeze–thaw cycles.

Safety evaluation of design alternatives to separate freeway-opposing traffic

Objectives Different design alternatives used to separate freeway-opposing traffic may produce varying safety levels. State-of-the-art design guidelines have provided guidance in respect to a number of median features such as width, slope, and barrier installation. Guidance provided has been based on benefit-cost procedures; however, because project costs may significantly vary across different countries/jurisdictions, findings from benefit-cost procedures may be meaningless on a broader geographical scope. The objective of this study is to quantify the safety level of a number of design alternatives commonly used to separate opposing freeway traffic based solely on annualized crash costs. Methods The safety performance of 14 design alternatives were assessed using the Roadside Safety Analysis Program (RSAPv3). Results A test-level 3, low-tension cable barrier installed in the middle of a wide, hazard-free median was found to be the safest design alternative. Road sections containing: i) cable barriers were found to be safer than those containing w-beam guardrails, ii) low-tension cable barriers installed in the middle of the median were found to be safer than those containing high-tension cable barriers installed on one side of the median, regardless of median width, iii) wide, hazard-free medians were found to be safer than those containing WB guardrails, and iv) concrete barrier installations were found to be only safer than those containing unshielded medians, except when the median was 20 meters wide and hazard-free. Conclusions This paper not only provides evidence that some of the design alternatives often installed in real-world scenarios are not the safest, but it also discusses how some of these alternatives may not be the most cost-effective either. These findings make this study relevant and timely, as designers and policy/decision makers should always seek to maximize safety while optimizing the allocation of limited public funds.

A reactive hydrodynamic simulation of noise propagation for a concrete-confined detonation

When a point source detonation occurs, high temperature and pressure gases are released and then propagate through the open atmosphere as a blast wave. This leads to an explosive sound in the form of environmental noise, which has been known to cause hearing damage to nearby residents surrounding the explosion area. In an effort to reduce such noise levels, explosion test sites are installed with sound barriers to mitigate and minimize the noise associated with the blasts. In this study, realistic explosion pressure was calculated at an initial detonation source inside a concrete sound barrier, and a numerical prediction was made to evaluate the environmental noise propagation in an actual terrain. In particular, we applied the concrete equation of state to the governing conservation equations for a spherical detonation in a confined geometry and compared the experimental data taken within 3 m from the test site and a few kilometers away from the sound source. Moreover, the amount of noise reduction was predicted by first considering the absorbed explosion pressure by the sound barrier, which later dissipated at a far distance at which the noise propagation in an actual terrain was compared with the measurements.

Development and Testing of a Concrete Median Barrier for Flood-Prone Areas

Concrete median barriers are designed to mitigate serious cross-median crashes by preventing penetration of errant vehicles into oncoming traffic. When implemented in flood-prone areas, however, solid concrete median barriers can act as a dam to floodwaters, as recently seen in the U.S. in Texas during Hurricane Harvey, or in Louisiana and Pennsylvania following severe storms. This raises the height of the floodwaters and increases the severity of flooding on highways and surrounding roads and communities. To reduce flooding, new median barrier options with openings were investigated. Finite element simulations were used to aid investigation and evaluation of the designs, and laboratory testing was performed to evaluate the hydraulic efficiency of barrier designs in a variety of simulated flood conditions. A concrete single-slope profile median barrier with a large scupper was selected for crash testing following Manual for Assessing Safety Hardware (MASH) Test Level 4 (TL-4) impact conditions and evaluation criteria. The median barrier design was deemed MASH compliant and is ready for implementation in areas susceptible to flooding, with the goal of reducing flooding severity, decreasing associated risk to motorists, and reducing the level of flood damage to both highways and surrounding areas.

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.

Investigating the Effect of the Geometry of RC Barrier Walls on the Blast Wave Propagation

Evaluating the performance of several types of reinforced concrete barrier walls subjected to blast loads is the target of this research paper. A parametric study is carried out for nine RC barrier wall systems with different geometries modelled in the three dimensions with different configurations and variable parameters. ANSYS Autodyn software version 18.2 is used to model and analyse these systems using three-dimensional explicit dynamics analysis. The nine systems are studied under the effect of several parameters, such as explosive charge weight (W) and the stand-off distance from the explosion source to the wall (R). Their effect on the wall damage and its deformations and the pressure-induced at different locations are analysed. Eighteen reinforced concrete barrier wall models are studied to achieve this research goal. Comparisons between the results showed the deformation performance of the 60° concave face with planar back walls and the walls with the constant base of 1.0-meter-thick up to 0.5-meter-high with a face hunch up to 2.0-meter-high are better than all other studied walls. However, the concave face-convex back wall that has 70° curvature mitigate the pressure behind the wall by 10% regardless of its deformation.

Long-Term Experiments for Demonstrating Durability of a Concrete Barrier and Gas Generation in a Low-and Intermediate-Level Waste Disposal Facility

Long-Term Experiments for Demonstrating Durability of a Concrete Barrier and Gas Generation in a Low-and Intermediate-Level Waste Disposal Facility

Negotiating change for gender equality: identifying leverages, overcoming barriers

Introduction. Institutional change through gender equality plans is today the dominant approach to promoting gender equality in higher education and research. Building on our experiences as “technical support partners” in several EU-funded projects, we reflect on how change is negotiated in a variety of contexts. Objectives. Theoretically, using Feminist Institutionalism and the Science and Technology Studies concept of the trading zone, our objective is to analyse institutional negotiations among various, differently positioned actors with diverse backgrounds, value systems and negotiating power. From a practice-oriented perspective, our aim is to demonstrate typical challenges, suggest pathways towards solutions, and identify specific negotiation skills which underscore the capacity-building needs of change agents. Methodology. For our analysis, we have selected eight information-rich case studies through purposive theory-based sampling, illustrating the different transactions in the trading zones, based on our prior knowledge of the circumstances. The methods we draw on are primarily participant observation and textual analysis of project documents. Results. The selected theoretical combination allows us to identify leverages, ways to overcome barriers and the required skills and competences. Specifically, we underscore the use of participatory and co-creation techniques, strategic framing, spotting and using windows of opportunity, and wide mobilisation of stakeholders. We highlight key features of the change process, including its processual and incremental nature, the need for constant negotiation and the capacity-building needs of change agents. Contribution. With this analysis, we contribute, firstly, to the understanding of organisational change by identifying concrete barriers and opportunities as well as considering the ways in which a shared representation of gender equality is developed. The second, theoretical contribution lies in combining Feminist Institutionalism and the concept of the trading zone, which allows us to bring to productive dialogue issues of power, processuality and the need to address both material and discursive enactments of change processes.

Assessment of the Effectiveness of Different Safety Measures at Tunnel Lay-Bys and Portals to Protect Occupants in Passenger Cars

Tunnel portals and tunnel lay-bys are hazardous spots for road users. Different infrastructure safety measures are in use, but the protection level is not known. In this study the following safety measures for reducing the injury risk are investigated: angular positioned 4 m and 8 m concrete barrier, crash cushion Alpina F1-50 and Alpina <prototype> crash cushion. A passenger car equipped with a data acquisition unit is accelerated to 100 km/h and impacts the safety measure. The assessment of the latter is based on the EN 1317 criteria, specifically the Acceleration Severity Index (ASI), Theoretical Head Impact Velocity (THIV). Further assessment criteria are related to intrusions into the passenger compartment and post-crash motion. The best result in terms of ASI and THIV was achieved by the 8 m (ASI: 1.6, THIV: 30 km/h) concrete barrier. The crash cushion Alpina <prototype> showed good results for the ASI (1.8) but the THIV (57 km/h) was less satisfactory, while the angular positioned 4 m concrete barrier (ASI: 2.9, THIV: 53 km/h) and the crash cushion Alpina F1-50 (ASI: 3.3, THIV: 74 km/h) performed worst. Even though some of the measures showed good results, no protection measure tested currently complies with all the assessment criteria used.

Performance-Based Design Framework for Concrete Barriers Subjected to Truck Collision

Abstract A validated computational model is used to investigate the response of concrete barriers subjected to impact by single-unit trucks and tractor-semitrailers with different weights and appro...

Evaluation of renewable hybrid barriers in terms of carbon emission with concrete and steel barriers

Evaluation of renewable hybrid barriers in terms of carbon emission with concrete and steel barriers

Investigating Head-On Crash Severity Involving Commercial Motor Vehicles in Kentucky

This study examines various features affecting the severity associated with commercial motor vehicle (CMV, i.e., large truck and bus) head-on collisions on Kentucky highways. Recent five-year (2015–2019) crash data and variables rarely explored before (e.g., presence of centerline rumble strips, type of passing zone, and terrain type) were collected and prepared using Google Maps. A total of 378 CMV-related head-on collisions were analyzed. The generalized ordered probit (GOP) model was employed to identify the significant factors affecting the severity level resulting from CMV head-on collisions. The model allows the coefficients to vary across the injury severity categories for reliable parameter estimations. From the preliminary investigation, rolling terrains had the highest share of severe CMV head-on crashes (62% and 71% for multilane and two-lane roadways, respectively). The presence of centerline rumble strips could reduce severe crash outcomes along multilane and two-lane facilities. The GOP model identified various significant predictors of minor and severe injuries from CMV head-on crashes. Occupants wearing seatbelt were 39.3% less likely to sustain severe head-on crash injuries. From the roadway characteristics, presence of median cable and concrete barriers could significantly reduce the probability of severe head-on crash injuries, with median cables being more effective. With regard to the driver characteristics, drug impairment and speeding increased the risk of sustaining fatal/serious injuries by 39.5% and 26.4%, respectively. Necessary safety recommendations are proposed to reduce the severity of CMV head-on-related collisions. One example is installing median cable barriers along roadway stretches with a history of head-on CMV-related crashes.

Examining Driver Injury Severity in Single-Vehicle Road Departure Crashes Involving Large Trucks

Road departure (RD) crashes are among the most severe crashes that can result in fatal or serious injuries, especially when involving large trucks. Most previous studies neglected to incorporate both roadside and median hazards into large-truck RD crash severity analysis. The objective of this study was to identify the significant factors affecting driver injury severity in single-vehicle RD crashes involving large trucks. A random-parameters ordered probit (RPOP) model was developed using extensive crash data collected on roadways in the state of Kentucky between 2015 and 2019. The RPOP model results showed that the effect of local roadways, the natural logarithm of annual average daily traffic (AADT), the presence of median concrete barriers, cable barrier-involved collisions, and dry surfaces were found to be random across the crash observations. The results also showed that older drivers, ejected drivers, and drivers trapped in their truck were more likely to sustain severe single-vehicle RD crashes. Other variables increasing the probability of driver injury severity have included rural areas, dry road surfaces, higher speed limits, single-unit truck types, principal arterials, overturning-consequences, truck fire occurrence, segments with median concrete barriers, and roadside fixed object strikes. On the other hand, wearing seatbelt, local roads and minor collectors, higher AADT, and hitting median cable barriers were associated with lower injury severities. Potential safety countermeasures from the study findings include installing median cable barriers and flattening steep roadside embankments along those roadway stretches with high history of RD large-truck-related crashes.

Enhancement of engineering models for simulation of soft, and hard projectile impact on reinforced concrete structures

Protective Reinforced Concrete (RC) barrier walls of nuclear or industrial facilities are required to withstand accidental or intentional missile impact. The missiles (projectiles) can be classified as hard, semi-hard or soft. In particular, an airplane crash on a reinforced concrete structure causes local and global damage to the structure. Local damage mechanisms are usually associated with the impact of hard aircraft components such as engine shafts and wing boxes. In the event of a hard impact, the contact actions and target reactions are strongly coupled and therefore the calculation of capacity and damage effects is very sophisticated.There are various analysis methods for modelling both, hard and soft impacts. In this regard, empirical and semi-empirical models can be considered to calculate the load-bearing capacity in a simplified way with a few input parameters. However, validated numerical Finite Element (FE) simulation models allow further investigation on damage mechanism as well as detailed evaluation of stresses and strains in concrete and reinforcement.Hence, this paper investigates the efficiency of the existing analytical approaches as well as numerical simulation methods in predicting the load-bearing capacity of rc structures under hard and soft impact loads. Moreover, a novel simplified mechanical analytical method is proposed concerning hard impact loads. The mechanical principles are based on a nonlinear two degree of freedom (TDOF) system by Schlüter (Schlüter, 1987), which was extended for applications on hard impact scenarios considering the interaction between the impacting projectile and the rc target as well as penetration process of the projectile. FE-simulations and experimental test results of recent and ongoing research projects are presented and have been used for validation purposes and investigations.

LABORATORY AND PRODUCTION TESTS OF A HYDROPHOBIC ADDITIVE FROM THE GROUP «RAMSINKS-2M» FOR CONCRETE USED FOR THE MANUFACTURE OF STATION BLOCKS AND BLOCKS OF TRANSPLANTING TUNNELS WITH HIGH WATERPROOFING

In the work, conducting experimental works and experiments on the choice of optimal ratios of PTCs 1-100 and hydrophobic material «Ramsinks-2MU», studying hydrophobicity of mixtures, recipes-solutions, research of technological properties of mixtures. Experimentally proved that the brand of concrete is not permeable reached by W12, which can not be obtained by sealing concrete. The results of laboratory tests of concrete with the addition of «Ramsinks-2m» are given. To increase the waterproofing of concrete antiltration barriers, underground structures of buildings and structures, reservoirs, etc. It is proposed to achieve high waterproofing of concrete by adding to its composition of the hydrophobic additive «Ramsinks-2MU». The use of new hydrophobic materials such as "Ramsinks-2MU" for the manufacture of concrete on the construction of the subway in Kyiv - is an exhaust direction in metrobudination. Reliable waterproofing of outflows and openings can be achieved by applying a water-retailing additive "Ramsinks-2MU" and its modifications. Technological simplificence in the introduction of the latest material is achieved by direct use of hydro-insulating works by introducing it in the appropriate ratio in traditional solutions. A method for selecting a percentage of a hydrophobic additive with cement for different classes of concrete and for specific mining-geological conditions has been developed. This technique makes it possible for the latest technologies to determine the qualitative characteristics of the hydrophobic additive offered. The use of this additive in the manufacture of concrete and solutions contributes to an increase in the elasticity of the mixture, prevents the uneven concentration of fillers, as well as prevents mixing of the mixture and increases resistance to aggressive factors. The high waterproofing of products with the additive is achieved with the corresponding concrete composition by fine schedules of hydrophobic particles. By reducing the negative impact of moisture on the design, their durability increases. Laboratory test tests showed that the introduction of a hydrophobic additive "Ramsinks-2M" significantly affects the strength of the cement stone in the hydrophobic mixtures "Ramsinks-2MU". The proposed hydrophobic materials have qualitative advantages over other similar materials, as well as cost-beneficial. They can be used when the seams of tunnel processing and stations, as well as waterproofing of monolithic concrete structures in the subway.

Experimental and numerical investigation on deflection and behavior of portable construction barrier subjected to vehicle impacts

Experimental and numerical investigations were conducted on impact performance and deflection of precast, portable concrete construction barrier, referred to as a portable concrete barrier (PCB), with a free-standing and a box-beam stiffened configuration. A 61-m long PCB system, consisting of ten 6.1-m long PCBs, was initially evaluated with two full-scale crash tests in a free-standing configuration and a box-beam stiffened configuration according to safety performance guidelines in Manual for Assessing Safety Hardware (MASH) 2016 for Test Level 3 (TL-3). Finite element models were developed using LS-DYNA and validated with these crash tests to ensure their feasibility to estimate barrier deflections and evaluate safety performance. The validated numerical models were used to conduct numerical simulations and investigate effects of concrete constitutive models and barrier length on the performance of PCB system with a box–beam stiffened configuration. Numerical results provided information on the selection and use of concrete constitutive models for evaluation of reinforced concrete barrier impact performance. Furthermore, the reduced-length analysis demonstrated that a reduction in the total system length resulted in decreased dynamic barrier deflection during impact events, as the ends of each system were pinned. This reduced-length analysis provided useful guideline on PCB system design and application for traffic control plan.

Finite element modelling of a truck crashing into a new form of mobile vehicle blocker

In the last years, a new form of terrorist attack has sowed panic in western countries: vehicles have been run into crowded places injuring and killing many people. The first solution to preventing the vehicle ramming attack has been the placement of concrete barriers around areas that are potential terrorist targets. The performance of these systems is questionable and the design of new, effective and good-looking protection devices is a hot topic. The authors have already presented a new certified mobile barrier, which is able to stop a 3500 kg vehicle run at 64 km/h in a few meters thank to its high deformability and the adoption of water as a filler. The water flows out and removes an appreciable amount of the impact energy. In this paper, the crashes of a 7500 kg truck running at 64 km/h against a concrete block and a single barrier designed by the authors are analysed with the help of finite element (FE) calculations in Abaqus Explicit. The water in the barrier is modelled using Smooth Particle Hydrodynamics (SPH). Due to the complexity of the truck modelling, a very simplified geometry is adopted, which is a consequence of the different versions tested. According to the results, compared to the concrete blocks, the designed barrier is overall more effective, even in a single configuration.

The Social Life of a Barrier: A Material Ethnography of Urban Counter-terrorism

In the aftermath of the truck attacks in Berlin, Nice, Paris, and Stockholm, new counter-terrorism measures are being installed in European city centers. Through an ethnographic approach, this article explores the socio-material effects triggered by the most conspicuous material responses to hostile vehicle treats: concrete barriers. We draw on the recent turn towards mobilities design thinking to address the béton barriers as more-than physical obstructions, but designed artefacts negotiated and re-appropriated in unexpected ways. Set in the context of Copenhagen, we explore how the concrete barriers reveal the social, cultural, and practical conditions of the city. By establishing a critical mobilities design-oriented understanding of counter-terrorism “in situ,” we seek to broaden out what the process of “designing out terrorism” entails and to discuss new participatory design processes for future transformations of the city in light of terrorism threats.