Fracture of Protective Structures from Heavy Reinforcing Cement During Interaction with High-velocity Impactor

In this work, the fracture of a reinforced concrete barrier made of heavy reinforced ce- ment is numerically simulated during normal interaction with a high-velocity titanium projectile. The projectile has the initial velocity 750 m/s. The problem of impact interaction is numerically solved by the finite element method in a three-dimensional formulation within a phenomenological framework of solid mechanics. Numerical modeling is carried out using an original EFES 2.0 software, which al- lows a straightforward parallelization of the numerical algorithm. Fracture of concrete is described by the Johnson-Holmquist model that includes the strain rate dependence of the compressive and tensile strengths of concrete. The computational algorithm takes into account the formation of discontinuities in the material and the fragmentation of bodies with the formation of new contact and free surfaces. The behavior of the projectile material is described by an elastoplastic medium. The limiting value of the plastic strain intensity is taken as a local fracture criterion for the projectile material. A detailed numerical analysis was performed to study the stress and strain dynamics of the reinforced concrete target and the effect of shock-wave processes on its fracture. The influence of reinforcement on the resistance of a heavy cement target to the penetration of a projectile has been investigated

Usage of pedestrian overpass in Akure, Nigeria

Background This study addressed the safety challenge, motivation, and utilization factors regarding the usage of the pedestrian overpass by different people of dissimilar ages alongside Oba Adeshida road at Oja-Oba (Oba market) in Akure, Ondo State, Nigeria. It addressed the following objectives: determined the value of the pedestrian overpass as used by people of different ages; examined the reasons for using the pedestrian overpass in Akure; and examined the performance level of a pedestrian overpass in Akure. Methods In total, 384 users (who used the bridge) were purposively sampled for questionnaire administration, but 324 users participated in the questionnaire, which included multiple-choice and open-ended questions. Also, personal observation was employed for queue analysis. The “Semantic Differential Scale” and single-server queue system for the single queue were employed for data analysis. Conclusions In Akure, there was low or no usage of the pedestrian overpass when the road median was made use of metal and low concrete; but when the road median was made use of high concrete barrier, there was high usage of the pedestrian overpass. It also revealed that the engineering design of the pedestrian overpass is low compared to the contemporary design solutions in addressing the urban societal needs. The pedestrian overpass was used frequently and every day because it provides access to the car park, market, and central mosque. The performance of the pedestrian overpass in Akure is 105% which indicates that the pedestrian overpass is over-utilized by a pedestrian. It is recommended that there is a need to construct another pedestrian overpass to enhance the efficiency of the structure. The existing and future pedestrian overpass should be redesigned to constitute interesting aesthetics and architectural solutions that could harmonize with the environment and enhance flow of the disabled persons.

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.

Environmental And Age-Related Deterioration Of Concrete Median Barriers

The purpose of this research was to understand the time-dependent environmental and age-related deterioration mechanisms in the un-reinforced concrete barrier walls used in Ontario. The study concentrated mainly on the response of plain concrete barrier walls to time-dependent thermal loads and associated volume changes. The research involved temperature data collection, experimental study and numerical analysis. The temperature data was collected on an hourly basis from the temperature sensors installed in a live plain concrete barrier wall. In the experimental study, concrete samples were exposed to varying temperature and environmental conditions and tested to monitor the deviation of significant concrete parameters like compressive strength, tensile strength, modulus of elasticity etc. Based on the results from the experimental study and the temperature data collected from the sensors, a non-linear transient thermal and structural analysis was carried out on a three-dimensional model, developed using ANSYS program, for a time period of three years.

Environmental And Age-Related Deterioration Of Concrete Median Barriers

The purpose of this research was to understand the time-dependent environmental and age-related deterioration mechanisms in the un-reinforced concrete barrier walls used in Ontario. The study concentrated mainly on the response of plain concrete barrier walls to time-dependent thermal loads and associated volume changes. The research involved temperature data collection, experimental study and numerical analysis. The temperature data was collected on an hourly basis from the temperature sensors installed in a live plain concrete barrier wall. In the experimental study, concrete samples were exposed to varying temperature and environmental conditions and tested to monitor the deviation of significant concrete parameters like compressive strength, tensile strength, modulus of elasticity etc. Based on the results from the experimental study and the temperature data collected from the sensors, a non-linear transient thermal and structural analysis was carried out on a three-dimensional model, developed using ANSYS program, for a time period of three years.

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.