Portable Concrete Barrier Research Articles

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.

Development of a New Manual for Assessing Safety Hardware TL-3 Low-Profile Portable Concrete Barrier for High-Speed Applications

A sight-distance problem is associated with use of 32-in. tall concrete longitudinal barriers, specifically in certain work zone locations and at nighttime. These 32-in. tall barriers can obstruct drivers’ eyesight, making it difficult for drivers to detect oncoming vehicles on the other side of these barriers. To address this sight-distance problem while protecting the errant vehicles, researchers at the Texas Transportation Institute (TTI) developed a 20-in. tall low-profile portable concrete barrier (PCB) for use in low-speed work zones in the early 1990s. To address the problem for high-speed application, TTI researchers applied modifications to the 20-in. tall low-profile PCB. Researchers designed two retrofit metal rail systems to be added on top of the existing 20-in. tall low-profile PCB to address roadside and median applications. The systems successfully performed in full-scale crash testing according to NCHRP Report 350 Test Level (TL) 3 evaluation criteria. This paper describes the efforts to develop and evaluate the crashworthiness of a new low-profile PCB design for high-speed applications. The crash tests were performed following Manual for Assessing Safety Hardware (MASH) guidelines and evaluation criteria. Based on results from finite element computer simulations performed to aid design, MASH full-scale crash tests were conducted on a low-profile PCB system comprised of 26-in. tall, 30-ft long barrier segments, with a T-shaped profile. Based on constructability feedback, the sides of the barrier were formed with a negative 1:18 slope, which allows for ease of construction forming. The new low-profile PCB performed acceptably as a MASH TL-3 longitudinal barrier.

Development of retrofit, low-deflection portable concrete barrier system

ABSTRACTA retrofit stiffening mechanism was developed for use in reducing the deflection of an F-shape portable concrete barrier (PCB) system without requiring anchorage of the barrier segments to the road surface. The research effort included development and analysis of mechanisms for limiting deflections through engineering analysis and finite element analysis with LS-DYNA. Deflection-limiting mechanisms investigated included increased barrier mass, increased barrier-to-ground friction, reduction of the joint gap, and composite action. Following analysis of the candidate designs, an initial prototype design was developed based on using composite action to provide moment continuity across the barrier joints. This design was successfully evaluated in full-scale crash tests. Following the first crash test, the low-deflection PCB system was modified to further reduce deflections and full-scale crash tested a second time. The final version of the low-deflection PCB system was capable of reducing dynamic barrier deflections almost 50% over free-standing PCB installations while still safely redirecting errant vehicles.

Simulation assessment and theoretical verification of a new design for portable concrete barriers

This paper presents a new portable concrete barrier (NPCB) design that can be placed in areas where vehicles may not enter. The proposed design is fabricated with a new shape, composed of three parts, and equipped with an interlocking connection between adjacent concrete barriers. LS-DYNA computer simulation was performed to assess whether the NPCB is in accordance with the roadside design criteria. The results showed that the new model can effectively contain and redirect collided vehicles as well as lessen the damage of vehicles. The results demonstrated little lateral deflection, which can facilitate an easy bonding between the NPCB and the floor. The occupant compartment did not penetrate, thereby keeping the driver and tenants safe during an accident. Comparison of the NPCB simulation, theoretical and the full-scale test results revealed that the simulation model is accurate and is well within the specification requirements.

Assessment of the impact speed and angle conditions for the EN1317 barrier tests

ABSTRACTRoadside safety barriers designs are tested with passenger cars in Europe using standard EN1317 in which the impact angle for normal, high and very high containment level tests is 20°. In comparison to EN1317, the US standard MASH has higher impact angles for cars and pickups (25°) and different vehicle masses. Studies in Europe (RISER) and the US have shown values for the 90th percentile impact angle of 30°–34°. Thus, the limited evidence available suggests that the 20° angle applied in EN 1317 may be too low.The first goal of this paper is to use the US NCHRP database (Project NCHRP 17–22) to assess the distribution of impact angle and collision speed in recent ROR accidents. Second, based on the findings of the statistical analysis and on analysis of impact angles and speeds in the literature, an LS-DYNA finite element analysis was carried out to evaluate the normal containment level of concrete barriers in non-standard collisions. The FE model was validated against a crash test of a portable concrete barrier carried out at the UK Transport Research Laboratory (TRL).The accident data analysis for run-off road accidents indicates that a substantial proportion of accidents have an impact angle in excess of 20°. The baseline LS-DYNA model showed good comparison with experimental acceleration severity index (ASI) data and the parametric analysis indicates a very significant influence of impact angle on ASI. Accordingly, a review of European run-off road accidents and the configuration of EN 1317 should be performed.

Traffic Barriers under Vehicular Impact: From Computer Simulation to Design Guidelines

Abstract: In this study, the problem of vehicular impact on a portable concrete barrier (PCB) is investigated. An available crash test is modeled and the impact response was simulated through a finite element (FE) model. On the basis of insight gained through this detailed FE analysis, a simpler rigid body model is then used to perform a comprehensive study of the barrier response under vehicular impact. The results from FE simulation and the rigid body model are found to be consistent with each other and in good agreement with the full‐scale crash test. On the basis of results from a series of simpler analyses, a set of charts for assessing the barrier displacement and related variables are developed for the purpose of design.

Development of a 30,000 kg heavy goods vehicle for LS-DYNA applications

In this paper, a finite element model of a 30,000 kg Heavy Goods Vehicle (HGV) was developed and validated against full-scale crash test data. Since this vehicle is a standard test vehicle in the European crash test standards, EN1317, development of an accurate vehicle model was deemed to be a positive contribution to the evaluation of roadside safety hardware. The vehicle model reproduces a FIAT-IVECO F180 truck, a vehicle with four axles and a mass of 30,000 kg when fully loaded. The model consisted of 12,337 elements and 11,470 nodes and was built for and is ready to use with LS-DYNA finite element code from Livermore Software Technology Corporation. Data available from two previously performed full-scale crash tests, one on a steel bridge rail and the other on a portable concrete barrier, were used to validate the accuracy of the HGV model. Results of the finite element simulation study show that the developed HGV model shows promise and can accurately replicate the behaviour of an actual HGV in a full-scale crash test. Improvements such as the steering mechanism in the front axles and the suspension system are currently underway to make the model more realistic.

Validation of a Single Unit Truck model for roadside hardware impact

The objective of this research is to validate the Finite Element (FE) model of a Ford F800 Single Unit Truck (SUT). The FE model of the SUT was developed at the FHWA/NHTSA National Crash Analysis Centre (NCAC) at the George Washington University (GWU). In this study, the characteristics of the SUT model were investigated and several modifications were incorporated in the model to accurately simulate its interaction with roadside safety hardware. A full-scale crash test of the Ford F800 SUT impacting an F-shape Portable Concrete Barrier (PCB) was conducted at The Federal HighWay Administration's (FHWA) Federal Outdoor Impact Laboratory (FOIL) and used in the validation. The response of any vehicle impacting a PCB is primarily governed by the mass and suspension characteristics of the vehicle. Detailed methods for modelling the truck's suspension components are discussed.

Finite-Element Crash Test Simulation of New York Portable Concrete Barrier with I-Shaped Connector

Use of finite-element simulations in designing and analyzing roadside hardware has increased significantly over the past decade. Due to considerable progress in computer technology in conjunction with nonlinear finite-element software, outcome of complex vehicle-roadside hardware collisions can be accurately predicted using simulation programs. In this paper, the finite-element simulation program LS-DYNA was used to analyze and improve the crash test behavior of New York Department of Transportation Portable Concrete Barrier (NYPCB). A full-scale crash test demonstrated that the current NYPCB design was unable to meet national standards. Inspections after the test revealed that the welding at metal connectors forming the joint between the barrier segments was not properly fabricated. A finite-element representation of the crash-tested barrier was developed with a special fillet weld with failure model and subjected to crash testing using the nonlinear finite-element code LS-DYNA. This baseline model simulation was intended to replicate the failed crash test and validate the fidelity of the finite-element models. Qualitative and quantitative comparisons show that the baseline model simulation was successful in replicating the failed crash test. Upon validation, an improved NYPCB model was developed by using proper welding details and subjected to full-scale impact simulation to determine whether this design would satisfy the crash testing requirements. Results of the simulation were encouraging. It was predicted that the barrier would successfully contain and redirect the impacting vehicle in a stable manner. Subsequent full-scale crash testing on the NYPCB with proper welding details passed the NCHRP Report 350 requirements and substantiated LS-DYNA predictions.

Low-Deflection Portable Concrete Barrier

Temporary barriers are often required to provide positive protection for motorists and workers in a highway work zone. Most highway work zones are restricted in regard to available lateral space for accommodating traffic and the work activity. Consequently, it is desirable to minimize deflection of work zone barriers to minimize the required buffer distance between the barrier and work activity area and, thereby, maximize the space and number of lanes available for traffic. Under this study, a new connection designed to reduce dynamic deflection of portable concrete traffic barriers was developed through a program of finite element simulation and full-scale crash testing. The new cross-bolted (or X-bolt) connection uses two threaded rods in different horizontal planes across the barrier joint to form a tight, moment connection. It achieves the objective of low dynamic barrier design deflection without sacrificing constructability. In addition to being easy to install, the new barrier system is also perceived to be easy to inspect and repair. Crashworthiness and design deflection of the barrier connection were verified through full-scale crash testing using segment lengths of 10 ft and 30 ft. An F-shape barrier with X-bolt connection was demonstrated to have the lowest deflection of any approved portable concrete barrier.

Low-Deflection Portable Concrete Barrier

Temporary barriers are often required to provide positive protection for motorists and workers in a highway work zone. Most highway work zones are restricted in regard to available lateral space for accommodating traffic and the work activity. Consequently, it is desirable to minimize deflection of work zone barriers to minimize the required buffer distance between the barrier and work activity area and, thereby, maximize the space and number of lanes available for traffic. Under this study, a new connection designed to reduce dynamic deflection of portable concrete traffic barriers was developed through a program of finite element simulation and full-scale crash testing. The new cross-bolted (or X-bolt) connection uses two threaded rods in different horizontal planes across the barrier joint to form a tight, moment connection. It achieves the objective of low dynamic barrier design deflection without sacrificing constructability. In addition to being easy to install, the new barrier system is also perceived to be easy to inspect and repair. Crashworthiness and design deflection of the barrier connection were verified through full-scale crash testing using segment lengths of 10 ft and 30 ft. An F-shape barrier with X-bolt connection was demonstrated to have the lowest deflection of any approved portable concrete barrier.

Improvement of Portable Concrete Barrier Design Using Computational Mechanics

Concrete safety barriers have been employed broadly in Italy since the 1980s, particularly on highways and freeways. Safety barrier homologation and design standards have not yet precisely determined specific fields of application or modality of installation, in particular for concrete barriers. Such barriers have sometimes been judged too rigid and, therefore, inadequate to pass crash tests conducted with lightweight vehicles. No changes have been made nor have new designs (crosssection shape and size) been developed in the past 20 years. For all those reasons, the possibility of achieving better overall performance with concrete barriers has been investigated (containment of heavy vehicles and lower accelerations on occupants of lightweight vehicles). One design proposal for these modular systems is to use lightweight concrete and make the element shorter than the one that is usually adopted in Italy. In that way, the higher lateral deformability of the barrier could lead to a greater dissipation of ene...

Improvement of Portable Concrete Barrier Design Using Computational Mechanics

Concrete safety barriers have been employed broadly in Italy since the 1980s, particularly on highways and freeways. Safety barrier homologation and design standards have not yet precisely determined specific fields of application or modality of installation, in particular for concrete barriers. Such barriers have sometimes been judged too rigid and, therefore, inadequate to pass crash tests conducted with lightweight vehicles. No changes have been made nor have new designs (cross-section shape and size) been developed in the past 20 years. For all those reasons, the possibility of achieving better overall performance with concrete barriers has been investigated (containment of heavy vehicles and lower accelerations on occupants of lightweight vehicles). One design proposal for these modular systems is to use lightweight concrete and make the element shorter than the one that is usually adopted in Italy. In that way, the higher lateral deformability of the barrier could lead to a greater dissipation of energy, with a resulting decrease in the dynamic effects for users, maintaining a good containment capability in the high-energy crash tests. In this paper, this new design is evaluated with virtual crash tests carried out with LS-DYNA, a finite element code. The model has been previously validated by comparing results of an actual crash test (using the existing Italian concrete barrier design) with the virtual crash test performed under the same conditions.

Impact simulation and full scale crash testing of a low profile concrete work zone barrier

The development of a new low profile portable concrete barrier system for use in roadside work zone environments is presented. By making extensive use of non-linear dynamic finite element impact simulation, several cycles of concept refinement were carried out using simulation rather than expensive full scale crash testing. Issues such as ensuring stable vehicle redirection during impact, properly accounting for frictional effects (and associated energy dissipation), and monitoring system energy parameters are discussed together with corresponding example simulations. Results obtained from full scale crash testing of the barrier validate the simulation methodology and demonstrate successful barrier performance.