As a key roadside safety feature, longitudinal guardrail steel barriers are purposefully designed to contain and redirect errant vehicles to prevent roadway departure, dissipate impact energy through plastic deformation, and reduce the severity of vehicle crashes. Nevertheless, these systems should be carefully designed and assessed, as localized rupturing, especially near splice or impact locations, can lead to catastrophic failures, compromising vehicle containment, violating crash safety standards, and ultimately jeopardizing the safety of occupants and other road users. Before conducting full-scale crash testing, finite element analysis (FEA) tools are widely employed to evaluate the design efficiency, optimize system configurations, and preemptively identify potential failure modes prior to expensive physical crash testing. To accurately assess system behavior, calibrated material models and precise failure criteria must be utilized in these simulations. Despite the existence of numerous failure criteria and material models, the material characteristics of AASHTO M-180 guardrail steel have not been fully investigated. This paper significantly advances the FE modeling of ductile fracture in guardrail steel, addressing a critical need within the roadside safety community. This study formulates stress-state-dependent failure criteria and proposes advanced material modeling techniques. Extensive experimental testing was conducted on steel specimens having various triaxiality and Lode parameter values to reproduce a wide spectrum of complex, three-dimensional stress-state loading conditions. The test results were then used to identify material properties and construct a failure surface. Subsequent FEA, which incorporated the Generalized Incremental Stress-State-Dependent Damage Model (GISSMO) in conjunction with two LS-DYNA material models, illustrates the capability of the developed surface and material input parameters to predict material behavior under various stress states accurately. A parametric study was completed to further validate the proposed models, highlighting their robustness and reliability.

Guardrails, consisting of soil-embedded piles tied with a rail, are safety barriers that are installed along highways to shield errant motorists from roadside hazards and to minimize the risk of serious injuries. Soil resistance plays a crucial role in the way that guardrails perform when impacted by vehicles. Although the consequences of guardrail system failures are tragic, little is known on the dynamic impact characteristics of soil and soil-pile interaction under impact loading. Thus, research was conducted to investigate the load-deflection behavior of a single pile under impact through dynamic large-scale component testing and numerical simulation using LS-DYNA. Baseline dynamic tests were performed on a steel W6x16 pile embedded in crushed limestone soil impacted by a surrogate bogie vehicle. Test results were used to develop a simplified numerical model of soil-pile system when impacted by a vehicle. The validated model was then compared to full-scale crash test data. The proposed soil modeling method accurately represented soil and pile behavior in component tests and full-scale vehicle crash tests.

The objective of this research was to design a transition from temporary concrete barriers to a permanent concrete barrier for median applications. The researchers at Midwest Roadside Safety Facility utilized a combination of free-standing and tied-down Kansas temporary concrete barriers and a dual-nested thrie beam for the transition to the single-slope permanent barrier as well as a transition cap. Two full-scale vehicle crash tests were performed on the system. Evaluation of the approach transition required testing at two Critical Impact Point (CIP) locations. The first tests was performed using a half-ton pickup truck that impacted the temporary barriers 1,432 mm upstream from the permanent barrier, at a speed and angle of 100.7 km/h and 24.7 degrees, respectively. The second crash test was also performed using a half-ton truck that impacted the temporary barriers 16.6 m upstream from the permanent barrier, at a speed and angle of 100.1 km/h and 26.2 degrees, respectively. Both tests were conducted and reported in accordance with requirements specified in the Manual for Assessing Safety Hardware (MASH) and were determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria.

The research study described herein developed an economical method for terminating and anchoring the upstream end of temporary concrete barrier systems. The termination and anchorage system was designed for use with the Kansas F-shape temporary concrete barrier design that is currently used by several states participating in the Midwest Pooled Fund Program. These efforts were performed in accordance with the Test Level 3 guidelines found in the Manual for Assessing Safety Hardware 2008. Criteria governing the design of the termination and anchorage system included development of adequate anchor loads over a finite deflection in order to limit peak loads, mitigation of vertical rotation and tipping of the end barrier about its longitudinal axis, and employing existing roadside safety hardware in the design to limit state hardware inventories. The termination and anchorage system allowed for a significant reduction in the number of barrier segments required upstream from the length of need and for use in anchoring a free-standing TCB system. The anchorage system was configured to effectively constrain the end of the TCB system for impacts as far upstream as the first anchored barrier segment. Full-scale crash testing demonstrated that the impacting vehicle was safely and smoothly redirected, and the test was judged acceptable according to the Test Level 3 safety criteria set forth in the Manual for Assessing Safety Hardware 2008.