Improved Models of Cable-to-Post Attachments for High-Tension Cable Barriers

Computer simulation models were developed to analyze and evaluate a new cable-to-post attachment for high-tension cable barriers. The models replicated the performance of a keyway bolt currently used in the design of a high-tension cable median barrier being developed at the Midwest Roadside Safety Facility. Component tests of the keyway bolts were simulated and compared to the component test results. Accurate friction, fracture strain, and stress-strain material properties were determined for a solid element model of the keyway bolt by applying actual load curve measured from the test to a simulated pull cable. By simulating the material properties of the solid element keyway bolt in bending, torsion, and tension of a rod, load curves were developed for a simplified beam element model of the keyway bolt as well. When material properties were finalized, the solid and beam element models of the keyway bolt were inserted in bogie test models and simulated again. By analyzing the bogie testing results, it was determined that due to the very small size of the keyway bolt and potential contact difficulties, solid element models of the keyway bolt may be impractical for full-scale simulation purposes. However, the beam element models were determined to be advantageous and had a very small computational cost in comparison

Dynamic strength of a modified W-beam BCT trailing-end termination system

W-beam systems utilize end-terminal anchorages to develop tension upstream and downstream of an impact event. However, the capacities of the anchorage components under impact loading are not well known. One such W-beam end anchorage system, the Midwest guardrail system (MGS) trailing-end anchorage, was evaluated using three dynamic component tests _ a soil foundation tube pull test, a breakaway cable terminal (BCT) post splitting test, and an MGS end anchorage system pull test. The peak load recorded during a soil foundation tube test was 193 kN at 56 mm deflection, as measured at the ground line. BCT posts split at loads of 17.8 and 32.9 kN. The end-anchorage tensile capacity was 156 kN, dissipating 64.7 kJ. Results from the component tests were also used to create and validate nonlinear finite element models of the components in order to be used for future design and analysis of end anchorages

Cable Median Barrier Failure Analysis and Remediation Phase II

Cable median barrier crashes from a total of 12 states were analyzed. Crash data included scene diagrams, photographs, and field measurements, crash narratives, although the availability of data in each crash varied. Major contributors to penetration crash propensity were identified: diving underride, in which the front end of the vehicle dropped below the bottom cable; prying, in which the vehicle profile caused cable separation or lifting; override; bouncing override, in which the vehicle rebounded after contact with the back slope and bounced over the top of the barrier; system failure, in which one component failure or design failure prevented the cables from adequately engaging the vehicle; and large vehicle crashes, such as tractor trailers, buses, and single-unit trucks into TL-3 systems. Major contributors to rollover were identified: steep median slopes, in which the slope caused unstable bouncing or abrupt changes in slope profiles acted as trip points for the tires; broadside skid, in which the vehicle was skidding with a sideslip angle of nearly 90 degrees prior to contact with the barrier; contact with post, in which the post acted as a trip point; and other factors such as towing trailer units, median anomalies, or with large vehicles such as tractor-trailers, buses, or motor homes. Recommended improvements to cable median barrier systems included: minimum top cable height of 35 in. (890 mm); maximum top cable height of 15 in. (381 mm); minimum of 4 cables supported by posts; higher lateral cable-to-post attachment strength at bottom and lower strength at top; low strong-axis strength post sections; and to eliminate cable entrapment in a vertical slot in the post when initial cable contact occurs at a post location. A summary of factors and how they contributed to penetration, rollover, and severe crash probability is shown in Table 1

DYNAMIC EVALUATION OF A PINNED ANCHORING SYSTEM FOR NEW YORK STATE’S TEMPORARY CONCRETE BARRIERS

Temporary concrete barrier (TCB) systems are utilized in many circumstances, including for placement adjacent to vertical dropoffs. Free-standing TCB systems are known to have relatively large deflections when impacted, which may be undesirable when dealing with limited space behind the barrier (as seen on a bridge deck) or limited lane width in front of the barrier system. In order to allow TCB systems to be used in space-restricted locations, a variety of TCB stiffening options have been tested, including beam stiffening and pinning the barriers to the pavement. These pavement-pinning procedures have been considered time-consuming and may pose undue risk to work-zone personnel who are anchoring the barrier on the traffic-side face. Thus, a means of reducing TCB deflections while reducing risk to workers was deemed necessary. The primary research objective was to evaluate the potential for pinning alternate barrier sections on the back-side toe of the New York State’s New Jersey-shape TCBs and evaluate the barrier system according to the Test Level 3 (TL-3) criteria set forth in MASH. The research study included one 2270P full-scale vehicle crash test with a Dodge Quad Cab pickup truck. Four 151⁄2-in. (394-mm) long, vertical steel pins were placed through holes on the back-side toe of alternating barrier sections and inserted into drilled holes within the rigid concrete surface. Following the successful redirection of the pickup truck, the safety performance of the pinned anchoring system was determined to be acceptable according to the TL-3 evaluation criteria specified in MASH using the 2270P vehicle. However, it should be noted that significant barrier deflections were observed during the crash test and may be greater than those desired for work areas with restricted space