Strategies and challenges to facilitate situated learning in virtual worlds post-Second Life

Virtual worlds can establish a stimulating environment to support a situated learning approach in which students simulate a task within a safe environment. While in previous years Second Life played a major role in providing such a virtual environment, there are now more and more alternative—often OpenSim-based—solutions deployed within the educational community. By drawing parallels to social networks, we discuss two aspects: how to link individually hosted virtual worlds together in order to implement context for immersion and how to identify and avoid “fake” avatars so people behind these avatars can be held accountable for their actions

Phase II Evaluation of Floor Pan Tearing for Cable Barrier Systems

The objective of this research effort was to mitigate the potential for floor pan tearing and penetration into the occupant compartment by modifying the posts utilized in a prototype cable barrier system. A series of dynamic component tests were conducted on the modified Midwest Weak Post (MWP). A bogie vehicle was equipped with a simulated floor pan designed to replicate the height, thickness, and strength of the floor pan of a Kia Rio. Two methods of post modification were investigated, including edge protection on the top of the MWP as well as weakening of the MWP at the ground line. Two methods of edge protection were tested, including a 31⁄2-in. x 21⁄2-in. x 3/16-in. (89-mm x 64-mm x 5-mm) thick steel tube cap and 21⁄8-in. x 13⁄8-in. x 7-gauge (54-mm x 35-mm x 5-mm) bent steel plates. Weakening of the MWPs was accomplished through two 3⁄4-in. (19-mm) diameter holes drilled through the weak-axis of the posts at the ground line. Both methods of edge protection showed potential for mitigating the propensity for floor pan tearing. In all but one test, the posts caused creasing on the simulated floor pan. In one test, test no. MWPFP-23, the edge protector connection bolt sheared and allowed the posts’ free edges to contact and tear the simulated floor pan, which would not be expected in full-scale crash testing with the 1100C vehicle. The bogie testing of MWPs with 3⁄4-in. (19-mm) diameter weakening holes with steel plate edge protectors mounted at the top of the posts resulted in only minor creasing on the simulated floor pan. Thus, a combination of weakening holes and edge protectors using steel bent plates at top of the MWP was recommended for further evaluation through full-scale vehicle crash testing

Evaluation of Floorpan Tearing and Cable Splices for Cable Barrier Systems

This research effort consisted of two objectives related to components of a prototype cable barrier system. The first objective was to mitigate the potential for vehicle floorpan tearing by modifying the cable guardrail posts. A bogie vehicle was equipped with a simulated floorpan designed to replicate the height, thickness, and strength of the floorpan of a Kia Rio vehicle. Baseline testing demonstrated that the top of the Midwest Weak Post (MWP) would contact, and crease the simulated floorpan, which matched the damage observed in actual full-scale vehicle crash tests. Once the test setup provided the desired results, various post configurations were tested including S3x5.7 (S76x8.4) posts, MWPs with edge rounding, MWPs with steel plate edge protectors, and MWPs with weakening holes/slots. Three different weakening patterns were evaluated: ¾-in. (19-mm) diameter hole; three ⅜-in. (10-mm) diameter holes; and ⅜-in. x 1⅛-in. (10-mm x 29-mm) slots. All three weakening patterns showed the ability to reduce the propensity for floorpan tearing. However, additional bogie testing of the posts resulted in significant reductions in strong-axis strength for the latter two weakening patterns. The ¾-in. (19-mm) diameter hole resulted in a 10 percent reduction in strong-axis bending strength, and thus, was recommended for further evaluation through full-scale vehicle crash testing. The second objective was to investigate the structural capacity of other cable splice hardware that would reduce the propensity for vehicle snag and sheet metal tearing. A review of existing hardware was conducted to identify possible couplers. Next, three component tests were conducted to evaluate two models of Bennett Bolt Works mechanical couplers. Test results for the new coupler, model no. CGBBWTH, showed promise, however the targeted failure strength of 39 kips (174 kN) was not satisfied for either the new coupler, model no. CGBBWTH, or current coupler, model no. CGBBHT. There is potential that the couplers used in test no. BBNC-3 sustained damage in previous testing which would make them susceptible to premature failure, therefore further testing and evaluation of both coupler models will be necessary to gain a better understanding of their strengths and durability

MASH Test No. 3-10 of a Non-Proprietary, High-Tension, Cable Median Barrier for Use in 6H:1V V-Ditch (Test No. MWP-9)

The Midwest Pooled Fund Program has been developing a prototype design for a non-proprietary, high-tension, cable median barrier for use in a 6H:1V median V-ditch. This system incorporates four evenly spaced cables, Midwest Weak Posts (MWPs) spaced at 8 to 16 ft (2.4 to 4.9 m) intervals, and a bolted, tabbed bracket to attach the cables to each post. Full-scale crash testing was needed to evaluate the barrier’s safety performance. According to the Manual for Assessing Safety Hardware 2016 (MASH) testing matrix for cable barriers installed within a 6H:1V median V-ditch, a series of eight full-scale crash tests are required to evaluate the safety performance of a system. Several previous tests have failed due to the posts penetrating into the occupant compartment. In order to mitigate the floor pan tearing, a modified MWP was designed. Test no. MWP-9 was conducted on the modified barrier system, consisting of MWPs with 3⁄4-in. (19-mm) diameter weakening holes at the ground line. Additionally, a two-part cap with a single retainer bolt was added to the top of the posts. The cap shielded the free edges of the MWPs during the post-to-vehicle contact. This test was conducted according to MASH 2016 test designation no. 3-10 and utilized an 1100C small car impacting the barrier on level terrain. The vehicle was contained by the system. The two-piece cap mitigated the floor pan tearing. However, one cable (cable no. 3) snagged on the cap retainer bolt and caused two cables (cable nos. 3 and 4) to become interlocked with the left-side A-pillar on the impact side of the vehicle, which resulted in excessive A-pillar crush. Therefore, test no. MWP-9 was deemed unacceptable. However, the two-part cap demonstrated that a closed-section post should be capable of mitigating floor pan tearing

DEVELOPMENT AND EVALUATION OF A TIE-DOWN SYSTEM FOR THE REDESIGNED F-SHAPE CONCRETE TEMPORARY BARRIER

Often, temporary barriers are used in applications where it is desired that their deflection during vehicular impact be limited. One such application is in the installation of temporary barriers placed adjacent to the edge of a concrete bridge deck in order to maximize lane width. Acceptable tie-down systems for temporary barriers have previously been developed, but there are concerns when the barriers and tie-down systems are used on bridges that are reconstructed in stages and where very little tolerance in barrier deflection is allowable. Therefore, a rigid tie-down system was developed that minimizes barrier deflections. For this system, the original Kansas temporary barrier was redesigned in order to strengthen the barrier around the tie-down holes and to standardize the barriers for use in adjacent states and in various temporary and tied-down configurations. The tie-down anchor system fastened the traffic-side of the barriers to the concrete bridge deck with three 29-mm (1.125-in.) diameter ASTM A307 anchor bolts with heavy hex nuts and 76-mm (3-in.) x 76-mm (3-in.) x 13-mm (0.5-in.) thick washers. The research study included one full-scale vehicle crash test, using a 3⁄4-ton pickup truck. The full-scale test, with an impact speed of 99.8 km/hr (62.0 mph) and an impact angle of 25.3 degrees, was conducted and reported in accordance with the requirements specified in the National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. The safety performance of the tie-down anchor system for use with concrete bridge decks and the redesigned F-shape temporary concrete barrier was determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria specified in NCHRP Report No. 350

BARRIER SYSTEM

A barrier system (100) includes first and second barrier segments (102) connected to one another such that crash energy is absorbed. The connection between the segments includes a pair of wedge-shaped connectors (102) disposed between angled faces (118) formed at the opposing ends of the segments. Elastic pads (700) are sandwiched between the respective segment faces and connectors (202)