Evaluation of the Midwest Guardrail System stiffness transition with curb

A W-beam to thrie beam stiffness transition with a 102-mm (4- in.) tall concrete curb was developed to connect 787-mm (31-in.) tall W-beam guardrail, commonly known as the Midwest Guardrail System (MGS), to a previously developed thrie beam approach guardrail transition system. This upstream stiffness transition was configured with standard steel posts that are commonly used by several state departments of transportation. The toe of a 102-mm (4-in.) tall sloped concrete curb was placed flush with the backside face of the guardrail and extended the length of the transition region. Three full-scale crash tests were conducted according to the Test Level 3 (TL-3) safety standards provided in AASHTO’s Manual for Assessing Safety Hardware (MASH). The first test, MASH Test No. 3-20, was deemed a failure due to guardrail rupture. The stiffness transition was modified to include an additional nested W-beam rail segment upstream from the W-beam to thrie beam transition element. MASH Test No. 3-20 was repeated on the modified system, and the 1100C small car was successfully contained and redirected. During MASH Test No. 3-21, a 2270P pickup truck was successfully contained and redirected. Following the crash testing program, the system was deemed acceptable according to the TL-3 safety performance criteria specified in MASH

Development and Evaluation of Weak-Post W-Beam Guardrail in Mow Strips

The objective of this study was to adapt and evaluate a weak-post, W-beam guardrail system for use within mow strips and other pavements. The weak-post guardrail system was originally designed as the MGS bridge rail and has also been adapted for use on culverts. It was envisioned that the weak-post design would absorb the impact forces and prevent damage to the mow strips, thereby minimizing maintenance and repair costs. Evaluation of the weak posts in mow strips began with three rounds of dynamic bogie testing. Round 1 of bogie testing showed that 4-in. (102-mm) thick concrete would sustain only minor spalling from impacts to the posts. However, the posts would push through 4-in. and 6-in. (102-mm and 152-mm) thick asphalt mow strips. During Round 2, 24-in. (610-mm) long, 4-in. x 4-in. (102-mm x 102-mm) sockets with 10-in. x 9-in (254-mm x 229-mm) shear plates were utilized to better distribute the impact load to the asphalt pavement and prevent damage. However, Round 3 of bogie testing consisted of dual-post impacts, and the asphalt suffered from shear block fracture between the two 24-in. (610-mm) sockets and the back edge of the mow strip. A dual-post test within a 4-in. (102-mm) thick concrete pad showed only minor spalling. A full-scale MASH 3-11 test was conducted on the weak-post guardrail system installed within an asphalt mow strip. Due to the Round 3 testing results, the asphalt thickness was increased to 6 in. (152 mm), and the socket depth was increased to 30 in. (762 mm). The 2270P pickup was contained and safely redirected, and all MASH safety criteria were satisfied. Unfortunately, the asphalt fractured, and a 2ó-in. (64-mm) wide crack ran from socket to socket throughout the impact region of the system. Therefore, the weak-post guardrail system was crashworthy, but would require repairs in its current configuration. The system could also be installed in a concrete mow strip to prevent pavement damage

Development of a Socketed Foundation for the Midwest Weak Post V1

A socketed foundation was designed and evaluated for use with the Midwest Weak Post (MWP), Version 1. Dynamic component testing was conducted on five different design configurations with varying embedment depths, steel reinforcement, and soil conditions. The low strength of the MWPs limited the force transferred into the foundations and prevented damage in the form of concrete cracking or fracture. Additionally, the lateral movements of the socketed foundations were all within the 1-in. (25-mm) limit established to ensure reuse of the foundations without resetting. The selected design consisted of a 12-in. (305-mm) diameter concrete shaft reinforced with four vertical bars and transverse hoop steel spaced at 6½ in. (165 mm) on center. A 4-in. x 3-in. x ¼-in. (102-mm x 76-mm x 6-mm) steel tube socket was placed in the middle of the shaft. Finally, guidelines were given for the length, or embedment depth, of the foundation based on surrounding soil conditions and risk of frost heave

Transition of Temporary Concrete Barrier

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

Development of a Transition Between an Energy-Absorbing Concrete Barrier and a Rigid Concrete Butress

From 2010 to 2015, MwRSF researchers developed the RESTORE barrier, which is a restorable MASH TL-4 median barrier with a steel and concrete rail supported by elastomer posts and steel skids. The research effort reported herein describes the initial development of a transition from the RESTORE barrier to a rigid TL-4 concrete buttress. The previously-developed RESTORE barrier LS-DYNA model was validated against three full-scale vehicle crash tests. Several design concepts were generated through a series of brainstorming efforts. The primary transition concept consisted of a pin and loop connection between the RESTORE barrier and rigid concrete buttress, which was designed and evaluated with LS-DYNA computer simulation. Vehicle and system behavior were investigated using MASH test designation nos. 4-20, 4-21, and 4-22. Six horizontal gusset plates and drop-down pin allowed for limited deflection and rotation at the transition joint, but provided shear continuity between the two systems. A rounded-edge cover plate mitigated vehicle snag on the transition joint hardware. Eleven impact points were evaluated with each vehicle model to determine critical impact points for use in a future full-scale crash testing program. All occupant risk measures and vehicle stability were within MASH limits. Further design modifications are recommended to limit stresses in the transition joint hardware and to reduce excessive occupant compartment deformation that occurred when the small car impacted the concrete buttress end