Nauman M Sheikh

State of the Practice of Cable Barrier Systems

This paper presents the state of the practice of the use of cable barrier systems in the United States. A literature review was conducted to identify the types of cable barriers systems being used. The scope of this review included benefits of using cable barriers, available guidelines, policies or procedures related to barrier placement, and issues related to the maintenance and in-service performance of the cable barriers. A comprehensive survey was conducted to identify experiences, practices, and design and construction standards for the use of cable barrier systems. To improve survey quality, survey participants were people identified as managing the cable barrier systems firsthand. The participants were therefore likely to be most knowledgeable about the design and construction, maintenance, and overall experience of cable barrier usage. Concluding remarks about the state of the practice of cable barriers, along with areas of further research, are presented.

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.

Development of Hybrid Energy-Absorbing Reusable Terminal for Roadside Safety Applications

The hybrid energy-absorbing reusable terminal (HEART) is a newly developed crash cushion or end terminal to be used in highway safety applications to mitigate injuries to occupants of errant vehicles. HEART is composed of corrugated plates of high-molecular weight, high-density polyethylene (HMW-HDPE) supported on steel diaphragms that slide on a fixed rail. Kinetic energy from errant vehicles is converted to other energy forms through folding and deformation of the HMW-HDPE material. Many previous designs utilized plastic or permanent deformation of plastics or steels to accomplish this goal. However, HEART is a combination of plastic and steel that forms a largely self-restoring and largely reusable crash cushion. Consequently, HEART has a major life-cycle cost advantage over conventional crash cushion designs. HEART was developed through extensive use of finite element analysis with LS-DYNA. The simulation approach adopted for the development of HEART, construction details, and a description and result...

Application of Precast Concrete Barrier Adjacent to Steep Roadside Slope

When concrete barriers are installed adjacent to drop-offs or steep roadside slopes such as 1.5H:1V, a cast-in-place concrete moment slab is usually attached to the base of the barrier to resist lateral and overturning forces during vehicle impact. Cast-in-place construction can require more time on-site to build forms, pour the concrete, and allow for curing. This time constraint results in an increase in disruption to traffic and more exposure for construction workers. Furthermore, the installation of a moment slab is very costly and requires an additional construction phase to build the slab. Because the slab is normally under the shoulder and possibly the lanes, the disruption of traffic flow is increased. A new application of a precast 42-in.-tall single-slope concrete barrier for use in front of steep slopes was developed that does not require a moment slab. The lateral movement of the barrier is restricted by embedding it in soil. This design also reduces the embankment behind the barrier to 2 ft. The embedded barrier application was successfully evaluated under Manual for Assessing Safety Hardware Test Level 3 criteria. The permanent deflection of the barrier was 5.5 in. The use of the embedded concrete barrier in lieu of the typically installed barrier with a moment slab is expected to result in cost savings of approximately

Development of Low-Deflection Precast Concrete Barrier

300 per linear foot and reduced time to construct.