Akram Y Abu-Odeh

Optimum design of composite plates using response surface method

A method for construction of response surfaces that predict the vertical displacement and three bending moment components at a point on a composite plate is presented. These approximate structural responses, which are global in character, are used in the optimization of a plate in lieu of an exact FE analysis during constraint evaluation. The results from five example problems compare optimal plate designs obtained using exact analysis with those based on approximated structural response.

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.

Numerical simulation of mow strip subcomponents used with strong post guardrail systems

Abstract Pavement mow strips are being used to combat vegetation growth around guardrail posts. However, the effect of pavement post encasement on the crashworthiness of strong post guardrail systems has not been investigated. In this paper, results from numerical simulation of mow strip subcomponents are compared with field experimental testing. Mow strip dimensions, materials, and depths are considered in addition to the presence of ‘leave-out’ sections around posts. Wood and steel guardrail posts embedded in various mow strip systems and confinement conditions were subjected to dynamic impact testing with a bogie vehicle. Results from these tests are compared with numerical simulations carried out using the nonlinear, dynamic, finite-element analysis code LS-DYNA. Results of simulation indicate that most of the subcomponent models can be used with confidence in design of mow strip barriers for vehicle impact.

Stability Analysis and Full-Scale Test of Traffic Barrier–Moment Slab System

Traffic barriers that can resist vehicle impact without being tied to a structure are needed at the top of mechanically stabilized earth walls. These barriers are usually constructed in an L-shape so that the impact load on the vertical part of the L can be resisted by the inertia force necessary to uplift the horizontal part of the L. The design load for such barriers has changed from 44.5 kN (10 kips) to 240 kN (54 kips) over the past decade. This increase has created concern about which load should be used. This paper contributes to answering that question. It shows the results of analytical solutions to the problem as well as one static load test and two impact tests on the same full-scale barrier. The conclusions are that 44.5 kN (10 kips) is an equivalent static load and that the 240 kN (54 kips) is a peak-impact load. Analytical and experimental approaches are used to provide better understanding of the behavior of the barrier–moment slab system. Guidelines for the dimensions of the barrier– moment slab system are presented and justified on the basis of the work described.

Short-Radius Guardrail System for NCHRP Report 350 Test Level 2 Conditions

When a road or driveway intersects a highway with certain restrictive features (bridge rail, culvert, etc.), it is difficult to fit the proper guardrail length (transition, length-of-need guardrail, and end treatment) along the primary roadway. Site constraints such as private driveways, state roads, and parish or county roads may intersect the primary road and prohibit the placement of a properly designed guardrail of the length needed. In these cases, the alternatives are to shorten the designed guardrail length, to relocate the constraint that is blocking placement of the guardrail, and to provide a curved or T-intersection guardrail design. This curved guardrail system is usually known as a short-radius guardrail. This paper investigated the performance of previously tested short-radius guardrail systems to determine whether some of those guardrail systems met NCHRP Report 350 Test Level 2 (TL-2) evaluation criteria. A system designed and tested for Yuma County, Arizona, was adapted as the basis for developing a short-radius guardrail system that satisfies NCHRP Report 350 TL-2 criteria. From an engineering review of previous designs, a recommended short-radius guardrail system that satisfied NCHRP Report 350 TL-2 conditions was developed. The nose section of this system consists of a 3.82-m (121/2-ft) curved W-beam segment that has a 2.44-m (8-ft) radius. This curved section is mounted on breakaway controlled-release terminal posts.