Road structure – process – or apparatus – Traffic steering device or barrier
Reexamination Certificate
2002-11-06
2003-11-11
Will, Thomas B. (Department: 3671)
Road structure, process, or apparatus
Traffic steering device or barrier
Reexamination Certificate
active
06644888
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a guardrail structure mounted along a roadway, and more particularly to post supports for supporting guardrail beams or panels which extend longitudinally in a direction generally parallel to the roadway.
BACKGROUND OF THE INVENTION
Roadway safety barrier and crash attenuation systems are an important safety feature and component of today's roadways. These systems serve to address the potentially catastrophic results of situations where errant motorists might otherwise leave the relative safety of the designated roadway, or might stray from the safety of normal traffic conventions. They accomplish this by redirecting the vehicle away from a hazardous area in a controlled manner, while absorbing some of the energy of the vehicle through deformation of the system. These systems often include portions having posts that serve as an integral component. This is because posts contribute to the effectiveness, economy of manufacture, ease of installation, and maintenance of these systems, as well as to their reliability.
The posts of a typical safety barrier or crash attenuation system serve to maintain the system in its optimal configuration and state of readiness relative to the roadway, including factors such as height, spacing, support, tension, rigidity, and energy absorption capability. These configuration aspects enable the various components of the system to perform in unison to accomplish their overall purpose of protecting motorists by absorbing and dissipating energy as the system reacts and deforms while responding to errant vehicles. In these applications, the posts are commonly fastened (bolted) or welded to various other roadway features, and may also be partially submerged in the ground in order to give them rigidity as well as to provide a means of anchoring the system while transmitting impact forces to the ground.
Over the past several years, the Federal Highway Administration (FHWA) as well as State Departments of Transportation (TDOT's) throughout the country have increasingly sought to improve the economy, strength, and effectiveness of roadway barrier and crash attenuation systems, including posts, guardrails, fasteners, end treatments, and other components. Thus, installed systems and their components have been required in recent years to sustain increasingly higher levels of economy and performance. This has led to system test requirements that reflect these increasingly higher standards.
Accordingly, these systems are now commonly tested using vehicles having somewhat increased speeds and angles of incidence upon impact with the systems. However, these seemingly small changes in vehicle speed and trajectory may result in substantial increases in the performance requirements of the system. This is because the forces that are imposed upon a system and its components during an impact are highly sensitive to vehicle speed and angle of incidence. Moreover, still additional increases in system forces have been introduced as follows. First, typical test vehicles now have increased mass. Second, the types of test vehicles have been modified to more adequately represent the actual fleet of vehicles on today's roadways. These modifications include vehicles having higher bumpers and centers of gravity, both of which contribute to greater challenges for barrier and crash attenuation systems in achieving-successful performance.
This trend toward increasing economy and performance is very desirable. Yet is has imposed a great challenge on the roadway safety community, because these specifications sometimes seem to require conflicting characteristics of the system. The discussion below describes several aspects of this challenge, with particular emphasis on the implications for existing conventional barrier post designs and the need for innovations that can adequately address the shortcomings of the present state-of-the-art in a cost-effective manner.
The first and most common approach taken by the roadway safety community in addressing these higher requirements has been to make the conventional barriers and posts out of heavier gauge material. For example, heavier gauges of guardrail, made from 0.130 inch thick (10 gauge) material now seem to be more common. I-beam posts are sometimes specified in weights of eight and a half and more pounds of steel per foot. This corresponds to specified flange thicknesses of 0.194 inches, and web thicknesses of 0.170 inches for a W6×8.5 post. In some applications even heavier I-beam posts are used. The use of thicker material has not only led to greater cost for roadway product manufacturers and consumers but also, as will be shown, has had the effect of creating other challenges simultaneously. The following is a discussion of various aspects of these challenges.
The approach of simply increasing material thickness in order to address higher standards may initially seem to minimize the number of changes that are required in updating specific parts of the system, such as the posts. However, this approach may also have some consequences in terms of its effect upon the vehicle. This is because thicker, heavier, and more rigid barrier systems may impose more sudden changes upon the trajectory and speed of an errant vehicle that can in turn affect the vehicle occupants. In addition to this, as the posts are made to be heavier, the posts themselves may become significant obstacles and sources of undesirable local levels of impact to the occupant compartment of the vehicle.
Moreover, in some barrier systems such as guardrail systems, the heavier posts may represent such an obstacle that they often inherently include or otherwise incorporate special characteristics that give them directional strength. This makes them stronger in one direction as compared with the transverse direction with respect to the roadway. One example of this is found in some longitudinal barriers having discontinuities or terminations near their longitudinal ends. In such cases it is often desirable to permit some of the end terminal posts to selectively break away or collapse to the ground rather than represent an obstacle that might unduly damage the vehicle if the end terminal region is struck head-on by a vehicle.
But the increase mass of barrier posts are not the only challenge facing the present state-of-the-art for barrier and crash attenuation system posts. The following is a discussion of some additional considerations that need to be addressed. In this discussion, specific geometrical features are discussed along with their performance characteristics.
Several types of posts are commonly used today in roadway barrier systems. One very common type of post that is found in roadway barrier systems is made of wood. These posts may be of round or rectangular cross-section. Others are hybrids that are made of metals such as steel in combination with materials such as wood or plastic. Hybrid posts are not considered to be extremely viable because of processing costs, and because of complexities associated with maintaining strong and viable interfaces between the materials over extended periods of sunlight, moisture, and temperature cycling during service.
Steel posts include those that have sections that are hot-rolled, cold rolled, or “built up” or joined sections that may represent open or closed cross-sections. Material cost, durability, reliability, and maintenance issues have favored a trend toward steel posts over wood or hybrid systems. However, these posts have remained relatively the same over the past few decades. Cost is always a consideration as more rigid (and thus generally heavier) conventional posts are considered. Other considerations are discussed below using the common hot-rolled steel I-beam post as an example.
Hot-rolled I-beam sections have become even more popular in recent years as the price of wood has risen. These sections consist of simple flat flanges that are joined by a middle web. Guardrail panels are commonly bolted directly to the flanges, and commonly have
Browning & Bushman P.C.
Florio Kristine
Helmreich Loren G.
Will Thomas B.
LandOfFree
Roadway guardrail structure does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Roadway guardrail structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Roadway guardrail structure will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3142706