"The purpose of this project is to design a non-snagging guardrail post. The procedure will be to first develop a simple finite element (FE) model of a single post, wheel and suspension to explore the snag potential for some existing standard guardrail posts. The next step in the procedure will be to develop appropriate design changes that could prevent wheel snagging and investigate if they do by using a one-post sub-model. An attempt to validate the used material model for wood will also be done by comparison between laboratory tests and finite element simulations."

No description available.

This thesis presents the results of a research effort aimed at investigating the crash performance of w-beam guardrail barriers in vehicle-roadside crashes using the finite element method. The developed roadside barrier models can be used to assess the occupant injury risk, vehicle performance, and damage to guardrail barriers during a roadside accident. The finite element models of w-beam guardrail barriers may also help evaluate the crash performance of the w-beam barriers with minor damage in vehicle-barrier crashes. Thus, the results can be used to develop repair guidelines to assist highway personnel in identifying levels of minor barrier damage and deterioration. Finite element models of the weak post w-beam guardrail barriers were developed and simulated using LS-DYNA. The simulation results were validated against full scale crash tests of pickup trucks and passenger cars impacting w-beam guardrail barriers. The maximum dynamic deflection of the guardrail, exit velocity and angle of the vehicle, and occupant injury risk were calculated and compared to the tests. Kinematics of the vehicle and guardrail were assessed qualitatively as well as quantitatively. The analysis showed that simulation results were in good agreement with test data. Additionally, the models were validated against pendulum tests conducted the Federal Outdoor Impact Laboratory (FOIL). Simulation results of pendulum tests showed that the test section taken from the current full scale models performed very similarly to that in the real pendulum tests. The developed finite element models were subsequently used to examine the crash performance of weak post w-beam guardrail barriers with minor damage under vehicle impacts. Only rail/post deflection based minor damage to weak post w-beam guardrail barriers was considered in this study. Simulations were completed to obtain the damaged profiles of the guardrail systems; the damaged weak post guardrail barriers were impacted by the pickup model at mid-span for the second time. The impacting vehicle remained stable in all of these simulations. No conclusions could be drawn however whether these second impacts could have resulted in rail tearing or rupture. / Master of Science

"Recent full-scale crash tests of the weak-post W-beam guardrail system have resulted in unsatisfactory collision performance as evaluated by the National Cooperative Highway Research Program (NCHRP) Report 350. Since acceptable crash test performance is required in order to use a guardrail on a Federal-Aid Highway in the United States, the poor performance of the weak-post W-beam guardrail is a significant problem to those states that use it. The goal of this project was to improve the impact performance of the weak-post W-beam guardrail system so that it satisfies the requirements of NCHRP Report 350 at test level three."

Safety is an important aspect when designing bridges and roads. One aspect among others to consider is the road restraint systems. The focus of this study was centered to safety barriers which are the vehicle parapets/guardrails. The parapet must meet certain requirements specified in European Standard in order to obtain a CE-marking, indicating the acceptance of use. Full-scale test must be performed for a proposed parapet to evaluate the performance. Often several full-scale tests are performed in order to achieve CE-marking, making it an expensive process. The primary objective of this master thesis was to investigate if Abaqus/Explicit could be used as the finite element software for simulation of crashes. Secondary objective was to investigate how well a performed full-scale crash could be simulated in Abaqus/Explicit. A full-scale test was conducted and the parapet installation and vehicle used was modeled. Same conditions as in the full-scale were used in the simulation. The results indicated that it is possible to simulate the full-scale crash using Abaqus/Explicit. However, the behavior of the full-scale test was not completely captured. The maximum dynamic and permanent horizontal deflection of the tabular thrie beam in the full-scale test was 582 mm and 515 mm, corresponding value from the simulation was 703 mm and 643 mm. The conclusion from the results is that Abaqus/Explicit is a suitable finite element software for simulating crashes. The differences between the full-scale test and the simulations in this master thesis were due to the simplifications and assumptions used when modeling the parapet, bridge deck and the vehicle. The overall global behavior of the full-scale test was not captured, however the simulation results were not far from the full-scale test even though rough simplifications and assumptions were used in the modeling. We believe that with more care to details in modeling, it should be possible to have better convergence between simulation and the full-scale test.

Guardrails are a key safety feature of modern roadways. Collisions with many roadside hazards, e.g. trees, poles and culverts, can be dangerous and guardrail prevents many crashes with such hazards. However, using guardrail safely and effectively is a challenging problem in itself. This research examined two aspects of the problem: 1) assessment of the injury risks posed by guardrail itself; 2) determination of appropriate guardrail length. When controlling for other factors, light truck / van / sport utility vehicles (LTVs) showed injury odds 3.9 times greater in end terminal crashes compared to guardrail face crashes, while cars showed no significant increase in injury odds. Additionally, the odds of injury in frontal end terminal crashes appeared to be between 3.9 and 5.0 times lower when the terminal design was compliant with the National Cooperative Highway Research Program (NCHRP) 350 crash testing protocol, compared to non-compliant designs. Rollover occurred in 10 % of all frontal guardrail crashes, and was initiated by the guardrail in roughly 46 % of instances. The evidence indicates that end terminal contact increases rollover odds by 6.9 times compared to guardrail face contact for LTVs, but not for cars. NCHRP 350 compliance of end terminals was not observed to have any significant effect on rollover propensity. In side-impact crashes with guardrail, end terminal crashes represented only about 25% of crashes but accounted for more than 70 % of the injuries sustained. End terminals compliant with NCHRP-350 may be about five times as safe as non-compliant designs, but the difference appears to be overshadowed by the high degree of risk involved in striking any narrow fixed object with the side of the vehicle. A somewhat larger sample appears necessary to make this finding significant at the 95 % confidence level. Only about 20 % of rollovers in non-tracking guardrail side crashes are initiated by contact with the rail; 80 % are initiated by some subsequent contact. Those rollovers which are rail-initiated appear to be about twice as likely to be initiated by a terminal as by the guardrail face. Cars showed odds of minor to severe injury 3.6 times greater than LTVs in end terminal crashes. End terminal designs compliant with NCHRP 350 were not observed to carry significantly different odds of minor to severe injury than non-compliant end terminals. The findings control for driver seat belt use, rollover occurrence, terminal orientation (leading/trailing), control-loss and the number of impact events. Rollover and non-use of seatbelts were observed to carry much larger increases in risk than end terminal type. For cars, electronic stability control (ESC) reduces odds of fatal crashes with roadside barriers by about 50 % For LTVs, ESC reduces barrier fatality odds by about 40 %. Based on the effectiveness levels observed in this research, it is estimated that ESC could prevent about 410 out of 1180 possible barrier-related fatalities per year by 2028, when 75 % of the fleet is estimated to be equipped with ESC. The study findings suggest that ESC significantly reduces road departures into roadside barriers, and/or that ESC changes departure conditions so that barrier crashes have less severe outcomes. This research has compared the current standard procedure for computing guardrail length of need (LON) with 'departure corridors' based on real-world road departure trajectories. Due to the current procedure's simplified treatment of road departure geometry, LON recommended by the current procedure becomes very conservative for hazards located closer to the roadside, and less conservative for hazards located further away. By contrast, the departure corridor technique developed in this research provides a known, precisely defined level of protection which remains the same for different hazard offsets. Departure corridors can be made for any desired level of protection, and the technique provides flexibility in how protection may be defined. Most importantly, the departure corridor technique is fundamentally more realistic than the current standard procedure and gives LON recommendations which provide protection levels that can be easily communicated to policy makers and other stakeholders. / Ph. D.

Crash tests of strong-post w-beam guardrail have focused entirely on the performance of new guardrail. The risk posed by minor damage modes, e.g. small deflections and missing posts, has never been evaluated. Using finite element models validated by real world crash tests, this study assessed the safety risk of crashes into guardrail with minor damage. The minor damage modes under consideration for this study were rail and post deflection, missing posts, rail flattening, and post/rail separation. Each of these damage modes was evaluated according to the testing protocols laid out in National Cooperative Highway Research Program (NCHRP) Report 350, test level 3. A number of minor damage modes were found to pose significant risks to vehicle occupants and should be repaired as soon as possible. In order of priority of repair, these modes are missing posts, rail and post deflection over 6â , and rail flattening over 50%. Damage modes of less concern were rail and post deflections less than 6â , rail only deflection up to 6â , flattening less than 50%, and separation of the posts from rails. These recommendations were on the conservative side because preventing occupant injury was the highest priority of guardrail performance. Guardrails with rail and post deflection posed a risk of vehicle vaulting due to lowered rail height and failure of the posts to separate from the rails. This risk would be even greater for guardrails embedded in soft soils, which allow for greater deflection. Guardrails with missing posts frequently resulted in snagging of the vehicle tire on the downstream posts, as well as large increases in the tension carried by the rails during impact. Flattened rails posed a risk of vehicle rollover as they provided a ramp-like surface which caused the side of the vehicle to move upward, greatly increasing the change of override. Flattening also occurs frequently with other damage modes. Pre-existing separation of posts from the rails was found to have very little effect on the crash outcome. Separation of the posts from the rails was desirable as it prevented failure modes that were observed for the rail and post deflection simulations while maintaining the post contributions to lateral strength of the guardrail. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / Driving safety is a very important topic in vehicle development. One of the biggest threat of driving safety is road departure. Many vehicle active safety technologies have been developed to warn and mitigate road departure in recent years. In order to evaluate the performance of road departure warning and mitigation technologies, the standard testing environment need to be developed. The testing environment shall be standardized to provide consistent and repeatable features in various locations worldwide and in various seasons. The testing environment should also be safe to the vehicle under test in case the safety features do not function well. Therefore, soft, durable and reusable surrogates of roadside objects need to be used. Meanwhile, all surrogates should have the same representative characteristics of real roadside objects to di erent automotive sensors (e.g. radar, LIDAR and camera). This thesis describes the study on identifying the radar characteristics of common roadside objects, metal guardrail, grass, and concrete divider, and the development of the required radar characteristics of surrogate objects. The whole process is divided into two steps. The rst step is to nd the proper methods to measure the radar properties of those three roadside objects. The measurement result of each roadside object will be used as the requirement for making its surrogate. The second step is to create the material for developing the surrogate of each roadside object. In the experimental results demonstrate that all three surrogates satisfy their radar characteristics requirements.

No description available.

No description available.