Truck Impact Research Articles

On the Treatment of Trucks in Roundabout Analyses

Trucks are not always addressed explicitly in planning studies and operational analyses, even though they are a very important part of the nation's economic engine. Most planning studies account for trucks as a percentage of the total traffic flow. The Highway Capacity Manual (HCM) converts trucks into autos through the use of a passenger car equivalency (PCE) factor. If the PCE is 2, then a truck is assumed to be equivalent to two autos. However, trucks are beginning to receive more attention, including that in the context of capacity assessments. A recent research effort focused on developing a level-of-service assessment for trucks and for enhancing the way that the impact of trucks is taken into account on freeways, arterials, and roundabouts. This paper focuses on the roundabout aspects of that research. The three roundabout-related objectives in the project were (a) to refine the PCE values used to convert trucks into auto equivalents for the flow on roundabout approaches, (b) to recalibrate the capacity equation so that it more appropriately accounts for trucks, and (c) to develop ways to estimate truck speeds so that travel times through the roundabout could be computed. The results of these analyses are presented as well as the methodology and data employed.

Investigating Impacts of Pickup-delivery Maneuvers on Traffic Flow Dynamics

Even if urban logistic has been extensively investigated in the literature, its effects on traffic flow dynamic remain mostly unknown. This paper aims to assess the impact of pickup-delivery trucks on traffic conditions. To this end, we resort to a theoretical but realistic urban arterial where deliveries are completed in double-park. The study first focuses on traffic flowing at capacity and determines the analytical formulation of the effective capacity when neglecting the effects of traffic signals. This formulation only depends on the characteristics of the arterial, the average time headway between truck arrivals and the average stop duration. It turns out that the pickup-delivery maneuvers strongly reduce the capacity. Then, this modeling framework is extended to other traffic conditions. The use of the macroscopic fundamental diagram (MFD) makes it possible to incorporate effects of traffic signals. To this end, an existing MFD estimation method is adapted to the case of double-park deliveries. The comparison of the MFD estimates highlights that logistic activities have a major impact for traffic conditions near the maximal capacity. It confirms that creation of dedicated delivery areas and related logistic policies (pre-booked area, off-pick hours deliveries, etc.) are very promising solutions to improve both the efficiency of the transportation network and the logistic system.

A Comparison Study of Direct Impact Analysis of Vehicle to Concrete Pier and In-Direct Impact Analysis using Load-Time History Functions

Abstract In design standards such as AASHTO LRFD and Korea Highway Bridge Design, the dynamic behaviors under the impact loading has not been considered and it recommends of using a static force for designing bridge column against vehicle collisions. Accordingly, in this study, models of vehicle collisions to concrete bridge column were developed with various boundary conditions in order to take into account dynamic behaviour of the column. Cargo trucks of 10tons, 16tons and 38tons were selected and a typical type of concrete bridge pier column along the Kyungbu highway in Korea was selected for this study. Results from this study indicate that the static load specified in the design standards are too small compared to results obtained in this study. It was also found that a consideration of the bridge superstructure allowed smaller damages of concrete bridge pier column under truck impact loadings. Furthermore, a comparison study of direct impact analysis of vehicle to bridge-column with in-direct impact analysis using load-time history functions was performed. The in-direct impact analysis shows that the use of load-time history graph improves the computational cost up to 92% and predict the behaviors of the bridge column under the impact loadings well. The obtained load-time history graph could be easily applied to several existing models.

Experimental Study on Impact Resistance of Dump Truck Bodies Floor

In order to study the impact resistance capability of dump truck bodies floor, a simulation model of dump truck bodies floor and impact hammerheads made of metal materials were designed, and a strain test system of bodies floor under impact loading was established, a measurement of the stress of bodies floor model was made to obtain the law of stress variation about key point of truck bodies floor model. The research laid the foundation for the analysis of impact resistance capability of dump truck bodies floor using finite element method as well as provided a reference for the structural optimization of truck bodies floor.

Test and numerical simulation of truck collision with anti-ram bollards

Inelastic transient finite element simulations based on an actual truck collision test are used to investigate the demands imposed during collisions between medium-duty trucks and anti-ram bollards constructed with concrete-filled steel tubes (CFT). The medium-duty truck is considered for crashing into a bollard at speed 50, 65, and 80 km/h, respectively, based on performance demands of bollards of different grades. Numerical results show that both the impact force and the bollard deflection increase with increasing the truck impact speed. When the speed is relatively high (e.g. 80 km/h), there is a risk of the truck climbing over the bollard, even with little damage to the bollard. The analyses show that the impact force along the height of the bollard is not uniform and may change during the impact process. Considering the complexity and computation time consumption, a simplified analysis based on a two-degree-of-freedom mass-spring-damper system model is developed to simulate the collision process. In the analysis, a bilinear spring is used to characterize the truck considering its “soft front and hard rear” characteristics when impacting bollards. Results show that the simplified analytical model is in good agreement with the finite element model using a detailed truck model.

Evaluation of Truck Impact Hazards for Interstate Overpasses

Increased freight activities on Interstate highways escalate the risk of collision between trucks and overpass bridges. Although such events are rare, the consequences of such a collision may be catastrophic. Many overpass bridges were designed and constructed in the early years of development of the Interstate highway system and therefore did not meet the requirements specified in AASHTO's Load and Resistance Factor Design Bridge Design Specifications. In this study, 5-year truck run-off-the-road crash data, information on Interstate highway geometric characteristics, and traffic information were collected to develop crash prediction models for bridge bents. The bent-based predictive methods improved the collision risk estimate by evaluating the individual bents of a bridge on the basis of roadway geometrics and traffic conditions. The detour costs subsequently measured on the basis of the additional road user costs caused by the failure of a bridge were used to assess the importance of a bridge quantitatively. As a result of this study, a bridge index was developed from both the collision risk and detour costs. This study could provide guidance to departments of transportation to develop mitigation plans for bridges with high collision risk indexes.

Parametric Effects on Evaluation of an Impact-Damaged Prestressed Concrete Bridge Girder Repaired by Externally Bonded Carbon-Fiber-Reinforced Polymer Sheets

AbstractThis paper investigates the evaluation procedure of an AASHTO Type 3 precast-prestressed girder that was extensively damaged by truck impact and then repaired using externally bonded fiber-reinforced polymer (FRP) composites. Results of this study can be applied to bridges having similar vehicle impact incidents. Parameters whose effects were investigated on the evaluation procedure include (1) the effect of horizontal resistance of elastomeric bearing supports, (2) the presence of barrier wall and sidewalk, and (3) live load distribution factors obtained from finite-element analysis (FEA) compared with the simplified method prescribed by other codes. FEA showed that support horizontal resistance has negligible effects on live load distribution factors for shear, Fv, while it has considerable effect on live load distribution factors for moment, Fm. The live load distribution factors Fm and Fv calculated from the simplified method of analysis prescribed by other codes were observed to all be greate...

Impact of Various Trucks on Pavement Design and Analysis

This investigation assessed the sensitivity of Mechanistic–Empirical Pavement Design Guide (MEPDG) outcomes to normalized axle load spectra representing various loading conditions observed in the Specific Pavement Studies Transportation Pooled Fund Study of the Long-Term Pavement Performance program. The goal was to determine what vehicle classes and axle types with a wide range of axle loading conditions are likely to cause differences in pavement design outcomes when the MEPDG is used. Significant differences found in the MEPDG outcomes support the need for characterization of axle loading beyond a single default value for heavy trucks that dominate vehicle class distributions, especially for Class 9 trucks. The absence of differences for lightweight and under-represented trucks indicates that load spectra from various sites could be combined to develop a single default for some vehicle classes and axle types. The effect of bias in weigh-in-motion (WIM) axle weight measurements on the normalized axle load spectra estimates and the associated MEPDG outcomes was also investigated. It was found that drift in WIM system calibration leading to a more than 5% bias in mean error between true and WIM-measured axle weight could lead to significant differences in MEPDG design outcomes. These results were used to develop recommendations for creating axle loading defaults for the MEPDG.

Overview and Preliminary Study of Approach - Slab Design Concept for Bridges

Abstract Settlement has been an issue when construction on soft soils is concerned. Many types of soils are classified as soft soft soils such as peat soils, soft clays and organic soft soils. Local and federal authorities in Malaysia responsible with road construction are always faced with undulating effects when roads meet bridges and those which are constructed on soft soils such as peaty and soft clays. Thus, it is of utmost important to study the effect of bridge designs and choice of structures for a particular condition. In this research, differential settlement between bridges and pavements will be study to understand the behaviour of soils and bridge structures. Bridge approach slab is a concrete transitional roadway between the bridge deck and the asphalt pavement. It is designed to reduce the vehicle dynamic effects on the bridge. However, growing numbers of rough riding and cracked approach slabs with heavy maintenance requirements is sufficient to convince highway agencies that a serious problem exists. The complaints usually describe a ‘bump’ that motorists feel when they approach or leave bridges. This bump results in reduction of steering response, distraction to the driver, amplified truck impact and dynamic response in bridge decks, and expense to maintenance operations. The introduction of approach slabs by many engineers has reduced some of the problems at the interface sections but only for a short period of time. The simulation using PLAXIS computer software and field geotechnical studies will be lead to the development of a proposed new interface road bridge test-bed at RECESS Malaysia, UTHM acronym IRB Test Bed as a full scale testing.

Evaluation of a Noncomposite Steel Girder Bridge through Live-Load Field Testing

This paper presents the field evaluation of a damaged noncomposite steel girder bridge that is part of the interstate highway system in Vermont. This bridge is typical of late 1960s construction and spans over a two-lane state highway near the town of Weathersfield, Vermont. The superstructure contains three-span continuous girders supported on abutments at the ends and on RC multicolumn interior bents. Strains were measured during live-load testing that was conducted to better understand the bridge behavior. The field results were compared with results from finite-element models created using common engineering assumptions. In addition, the load-distribution characteristics of girders that were damaged by an overheight truck traveling on the state highway under the bridge were evaluated. The results indicate that alternate load paths were developed within the bridge superstructure as a result of damage from the truck impact. For the loading magnitude applied during the load tests, evidence of composite action was observed and participation of curbs on the response of the bridge was noticed. Bridge skew and partial restraint generated at the supports also contributed to differences in the observed and calculated responses. These nondestructive load testing results were used to provide confidence on the load-carrying capacity of the bridge and to avoid costly bridge closures and detours.

Drive-In Steel Storage Racks. II: Reliability-Based Design for Forklift Truck Impact

Steel drive-in racks are susceptible to structural failure from accidental impact by operating forklift trucks. Under impact, the upright bends and the supported pallets may drop through the rack to cause structural collapse if the bay opening exceeds the pallet bearing width. This drop-through limit state has not been considered in existing rack design standards. This paper proposes a simple equation to calculate the equivalent static impact force based on recent tests and nonlinear dynamic analysis of drive-in steel racks. An impact load factor is developed on the basis of a structural reliability assessment, taking into account the uncertain nature of the impact force, structural resistance, and models used in structural analysis. In design practice, the bay opening is determined from factored impact loads and is not to exceed specified limits.

Determination of accidental forklift truck impact forces on drive-in steel rack structures

The paper addresses the problem of determining the accidental forklift truck impact forces on steel storage racks. Based on first principles of mechanics, simple models of a loaded forklift truck and a drive-in racking structure are presented. Model masses, as well as stiffness and damping coefficients are calibrated against experimental results obtained from tests of a forklift truck and a drive-in racking structure. Comparisons between experimental results and solutions obtained from the simple mechanical models show that the simple models accurately reproduce the static and dynamic behaviours of their associated structures. Based on the drive-in rack impact test results presented in a companion paper (Gilbert and Rasmussen, submitted for publication) [1] and the simple mechanical models for drive-in racks, actual impact forces are calculated and presented. Finally, using the impact test results and the simple mechanical models, the actual motion of the forklift truck body is calculated. This motion, being a common characteristic to all drive-in racking impacts, allows impact forces to be obtained for various pallet loads, impact elevations and rack characteristics. Thus, the paper concludes with a general method for calculating forces generated under forklift truck impact.

Will tweet for food. The impact of twitter and New York City food trucks, online, offline, and inline

Will tweet for food. The impact of twitter and New York City food trucks, online, offline, and inline

Assessing the impact of driverless haul trucks in Australian surface mining

Australia has been a leading mining nation and its mines continue to attract substantial investment due to its strong mineral endowment, mining tradition and high skills base. In recent years Australian mining companies have been facing higher labour costs, which need to be offset by other savings. Automating mine-site machinery offers one potential source of such savings. Underground mines pioneered automated technology largely for safety and mine accessibility reasons and to reduce operating costs. Yet these operations now represent a much smaller portion of the total ore tonnes mined due to the changing mining techniques meaning larger lower grade deposits are becoming economic. It appears the future of mine automation will be directed by surface mining as this maturing technology finds further applications above ground and in the next decade large scale open pit automation trials gain more momentum. This paper assesses the implications of introducing driverless haul trucks in a typical large remote Australian open-pit mine. Such automation will save employee and associated costs, increase operational productive hours and ultimately will reduce mine site workforce numbers. While there will be fewer jobs per mine, with reduced costs and higher productivity some previously uneconomic mines may again be profitable. The social implications of greater mine site automation are the reduction in population of remote mining towns and a decrease in the lower skilled labour requirements for the mining sector. There will be an increase in fly-in fly-out mining operations and companies will establish remote control centres for automated mines in larger cities. This may decrease overall labour requirements and so reduce employment in the sector; therefore, the government should be mindful of implementing policies that ensure a fair return on the economic rent of mineral leases.

An Analysis of Injuries to Haul Truck Operators in the U.S. Mining Industry

Because haul trucks are used extensively in mining, the operators of these trucks are exposed to various risks and hazards inherent to this occupation. The objective of this work was to profile injuries sustained during haul truck operations, to identify priorities for further investigation, and to determine potential injury prevention strategies. Data from the Mine Safety and Health Administration (MSHA) annual administrative database were sorted and reviewed to select records identifying a subset of injuries sustained during haul truck operations. Records covering a 5-year period (2004–2008) involving haul trucks were reviewed. The majority of the injury records were for injuries classified as “struck against moving object” (STRUCK) (N=613) and “slip or fall of person from an elevation or on the same level” (SLIPFALL) (N=359). Each injury narrative was read to determine the activity being performed during the injury (such as ingress, egress, driving, maintenance), the incident results (such as operator impact and truck impact), contributing factors to the event, and environmental factors. The nature of the injury, body parts affected, as well as lost work days were also quantified. The average lost work days for STRUCK and SLIPFALL injuries was 60 and 62, respectively. The majority of the total incidents resulted in sprain and strain injuries; the back was the most frequently injured body part injured. For STRUCK injuries, the majority of activities being performed at the time of the injuries involved driving (63%). More than one-third of the total incidents resulted in vertical jarring of the haul truck (36%), and the majority of the total incidents caused jolting and jarring to the operator (75%). For SLIPFALL injuries, the majority of incidents occurred during egress from the vehicle (46%), and of the total incidents, 32% resulted in the worker falling. Almost one-third of the total incidents were due to the operator's foot slipping (32%). Further investigation should focus on the factors contributing to haul truck operators being struck against a moving object and those related to operators slipping and falling.

Impact of Trucks on Signalized Intersection Capacity

The most common method used for the analysis of signalized intersections in the United States is contained in the Highway Capacity Manual (HCM). In this method, the base saturation flow rate of the signalized intersection is defined in units of passenger cars per hour green per lane (pc/hg/ln). To account for the presence of large trucks in the traffic stream, the HCM includes a Passenger Car Equivalency (PCE) value. In the current edition of the HCM, a PCE value of 2.0 is applied for all large trucks, with no distinction between different sizes of trucks. The HCM also recommends a single value of 2.0 seconds for startup lost time, regardless of queue composition. Many transportation professionals have questioned the validity of the PCE value and startup lost time recommended by the HCM. They are concerned that the impact of trucks at signalized intersections is being underestimated. If this is the case, then capacity is being overestimated and intersections are not being adequately designed. The objective of this study was to identify appropriate truck PCE values and a relationship for startup lost time as a function of truck percentage in the traffic stream. To accomplish this objective, a custom simulation tool was developed based on the modified Pitt car-following model, calibrated with field data, and applied to a comprehensive experimental design. The PCE values determined from this study are 1.8, 2.2, and 2.8 for small, medium, and large trucks, respectively. A model for estimating startup lost time based on the same small, medium, and large truck classifications was also developed.

Effects of overheight truck impacts on intermediate diaphragms in prestressed concrete bridge girders

This paper studies the capacity of prestressed concrete bridge girders to withstand overheight truck impacts. The numerical model of the bridge was validated with the existing experimental data in the literature. The elastic-plastic modeling of concrete damage and quasi-static impact simulation of the bridge were considered. Parametric studies were then conducted with respect to the spacing and depth of intermediate diaphragms as well as girder types from which the role of intermediate diaphragms in protection and enhancement of prestressed concrete bridge girders from truck impacts is obtained. From the simulation results, it was concluded that the optimum spacing of intermediate diaphragms (that is, 25.0 ft [7.62 m]) is consistent with the results reported for previous studies. The depth of intermediate diaphragms should be extended to the top edge of the bottom flange of girders to provide maximum impact protection. Wide flanges in girders increase the bending stiffness and reduce the horizontal deflection and correspondingly decrease damage areas. However, deep webs in girders introduce a large rotation with respect to the deck, and thus increase the deflection under the truck impact. Design guidelines for typical parameters for intermediate diaphragms in prestressed concrete bridges are provided. The numerical finite-element parametric study provides a better understanding of placement and size of intermediate diaphragms in prestressed concrete bridges and their role in protecting girders from overheight truck impacts.

Field investigation and performance of bridge approach slabs

Bridge approach slabs are designed to function as a transitional roadway to the bridge deck, spanning the distance between the abutment and the road pavement. However, the number of rough riding approaches with heavy maintenance requirements is sufficient to convince highway agencies that a serious problem exists. The complaints usually describe a ‘bump’ that motorists feel when they approach or leave bridges. This bump results in reduction of steering response, distraction to the driver, amplified truck impact and dynamic response in bridge decks, and expense to maintenance operations. Approach slabs can lose their contact supports due to various reasons, including the settlement of soil and the bulging of embankments. The objective of this paper is to present results from a study to evaluate the analytical behaviour and the field performance of new design alternatives that could reduce or eliminate this problem. The new designs were analysed using comprehensive finite element (FE) models and were also built and instrumented at the Doremus Avenue Bridge in Newark, New Jersey, for testing and long-term monitoring. Various truck load tests were performed prior to opening the bridge to traffic. The results show that the FE models are accurate and that the new design alternatives have higher load carrying capacities than those of the existing design. In addition, results also show that long-term field monitoring using various sensors can lead to quantitative measurements of various factors that can lead to the cracking of the approach slabs.

Modeling of Bond Stresses of Overlay–Bridge Deck System

This study investigated direct and indirect factors influencing the bond strength between the concrete overlay and the bridge deck by using finite element analysis (FEA) and experimental validation. In addition, it presents reliable guidelines for the required bond strength that is needed for concrete to avoid potential delamination under various possible induced stresses. The purpose of the FEA is to predict and correlate the live load– and shrinkage-induced stresses at the interface between the concrete overlay and the bridge deck and to correlate these induced stresses with the direct tensile bond strength of the overlay. Fifteen full-scale prototype bridge systems without and with various thicknesses of overlays were studied. In addition, 42 overlay–bridge deck slab segments were created considering the relative thickness ratio of the overlay to the bridge deck slab ( toverlay/ tslab) and the relative elastic modulus ( Eoverlay/ Eslab). Also, 210 overlay–bridge deck slab segments were created considering toverlay/ tslab, Eoverlay/ Eslab, and slab concrete compressive strength ( f ‘ c). The effectiveness and accuracy of the FEA guideline models were compared with Fowler's guidelines. The FEA results reveal that the live load– and shrinkage-induced shear stresses are about 1.5 to 2.5 times the induced normal stresses, in good agreement with most of the published research. Overlay thicknesses of 38 and 63 mm (1.5 and 2.5 in.) were recommended as the minimum and maximum allowable thicknesses that will prevent the overlay from debonding when the deck is subjected to AASHTO HS-20 truck loading plus impact as well as shrinkage loading.

Further Evaluation of the Relationship between Enhanced Consistency Model and Safety of TwoLane Rural Roads in Israel and Germany

Crashes on two-lane rural highways are over-represented at horizontal curves, and speed inconsistency is a common contributing factor to these crashes. Road Consistency reflects the similarity or lack thereof of vehicle performance along an entire road segment. Consistency is measured by estimating the speed variation along successive geometric elements and evaluation of the speed deviation from the average speed. Because it has been shown in the past that speed variability has an impact on safety, it was hypothesized that design consistency is also related to safety. The purpose of this study is to examine the relationship between road design consistency and crash probability on two-lane rural highways. An enhanced consistency model is applied to examine this relationship in Israel and Germany. This consistency model is based on both the horizontal and vertical alignments and takes into account the impact of trucks and grades on road consistency. A statistically significant model that showed a reduction in average crash numbers per year with an increase in consistency is presented and discussed. It was found that the Israeli and German models have a similar trend. The enhanced-consistency model and the software may be used relatively easily to determine consistencies of different alternatives during the planning of new highways or the reconstruction of existing roads. Planners and decisionmakers could be advised of potential design deficiencies during the design process and consequently, modify a proposed design and thus improve safety levels and save lives.