Highway Loading Research Articles

STRUCTURAL DESIGN OF CONCRETE PAVEMENTS WITH LEAN CONCRETE LOWER COURSE

A procedure is presented for the structural design of concrete pavements incorporating a lower layer of lean concrete, either as a subbase constructed separately or as a lower layer in monolithic construction. An analysis of flexural stresses is used to recognize the strength and elastic properties of the materials and the layer thicknesses. Modifications of conventional linear elastic theory are made based on the properties of concretes at low cement contents and on experimental and performance data. Because these data are limited, the design procedure is suggested as a preliminary guide. Simplified design charts are presented for conventional highway truck loadings; design data are also given that may be used for aircraft and other loadings.

Fatigue performance and failure mechanism of ductile iron pipes with socket joints under traffic loads

Urban water supply pipelines experience repetitive traffic loads during their operational lifespan, potentially leading to fatigue failure. However, existing research focuses primarily on the static or dynamic mechanical responses of pipes, with limited studies on the fatigue performance of pipes. This study investigates the fatigue performance and failure mechanism of DN200 ductile iron (DI) pipes with socket joints under traffic loads and water pressure through bending fatigue tests. First, the mechanical responses of pipe joints under traffic loads derived from statistical data on highway traffic loads, soil pressure, and self-weight are calculated using ABAQUS to give the fatigue test load amplitude. Subsequently, tests are conducted on three DN200 DI pipes under a water pressure of 0.2 MPa: one for a monotonic test and two for fatigue tests under extra car and bus loads, respectively. The fatigue life of pipes under various traffic load combinations is analyzed using cumulative damage theory. Moreover, the relationship between fatigue load amplitude and number of cycles for DN200 DI pipes are obtained on the basis of the test data. Results show that the maximum rotation angle of joint is an important indicator of failure. Finally, a theoretical method for calculating the joint angle is proposed on the basis of geometric dimensions. A good agreement between the test and theoretical results is observed. Thus, the proposed method can obtain the fatigue performance of joints effectively.

Evaluation of Minimum Web Reinforcement Requirements for Slender and Non-Slender Beams

Prescriptive shear requirements in the U.S. from the American Concrete Institute (ACI) 318 (2019), the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) Bridge Design Specifications (2020), and the fédération international du béton Model Code ( fib MC) (2010) include a minimum web reinforcement requirement. In general, slender beams require a minimum area of web reinforcement equal to 0.08% of the cross-section, while non-slender beams require up to 0.30%, or roughly three times more than the slender beam requirement. This investigation aims to evaluate the discrepancy between these requirements in relation to the strength and serviceability behavior of experimental test data. This is carried out through an analysis of existing and peer-reviewed databases. The results show that the minimum web reinforcement needed to ensure shear strength is consistent with code requirements for slender beams, but not non-slender beams. The minimum web reinforcement needed to restrain crack widths is consistent with code requirements for non-slender beams, but not slender beams. Thus, the prescriptive web reinforcement requirements for slender and non-slender beams do not appear to be derived from the same criteria. The requirement for slender beams is derived based on these members achieving their predicted strength, while the requirement for non-slender beams is derived based on the width of in-service cracks.

Fatigue damage assessment of a large rail-cum-road steel truss-arch bridge using structural health monitoring dynamic data

Structural health monitoring (SHM) system provides valuable information for the fatigue assessment of existing rail-cum-road bridges. This paper aims to develop an effective fatigue assessment approach for the rail-cum-road bridge, Jiujiang Yangtze River Bridge, by utilising the SHM data, focusing on dynamic modal analysis, finite element model updating and fatigue assessment. First, the traffic load spectrum and modal characteristics of the bridge are investigated from the SHM data. A three-dimensional finite element model is constructed and then updated by using the measured modal data through the proposed regularised model updating method. Then, the updated numerical model is verified with the measured dynamic response data, which can be utilised for calculating stress response at critical structural components of the rail-cum-road bridge. Finally, an improved Corten-Dolan’s model is proposed to analyse the fatigue damage and structural reliability of the critical structural components of the bridge, taking into account the combined effects of train and highway vehicle loads. The results demonstrate that the proposed fatigue assessment method provides more reliable results for the rail-cum-road bridge by considering the combined effect of multi-level traffic loads and the non-linear fatigue damage accumulation. It is concluded that the short H-shaped suspender is identified as the most vulnerable structural member of the rail-cum-road bridge, and the remaining fatigue service life of the typical components of the bridge should meet the design requirement.

Hierarchical Bayesian modeling of highway bridge network extreme traffic loading

The road network consists of bridges of various lengths and configurations, all of which require accurate prediction of traffic load within their lifetime. However, current prediction methods are limited to modeling and predicting traffic load for a handful of individual bridges only; no method can simultaneously model and predict the traffic load of all bridges within an entire road network. Further, conventional models neglect the information that exists in the traffic load effect data established for different bridges, leading to large estimation uncertainties for each bridge and load effect examined. This study proposes a hierarchical Bayesian model that can estimate the traffic load effect of multiple bridges simultaneously, and subsequently create predictions for the remaining (unexamined) bridges within the road network. The proposed model is demonstrated using the traffic load data and influence lines used in the background study for the Eurocode 1 Load Model 1. The results show significant reductions in prediction uncertainties, better fits as measured by leave-one-out statistics, more robust fits against extremes, and the emergence of intuitive correlation structures between different bridges’ traffic loads that are absent in conventional models. This paper also presents a potential new strategy to reduce estimation uncertainty, and a method to predict parameters and return levels for bridges across an entire network made possible by the proposed hierarchical Bayesian model.

Advanced analysis of intact, fire-damaged, and CFRP retrofitted bridge pier columns under vehicle collisions: Empirical equivalent static force equation and framework

A series of numerical simulations were completed to investigate the behavior of intact, fire-damaged, and Carbon Fiber-Reinforced Polymers (CFRP) retrofitted reinforced concrete (RC) bridge columns of varying sizes subjected to vehicle collisions. Three-dimensional finite element models of isolated RC columns and their foundation systems surrounded by soil volumes were developed using LS-DYNA. A comprehensive parametric study was carried out to investigate the effects of nine demand and design parameters on the performance of bridge columns. Studied parameters included: column diameter, column height, unconfined compressive strength, steel reinforcement ratio, fire duration, CFRP wrap thickness, wrapping configuration, vehicle’s mass, and vehicle’s speed. For each studied scenario, Peak Twenty-five Milli-second Moving Average (PTMSA) was employed to estimate the Equivalent Static Force (ESF) corresponding to each vehicle collision scenario. Resulting ESFs were then utilized to assess effectiveness of the current ESF approach available in the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO-LRFD) Bridge Design Specification for analyzing and helping design bridge columns under vehicle collision. Multivariate nonlinear regression analyses were used to derive an empirically based, simplified equation to predict the ESF that corresponds to a vehicle collision. Rather than constant design force, this equation established a correlation between ESF and kinetic energy, column axial capacity, and column height. Results indicated that the proposed equation is reliable and can accurately predict ESFs over a diverse range of collision scenarios that included intact, fire damaged, and CFRP retrofitted columns. To facilitate realistic implementation of the derived equation, an ESF assessment framework was also devised.

Study of the Prediction of Vibrations in Soft Soil Foundations Based on Field Tests.

To explore the prediction of vibrations in soft soil foundations, in light of the construction of laboratories with microvibration requirements on soft soil foundations which are subject to the limitations of urban land planning, field testing was conducted, and the soil surface vibration responses were recorded at different distances from a road under various highway traffic loads. By analyzing the data which summarize the characteristics of soft soil foundations, it is clarified that the vibration response of soft soil foundations mainly occurs at low frequencies, and the vibration response under road traffic loads is prone to resonance at the natural frequency of soft soil foundations. Subsequently, a new vibration prediction method based on the vibration transmission ratio is proposed, and its effectiveness and accuracy based on transmissibility are verified. This research study provides a reference for laboratories constructed on soft soil and for surrounding traffic planning.

Study of Rail Structure Interaction on Double-Decker integrated bridge with Metro and Highway Structure

In the metro rail system, Long Welded Rails (LWR) have been used for less maintenance, smooth & safe ride at higher speeds. The arrangement of connecting rail and deck system causes an interaction effect in force transfer. The study of this effect in the structure is Rail Structure Interaction (RSI) analysis. In this study, the behavior of double-decker integrated structure, rail stresses and relative deformation are studied due to the bending behavior of the deck, bearing articulation & support stiffness with the proposed geometrical arrangement of the bridge and applicable loading as per standards. The effect of RSI analysis and limitations of additional stresses are referred with the guidance of UIC standards & RDSO guidelines. The double-decker elevated viaduct structure is proposed with a first level highway deck carrying highway loading and second level metro system carrying metro loading. In highway bridge deck, the decks are proposed with four span continuous to avoid discomfort due to more number of expansion joints and thereby provide smooth riding for passengers. The effect of RSI is studied in this paper by considering the above complexity of two-level superstructure with a different type of superstructure at the metro level due to the track requirement like U girder deck system at each track, I girder deck system as a single deck for both the tracks at the cross over / pocket track locations and I girder deck system at highway level with deck continuity. A finite element analysis is performed using the analytical tool MIDAS CIVIL software to study the interaction mechanism for this double-decker bridge structure. For this study, rail and deck (unballasted) are linked with a multilinear elastic spring as recommended in UIC 774-3R and other boundary conditions as per IRS & IRC standards. This paper discusses the behavior of structure from the results of the rail stresses and forces to the substructure due to thermal and live load effects at both level Metro Rail system and Highway Road systems.

Live load and long-term response of steel bridges with high skew

High skew in bridges alters live load distribution and creates performance issues such as deck cracking, superstructure in-plane (horizontal) displacements and bearing distress. In-plane superstructure displacements, also called racking, are particularly important as they cause misalignments of superstructure and approach slabs, stress bearings and expansion joints. This study had two objectives: to evaluate live load distribution in skewed bridges and to understand how skew influences in-plane superstructure displacements. The effect of bridge design details on live load distribution and in-plane superstructure displacements was assessed through parametric studies on highly skewed bridges.A three-span, steel girder-concrete deck bridge with a 47-degree skew was load tested. Load test results were employed to validate finite element analyses that were used to understand the impact of varying skew angle, bridge features and bearing fixity on live load distribution and in-plane superstructure displacements. The ability of the American Association of Highway and Transportation Officials Load and Resistance Factor Design Bridge Design Specifications (AASHTO LRFD BDS) to accurately capture live load distribution for steel girder bridges was evaluated.Field test results, consisting of girder bending and vertical shear strains measured through strain gages strategically located on one of the exterior spans, and parametric studies showed that AASHTO LRFD BDS predicted shear and moment distribution very conservatively and closely, respectively. Seasonal temperature changes were sufficient to create in-plane (horizontal) superstructure displacements. These displacements caused the superstructure to rotate towards obtuse and acute corners for negative and positive temperature changes, respectively. Larger skew angles led to greater transverse (i.e., perpendicular to bridge longitudinal axis) displacements at girder bearings. Longitudinal (i.e., parallel to bridge longitudinal axis) displacements were consistently smaller than transverse displacements and were not affected by skew. Mixed bearing fixity arrangements, with both fixed and expansion bearings over the same pier, limited superstructure transverse in-plane displacements.

Development of Improved Equations for Live Load Moment Distribution in Interior Girders of Shallow Steel Tub Girder Bridges

AbstractThe focus of this paper is the development of improved live load distribution factor (LLDF) prediction equations for interior beams of press‐brake‐formed tub girder (PBFTG) bridges. PBFTGs consist of cold‐bent standard plate widths and thicknesses to form a trapezoidal box girder. Based on a survey of literature and field testing performed on PBFTG bridges across multiple states in the United States, the empirical equations found in the American Association of State Highway and Transportation Officials Load Resistance and Factor Design Bridge Design Specifications (AASHTO LRFD BDS) have been found to be conservatively applicable to shallow steel tub girder bridges. Improvements can be made to AASHTO LRFD BDS provisions relating to shallow steel tub girders and their respective live load distribution factors (LLDFs). To overcome this gap in design and analysis, rigorous three‐dimensional finite element analysis tools were developed and benchmarked against field implementations. The tools were used to analyze the live load distribution behavior of an interior girder of a matrix of approximately 18,000 PBFTG bridges. From the result of the analysis, statistical methods were employed to produce simplified empirical equations to better predict live load moment distribution in PBFTGs. The simplified equations are to be used in conjunction with line girder analysis to further simplify the design of shallow steel tub girder bridges and expand their application in the short‐span bridge market.

Assessment of noise and vibration characteristics of Botryococcus braunii microalgae and hydrogen blends in internal combustion engines for highway vehicles

Extensive study has revealed biodiesel as a promising fuel obtained from a variety of sources, with its availability being a significant benefit. While biodiesel's performance and emission characteristics have been widely researched and proved suitable as a fuel, the most important aspects of noise and vibration characteristics in highway vehicles is remain unknown. In this study the effect of Botryococcus braunii microalgae on the four stoke diesel engine has been studied under the highway vehicle loading conditons. The biodiesel blends used in this study were B10% (10% of Botryococcus braunii biodiesel + 90% of pure diesel) and B20% (20% of Botryococcus braunii biodiesel + 80% of pure diesel). In addition to the biodiesel blends and neat diesel, the hydrogen was also supplied at the flow rate of 5 lpm. In order to avoid the backfire, flashback arrestor had been connected in the fuel inline manifold. The results obtained by using pure diesel were taken as reference and the biodiesel blend results were compared with them. A series of test conducted on the blends at five different loads of 0%, 25%, 50%, 75% and 100%. Sound pressure sensor and accelerometer were used to measure noise and vibration with respect to engine loads. Addition of hydrogen reduced the mass fraction in all blends, regardless of the fuel type. Hydrogen aids the combustion process thus there is an significant reduction in both highway vehicles engine noise and vibration has been noted irrespective of operating conditions. From the results, it is clear that the addition of hydrogen in both biodiesel and diesel showed a significant reduction in sound and acceleration. This finding supports the promising potential of microalgae blends as viable alternatives for highway vehicles.

Dynamic response of a multi-span suspension bridge subjected to highway vehicle loading

Dynamic response of a multi-span suspension bridge subjected to highway vehicle loading

Live Load Multiple Presence Factors for Design and Evaluation of Short-to-Medium Span Highway Bridges

The critical live loads in bridge design or evaluation could be caused by either a single vehicle event or simultaneous occurrence of two or more vehicles, which is usually called a “multiple presence event.” The multiple presence factors (MPFs) are then defined to assess the live load effects from single and multiple presence events. The MPFs from the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) were derived three decades ago, by assuming the probability of multiple presence events based on field observation. In addition, the correlation among truck loads in multiple presence events needs further evaluation based on actual data, as previous studies have assumed either fully correlated or independence across the lanes. There is an imperative need to re-evaluate the MPFs based on the available weight-in-motion data. This paper derives the MPFs for bridge live loads based on both traffic simulation and probabilistic modeling, utilizing existing weigh-in-motion data. It is found that the MPFs are affected by two major factors: truck loads and probability of multiple presence events. Truck loads can be further defined as the mean and standard deviation of loads on each lane, and the covariance of the load effects across the lanes. The probability of multiple presence events is related to average daily truck traffic, and the distribution of the traffic. The dispersion of truck volume and covariance of load effects across the lanes shows significant impact on the MPFs. Statistics of MPFs are obtained and recommendations to AASHTO LRFD are provided for 2-lane and 3-lane MPFs.

Experimental Study on Load of Continuous Steel Truss Bridge Stiffened by Rigid Suspension Cable for Highway and Rail

In order to reveal the stress law of rigid suspension stiffened continuous steel truss bridge under highway and crowd loads, a highway rail bridge is taken as the supporting project, and the load test method is used to verify it. Firstly, the completed bridge state (the dead load of the lower track) is simulated by laying water bags on the lower deck, which solves the problem of asynchronous construction of highway and track. Then, the stress, deformation results and change rules of this kind of bridge under the test load are summarized by simulating the load action of highway and crowd through the loading vehicle, which can provide a reference for the load test of similar bridges.

Rest Period Characteristics under Highway Truck Traffic for Mechanistic-Empirical Design of Asphalt Concrete Pavement

Fatigue cracking due to repeated truck traffic loads is the leading cause of failure of asphalt concrete pavement in many locations. Rest periods, referring to the time intervals between successive trucks, may allow for partial or full recovery from fatigue damage and in turn extend pavement fatigue life. This paper delves into the characteristics of rest periods between highway truck traffic loads using traffic data from 40 weigh-in-motion (WIM) stations installed on California state highways and evaluates their effects on pavement performance using mechanistic-empirical incremental-recursive damage and cracking simulation (CalME software). Toward this purpose, truck traffic data were extracted from these WIM stations at selected periods throughout the year 2015 to calculate rest periods. The probability distribution of rest periods and quantiles of cumulative rest periods were calculated, respectively. Regression and statistical analysis for 0.5 quantiles (median) of cumulative rest periods were also performed for different spectra groups and seasons. It was found that rest periods are strongly correlated with the truck traffic volume regardless of the WIM station location and seasons of the year. The actual rest periods based on the nonuniform truck traffic measured from the WIM data were found to be slightly shorter than the corresponding theoretical average rest periods for uniform traffic (ARP-UT) currently assumed in CalME, likely due to truck-following. This theoretical value assumes an equal time interval between trucks all the time. After comparing pavement performance with and without rest periods, it was found that rest periods have a significant influence (30% in difference) on pavement cracking performance in the modeling. Based on this preliminary analysis, the difference in pavement performance caused by the difference between the actual rest periods and ARP-UT is minimal. It is therefore recommended to continue to use ARP-UT to account for the effect of rest periods in pavement design.

Forecasting air quality index considering socioeconomic indicators and meteorological factors: A data granularity perspective

AbstractForecasting air quality index (AQI) is critically important to provide a basis for government policy makers, especially in public health, smart transportation, energy management, economic development, and sustainable environments. In reality, AQI consists of various components, such as PM2.5, PM10, CO, NO2, and SO2. Although numerous methods have been presented, few studies concurrently considered the causalities of socioeconomic indicators and meteorological factors and different data granularities. The aggregate AQI of Taiwan comprises five representative cities: Taipei, Hsinchu, Taichung, Tainan, and Kaohsiung. Research findings identify seasonal factors, carbon power generation, steel and metal production, highway cargo load, the number of registered cars, and retail and manufacturing employment population as the key indicators to predict the monthly AQI of Taiwan. For the daily AQI of Hsinchu and the hourly AQI of Kaohsiung, PM2.5, PM10, O3, ambient temperature, humidity, wind speed, wind direction, and pollutants (CO, NO2, and SO2) are recognized. Deep learning significantly outperforms machine learning in the hourly AQI while it performs slightly better in the daily AQI. With the presented framework, governments can balance the trade‐offs between economic development and environmental sustainability.

Static response of a multi-span suspension bridge subjected to highway vehicle loading

Static response of a multi-span suspension bridge subjected to highway vehicle loading

Reclassifying Fracture Critical Members (Non-Redundant Steel Tension Members) to System Redundant Members in a Steel Arch Bridge

The American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design Bridge Design Specifications define fracture critical members (FCMs) as steel primary members, which are subject to tension and whose failure would probably cause the collapse of a portion of or the entire bridge. FCMs not only lead to additional material procurement and fabrication quality requirements, but bridges with FCMs need to meet the requirements of special mandatory bi-annual hands-on inspections in additions to the routine planned bridge inspections per the National Bridge Inspection Standards. The special mandatory inspections for FCMs are a considerable budgetary constraint for asset owners while still not providing definite safety proofs within the period in between the inspections. Designation of FCMs should be carefully scrutinized in a new bridge constructed with high-quality materials and well-designed details. In 2012, the Federal Highway Administration published a memorandum introducing system redundant members (SRMs), which are identified through refined analysis and exempted from the inspection requirements for FCMs. A new AASHTO Guide Specification released in 2018 outlines a detailed procedure for the reclassification of FCMs as SRMs. This paper summarizes the analyses and results of a detailed FEA performed for a newly designed steel arch bridge. The analyses considered potential failure scenarios at the edge girder of the steel arch bridge and demonstrated the available redundancy in the system to distribute the loads by satisfying the performance criteria set forth in the AASHTO Guide Specification. Reclassification of the FCMs as SRMs could help the asset owner to reallocate their strained resources more efficiently.

Load Effect of Automated Truck Platooning on Highway Bridges and Loading Strategy.

Automated truck platooning (ATP) has gained growing attention due to its advantage in reducing fuel consumption and carbon emissions. However, it poses serious challenges to highway bridges due to the load effect of multiple closely spaced heavy-duty trucks on the bridge. In China, ATP also has great application prospects in the massive and ever-increasing highway freight market. Therefore, the load effects of ATP on bridges need to be thoroughly investigated. In this study, typical Chinese highway bridges and trucks were adopted. ATP load models were designed according to the current Chinese road traffic regulations. The load effects of ATP on highway bridges were calculated using the influence line method and evaluated based on the Chinese bridge design specifications. Results show that the load effect of ATP on bridges increases with the increase in the gross vehicle mass and the truck platooning size but decreases with the increasing inter-truck spacing and the critical wheelbase. The Grade-I (best quality standard) highway bridges are generally capable of withstanding the ATP loads, while caution should be exercised for other bridges. Strategies for preventing serious adverse impacts of ATP load on highway bridges are proposed.

Dynamic response of a beam to a train of moving forces driven by a translated Poisson process

Dynamic response of a beam to a random train moving forces driven by a so-called translated Poisson process is considered. The commonly used model of the counting process driving the random train of loads due to highway traffic is the Poisson process. Other, more adequate models of highway traffic loads are renewal processes, for example an Erlang renewal process (Ashton, 1966). In this paper the inter-arrival times of forces (vehicles) are assumed to have a translated (shifted) negative-exponential distribution. Such a renewal counting process, called a translated Poisson process, is known to be an adequate model of highway traffic (Haight, 1963). The problem is converted into that for modal responses by normal mode technique. In time domain approach the integral expressions for a mean value and the mean square of the response involve the renewal densities (Iwankiewicz, 1995; Jabłonka and Iwankiewicz, 2021). However, since for the translated Poisson process no exact solution for the renewal density exists, this renewal density is determined approximately, using a Gaver–Stehfest method (Gaver Jr, 1966; Stehfest, 1970). The mean value and variance of the response are determined by numerical evaluation of integrals and verified against direct Monte Carlo simulations. The results are also compared with those for a train of moving forces driven by a Poisson and by an Erlang process.