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The paper describes load and resistance factor design (LRFD) calibration for the resistance factor used in the Stiffness Method internal stability soil failure limit state for geogrid mechanically stabilized earth (MSE) walls. The Stiffness Method was recently adopted in the current American Association of State Highway and Transportation Officials LRFD Bridge Design Specifications in the US, and will appear in the next edition of the Canadian Highway Bridge Design Code. The paper describes the details of the calibration of the soil failure limit state which is unique to the Stiffness Method. Calibration outcomes include consideration of the concept of level of understanding in the selection of nominal load and resistance values which is unique to LRFD foundation engineering practice in Canada. A practical conclusion from these calculations is that if product line-specific creep test data are available to estimate the reinforcement secant creep stiffness used for design, then a resistance factor of 1.0 is reasonable for US practice. If only minimum average roll value tensile strength data are available, then a value of 0.95 is recommended for US practice. For Canadian practice, the corresponding values for typical level of understanding are 0.90 and 0.85, respectively. [ABSTRACT FROM AUTHOR]

In the 1950s and 1960s, some Louisiana's bridges were constructed using steel twin-girder or truss systems, in which floorbeams are carried by the main members and continuous (spliced) stringers are supported by the floorbeams. The main members are either two-edge (fascia) girders or trusses. One of the byproducts of this type of design is that stringer bottom flanges are in compression in the negative moment region over the floorbeams, which could result in lateral torsional buckling (LTB) should inadequate lateral bracing be provided. When the continuous stringers are load-rated using AASHTOWare Bridge Rating analysis software (BrR 7.1), their LTB resistance is calculated in accordance with American Association of State Highway Officials (AASHTO) LRFD Bridge Design Specifications, which do not account for potential bracing provided by a noncomposite deck and could underestimate flexural strength. As a result, the rating may be low enough to require restrictive load posting or even bridge closure. This paper summarizes extensive experimental and numerical studies investigating the behavior of this type of floor system by testing two-span, continuous, steel stringers in a grillage that included three stringer lines, an interior transverse support (floorbeam), and transverse diaphragms at the end supports. The tests and finite-element analysis studies encompassed a variety of unbraced lengths and support conditions with steel diaphragms or timber ties acting as bracing members. The findings demonstrated that, for the systems examined, minimal bracing could substantially enhance LTB resistance and supported the use of higher flexural strengths than those currently predicted using AASHTO Specifications. This paper illustrates the use, challenges, and successes in LTB modeling beams with various support and bracing conditions. The most flexible cases were the most difficult to achieve close agreement with experimental results. [ABSTRACT FROM AUTHOR]

Prestressed girders often deteriorate over time due to environmental and man-made stressors, lowering the strength and serviceability of bridge structures. Although structural repairs are implemented to improve the load carrying capacity of the structure, the presence of numerous unknowns leads to high uncertainty in estimating the adequacy of repairs. For instance, the cross-section of the remaining strands, material properties, applied external loads, and workmanship assumptions made throughout the repair process introduce ambiguities when estimating the adequacy of the repairs. This study evaluates the efficiency of re-tensioning repairs of prestressed concrete bridge span girders. The repairs include field splicing, re-tensioning, of deteriorated or damaged strands by torquing a splicing coupler. The evaluation in this study considers component, system reliability, and load ratings while accounting for several uncertainties, such as structural repair, material properties, and external loads. This paper introduces an approach to account for prestressing strands damage and repair uncertainties while also accounting for other uncertainties. In this regard, five cases are studied: as-built, repaired, and three varying degrees of damage cases. First, the distribution for structural demand and capacity accounting for uncertainty in loads, material properties, and repair process is defined for each girder in the prestressed concrete bridge span. In doing so, Monte-Carlo simulation is employed to determine the distributions. Accordingly, the limit state function of the girders is defined from the obtained distributions. Then, the component reliability of each AASHTO (American Association of State Highway and Transportation Officials) Type II girder is calculated from the obtained reliability indices based on the determined limit state functions. Finally, a system reliability model of the span is developed from the component reliability of each girder. Some advantages and disadvantages of using component and system reliability index versus load rating in damaged and repaired prestressed concrete bridge girders are also discussed. Several critical conclusions are made regarding the uncertainties in structural repair, material properties and external loads, and their impact on the load rating and the component and system reliability of the prestressed concrete bridge structure girders. [ABSTRACT FROM AUTHOR]

Highly-skewed steel I-girder bridges are commonly used across the US, especially in congested areas, despite complications in their analysis and design. The American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specification provides suggestions for design values of flange lateral bending stress in addition to line girder analysis when bridge skew exceeds 20° for certain cross-frame layouts. For bridges with skew exceeding 60°, a higher level of analysis is often required, with cross-frames considered primary members in design. Neither the magnitude of additional lateral stress nor the associated skew limits are particularly well understood, so more study is needed to refine and support this analysis and design approach. In addition to short-term response and load distribution, long-term bridge behavior for thermally induced stresses and deformations also needs to be more thoroughly studied. In support of an ongoing research initiative in Illinois, an agency survey was formulated and distributed across the US to understand practices used and challenges faced by state transportation agencies when designing and constructing skewed steel I-girder bridges. Findings from the responses of 23 state agencies illuminate issues, concerns, and current practice related to design, construction, and service life of those bridges. The agency survey informed selection of two bridges in Champaign, Illinois, for field monitoring, in order to provide new understanding of skew effects on bridge superstructure behavior. Three-dimensional finite-element analysis was conducted to guide field instrumentation planning, and initial measurements from the monitored bridges under traffic load confirmed good predictions compared to the planning-stage numerical study. This paper presents the initial stages of a long-term project that employs field monitoring and three-dimensional finite-element analysis of skewed steel I-girder bridges. Findings from a survey of state transportation agencies describe issues, concerns, and current practice related to design, construction, and service life of these bridges, which can be of interest to practicing engineers and contractors. This paper illustrates the integration of data from current practice and targeted numerical simulations to establish a rigorous basis for planning a bridge superstructure field monitoring campaign. The information and experiences summarized can be helpful to both practicing engineers and researchers. [ABSTRACT FROM AUTHOR]

Load testing of bridges is often used as a reliable method for assessing the capacity of in-service bridges with low analytical load rating factors. This paper presents a detailed load rating study of an 82-year-old concrete slab bridge with an unusually large aspect ratio of 3.73 by performing non-destructive diagnostic and proof load tests. The test-based modified rating factor is evaluated based on the American Association of State Highway and Transportation Officials (AASHTO) approach and the structural effective strip width approach which is then compared with the analytical rating factor from a simplified 1-D beam-line model. Field data is also used to evaluate the impact of the rotational stiffness of the bridge on its global response and load rating factor. The field test results based on the AASHTO approach reveal that the rating factor improves by up to 53% compared to the analytical rating factor. Monitoring the rotational residual response at the bridge supports is proven to be an effective method for assessing the global response of the bridge during field testing. The study shows that adding a rotational spring with a field-calibrated rotational stiffness to the 1-D analytical model of the bridge can significantly increase the load rating factor. [ABSTRACT FROM AUTHOR]

In some instances, cast-in-place anchors need a little extra tension capacity in concrete breakout. One method of increasing capacity is to add a bearing plate at the embedded end of the anchor to increase the base area where the breakout cracking initiates. ACI 318-19 has a procedure for increasing the breakout area in Section 17.6.2.1.3. The American Association of State Highway and Transportation Officials (AASHTO) bridge code also has a procedure to design the bearing plates for post-tensioning anchors. These procedures have the same objective but yield different results. To effectively increase the breakout area, the bearing plate must be stiff enough to uniformly distribute the bearing stress to the concrete. This paper describes the analysis of previously published concrete breakout test data and the implications the tests have on determining if the bearing plate is rigid enough to uniformly distribute the bearing stress to the concrete. [ABSTRACT FROM AUTHOR]

This paper presents a new tub girder series for Colorado, conforming to the articles of the American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications. Although the B618 tub girders developed by the Colorado Department of Transportation in the 1990s have been successfully used for decades, the need for an upgrade is essential to satisfy the requirements of contemporary bridge design and construction. After examining the performance of tub girders selected from six transportation agencies in the United States, an optimization algorithm was employed to generate efficient prototype sections. Then, detailed investigations were conducted to examine various practical aspects concerning the serviceability and ultimate limit states of AASHTO LRFD specifications. Parametric analysis with five bridge superstructures that accommodate up to four traffic lanes demonstrated the applicability of the prototype girders. A simplified version of the prototype sections was also delineated for regional precasters. Furthermore, a comparative study was carried out to evaluate the geometric stability and production costs of the prototype, simplified, and existing B618 girders. [ABSTRACT FROM AUTHOR]

This paper presents load factors for the residual capacity of highway bridges strengthened with carbon fiber-reinforced polymer (CFRP) composites. These load factors are intended to reflect structural loadings when a CFRP system malfunctions, so that a catastrophic event is prevented. To determine dead and live load factors under such an unordinary situation, stochastic inverse models are formulated per measure theory. Various bridge configurations and structural loadings are sampled from those used for calibrating the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (BDS). With an increase in span length over 18.3 m (60 ft), the dead load controls the response of the bridges relative to the live load. In accordance with inverse standard normal distributions, the live load effects are appropriate for representing service loadings (37.7% of the 75-year ultimate load effects, on average), which can thus be coupled with the residual capacity of the strengthened bridges. The most probable values are mathematically calculated to estimate the dead and live factors, and their influence is investigated on the moment and shear of the bridges. Analytical approaches, such as exceedance probability and safety index, substantiate that the calculated load factors outperform the load factors stipulated in a published design guideline. For the evaluation of residual capacity, the dead and live load factors are proposed to be 1.05 and 0.60, respectively. [ABSTRACT FROM AUTHOR]

Bridge damage and failure due to the effects of hurricane-generated storm surge is well documented. Over the past ten to fifteen years, research efforts have been undertaken to improve understanding of storm surge effects on bridges and explore how best to mitigate these effects. This paper documents development and assessment of a finite element analysis framework named AMBUSH that calculates forces applied to bridges subjected to storm surge loading. AMBUSH was shown to be capable of calculating reaction forces for a Biloxi Bay Bridge span for 14 storm events representing 5 storm categories. Simulation results compared favorably to American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications that were released relatively soon after Hurricane Katrina. Deviations of AMBUSH could be applied to other bridge or structural engineering problems with manageable reconfiguration. [ABSTRACT FROM AUTHOR]

This paper describes the characteristics of the new pavement design method developed by the American Association of State Highway and Transportation Officials (AASHTO), known as AASHTOWare Pavement-ME®, and presents the results of its application to the flexible pavement structures presented in the Portuguese Manual of Pavement Structures for the national road network. The results obtained clearly show that it is a very useful tool for road engineers not only for designing new pavement structures but also for the analysis of their performance and for efficiently planning maintenance and rehabilitation interventions. According to the characteristics of the case study that was considered, rutting is the most critical distress, since it presents values close to its threshold value of 20.0 mm, a value that is defined in Portuguese Quality Control Plans. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

In the bridge design specifications of the American Association of State Highway and Transportation Officials (AASHTO) using the Load and Resistance Factor Design (LRFD) method, the loads and resulting force effects are given two-letter designations, e.g. "SE" for "force effects due to settlement". The SE load factor is used to develop factored values of the induced force effects such as moments and shears in a bridge structure due to foundation movements. In 2018 AASHTO committees voted to adopt calibrated values of the SE load factors that account for the uncertainty in predicted foundation movements from different analytical methods. However, additional uncertainty can occur in the differential settlements. This paper explores the additional uncertainty in differential settlements of bridge foundations and retaining walls using the datasets for two analytical methods that were used by AASHTO to develop the SE load factors for foundation settlement. Normalised probability exceedance charts (NPECs), that integrate the concept of reliability index and data correlation, have been developed and their application in bridge and wall design process is discussed for a variety of scenarios. Guidance is provided for the practical implementation of differential settlement in bridge analysis through an example problem. [ABSTRACT FROM AUTHOR]

Drainage is one of the primary factors considered during the design of pavements. This paper presents the data from large-scale permeameter tests conducted on pavement sections to evaluate the drainage characteristic of geocomposite (GC) embedded subbase layers with and without traffic load. Two types of GCs with 2D core and 3D core were considered to enhance the drainage properties of a subbase layer. The large-scale permeameter test results indicate that the in-plane drainage capacity of the subbase layer improved by about 12 and 22 fold, respectively, for 2D−GC and 3D−GC. The GCs can drain infiltrated water at a rate of more than 300 m/day (in-plane permeability), even if the thickness of the subbase layer is reduced by about 50%. Over the pavement's design life, long-term in-plane permeability is estimated to decrease by 65–70%. It is estimated that the GC embedded subbase layers could drain off 50% of the infiltered water from a two-lane pavement system within 2 h, even after reducing the layer thickness by 100 mm. A set of new drainage coefficients for geocomposite improved subbase layers (m 3c) were proposed based on the American Association of State Highway and Transportation Officials drainage quality guidelines. • The study highlights the drainage characteristics of geocomposite-embedded subbase layers through a large-scale permeameter. • Even with a 50% reduction in the thickness, the geocomposite-embedded subbase layer could drain water at a rate > 300 m/day. • The in-plane permeability has decreased by about 20% under traffic loads. • A set of new drainage coefficients for geocomposite improved subbase layers (m 3c) were proposed. [ABSTRACT FROM AUTHOR]

Bridges are essential components of transportation systems and their unacceptable performance following a disaster may lead to disruption to relief operations. Many existing bridges all around the world were designed based on early editions of seismic codes and the performance of some old bridges following seismic events has revealed that they are seismically vulnerable. This paper provides a comparison of the seismic performance of reinforced concrete (RC) bridges designed according to recent code editions and according to earlier provisions. To this end, a probabilistic seismic safety assessment of RC bridges was conducted. Non-linear response history analyses were performed for each set of bridge samples subjected to earthquake ground motions with different severities employing three-dimensional models. The effect of the earthquake focal mechanism on the seismic vulnerability of the bridges was investigated. Moreover, fragility curves were developed for RC bridges designed according to the latest edition of the American Association of State Highway and Transportation Officials (Aashto) specifications (so-called new bridges) and those designed based on pre-1980 specifications (so-called old bridges). The fragility curves are presented in terms of the geometrical specifications of the bridges and the focal mechanism associated with input motions for both new and old bridges. [ABSTRACT FROM AUTHOR]

Local calibration is an important step before a transportation agency adopts the American Association of State Highway and Transportation Officials' (AASHTO) mechanistic-empirical pavement design guide (MEPDG). This paper presents the challenges of and findings from the local calibration of flexible pavements in provincial highways under the jurisdiction of the Ministry of Transportation of Ontario (MTO). A calibration database was developed that involved a hierarchical framework of the input parameters required for AASHTOWare Pavement ME (the MEPDG software) and the historical field performance data based on the MTO's second-generation pavement management system. A regression analysis is carried out for preliminary calibration of rutting and international roughness index (IRI) models by comparing the predicted distress to observed distress. The analysis suggested that whereas the MEPDG provided fairly unbiased prediction of the IRI value, it often over-predicted the total rutting. Calibrated predicted IRI and rut depth are found for Ontario's local conditions from MEPDG distress prediction models. A further clustering analysis based on Functional Class and geographical zone for the rutting and IRI, respectively, improved the precision of the locally calibrated models. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In 2009, a joint American Society of Civil Engineers Structural Engineering Institute and American Association of State Highway and Transportation Officials ad hoc group was created to study how current bridge practices could be improved for the future. Among their recommendations was the wider use of nondestructive evaluation (NDE) techniques. Risk-based planning to determine the appropriate inspection frequency, scope, intensity, and methodology would help make the increased time and costs associated with NDE inspections feasible for management budgets. However, a rigorous risk-based approach requires that the accuracy and reliability be quantified for each test. This paper serves as a starting point for quantifying these important variables and identifies the type of information that is still needed. Common NDE techniques were identified, and existing studies were reviewed to identify what data relevant to accuracy and reliability are currently available for these techniques. This review indicates that there is only a limited amount of quantifiable data available for most common NDE techniques for bridges, and not enough to statistically describe the uncertainty. [ABSTRACT FROM AUTHOR]

Owing to a severe shortage of natural aggregates in terms of quantity and quality, alternative aggregate resources must be utilized in civil engineering construction to meet significant increase in aggregate demand. This study focuses on manufacturing artificial aggregates for pavement applications using two waste materials- mine overburden waste from the coal mining industry and fly ash from thermal power plants. Liquid alkali activator, a mixture of sodium silicate and sodium hydroxide, is used as a binder. The centrifugal forces generated due to a rotating disc pelletizer enables mixing the said components resulting in formation of spherical-shaped pellets. The nucleated pellets are oven cured at 70°C for 7 days. Based on extensive laboratory test trials, the optimal features to produce competent aggregates in terms of angle and revolution speed of the disc pelletizer, dosage of the liquid alkali activator and the concentration of the NaOH are proposed. Finally, the manufactured aggregates are tested for properties relevant to flexible pavement applications. The aggregate impact and Los Angeles abrasion values are found to be 17% and 21.6%, indicating satisfactory resistance to impact and abrasion of aggregate particles under traffic loads. The basic material properties of these aggregates are found to conform to the Indian Roads Congress (IRC) and American Association of State Highway and Transportation Officials (AASHTO) standards for base and subbase layers. Moreover, base/subbase layers prepared with artificial aggregates and mine waste showed high California bearing ratio (CBR) of 54.3% and 80.5% for 2.5 mm and 5.0 mm penetration of the plunger, respectively, indicating high load-bearing capacity of pavement layers. [ABSTRACT FROM AUTHOR]

The current American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications' approximate formula for estimating long-term prestress losses is the outcome of the research work presented in National Cooperative Highway Research Program report 496. It is produced by simplifying the detailed method and taking into account the variability of concrete properties and the interaction between the precast concrete girder and cast-in-place deck. This paper presents two detailed parametric studies based on the average conditions for the design and construction of commonly used bridge girders. Three spans and, consequently, three levels of prestressing for each section have been considered. The first study establishes the creep multiplier Nc, whereas the second study evaluates the shrinkage multiplier Ns. Both multipliers are used in the lump-sum formulas for estimating long-term prestress losses for different bridge girders. The multipliers produced by these studies are compared with that of the current AASHTO LRFD specifications' approximate method, and new lump-sum formulas for long-term prestress losses are proposed. [ABSTRACT FROM AUTHOR]

Geotechnical data used for reliability-based design (RBD) and load and resistance factor design (LRFD) calibration can be parsed into subgroups based on material type, location, test method, and so on. Most often statistical analyses assume all data fall within a representative envelope, and pool (combine) all data into a single large data set without rigorously evaluating the veracity of this assumption. Adopting a Bayesian view, we introduce hierarchical/multilevel models as the more suitable alternative that takes into account multiple variation sources. Rather than assuming an identical parameter for data in all groups, hierarchical models assume exchangeable group-specific parameters, or informally, "similar but not identical" parameters. The utility of Bayesian hierarchical modelling is demonstrated by examining the accuracy of three reinforcement load models for polyester strap mechanically stabilised earth (MSE) walls and a simple hierarchical model as an example. We show that hierarchical models (i) have the customary complete pooling approach as their limiting case, (ii) quantify uncertainty from different sources of variation, (iii) prevent under-fitting, and (iv) can be used as tools for understanding the variations in the data. A simple RBD/LRFD example shows practical implications of hierarchical modelling of bias data. Finally, more complex/flexible hierarchical models are briefly discussed. Abbreviations: AASHTO: American Association of State Highway and Transportation Officials; ANOVA: analysis of variance; CDF: cumulative distribution function; CI: credible interval; COV coefficient of variation; DIC: deviance information criterion; LOGOIC: leave-one-group-out information criteria; LOOIC: leave-one-out information criteria; LM: load model; lppd: log pointwise predictive density; LRFD: load and resistance factor design; MCMC: Markov chain Monte Carlo; MSE: mechanically stabilised earth (wall); NHT: null hypothesis testing; PET: polyester; PGM: probabilistic graphical model; RBD: reliability-based design; WAIC: Watanabe-Akaike information criterion. [ABSTRACT FROM AUTHOR]

In the bridge design specifications of the American Association of State Highway and Transportation Officials using the Load and Resistance Factor Design method, the loads and resulting force effects are given two-letter designations, e.g. "SE" for "force effects due to settlement". The same two-letter designation is used as a subscript to distinguish load factors, γ, to be applied to loads and other actions acting on the bridge. Thus, the load factor γSE is used to develop factored values of the additional induced force effects such as moments and shears in a bridge structure due to foundation movements. This paper presents the process to calibrate the SE load factor as a function of the target reliability index based on structural service limit states such as cracking in a bridge superstructure. In this process, the target reliability index, uncertainty in predicted movements, and user-specified deterministic tolerable movements are considered in a unified manner. The calibration process can be used for any analytical method and any pattern of movement. The calibration process is demonstrated by an example of immediate settlement for five analytical methods using a dataset based on 20 instrumented spread footings from 10 bridges in the northeast USA. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) do not account for the presence of railings in the analysis or design of highway bridges. This paper presents a follow-up parametric investigation of the influence of railing stiffness on the wheel load distribution in simply-supported, one-span, three- and four-lane reinforced concrete slab bridges using the finite-element analysis (FEA). A total of 48 bridge cases are modeled using refined 3D FEA and bridge parameters such as span lengths, slab widths, and railings that were varied within practical ranges. Various railings stiffness were considered to be built integrally with the bridge deck and placed on both edges of the concrete slabs. The FEA wheel load distribution and bending moments are compared with reference bridge slabs without railings as well as to the AASHTO design procedures. According to the FEA results, the presence of railings reduces the longitudinal bending moment in the concrete slabs by 25% to 60% depending on the stiffness of the railings in one- and two-lane reinforced concrete bridges. However, when considering three- and four-lane bridges, the presence of railings reduced the longitudinal bending moment in the concrete slab by a range of 10% to 32% depending on the stiffness of railings. The results of this investigation will assist bridge engineers in better evaluating the load carrying capacities of multi-lane concrete slab bridges using 3D FEA and account for the contribution of railings. The presence of railings can also be considered a possible alternative for strengthening existing concrete slab bridges. [ABSTRACT FROM AUTHOR]

This study assessed soil pollution and index properties in Okpulor through geochemical, geotechnical, and geoenvironmental analyses. Twenty samples, comprising 14 surface and 6 shallow subsurface ones, underwent geochemical analysis for heavy metals (Fe, Cr, Cu, Zn, Ni, and Pb). Five geochemical indices, including the Geoaccumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), Metal Pollution Index (MPI), and Potential Ecological Risk Index (PERI), were utilized. Simultaneously, six subsurface samples underwent geotechnical analysis for Natural Moisture, Grain Size, Specific Gravity, Bulk Density, and Atterberg Limits, following Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) guidelines. The Igeo highlighted significant heavy metal contamination in Okpulor soils, particularly Cd. EF values exceeding 1.5 underscored a strong anthropogenic influence, with CF indicating Cd's substantial contribution to overall contamination. PERI underscored the ecological risks associated with Cd contamination. Natural moisture content, ranging from 18.21% to 21.45%, indicated a notable presence of water in the soil during the dry season, potentially leading to increased leaching and migration of water-soluble contaminants. Bulk density values suggested moderate to lightly packed soils, impacting porosity and permeability, and influencing contaminant movement. Atterberg limits indicated low soil plasticity, impacting moisture retention and contaminant behaviour. Grain size analysis revealed poorly graded soils with a close sand-to-clay ratio, affecting water drainage. These geotechnical properties and heavy metal contamination reveal the intricate interplay between soil characteristics and contamination risks in the Okpulor area, emphasizing the need for targeted interventions to safeguard the environment. [ABSTRACT FROM AUTHOR]

The present work aims to assess earthquake-induced earth-retaining (ER) wall displacement. This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels, reinforcement concrete facing panels, and gravity-type earth-retaining walls. The finite element (FE) simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses. The seismic performance of differentmodels, which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls, was simulated and examined using the FE approach. It also displays comparative studies such as stress distribution, deflection of the wall, acceleration across the wall height, lateral wall displacement, lateral wall pressure, and backfill plastic strain. Three components of the created ER walls were found throughout this research procedure. One is a granular reinforcement backfill, while the other is a wall-facing panel and base foundation. The dynamic response effects of varied earth-retaining walls have also been studied. It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls. The proposed analytical model's validity has been evaluated and compared with the reinforcement concrete facing panels, gravity-type ER wall, scientifically available data, and American Association of State Highway and Transportation Officials (AASHTO) guidelines results based on FE simulation. The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types. The methodology and results of this study establish standards for future analogous investigations and professionals, particularly in light of the increasing computational capabilities of desktop computers. [ABSTRACT FROM AUTHOR]

To address the shortcomings of traditional prestressed concrete girders, a new hybrid beam element, the Hybrid Deck Bulb Tee (HDBT) is proposed. The HDBT utilizes staged fabrication. First, the bottom flange is cast with Ultra-high Performance Concrete (UHPC) and prestressed prior to casting the web and top flange with High-Performance Concrete (HPC). The purpose of this study is to analytically evaluate the structural performance of HDBT beams for bridge structures. Multiple HDBT bridges were designed following the state-of-the-art criteria in regard to UHPC bridge design. The performance was evaluated using the following criteria: 1) the deflections under live load and dead load, 2) design checks for temporary stresses before losses, 3) stresses at serviceability limit states after losses, and 4) demand-to-capacity ratios under the American Association of State Highway and Transportation Officials (AASHTO) Strength I load combination. To obtain more refined results for the serviceability limit state, the bridges were modeled using a commercial finite element software. The model captured the time dependent material properties such as strength gain, creep, and shrinkage, as well as the stages of fabrication. The analysis demonstrates that the innovative design and fabrication processes of HDBTs are capable of resolving the current limitations of prestressed concrete elements. [ABSTRACT FROM AUTHOR]

Thermal cutting is a common engineering practice that is used to obtain the final shape of structural components. The characteristics of the cut surface and the material transformations caused by the cutting method determine the corresponding fatigue behavior. However, design codes, including the AASHTO LRFD bridge-design specifications, provide fatigue design curves for a limited number of situations. In the case of cut edges, only flame cutting is covered, whereas plasma and laser cutting are not associated to any category. In the case of cut holes, AASHTO specifications only consider the fatigue performance of drilled and punched holes, limiting the use of thermal cutting processes to, for example, produce bolt holes. All this restricts the use of thermal cut technologies in many applications. This paper analyzes the effects of flame, plasma and laser cutting on the fatigue behavior of cut edges and cut holes performed on structural steels. With this aim, an experimental program composed of 300 fatigue specimens has been completed. The obtained S-N results have been used to estimate the corresponding proposal of AASHTO detail categories. [ABSTRACT FROM AUTHOR]

Standard concrete creep prediction models are essential for structural design; however, it would be unrealistic to expect accurate prediction results without calibration and validations through experimental studies involving local materials and conditions. This paper reports on the long-term creep of high-strength concrete based on experimental work of six independent concrete mixtures involving three types of aggregate, where three mixtures of them incorporated 10% silica fume. Creep testing was conducted with consideration of standard guidelines for loading and strain measurements for up to 2.5 years. Creep coefficients computed from measured strains indicated a substantial influence of the silica fume and aggregate types. The study found that two of the examined models were capable of producing reasonable predictions of the creep for concretes without silica fume. On the other hand, the a current industry model showed reasonable prediction of the creep of concretes with silica fume while underestimating creep for concretes without silica fume. Finally, a mixed formulation model with features from two of the models is proposed and calibrated for concretes with or without silica fume. [ABSTRACT FROM AUTHOR]

Reinforced concrete short-span solid-slab bridges are used to compare Dutch and North American practices. As an assessment of existing solid-slab bridges in the Netherlands showed that the shear capacity is often governing, this paper provides a comparison between Aashto (American Association of State Highway and Transportation Officials) practice and a method based on the Eurocodes, and recommendations from experimental research for the shear capacity of slab bridges under live loads. The results from recent slab shear experiments conducted at Delft University of Technology indicate that slabs benefit from transverse force redistribution. For ten selected cases of straight solid-slab bridges, unity checks (the ratio between the design value of the applied shear force and the design beam shear resistance) are calculated according to the Eurocode-based method and the Aashto method. The results show similar design shear forces but higher shear resistances in the North American practice, which is not surprising as the associated reliability index for Aashto is lower. [ABSTRACT FROM AUTHOR]

E-ticketing was an intriguing technology to many state transportation agencies (STAs) pre-COVID-19 pandemic but gained significant attention upon arrival of the pandemic due to the contactless nature of the technology. Research completed prior to the pandemic into E-ticketing for asphalt paving primarily identified qualitative benefits and concerns. However, minimal academic literature exists in the postpandemic era discussing the additional E-ticketing benefits not previously captured which resulted in increased implementation by STAs. This research seeks to address this gap by gathering information from state members of the American Association of State Highway and Transportation Officials Committee on Construction (AASHTO COC), employees of the Kentucky Transportation Cabinet (KYTC), and members of the Kentucky Association of Highway Contractors (KAHC) and the Plantmix Asphalt Industry of Kentucky (PAIKY) regarding E-ticketing practices for asphalt paving in the postpandemic era. The first portion of the study combines national and state-level survey responses to create a qualitative benefit-cost analysis for E-ticketing for asphalt paving operations based upon experience gained through emergency implementation during the pandemic. To reinforce the results of the qualitative analysis and increase the power of the study, the second portion of the research creates a quantitative benefit-cost analysis (BCA) from data collected from KYTC construction projects to compare the traditional weigh ticket collection process with E-ticketing processes for both project engineers and inspectors. The analysis shows a statistically significant time savings for field employees but not project management personnel. The monetary analysis for Kentucky indicates that whereas E-ticketing does not result in significant time savings for all employees, there is substantial monetary benefit worthy of STAs adopting E-ticketing as policy. The primary contributions to the body of knowledge include an improved BCA methodology applied to a new domain of electronic bulk material tickets and an informed quantitative BCA framework useful for STAs as a proof-of-concept to champion E-ticketing implementation and by transportation-focused researchers for evaluating emerging technological applications. Previous research has focused on improving safety and task efficiency for field employees associated with asphalt paving operations. E-ticketing (electronic ticketing) has been proposed as an innovative technology to help augment typical tasks associated with asphalt paving. Before the COVID-19 pandemic, several state transportation agencies (STAs) had introduced pilot projects to study E-ticketing, but these yielded minimal policy adoption results. During the COVID-19 pandemic, many STAs pivoted to emergency usage of E-ticketing as the primary means of collecting information about asphalt material used on construction projects. This research compares previous qualitative analyses regarding the benefits and concerns associated with E-ticketing prior to the COVID-19 pandemic with lessons learned by STAs across the country after utilizing E-ticketing during the pandemic. Additionally, a case study focused on the Kentucky Transportation Cabinet (KYTC) is used to create a quantitative benefit-cost analysis from project-level data collected from various asphalt paving projects during the 2022 construction season. The findings indicate a statistically significant time savings for field employees utilizing E-ticketing and a benefit-cost ratio that promotes STAs adopting E-ticketing as a permanent policy. [ABSTRACT FROM AUTHOR]

With the development of bridge crossings over rivers, the accident of the vessel–bridge collision is increasing as well. It is important to assess probability of bridges colliding with passing ships. Firstly, the AIS (Automatic identify system) data was collected and decoded to obtain the dynamic information of the ships passing the bridge including the distributions of ships position, speed, and yaw angle, which are then compared with the value recommended by the AASHTO (American Association of State Highway and Transportation Officials) specification. The mainly influential parameters of ship–bridge collision obtained from AIS data are used to correct the variables in the risk assessment of AASHTO specification, which intends to improve the assessment accuracy by considering the actual information of passing vessels. The collision probability with and without considering the actual situations of passing ships are compared. It is found that the distribution and transit path of passing ships significantly influence the collision probability. To improve the risk assessment accuracy, it is suggested to use the actual distributions of passing ships from AIS data. [ABSTRACT FROM AUTHOR]

The friction coefficient resulting from the road surface condition directly affects the vehicle braking condition and distance. In the American Association of State Highway and Transportation Officials (AASHTO), the braking distance for different speeds, upgrades, and downgrades is recommended. However, the effects of the variations in the friction coefficient, type, and weight of vehicles are not directly taken into account. Therefore, the present study firstly examines the effects of the variations in vehicle speed, friction coefficient, longitudinal grade (upgrade and downgrade) in AASHTO 2018, and the vehicle type on braking distance. Secondly, a nonlinear analytical approach is considered to estimate braking distance and determine a critical friction coefficient that causes decreases in the braking distance. The findings indicate that under dry road surface conditions (with a friction coefficient of 0.6), the weight of the vehicle predominantly influences braking distance, resulting in heavier vehicles having shorter braking distances than lighter vehicles across all selected grades, except at a − 6%. However, when the road surface friction coefficient decreases from 0.6 to 0.18, the impact of vehicle weight surpasses the effect of the longitudinal grade, leading to an increase in braking distance. Consequently, when designing a road, it's essential to consider not only the technical road parameters and vehicle dimensions but also the vehicle weight and the road surface conditions in areas prone to snowfall, among other factors. If we wish to account for snowy and icy conditions, in addition to AASHTO's classification of wet conditions, in order to refine predictions of braking distance, the results of this study can provide valuable insights for road designers. [ABSTRACT FROM AUTHOR]

Serviceability limit state (SLS) refers to the condition under which a system (structure) is still considered functional and serviceable. The main contribution of this study is to develop a procedure to perform the reliability analysis for steel girder bridge deflections due to vehicular loading with the consideration of the serviceability limit state (service level II) according to the American Association of State Highway and Transportation Officials (ASSHO) load and resistance factor design (LRFD) of bridge specifications. In order to achieve this, the statistical parameters (mean and standard deviation of the bridge deflections) are updated based on the available weighin- motion (WIM) data (from several states across the United States) at different lifetimes. Two state-of-theart new approaches are introduced to determine the time-dependent statistical parameters; one of them is related to the probability papers and the other is related to the probability space (which is defined in this paper). Eventually, by taking advantage of the updated statistical parameters of the bridge deflections, the reliability analysis is performed to determine the target reliability for SLS, which was implicitly considered by AASHTO LRFD bridge specifications. [ABSTRACT FROM AUTHOR]

In this paper, the application of Endurance Time (ET) method to the seismic analysis of bridges is elaborated. ET method is a novel seismic analysis method based on time history analysis in which a structure is subjected to a predefined intensifying acceleration function. First, six concrete bridges were modeled in this study. Three Endurance Time Acceleration Functions (ETAFs) were applied to the models, and the average of responses was calculated. Next, the time history analysis was conducted using seven real accelerograms that are scaled using the method recommended by Federal Highway Administration (FHWA) to be compatible with the design spectrum of American Association of State Highway and Transportation Officials (AASHTO) guideline for a site with soil type C in Berkeley, California. The average of the responses of these analyses is considered as a reference. By scaling the mentioned accelerograms over a wide range of hazard levels, Incremental Dynamic Analysis (IDA) is performed. Finally, the comparison of the response of ET analysis and time history analysis and also the comparison of Endurance Time Analysis (ETA) and IDA curves revealed good agreement. The major advantage of ET method over time history and IDA methods is the need for less computational effort for performing the analysis. Such time efficiency was achieved due to the possibility of predicting responses by a smaller number of analyses despite maintaining the necessary accuracy. [ABSTRACT FROM AUTHOR]

This paper presents results of a database of interface shear experiments collected from the literature and analyzed to identify the main parameters affecting the strength of concrete-to-concrete interfaces subjected to shear loads and to gauge the reliability of major international codes and interface strength models. The database included 509 push-off and pull-off specimens, with steel reinforcement normal to the interface and subjected to monotonic pure shear loading. The experimental data were analyzed mainly in terms of interface type, clamping stress, concrete compressive strength, concrete unit weight, and steel strength. The analysis of the database revealed that clamping stress and interface type were the main parameters influencing the interface strength but that the concrete strength could play an important role as well. In contrast, it was found that the concrete unit weight appeared to have no effect on the interface strength. Of the code provisions considered, it was found that the American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications shear friction equations were the most accurate at predicting the interface strength for all interface types and conditions, while the PCI Design Handbook: Precast and Prestressed Concrete and American Concrete Institute's Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14) equations tended to underestimate the strength, with the PCI Design Handbook being generally more accurate than ACI 318-14. [ABSTRACT FROM AUTHOR]

The allowable level of temporary concrete compressive stress in precast, prestressed concrete components has been a source of debate in the concrete industry for many years. Traditionally, these stresses have been considered to originate only from the effects of prestress combined with the self-weight of a plumb component, evaluated about the major axis. The maximum compressive stress divided by the coefficient of the compressive stress limit determines the required concrete strength. Although these temporary stresses can occur at any time from fabrication through erection into the structure, the critical case is usually at transfer of prestress and subsequent lifting from the form. At this stage, the prestress force is higher and the concrete strength is lower than at any other point in the life of the component. At this early age, concrete is also more susceptible to damage from high compressive stress. As materials and fabrication capabilities in the precast, prestressed concrete industry advance, components are becoming longer and slenderer, particularly within the transportation sector. Such components require serious consideration of lateral stability during handling, which introduces bending about the minor axis. This lateral bending will increase maximum tensile and compressive stresses at the extremities of the component. These localized stresses traditionally have not been used to determine the required concrete strength, and doing so at current stress limits can significantly increase the required concrete strength. This paper is intended to reconcile the interaction between the temporary concrete compressive stresses traditionally used to determine the required concrete strength and the requirements for lateral stability, primarily the additional stresses due to lateral bending. The assumption is made that compressive stresses govern the determination of the required concrete strength. It is normally not efficient to determine the required concrete strength based on tensile stresses, which can be satisfied in a different manner. [ABSTRACT FROM AUTHOR]

The number of bridges in South Korea has almost tripled in the past few decades. Monitoring the structural behavior of these bridges is essential to maintain their performance in the infrastructure network and keep them in the best possible condition. The study presented in this paper aims to evaluate the Tun Bridge, located in Seoul, Korea. The bridge was tested under static and dynamic loads following the American Association of State Highway and Transportation Officials (AASHTO) standards. Twenty load cases and a wide range of truck speeds were applied during the bridge test. The bridge responses were captured using a short-period structural health monitoring system. Statistical analysis and signal processing for all the measurements were used to assess the structural behavior and fatigue life of the bridge. Bridge deformation/deflection and fatigue responses were evaluated. Furthermore, comparison with the available data from previous tests on the same bridge (17 years earlier) showed that the changes in static deflection and dynamic frequency were 13.87% and 2.73%, respectively. In addition, deflection and fatigue responses were found to be negligible under static and dynamic loads. Therefore, it was concluded that the bridge's behavior during its operational state was shown to be safe. [ABSTRACT FROM AUTHOR]

Link slabs provide continuity in the deck slab over the intermediate supports of multiple-span bridges where precast, prestressed concrete girders are used. Current practice recommends debonding the link slab from the girders' ends to reduce its stiffness. Steel reinforcement is consequently provided to satisfy the dead- and live-load criteria. A survey of bridges in the United States indicated that full-depth cracks still develop in the link slab and some practices are placing the link slab without debonding. Although design procedures for debonded link slabs are currently available, data related to bonded link slabs is scarce. This paper investigates the structural behavior of bonded link slabs due to dead and live loads. It examines the contribution of the stiffness of the link slab on redistribution of shear and moments. Closed-form solutions were derived for a three-span symmetrical case and a parametric study conducted based on standard American Association of State Highway and Transportation girders commonly used in the medium-span-length range. It was shown that the link slab parameters, if optimized, can strengthen the connection in the continuity zone to resist the induced loads without affecting its resisting capacity. [ABSTRACT FROM AUTHOR]

Piles provide a convenient solution for heavy structures, where the foundation soil bearing capacity, or the tolerable settlement may be exceeded due to the applied loads. In cohesionless soils, the two frequently used pile installation methods are driving and drilling (or boring). This paper reviews the results of a large database of pile load tests of driven and drilled piles in cohesionless soils at various locations worldwide. The load test results are compared with the static analysis design method for single piles recommended in the Canadian Foundation Engineering Manual (CFEM) and other codes and standards such as the American Association of State Highway and Transportation Officials, Federal Highway Administration, American Petroleum Institute, Eurocode, and the Naval Facilities Engineering Command. An improved pile design procedure is proposed linking the pile design coefficients (β) and (N t) to the friction angle of the soil, rather than employing the generalized soil type grouping scheme previously used in the CFEM. This improvement included in the new version of the CFEM 2021 produces a more unified value of the pile capacity calculated by different designers, reducing the obtained design capacity discrepancies. [ABSTRACT FROM AUTHOR]

This paper presents the development of a standard live load model for light rail bridges. It is recognized that the absence of a standard load model causes design outcomes varying from agency to agency, which is problematic from performance and reliability standpoints. A blend of deterministic and probabilistic approaches is employed to propose a new load model. Pursuant to light rail transit guidelines, benchmark bridges are designed (steel plate, prestressed concrete multicell box, reinforced concrete tee-beam, prestressed concrete I and bulb-tee, and steel box girder bridges). Finite element analysis is conducted to examine the response of the bridges when loaded by representative light rail trains operated in the United States (Colorado, Massachusetts, Minnesota, and Utah). Parametric investigations in conjunction with numerous loading configurations (48,256 model cases) characterize light rail train loadings, and corresponding results are exploited to determine the extreme bending moments and shear forces of the bridges at four probability levels (the average, upper 20%, 99.9%, and 75-year categories). The upper 20% model shows load effects similar to the standard live load model (HL-93) of the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (BDS). The 99.9% and 75-year models envelop the moments and shear forces resulting from the representative light rail trains. These candidate load models are further assessed against site-based load inference. The 75-year model is selected and proposed to be the standard live load model entitled LRT-16 (a uniformly distributed load of 14 kN/m plus three axles of 150 kN at a spacing of 4.3 m, which is configured similarly to those of HL-93 in AASHTO LRFD BDS). The applicability of the standard load model is evaluated using 33 light rail tra. [ABSTRACT FROM AUTHOR]

This paper examines the fatigue life of a Melt Shop crane girder with over 30 years of operation. Research indicates that the most frequent failures in these structures is related to fatigue in welded joints, thus an initial approach was performed according to AASHTO standard for calculating the remaining fatigue life of the structure. The alternating stress at the most severe loading conditions was obtained by numerical simulation in ANSYS software. Based on history and production forecasts, each critical welded joint fatigue life was determined. To calibrate the model, a field test was performed with strain gages to determine the real stress variation during regular plant operation. At this stage, crane load was parameterized in the computational model and varied to simulate the real behavior of the structure under the measured stresses. The analysis pointed out the most critical points which guided a visual inspection that identified cracks that could lead to a structural collapse. Identified crack growth was simulated through FRANC2D software that applies the LEFM method to determine the stress intensity factor. The calculated values were used to reach fatigue life for crack growth from an initial to a critical value which is expected to lead to a brittle fracture. It was concluded that the S-N method associated with finite element analysis has proven to be an efficient technique for determining the most critical structure joints damage reducing inspection work significantly. The application of linear elastic fracture mechanics techniques reached more conservative results. This technique can assist the maintenance crew in determining inspection intervals and the best moment for intervention to repair existent cracks based on the calculated remaining life. [ABSTRACT FROM AUTHOR]

There has been considerable progress in reliabilitybased code development procedures. The load and resistance factors in the 2014 edition of the American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications were determined using statistical parameters from the 1970s and early 1980s. Load and resistance factors were determined by first fixing the load factors and then calculating resistance factors. Load factors were selected so that the factored load corresponded to two standard deviations from the mean value, and the resistance factors were calculated so that the reliability index was close to the target value. However, from a theoretical point of view, the load and resistance factors should be determined as coordinates of the design point that corresponds to less than two standard deviations from the mean. Therefore, the optimum load and resistance factors are about 10% lower than those specified in the AASHTO LRFD specifications. The objective of this paper is to revisit the original calibration and recalculate the load and resistance factors as coordinates of the design point for the Strength I limit state. The analysis was performed for the same types of girder bridges--reinforced concrete T beams, prestressed concrete girders, and steel girders--as in the original calibration presented in the 1999 National Cooperative Highway Research report 368, Calibration of LRFD Bridge Design Code. The recommended new load and resistance factors provide consistent reliability and a rational safety margin. [ABSTRACT FROM AUTHOR]

The current editions of the American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications and ACI 318-14 are based on years of experimental research and use the traditional 270 ksi (1860 MPa) prestressing strand. Recent developments have resulted in a higher-strength strand with an ultimate tensile strength of 300 ksi (2070 MPa). This paper presents the results of an experimental investigation looking at the behavior of pretensioned, prestressed concrete members containing 300 ksi prestressing strands. Eighteen T-beam test specimens were fabricated and used to evaluate the effects of using the higher-strength strand on transfer and development lengths as well as flexural capacity and ductility. The results from 35 transfer zones and 35 flexural tests are compared with a variety of known influential factors and the current code provisions for transfer and development length and nominal moment capacity. The results are also evaluated with respect to the tensile strength of the strand. [ABSTRACT FROM AUTHOR]

With the recent American Association of State Highway and Transportation Officials bridge design code acceptance of cold bent fracture-critical and nonfracture-critical plates and the increasing use of cold bending by the bridge industry, there is a need to better understand and predict residual strains in cold bent steel. However, measuring residual strains is a challenging task since the bending process typically interferes with conventional instrumentation. This paper introduces three-dimensional Digital Image Correlation (DIC) as a new, non-destructive approach to measuring residual strains in cold bent steel that captures full-field strain data with high accuracy. DIC was used to measure residual strains in 18 cold bent 12.7 mm thick ASTM A36 steel plates, bent using a press-brake to a constant radius of 102 mm with varying angles (10, 20, and 30 degrees) and plate widths (76.2 mm and 203 mm). The measured residual strains are compared to analytical predictions and both two- and three-dimensional finite element models. A parametric study, using the validated finite element models, is completed for additional widths (12.7 mm and 140 mm) and thicknesses (6.35 mm and 19.1 mm) to investigate the effect of these parameters on circumferential strains, contact pressure, strain state, and to make modeling recommendations. Results are used to develop a means of predicting peak residual strains based on the final plate dimensions - a useful quality control measure. [ABSTRACT FROM AUTHOR]

This study presents the use of V-M interaction diagrams to estimate the ultimate shear and moment demands of reinforced concrete (RC) beams. The method of analysis presented can be beneficial for both design and analysis as it provides a visual aid for gaining clearer insight into the determination of the maximum load-carrying capacity of a considered section, as well as its failure mode. To simplify the construction of such V-M interaction diagrams and remove the often-needed iterative procedure, the current American Association of State Highway and Transportation Officials (AASHTO) shear sectional design model based on the Modified Compression Field Theory (MCFT) was modified. As a result, the simplified process uses the strains of flexural reinforcement and moment demands at three events, which can be obtained by a simple elastic analysis. The maximum shear strengths were predicted for 1012 RC beams without transverse reinforcement using two current AASHTO shear design methods and the proposed simplified method. Overall predictions at failure from the V-M interaction diagram approach for all three methods showed great agreement with the test results with a reasonable coefficient of variation. Further investigation of the experimental variables revealed an overly conservative trend in beams with smaller effective depth and a/d ratio due to insufficient consideration of size effect and arch action. The noticeable trend by a/d ratio was somewhat moderated in the proposed method. Although the proposed method showed the most accurate predictions compared to the two AASHTO methods, an unconservative aspect existed for many cases so that a strength reduction factor of 0.75 was suggested. Also, the current strength reduction factor of 0.9 in AASHTO for shear was evaluated and considered appropriate. Given the satisfactory performance in estimating the maximum shear capacity, the proposed simplified AASHTO method using the V-M interaction diagram can serve as an alternative shear strength design and analysis method for slender RC beams. [ABSTRACT FROM AUTHOR]

Plastic waste (PW) constitutes a nuisance to our environment despite several efforts to reduce, reuse and recycle it. This study experimentally explores the possibility of storing plastic waste within a cement-stabilised soil that can be used as a road pavement layer material without adversely affecting the geotechnical characteristics of the stabilised soil. The soil is an A-2-6 soil, according to classification by the American Association of State Highway and Transportation Officials (AASHTO). Compaction characteristics, the California bearing ratio (CBR) and the unconfined compressive strength (UCS) of soil with 10% cement were determined for the 0, 2, 5, 10 and 15% addition of PW. The cementing of soil particles, which played a vital role in enhancing its strength on the addition of cement, may have been activated by the pozzolanic reaction between cement and soil particles. However, the addition of PW to this cement-stabilised mix led to a decrease in strength parameters at all variations. The soil with 10% cement and 2% PW yielded higher strength when compared to other mix ratios with PW and is suitable for use as a layer material in road pavement construction. As a sustainable strategy for PW management in developing nations, the usage of PW in cement-stabilised soil layer is recommended. [ABSTRACT FROM AUTHOR]

The practice of designing load-bearing walls with stabilized earth-based material is currently increasing in most developed countries. Potentialities of earth-based materials have room for more exploration, investigation, and promotion among building industry stakeholders globally. This research aims to analyze the compressive strength and durability of "Hamrah" Soil to assess its fitness in construction. Such a study is intended to get international and local (Saudi Arabia) construction practitioners' confidence about soil usage in the construction industry. To achieve this goal, sufficient soil material was procured from the Al-Hofuf region in eastern Saudi Arabia. Several geotechnical experiments were carried out to characterize and identify Hamrah Soil properties. The soil samples were classified in adherence to both the Unified Soil Classification System (USCS) and the American Association of State Highway and Transportation Officials (AASHTO) system. Stabilizing agents (cement and lime) were added at different percentages (0, 2.5, 5, 7.5, 10, 15% of the dry soil weight) to enhance their structural properties. Based on the acceptance criteria of 2 MPa strength, more than 5% cement maximized the stabilized rammed earth (SRE) sample strength more than 2 MPa (up to 6.3 MPa at 15% cement content), whereas 10% lime reached only1.46 MPa, which proved the efficiency of cement stabilization over lime. Micro-characterization techniques utilizing XRD, SEM, and durability tests also lent credence to the effectiveness of cement in the stabilization regime, giving more fibrous formations and a reduction in weight loss below the acceptable limits compared with the case of lime stabilization. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced polymer (CFRP) materials are an alternative to steel reinforcement and prestressing strands in harsh climates because of their noncorrosive nature, durability, high tensile strength, and light weight. This paper discusses the use of CFRP in bridges in the form of carbon-fiber-composite cable (CFCC). CFCC's unique performance influences the design requirements of members with CFCC reinforcement. The American Association of State Highway and Transportation Officials and Michigan Department of Transportation are developing guidelines that will help highway transportation agencies make decisions about the use of CFRP for prestressed concrete bridge beams. [ABSTRACT FROM AUTHOR]