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Experimental tests of cross-laminated timber (CLT)-concrete composite floor panels were conducted. The tests consisted of linear-elastic tests of square CLT-concrete composite panels with a novel shear connector to determine elastic orthotropic plate properties. After the linear-elastic tests, the panels were subjected to a patch load at the center of the panel and tested to failure. To investigate load transfer across longitudinal joints between adjacent panels, nonuniform bending tests were conducted. Results from the experimentally measured orthotropic plate properties showed that the shear connector increased the bending stiffness in the weak direction of the panel compared to prior test results using conventional shear connectors. The tests to failure exhibited larger differences in behavior between the strong and weak orientations of the specimens, with both showing substantial inelastic behavior prior to failure. Numerical finite element models of the patch-load test showed good agreement with experimental results. Analytical formulas using the obtained orthotropic plate properties did not agree with experimental results for the patch-load at linear scales, suggesting the simplified method is currently not suited for CLT-concrete two-way bending. Load-transfer tests found that the reinforced concrete topping is capable of transferring load across the longitudinal joint of two parallel panels to enable two-way bending of composite timber–concrete floors and that the addition of a plywood spline with closely spaced screws enables a higher degree of force transfer. [ABSTRACT FROM AUTHOR]

Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90° and 45° orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws. [ABSTRACT FROM AUTHOR]

While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes. [ABSTRACT FROM AUTHOR]

New building code changes enable mass timber panels (MTP), including cross-laminated timber (CLT), to be used in moderate and tall buildings as a floor system, usually with a concrete topping. A floor system of CLT composite with a reinforced concrete topping slab can provide increased stiffness and strength, making the system more advantageous. Present connection methods used to produce composite action within timber-concrete composites (TCC) have limitations when considering constructability or performance. This study presents experimental results from four (4) shear connectors for CLT-concrete composite floor systems, including three developed for this study. The connectors included self-tapping screws (STS) at 45-degrees, a modified lag screw with an integral plate washer that bears on the CLT surface at installation, a steel angle anchored only at the end of the span, and an inverted-T steel section with stem perforations. Different tests were performed on the different connectors including individual fastener tests, push-off group tests, and full-scale one-way bending tests. The push-off group tests showed that the proposed washer-screw exhibited higher stiffness and strength than a conventional STS. The full-scale one-way bending testing showed that the STS specimen exhibited the lowest strength of the alternatives. The inverted-T section exhibited the highest stiffness, while the other three connections had similar stiffness to the STS. [ABSTRACT FROM AUTHOR]

The cyclic performance of substandard reinforced concrete (RC) bridge substructures seismically retrofitted using titanium alloy bars (TiABs) is assessed using full-scale experiments and nonlinear numerical models. The retrofit technique uses TiAB ligaments to simply and effectively strengthen columns with inadequate flexural lap splices and provides confinement through hoop action when combined with continuous TiAB spirals. The failure characteristics, flexural ductility, and hysteretic behavior of unretrofitted substandard (i.e., vintage) and TiAB retrofitted columns were evaluated using quasi-static, reversed cyclic tests of full-scale bridge column–footing specimens modeled after the characteristics of highway bridges in Oregon constructed prior to the introduction of seismic design provisions. Foundation rocking was examined and quantified through implementation of a soil subgrade simulant. Experimental results demonstrate improved flexural response and ductility with reduced concrete damage and residual drifts of RC columns when retrofitted with TiAB. The measured responses of the test specimens were used to calibrate three-dimensional (3D), nonlinear, finite-difference models used to investigate the effect of soil–structure interaction (SSI) on the rocking moment capacity for as-built and retrofitted column–footing specimens. The model was then used to perform a parametric study to evaluate retrofit details (flexural strength and stiffness) and soil characteristics (strength and stiffness) and their relationships to engineering demand parameters such as displacement and strength, which indicated that incorporation of SSI will permit the design of more efficient and economical seismic retrofits. [ABSTRACT FROM AUTHOR]

Transportation agencies expend large amounts of money annually to maintain highway wearing surfaces. Wear depends mainly on axle weight, vehicle speed, temperature, surface type, and the type of tires mounted on vehicles. When studded tires are used, wear is increased significantly. Past studies on the use of studded tires have highlighted the need for a tool to better estimate the number of vehicles with studded tires that travel a road network. Currently, there is no such tool available. This paper presents a detection methodology using acoustic emission techniques to identify vehicles operating with studded tires. Data from an in-service test on a highway bridge were used for developing and evaluating two proposed detection schemes. It was found that using relatively simple detection algorithms, vehicles with studded tires could be discriminated reliably. Finally, a practicable integrated system is proposed that could be implemented for detection and monitoring of studded snow tire use on highway systems. DOI: 10.1061/(ASCE)TE.1943-5436.0000062 CE Database subject headings: Tires; Vehicles; Probe instruments; Monitoring; Bridges; Highway. Author keywords: Studded tires; Acoustic Emission; Monitoring; Real-time detection; Highway bridges.

Tests were performed on full-size prefabricated steel stair assemblies to assess seismic interstory drift response combined with factored gravity loads. The stair assemblies were production-run units of a standard system and were designed for a typical steel frame building. Two different stair assembly units were tested: one with checker plate and one with concrete-filled pans. A loading system and testing protocol were developed to evaluate the seismic performance using seismic and gravity load combinations. Lateral drifts were imposed in both orthogonal stair directions followed by factored live and dead gravity loads. Imposed lateral drift placed high deformation demands on the stair-to-landing connections and overall performance is dependent on the deformability and endurance of these connections. Careful detailing, fabrication, and inspection of the stair-to-landing connections are required to ensure desired system performance. DOI: 10.1061/(ASCE)0733-9445(2009)135:2(122) CE Database subject headings: Stairs; Seismic design; Seismic tests; Gravity loads; Combined loads.

A bridge rating application is developed using the Tool Command Language (Tel) scripting language in conjunction with the OpenSees finite-element software framework. Fully programmable and string based, Tel is ideal for implementing live load analysis through scripts and experimenting with emergent bridge rating methodologies. Since Tel is an interpreted language, the application also has the important advantage that new bridge capacity models and rating factor calculations can be implemented quickly by a user without compiling source code. The rating application is demonstrated on a conventionally reinforced concrete bridge girder. The use of OpenSees for finite-element analysis makes the rating application readily extensible to nonlinear structural response and advanced structural reliability methods for a variety of a bridge types and structural components. CE Database subject headings: Bridge maintenance; Computer aided simulation; Computer programming; Live loads; Ratings; Structural analysis.

Bench-scale experiments were performed to evaluate poly- and perfluoroalkyl substance (PFAS) desorption from vadose zone soils collected at a site historically impacted with aqueous film-forming foam (AFFF). A sequential dilution batch method was employed to obtain PFAS desorption isotherms from a shallow surface soil [0.03 to 0.9 m below ground surface (bgs)] and from a deep soil (0.9–2.4 m bgs). Results showed that the desorption isotherms were reasonably described by a linear model, and that a fraction of the soil-bound PFAS mass was not readily desorbed (or, non-labile); the recalcitrance of this non-labile fraction was evaluated on a subset of samples and shown to persist for up to 9 months. The non-labile fraction of PFAS mass sorbed to the soil (non-labile PFAS sorbed mass divided by the total PFAS sorbed mass) ranged from 0.17 g g−1 for perfluorohexane sulfonamide in the deep soil to 0.87 g g−1 for 8∶2 fluorotelomer sulfonate in the shallow soil, and generally increased with the PFAS organic carbon:water partitioning coefficient (Koc). The fraction of the PFAS within the non-labile fraction was generally greater in the shallow soil than in the deep soil, likely due to the elevated organic carbon content of the shallow soil. The slopes of the desorption isotherms associated with the readily-desorbable (labile) PFAS fraction for the shallow soil were within the ranges predicted by Koc -based models derived from adsorption data. Overall, results for the soils studied herein suggest that much of the PFAS mass present in the soil likely is not readily available for leaching into infiltrating waters. Such information could provide useful insight for developing PFAS soil cleanup standards. [ABSTRACT FROM AUTHOR]

The ability of shallow bridge foundations to dissipate earthquake energy via rocking has gained significant attention by bridge engineers owing to recent efforts to quantify the performance of rocking footings. This paper presents a new formulation for estimating the moment capacity of rocking bridge foundations resting on all types of soils under varying saturation and surface flux boundary conditions. The proposed formulation uses the moment capacity equation originally employed for saturated soils, classical effective shear strength parameters, and a representation of the soil–water retention curve (SWRC) to accommodate partially saturated conditions that may commonly exist below the shallow foundations of bridge substructures. A closed-form equation is incorporated in this formulation for the matric suction and effective saturation profiles to directly implement surface flux boundary conditions when analyzing the moment capacity of rocking foundations supported on partially saturated soils. The formulation implements a new method to predict the air entry suction for partially saturated soils, representing a key step towards improving the accuracy of moment capacity. A parametric study is performed to investigate the sensitivity of the moment capacity to primary design variables and various surface flux boundary conditions. The analyses demonstrate that flow conditions have a negligible and strong influence on the moment capacity of coarse- and fine-grained soils, respectively. Predictions from the proposed formulation were compared against two sets of experimental data obtained from large-scale shaking table (on sand) and snap-back (on plastic silt) tests and indicated good agreement with experiments. [ABSTRACT FROM AUTHOR]

A full-scale 2-story mass timber building was tested on the University of California San Diego Natural Hazards Engineering Research Infrastructure (UCSD-NHERI) uniaxial shake table during the period from June 2017 to September 2017. The main objective of the experimental program was to test the performance of mass timber building designs with different seismic lateral force–resisting systems. The focus of this study is on a building configuration designed using self-centering post-tensioned cross-laminated timber (CLT) rocking walls with U-shaped steel flexural plate energy dissipators. The shake-table tests were designed to subject the building to a series of earthquake ground motions of increasing intensity, ranging from a service-level earthquake to 1.20 times the maximum considered earthquake intensity. Between each ground motion, low-amplitude white-noise excitations were applied to the building, which responded as a quasilinear system. In this paper, two output-only operational modal analysis methods are used to estimate the modal parameters (frequency, damping, and mode shapes) based on acceleration data collected during the white-noise shake-table tests. The correlations of observed damage and repairs performed during the experimental program with changes in estimated modal features are reported. The modal parameters estimated from the testing program are also compared with a linear finite-element model that is used to validate the modal identification results and study the performance of the two system identification methods for CLT rocking structures. [ABSTRACT FROM AUTHOR]

This paper presents the behavior of floor diaphragms of a shake-table experiment of a full-scale 2-story mass-timber building structure. The structure consists of glued-laminated timber beams and columns, and floors and walls were designed and built making use of cross-laminated timber panels. Two different floor systems were designed, where the roof consists of a topped cross-laminated timber (CLT)-concrete composite system, and the floor level consists of untopped CLT panels connected with plywood single-surface splines. The CLT floor systems were designed to remain essentially elastic over the whole series of shake-table tests, which included testing of three lateral force–resisting systems tested at three different seismic intensity levels (service level, design basis, and maximum considered earthquake) for a total of 34 shake-table earthquake tests. Results from the testing indicate that CLT diaphragms designed to remain essentially elastic based on basic principles of structural mechanics and existing test data can achieve desired seismic performance objectives. In addition, sources of overstrength in certain elements of the diaphragm need to be explicitly considered for a holistic diaphragm design. [ABSTRACT FROM AUTHOR]

Bench-scale experiments were performed to measure and evaluate the desorption kinetics of poly- and perfluoroalkyl substances (PFAS) from a vadose zone soil exposed decades ago to aqueous film-forming foams (AFFFs). Desorption kinetics in the shallow zone (0.03–0.9 m below ground surface) that contained an elevated organic carbon (OC) content, and in an underlying deep zone (0.9–2.4 m below ground surface) that contained a relatively low OC content, were evaluated for a wide range of anionic and zwitterionic compounds. Results showed that, for a given perfluorinated chain length, the head group impacted desorption. For the low-OC deep soil, desorption equilibrium generally occurred rapidly (within 48 h), indicating that mass transfer limitations were minimal. However, for the high-OC shallow soil, less-hydrophobic and short-chained compounds (including C<8 for the perfluorinated carboxylates, and C<7 for the perfluorinated sulfonates) generally did not reach equilibrium within 400 h , whereas longer-chained and more-hydrophobic PFAS appeared to reach equilibrium within 48 h. Kinetic desorption modeling revealed that these observations likely were due to the depletion of shorter-chained PFAS in the rapid equilibrium sorption domain, coupled with their persistence in the kinetically controlled sorption domain. Kinetic modeling also showed that the rate of desorption was proportional to the PFAS aqueous diffusivity, confirming that diffusion limited the rate of release from the soils. Overall, the extent of desorption generally was substantially less than that predicted by published Kocfoc relationships, suggesting that PFAS desorption from field-aged soils may have a less pronounced impact on underlying groundwater than anticipated, particularly for shorter-chained PFAS. [ABSTRACT FROM AUTHOR]

Designing structures resistant to tsunami-like flood flow impacts is contingent on the ability to accurately predict dynamic loading effects on building components. To characterize these effects, two metal building cladding subassembly test specimens, designed for Risk Category II and Category IV wind loading, were experimentally subjected to surges and bores with various wave height and initial water levels. The results reveal that maximum structural responses, quantified by curvatures and displacements, occur after initial wave impact, as splash up on the structure subsides. Furthermore, consistent pressure–time histories between specimens in equivalent flow conditions, despite significantly different strains and displacements, suggest structural flexibility does not influence which wave forcing produces the maximum structural response. Lastly, structural analysis of the specimens, based on measured pressures at maximum strain conditions, reveals that loading conditions ranged between hydrostatic and hydrodynamic depending on the initial flooding conditions. With these findings, a method to predict pressure magnitude and distribution on the cladding at the time of maximum structural response for tsunami-like flood flow impacts is proposed. [ABSTRACT FROM AUTHOR]

Ecoroof systems are proliferating to meet the need for reducing peak storm discharge and improving habitat in urban environments; however, no coherent set of standards exists for the engineering of these systems. Necessary questions that remain regarding engineering performance range from hydraulic to structural to geotechnical in nature, as exemplified in a series of recent ecoroof failures. As a first step, this paper describes a field exploration and laboratory characterization program conducted to develop a necessary geotechnical engineering baseline for ecoroof soils currently used with sustainable green-roof technologies. A series of low-stress (i.e., 10-30 kPa), static drained, simple shear tests were conducted on both reconstituted and relatively undisturbed specimens derived from three target gradations. The volumetric response of the undisturbed specimens exhibited contraction, and developed significantly larger magnitudes of volumetric strain than that of the reconstituted specimens, which exhibited a range in shear strain-dependent volumetric responses. The mobilized friction angle of the ecoroof materials ranged from approximately 37 degrees to 65 degrees, and varied as a function of organic content, normal stress, gradation, and relative density. The results show that the organic content has a significant effect on the stress-strain and volumetric responses of ecoroof soil in the field, which indicates that ecoroof design codes and standards are needed. [ABSTRACT FROM AUTHOR]

The strength and behavior of large-diameter reinforcing steel bars with straight anchorages were experimentally investigated. The anchorage details are typical of monolithic girder-column connections used in bridges and buildings in the midcentury. Eleven subassemblage column specimens were examined with different anchorage lengths, bar groupings, amount of transverse steel, and externally applied column axial forces. Test results showed an increase in anchorage capacity because of the presence of transverse steel and externally applied axial force. Experimental results were compared with contemporary design specifications which do not currently account for the beneficial effects of column axial compression acting transverse to the splitting plane. A modification factor was developed to account for the presence of active force applied transverse to the splitting plane to determine anchorage capacity that better estimated the available capacity of the anchorages. [ABSTRACT FROM AUTHOR]

Long and torsionally slender H-shaped cross sections, often used as tension members in truss bridges, can exhibit wind-induced torsional motions. These motions have produced high-cycle fatigue damage for some bridges. There is limited information available to evaluate the torsional response on the fatigue performance of themembers and connections. An in-service bridge with a documented history of wind-induced torsional motions in the verticals was instrumented to capture the wind speed and direction that induced torsional motions in the verticals. Sensors also captured the rotation angle amplitudes and numbers of cycles. Laboratory tests were conducted on a full-size replica of a vertical-and-chord connection to establish the relationship between rotation and normal stresses in the cross section from warping restraint at the connection locations. Analytical methods were shown to accurately predict the rotations and warping stresses along the member length. Applying the experimental and analytical results, the stress ranges were determined for the field-measured torsional responses, and the fatigue potential was evaluated. The results showed the measured stress ranges are near the constant amplitude fatigue limit, but the large cycle counts and frequency of events in the historical wind record that could produce torsional response indicate the need for continued monitoring and a long-term mitigation strategy. [ABSTRACT FROM AUTHOR]

The collapse of the Interstate 35W bridge in Minneapolis, Minnesota, in 2007 brought into question the strength of large-size gusset plates in steel truss bridges. To provide new data on the behavior and strength of large-size bridge-type gusset plates, experimental tests were performed and are described in this paper. The research program focused on sway-buckling behavior and test variables included plate thickness, compression diagonal flexural stiffness, initial out-of-plane imperfection, and member load combinations. Unique to this test program was the direct consideration of different compression diagonal out-of-plane flexural stiffnesses on plate buckling behavior and capacity. Results showed that sway-buckling behavior and ultimate capacity were affected by initial out-of-plane imperfections of the plate and the out-of-plane bending stiffness of the truss compression diagonal. Results also showed that the effective length factor, , a parameter used in present load rating guides, did not accurately predict sway-buckling capacity, and the Whitmore section approach may not be the best approximation for use in plate sway-buckling behavior. A stepped-column approach was shown to illustrate and predict the effect of the plate-member stiffness interaction on buckling capacity. [ABSTRACT FROM AUTHOR]

After the collapse of the Interstate 35W Bridge in Minneapolis, Minnesota, in 2007, transportation agencies began evaluating and rating their inventories of gusset plate connections. Connection evaluations require accurate drawings that detail the plate, member, and fastener geometries. These structural details should also accurately reflect the as-built conditions. For some connections, as-built information may not be available, or the available drawings may not represent the actual field conditions. To fill this gap, a new methodology was developed that enables rapid and accurate collection of field measurements for connection plate geometry. The method uses close-range photogrammetry techniques to rectify images taken with consumer-grade cameras using flat-field and fish-eye lenses. The technique has been demonstrated on full-scale gusset plates in the laboratory and in the field. Dimensional measurements from the processed images provided results that are as good as or better than conventional field measurements and with tolerances below what most engineers require for calculation of gusset plate connection capacity. This technique provides a new tool for bridge engineers to quickly collect gusset plate geometry that can be used in connection evaluations and rating and can further enhance bridge-management tasks. [ABSTRACT FROM AUTHOR]

Many bridges along the Gulf Coast of the United States were damaged by hurricanes, especially in the 2004 and 2005 hurricane seasons. Many more bridges are susceptible to similar damage. This research examines the structural performance of three commonly used connection details for AASHTO Type III prestressed concrete girders: headed studs, through bolts, and clip bolts. Full-scale specimens were fabricated and tested under static and dynamic cyclic load histories using expected maximum loads from previously conducted hydraulic tests of a scale model of a highway bridge spanning a coastal embayment. The load effects considered included (1) vertical uplift force, (2) lateral force, (3) combined lateral and vertical forces, and (4) dynamically applied wave force time histories. Connection performance was evaluated by comparing initial concrete cracking, strand slip, and ultimate capacity. The experimental results showed that the insert clip-bolt connections had the lowest capacity and produced significant ancillary damage to the surrounding concrete while the headed-stud connections exhibited the highest load capacity and negligible ancillary concrete damage. None of the anchorages considered would be capable of resisting newly specified vertical wave forces for large hurricane wave heights when significant air is entrapped such as those observed in Hurricane Katrina. [ABSTRACT FROM AUTHOR]

Current AASHTO-LRFD specifications use many disparate design provisions to establish live load demands in bridge decks. As an example, approximately 17% of Chapter 4 addresses the analysis of decks. One of the AASHTO-LRFD analysis methods for decks uses an orthotropic plate model. The present AASHTO-LRFD orthotropic plate model has a single formulation for the plate torsional stiffness, and this is not generally applicable to all deck types. In this paper, new analytical expressions are developed for moment in bridge decks subjected to arbitrary patch loading considering each of the three cases of orthotropy: (1) relatively torsionally stiff, flexurally soft decks; (2) relatively uniformly thick decks (such as a reinforced concrete deck); and (3) relatively torsionally soft, flexurally stiff decks. Using these newly developed expressions, the AASHTO-LRFD notional live load models were combined with impact, multiple presence, and live load factors to determine maximum strong direction live load moments for the Strength I design limit state. Design equations were developed to estimate the maximum strong direction live load moments without performing cumbersome moving load analysis for common deck orientations. Using the proposed formulations, bridge deck strength design demands can now be treated in a unified way across different deck types using only four equations. Application of these methods can significantly reduce and simplify the analysis of decks and allow bridge engineers to make comparisons across different deck design alternatives. [ABSTRACT FROM AUTHOR]

Orthotropic plates are widely used in bridge deck systems. However, these are not commonly treated as such within design specifications, and semianalytical solutions are not presently available for all deck types. This paper develops deflection equations for infinitely wide and simply supported thin plates considering each of the three cases of orthotropy: (1) relatively torsionally stiff, flexurally soft; (2) uniformly thick plate; and (3) torsionally soft, flexurally stiff; subjected to arbitrary patch loading. These are common boundary and loading conditions encountered for bridge deck applications. The reported analytical solutions enable rapid evaluation of multiple moving patch loads to determine maximum design load effects and permit validation of numerical and finite-element methods. Application of the solutions will produce guidelines that can prescribe design demands and establish practical design simplifications for treatment of different bridge deck and slab systems in a uniform and consistent manner. [ABSTRACT FROM AUTHOR]

To gain a better understanding of the wave forces that led to the failure of numerous causeway-type coastal highway bridges along the U.S. Gulf coast, a series of experiments was conducted on a realistic, 1:5 scale reinforced concrete bridge superstructure. The experimental setup is unique compared to other wave-in-deck studies in that the stiffness of the horizontal support system can be varied to represent different dynamic properties of the bridge system. The bridge specimen is subjected to a wide range of regular and random wave conditions at multiple water levels. In addition to measuring pressures and forces, the experiments measure the dynamic response of the bridge specimen using strain gauges, displacement sensors, and accelerometers. This paper presents the innovative experimental setup, and a preliminary analysis of the data showing the effect of wave height, wave period, and water level, on the forces experienced by the bridge superstructure. [ABSTRACT FROM AUTHOR]

Evaluation and rating of steel truss bridge connections has become imperative for many transportation agencies after the recent collapse of the I-35W Bridge in Minneapolis. Detailed engineering capacity calculations of gusset plate connections are time consuming and thus expensive. Large numbers of connections are in the national inventory and must be evaluated. A screening process and a simplified rapid screening process are proposed for ranking gusset plate connections in steel truss bridges to help bridge engineers identify possible vulnerable connections and aid field inspections. The procedures consider member demands relative to the connection geometric proportions for four different parameters: fasteners, plate tension, plate compression, and overall horizontal shear. The methods are demonstrated for two bridges, including the collapsed I35W Bridge, and clearly identify connections U10 and L11 as vulnerable for three of the four parameter types (fasteners were not identified as vulnerable for these connections). The ranking approach is not proposed as a substitute for thorough, detailed, and expert assessment of the connections, but rather allows rating engineers to more quickly prioritize detailed evaluations in an ordered systematic way from the most likely vulnerable connections to the least likely vulnerable connections. This technique may be considered analogous to performing screening tests on a new patient to indicate the likely medical condition prior to conducting more sophisticated and costly investigations. [ABSTRACT FROM AUTHOR]

Many transportation agencies are now evaluating and rating their inventory of steel truss bridge gusset plate connections after the collapse of the I35W Bridge in Minneapolis. Modern design methodologies are being used to evaluate inventory gusset plate connections that were designed using allowable stress methods. One such implementation is evaluation of gusset plates using block shear, an approach that was developed well after many of the nation’s truss bridges were designed. Vintage designs commonly used the Whitmore section to proportion gusset plate connections. Differences between rating outcomes from block-shear analysis at strength conditions with designs that employed allowable stresses on the Whitmore section method were identified and expected outcomes for rating of gusset plate connections are proposed. Examples are shown to highlight the similarities and differences in these two approaches to assist rating engineers in implementation and expected variabilities on the outcomes based on connection geometric proportions and material properties. [ABSTRACT FROM AUTHOR]

Many reinforced concrete bridges are posted or restricted to traffic, and repair or replacement decisions for these bridges involves both economical and safety considerations. To avoid the high costs of unnecessary replacement or repair, safety evaluation should be done with the most accurate methods available. Due to variability in material properties, geometrical properties, and methods of analysis, load carrying capacity evaluation may lead to uncertain outcomes. This paper presents a statistical model for combined shear-moment resistance of conventionally reinforced concrete bridge girders with common vintage design details and properties. New statistical data on stirrup spacing variability were developed from field measurements on in-service deck-girder bridges and these were combined with available data in the literature to model resistance uncertainty. The model offers bias factor and coefficient of variation for combined moment and shear carrying capacity per modified compression field theory. AASHTO-LRFD and ACI-318 were utilized to calculate capacity of the selected sections and strength reduction factors in AASHTO-LRFD and ACI-318 were compared using the obtained statistical parameters. [ABSTRACT FROM AUTHOR]

The LRFR Manual, within commentary Article C6.4.4.2.3, contains provisions for development of site-specific live load factors. In Oregon, truck weigh-in-motion (WIM) data were used to develop live load factors for use on state-owned bridges. The factors were calibrated using the same statistical methods that were used in the original development of LRFR. This procedure maintains the nationally accepted structural reliability index for evaluation, even though the resulting state-specific live load factors were smaller than the national standard. This paper describes the jurisdictional and enforcement characteristics in the state, the modifications used to described the alongside truck population based on the unique truck permitting conditions in the state, the WIM data filtering, sorting, and quality control, as well as the calibration process, and the computed live load factors. Large WIM data sets from four sites were used in the calibration and included different truck volumes, seasonal and directional variations, and WIM data collection windows. Finally policy implementation for actual use of the factors and future provisions for maintenance of the factors are described. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymers (FRP) are becoming more widely used for repair and strengthening of conventionally reinforced concrete (RC) bridge members. Once repaired, the member may be exposed to millions of load cycles during its service life. The anticipated life of FRP repairs for shear strengthening of bridge members under repeated service loads is uncertain. Field and laboratory tests of FRP-repaired RC deck girders were performed to evaluate high-cycle fatigue behavior. An in-service 1950s vintage RC deck-girder bridge repaired with externally bonded carbon fiber laminates for shear strengthening was inspected and instrumented, and FRP strain data were collected under ambient traffic conditions. In addition, three full-size girder specimens repaired with bonded carbon fiber laminate for shear strengthening were tested in the laboratory under repeated loads and compared with two unfatigued specimens. Results indicated relatively small in situ FRP strains, laboratory fatigue loading produced localized debonding along the FRP termination locations at the stem-deck interface, and the fatigue loading did not significantly alter the ultimate shear capacity of the specimens. [ABSTRACT FROM AUTHOR]

Large numbers of conventionally reinforced concrete (CRC) bridges in the national bridge inventory built during the 1950s are lightly reinforced for shear. Inspections revealed many of these bridges exhibit diagonal cracks resulting in load postings, monitoring, emergency shoring, repairs, and unscheduled bridge replacements. A research program was conducted to investigate the behavior and capacity of CRC bridge girders with vintage details. Laboratory tests of large-size girders representative of 1950s design and construction practice were carried out. Various steel reinforcement configurations were tested. Loading conditions were varied to reproduce girder behavior at different positions in a bridge and various loading protocols were considered. Test results provide a comprehensive data set for comparison of analysis methods and repair strategies; and indicated that anchorage of flexural steel was key to developing higher ultimate capacity, initial crack damage may not necessarily contribute to the final failure mode, and crack width alone may not indicate the level of damage to the beam. [ABSTRACT FROM AUTHOR]

Large numbers of conventionally RC deck–girder bridges are in the national highway system. Diagonal cracks have been identified in many of these bridges, which are exposed to millions of load cycles during service life. The anticipated life of these bridges in the cracked condition under repeated service loads is uncertain. Laboratory experiments were performed on full-size girder specimens to evaluate possible deterioration in shear capacity under repeated loading. Specimen variables included: T and inverted-T configurations, stirrup spacing, and flexural reinforcing details. Test results indicated bond deterioration increased diagonal crack displacements, and analysis methods to predict the shear capacity of diagonally cracked reinforced concrete girders subjected to high-cycle fatigue damage are provided. The AASHTO-LRFD shear provisions conservatively predicted shear capacity for the fatigued specimens without stirrup fractures, and shear capacity predictions from computer analysis program Response 2000 were very well correlated with experimental results for fatigued test specimens when the input concrete tensile strength was reduced to nearly zero. [ABSTRACT FROM AUTHOR]

This paper presents findings of field tests and analysis of two conventionally reinforced concrete (CRC) deck girder bridges designed in the 1950s. The bridges are in-service and exhibit diagonal cracks. Stirrup strains in the bridge girders at high shear regions were used to estimate distribution factors for shear. Impact factors based on the field tests are reported. Comparison of field measured responses with AASHTO factors was performed. Three-dimensional elastic finite-element analysis was employed to model the tested bridges and determine distribution factors specifically for shear. Eight-node shell elements were used to model the decks, diaphragms, bent caps, and girders. Beam elements were used to model columns under the bent caps. The analytically predicted distribution factors were compared with the field test data. Finally, the bridge finite-element models were employed to compare load distribution factors for shear computed using procedures in the AASHTO LRFD and Standard Specifications. [ABSTRACT FROM AUTHOR]

Large numbers of conventionally reinforced concrete deck–girder (RCDG) bridges remain in-service in the national highway system. Diagonal cracks have been identified in many of these bridges, which are exposed to millions of load cycles during service life. The anticipated life of these bridges in the cracked condition under repeated service loads is uncertain. RCDG bridges with diagonal cracks were inspected and instrumented. Strain and crack displacement data were collected under ambient traffic conditions and controlled test trucks. Results indicated relatively small stirrup stresses and diagonal cracks exhibited opening and closing under truck loading. [ABSTRACT FROM AUTHOR]

Concrete filled grid bridge decks exhibit orthogonal elastic properties and significant two-way bending action enabling orthotropic plate theory to determine structural response for these elements. Current American Association of State Highway and Transportation Officials load and resistance factor design (LRFD) specifications employ an orthotropic plate model to predict live load moment in concrete filled grid bridge decks but provide no guidance for computing displacement, a potentially important serviceability consideration. This paper presents equations to approximate the maximum deflection in concrete filled grid bridge decks based on orthotropic plate theory, multiple patch loads, LRFD design truck and tandem load cases, the influence of multiple spans, and the two most common deck orientations. [ABSTRACT FROM AUTHOR]

Due to the orthogonal elastic properties and significant two-way bending action, orthotropic plate theory may best be used to describe the behavior of concrete filled grid bridge decks. The current AASHTO LRFD specification employs an orthotropic plate model with a single patch load to predict live load moment in concrete filled grid bridge decks, which may not be conservative. This paper presents alternative equations to predict maximum moments, based on classical orthotropic plate theory, which include multiple patch loads, both the LRFD design truck and tandem load cases, and the two most common deck orientations. The predicted moments are verified through finite-element analyses. [ABSTRACT FROM AUTHOR]

An experimental study of composite bridge decks with alternative shear connectors has been performed. The alternative shear connector consists of concrete filled holes located in the webs of grid main bars and friction along the web embedded in the slab, which enables shear transfer between the concrete slab and steel grid. Results of static and fatigue tests on full-scale prototype decks indicated that composite action between the concrete slab and steel grid is maintained well above the service load range even after fatigue loading, the eventual loss of composite action at overload is gradual, failure was controlled by punching shear of the concrete slab and was unaffected by the shear connectors, and no significant change in behavior was observed due to fatigue loading. Further, the measured stress range at the shear connection location would not control the fatigue behavior of the deck in positive bending, and no fatigue cracking of the steel grid was observed in negative bending. [ABSTRACT FROM AUTHOR]

Although electrochemical treatment has received increased attention with respect to treating poly- and perfluoroalkyl substances (PFAS), studies assessing treatment longevity for the wide range of PFAS present in water impacted by aqueous film-forming foam (AFFF) are lacking. A 21-day study was performed in which electrochemical treatment using boron-doped diamond (BDD) anodes was performed in successive 24-h batch cycles on groundwater impacted with AFFF. Results showed substantial defluorination of both the perfluoroalkyl acids (PFAAs) and defluorination of polyfluoroalkyl compounds (based on fluoride generation). Substantial perchlorate generation was observed throughout the study. PFAS treatment effectiveness diminished over time due to scaling, resulting in decreased removal of the PFAAs and generation of perfluorobutanoic acid (PFBA). Based on measured generation of fluoride relative to the concentrations of the PFAAs, defluorination of the polyfluoroalkyl acids decreased 2–3 times more than the PFAAs due to this scaling. This suggests that defluorination of the polyfluoroalkyl acids occurred via a mechanism different from that of the PFAAs. Acid cleaning to remove the accumulated scale resulted in restoration of PFAS treatment. Together, these results suggest that electrochemical treatment of AFFF-impacted waters shows promise. Polyfluorinated compounds and PFBA showed greater adverse impacts from the mass transfer and/or residence time decreases associated with the scaling than what was observed for the other PFAAs. This implies that these compounds may prove to be the greater challenge in long-term full-scale applications. [ABSTRACT FROM AUTHOR]