Load Performance of In Situ Corrugated Steel Highway Culverts

This paper presents the results of field performance tests of 39 in-service corrugated steel highway culverts in Ohio. The culverts had span lengths varying from 3.23?m (10.6?ft)?to?7.04?m (23.1?ft) and backfill soil heights over the crown varying from 0.27?m (0.9?ft)?to?7.47?m (24.5?ft). Static and dynamic load tests were conducted by driving heavy trucks across the culverts. Static loads were applied at ten different locations above each culvert. Dynamic load tests were conducted at six truck speeds varying from 8?km/h (5?mi/h)?to?64?km/h (40?mi/h). A portable instrumentation frame was installed inside each test culvert to monitor deflections. Strains on the culvert walls were also measured at 14 locations using strain gauges. Effects of backfill height and loading conditions are investigated. According to the experimental results, a plot of maximum culvert deflection versus backfill height shows a nonlinear relationship. Maximum static load deflections were found to be consistently larger than the maximum dynamic deflections obtained using the same test truck. Deflections were nearly zero for deep culverts with backfill heights exceeding 4?m (13?ft). Maximum deflections correlate more closely to equivalent line loads than to total truck weight. The data also indicate that culvert behavior is more difficult to predict when backfill heights are shallow because other factors, such as culvert age and condition and soil type, likely play a significant role.     

Cyclic Lateral Load Behavior of a Pile Cap and Backfill

A series of static cyclic lateral load tests were performed on a full-scale 4×3 pile group driven into a cohesive soil profile. Twelve 324-mm steel pipe piles were attached to a concrete pile cap 5.18×3.05?m in plan and 1.12?m in height. Pile–soil–pile interaction and passive earth pressure provided lateral resistance. Seven lateral load tests were conducted in total; four tests with backfill compacted in front of the pile cap; two tests without backfill; and one test with a narrow trench between the pile cap and backfill soil. The formation of gaps around the piles at larger deflections reduced the pile–soil–pile interaction resulting in a degraded linear load versus deflection response that was very similar for the two tests without backfill and the trenched test. A typical nonlinear backbone curve was observed for the backfill tests. However, for deflections greater than 5 mm, the load-deflection behavior significantly changed from a concave down shape for the first cycle to a concave up shape for the second and subsequent cycles. The concave up shape continued to degrade with additional cycles past the second and typically became relatively constant after five to seven cycles. A gap formed between the backfill soil and the pile cap, which contributed to the load-deflection degradation. Crack patterns and sliding surfaces were consistent with that predicted by the log spiral theory. The results from this study indicate that passive resistance contributes considerably to the lateral resistance. However, with cyclic loading the passive force degrades significantly for deflections greater than 0.5% of the pile cap height.     

Experimental Investigation of Shear Capacity of Precast Reinforced Concrete Box Culverts

This study presents an experimental program to investigate the shear capacity of precast reinforced concrete box culverts. Each culvert was subjected to monotonically increasing load through a 254?mm×508?mm (10?in.×20?in.) load plate in order to simulate the HS20 truckload per AASHTO 2005. Instrumentation included strain gauges, high-resolution laser deflection sensor, and automated data acquisition. Four tests were conducted on 1.22?m×1.22?m×1.22?m (4?ft×4?ft×4?ft) box culverts. The location of the load plate was varied to identify the position, which introduces the maximum shear stresses. Laser sensor data and dial gauge readings were recorded to measure the deflection profile of the box culvert. Strain gauges were placed on the steel reinforcement to measure axial strain at locations of maximum positive and negative bending moments. The test results include reporting the loads at which each crack initiated and propagated. The displacement profile of the top slab from the laser instrumentation output along with the load versus maximum deflection for each culvert is also reported.     

Vertical Loads on Concrete Box Culverts under High Embankments

Vertical loads on concrete box culverts under high embankments are examined, where a high embankment is defined herein as one where the height of the fill above the culvert is greater than the width of the culvert. Results from an instrumented culvert are described, with results from pressure cells, strain gages in the wall, and strain gages in the roof showing reasonable agreement. There was strong correlation between the height of fill and the pressure and internal forces in the culvert, suggesting that the soil–structure interaction factor is independent of the H/B ratio. The results of the instrumented culvert were compared to those of other instrumented culverts under high embankments. The measured roof pressures were significantly greater than the pressure due to the soil overburden, with the measured pressures averaging 1.5 times the soil overburden pressure. Although the soil–structure interaction factor recommended by the American Society of Highway and Transportation Officials specification tends to under-predict the loads acting on concrete culverts, a simplified reliability analysis suggests that the Specification provides a sufficient level of safety.     

Behavior of Step Tapered Bored Piles in Sand under Static Lateral Loading

The behavior of step tapered bored piles in sand, under static lateral loading, was examined by field tests at one site in Kuwait. A total of 14 bored piles including two instrumented piles were installed for lateral loading. The soil profile consists of medium dense sand with weak cementations and no groundwater was encountered in the boreholes. Laboratory tests were carried out to determine the basic soil characteristics and the strength parameters. Both the ultimate lateral capacity and the deflections at applied loads were examined. The results indicate increased lateral load carrying capacity and decreased deflections at different applied loads for the step tapered piles due to the enlargement or strengthening of the upper section of the piles. The advantages of using this type of pile is emphasized including the cost saving resulting from an economical design.     

Experimental Study and Numerical Simulation on Concrete Box Culverts in Trenches

Concrete culverts in trenches have been widely used in expressways. Problems frequently take place because of improperly estimated vertical earth pressures on culverts. Different codes have been used in China to estimate the design load on culverts. In this study, a full-scale experiment and FEM simulation were conducted to evaluate the variation of vertical earth pressures and soil arching in backfill and to examine the accuracy of the methods recommended by different design codes including the prevailing Chinese General Code for Design of Highway Bridges and Culverts based on the linear earth pressure theory. The measured vertical earth pressures from the experiment were compared with those from the current theoretical methods. The variations of foundation pressure and settlement were also analyzed. The FEM simulation investigated the key influencing factors on the vertical earth pressures including the height of the embankment fill, the width of the trench, the slope angle of the trench, the dimensions of the culvert, the properties of the backfill, and the elastic modulus of the foundation soil. This research reveals that soil arch formed when the backfill on the culvert reached a certain height, but it was unstable. The coefficient of the vertical earth pressure on the top of the culvert was significantly different from that recommended by the Chinese General Code for Design of Highway Bridges and Culverts.     

Increased Lateral Abutment Resistance from Gravel Backfills of Limited Width

Lateral pile cap tests were performed on a pile cap with three backfills to evaluate the static and dynamic behavior. One backfill consisted of loose silty sand while the other two consisted of 0.91- and 1.82-m-wide dense gravel zones between the pile cap and the loose silty sand. The 0.91- and 1.82-m-wide dense gravel zones increased the lateral resistance by 75 to 150% and 150 to 225%, respectively, relative to the loose silty sand backfill. Despite being thin relative to the overall shear length, the 0.92- and 1.82-m-wide gravel zones increase lateral resistance to approximately 54 and 78%, respectively, of the resistance that would be provided by a backfill entirely composed of dense gravel. The dynamic stiffness for the pile cap with the gravel zones decreased about 10% after 15 cycles of loading, while the damping ratio remained relatively constant with cycling. Dynamic stiffness increased by about 10 to 40% at higher deflections, while the damping ratio decreased from an initial value of about 0.30 to around 0.26 at higher deflections.     

Using Inclinometers to Measure Bridge Deflection

Deflection of a bridge span under designed loads is an important parameter for bridge safety evaluation. However, it is inconvenient to obtain the bridge deflections directly. For bridges over rivers, railways, or highways, a direct measurement method is impractical. A promising bridge deflection measurement method (inclinometer method) is presented in this paper. It offers a simple, practical and inexpensive method of measuring static and dynamic deflections of bridge spans under loads, even for bridge spans that traverse great heights. Hundreds of experiments and practical tests on simple and continuous bridges, utilizing dynamic and static loads, under various vehicle speeds, show that the method has very high precision, which provides an authentic basis for new-built bridge acceptance and old bridge safety evaluation. The method does not need fixed observation positions as other deflection measurement methods because the inclinometers are installed on the bridge directly, which increases measurement efficiency greatly. These features indicate that as a potential method of measuring bridge deflection, inclinometers have significant engineering application value and a promising future.     

Effect of Wheel Live Load on Shear Behavior of Precast Reinforced Concrete Box Culverts

This study reports on a part of a comprehensive study to evaluate the shear capacity of the precast reinforced concrete box culverts. Six full-scale 2.4?m (8?ft) span box culverts were tested to failure by subjecting each culvert to the AASHTO HS-20 wheel load. The location of the wheel load was varied from the tip of the haunch as a function of the top slab effective depth in order to identify the critical shear location. Each test specimen was loaded incrementally up to failure in which crack initiation and propagation were identified and recorded in each load step. In some specimens the top slab compression distribution steel was precluded during specimen fabrication the effect of which was shown to be insignificant in culvert’s performance experimentally. Even though the test specimens were loaded to introduce shear behavior, it was shown that all the test specimens behaved in flexural mode up to and beyond standard factored live load. The test specimens only experienced shear cracks at loads equivalent to approximately twice of the aforementioned factored load. This study concludes that shear is not the governing behavioral mode for the concrete box culverts, and the live load distribution width equations along with the provisions for shear transfer devices for box culverts reported in the current standard need to be revisited.     

Passive Earth Pressure Mobilization during Cyclic Loading

The passive resistance measured in a series of full-scale tests on a pile cap is compared with existing theories. Four different soils were selected as backfill in front of the pile cap and the load-deflection relationships under cyclic loading were investigated. The log spiral theory provided the best agreement with the measured passive resistance. The Rankine theory significantly underestimated the passive force, while the Coulomb theory generally overestimated the resistance. The displacement necessary to mobilize the maximum passive force was compared with previous model and full-scale tests and ranged from 3.0 to 5.2% of the cap height. A hyperbolic model provided the best agreement with the measured backbone passive resistance curve compared with recommendations given by Caltrans and the U.S. Navy. However, this model overestimated the passive resistance for cyclic loading conditions due to the formation of a gap between the pile cap and backfill soil and backfill stiffness reduction. Based on the test results, the cyclic-hyperbolic model is developed to define load-deflection relationships for both virgin and cyclic loading conditions with the presence of a gap.     

Soil-Steel Interaction of Long-Span Box Culverts—Performance during Backfilling

The paper presents the performance of four long-span deep-corrugated steel box culverts with spans of 8- and 14-m during backfilling, as well as comparisons with finite-element modeling and design codes. Two of the culverts were stiffened at the crown arch. The test results show that the stiffening applied on the culverts is quite effective. The crown rises of the respective stiffened culverts were found to be half those of the not-stiffened culverts. The influence of the structure geometry on the soil-passive earth pressure was confirmed, as well as the sensitivity of box culverts to soil loads with increasing spans. The results showed that the influence of the size and shape of the box culverts on the amount of thrusts must be better implemented in the design method. The finite-element analysis results were conservative when live loading was concerned but the crown displacements and thrust during backfilling were underestimated.     

Field Static Load Test on Kao-Ping-Hsi Cable-Stayed Bridge

Field load testing is an effective method for understanding the behavior and fundamental characteristics of a cable-stayed bridge. This paper presents the results of field static load tests on the Kao-Ping-Hsi cable-stayed bridge, the longest cable-stayed bridge in Taiwan, before it was open to traffic. A total of 40 loading cases, including the unit and distributed bending and torsion loading effects, were conducted to investigate the bridge behavior. The atmospheric temperature effect on the variations of the main girder deflections was also monitored. The results of static load testing include the main girder deflections, the flexural strains of the prestressed concrete girder, and the variations of the cable forces. A three-dimensional finite-element model was developed. The results show that the bridge under the planned load test conditions has linear superposition characteristics and the analytical model shows a very good agreement with the bridge responses. Further discussion of deflection and cable forces of the design specifications for a cable-stayed bridge is also presented.     

Simulating Seismic Response of Cantilever Retaining Walls

Many failures of retaining walls during earthquakes occurred near waterfront. A reasonably accurate evaluation of earthquake effects under such circumstance requires proven analytical models for dynamic earth pressure, hydrodynamic pressure, and excess pore pressure. However, such analytical procedures, especially for excess pore pressure, are not available and hence comprehensive numerical procedures are needed. This paper presents the results of a finite-element simulation of a flexible, cantilever retaining wall with dry and saturated backfill under earthquake loading, and the results are compared with that of a centrifuge test. It is found that bending moments in the wall increased significantly during earthquakes both when backfill is dry or saturated. After base shaking, the residual moment on the wall was also significantly higher than the moment under static loading. Liquefaction of backfill soil contributed to the failure of the wall, which had large outward movement and uneven subsidence in the backfill. The numerical simulation was able to model quite well the main characteristics of acceleration, bending moment, displacement, and excess pore pressure recorded in the centrifuge test in most cases with the simulation for dry backfill slightly better than that for saturated backfill.     

Seismic Behavior of Cantilever Retaining Walls with Liquefiable Backfills

A series of centrifuge tests were conducted to investigate the seismic behavior of fixed-base, cantilever, retaining walls supporting saturated, liquefiable, cohesionless backfills. Accelerations, bending strains, deflections, and lateral earth pressures were measured on the walls. Accelerations, pore pressures, and surface settlements were measured in the soil. Parametric studies investigating effects of wall stiffness and magnitude of shaking on the wall-soil behavior were conducted. The magnitude and distribution of lateral earth pressures were determined. Experimental results demonstrated that excess pore pressures in liquefiable backfills contribute significantly to seismic, lateral, earth pressures. It was shown that the average rise in the dynamic thrust is well correlated to the excess pore pressures in the backfill but is insensitive to the range of wall stiffness. It was found that simple calculations, based on Coulomb's active earth pressure theory, can be used to estimate the dynamic thrust at the end of shaking, when backfill liquefies completely. The location of the line of action of the total static lateral thrust was approximately two-thirds of the wall height from the top. During shaking, this distance varied between 0.6 and 0.8 of the wall height.     

Inspection and Risk Assessment of Concrete Culverts under Ohio’s Highways

In 2003 the Ohio Department of Transportation (ODOT) implemented a new culvert management program. Simultaneously, a team of researchers from the Ohio Research Institute for Transportation and the Environment (ORITE) and engineers from a private consulting firm conducted a joint study to evaluate the effectiveness of field culvert inspection and rating procedures proposed by the ODOT’s new program and describe the best remedial measures currently available for highway culverts. This paper focuses on the first component and addresses it relative to concrete culverts. The new inspection procedure for concrete culverts was applied at 25 sites. Inspection data were examined to detect common problems existing at concrete culvert sites in Ohio. The field data were also analyzed using statistical software to identify factors that contribute to the degradation of concrete culverts. Despite the limited amount of data, the results indicated that the ODOT approach was basically sound. The final segment of the paper presents a risk assessment method developed by the ORITE researchers. The proposed risk assessment method computes the overall structural health rating for any inspected culvert and recommends a course of action.     

Fundamental Frequency Testing of Reinforced Concrete Beams

Tests were conducted to measure the fundamental frequencies of reinforced concrete beams. Beams were tested prior to load application and after they had been loaded to various fractions of their ultimate moment capacity. Dynamic testing was performed in an unloaded state in both the direction of loading and in the direction perpendicular to loading. Resulting fundamental frequencies were used to determine the dynamic flexural stiffness (EdI) relative to the undamaged flexural stiffness. Results show that fundamental frequency tests can effectively measure decreases in dynamic flexural stiffness caused by flexural cracking. However, the effective moment of inertia in the relaxed state is not accurately predicted by American Concrete Institute recommendations for computing static beam deflections. Equations were developed to describe the effective flexural stiffness of unloaded, cracked beams. A relative dynamic flexural stiffness value of 70 provides a conservative prediction that a beam has failed by being loaded to its ultimate moment capacity.     

Laboratory Measurements of Flow through Culverts

Laboratory apparatus to simulate flow through culverts has been used to collect discharge and water level measurements. Two different shapes of culvert barrels, namely square and circular, were tested. The measurements presented in this note are intended to provide useful information regarding the variety of flow regimes (including overtopping) through culverts, and the transitions from one flow regime to another. It is known that modeling the culvert flow regimes and capturing the transitions among these regimes numerically is a challenging task. To that effect, the laboratory measurements presented herein can provide a testing and validation data set for numerical modeling of hydraulic structures such as culverts.     

Entrance Loss Coefficients and Inlet Control Head–Discharge Relationships for Buried-Invert Culverts

In current practice, entrance loss coefficients and inlet control head–discharge relationships for buried-invert culverts designed for fish passage applications are either ignored or approximated using traditional culvert design data due to a lack of data specific to these alternative culvert geometries. This study experimentally determined entrance loss coefficients and inlet control head–discharge relationships for circular culverts with invert burial depths of 20, 40, and 50% and an elliptical culvert with 50% invert burial depth. In general, the inlet loss coefficients for buried-invert culverts were higher than for traditional culverts of the same cross-sectional shape without invert burial. The influence of approach flow conditions (ponded or channelized) on inlet loss coefficients and inlet control head–discharge relationships was also investigated. This paper outlines the experimental methods used to determine entrance loss coefficients and inlet control head–discharge regression constants relative to these alternative culvert geometries and presents the data relevant to the hydraulic design and evaluation of these culverts.     

Laboratory Testing to Examine Deformations and Moments in Fiber-Reinforced Cement Pipe

Two 381 mm (15 in. nominal) diameter fiber reinforced cement pipes have been tested under embankment loading conditions to study pipe response in both low stiffness, fine grained backfill, and a high stiffness graded granular backfill. Pipe deformations and strains were measured and interpreted to provide insight into the effect of soil backfill on the deformations and moments that develop. Not surprisingly, the use of silty clay backfill resulted in greater pipe deflections while the stiffer granular backfill lead to greater load transfer to the surrounding ground. Calculations using elastic soil-pipe interaction theory were effective in estimating the observed changes in pipe diameter at typical service loads (overburden pressures of 100 kPa, i.e., 14.4 psi in the lower stiffness backfill and 200 kPa, i.e., 28.8 psi in the high stiffness backfill). Measured strain distributions show that the fiber reinforced pipe exhibited ovaling response similar to that seen for flexible and semiflexible pipes. As expected, tensile strains were observed on the outer surface at the springlines and the inner surface at the crown. Strains observed at the haunch were negligible, indicating that the bending moments within the pipe have conventional “hourglass” distribution, with negligible moments at shoulders and haunches. Differences in strain measured at the inner and outer surfaces were used with the elastic pipe modulus to calculate the experimental bending moments. Comparisons of those experimental bending moments with the bending moment calculated for a rigid pipe indicate that these FRC pipe structures are semirigid so that moments are reduced as a result of support provided by the surrounding soil. A design expression for moment arching factor (MAF or moment divided by the rigid pipe moments) developed in an earlier paper was found to provide reasonable estimates for the experimental moment values. Moment estimated using the design soil moduli of McGrath and MAF provide moment values that are reasonable and conservative relative to those that were observed.     

Full-Scale Impact Test of Four Traffic Barriers on Top of an Instrumented MSE Wall

This paper presents the results of four full-scale impact tests against barriers placed on top of an instrumented mechanically stabilized earth (MSE) wall. The impact was created by a head-on collision of a 2,268-kg bogie going at about 32.2 km/h. The barriers were New Jersey and vertical wall barriers with a 1.37-m-wide moment slab in 9.14-m-long sections. The wall was 1.52 m high with one panel and two layers of reinforcement. The reinforcement was 2.44-m-long strips, 4.88-m-long strips, and 2.44-m-long bar mats. The backfill was crushed rock. The instrumentation consisted of accelerometers, strain gauges, contact switch, displacement targets, string lines, and high-speed cameras. The test was designed to represent a commonly used installation in current practice including an impact load on the barrier at least equal to 240 kN. Most of the barriers sustained significant damage but overall the behavior of the wall was satisfactory since the displacements of the panels were minimal (less than 25 mm) and the panel damage was acceptable except possibly in the case of the 4.88-m-long strips. The loads measured in the reinforcement indicate that the reinforcement was brought to its ultimate capacity for the duration of the impact but since the impact duration was so short and since the displacements of the panels were within tolerable limits of 25 mm, this is considered acceptable. The use of the longer strips (4.88-m-long strips) leads to slightly smaller panel displacements and higher panel stresses as evidenced by a bending crack in the panel. The 2.44-m-long strips permitted more displacement of the wall panels, but the magnitude of the displacement was considered to be tolerable. The measured maximum dynamic loads in the strips were found to be 3–5 times higher than the calculated maximum static loads by AASHTO guidelines.