Geosynthetic Reinforced Soil Integrated Bridge System Research Articles

Deformation Responses of a Geosynthetic Reinforced Soil-Integrated Bridge System Under Static Loading and Sensitivity Analysis of Influential Factors Based on the Improved Grey Relational Method

A numerical parametric study is conducted to evaluate the effects of various parameters on the deformation responses of a geosynthetic reinforced soil-integrated bridge system (GRS-IBS) under static load. The investigated parameters include the abutment height, reinforcement spacing, reinforcement length, reinforcement stiffness, bridge load, and backfill internal friction angle. The improved grey relational method is used to investigate the sensitivity of influential factors on the deformation responses of the GRS-IBS. The simulation results indicate that the abutment height, reinforcement spacing, and bridge load have a significant impact on the performance of the GRS-IBS with respect to lateral displacement and settlement, while the effects of reinforcement length, reinforcement stiffness, and backfill internal friction angle on the deformation behavior of the abutment are negligible. Differential settlements between the girder and approach are minimal under all conditions. The potential failure envelope of the GRS-IBS exhibits a “L” shaped configuration where the potential failure surface starts beneath the inner edge of the strip footing, extending vertically downward to half of the wall height and further bifurcating toward the strip footing and the toe of the wall. The results of the improved grey relational analysis show that reinforcement spacing is the most sensitive to the lateral displacement of the GRS-IBS. The abutment height and bridge load are more sensitive to abutment deformation than other influential factors. These three parameters are crucial to the deformation behavior and should be given primary consideration when designing a GRS-IBS.

Use of geosynthetic reinforced soil-integrated bridge system to alleviate settlement problems at bridge approach: A review

Bump problems at the bridge approach cause riding discomfort and result in safety issue to the road users. The Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) is a recent bridge approach construction system that connects the bridge deck and roadways without joints and bearings, thus capable to eliminate the bump problems. This system is gaining popularity for low to medium bridge construction due to its relatively faster, lower cost, and simple construction process. The GRS abutment is a composite geotechnical structure with internally supported reinforcement. A close spacing reinforcement of 0.2–0.3 m in between the compacted granular backfill of high shear resistance has improved the bearing capacity of the GRS abutment, hence capable to support the bridge loads directly. In this paper, a thematic literature review on the bump problems and GRS-IBS system is presented. Summaries of previous studies are tabulated and discussed, inclusive of case studies, physical models, numerical models, and key factors affecting the performance of GRS-IBS. Limitations posed to this system are also provided at the end of this article. The review and summary of this paper are expected to provide meaningful information to the readers.

Field monitoring of vertical stress distribution in GRS-IBS with full-height rigid facings

This paper presents a case study of the first geosynthetic reinforced soil-integrated bridge system (GRS-IBS) with full-height rigid facings in China. Open graded gravel and biaxial geogrid were used for the GRS-IBS. Steel frames and three-dimensional (3D) vegetation nets were used as temporary facing support during construction of the GRS abutments. Full-height rigid facings were cast in place on strip foundations. Field monitoring results of vertical stress distribution for different construction stages and loading conditions are presented and discussed. For both bridge dead load and truck loads, measured incremental vertical stresses under the beam seat increase significantly with increasing elevation, especially for higher applied vertical stress. The calculated incremental vertical soil stresses using the Boussinesq solution are in reasonable agreement with the measured values, while the 2 : 1 stress distribution method overestimates the incremental stresses in the lower section of the abutment. The transferred vertical stresses from bridge load application for the GRS abutment with full-height rigid facing are larger than those for the GRS abutment with modular block facing near the top of the abutment, but are smaller near the bottom.

Numerical simulation of dynamic response of geosynthetic-reinforced soil-integrated bridge system

Numerical simulation of dynamic response of geosynthetic-reinforced soil-integrated bridge system

Numerical Analyses on the Behavior of Geosynthetic-Reinforced Soil: Integral Bridge and Integrated Bridge System

Geosynthetic-reinforced soil (GRS) technology has been used worldwide since the 1970s. An extension to its development is the application as a bridge abutment, which was initially developed by the Federal Highway Administration (FHWA) in the United States, called the GRS—integrated bridge system (GRS-IBS). Now, there are several variations of this technology, which includes the GRS Integral Bridge (GRS-IB) developed in Japan in the 2000s. In this study, the GRS-IB and GRS-IBS are examined. The former uses a GRS bridge abutment with a staged-construction full height rigid (FHR) facing integrated to a continuous girder on top of the FHR facings. The latter uses a block-faced GRS bridge abutment that supports the girders without bearings. In addition, a conventional integral bridge (IB) is considered for comparison. The numerical analyses of the three bridges using Plaxis 2D under static and dynamic loadings are presented. The results showed that the GRS-IB exhibited the least lateral displacement (almost zero) at wall facing and vertical displacements increments at the top of the abutment compared to those of the GRS-IBS and IB. The presence of the reinforcements (GRS-IB) reduced the vertical displacement increments by 4.7 and 1.3 times (max) compared to IB after the applied general traffic and railway loads, respectively. In addition, the numerical results revealed that the GRS-IB showed the least displacement curves in response to the dynamic load. Generally, the results revealed that the GRS-IB performed ahead of both the GRS-IBS and IB considering the internal and external behavior under static and dynamic loading.

Numerical parametric study of geosynthetic reinforced soil integrated bridge system (GRS-IBS)

A 2-D finite flement model was developed in this study to conduct a FE parametric study on the effects of some variables in the performance of geosynthetic reinforced soil integrated bridge system (GRS-IBS). The variables investigated in this study include the effect of internal friction angle of backfill material, width of reinforced soil foundation (RSF), secondary reinforcement within bearing bed, setback distance, bearing width and length of reinforcement. Other important parameters such as reinforcement stiffness and spacing were previously investgated by the authors. The performance of GRS-IBS were investgated in terms of lateral facing displacement, strain distribution along reinforcement, and location of potential failure zone. The results showed that the internal friction angle of backfill material has a significant impact on the performance of GRS-IBS. The secondary reinforcement, setback distance, and bearing width have low impact on the performance of GRS-IBS. However, it was found that the width of RSF and length of reinforcement have negligible effect on the performance of GRS-IBS. Finally, the potential failure envelope of the GRS-IBS abutment was found to be a combination of punching shear failure envelope (top) that starts under the inner edge of strip footing and extends vertically downward to intersect with Rankine active failure envelope (bottom).

Prediction equations for estimating maximum lateral displacement and settlement of geosynthetic reinforced soil abutments

Abstract The Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS), which consists of closely-spaced layers of geosynthetic reinforcement and compacted granular fill material, is a fast, sustainable and cost-effective method for bridge support. The in-service performance of this innovative bridge support system is largely evaluated through the vertical and horizontal deformations of the GRS abutments. This paper presents the development of nonlinear equations for estimating the maximum lateral displacement and settlement of GRS abutments. The parameters that are considered in the prediction equations include abutment geometry (height, facing batter and foundation width), backfill friction angle, reinforcement characteristics (stiffness, spacing, and length), and applied static loads from 50 to 400 kPa. In the development of the prediction equations, a parametric study was first conducted using a validated finite difference numerical model. The results of the parametric study were then used to conduct a regression analysis to develop the equations for estimating the maximum lateral displacement and settlement of GRS abutments under service loads. The equations were validated using three case studies. The developed prediction equations can contribute to a better understanding and enable simple calculations in designing these structures.

Comparison of Field Behavior with Results from Numerical Analysis of a Geosynthetic Reinforced Soil Integrated Bridge System Subjected to Thermal Effects

When subjected to ambient daily temperature fluctuations, a 109.5 ft-long geosynthetic reinforced soil integrated bridge system (GRS-IBS) was observed to undergo cyclic straining of the superstructure. The upper and lower reaches of the superstructure experienced the highest and lowest strain fluctuation, respectively. These non-uniform strains impose not only axial loading of the superstructure but also bending. Pure axial loading in a horizontal superstructure will cause the footings to slide. However, bending in the superstructure will cause the footings to rotate thereby inducing cyclic fluctuations of the vertical pressure beneath the footing and also lateral pressure behind the end walls. Measured vertical footing pressure closest to the stream experienced the greatest daily pressure fluctuation (≈ 2,500–3,000 psf), while that nearest the end wall experienced the least. The toe pressure fluctuations seem rather large. That these large vertical pressure fluctuations are observed in a tropical climate like Hawaii when no other GRS-IBS in temperate regions has reported the same (or perhaps higher fluctuation) is indeed surprising. The larger these pressures are, the greater the likelihood of inducing cyclic-induced deformations of the GRS abutment. A finite element analysis of the same GRS-IBS was performed by applying an equivalent temperature and gradient to the superstructure over the coldest and hottest periods of a day to see if the field measured values of pressures are reasonable and verifiable, which indeed they were. This methodology is novel in the sense that the effects of axial load and bending of the superstructure are simulated using measured strains rather than measured temperatures.

Seismic performance of a whole Geosynthetic Reinforced Soil – Integrated Bridge System (GRS-IBS) in shaking table test

A scaled plane-strain shaking table test was conducted in this study to investigate the seismic performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) with a full-length bridge beam resting on two GRS abutments at opposite ends subjected to earthquake motions in the longitudinal direction. This study examined the effects of different combinations of reinforcement stiffness J and spacing Sv on the seismic performance of the GRS-IBS. Test results show that reducing the reinforcement spacing was more beneficial to minimize the seismic effect on the GRS abutment as compared to increasing the reinforcement stiffness. The seismic inertial forces acted on the top of two side GRS abutments interacted with each other through the bridge beam, which led to close peak acceleration amplitudes at the locations near the bridge beam. Overall, the GRS-IBS did not experience obvious structure failure and significant displacements during and after shaking. Shaking in the longitudinal direction of the bridge beam increased the vertical stress in the reinforced soil zone. The maximum tensile forces in the upper and lower geogrid layers due to shaking happened under the center of the beam seat and at the abutment facing respectively.

Numerical parametric study to evaluate the performance of a Geosynthetic Reinforced Soil–Integrated Bridge System (GRS-IBS) under service loading

Abstract This paper presents the evaluation of the performance of the Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) in terms of lateral facing deformation, strain distribution along geosynthetics, and the location of potential failure zone (locus of maximum strain) subjected to service loading. Simulations were conducted using two-dimensional (2D) PLAXIS 2016 Finite Element (FE) program. The hardening soil model proposed by Schanz et al. (1999) was used to simulate the behavior of the backfill material; the interface between the backfill materials and the reinforcement was simulated using the Mohr-Coulomb frictional model, and the reinforcement and facing block were simulated using the linear elastic model. The numerical model was first verified using results of a field case study conducted at the GRS-IBS of Maree Michel Bridge, Louisiana. A parametric study was then carried out to investigate the effects of abutment height, span length, reinforcement spacing, and reinforcement stiffness on the performance of the GRS-IBS. The results of the FE analyses indicate that the abutment height and span length have significant impact on the maximum strain distribution along the geosynthetic, and the lateral facing displacement. It was noted that the reinforcement stiffness has a significant impact on the GRS-IBS behavior up to a certain point, beyond which the effect tends to decrease contradictory to the reinforcement spacing that has a consistent relationship between the GRS-IBS behavior and the reinforcement spacing. The results also indicate that the reinforcement spacing has greater influence on the lateral facing displacement than the reinforcement stiffness for the same reinforcement strength to spacing ratio (Tf/Sv), mainly due to the composite behavior resulting from closely reinforced soil.

Long-Term Behavior of a Geosynthetic Reinforced Soil Integrated Bridge System in Hawaii

A 109.5-Ft-long Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) in Hawaii was instrumented to measure superstructure strains, vertical pressures below the footing, lateral pressures behind the end wall and modular block facing, and lateral displacements of the facing. Field surveys were also performed to measure the bridge footing settlement. The field data showed that: (1) with time the superstructure compressive concrete strains gradually increased and the end wall lateral pressures gradually decreased, evidence of superstructure concrete creep and shrinkage; (2) three years after construction, the total footing settlement was ≈ 1.2 in.; and (3) the bridge superstructure undergoes daily and seasonal thermal expansion and contraction cycles. Also seasonally, the vertical pressures beneath the footing, lateral pressures behind the end walls, and superstructure strains fluctuate cyclically. The vertical footing pressure closest to the stream experienced the greatest daily pressure fluctuation (≈ 2500−3000 psf), while the one nearest the end wall experienced the least. Based on the results of cyclic triaxial tests on a basalt aggregate similar to the GRS backfill to estimate permanent deformation of the abutment due to daily pressure fluctuations, it was estimated that the permanent strain ≈ 1%, comparable to what was observed in the bridge footing. After three years, the total settlement is about 1.6% of the GRS abutment height; ≈ 0.7% of this is due to the structure dead weight and the remaining 0.9% is due to cyclic loading, consistent with the 1% cyclic strain from laboratory permanent deformation tests.

Evaluating the Performance of Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) under Working Stress Condition

This paper evaluates the performance of geosynthetic reinforced soil-Integrated Bridge System (GRS-IBS) in terms of lateral facing deformation and strain distribution along geosynthetics. Simulations were conducted using 2D PLAXIS program. The hardening model proposed by Schanz et al. [1] was used to simulate the behavior of backfill material; the backfill-reinforcement interface was simulated using Mohr-Coulomb model, and the reinforcement and facing block were simulated using linear elastic models. The numerical model was verified using the results of a case study conducted at Maree Michel GRS-IBS, Louisiana. Parametric study was carried out to investigate the effects of span length, reinforcement spacing, and reinforcement stiffness on the performance of GRS-IBS. The results indicate that span length have significant impact on strain distribution along geosynthetics and lateral facing deformation. The reinforcement stiffness has significant impact on the GRS-IBS behavior up to a certain point, beyond which the effect tends to decrease contradictory to reinforcement spacing that has a consistent relationship between the GRS-IBS behavior and reinforcement spacing. The results also indicate that reinforcement spacing has higher influence on the lateral facing deformation than the reinforcement stiffness for the same reinforcement strength/spacing ratio (Tf/Sv) due to the composite behavior of closely reinforcement spacing.

Numerical evaluation of the effect of differential settlement on the performance of GRS-IBS

This paper presents the numerical results of the performance of the Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) due to differential settlement underneath the reinforced soil foundation (RSF), underneath the reinforced zone including the RSF, and underneath the retained soil. The performance was evaluated in terms of reinforcement strain, lateral facing deformation, bump at the approach roadway – bridge slab intersection, and lateral facing pressure. Four different differential settlement values of 50, 100, 150, and 200 mm were selected for this study under three different service loading conditions corresponding to bridge spans of 24.4, 30.5, and 36.6 m. Simulations were conducted using the two-dimensional (2D) PLAXIS 2016 finite element (FE) program. The hardening soil model was used to simulate the backfill material behavior. The interface between the backfill material and the reinforcement was simulated using the Mohr-Coulomb model. The reinforcement and facing block were simulated using the linear elastic model. The results of FE analyses indicate that the differential settlement under the RSF has a high impact on both the strain distribution along the reinforcement and the lateral facing displacement.

Life cycle assessment of a geosynthetic-reinforced soil bridge system – A case study

Road infrastructures are a very important component of the world's total transportation network. Investment in its construction and maintenance is significant on a global scale. The paper presents some results from an environmental study of a geosynthetic-reinforced soil integrated bridge system. The Pavlovski potok stream in Slovenia was used as a demonstration case for this study. It is the first GRS bridge system with full-height rigid (FHR) facings in Europe. It was constructed at the end of 2014. The goal of these analyses was to compare two different types of bridges: the new GRS bridge system, which is comprised of a simple girder partially structurally integrated to FHR facings of GRS bridge abutments and a conventional reinforced concrete road bridge. The results of an environmental life cycle assessment (LCA) show that the GRS bridge system has a much lower environmental impact than an equivalent bridge conventionally built with reinforced concrete.

3D Finite element analysis of the geosynthetic reinforced soil-integrated bridge system (GRS-IBS) under different loading conditions

Abstract In this study, a three-dimensional (3D) Finite Element (FE) analysis was developed to simulate the fully-instrumented geosynthetic reinforced soil integrated bridge system (GRS-IBS) at Maree Michel Bridge in Louisiana. The 3DFE computer program PLAXIS 3D 2016 was selected to simulate the GRS-IBS behavior under different loading conditions. A second order-hyperbolic elasto-plastic soil model was used to simulate the granular backfill materials. The soil-structure interaction was simulated using zero thickness interface elements, in which the interface shear strength is governed by Mohr-Coulomb failure criterion. Three different loading conditions were considered in this study: (a) at the end of bridge construction (Case 1); (b) surface loading (Case 2); and (c) at abnormal loading (Case 3), which is equal to the dead load of the bridge structure plus three times the service loading. The predicted results were compared with the field measurements at the end of bridge construction. Moreover; the predicted results of the 3D-FE analysis were compared with those predicted using the 2D-FE analysis. A good agreement was obtained between the 3D-FE and 2D-FE numerical results and the field measurements. The predicted results using the 3D-FE showed that the range of maximum reinforcement strain under service loading ranges between 0.6% and 1.5%, depending on the location of the reinforcement layer. The maximum lateral deformation at the face was between 3 mm (0.07% lateral strain) under service load case and 7 mm (0.3% lateral strain) for abnormal load case. The maximum settlement of the GRS-IBS due to the service loading was 9 mm (0.3% vertical strain). The axial reinforcement forces predicted by FHWA (Adam et al., 2011) design methods were compared with those predicted by the 3D-FE and 2D-FE analysis. The results showed that the FHWA analytical method is 1.5–2.5 times higher than those predicted by the FE analysis, depending on the loading condition and reinforcement location.

Applied bearing pressure beneath a reinforced soil foundation used in a geosynthetic reinforced soil integrated bridge system

Geosynthetic reinforced soil integrated bridge system (GRS-IBS) design guidelines recommend the use of a reinforced soil foundation (RSF) to support the dead loads that are applied by the reinforced soil abutment and bridge superstructure, as well as any live loads that are applied by traffic on the bridge or abutment. The RSF is composed of high-quality granular fill material that is compacted and encapsulated within a geotextile fabric. Current GRS-IBS interim implementation design guidelines recommend the use of design methodologies for bearing capacity that are based around rigid foundation behavior, which yield a trapezoidal applied pressure distribution that is converted to a uniform applied pressure that acts over a reduced footing width for purposes of analysis. Recommended methods for determining the applied pressure distribution beneath the RSF for settlement analyses follow conventional methodologies for assessing the settlement of spread footings, which typically assume uniformly applied pressures beneath the base of the foundation that are distributed to the underlying soil layers in a fashion that can reasonably be modeled with an elastic-theory approach. Field data collected from an instrumented GRS-IBS that was constructed over a fine-grained soil foundation indicates that the RSF actually behaves in a fairly flexible way under load, yielding an applied pressure distribution that is not uniform or trapezoidal, and which is significantly different than what conventional GRS-IBS design methodologies assume. This paper consequently presents an empirical approach to determining the applied pressure distribution beneath the RSF in GRS-IBS construction. This empirical approach is a useful first step for researchers, as it draws important attention to this issue, and provides a framework for collecting meaningful field data on future projects which accurately capture real GRS-IBS foundation behavior.

Numerical evaluation of the performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) under different loading conditions

This paper presents the results of a finite element (FE) numerical analysis that was developed to simulate the fully-instrumented Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) at the Maree Michel Bridge in Louisiana. Four different loading conditions were considered in this paper to evaluate the performance of GRS-IBS abutment due to dead loading, tandem axle truck loading, service loading, and abnormal loading. The two-dimensional FE computer program PLAXIS 2D 2016 was selected to model the GRS-IBS abutment. The hardening soil model proposed by Schanz et al., (1999) that was initially introduced by Duncan and Chang (1970) was used to simulate the granular backfill materials; a linear-elastic model with Mohr-Coulomb frictional criterion was used to simulate the interface between the geosynthetic and backfill material. Both the geosynthetic and the facing block were modeled using linear elastic model. The Mohr-Coulomb constitutive model was used to simulate the foundation soil. The FE numerical results were compared with the field measurements of monitoring program, in which a good agreement was obtained between the FE numerical results and the field measurements. The range of maximum reinforcement strain was between 0.4% and 1.5%, depending on the location of the reinforcement layer and the loading condition. The maximum lateral deformation at the face was between 2 and 9 mm (0.08%–0.4% lateral strain), depending on the loading condition. The maximum settlement of the GRS-IBS under service loading was 10 mm (0.3% vertical strain), which is about two times the field measurements (∼5 mm). This is most probably due to the behavior of over consolidated soil caused by the old bridge. The axial reinforcement force predicted by FHWA (Adams et al., 2011b) design methods were 1.5–2.5 times higher than those predicted by the FE analysis and the field measurements, depending on the loading condition and reinforcement location. However, the interface shear strength between the reinforcement and the backfill materials predicted by Mohr-Coulomb method was very close to those predicted by the FE.

Numerical Investigation of the Geosynthetic Reinforced Soil–Integrated Bridge System under Static Loading

AbstractThis paper presents numerical simulations of the performance of the Geosynthetic Reinforced Soil–Integrated Bridge System (GRS-IBS) under static loading conditions. Simulations were conduct...

Performance monitoring of Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) in Louisiana

The Geosynthetic Reinforced Soil (GRS) Integrated Bridge System (IBS) is an alternative design method to the conventional bridge support technology. Closely spaced layers of geosynthetic reinforcement and compacted granular fill material can provide direct bearing support for structural bridge members if designed and constructed properly. This new technology has a number of advantages including reduced construction time and cost, generally fewer construction difficulties, and easier maintenance over the life cycle of the structure. These advantages have led to a significant increase in the rate of construction of GRS-IBS structures in recent years. This paper presents details on the instrumentation plan, short-term behavior monitoring, and experiences gained from the implementation of the first GRS-IBS project in Louisiana. The monitoring program consisted of measuring bridge deformations, settlements, strains along the reinforcement, vertical and horizontal stresses within the abutment, and pore water pressures. In this paper, the performance of instrumentation sensors was evaluated to improve future instrumentation programs. Measurements from the instrumentations also provide valuable information to evaluate the design procedure and the performance of GRS-IBS bridges. The instrumentation readings showed that the magnitude and distribution of strains along the reinforcements vary with depth. The locus of maximum strains in the abutment varied by the surcharge load and time that did not corresponds to the (45+ϕ/2) line, especially after the placement of steel girders. A comparison was made between the measured and theoretical value of thrust forces on the facing wall. The results indicated that the predicted loads by the bin pressure theory were close to the measured loads in the lower level of abutment. However, the bin pressure theory under predicted the thrust loads in the upper layers with reduced reinforcement spacing. In general, the overall performance of the GRS-IBS was within acceptable tolerance in terms of measured strains, stresses, settlements and deformations.

Full-Scale Testing of Geosynthetic-Reinforced, Soil-Integrated Bridge System

This paper focuses on the preliminary results of static load tests that were conducted on a geosynthetic-reinforced, soil-integrated bridge system (GRS-IBS) in Louisiana. Sixteen loading tests that used two fully loaded trucks were conducted on the instrumented GRS-IBS bridge. The bridge was surcharge loaded to stress levels well in excess of working load conditions. To evaluate the performance of the GRS-IBS abutment under different load tests, various types of instrumentation were installed; these included shape accelerated arrays, pressure cells, strain gauges, piezometers, and thermocouples. The primary measurements were the horizontal deformations near the front wall, vertical deformation of the GRS abutment, distribution of stresses in the GRS abutments and below the reinforced soil foundation, and distribution of strains along the geosynthetic reinforcements. Measurements from the instrumentation provided information needed to verify design factors and parameters for the GRS-IBS abutment. The bridge settlement and lateral movement of the facing wall were within the serviceability level; this result demonstrated excellent load-carrying capacity of the GRS abutment. The locus of maximum strains in the abutment varied by the surcharge load and did not correspond to the (45 + ϕ/2) line, especially when the surcharge load was placed at the bridge. The results of the load test revealed that the GRS-IBS bridge responses to the load tests were well within the serviceability limits, and the overall performance of the GRS-IBS was within acceptable tolerance in terms of measured strains, stresses, settlements, and deformations.