Design, Construction, Rehabilitation, and Maintenance of Bridges

U-shaped aqueduct is superior structure form, which is extensively used in the china's South-to-North Water Diversion Project. However the analysis of oscillating modality and stability for U-shaped aqueduct coupling system has not been studied in-depth. In the analysis of oscillating modality of this paper, potential fluid method is applied in the fluid model taking into account the surface vibration. With reference to different water depths, the variation law of natural frequency of U-shaped aqueduct - fluid coupling system along with the water depth is investigated. Finally the ALE finite element method is applied to solving nonlinear fluid-solid coupling problem of coupling system on the basis of numerical simulation of U-shaped aqueduct random wind field by applying autoregressive moving average (ARMA) model. The time history of overturning stress and moment for U-shaped aqueduct under different conditions is obtained. And through cross-comparison between the data, the curves of the overturning stress and overturning moment under different water depths are obtained to reflect the stability characteristics of aqueduct - fluid coupling system. Thus it further reveals vibration mechanism of U-shaped aqueduct under the action of the stochastic aerodynamic force. It provides a reference to expand the analysis of dynamic properties for U-shaped aqueduct — fluid coupling system.

The cable-stayed aqueduct has become a new form of aqueduct after the beam and arched aqueducts. But the study focused on the dynamic characteristics of cable-stayed aqueducts is not enough. Based on the structure of cable-stayed aqueduct, the inner water is considered as added mass. The three-dimensional finite element model of fluid and the cable-stayed aqueduct is established to analyze the dynamic characteristics of aqueduct in different conditions. The results show that the dried modes and wet modes are analogous, but the natural frequencies of vibration are obviously different. The natural characteristics of vibration are three-dimensional and coupling with torsion mode. The cables have no effect on the fundamental frequency of lateral bending mode of vibration though they enhance vertical restraints to the aqueduct body.

Dynamic properties of Aqueduct-water coupling systems with rubber bearings were studied in this paper by considering the actual nonlinear influence of rubber bearings. In order to reflect the actual rubber bearings, Mooney-Rivlin model was applied to simulate the rubber material property and the steal panel was considered as two dimension solid model. The nonlinear contact was considered between rubber and steal panel. Fluid potential method was used to simulate the water in aqueduct by considering the fluid-structure coupling interaction. Once the finite element model of aqueduct-water coupling system with rubber bearings was developed, the frequency and the mode shapes were calculated for different depths of water. Compared with the dynamic properties of aqueduct-water coupling system without rubber bearings, the results show that the rubber bearings were effective in reducing the frequency of aqueduct structure, and the fluid-structure coupling system was shown the vibrational modes of aqueduct structure without the mode shape of water. This indicates that the mode shape of the fluid-structure coupling system was changed due to the nonlinear property of rubber bearings.

Base on the compressive tests of 24 lightweight aggregate concrete filled steel tubular (LACFST) stub under axially load, force-longitudinal strain curves, macroscopically characters of deformation, failure mode and the influence of parameters were studied. And different parameters, containing steel ratio, steel strength and concrete strength were considered. The test results demonstrate that confinement coefficient is a significant parameter to the mechanical properties of LACFST. With a small confining ratio, it has a decrease trend in later period and failure mode is drum-shaped type. Otherwise, the failure mode is shear type. Because of confinement, strength of core lightweight aggregate concrete (LAC) increases, and stiffness of LACFST is about 20% larger than the sum value of LAC stiffness and steel tube stiffness. Based on test considering the increase of LAC strength, calculation method of bearing capacity and its simplified method are proposed. Compare to other methods, its results are closer to the test ones.

18 lightweight aggregate concrete (LAC) specimens confined by steel tube under axial load was tested. Different influencing factors were considered, including concrete strength, steel ratio. Influence of different parameters to the carrying capacity of LAC, the relation curves of stress-strain and the failure mode were studied. It indicates that the failure mode of the specimen changes from Drum-shaped failure to shear failure when the strength of LAC increases. And the strength and ductility behavior of LAC under the confinement of steel tube are obviously improved. The confinement effect increases when the LAC strength induces and the steel ratio increase, and it is lower than normal concrete one. The strength criterion of the LAC confined by steel tube is established according to the test results. The calculation value obtained from this strength criterion is close to test value.

An approximate importance sampling technique based on DSmT (Dezert-Smarandache Theory) is presented for structural reliability evaluation in this paper. Belief functions in DSmT are well adapted for dealing with partial knowledge and uncertain information. To deal with the uncertainty induced by the use of approximate performance function, we apply belief functions to replace the indication function in traditional importance sampling techniques, and thus the error induced by approximate analysis is largely reduced. Moreover, this technique does not require the precise computation of structural failure hyper-plane and just demands few structural reanalysis. Examples are provided to show the computation precision and efficiency of this technique.

To find an alternative way of improving bonding and restricting sliding displacement, a new technique that combines FRP surface adhesion (EB-FRP) with a new type of mechanical fastening, namely Hybrid bonding (HB-FRP), is developed. The specimens are investigated and compared in a new modified beam-shear program in order to examine the bonding behavior of HB-FRP and EB-FRP. The finite element analysis is conducted to simulate the interfacial shear on the basis of different bolt prestress by Pretension 179 element and compact pairs of ANSYS. On the basis of experiments and the finite element analysis, the formula of calculating anchor length is suggested. The results show that HB-FRP is a more reliable strengthening technique. The new bolt-fastening technique does not rely on bearing to transmit the interfacial shear, but increases the interfacial bond by resisting the separation of the FRP laminate from the concrete substrate by the bolt pretension instead. This study contributes to direct the design and the construction of HB-FRP.

To research the effect of FRP-bolt strengthening technology and to examine the strengthening effect on RC beams in shear, contrast tests of FRP surface adhesion (EB-FRP) and FRP-bolt hybrid boding (HB-FRP) are conducted in laboratory on the basis of the destructive characteristics of aging RC beam bridges. The results of the EB-FRP and HB-FRP are compared. The influence of pre-cracking level and FRP strip spacing on RC beams strengthened in shear with HB-FRP is assessed particularly. The experiment results show that HB-FRP is a more reliable strengthening technique which can improve the shear capacity of beams. The new bolt-fastening technique does not rely on bearing to transmit the interfacial shear, but increases the interfacial bond by resisting the separation of the FRP laminate from the concrete substrate by the bolt pretension instead. This study contributes to direct the design and the construction of HB-FRP.

The problems such as difficult to obtain the training sample, slow to convergence for learn algorithm is encountered in damage identification using BP neural network. To solve the above problem, finite element model updating technique and Levenberg-marquardt algorithm are adopted. To verify the feasibility of such method, modal test for a simply supported reinforced concrete beam with rectangle section was carried out considering three different damage level. A finite element model for test concrete beam was updated using the modal test data, and then training sample was obtained. Levenberg-marquardt algorithm was adopted in BP neural network to improve the convergence rate of learning and realize the damage location and damage level identification of beam.

This research work involved surveying major road damages attributed to expansive soils with particular focus on Saudi Arabia. Roads and light structures in various parts of this country experienced damage as a result of moisture increase and environment changes to subgrade soils. Strains in asphalt pavement due to volume change in soils can lead to cracking and attract water seepage to lower formations. An attempt was made to link the road damage to the soil conditions, road geometry and road drainage arrangements. The parameters influencing the swelling process including thickness of pavement, slope of the shoulder, adjacent topography and drainage setup are discussed. Recommendations to achieve better road performance are presented. Applications of cut—off walls and dressing layers are suggested for certain conditions.

The traditional "shimming method" has some drawbacks when the incremental launching method is applied to a continuous beam with varying vertical curvatures at the bottom surface of its bottom slab. A new method of "adjusting the elevations of launching saddles" was studied and applied to the launch of the deck of the Hangzhou Jiangdong Bridge that is a self-anchored suspension bridge. A simulation model for the whole launch process was built by means of the finite element software ANSYS. An ideal scheme, including the initial pre-cambers of all launching saddles, when, where and how much to adjust, was attained by trial and error based on the principles of security, configuration, optimization and target, and based on the assumption of lowering frameworks at one time and the method of forcing displacement. The launching construction was completed successfully by the aids of the models and schemes updating with the launching process.

In this paper, a finite element model is developed using ADINA to simulate laboratory model tests of soil nails in expansive soils. In the numerical model, the soil nails are simulated using the rebar model and the effect of rainfall infiltration is described using fluid control equations. The numerical results are in good agreement with the model test results. The results indicate that soils near the top locations present uplift due to infiltration and swelling. The distribution of the horizontal displacements of the facing is like a bell with the largest displacement in the middle location. The axial force of soil nails increases with water infiltration.

The mechanical behavior of bridge pile foundation were complicated because overlaying mantle rock always has lateral thrust on piles foundation and free face of slope would have an influence on distribution of lateral resistance. The factors mentioned above could make it significantly different for piles foundational mechanical characteristics in slope from flat ground. Based on model tests on piles foundation in slope, the distribution of thrust, lateral resistance and its influence scope were discussed. According to the study of piles foundation stress in different loads combination and pier-column length, the mechanical characteristics of bridge foundation in slope were analyzed. The tests results show slope thrust distribution shape was simplified as a parabola. Approaching to certain depth of pile foundation, thrust would decrease with depth. Due to the existence of free face of slope, the lateral resistance was small and lateral resistance could be fully exerted when soil layer thickness is five or six times that of pile diameter. With an increase of the pier-column length, the moment of piles foundation has greatly increased and P-Δ effect of piles foundation in slope was more significant than in flat ground.

In foundation design, stress distribution is crucial for determination of bearing capacity and settlement. Stresses are generally calculated using elastic models proposed by Boussinesq and Mindlin which mainly consider foundation size and depth. In fact, stresses are also dependent on construction methods and mechanisms of stress distributions, but these factors are rarely considered in engineering design. This paper used the FEM to simulate the construction method and analyzed stress distributions in diaphragm wall and open caisson foundation. The study showed that the additional stress under a caisson foundation is always greater than that beneath a diaphragm wall foundation, thus showing the importance of the effect of construction method on stress distribution. It was also found that Mindlin's solution is more appropriate than Boussinesq's solution for calculation of total settlement of deep foundation even though the latter may provide better stresses near the bottom of the foundations. In addition, the settlement obtained using Mindlin's approach is between the settlement of caisson foundation and diaphragm wall foundation, and the discrepancy goes up with an increase in foundation depth.

This paper summarizes two bridge studies: 1) testing and numerical modeling of a newly constructed skewed hybrid high-performance steel (HPS) bridge; and 2) testing of a culvert bridge near a rock blasting. The first study is for construction verification and the second study is for possible blast damage identification. In the first study, truck load tests were conducted on the first North Carolina HPS 100W girder bridge after construction completion. LiDAR scan technique was used to measure bridge displacements under truck loading. A detailed 3D finite element (FE) model of the bridge was established. Results obtained from numerical analyses were compared with static load tests. In the second study, 3D LiDAR scans of a culvert were performed before and after rock blasting. Possible bridge position changes and damages were investigated. This research demonstrates two applications of LiDAR scan for bridge condition assessment.

The effectiveness of innovative polymeric coatings, polyurea and polyaspartic polyurea, to protect structural steel from corrosion was investigated through standard laboratory tests. The coating evaluation tests included salt fog test, QUV weathering test, adhesion test, and freeze-thaw stability test. These tests were used to assess the long-term performance of coating technologies compared to the conventional polyurethane type coatings, i.e. coating systems with inorganic zinc primer, epoxy intermediate coat and polyurethane topcoat. This paper presents part of results in the aforementioned evaluation tests. The results illustrate that polyaspartic coating systems are very promising for corrosion mitigation and can provide long-term adhesion strength for transportation steel structures. In addition, compared with the coating systems currently used by Department of Transportation's (DOT's), the polyaspatic coating systems performed equally well with even higher bond strength.

High-strength concrete (HSC) and glass fiber reinforced polymer (GFRP) bars are materials utilized in bridge construction to lower cost, reduce construction time, and increase service life of bridge structures. Recently, high-strength self-consolidating concrete (HS-SCC), a highly flowable concrete that does not require vibration, has been developed as a viable alternative to HSC for use in situations with congested steel or a need for rapid construction. Coupling HS-SCC with GFRP bars could create durable structures built rapidly. Several performance related issues remain to be investigated such as the behavior of prestress loss, shear, creep, shrinkage, thermal gradients, mechanical property development, time dependent behavior, and serviceability under varying loads before HS-SCC can be implemented in prestress applications. Two prestressed precast pedestrian bridges designed for rapid construction in Rolla, Missouri, USA, were constructed of HSC and HS-SCC to differentiate the mechanical and material properties between the two materials. In addition, the precast deck panels were reinforced with mild steel and GFRP to determine differences in the interaction between the reinforcement and decking materials. Instrumented systems and material tests were used to monitor the mechanical and material properties. This paper reports the results from fabrication through erection. In addition, a service load test is planned.

The proto-machine-made sand is a new environmental protection manufactured material, which is produced by technical improvement of stone cleaned by water firstly before crushed. It is always confined in engineering application because the content of stone powder is over the limit specified in current standard of Sand for Building. The paper introduces a series of test results of concrete in grade of C30 mixed with proto-machine-made sand. The contents of stone powder by mass of sand are 3 %, 7 % and 13 %, the cubic compressive strength were tested at ages of 3 d, 4 d, 7 d, 14 d, 28 d, 56 d, 90 d, 120 d, 150 d and 180 d. Based on the test results, the strength developing regularities of concrete affected by the content of stone powder are analyzed, the formulas are proposed for predicting the cubic compressive strength of concrete at any age. It is proved that the effect of stone-powder in proto-machine-made sand on concrete strength is virtually different from that of the crushed stone rust mixed with powdered mud in traditional machine-made sand, the limit content of stone powder lower than 5 % is not suitable for proto-machine-made sand to mix concrete in grade of C30.

To study the effects of hinge concrete on the integral loading properties of assembled prestressed concrete hollow slab bridge, the numerical model of whole bridge is build up by 3D finite element method. The hollow slab concrete, the hinge concrete, the pavement concrete and asphalt concrete are divided by solid elements, the prestressed reinforcements are divided by link-elements, and the ordinary steel bars are dispersed into corresponding concrete by equivalent modulus. The vehicle loads are arranged resulting in the unfavorable bearing status of hinge concrete. The construction sequence is also modeled by the calculation. The hinge concrete strengths are taken as reaching 100%, 80% and 60% of the design value. The analyses show that there is less influence of the hinge concrete strength on the integral loading properties of bridge, the reduction of hinge concrete strength will decrease its tensile capacity and lead to the cracks along hinge. If the cracks became serious under cyclic vehicle loads, the pavement above the hinge would also crack and the concerted actions of the assembled hollow slabs would be damaged and resulted in loading by single slab.

The rammed earth (RE) technique was developed thousands of years ago in China before it spread to the rest of the world. It was abandoned gradually due to the invention of modern construction materials, like concrete and steel. It has attracted renewed interests throughout the world in recent years due to its environmentally friendly features and low construction cost. The materials used in normally rammed earth include the binder (normally silt and clay) and the aggregate (normally gravel and sand). Cement or lime can also be found in modern stabilized rammed earth. This paper summarizes contemporary research in rammed earth technique, including material composition, physical and mechanical properties, as well as failure modes of RE structures. Since its mechanical properties vary widely based on different ingredients, the compression strength is normally used in the field for quality control. The future research and application potentials of this technique are also discussed in this paper.

The liquefied sand was certified as shear thinning non-Newtonian fluid according to its liquefaction flow characteristics through the laboratory tests. The relationship between the shear stress and the shear strain rate could be expressed by a power function. The flow constitutive model of liquefied sand was proposed and second-developed in FLAC3D. The simplified numerical method in FLAC3D was obtained to calculate the flow deformation of sand which was induced by the liquefaction. There were two steps regarding the simplified method. Firstly, the elastic model was used to get the initial stress field including shear stresses. Secondly, the flow constitutive model replaced the elastic model to get the liquefaction deformation under shear stress conditions. The simplified method was used to analyze the liquefaction deformation of sands under the shaking table tests. Various influence factors were discussed such as the slope of liquefied soil layer, texture coefficient, flow index and elastic parameters. It was indicated that the texture coefficient and the flow index of the liquefied sand were the major factors controlling the deformation.

For the application and dissemination of the new proto-machine-made sand in concrete structural engineering, tests were carried out to study the drying shrinkage of concrete in strength grade of C60 affected by the content of stone powder in proto-machine-made sand. The contents of stone powder by mass of proto-machine-made sand were 3 %, 5 %, 7 %, 10 %, 13 % and 16 %. The drying shrinkage strain of concrete at the ages of 3 d, 7 d, 14 d, 28 d, 56 d, 90 d, 120 d, 150 d and 180 d were measured according to the standard method. Based on the test results, the drying shrinkage regularity of concrete affected by content of stone powder in proto-machine-made sand is analyzed and compared with that of similar test of concrete with traditional machine-made sand, the predicting formulas are proposed.

Hybrid-Bonding of FRP (HB-FRP) is one of the developing practicable technologies for repairing concrete structures. Previous studies showed HB-FRP system could limit the interface debonding failure of FRP effectively and improve flexural capacity and ductility of structures. Previous experimental studies have focused on strengthening the unbroken beams, but defective beams were usually strengthened in practical projects. Thus unbroken beams and defective beams of different degree had been researched separately in this paper. According to the defective degrees and strengthened methods, 12 beams were divided into 4 groups to do destructive loading tests. The impact on the flexing resistance for unbroken beams and defective beams of Hybrid-Bonding of FRP were systematically researched. HB-FRP system had great advantages in ductility and flexural capacity of RC defective beams compared with EB-FRP (External bonded FRP) system through comparative analysis of load - deflection curves. The results could provide a theoretical basis and experimental evidence for reinforcing different defective degree beams.

The primary objective of this study is to obtain the statistical parameters of the members for calibration of the steel highway bridge reliability design. Firstly, the stochastic parameters of roll steel and sections of steel highway bridge member are calculated based on the extensive survey and investigation across China. Secondly, three aspects of member's uncertainty which are the uncertainty of materials properties, geometric parameters of members and calculation model are analyzed respectively. Thirdly, the stochastic parameters of five typical members of two commonly used steels—Q235q and Q345qD—in steel highway bridges are calculated.

In this paper, dynamic properties of short-span cable-stayed bridges are analyzed by finite element method with emphasis on effect of cable's tension and cable model. The results show that the cable's tensions have great effect on the dynamic property of the short-span cable-stayed bridges, especially the longitudinal frequency. Single element cable model (SECM) and Multi-element cable model (MECM) are used for frequency domain and response in time domain analysis of short-span cable-stayed bridge. The results for frequency domain are similar for SECM and MECM, while difference in time domain response can be found.