Recent Advances in Material, Analysis, Monitoring, and Evaluation in Foundation and Bridge Engineering

The carbon fiber reinforced composite polymer (CFRP) reinforcement is currently one of the most popular and effective methods for retrofitting and strengthening concrete structures. However, the nonprestressed CFRP reinforcement cannot make full use of the tensile strength of CFRP, the crack development of the stiffening beam cracks cannot restrain actively either. The failure of a strengthened or retrofitted structure with the nonprestressed CFRP is usually caused by the breakdown of the bond at the CFRP-epoxy interface or at the concrete-epoxy interface which is weaker than other places. Much effort has been made in the research community to improve the bond strength and restrain the crack development of the strengthening beam cracks. The full CFRP strength can usually be achieved in the strengthened or retrofitted structure with the prestressed CFRP. The prescrewed bolts fastening is another new mechanical fastening technique that is used to bond one material to another to improve the bond interface strength. Therefore, this paper introduces a new hybrid bonding prestressed technique that combines prestressed CFRP reinforcement and prescrewed bolts fastening. New tensioning equipment was developed to prestress CFRP. The strengthened reinforced concrete (RC) beam experiments have been finished to check the strengthening effect. Experimental tests have demonstrated that the new hybrid technology of prestressed CFRP sheets and prescrewed bolts can make full use of the tensile strength of CFRP and actively restrain the crack development of the strengthening beam cracks.

Highly flowable strain hardening fiber reinforced concrete (HF-SHFRC) has good workability in its fresh state and exhibits the strain-hardening and multiple cracking characteristics of high performance fiber reinforced cement composites (HPFRCC) in the hardened state. HF-SHFRC can be easily manufactured and delivered by ready-mix trucks for cast on the job site. Structural large-scale test results from several research programs also have shown that HF-SHFRC is effective in increased shear strength, displacement capacity, and damage tolerance in members subjected to large inelastic deformations. The results of two tests—long prismatic tensile test with continuous reinforcement and in-plane pure shear panel test—are carried out in this paper. Compared to conventional concrete, not only does it show much better mechanical performances, HF-SHFRC also presents lower crack potential and excellent crack width control. These characteristics of HF-SHFRC can further diminish work of repair, rehabilitation, and maintenance after extreme loading events and give infrastructure longer service life, as well as eventually lower life-cycle costs.

In this paper, a model for fracture and fragmentation, considering the heterogeneity of material properties, is employed to investigate the mechanism of spallation in fiber-reinforced concrete with various fiber and aggregate contents under impact loading. Numerical simulations show that there is a marked difference in the failure patterns among concrete with various fiber and aggregate content,s and the fibers can remarkably improve the tensile strength of the concrete, effectively preventing the initiation and propagation of cracks and inhibiting the occurrence of spallation. Moreover, numerical simulations capture the whole process of the propagation of incident compressive stress waves in the fiber reinforced concrete and the reflection of stress wave on concrete surface and the spallation failure of fiber-reinforced concrete induced by the reflected tensile stress wave, which is obviously different from the failure pattern of fiber reinforced concrete under static loads. The results in this study can provide some valuable reference for studies on the tensile properties and failure modes of heterogeneous quasi-brittle materials.

In this project, mixed-mode I-II fracturing of concrete has been investigated by using semi-circular chevron disk (SCCD) specimens. The numerical simulations have been done by using FRANC2D to analyze the experimental results. It was found that the notch crack initiation angle θ is a function of the notch crack inclination angle β. The crack initiation position changes when β ≥ 30° as the tensile stress and the shear stress leading to crack initiation extends along the upper side of the notch crack.

To investigate the eccentric compressive behaviors of reinforced concrete (RC) columns after freeze-thaw cycles, static eccentric compressive experiment of 30 RC columns after 0, 50, 100, 125 freeze-thaw cycles were made. The influences of different freeze-thaw cycles on the compressive behaviors of RC columns with different axial force eccentric distance were studied. The results showed that concrete cubes' mass, relative dynamic elastic modulus, and compressive strength decreased with the increasing of freeze-thaw cycles. Cracking load and ultimate load of RC columns decrease with the increasing of freeze-thaw cycles, whereas the deflection increased gradually. Some large eccentric compression failure specimen turned into small eccentric compression failure with the increasing of freeze-thaw cycles. Current concrete structure design code about ultimate load is still suitable for RC columns after freeze-thaw cycles.

A composite tubular truss bridge has been widely used in highway projects because of its short construction period and excellent mechanics characteristics. The joints' configuration and deformation of the composite truss bridge are of vital importance. Concrete filled tubular joint (CFTJ) has been approved as an effective way to enhance the loading capacity. Although the bonding force between concrete and rectangular tube is not distributed uniformly, this will cause the bond-slip behavior in the tube. To improve the interface bonding strength, perfobond rib is installed inside tube on the joint. This paper represents the damage mechanism of both CFTJ and CFTJ with perfobond rib through experiment calibration and numerical methods. The author proposes a new method to evaluate the steel joints' damage and fracture based on the stress-modified fracture strain model. The damage model, which considers both critical fracture strain and stress triaxiality, is calibrated by experiment to validate its accuracy. The user subroutine tool provided by commercial software ABAQUS was implemented to establish the damage model. Through analysis of CFTJ and CFTJ with perfobond rib, CFTJ with perfobond rib was found to have considerably much high constraint capability to concrete than CFTJ. The damage mechanism difference of the two types of joints is compared in the paper.

Piles are often designed to resist uplift actions resulting from wind, wave, earthquake, and underground water in high-rise buildings and long-span bridges. A rock-socketed under-reamed uplift pile can bear larger capacity with better performance, although its theoretical study is lagging behind the application, especially the prediction of bearing capacity. Based on the Hoek-Brown failure criterion of rock, a new simplified calculation formula is deduced according to the similar analysis and prediction method of capacity of under-reamed piles in soil. Two static loading tests were conducted on piles in Zifeng tower in Nanjing. The comparisons were made among predictions resulted from the simplified formula, other empirical methods, and field test results in Zifeng, including other test data in the literature. The results from simplified calculation formula agree well with the test results.

Stress concentration of the crossing oil pipeline is the main reason for pipeline failure. Currently, the study on stress analysis of large excavation crossing river oil pipeline is seldomly done. To ensure the safe operation of the pipeline, it is necessary to analyze crossing river oil pipeline stress distribution under operating conditions. In this paper, we do the numerical simulation of a certain oil pipeline with large excavation method using stress analysis software CAESAR II, come to the distribution of the pipeline, and check whether it can meet the strength requirements. Through the engineering case study, we concluded that the maximum stress generated at saddle weight under the operating conditions means that the saddle weight location is the dangerous section of the crossing river pipeline. After analyzing and comparing primary stress and secondary stress, we concluded that temperature difference is the main factor that generates stress in oil pipelines, whereas the effect of internal pressure is less.

Buried oil pipelines can traverse hundreds of kilometers of terrain with varied environmental and geotechnical conditions, such as through earthquake prone areas. These areas experience ground subsidence, which can lead to pipelines being suspended. The suspended segment of pipeline may result in pipeline rupture. Suspended oil pipeline stress safety usually has two contributing factors: the length of the suspended segment and water buoyancy. To research the influence that the two contributing factors cause on the stress of suspended pipelines, suspended pipeline stress needs analyzing using analysis software CAESAR II. Research shows that the buoyancy of water is more sensitive, and suspension pipe length of oil pipe is relatively small. This paper als provides some reference results for pipeline safety management.

Contact stress is related to the normal pressure at the contact surface between the foundation and the supporting soil. Contact stress distribution under the footingdepends on the footing rigidity. Rigidity of the foundation-soil system is qualified according to DIN (2005) using the coefficient of rigidity (K). At very low values of K, contact stress is highly concentrated under the footing center, and some unrealistic tension stresses are produced at edges due to the linear elastic soil. This tension disappeared with increasing K, and low compression stresses are produced. With increasing the rigidity, the center contact stress decreased and the edge compression stress increased. When the footing is rigid, the edge stress is highly concentrated and center stresses are low. The increase of concentration of edge stresses leads to increases in the resulting maximum moment. Thus, increasing the footing rigidity is increasing the maximum moment. Footing design using standards always results in a semi-rigid section, which produces concentration of stresses at edges and low stresses at the footing center. Therefore, the calculated maximum bending moment by assuming distributed contact stress, as standards and references, is lower than that calculated considering the effect of soil structure interaction. Most references state that the contact stress in cohesionless soil is concentrated at the footing center and is low at the footing edges. It cannot be done, according to the numerical analysis, except in two cases. Case 1 is the flexible footing, and it is not applicable because the designed footing is considered semi-rigid. Case 2 is the failure condition, which cannot be applicable by calculating footing dimension considering the allowable bearing capacity with an appropriate factor of safety.

This paper presents the effect of the tie beams that connect footings on the contact stress under footings applying the 2-D finite element (FE) technique. It showed that the tie beam rigidity has a significant effect on the average contact stress (P_sm) and corresponding differential settlement under footings. For the inner footing, P_sm decreased with the increase of the tie beam rigidity, whereas P_sm under outer footing increased with the increase of the tie beam rigidity. These effects tend to decrease the differential settlement under the footings. Tie beams redistribute the force acting on the footings. Therefore, it affects P_sm under footings that affects the settlement and the differential settlement. Due to the increase of outer P_sm, the outer footing is required to be increased to reach the standards safety factor for the bearing capacity of soil. In addition, tie beams redistribute the acting loads on footings that are carried from the columns. Therefore, it affects the straining actions of the superstructure members. This paper also clarified that the outer footing settled more than that was estimated regardless of the soil structure interaction. It is important to note that the tie beam rigidity also leads to increase the tilting of outer footings, which is necessary to be accurately calculated and checked with standard requirements.

This paper presents the effect of soil, foundation, and superstructure interaction on the contact stress and differential settlement. In recent design, designers have tried to resist the differential settlement by tie beams that connect the foundations. It is a complicated problem to calculate the differential settlement under the foundations taking into consideration the effect of the soil structure interaction. In addition, design of the tie beams that can resist the differential settlement by rigidity only result in a huge beam section with a huge reinforcement. Usually the tie beams are constructed as flexible rigidity due to the thickness-length ratio. Therefore, the tie beams cannot resist the differential settlement alone, and the superstructure members also shall work together with the tie beams. This paper presents the effect of the superstructure floor only without tie beams on the contact stress and differential settlement. Floor rigidity has a significant effect on the contact stress that increases the outer footing contact stress and decreases the contact stress under inner footing. This interaction leads to dampen the differential settlement under foundations. The floor rigidity affects the differential settlement, and the differential settlement affects the straining actions acting on the floor. In addition, the straining actions affect the design of the floor sections that affect the floor rigidity. This closed form solution still is in need of more research to simplify the solution. Curerntly it can be solved usinggeotechnical finite element (FE) programs that can simulate the superstructure members. Therefore, calculation of the secondary stresses on the floors concerning differential settlement calculated without soil structure interaction is wrong.

This paper presents the effect of superstructure rigidity on contact stress and differential settlement. Usually designers calculate the normal force in columns or walls using structural software with hinged or fixed supports representing the foundations. Thus, they calculate the contact stress by dividing the normal forces of columns by the foundation area. This way neglects the effect of the superstructure rigidity on contact stress and corresponding differential settlement. Differential settlement affects the normal forces that resulted in the columns, which affects the differential settlement. This closed form formula is need an appropriate solution. The solution is to take the soil, foundation, and superstructure interaction into account during the structural analysis and soil study. It is not applicable to study soil without structure or study structure without soil. For buildings that fail from excessive settlement, it may be because of the effect of the soil structure interaction. In addition, the buildings that fail due to the failure of some structure members may be because of the miscalculation of secondary stresses on the structure members resulting from the soil structure interaction.

Many structural designers represent footings as hinged or fixed supports in the structural models. Sometimes they represent the footing asagroup of springs withaspring's coefficient K (kN/m) equal to the area of modulus of subgrade reaction k_s (kN/m²/m). Designers assumed this modulus in different ways that do not consider soil structure interaction, such as the ACI way of calculation. ACI calculates k_s by dividing the allowable bearing capacity by 1.0 cm assumed settlement or calculated settlement without soil structure interaction. This paper shows that the soil structure interaction has a significant effect on the modulus of subgrade reaction. Usually designers assume K for edge as half of the inner one and the corner as quarter, which is based on the area that each spring represents assuming uniform k_s. However, k_s is not uniformly distributed under the footings. Considering the soil structure, interaction results change relatively in the normal forces in the columns. For the paper model, this change leads to increase in the outer columns and decrease the inner columns. For the complex structural systems, the distribution cannot be estimated. The change in the normal forces changes the resulting contact stress and settlement, which changes the resulting k_s. We are in need for more research to this effect to simplify an accurate calculation. Currently, use of a geotechnical finite element (FE) program that can consider soil, foundations, and superstructure effect is highly recommended.

In view of the characteristics of contemporary interdisciplinary research, this study is based on the knowledge of engineering technology and aesthetics linkages and focuses on a particular perspective—urban construction of the Three Gorges Reservoir review of the environmental planning. For ecological maintenance and governance issues were raised visual image of the reservoir environment, ecological landscape, and humanism envisaged; same reservoir planning the redevelopment areas, launched by the aesthetic sense, and further discusses the location advantages of culture, environment coordination, bridge facility, and many other features, which reflects the future sustainable development of the Three Gorges Reservoir combination of factors.

Fiber reinforced polymer (FRP) materials have been widely used in China's civil engineering construction. This paper briefly introduces the development and current application of FRP materials in China's engineering construction and scientifically analyzes the difficulties confronted.

Increasing concrete durability yields significant economic benefits, and the associated environmental benefits make durability a critical sustainability issue. Numerous factors deteriorate concrete in bridge structures, but several primary means are available to address this deterioration on both new and existing structures. One form of gel forming chemical, utilizing a blend of sodium silicates, delivered with a surfactant, has been demonstrated to be a viable, cost-effective solution on both new and existing concrete. Test data are provided that confirm the efficacy in preventing chloride ion (salt) penetration and freeze-thaw damage. Because a single application protects the concrete for the life of the structure, this product category demonstrates that sustainability issues need not be neglected in bridge construction or maintenance.

Bridges play a crucial role in connecting two places. Therefore, it is an important subject for concerned agencies to maintain a bridge's functionality and safety after its completion. As we know, steel bridges possess the advantages of light weight, high strength, and high ductility. However, the corrosion problems caused by aging of the coating surface of steel bridges affect structural safety and increase the cost of maintenance at operation stage. Currently, many bridges have already induced huge costs for their repair and maintenance before reaching their designed life ends This shows a lack of technique and quality of bridge design and management. This paper compares the life-cycle costs of the traditional paint coating method and that of the hot-dip galvanization method on steel bridges. From a short-term cost perspective, the paint coating method is more cost effective, because its unit cost is lower. However, from a life-cycle cost perspective, hot-dip galvanization is more cost effective, because itdoes not require maintenance for a long period of time. By applying the concept of life cycle in bridge construction, maintenance cost could be lowered. Therefore, it is worthwhile to look into its potential.

When rainfall-induced, debris flow landslides affect the Scottish strategic road network, the degree of damage to the infrastructure and the loss of utility to road users can have a major detrimental effect on both economic and social aspects of the use of the asset, and even small events may cast an extensive vulnerability shadow. The regional hazard and risk assessment that was undertaken following events in August 2004 to inform the process of allocating budgets and targeting works to the highest risk areas is described. The management and mitigation strategy that was developed is also described, a crucial element of this is the ongoing development of a rainfall trigger threshold to indicate conditions likely to produce debris-flow activity. The triggering of such debris flow events in the context of the historic and recent climate of Scotland is examined. Predicted changes to climate and their likely effect on landslide hazard and risk are also discussed.

In Taiwan, most of types of disasters can occur, such as debris flows, slope sliding, and rockfalls. The traditional instrument for slope monitoring cannot be effective concerningreal time and comprehensive layout. This study utilized WSN tilt meter to monitor the slope surface and understand the process of slope instability from the characterization variation of surface features. The first stage of the study was WSN tilt meter carried out in the National Highway No. 3, 3K+100 and used the WSN management platform to obtain the result. The WSN management platform can effectively collect the data, even if there is current bad weather. It also has a function that can fast and efficiently obtain data within a day, week, or month, average the data, then present the curve trend of the slope surface. The second stage was monitoring data analysis and laboratory tests including the calibration and simulation effect of the WSN tilt meter under various temperatures. The WSN monitoring system for slope had been used in operation for nearly a year. The data that can be gathered is useful not only for this study but also can provide useful information to the other management units, which can serve as a reference for slope stability monitoring.

To further improve landslide deformation prediction accuracy in Three Gorges reservoir, near-real-time monitoring systems were built in the subsequent phase of Three Gorges Project to substitute early manual monitoring. Shuping landslide, a typical reservoir type slide, is taken as an example; the near-real-time monitoring system that includes field continuous GPS sensors, communication infrastructure, and control center is described first. Then, based on the near-real-time monitoring data from June 20, 2012, to June 30, 2013, the spatial and temporal moving patterns are analyzed. Finally, by comparing the displacements to reservoir water fluctuation and rainfall, the conclusion is that landslide deformation is mainly triggered by the fast reservoir water level fall, and rainfall has a secondary influence. The results indicate that near-real-time monitoring can greatly improve the precision of understanding landslide behavior and the relation between movement and inducing hydrologic factors, which would be critical to protecting lives and property.

In this study, the use of geographical information systems (GIS) for evaluating landslide hazards was undertaken to complete an event-based landslide inventory and further evaluate effects of landslide on interruptions of mountain road networks. To achieve these objectives, satellite images before and after typhoon events were used to interpret landslides. Factors that influence landslides occurrence were selected for developing the landslide prediction model using a logistic model so that the criteria for successfully distinguishing landslides from nonlandslides were established. Analysis results show that the logistic model could be used in predicting road interruption due to landslides.