Construction Of Long-span Bridges Research Articles

Enhancing stress measurements accuracy control in the construction of long-span bridges

This paper introduces new contributions for construction procedures designed to enhance the robustness and precision of stress control in active anchorage and short presetressing units for long-span bridges, particularly addressing potential technical risks. The primary focus is on optimizing stress management for bridge stays, suspension cables, and short prestressing units by emphasizing a unified parameter: stress. The contributions of this research encompass (1) the introduction of advanced load cells for stress control in active anchorages and (2) the implementation of a novel synchronized multi-strain gage load cell network for short prestressing units, crucial in situations where prestressing losses can attain significant magnitudes. To validate these advancements, the authors present (3) a practical experience and results obtained from applying these methodologies in monitoring the structural response during the construction of the Tajo Bridge using the cable-stayed cantilever technique.

Numerical study of wind characteristics at a long-span bridge site in mountain valley

Wind loads play an important role in the design and construction of long-span bridges, especially for that built in mountain valley, and wind characteristics in mountain terrain are still unclear. To further understand the wind characteristics at a bridge site in a mountain valley, large eddy simulations were employed to comprehensively study the wind characteristics at the bridge site in an L-shaped canyon. Different wind directions consisting of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° were considered, and the wind characteristics on the main girder and towers, as well as the flow field, were comprehensively investigated. The results indicate that the mean and fluctuating wind characteristics are significantly different from those specified in the relevant specifications, and it is inappropriate to apply the specifications directly to mountainous terrain. When wind flows along a channel, it leads to a large wind speed amplification factor, strong non-Gaussianity, and large kurtosis and skewness. The steeper the slope of the mountain, the stronger the non-Gaussianity of the fluctuating wind. The coherence function remains nearly unchanged when the distance between the two points is constant, regardless of the location. The wind characteristics at the main girder and towers are so different that they should be considered separately and taken into account in engineering practice. This study provides a reference for the wind-resistant design of bridges and structures built on mountainous terrains.

Assessing the performance of palm oil fuel ash and Lytag on the development of ultra-high-performance self-compacting lightweight concrete with waste tire steel fibers

Recent advances in ultra-high-performance concrete (UHPC) materials have emphasized the necessity for continuous research. This imperative is particularly pronounced given the widespread demand for materials that facilitate the design and construction of long-span bridges, high-rise towers, and architecturally complex structures. The current study strives to address this need by developing a novel ultra-high-performance self-compacting lightweight concrete (UHPSCLWC). This research introduced Palm Oil Fuel Ash (POFA) and Lytag as replacements for specific conventional components. Specifically, 5%–25% POFA was utilized at 5% intervals as a partial substitute for cement to counter the heavy cement requirement typical of UHPC. Similarly, 5%–25% Lytag was used in 5% increments as a lightweight aggregate substitute for fine aggregate. To further optimize UHPC's production cost, waste tire steel fibers (WTSF) sourced from discarded truck tires were employed as primary reinforcement. This study comprehensively evaluates the rheological, physical, functional, and extreme durability properties of the UHPSCLWC and provides microstructural analysis. Test results suggest that samples utilizing 20% POFA and Lytag demonstrate optimal improvements across assessed characteristics, notably improved thermal and acoustic performance. At 90 days, the highest enhancement in compressive strength, modulus of elasticity, and modulus of rupture was 14.09%, 33.54%, and 17.44% for samples with 20% POFA and Lytag. Due to the unique properties and porous nature of Lytag, the hardened density of UHPSCLWC was reduced from 1993 kg/m3 to 1705 kg/m3. These modified samples also displayed enhanced durability, reduced mass loss and chloride penetration, and increased residual compressive strength when subjected to extreme conditions. Furthermore, the optimal inclusion of 20% POFA and Lytag in the mixture facilitated higher peaks of hydration phases, as observed in x-ray diffraction analysis. The findings of this study suggest the practical potential of POFA and Lytag in developing an innovative UHPSCLWC modified with waste tire steel fibers. This study adds valuable insights to the growing body of knowledge in the field of UHPC material development.

STABILITY AND RELIABILITY OF LONG-SPAN BRIDGE STRUCTURES

Introduction: Despite the fact that, in recent years, the construction of long-span bridges has been extensively developed, cases of bridge structures buckling in wind still occur, but the issue of their interaction with wind has not been sufficiently studied. Purpose of the study: We aimed to improve the structural integrity and operational safety of long-span bridge structures by conducting a computational and experimental study on the effect of various designs of aerodynamic dampers on the aerodynamic stability of such structures. Methods: The study was performed in two stages. At the first stage, preliminary two-dimensional numerical modeling was conducted to study the effect of various designs of aerodynamic dampers on the wind flow over selected bridge spans. Based on the results of the preliminary two-dimensional numerical modeling, we chose the most effective designs of aerodynamic dampers and made their models to conduct experimental studies on aerodynamic stability on a special test bench. Results: Based on the obtained computational and experimental results, we analyzed the effectiveness of various designs of aerodynamic deflectors and fairings used to improve the aerodynamic stability of the standard bridge structure under consideration. Discussion: For a span with one main girder, we determined the deflector design that reduces the vibration amplitude at high wind velocities.

The Time-Dependent Effect in Ultra High-Performance Concrete According to the Curing Methods.

Ultra-high-performance concrete (UHPC) is required to develop multifunctional concrete structures such as long-span bridges. During the construction of long-span bridges, girders exhibit significant differences in age because they use different curing days in the precast process. In this study, the performances of UHPC were compared when subjected to long-term storage under various conditions after 3-day steam curing. At 365 days, the compressive strength of steam curing is 197 MPa, moist is 191 MPa, and the air is 169 MPa. Based on these differences, prediction models were proposed for long-term performances. Furthermore, the development characteristics of compressive strength, modulus of elasticity (MOE), and flexural strength until 365 days of age were analyzed under air, moist, and steam conditions. Steam curing exhibited the highest level of strength development while air curing showed the lowest. Flexural strength showed no significant difference depending on age because steel fibers were mixed with UHPC; they significantly contributed to flexural performance. The results would contribute to recognizing differences in strength between members at sites where UHPC is applied and to managing high-quality structures constructed using precast members. These research results are expected to contribute to efficient member production and process management during the construction of large structures such as super-long-span bridges.

Static test research on steel bridge deck pavement structures paved by high-content hybrid fibre polymer concrete

Steel bridge deck pavement has always been a key and difficult point in the construction of long-span bridges. In practical engineering, common paving material is asphalt, and serious damage is caused on the pavement layer in the early stage. In this study, a high-performance high-content hybrid fibre polymer concrete was used as the paving material. A test was conducted on the small beam of the composite structure formed by the pavement layer and steel plate, and a positive/negative bending moment test was conducted to analyse the stiffness and bearing capacity of the composite structure. As revealed in the research results, the flexural and tensile stiffness of the structure and the bearing capacity of the composite structure showed superior performance, increased significantly with the pavement thickness, but increased slowly after the pavement thickness exceeded 80 mm and the increase in thickness contributed little to the bearing capacity. Under the simulated action of a positive/negative bending moment, the pavement layer still exhibited certain ductile failure features when the structure was bearing an ultimate load. This proves that high-content hybrid fibre polymer concrete exhibits suitable mechanical properties for steel bridge deck pavement.

Dynamic Response of Multitower Suspension Bridge Deck Pavement under Random Vehicle Load

Recently, the multitower suspension bridge has been widely used in long‐span bridge construction. However, the dynamic response of the deck and pavement system of the multitower suspension bridge under random vehicle load is still not clear, which is of great significance to steel‐bridge deck pavement (SBDP) design and construction. To reveal the mechanical mechanism of the steel‐bridge deck pavement of the multitower suspension bridge under traffic load, this paper analyzed the mechanical response of the pavement based on case study through the multiscale numerical approach and experimental program. Firstly, considering the full‐bridge effect of the multitower suspension bridge, the finite element model (FEM) of the SBDP composite structure was established to obtain key girder segments. Secondly, the influences of pavement layer, bending moment and torque, random traffic flow, and bridge structure on the stress of the girder segment were analyzed. Thirdly, the mechanical response of the pavement layer to the orthotropic plate under random vehicle load was studied. Finally, a full‐scale model of the experimental program was established to verify the numerical results. Results show that (1) the pavement layer reduced the stress of the steel‐box girder roof by about 10%. In the case of adverse bending moment and torque, the longitudinal and transverse stresses of the pavement layer were mainly concentrated in the stress concentration area near the suspender. Under the action of the random vehicle flow, the stress response of the pavement layer was increased by 40% compared with that under standard load. (2) Three‐tower and two‐span bridge structures have a great influence on the vertical deformation of the pavement layer under the action of vehicle load. Thus, the pavement material needs to have great deformation capacity. (3) The full‐bridge effect has a significant influence on the longitudinal stress of the local orthotropic plate, but a small influence on the transverse stress. (4) There is a good correlation between the experimental measurement results of the full‐size model and that of the numerical model. The research results can provide guidance for SBDP design and construction of the multitower suspension bridge.

Flutter Stability of a Long-Span Suspension Bridge During Erection in Mountainous Areas

In mountainous areas, more challenges are expected for the construction of long-span bridges. The flutter instability during erection is an outstanding issue due to flexible structural characteristics and strong winds with large angles of attack. Taking the suspension bridge as an example, the flutter stability of the bridge with different suspending sequences was investigated. First, the dynamic characteristics of the bridge during erection were computed by the finite element software ANSYS, along with the effects on flutter stability discussed. Then, different aerodynamic shapes of the bridge girder during erection were considered. The aerodynamic coefficients and the critical flutter state were determined by wind tunnel tests. Based on the above analysis, some structural measures are proposed for improving the flutter stability of the bridge during erection. The results show that the flutter stability of the bridge during erection is related to the suspending sequence and the aerodynamic shape of the girder. Owing to the structural dynamic characteristics, the bridge has better flutter stability when the girder segments are suspended symmetrically from the two towers to the mid-span. Considering the construction requirement that the bridge deck should be laid without intervals, this structural superiority is seriously weakened by the unfavorable aerodynamic shape of the girder. In order to improve the flutter stability of the bridge during erection, an effective way is to adopt some temporary structural strengthening measures.

Transforming gender relations in Nepal's trail bridge programme: policies and practice

This paper considers the extent to which the full and equal rights guaranteed in Nepal's constitution are reflected in the government's trail bridge programme (TBP). A review of the legal provisions and relevant literature was used to inform interviews and field enquiries at nine short-span trail bridges and one long-span bridge. The analysis indicates that the TBP is broadly gender responsive in its policies, but often falls short at field level. Analysis of the findings of the study was guided by five drivers of change for women's economic empowerment identified by the 2016 United Nations High-Level Panel. It considered the degree to which the TBP tackles adverse gender norms and promotes positive role models; addresses unpaid care work; promotes women's assets, representation and leadership; and contributes to a revision of gender-discriminatory laws. The paper concludes with five key suggestions for rendering the TBP more gender transformative: to address the time constraints imposed on women by unpaid care work; to ensure better facilitation of social processes; to strengthen women's leadership; to maximise women's income from wage labour through avoiding debt, turning it into assets and undertaking skills training; to incorporate inclusive community planning and construction of long-span bridges.

Effects of confinement in square hollow concrete column sections

Hollow concrete bridge columns have been frequently used in tall and long-span bridge construction due to their effective section properties and reduced weight. However, they are not widely used in seismic regions because the understanding of confinement effect in hollow concrete columns is quite limited. To improve the understanding of confinement effect in square hollow concrete columns, this paper presents a systematic computational study using the confinement configuration, wall thickness, and confinement reinforcement amount as the primary investigated parameters. The computational results show that two layers of transverse reinforcement connected with cross-ties provide the best confinement effect for square hollow concrete columns. In addition, both wall thickness and confinement reinforcement amount are found to not significantly affect the confinement effect in square hollow concrete columns with a wall thickness ratio in the range of 0.1–0.2 and confined with a single layer of reinforcement.

Nondestructive Evaluation of Non-Strand Defects in Stay Cable Specimens

Stay cable systems are used extensively for the construction of long-span bridges owing to their inherent advantages. In most cable-stayed bridges the steel strands within the main tension elements (MTEs) are grouted to provide a corrosion protection system. However, there could be segregated grout, voids, and water accumulation/infiltration within these voids in the ducts due to poor quality of the grouting material and grouting techniques. These locations may act as initiators for the corrosion of steel strands within the ducts, which can have serious implications on the load carrying capacity and safety of cable-stayed bridges. In this investigation, several nondestructive evaluation (NDE) techniques are evaluated to determine their ability to detect grout defects within the anchorage regions, end caps, and MTEs of the stay cable system. Four stay cable specimen mock-ups with known grout defects and voids were fabricated. NDE methods that were part of this investigation included ground penetrating radar, infrared thermography, electrical capacitance tomography, impact echo, sounding, ultrasonic tomography, ultrasonic pulse velocity, low frequency ultrasound, visual testing, and borescope. While a few NDE methods could identify voids and water infiltration defects within the high-density polyethylene (HDPE) MTEs, it is evident that there is still a need for a method that is effective in detecting grout defects within the metal ducts embedded in the anchorage region and metal MTEs. Although visual testing and borescope methods are effective in identifying the defects, prior information about the location of the defects is generally required.

Structural health monitoring baseline of Gómez Ortiz bridge using ambient vibration tests

Introduction: The construction of long-span bridges, especially box girder type, has been increasing in recent years in Colombia. Due to the importance that these structures represent for the infrastructure of the country, there is a need to monitor their structural integrity to analyze their behavior throughout their life cycle, detect changes caused by possible damages and establish maintenance plans. This monitoring can be carried out through the characterization of the dynamic properties of the structure. Objective: This study shows the results of the structural health monitoring baseline carried out in the Gomez Ortiz bridge. The dynamic characterization of the structure is performed and discussed, as well as the process of adjusting a numerical model based on the experimental results. Methodology: The dynamic characterization of the structure was carried out using the experimental technique based on ambient vibration tests. Four different techniques were used to post-processing the data obtained in these tests such as Peak Picking (PP), Frequency Domain Decomposition (FDD), Enhanced Frequency Domain Decomposition (EFDD), and the Stochastic Subspace Identification (SSI). Results: Experimental information of the dynamic properties of the bridge was obtained in the study, such as fundamental frequencies, modal shapes, and damping ratios. Conclusions: The results of the study demonstrated that the four techniques show similar results, except for damping ratios, which confirms the uncertainty of the experimental techniques to define this parameter.

Assessment of transmission length of prestressing strands according to fib Model Code 2010

Abstract The use of 18-mm prestressing strands is advantageous in the construction of long-span bridges. Transmission length is a significant parameter in the design of pretensioned concrete members. This study provides a unique set of experimental data to validate the applicability of using the fib Model Code 2010 to predict the transmission length and strand draw-in of 18-mm strands. Twelve pretensioned concrete beams were cast with high-strength concrete. Transmission lengths were measured at prestress transfer and at 28-day of age. The experimental results indicated the lower and upper bounds of transmission length specified by the code adequately predict the measured values.

Stay cable tension estimation using a vision-based monitoring system under various weather conditions

Recently, the construction of long-span bridges has increased due to continuous developments in materials and construction technologies. For long-span bridges that use cables, it is important to continuously monitor bridge safety by measuring cable tensions under construction and in traffic use. Among the many methods of measuring cable tensions, the vibration method, which estimates tensions based on cable shapes and natural frequencies, is currently popular because it is more cost-efficient and convenient than direct methods. Studies on the estimation of cable tensions using image measurement systems are actively underway, but they are used for routine inspections rather than in fixed systems for long-term monitoring of cable tensions. In this study, a vision-based monitoring system to measure cable tensions is installed. The system is applied to a cable-stayed bridge in traffic use. To verify the possibility of long-term monitoring cable tensions, images acquired under various weather conditions were used to estimate the cable tensions.

Assessing the potential of a commercial pulsed lidar for wind characterisation at a bridge site

Characterisation of atmospheric turbulence is a central step prior to the construction of long-span bridges. The present paper investigates the potential of a long-range scanning pulsed coherent lidar to measure the wind field at the inlet of a fjord. The wind velocity data acquired by the lidar is compared to the data recorded by sonic anemometers installed on the bridge. The focus is on the ability of the lidar to capture single and two-point statistics of turbulence in complex terrains. Satisfying results are obtained with the Line-of-Sight scanning mode, which provides the best sampling frequency (1Hz). The low temporal resolution and the low signal-to-noise ratio for the Range Height Indicator and the Plan Position Indicator scanning modes are important limiting factors in the pilot study performed. Better results may be achieved for a lidar measurement set-up which is adapted specifically for investigating coherence.

PERILAKU MEKANIS BETON MUTU TINGGI DENGAN VARIASI PENGGUNAAN SUPERPLASTICIZER

Concrete itself is quite popular in terms of usage in the field of construction (bridges, buildings, and dams). In large projects and unconditioned special (extreme) as the long-span bridge construction in the middle of the sea, pier construction, buildings and retaining walls high sea waves need to use high-quality concrete. To be able to make high strength concrete required fas value (water-cement ratio) is low, ranging from 0.20 to 0.30 (ACI, 1998). In high quality concrete workmanship in the field, to facilitate construction of concrete because considering using a little water, then a superplasticizer admixture materials needed to facilitate mixing concrete. This study was conducted to determine the performance of each in terms of value Slump superplasticizer, concrete compressive strength and split tensile strength of concrete. Calculation of SNI 03-6468-2000 material refers to the weight ratio of cement: fine aggregate: coarse aggregate of 1.00: 1.67: 2.15 with water cement factor of 0.317. Used to test a cylindrical specimen with a diameter of 150mm and height of 300mm which for the life of the test was made three (3) pieces of the specimen. Preparation and treatment of test specimens performed by standard procedures. The results showed that the use of superplasticizer type Napthalene Formaldehyde Sulphonate deliver results better compressive strength than the type superplasticizer Aqueous Solution Of Modified Polycarboxylate Copolymers is equal to 7.70%, but when viewed in terms of tensile strength and slump value (kelecakan) type superplasticizer Aqueous Solution Of Modified Polycarboxylate Copolymers provide better value Napthalene Formaldehyde Sulphonate when compared with that of 4.04% for split tensile strength and 22.22% for the slump value.

Integrated investigation of an incremental launching method for the construction of long-span bridges

This paper conducts a combined experimental and numerical study of the effectiveness of the incremental launching method for the construction and erection of continuous hybrid arch-girder bridges. To verify construction safety for these bridges, the investigation focuses on the stress and deformation levels of the launched structures during the launching process. The stress fluctuation of structural members is analyzed at critical launching stages under the mechanical and wind loads. It is shown that the temporary connectors between steel arches and longitudinal girders are critical to the structures during the launching process, and that the front connector of the first launched span needs specific attention to avoid fatigue and buckling issues. It is further demonstrated that the wind load has a significant effect on both stress and deformation, especially during the critical launching stages. Stiffening the key components is recommended to ensure the safety of bridge structures during the erection process under severe weather and wind conditions.

Vortex-Induced Vibrations on Cross Sections in Tandem Arrangement

The progressive increase in the construction of long-span bridges in recent years has led to an increasingly detailed study of the aeroelastic effects observed for structural components such as decks, towers and cables. The greater flexibility due to larger spans and optimized cross sections result in critical wind speeds below the design wind speed and would have therefore a certain probability of occurrence during the service life. Such critical wind speeds should be increased by introducing some modification on the cross section geometry.Cables for suspension and cable-stayed bridges are subject to vibrations caused by galloping or gust effects, though these typically occur at high wind speeds. Flutter instability is driven by a fundamental vertical and torsional mode coupling at very high wind speeds. On the contrary, vortex-induced vibrations (VIV) are associated with a single vibration mode and are characteristic of a lower wind speed range. Vortex shedding causes amplitude-limited oscillations, as VIV is not aeroelastic instability. However, it can pose a danger to the structural integrity of the deck or discomfort to users, which would require the temporary bridge closure. Towers of cable-stayed and suspension bridges can also suffer this type of aeroelastic phenomenon.This paper examines the VIV phenomena on towers and decks in tandem configuration by computational fluid dynamic (CFD) methods and experimental wind tunnel tests. This paper specifically discusses the influence of the gap that separates the two main sections and the presence of obstacles, as bracing elements, that affect the fluid–structure interaction and thus their aerodynamic properties. The choice of a proper geometry in the design stage can avoid such low-wind speed vibrations on sections in tandem arrangement.

Corrigendum to "Probabilistic sensitivity analysis of two suspension bridges in Istanbul, Turkey to near- and far-fault ground motion" published in Nat. Hazards Earth Syst. Sci., 12, 459–473, 2012

In the paper "Probabilistic sensitivity analysis of two sus- pension bridges in Istanbul, Turkey to near- and far-fault ground motion (Cavdar, 2012) a number of citations were missing, in the text and in the list of references. Below we publishthe necessary corrections. In section 1. Introduction: The text "The suspension bridges, Fatih Sultan Mehmet and Bosporus bridges, located on Bosporus straits in Istan- bul, a mega city of significant seismic hazard in Turkey. Is- tanbul has a population of approximately 15 million people, and is located astride the Bosporus, which divides it into Eu- ropean and Asian side." was missing a citation. The corrected text reads: "The suspension bridges, Fatih Sultan Mehmet and Bosporus bridges, located on Bosporus straits in Istan- bul, a mega city of significant seismic hazard in Turkey. Is- tanbul has a population of approximately 15 million people, and is located astride the Bosporus, which divides it into Eu- ropean and Asian side (Memisoˇ glu Apaydin, 2010)". The text "Suspension types of bridges are becoming more and more popular in the construction of long span bridges due to their many advantages, i.e. light in weight, efficient in load resistance, and of smaller cross sections. Suspension bridges which consist of main girders, towers and hanger are complicated structures." was missing a citation. The cor- rected text reads: "Suspension types of bridges are becom- ing more and more popular in the construction of long span bridges due to their many advantages, i.e. light in weight, ef- ficient in load resistance, and of smaller cross sections. Sus- pension bridges which consist of main girders, towers and hanger are complicated structures (Cavdar et al., 2010)". The text "The hangers are vertical and connect to the deck and cable with singly hinged bearing" was missing a citation. The corrected text reads: "The hangers are vertical and con- nect to the deck and cable with singly hinged bearing (Cavdar et al., 2011)". The text "It produces high input energy on structures in the beginning of the earthquake" was missing a citation. The cor- rected text reads: "It produces high input energy on structures in the beginning of the earthquake (Bayraktar et al., 2009)". The text "The ground motions with the velocity pulses recorded in the vicinity of an earthquake fault are quite dif- ferent from the usual far-fault earthquake ground motions" was missing a citation. The corrected text reads: "The ground motions with the velocity pulses recorded in the vicinity of an earthquake fault are quite different from the usual far-fault earthquake ground motion (Akk¨ ose et al., 2010)".

Research on the Automatic Walking-Type Launching System Applied in Jiubao Bridge Construction

In Long-span bridge construction by incremental launching method, due to its quiet heavy launching weight, long cantilever and complex structural stress. The dragging-type launching equipment commonly used at present no longer applies. Based on Jiubao bridge project, a new launching system of Automatic Walking-type Launching System (AWLS) was developed. This AWLS is a self-balancing launching system that integrates with functions of lifting, pushing and rectifying. It features highly automation, safety and reliability in operation. By using this system, Jiubao Bridge was successfully erected by incremental launching method for the first time as a three-span beam-arch composite bridge at home and abroad.