The use of glass fiber-reinforced polymer (GFRP) grids in reinforced concrete construction offers several advantages, such as high tensile strength and excellent corrosion resistance. This paper ...presents the results of experimental and numerical studies of the flexural performance of ultrahigh-performance concrete (UHPC) panels reinforced with GFRP grids. Such panels can be prefabricated and used as permanent formwork elements for bridge columns or walls. The mechanical properties of GFRP grids and UHPC were experimentally evaluated. The flexural performance of panels containing different reinforcement configurations was evaluated in three-point bending tests. The GFRP grids were found to be able to significantly enhance the flexural performance of the UHPC panels. A three-dimensional nonlinear finite element model was established by using ABAQUS, which incorporated the concrete damage plasticity model and can be used to predict the postfracture behaviors. The numerical model was experimentally validated by using the three-point bending test results and was then used for parametric studies. The studied parameters included the panel thickness and the layer number of the GFRP grids reinforcement. The proposed GFRP–UHPC panel system was shown to be promising for the development of lightweight, high-performance permanent formwork. Such formwork can be used in the accelerated construction of critical infrastructures for the enhancement of crack resistance and extension of the service life.
Cranes as indispensable and important hoisting machines of modern manufacturing and logistics systems have been wildly used in factories, mines, and custom ports. For crane designs, the crane bridge ...is one of the most critical systems, as its mechanical skeleton bearing and transferring the operational load and the weight of the crane itself thus must be designed with sufficient reliability in order to ensure safe crane services. Due to extremely expensive computational costs, current crane bridge design has been primarily focused either on deterministic design based on conventional design formula with empirical parameters from designers’ experiences or on reliability-based design by employing finite-element analysis. To remove this barrier, the paper presents the study of using an advanced surrogate modeling technique for the reliability-based design of the crane bridge system to address the computational challenges and thus enhance design efficiency. The Kriging surrogate models are first developed for the performance functions for the crane system design and used for the reliability-based design optimization. Comparison studies with existing crane design methods indicated that employing the surrogate models could substantially improve the design efficiency while maintaining good accuracy.
This study focuses on structural systems, which are particularly attractive for bridge design. Specifically, it investigates the seismic performance of single-column bridges, which are either ...conventionally designed, with the column monolithically connected with the ground (i.e. fixed-base), or designed with the column-footing system able to uplift and exhibit planar rocking motion during an earthquake. Although various researchers have studied the examined structures in terms of their seismic fragility, their seismic losses, post-earthquake functionality and resilience have received less attention. This paper redirects our attention to the main benefits of rocking design over the conventional (fixed-base) design in the aftermath of severe seismic hazard scenarios. The analysis reveals the considerably mitigated (short-term and long-term) seismic losses of the rocking structure compared to the pertinent losses of the fixed-base structure. In addition, the results show the remarkable functionality and resilience of the rocking structure after all the examined seismic hazard scenarios. Importantly, this work unveils that the post-earthquake financial benefits of the rocking structure can be further increased when the structure is carefully designed. In particular, even a small modification of its slenderness can lead to a substantial enhancement of its post-earthquake performance. The above findings illustrate the potential of the rocking structural system as an alternative seismic design paradigm for bridges and serve as the basis for a more rational and holistic seismic assessment framework of single-column rocking bridges.
The unified boundary trapezoidal modulation (TZM) control utilizing fixed duty cycle compensation and magnetizing current design for dual active bridge dc-dc converter is proposed in this paper. The ...fixed duty cycle compensation and magnetizing current design are first introduced to achieve the zero voltage switching (ZVS) of the power switches, which cannot be ensured with the conventional TZM control. As a result, all the power switches of dual active dc-dc converter can achieve ZVS and four switches can be turned off with very low current. Besides, based on the revealed power transfer characteristic, the power control variables including the duty cycles and phase-shift ratio can be unified without lookup tables or operation region division. With the proposed boundary TZM control, circulating current losses can be reduced and nonactive power is significantly suppressed according to the mathematic analysis, resulting in decrease of the conduction loss. A 1.6-kW laboratory prototype is built to verify the theoretical analysis and effectiveness of the proposed control.
•Maximum vertical displacement at midspan can be about ten times higher when vertical ground acceleration is considered.•Moment demands are increased in average by around 38% and are correlated with ...the spectral acceleration values.•Effects of vertical ground accelerations are stronger if the period of the vertical translation mode is lower.
Vertical ground accelerations are not always considered in bridge design practice, which is partially due to the lack of consistent recommendations in the design codes and standards. However, undeniably, the vertical ground acceleration component in an earthquake can be large. While the effects of vertical ground acceleration on bridges have been studied in the past, the focus has mostly been on performance of the substructure, especially columns. This study thus investigates the effects of large magnitude of vertical ground accelerations on the response of bridge superstructures as it can experience significant impact, particularly in the connections and bearing forces. To quantify the effects of vertical ground accelerations and compare the outcomes with existing design recommendations, an analytical study is undertaken on the seismic response of straight, skewed, and curved steel bridge superstructures with drop pier caps. The results show that the vertical accelerations can amplify the superstructure moment demands at the midspan and support locations by as much as above 100%. It is further shown that the current design practice to account for vertical ground acceleration effect is not sufficient for earthquakes with high vertical ground accelerations. Although the superstructure used in this study incorporated steel girders, the results are also applicable to bridges with concrete superstructure.
•Distributed fibre optic sensors (DFOS) can be integrated with FRP laminates.•Installation during production allows the analysis to be done from real “zero state”.•Integrated DFOS system can ...accurately measure extremely large strains.•Appropriate arrangement of DFOS sensors allows for displacement (shape) analysis.•Smart, self-diagnostic components can improve the safety of bridge infrastructure.
An increase in application of advanced materials and high-tech monitoring systems is being observed in bridge engineering in recent years. The main goal is aimed at optimizing maintenance costs spent during entire lifecycle of a bridge. The paper describes the concept of the smart fibre reinforced polymer (FRP) sandwich deck panel, dedicated for newly-designed and renovated bridges. This panel is equipped with the distributed fibre optic sensing (DFOS) system, integrated with composite laminates. The DFOS system is provided to control strain and displacement measurement, further used in the structural health monitoring of a bridge. The DFOS system is characterized by the following features: accurate, reliable and distributed strain measurements, possibility of assessing shape and displacements, detection of local damages, reliable protection of the sensors, no need for surface installations, high durability, measurements from the real zero state of the structural element. Exemplary results of distributed fibre optic strain and displacement measurements performed under laboratory conditions on laminate specimens as well as the beam cut from the prototype panels are presented and compared to conventional measurements and FEM predictions.
•The impact factors (IMs) of continuous beam bridges increase dramatically when resonance phenomena occur. Vehicle-bridge resonance is closely related not only to vehicle frequency and bridge ...frequency but also to the disturbance frequency caused by vehicle movement. Travelling velocity exerts an important influence on resonance. In most cases, the IM of a continuous beam bridge reaches its peak at a low travelling velocity.•Vehicle-bridge resonance may be caused by the first-order mode or the second-order mode of a bridge. Second-order curvature modes exert an especially crucial influence on the IMs of the negative moment at the interior supports. The maximum IM of continuous beam bridges at the interior supports is much larger than the maximum IM at the mid-spans, which is an important feature of the IMs of continuous beam bridges.•For the VM at the interior supports, the maximum DAF may be more than 1.7. If the design vehicular load specified in AASHTO code is used, the DLA of 33% is applicable to the force effect at the supports. However, when the same static traffic load standard is applied to both interior supports and mid-spans, a DLA of 75%, which is used for the deck joint in AASHTO code (2017), is necessary for the moment effect at interior supports.
The impact factors of multi-span continuous box girder bridges in highways are influenced by many factors, including road roughness, vehicle-bridge interactions (VBIs), and travelling velocity. Currently, the empirical formulas specified by bridge design codes are based on single factors (bridge length or fundamental frequency). These formulas yield inconsistent results that can differ widely. In this paper, the regularity of the dynamic amplification factors (DAFs) of continuous beam bridges is investigated by selecting 15 continuous beam bridges and conducting VBI analyses. The results indicate that the DAFs of the continuous beam bridges increase dramatically when resonance phenomena occur. The vehicle-bridge resonance is closely related to vehicle frequency, bridge frequency and the disturbance frequency caused by vehicle movement. The travelling velocity exerts an important influence on the resonance. In most cases, the DAF of a continuous beam bridge peaks at the velocity range of 40–60 km/h. Vehicle-bridge resonance may be caused by the first-order or second-order mode of a bridge. Second-order curvature modes exert an especially crucial influence on the DAF of the negative moment at the interior supports. The empirical formulas used in current bridge design codes fail to account for the influence of resonance and travelling velocity on the DAFs of bridges. The maximum DAF at the interior supports of the continuous beam bridges may exceed 1.7.
Expansion joints are a weak and fragile part of bridge superstructure. The damage or failure of the expansion joint will lead to the decline of bridge durability and endanger the bridge structure and ...traffic safety. To improve the service life and performance of bridge expansion joints, the ideal method is to use seamless expansion joints. In this study, starting from the commonly used asphalt mixture gradation of seamless expansion joint, and taking into account the actual situation of bridge expansion joint structure and environment in China, the gradation and asphalt-aggregate ratio are preliminarily designed. Through a Marshall test, the corresponding asphalt mixture is evaluated and analyzed according to the stability, flow value, and void ratio, and the optimal gradation and asphalt-aggregate ratio are determined. Finally, the asphalt mixture is prepared with the mixture ratio design, and the test results of an immersion Marshall test, fatigue performance test, and full-scale test verify that the asphalt mixture meets the road performance requirements of seamless expansion joints. On the basis of the experimental data, the performance of large sample asphalt mixture is continuously tested, compared, and optimized. The results show that the asphalt mixture ratio designed is true and reliable, which can provide reference for the optimal design of seamless expansion joint filler.
Building information modeling (BIM), which can efficiently manage the life cycle of structures, has been increasingly applied in the construction industry. However, it is difficult to implement BIM ...for existing structures, due to the differences between the design and as-built conditions. Point cloud data (PCD) can be obtained through the scan-to-BIM process, which builds a model based on the current state of the structure. The scan-to-BIM process is complicated for bridge structures and consumes significant time and resources. Therefore, this study developed a system to extract bridge design parameters automatically to reduce the time and resources for the scan-to-BIM process. The proposed automatic bridge design parameter extraction is performed in three steps: (1) noise reduction, (2) 3D transformation, and (3) parameter extraction. The validation test was conducted on the Osong test track fifth bridge in Nojang-ri, Jeondong-myeon, Yeongi-gun, Chungcheongnam-do, Korea. The system developed in this study successfully extracted the design parameters of the bridge from the PCD automatically, resulting in 0.8% error rate.
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