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Purpose – The bridge expansion joint (BEJ) is a key device for accommodating spatial displacement at the beam end, and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge. For long-span railway bridges, it must also be coordinated with rail expansion joint (REJ), which is necessary to accommodate the expansion and contraction of, and reducing longitudinal stress in, the rails. The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway (HSR) long-span bridges in China, and to propose a performance-based integral design method for BEJs used with REJs, from both theoretical and engineering perspectives. Design/methodology/approach – The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development. Results of a survey of typical BEJ faults were analyzed, and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load. Based on the above, a performance-based integral design method for BEJs with maximum expansion range 1600 mm (±800 mm), was proposed, covering all stages from overall conceptual design to consideration of detailed structural design issues. The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios, full-scale model testing, and field testing and commissioning. Findings – Two major types of BEJs, deck-type and through-type, are used in HSR long-span bridges in China. Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap, abnormally large longitudinal frictional resistance, and flexural deformation of the scissor mechanisms. These faults influence BEJ functioning, and thus adversely affect track quality and train running performance at the beam end. Due to their simple and integral structure, deck-type BEJs with expansion range 1200 mm (± 600 mm) or less have been favored as a solution offering improved operational conditions, and have emerged as a standard design. However, when the expansion range exceeds the above-mentioned value, special design work becomes necessary. Therefore, based on engineering practice, a performance-based integral design method for BEJs used with REJs was proposed, taking into account four major categories of performance requirements, i.e., mechanical characteristics, train running quality, durability and insulation performance. Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ; the latter factor in particular has a decisive influence on train running performance at the beam end. Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface. The static and dynamic performance of the newly-designed BEJ with expansion range 1600 mm have been confirmed to be satisfactory, via numerical simulation, full-scale model testing, and field testing and commissioning. Originality/value – This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China, along with novel insights into their design.

The date palm is a giant plant that must be cleaned annually, which can be the first source various raw materials compared to other woods that are cleaned once every four years, such as cork. In Algeria, there are millions of palm trees that produce a significant amount of raw materials annually, but unfortunately they are not exploited in industry. This paper presents an experimental study on mechanical behaviour of four bio-sourced sandwich materials differentiated by their core types. The skins of these sandwiches are made composite material composed of rachis fibers and epoxy resin; however the cores are made of: 1) raw petiole and petiole agglomerate with two sizes (0 -1 mm and 1-3 mm) and 2) cork agglomerate for comparison. The comparison between these sandwiches is based on the overall stiffness which is determined by three point bending tests. The results obtained for all sandwich materials show that the overall stiffness of the Petiole agglomerate with the size (0mm-1mm)/rachis fibers-epoxy resin is higher than the other sandwiches. Thus, we have carried out a complementary damage study to this last sandwich material based on delamination tests. It turns out through this study the good resistance of this new sandwich to delamination compared to other previously studied materials. [ABSTRACT FROM AUTHOR]

The main navigable bridge is a three-tower steel box girder cable-stayed bridge with a span of 78 + 187 + 2×550 + 187 + 78 m. The design reference wind speed is 42.3 m/s. The main navigation span can navigate 100,000-ton ships. In order to improve the overall stiffness of the bridge under unbalanced live loads, some measures are studied, such as the restraint conditions, the stiffness of the tower, the stiffness of the beam, the number of stay cables in the side and central tower, and so on. Through the wind tunnel test research, the control measures for the buffeting performance of the double cantilever are clarified. According to the IABSE vessel collision model, the vessel collision force is determined. A double-layer collision protection structure is used to protect the bridge and reduce vessel collision damage. In order to improve the structural durability, high-performance epoxy steel bars are used in the splash zone. The cable-anchor beams of the towers are made of weathering steel. Maintenance vehicles are installed in the main beam which is 1.63 km. Through the above measures, the structural performance is guaranteed. [ABSTRACT FROM AUTHOR]

Capacity of pile group is the summation of the individual piles capacity with influence of spacing between the piles. Pile groups usually have the same length, so if the spacing between piles is too close, the zones of stress around the pile will overlap and the ultimate load of the group is less than the sum of the individual pile capacities especially in the case of friction piles, where the efficiency of pile group is much less. In this research the optimization of bearing capacity and unsymmetrical settlement of cap in the vertical pile group using genetic algorithm were studied. Friction pile in granular soil, with different length and arrangement were investigated to find the best performance of the group for the axial stiffness, bearing capacity and unsymmetrical settlement. The criterion of optimization is the volume of concrete needs for piles and cap. Two patterns of 5×5 pile groups (row variation and squared variation) are studied in this research. The analysis of pile group to find bearing capacity was conducted using the finite element software (Fb-pier) and for optimization used evolutionary genetic algorithm method.

This study explores the feasibility of estimating overall shear wave velocity for levees to detect weak sections by using microtremor measurement. Microtremor measurement is carried out on the crest and near the toe of the levee embankment simultaneously by placing servo-type velocity sensors perpendicular to the levee axis. Then, transfer functions are calculated using the horizontal motions. Finally, overall shear wave velocity structure is identified so that the peak frequency of the transfer function and the fundamental frequency of finite element model of the levee that has the same cross section coincide. The identified shear wave velocities are mostly consistent with shear wave velocities estimated based on SPT blow counts. Hence, this method is feasible to detect weak sections along levees. [ABSTRACT FROM AUTHOR]

The current regulation uses pedestrian lower legform impactor test to assess the pedestrian leg protection performance of vehicles, which imposes new design requirements on vehicle's front-end structure. In this paper, a stiffness-based control strategy is proposed for assisting engineers to quickly identify the causes of excess tibia acceleration over regulation limit. By the combination of different position, dimension and stiffness parameters of front-end structure, 24 FE crash simulations are conducted to analyze the effects of design parameters of front-end structure on its overall stiffness and tibia acceleration. In the end a real vehicle example for the application of the proposed strategy is given. [ABSTRACT FROM AUTHOR]

This paper presents the development of a numerical model for simulating tree stability considering tree-root-soil interaction. This model is validated against tree pulling test results for three tree species by comparing the derived load-deflection curves from the numerical model with those obtained from the field experiments. Experimental overall stiffness of a tree is calculated based on the tree pulling tests and is implemented in the numerical simulations. A series of numerical tree stability analyses for a tree with various geometries and properties is performed to investigate the effects of influencing parameters on the lateral resistance behavior of the trees. Through comparison with the results of tree pulling tests, the three-dimensional (3D) numerical results from the present study is found to be in good agreement with the general trend observed from the field measurements and thus, the numerical model represents a realistic tree-root-soil interaction for laterally loaded trees. In addition, numerical analysis results confirm the fact that the lateral behavior of the tree is strongly dependent on the tree geometries (i.e., trunk diameter and rooting depth), and elastic modulus of trees and soils. [ABSTRACT FROM AUTHOR]

l A rigorous analytical solution of interfacial stresses and overall stiffness of plated beams are obtained. l Influences of the plate and interface properties are systematically studied. l Limitation of the widely adopted assumption of the same curvature of host beam and plate is clarified. l Critical values of the plate and interface parameters indicating overall stiffness saturation are proposed. Beam structures with partially covered plates have been widely used in macro members and micro devices, such as concrete beams with fiber-reinforced plastic (FRP) plates, aircraft structures with FRP patches and smart beams with actuators/sensors. Based on the two-parameter elastic foundation model and the classical Euler–Bernoulli beam model, a rigorous analytical solution of interfacial stresses and overall stiffness of plated beams is obtained, and influences of the interface and plate properties are presented. The limitation of the assumption of the same curvature of host beam and plate, which was widely adopted in previous studies, has been clarified. And the present solution is applicable to a wider range of interface and plate properties, especially for large values of plate thickness, plate modulus and interfacial stiffness, as well as small values of plate length. The saturation phenomenon of overall stiffness is observed in some cases, and critical values of the interface and plate parameters corresponding to the saturation limit of overall stiffness can be referred for design. The results can provide guidance for the optimal design of widely-used plated beams to prevent premature interfacial debonding and acquire better overall performance, such as higher stiffness with FRP plates or shape control with actuators, by manipulating the interface and plate properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]