The design of beam-column joints is a crucial step of the design of seismic-resistant RC framed structures. Premature joint failure may prevent yielding of beams and the achievement of the target ...collapse mechanism. Hence, an effective capacity model is essential. In the past, Italian building code in force before NTC (2008) required that a minimum amount of ties, equal to that used in the column, be provided in the joint, but it did not stipulate any verification of the joint. Eurocode 8 (2005) and subsequently Italian NTC (2008 and 2018), recognize that shear in beam-column joint is higher than in columns and recommend the explicit verification of the joint. The suggested capacity model is based on stress analysis and is very demanding in terms of joint ties. The new draft of Eurocode 8 (2020) provides a different capacity model, based on research carried on by Fardis (2021), which better reflects the state of art on this topic under both theoretical and experimental point of view. This paper examines the capacity model for shear resistance of joints adopted in Eurocode 8 draft, underlining its advantages but also some difficulties in practical application. Based on a parametric analysis of a wide set of RC joints, it is showed that it is possible to assume that the joint rebars are yielded when the joint attains its ultimate limit state. This assumption does not determine any significant loss of precision in evaluating the shear resistance of the joint and leads to a capacity model consistent with other models adopted in Eurocode 8, e.g. those for shear resistance of RC beams. Furthermore, it allows a closed form solution of the problem that leads to a very simple procedure both for the verification of joint resistance and for the optimization of the design of horizontal and vertical rebars of the joint.
Contemporary construction heavily relies on advanced techniques for connecting and assembling structures. The most common example of construction assemblies is connecting structural and ...non-structural elements to a concrete substrate, often using cast-in and post-installed anchors. The widespread adoption of advanced concrete materials with high compressive strengths, such as Steel Fibre Reinforced Concrete (SFRC), in practical applications have led to challenges. Most of these stem from the absence of established standards and limited understanding of their impact on other structural elements, such as anchorage systems embedded in these types of substrates. This is because existing guidelines for anchorage design primarily rely on studies and test outcomes conducted on anchors embedded in Plain Normal-Strength Concrete (NPC). This creates a research gap when applying the CCD method to SFRC, particularly Ultra-High-Performance Fibre Reinforced Concrete (UHPFRC), where compressive strength can exceed 120 MPa. In this work, a comprehensive evaluation of the literature on anchorages in SFRC is conducted. Several parameters relating to the behaviour of anchorage in SFRC are listed and discussed in this work. Factors such as the fibre content, fibre homogeneity and orientation, and fibre type are determined to influence the capacity of anchors. The results of a total of 916 tests on the performance of anchorages in SFRC are carefully collated, classified, critically reviewed and analysed. The synthesised data highlights the trends, gaps, and evolutions on the research on anchorage in SFRC and illustrates the relationships and connections that emerge from the collective literature. The evaluation of the test results indicates that the scope of the CCD method can potentially be expanded to be used for the design of anchors in SFRC, with some modifications. Consequently, a modification factor is suggested for the CCD method using the analysed dataset. The insights from this comprehensive review on anchorages in SFRC can drive future research, guide revisions to industry standards and enhance practical construction applications.
•A comprehensive review and detailed examination of 916 tests on anchorages in Steel Fibre Reinforced Concrete (SFRC).•Identified key factors such as fibre content, homogeneity, orientation, and type impacting anchor performance.•Suggests modification factors for the CCD method to improve accuracy in designing anchors in SFRC.•Recommends increasing minimum embedment depth and edge distance based on fibre length.•Observed that fibre contents up to 80 kg/m³ enhance ultimate capacity of anchors due to improved fibre interlocking.
•A capacity design factor was defined to evaluate the system design and off-design operation strategy.•Key parameters that influenced on system performance under different capacity design scenario ...was quantitative analysised.•An universal system boundary of the ESR under different energy-matching scenarios was constructed.
In this study, a capacity design factor was defined to evaluate the system design and off-design operation strategy, and the mathematical model was derived for the relationship between the load supply and the users' demands under different capacity design modes and operation strategies, and the influence of the key parameters (load demands, load rate, matching degree) on system integration and operation characteristics under different capacity design scenario was quantitative analysised. Furthermore, the impact of energy-matching degree and system efficiency on the energy saving rate (ESR) was discussed, and based on the user demands, an universal system boundary of the ESR was constructed. Finally, the energy saving potential in different scenarios was clarified, and a case study was conducted using a data centre as an example, and the optimal capacity design mode was demonstrated.
This paper focuses on the operation design of a future public transit service adopting modular vehicles. The unique feature of modular vehicles allows for assembling and disassembling operations ...along each trip to dynamically adjust the vehicle formation at stations. We propose a mathematical model to determine the optimal scheduling and modular vehicle formation (i.e., capacity adjustment) on a single transit line with time-dependent travel demand. In particular, the limited availability of the modules at stations, as well as the incurred re-balancing cost of the modules during operation, is explicitly considered. The model is originally formulated as a mixed-integer nonlinear program (MINLP). We then apply exact reformulation techniques to recast the MINLP into an equivalent mixed-integer linear program (MILP), which can be solved to its global optimal solution by off-the-shelf solvers. To solve more practical problems with a long planning horizon, we then develop a two-step heuristic that combines a searching algorithm and a rolling horizon approach. The first exact solution method based on MILP reformulation can be used to derive the global optimal solution for the small-size problem, while the heuristic can solve large-size problems efficiently. Numerical studies demonstrate the validity of the formulation and the efficiency of the solution methods. Besides, the experimental results reveal that the timetable and vehicle formations change significantly with the time-dependent demands, and the modular transit services have remarkable advantages in reducing both operator’s and passengers’ costs.
•Study scheduling and formation design of the future public transit services.•Consider limited availability of the modules at stations.•Model the rebalancing operation and cost of the modular vehicles.•Formulate an equivalent linear transformation to derive the exact solution.•Propose a two-step sequential heuristic approach to solve largesize practical problems.
•A review of the different previous versions of Chapter 8 of Eurocode 8 is presented.•New definition of structural types is presented with graphical description.•Capacity design rules, ductility ...provisions and over-strength factors are presented for the different structural types.•Other changes including modified definitions, material properties and safety verifications equations are presented.•Some provisions regarding the application of non-linear static analysis of timber structures is introduced.
This paper presents the results of the ongoing work on the revision of the provisions for the seismic design of timber buildings in Europe included within Chapter 8 of Eurocode 8. The most recent research results and technical developments regarding both wood-based materials and structural systems have been implemented into the proposed new version together with the application of the capacity design to each structural system. The main objectives are to update the few and incomplete provisions included in the current version to the current state-of-the-art and to correct some misleading rules. This manuscript represents the authors’ point of view on the basis of a scientific research background and the design common practice regarding different key aspects in the seismic design of timber structures.
The railway power conditioner-based energy storage system (RPC-based ESS) is a promising technology to improve the regenerative braking energy (RBE) utilization and power quality of ac direct-fed ...(25 kV) and AT-fed (2 × 25 kV) railway power systems. However, despite its benefits from the technical perspective, economic viability must be concerned in industrial applications. The capacity is one of the critical issues affecting ESS performance in technical and economic aspects. Therefore, this paper presents a comprehensive approach to designing the capacity for the RPC-based ESS by considering multiple objectives, including the RBE utilization rate, power quality standard, and net lifetime benefit. The proposed approach develops a technical-economic model for the RPC-based ESS based on variables such as the system capacity for RBE utilization and power quality improvement, lifetime cost, and electric charge-based benefits. Moreover, the master-slave control strategy is employed to control the RPC-based ESS to implement the capacity design objectives. Finally, the correctness and effectiveness of the proposed method are validated by sufficient tests based on field load data of a Chinese traction substation.
•A steel bracing system dissipates the seismic energy through moment-rotation hysteresis loops of a fuse.•Cyclic tests and numerical analyses are performed to investigate the behaviour of the ...proposed system.•The influence of design parameters on theenergy dissipationcapacity of the system is investigated.•The easily replaceability of the fuse, while ensuring ductile system response, is assessed.•The fulfilment of limitations on the overstrength coefficient by simply changing the fuse cross-section is highlighted.
According to the capacity design method, earthquake-resistant structures should be able to dissipate energy through dissipative regions, which are expected to yield while the other structural members remain in the elastic field during seismic excitation. The non-linear response of a bracing system, in which energy dissipation relies on a fuse, is investigated through experimental tests and numerical analyses. Loading on the fuse is a combination of bending moment, axial, and shear load. Results provide valuable information on the influence of several design parameters, such as the member cross-section compactness, shape, and member slenderness. The stability of the moment-rotation hysteresis loops and the energy dissipation are assessed through cyclic tests.
To promote the utilization of the proposed bracing system in earthquake resistant steel structures, the work concludes by highlighting that the fuses are easily replaceable while ensuring ductile system response.
•Propose a continuum approximation model from a macroscopic point of view.•Prove that the investigated problem is equivalent to a simpler revised problem.•Decompose the original problem into a set of ...analytically solvable subproblems.
Time-varying capacity design holds an opportunity to reduce the energy consumption of urban mass transit systems, e.g., urban rail transits, bus rapid transits, modular autonomous vehicles. In this paper, we investigate the joint design of dispatch headway and vehicle capacity for one to one shuttle systems with oversaturated traffic to achieve the optimal tradeoff between general vehicle dispatching cost (mainly comprised of vehicle energy consumption) and customer waiting cost. We propose a continuum approximation model from a macroscopic point of view to reveal fundamental analytical insights into the optimal design. By introducing the concept of a preferred virtual arrival demand curve at the origin station, we prove that the investigated problem with possibly oversaturated traffic can be equivalently solved with a simpler revised problem where only unsaturated traffic is present. With this property, we decompose the original problem into a set of independent unit-time revised unsaturated problems that can be analytically solved in each neighborhood across the operational horizon. With two sets of numerical experiments, we show that the CA model offers near-optimum solutions with negligible errors very efficiently and we also verify the theoretical properties. Also, the effectiveness of time-varying vehicle capacity design is demonstrated in shuttle systems under both saturated and unsaturated traffic. Overall, the proposed CA model contributes to the CA methodology literature by extending the CA method for traditional transit dispatching problems with unsaturated traffic to the joint design of dispatch headway and vehicle capacity considering oversaturated traffic, adjustable vehicle capacities and other factors (e.g. minimum dispatch headway).
According to EN 1998-1, chevron concentrically braced frames (C-CBFs) are expected to provide limited ductility due to the interactions between the braces and intercepted beam. As a consequence, EN ...1998-1 recommends values of the behaviour factor (namely q=2 and q=2.5 in ductility class medium and high, respectively) lower than that (i.e. q=4) given for other concentric bracing configurations, e.g. both cross and single diagonal CBFs. The research activity presented in this paper is addressed to revise the design rules and requirements of EN 1998-1 for C-CBFs in order to improve the ductility and the dissipative capacity of this structural system. The study is organized in two parts: in the first part design rules recently presented in literature are assessed, while in the second part new design criteria are proposed and validated against the results obtained from incremental dynamic analyses carried out on 2D frames extracted from low, medium and high rise buildings.
•Design criteria for ductile chevron CBFs are proposed.•Design rules and requirements of EN 1998-1 are revised.•Increasing the stiffness of brace-intercepted beams improves the performance of CBFs.•Numerical analyses to assess the effectiveness of proposed rules are performed.•The proposed rules enhance the ductility and dissipative capacity of chevron CBFs.
The assembling rivet-fastened rectangular hollow flange beam (ARHFB) is a new type of cold-formed steel beam. The ARHFB section has two rectangular hollow flanges formed by U-shaped and C-shaped ...components that connected by self-locking rivets. A finite element model is developed to simulate 16 four-point bending experiments. Details of the modeling including finite element meshing, loading and boundary conditions, contact and analysis methods are presented. The accuracy of the developed finite element model is verified by comparing the ultimate moment capacity, applied load versus deflection curves, bending moment versus deflection curves, strain versus deflection curves and failure modes obtained from the tests and the finite element analysis. Based on the validated finite element model, a parametric analysis is carried out to discuss the effects of rivet spacing, section depth, flange thickness, and web thickness on the bending performance of ARHFB. The moment capacities of these sections obtained from the parametric study are compared with predictions from Australia and New Zealand, Chinese design standards for cold-rolled sections and the DSM (Direct Strength Method). It is found that GB50018 can conservatively predict the bearing capacity of ARHFB with a large error, while AS / NZS 4600 and DSM (Direct Strength Method) cannot provide reliable prediction results.
•A novel assembling rivet-fastened rectangular hollow flange beam (ARHFB) is analyzed in finite element model.•An extensive parametric investigation using a verified finite element model is conducted.•The feasibility of current design codes for ARHFBs is evaluated and judged.
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