Mascolo, Ida

Mascolo I., Guarracino F., Sarfarazi S., Della Corte G.

Sarfarazi S., Shamass R., Mascolo I., Della Corte G., Guarracino F.

Stainless-steel has proven to be a first-class material with unique mechanical properties for a variety of applications in the building and construction industry. High ductility, strain hardening, durability and aesthetic appeal are only a few of them. From a specific point of view, its nonlinear stress–strain behaviour appears capable of providing a significant increase in the rotational capacity of stainless-steel connections. This, in turn, may provide significant benefits for the overall response of a structure in terms of capacity and ductility. However, the bulk of the research on stainless-steel that has been published so far has mostly ignored the analysis of the deformation capabilities of the stainless-steel connections and has mostly focused on the structural response of individual members, such as beams or columns. For such a reason, the present study aims to contribute to the general understanding of the behaviour of stainless-steel connections from a conceptual, numerical and design standpoint. After a brief review of the available literature, the influence of the use of stainless-steel for column–beam connections is discussed from a theoretical standpoint. As a novel contribution, a different approach to compute the pseudo-plastic moment resistance that takes into account the post-elastic secant stiffness of the stainless-steel is proposed. Successively, a refined finite element model is employed to study the failure of stainless-steel column–beam connections. Finally, a critical assessment of the employment of carbon-steel-based design guidelines for stainless-steel connections provided by the Eurocode 3 design (EN 1993-1-8) is performed. The findings prove the need for the development of novel design approaches and more precise capacity models capable of capturing the actual stainless-steel joint response and their impact on the overall ductility and capacity of the whole structure.

Mascolo I.

Abstract. Long-span suspended bridges rely upon networks of tensed cables that carry the weight of the deck. The networks of cables are generally connected to a number of vertical towers (pylons) that transfer the forces to the foundations as in the case of cable-stayed bridge. Their structural behaviour is highly influenced by the pretension forces on account of the redundancy of the structure. Several methods have been proposed for determining pretension the forces in the cables, such as Load-Balance Method, Iterative Unit Load Method, Force Equilibrium Method, Zero Displacement Method. The present study aims to investigate the influence of geometrical non-linearities on the optimization of the design. To this end, the Force Equilibrium Method is here extended and compared to the use of a Finite Element commercial package, since this is the standard method in everyday engineering practice. The comparison between the Force Equilibrium Method and FEM results shows that the first method, in spite of its simplicity, is able to provide a reasonable and reliable alternative to the more complex non-linear FE approaches.

Cutolo A.

Abstract. In recent years, efforts have been made to compare equilibrium solutions of masonry domes obtained through different methods. The research summarized in the present paper focuses on the evaluation of the equilibrium of masonry domes in the context of the classical membrane theory, in comparison with more sophisticated finite element models. In particular, we consider solutions, with vanishing tensile stresses, for domes under gravity loads. The equilibrium problem is traced back to the equilibrium of a thrust surface under the assumption of no-tension material in the sense of Heyman (i.e., no tensile strength, infinite resistance in compression, and no slide along fracture lines). A finite difference discretization of the equilibrium equation is proposed and the obtained solution is compared with results from a nonlinear finite element analysis. The good agreement of the results shows that both finite difference and finite element approaches represent reasonable and reliable alternative tools.

Babilio E., Mascolo I., Guarracino F.

The dynamic buckling of circular rings is a pervasive instability problem with a major impact in various fields, such as structural, nuclear and offshore engineering, robotics, electromechanics, and biomechanics. This phenomenon may be simply seen as the complex motion that occurs deviating from the original circular shape under, for instance, any kind of time-dependent forcing load. Despite the fact that this topic has progressively gained importance since the mid-20th century, it seems that the same points have not been made completely clear. In fact, even some subtleties in the derivation of classical static buckling load may still give rise to misinterpretations and lead to misleading results. A fortiori, research concerning the nonlinear dynamics of rings still suffers the inherent difficulties associated with different possible analytical formulations of post-buckling dynamics. Advancement in this respect would be relevant, both from a theoretical and a practical point of view, since the applications are endless, with countless possibilities, especially in the biomedical and biotechnological fields: buckling-driven transformations of thin-film materials for applications in electronic microsystems, self-excited oscillations in collapsible tubes and pliable fluid-carrying shells, vocal-fold oscillations during phonation and snoring, pulse wave propagation in arteries, closure and reopening of pulmonary airways, stability of cardiac and venous valves during vascular surgery, stability of annuloplasty devices, flow-induced deformation and ultimate rupture of a cerebral aneurysm, and much more. The present article, in the framework of a critical review of the classic formulation of elastic ring buckling, proposes a straightforward approach for the nonlinear dynamics of an elastic ring that leads to a Mathieu–Duffing equation. In such a manner, some possible evolutions of the system under pulsing loads are analyzed and discussed, showing the inherent complexity of its dynamic behavior.

Mascolo I., Guarracino F.

Elastic buckling of circular rings under external pressure is one of the oldest and most ubiquitous problems in structural engineering and the first meaningful solution to it was proposed by Levy (1884). This basic solution, based on the Euler–Bernoulli beam model, can be found in the vast majority of textbooks on stability. However, there are a number of subtleties in the formulation of the problem which need to be taken into account so and one should always be well aware of the underlying analytical fundamentals, especially in the current world which strongly relies on numerical analyses. Therefore, starting from the general nonlinear kinematics of the problem, the buckling load is revisited by means of a direct energy approach and on the basis of an in-depth discussion of the classic kinematic hypotheses. Possibly different outcomes are pointed out and remarked. Finally, some inconsistencies which unexpectedly arise in pursuing the solution by means of commercial FE packages are presented and commented. • Elastic buckling of circular rings under different types of pressure is analysed and reviewed. • Discrepancies between theoretical and numerical results are discussed. • The possible drawbacks of using FE codes without making reference to fundamental solutions are pointed out.

Mascolo I., Gesualdo A., Olivieri C., Fortunato A.

Cutolo A., Guarracino F., Olivieri C., Mascolo I.

Olivieri C., Cennamo C., Cusano C., Cutolo A., Fortunato A., Mascolo I.

The present paper applies the Linear Arch Static Analysis (LASA), which models the masonry material as unilateral, i.e., No-Tension material in the sense of Heyman, and the Safe Theorem of the Limit Analysis to the study of masonry spiral stairs. A comparison is made with a refined FE analysis of the same problem, obtained by means of the ANSYS Parametric Design Language (APDL). The objective is to prove that LASA can be a valid alternative to other more complex numerical methods, such as FE, especially when the modeling parameters, such as the boundary conditions, cannot be exactly defined. The case study of a small spiral staircase placed in the tower of Nisida, a small island close to Naples, Italy is taken into consideration. The results show that the LASA analysis provides results that fall within two limit FE cases in terms of stress and overall thrust, providing at the same time a meaningful insight into the equilibrium state of the structure.

Fortunato A., Gesualdo A., Mascolo I., Monaco M.

Malena M., Angelillo M., Fortunato A., de Felice G., Mascolo I.

Settlements severely affect historic masonry arch bridges worldwide. There are countless examples of structural dislocations and ruins in recent years due to severe settlements at the base of pier foundations, often caused by shipworm infestation of wooden foundations or scouring and riverbed erosion phenomena. The present paper proposes an original way to approach the failure analysis of settled masonry arch bridges. The proposed method combines two different 2D numerical models for the prediction of masonry arch bridge capacity against settlements and for safety assessment. The first one is the Piecewise Rigid Displacement method, i.e. a block-based limit analysis approach using the well known Heyman's hypotheses; the second one is a continuous Finite Element approach. The case study of the four-span Deba Bridge (Spain, 2018) failure is presented with the aim to illustrate how the methods work. The failure analysis produced satisfactory results by applying both methods separately, in confirmation of their reliability. Their combination also allowed to obtain a significantly reduction in computational cost and an improvement of prediction accuracy. A sensitivity and a path-following analysis were also performed with the aim to demonstrate the robustness of the presented method. The obtained simulations highlighted that the results do not depend on the friction angle and that a proper prediction of the evolution of the structural behavior can be obtained only taking into account geometric nonlinearities. Such results demonstrate once again that in settled masonry arches geometry prevails over the mechanical parameters. The current study paves the way for the fruitful use of the proposed approaches for a wider range of applications, as, for example, the mechanism identification or the displacement capacity assessment of masonry structures under overloading as seismic loads.

Guarracino F., Mascolo I.

Buckling of circular rings under external pressure is one of the oldest problems in structural engineering and the first solution to it was proposed by Levy in 1884. The basic solution for the Euler-Bernouilli beam can be found in the vast majority of textbooks on stability. However, in a world which strongly relies on FE commercial packages, one should be always well aware of these fundamentals and in the present work some considerations arising from the numerical treatment of the problem by means of FE and from the classic analytical solutions of the differential equations are discussed in order point out some inconsistencies which may arise the numerical analyses.

Mascolo I., Modano M.

The study deals with the optimum suspended-deck bridge (i.e. suspension, cable-stayed and tied-arch bridges) design through cable adjustment. An easy linear analysis procedure is proposed based on ...

Bieniek Z., Mascolo I., Amendola A., Micheletti A., Luciano R., Fraternali F.

Micheletti A., Ruscica G., Amendola A., Mascolo I., Fraternali F.

Fang Y., Li J., Chen J.

Nugroho L., Haryanto Y., Hu H., Hsiao F., Pamudji G., Setiadji B.H., Hsu C., Weng P., Lin C.

Prestressed concrete structures, designed to enhance the compressive strength of concrete through internal pretension, are increasingly susceptible to serviceability issues caused by rising live loads, material degradation, and environmental impacts. Strengthening or retrofitting offers a practical and cost-effective alternative to full replacement. This study investigated the flexural strengthening of prestressed concrete T-beams in the negative moment region using near-surface mounted (NSM) carbon-fiber-reinforced polymer (CFRP) rods. Validation against experimental results from the literature demonstrated high accuracy, with an average numerical-to-experimental ultimate load ratio of 0.97 for reinforced concrete T-beams strengthened with NSM-CFRP rods, a negligible difference of 0.49% for prestressed concrete I-beams, and a minimal error of 1.30% for prestressed concrete slabs strengthened with CFRP laminates. Parametric studies examined the effects of CFRP rod embedment depths and initial prestressing levels. In certain cases, achieving the minimum embedment depth is not feasible due to design or construction constraints. The results showed that fully embedded CFRP rods increased the ultimate load by up to 14.02% for low prestressing levels and 16.36% for high levels, while half-embedded rods provided comparable improvements of 11.20% and 15.76%, respectively. These findings confirm the effectiveness of NSM-CFRP systems and highlight the potential of partial embedment as a practical solution in design-constrained scenarios.

Wu M., Zhu J., Huang X.

Due to the excellent bending resistance characteristics, open- and closed-section members are widely used in engineering practice. However, the interactions between plates of different sections have a significant effect on the mechanical behavior of members. Therefore, taking those interactions into consideration is a critical step in establishing the analytical model to investigate the static and dynamic behavior of the structures. This investigation proposes a spring plate model to analyze the vibration, static and dynamic buckling of members, in which the deformation of the spring plate is described by coupling polynomials and trigonometric series. The results show that this class of functions can accurately characterize the restraint of plates. The rotational restraint stiffness for single-plate and double-plates constraints are accurately obtained. Subsequently, analytical solutions for vibration and buckling problem are obtained by the Rayleigh–Ritz method. The dynamic buckling region of the members is further obtained using the Bolotin theory. When the frequency of the periodic load is in this region, the dynamic buckling of the structure is triggered. The presented model is provided to be an effective tool for analyzing the vibration and static and dynamic instability of thin-walled structures by comparing the existing results with finite element method (FEM) results. At the same time, understanding the vibration and dynamic behaviors is beneficial for design safely in terms of structural stability, load bearing capacity, and seismic resistance.

Sayed A.M., Ali N.M., Aljarbou M.H., Alzlfawi A., Aldhobaib S., Alanazi H., Altuwayjiri A.H.

Steel I-beams may be subject to deviation from their normal path towards the lateral direction due to obstacles along their axis line. This deviation in the lateral direction, i.e., the out-of-plane distance, affects the behavior of the steel beams and may reduce their ultimate capacity. To obtain this effect, finite element modeling (FEM) was used to model these beams with and without an out-of-plane distance at the mid-span beam length with several different variables. These variables were the out-of-plane distance, cross-section dimensions, beam length, and steel yield stress. The reliability of using FEM simulation was confirmed by comparing the experimental test results of 25 available steel beams in previous studies. The results indicate the high accuracy of the simulation of this beam in terms of ultimate capacity, structural behavior, and deformation patterns. After verifying the results, 116 broad-flange I-beam (BFIB) steel beams with different out-of-plane distances were modeled. The results showed that using an out-of-plane distance equal to the flange width of the BFIB-300 cross-section caused a 60% decrease in the ultimate capacity. The reduction ratios in the ultimate moment capacity in out-of-plane steel beams were directly proportional to the out-of-plane distance, cross-sectional dimensions, and steel yield stress, while the beam length had no effect. Failure in beams containing an out-of-plane distance occurs as a result of a global buckling in the upper flange, which contains tensile stresses at the outer edge and compressive stresses at the inner edge, with stress concentration occurring at the point of contact of the out-of-plane part with the main beam. The prediction results of the design codes were compared with the results of experimental tests and the FEM analysis of the beams with and without out-of-plane distances. For all the beams with out-of-plane distances, all the design codes were unable to predict this ultimate capacity.

Sarfarazi S., Shamass R., Guarracino F., Mascolo I., Modano M.

Stainless-steel provides substantial advantages for structural uses, though its upfront cost is notably high. Consequently, it’s vital to establish safe and economically viable design practices that enhance material utilization. Such development relies on a thorough understanding of the mechanical properties of structural components, particularly connections. This research advances the field by investigating the behavior of stainless-steel connections through the use of a four-parameter fitting technique and explainable artificial intelligence methods. Training was conducted on eight different machine learning algorithms, namely, Decision Tree, Random Forest, K-nearest neighbors, Gradient Boosting, Extreme Gradient Boosting, Light Gradient Boosting, Adaptive Boosting, and Categorical Boosting. SHapley Additive Explanations was applied to interpret model predictions, highlighting features like spacing between bolts in tension and end-plate height as highly impactful on the initial rotational stiffness and plastic moment resistance. Results showed that Extreme Gradient Boosting achieved a coefficient of determination score of 0.99 for initial stiffness and plastic moment resistance, while Gradient Boosting model had similar performance with maximum moment resistance and ultimate rotation. A user-friendly graphical user interface (GUI) was also developed, allowing engineers to input parameters and get rapid moment–rotation predictions. This framework offers a data-driven, interpretable alternative to conventional methods, supporting future design recommendations for stainless-steel beam-to-column connections.

Yazbeck R., El-Borgi S., Boyd J.G., Chen M., Lagoudas D.C.

Palakurthy S., Schemmel A., Zope A., Collins E., Bhushan S.

In this report, we investigate the onset of chaotic flutter in laminar and turbulent flows over a two-dimensional semi-infinite panel using time-accurate fluid–structure interaction (FSI) simulations of shock–boundary-layer interactions (SBLIs). Results indicate that the critical dynamic pressure and the nature of the panel dynamics strongly depend on the static pressure differential across the shock, the local loading, the viscous and turbulent damping in the flow, and the formation of dynamic flow separation bubbles due to the SBLIs. The structural system undergoes local instability (Hopf bifurcation) when the local loading due to panel deformation overcomes the static pressure differential across the shock. In the absence of external fluid instabilities, the structural oscillations will induce unsteadiness in the flowfield, resulting in low-frequency limit-cycle oscillations. Viscous and turbulent damping in the boundary layer also delays the bifurcation and reduces the amplitude of the oscillations. Sufficiently strong shocks can produce localized flow separations, which drive additional boundary-layer instabilities, resulting in an early bifurcation. In the presence of external fluid instabilities, the behavior of the FSI strongly depends on the nonlinear coupling of their instabilities. Chaotic oscillations are observed when the fluid instabilities are dominant enough to induce structural oscillations with broadband frequencies.

Sarfarazi S., Shamass R., Guarracino F., Mascolo I., Modano M.

Rezaei H., Zinatizadeh A.A., Joshaghani M., Zinadini S., Nazari S., Dolatshah M.

Xu C., You Z., Zhang C., Kang S.

Davey K., Xu J., Sadeghi H., Darvizeh R.

Fabbrocino F., Olivieri C., Luciano R., Vaiano G., Maddaloni G., Iannuzzo A.

Scozzese F., Tubaldi E., Dall’Asta A.

Gawali S.K., Jain P.K.

Recent studies have focused on developing new materials capable of withstanding diverse environmental or weathering conditions, including sunlight, temperature, moisture, and chemicals, for various outdoor applications. Nowadays, nanotechnological advancements have opened possibilities for the development of polymer nanocomposites, which exhibit superior mechanical and weathering properties over traditional materials. However, there is limited literature available that summarizes the improvements in the mechanical and weathering properties of nanocomposites specifically for FFF. This paper provides a concise review of composite material development through the incorporation of nanofillers (NFs) to enhance product strength and durability. The primary focus is on examining the effect of the inorganic nanofillers, especially metal oxides NFs (TiO2, ZnO, SiO2), on the mechanical and weathering properties of the polymers in different manufacturing processes. Paper also covered the challenges and opportunities along with the applications of metal oxide-based polymer nanocomposites for outdoor use.

Mascolo I., Guarracino F., Sarfarazi S., Della Corte G.

Sarfarazi S., Shamass R., Mascolo I., Della Corte G., Guarracino F.

Stainless-steel has proven to be a first-class material with unique mechanical properties for a variety of applications in the building and construction industry. High ductility, strain hardening, durability and aesthetic appeal are only a few of them. From a specific point of view, its nonlinear stress–strain behaviour appears capable of providing a significant increase in the rotational capacity of stainless-steel connections. This, in turn, may provide significant benefits for the overall response of a structure in terms of capacity and ductility. However, the bulk of the research on stainless-steel that has been published so far has mostly ignored the analysis of the deformation capabilities of the stainless-steel connections and has mostly focused on the structural response of individual members, such as beams or columns. For such a reason, the present study aims to contribute to the general understanding of the behaviour of stainless-steel connections from a conceptual, numerical and design standpoint. After a brief review of the available literature, the influence of the use of stainless-steel for column–beam connections is discussed from a theoretical standpoint. As a novel contribution, a different approach to compute the pseudo-plastic moment resistance that takes into account the post-elastic secant stiffness of the stainless-steel is proposed. Successively, a refined finite element model is employed to study the failure of stainless-steel column–beam connections. Finally, a critical assessment of the employment of carbon-steel-based design guidelines for stainless-steel connections provided by the Eurocode 3 design (EN 1993-1-8) is performed. The findings prove the need for the development of novel design approaches and more precise capacity models capable of capturing the actual stainless-steel joint response and their impact on the overall ductility and capacity of the whole structure.

Xu B., Xia J., Ma R., Chang H., Yang C., Zhang L.

It is well-known that interfacial slippage is a critical factor for the cooperation of laminated beams in modular steel buildings. However, the slipping behavior of laminated steel channel beams with bolt connections has not been fully understood. In the present study, a series of bending tests using the digital image correlation (DIC) optical measuring method, finite element (FE) parametric study, and theoretical derivation were conducted to investigate the interfacial slip response of laminated channel beams comprehensively. The results showed that the increase in bolt connection number significantly constrained the slipping behavior, while the effect of layer height ratio was comparatively not obvious. Moreover, the nonlinear improvement of anti-slip behavior by adding interfacial bolt connections was observed, which suggested that the appropriate bolt number should be adopted in engineering practice for optimal efficiency. The analytical models provided a reliable assessment for the interfacial slippage, and laid a foundation for further theoretical study on the cooperative bending behavior of laminated channel beams. • Laminated beams with varying bolt numbers showed different load-slip mechanisms. • The appropriate bolt number should be adopted for optimal engineering efficiency. • The analytical procedure gave good prediction of slip regarding design parameters.

Mascolo I., Guarracino F.

Elastic buckling of circular rings under external pressure is one of the oldest and most ubiquitous problems in structural engineering and the first meaningful solution to it was proposed by Levy (1884). This basic solution, based on the Euler–Bernoulli beam model, can be found in the vast majority of textbooks on stability. However, there are a number of subtleties in the formulation of the problem which need to be taken into account so and one should always be well aware of the underlying analytical fundamentals, especially in the current world which strongly relies on numerical analyses. Therefore, starting from the general nonlinear kinematics of the problem, the buckling load is revisited by means of a direct energy approach and on the basis of an in-depth discussion of the classic kinematic hypotheses. Possibly different outcomes are pointed out and remarked. Finally, some inconsistencies which unexpectedly arise in pursuing the solution by means of commercial FE packages are presented and commented. • Elastic buckling of circular rings under different types of pressure is analysed and reviewed. • Discrepancies between theoretical and numerical results are discussed. • The possible drawbacks of using FE codes without making reference to fundamental solutions are pointed out.

González-de-León I., Nastri E., Arrayago I., Montuori R., Piluso V., Real E.

Stainless steel is an excellent construction material due to its high ductility, strain hardening, durability and aesthetic characteristics. To date, most studies on stainless steel have been devoted to understanding its mechanical properties and the behaviour of individual structural members and simple structures under monotonic loading. As a result, next versions of stainless steel codes, traditionally based on carbon steel codes, will enable efficient structural designs under static forces. However, advances related to the performance of stainless steel structural members under cyclic forces are still scarce, and there are no specific rules for the seismic design of stainless steel structures in Eurocode 8 in spite of the notable differences between this material and other steels. On this basis, an experimental programme on austenitic stainless steel hollow section elements subjected to cyclic loading has been recently conducted. A total of nine specimens with different local and member slenderness values were tested under cyclic bending around their major axis following a cantilever loading scheme. This paper describes the experimental set-up adopted for the tests, including the loading scheme and instrumentation, and discusses the load–displacement, moment–rotation, degradation of stiffness and energy dissipation values obtained in detail. In addition to providing fundamental information on the response of stainless steel members under cyclic loading, the description of the set-up reported in this paper will assist researchers in planning similar experimental programmes, while the results will serve as a reference to validate numerical analyses of stainless steel members and frames subjected to cyclic loading. • Austenitic stainless steel hollow section members are tested under cyclic bending. • Specimens with different local and member slenderness values are covered. • The adopted experimental set-up and loading protocol are defined. • The resulting load–displacement and moment–rotation responses are provided. • The stiffness degradations and energy dissipation capabilities are discussed.

Piluso V., Pisapia A., Rizzano G.

The aim of the work is the evaluation of the ultimate behaviour of aluminium channel sections subjected to local buckling under uniform compression. In particular, two different approaches are presented to predict the inelastic response of aluminium members: the Deformation Theory of Plasticity (DTP) and the Effective Thickness Method (ETM). The first one represents a theoretical procedure applied according to elastic–plastic stability theory of a single plate and considering restraining effects of adjacent plate elements. The Effective Thickness Method (ETM) is a simplified approach currently adopted by Eurocode 9 to estimate the ultimate resistance of aluminium sections taking into account the local buckling effects. In this paper, an extension of this approach is provided by introducing the mechanical non-linearity of material and the influence of section plates constraints. Finally, the accuracy of these procedures is demonstrated by comparing the ultimate compressive resistance derived by theoretical approaches with the values of the ultimate loads provided by the stub column tests performed at the University of Salerno. • Theoretical procedure to predict the ultimate resistance of aluminium channel sections in compression. • Application of the effective thickness method currently adopted by Eurocode 9. • Derivation of plastic coefficients according to deformation theory of plasticity. • Comparison between the experimental results with those obtained DTP and ETM approaches.

Sarfarazi S., Shamass R., Della Corte G., Guarracino F.

Considering the significant strain-hardening and ductility characteristics of stainless steel and the influential role of beam to column joints in the overall response of structures, a clear understanding of their moment rotation behaviour appears fundamental. In the present study, a review of the European design code for three typical semi-continuous beam-to-column joints (extended end plate, flush end plate and top-and-seat angle connections) is first carried out. Then, using a hybrid modelling strategy with uncoupled elastic-plastic springs for the bolts and shell elements for the members, more refined 3D finite element (FE) models are developed and validated against available test results. An equivalent stress definition is then proposed for calculating the joint moment resistance. Finally, the initial rotational stiffness, moment resistance, rotation capacity, and failure patterns are used to evaluate critically the accuracy of the predictions of the European design code. As a result, the need for more comprehensive design guidance in accordance with the observed findings is pointed out.

Wang Z., Ming D., Wang Y., Qiu C., Tan M.

Micro-ring resonator (MRR) is a key photonic device that has a wide range of applications but suffers from wavelength uncertainties. For almost all practical applications, a wavelength controller is required for each MRR. The wavelength controller is usually much larger than the MRR. With more complicated control algorithms, the controller size becomes even larger. Equipping each MRR with a wavelength controller will not be scalable. We propose a pipelined time-division-multiplexing (PTDM) control scheme that achieves high scalability while maintaining good loop bandwidth by exploiting the speed mismatch between the heater and the controller. To verify this proposed scheme, a hybrid integrated controller supporting four MRRs is designed. Measurement results show that it achieves a sine tracking speed of about 15 nm/s while achieving a locking accuracy of 7 pm and a tuning range of 9 nm.

González-de-León I., Arrayago I., Real E., Nastri E.

Stainless steel is a structural material with great potential in seismic design due to its ductile and strain hardening characteristics. However, no specific seismic design provisions exist for stainless steel, despite the remarkable differences with carbon steel. Moreover, research on the behaviour of stainless steel under cyclic conditions is scarce, not allowing designers to rely on accurate capacity models able to catch the actual member ductility under seismic excitation. Hence, the aim of this paper is to fill this lack and to provide simple provisions to estimate the total and stable part of the rotation capacity of stainless steel members with rectangular hollow section (RHS). A numerical study on 120 austenitic, ferritic and duplex beams under cyclic loading was performed following the ANSI/AISC 341 loading protocol. From the resulting skeleton curves, information on the ultimate strength and ductility (total and stable parts of the rotation capacity) were extracted. It was found that the ultimate bending moment resistance of RHS stainless steel beams under cyclic loading is accurately predicted by the Continuous Strength Method moment capacity, and that the rotation capacities can be related to the local slenderness by power functions calibrated from the numerical results. Finally, a tri-linear model that describes the full moment-rotation curves of stainless steel beams under cyclic loading is proposed using the calibrated equations, showing a good agreement with numerical moment-rotation curves, and which can be implemented in design software to define the behaviour of concentrated plasticity hinges. • Stainless steel hollow section beams under cyclic loading are studied numerically. • Austenitic, ferritic and duplex stainless steel alloys are covered. • Ultimate bending moment and plastic rotation values under cyclic loading are identified. • Expressions predicting plastic rotation capacities under cyclic loading are proposed. • A tri-linear model describing the full moment-rotation curves is proposed and assessed.

Olivieri C., Cennamo C., Cusano C., Cutolo A., Fortunato A., Mascolo I.

The present paper applies the Linear Arch Static Analysis (LASA), which models the masonry material as unilateral, i.e., No-Tension material in the sense of Heyman, and the Safe Theorem of the Limit Analysis to the study of masonry spiral stairs. A comparison is made with a refined FE analysis of the same problem, obtained by means of the ANSYS Parametric Design Language (APDL). The objective is to prove that LASA can be a valid alternative to other more complex numerical methods, such as FE, especially when the modeling parameters, such as the boundary conditions, cannot be exactly defined. The case study of a small spiral staircase placed in the tower of Nisida, a small island close to Naples, Italy is taken into consideration. The results show that the LASA analysis provides results that fall within two limit FE cases in terms of stress and overall thrust, providing at the same time a meaningful insight into the equilibrium state of the structure.

Rabi M., Shamass R., Cashell K.A.

Nowak R., Kania T., Rutkowski R., Ekiert E.

The study presents the terrestrial laser scanning (TLS) diagnostic of the clay brick masonry arched staircase in a historic building. Based on the measurements of the existing arched stair flights, 1:1 scale experimental models with and without stair treads were made. Strength tests of the models were carried out for different concentrated force locations in relation to the supporting structure. Force, deflections and reaction in the upper support of the run were measured during the tests. The influence of the masonry steps on the curved vault on the load capacity and stiffness of the run structure was analyzed. The conducted experimental investigations showed that the key element responsible for the actual load-bearing capacity and stiffness of this type of stair flights were the treads above the masonry arch.

Fortunato A., Gesualdo A., Mascolo I., Monaco M.

Yan S., Rasmussen K.J.

The design-by-analysis approach lays the foundation for the next generation of structural design standards in which the strength and structural safety check are performed in a single step at system level, without recourse to a structural standard for individual member checks. However, to date, no attempt has been made towards considering the failure of joints in the structural analysis, without which the complete set of limit states cannot be accurately predicted. This paper presents a new analysis approach that incorporates macro-element joint models based on the Generalised Component Method in the FE analysis of steel frame buildings. The new analysis approach is termed Generalised Component Method-based finite-element (GCM-FE) analysis. The fundamental aspects and principles of the GCM-FE analysis approach are established in this paper, including the framework of GCM-FE analysis, the constitutive models for the connection components and the implementation of GCM-FE analysis in commercial numerical software including an automatic modelling technique. The GCM-FE joint modelling method is first validated against the experimental results of three steel beam-to-column connection types, including the bolted moment end-plate connection, top-and-seat angle connection and web angle connection. GCM-FE analysis is subsequently performed on a two-storey four-bay irregular steel frame, showing apparent advantages over the traditional analysis methods which adopt simplified joint models. The GCM-FE analysis not only provides the ultimate resistance and failure mode of the frame, but also accurately predicts the load-redistribution process inside the connections and the resultant effect on the structural framework. • Generalised Component Method is incorporated in the finite-element analysis. • The framework and implementation method of GCM-FE analysis is established. • GCM-FE analysis predicts the ultimate resistance and all failure modes of the frame. • Failure process inside connections and resultant effect on the frame are predicted.

Ali L., Khan S., Iqbal N., Bashmal S., Hameed H., Bai Y.

Many methods have been used in the past two decades to detect crack damage in steel joints of the offshore structures, but the electromechanical impedance (EMI) method is a comparatively recent non-destructive method that can be used for quality monitoring of the weld in structural steel joints. The EMI method ensures the direct assessment, analysis and particularly the recognition of structural dynamics by acquiring its EM admittance signatures. This research paper first briefly introduces the theoretical background of the EMI method, followed by carrying out the experimental work in which damage in the form of a crack is simulated by using an impedance analyser at different distances. The EMI technique is used to identify the existence of damage in the welded steel joints of offshore steel jacket structures, and Q345B steel was chosen as the material for test in the present study. Sub-millimetre cracks were found in four typical welded steel joints on the jacket platform under circulating loads, and root average variance was used to assess the extent of the crack damage.

Liang G., Huang H., Mohanty A., Shin M.C., Ji X., Carter M.J., Shrestha S., Lipson M., Yu N.

Optical phase modulators are essential to large-scale integrated photonic systems at visible wavelengths and are promising for many emerging applications. However, current technologies require large device footprints and either high power consumption or high drive voltages, limiting the number of active elements in a visible-spectrum integrated photonic circuit. Here, we demonstrate visible-spectrum silicon nitride thermo-optic phase modulators based on adiabatic micro-ring resonators that offer at least a one-order-of-magnitude reduction in both the device footprint and power consumption compared with waveguide phase modulators. Designed to operate in the strongly over-coupled regime, the micro-resonators provide 1.6π phase modulation with minimal amplitude variations, corresponding to modulation losses as small as 0.61 dB. By delocalizing the resonant mode, the adiabatic micro-rings exhibit improved robustness against fabrication variations: compared with regular micro-rings, less than one-third of the power is needed to thermo-optically align the resonances of the adiabatic micro-rings across the chip to the laser frequency. Visible-spectrum silicon nitride thermo-optic phase modulators based on adiabatic micro-ring resonators with a small device footprint and low power consumption, of potential use for applications like augmented-/virtual-reality goggles, quantum information processing circuits and optogenetics, are presented.