Frame Configuration Research Articles

Experimental research on the axial compressive performance of brick masonry walls strengthened with a steel plate frame considering initial load

Initial load means the load, including dead or/and live load, applied on brick masonry walls before being strengthened, which can influence the strengthening effect. However, research on the strengthening of brick masonry walls particularly considering the effect of initial load is insufficient. Steel is widely utilised for brick masonry strengthening because of its simple construction procedure and flexible configuration. Hence, for advancing the application of steel plates in brick masonry strengthening engineering and studying the effect of initial load on strengthening, an experiment was performed to investigate the axial compressive performance of a steel plate frame (SPF) strengthening brick masonry wall considering initial load for various frame configurations. The experiment results indicated that the SPF effectively confined the brick masonry wall, and steel plate columns underwent local buckling failure under axial load; the load-bearing capacity of brick masonry walls increased by at least 10.62 % strengthened with double-sided single-span SPF, and it further improved by 18.75 % strengthened with double-sided double-span SPF when initial load ratio was less than 0.25. Initial load ratio considerably affected the axial collaborative performance of the brick masonry wall and SPF, and increasing initial load ratio resulted in poor axial collaborative performance, following which the load-bearing capacity of the strengthened masonry walls decreased. The load-bearing capacity of the strengthened walls was higher for an initial load ratio less than 0.25. Conversely, a rare strengthening effect was observed when the initial load ratio exceeded 0.7. Based on the simplification of steel plate boundary conditions and the buckling theory of struts, a formula for predicting the load-bearing capacity of brick masonry walls strengthened with an SPF considering initial load was derived, which showed acceptable accuracy in comparison with experimental values.

An unusual new ophiuroid (Echinodermata) from the Late Ordovician (early Katian) of Morocco

A distinctive new genus and species of the subphylum Asterozoa, Componaster spurius n. gen., n. sp., is described from the Late Ordovician (early Katian) of Morocco. Construction of the ambulacral column is considered key to delineation of classes of the subphylum Asterozoa: morphology and configuration of the mouth frame, axial (ambulacral series), and adaxial (lateral series) enable class-level assignment of C. spurius n. gen., n. sp. to the Ophiuroidea Gray, 1840. However, overall form and aspects of extraxial skeletal expression from beyond the ambulacral column are strongly reminiscent of expressions of the Asteroidea de Blainville, 1830. The character complex of C. spurius n. gen., n. sp. precludes its alignment with any available ophiuran ordinal concept, and available data do not justify proposal of new ordinal terminology: the species is left incertae sedis at the ordinal level but a new familial taxon, Componasteridae n. fam., is recognized. Although Late Ordovician, the complex morphology of Componaster spurius n. gen., n. sp. suggests either plesiomorphic expressions from asterozoan diversification surviving until the Katian or significant homoplasy during early ­asterozoan history.

Machine learning-based residual drift prediction of concrete-filled steel tube columns under earthquake loads

This study introduces a machine learning (ML) model for predicting the residual (permanent) drift in concrete-filled steel tube (CFT) structures exposed to excessive loads. The relationship between the residual drift and design parameters of the CFT column was established through the adaptation of six distinct ML models. The accuracy of the proposed model was evaluated by comparing its predictions with the results derived from existing numerical models and code provisions. The proposed ML model surpasses existing residual drift prediction models by at least 4% in terms of R-squared value. To evaluate the effectiveness of the model, a nonlinear dynamic analysis of a three-story, three-bay CFT moment-resisting frame subjected to 44 ground motions was conducted using a numerical model. Additionally, two modified frame models were considered to investigate the influence of frame configuration on the performance of the ML model. Subsequently, the residual inter-story drift ratio derived from the seismic analysis using the numerical model was compared with the results obtained from the ML predictive model and code provisions. The proposed ML model exhibited greater accuracy in predicting the residual inter-story drift ratio than the code provisions when applied to the results of numerical analyses performed for weak-column strong-beam frames. The ML model showed a positive R-squared value, whereas the code provisions yielded a lower R-squared value. In turn, the ML model applied to the strong-column weak-beam moment-resisting frames tended to overestimate the residual inter-story drift ratio, with a ratio of the predicted value to the value obtained from the analysis equal to 3.5.

Reserve capacity and vertical extension potential in steel framed buildings

Reusing existing buildings is key in transitioning to a circular economy and meeting associated decarbonisation targets. Many adaptive reuse strategies, including vertical extensions, result in increased loads that are required to be resisted by reserve structural capacity and/or strengthening. Previous work identifies structural underutilisation within existing buildings and suggests numerous sources of this. However, understanding of associated contributions to reserve capacity and how this influences a building’s ability to be extended is limited. To address this, 11 scenarios, each modelling a different source of underutilisation, have been developed and applied in the design and reappraisal of 11,252 hypothetical steel framed office buildings. An average reserve capacity of 10% is found in optimal Eurocode designs, rising to around 20% for British Standards and over 30% in the conservative or defensive application of Eurocodes. Office to residential conversions are shown to unlock an average reserve capacity of more than 20%. Across the 11 scenarios, between 9% and 89% of considered cases are shown to be extendable without the need for strengthening. This demonstrates potentially significant extension potential within steel framed buildings, but that this varies with frame configuration, design/appraisal approach, and the extension’s use and structural material.

Experimental investigation of long-span cold-rolled aluminium built-up section portal frames: Braced columns and ultimate strength enhancement

This paper presents an experimental program on a series of long-span cold-rolled aluminium portal frames with various configurations subjected to different load combinations. The main structural members of the portal frame systems, including columns and rafters, were constructed using cold-rolled aluminium back-to-back built-up channel sections made from aluminium alloy 5052-H36 materials. The objectives of this paper are to understand the structural behaviour of different portal frame configurations and to explore possibilities for improving the performance of the structural systems, including strength and ductility enhancements. A total of four full-scale two-bay portal frame systems, each featuring two end frames and a central frame, were tested. The columns were braced against flexural-torsional buckling by girts spanning between the columns of the central frame and the columns of the two end frames. As a result, the portal frames failed due to in-plane sway deformations with the columns reaching their full section capacities. The tests revealed that the addition of rafter tie and sleeve stiffeners significantly improved the performance of the cold-rolled aluminium portal frame systems. Described in a separate publication, the authors also conducted a study to experimentally investigate the behaviour of the same system but with unrestrained columns, resulting in failure due to flexural-torsional buckling. Collectively, these two works form the foundation for further studies on cold-rolled aluminium portal frames in particular, and aluminium structures more generally.

A consistent approach to the definition of initial geometric imperfections for in-plane stability design of steel moment frames

Geometric imperfections can have a significant influence on the behaviour and ultimate resistance of steel structures. For the purposes of structural design, particularly design by geometrically and materially nonlinear analysis with imperfections (GMNIA), a suitable choice of imperfections, in terms of both amplitude and shape, is therefore required; an inappropriate choice of imperfections can lead to misleading results and unsafe resistance predictions. The development of a practical strategy for defining imperfection shapes in the in-plane GMNIA-based design of steel moment frames is the focus of the present study. The proposals are also suitable for GNIA-based design. Both overall sway imperfections (i.e. frame out-of-plumbness) and individual member bow imperfections, together with combinations thereof (i.e. sway-member imperfection combinations), are considered. Several methods for introducing imperfections are assessed. Each method is categorised depending upon whether the imperfection is established through: (1) direct definition or (2) the scaling of eigenmodes. The recommended direct definition-based method introduces a sway imperfection in sympathy with the applied lateral loading and member imperfections with alternating directions between storeys, as dictated by the column base boundary conditions. The recommended eigenmode-based method uses the first sway mode and determines the number of non-sway modes according to the eigenvalues under the design loading, with all non-sway modes for which the eigenvalues αcr,ns < 25 also contributing to the imperfection. The eigenmodes are scaled to ensure the bounds of the prescribed imperfection amplitudes are suitably maintained. The consistency and accuracy of the proposed methods are demonstrated for 21 different frame configurations.

Quadcopter Unmanned Aerial Vehicle Structural Design Using an Integrated Approach of Topology Optimization and Additive Manufacturing

The performance of quadcopter frames, particularly in terms of weight and crash resistance, is significantly influenced by their structural design and manufacturing process. In this work, a methodology is proposed that integrates advanced principles of topology optimization (TO) and additive manufacturing (AM) techniques to optimize the frame structure for improved performance. First, an analysis is conducted to evaluate existing quadcopter frame configurations, identifying areas for improvement. Experimental evaluations of thrust and moment of motors are performed to assess the performance of the enhanced quadcopter frame, with a focus on advancing the design through computer-aided simulations of static structural analysis and impact tests. The TO technique is then employed to determine the optimal distribution of material within the frame, governed by constraints such as weight reduction and mechanical strength. The results demonstrate that the overall performance of a quadcopter frame is significantly improved by the proposed methodology, showcasing advancements in stability, weight reduction, and crashworthiness. The resulting optimized frame design is subsequently manufactured using AM methods, which offer advantages such as design flexibility and the ability to produce complex geometries. The findings of this study contribute to the field of quadcopter design and optimization by highlighting the synergies between TO and AM techniques. An avenue is offered for the development of lightweight and robust quadcopter frames, as the capabilities and performance of quadcopter systems are advanced. The insights gained from this research open up opportunities for further advancements in the design and manufacturing of UAVs.

Different shades of green: how transnational actors frame nature as a solution to sustainability challenges in African cities

ABSTRACT Nature – based solutions (NBS) are increasingly being positioned within global discourses concerning how urban sustainability challenges can be addressed. To better understand to what extent, how, by whom and with what potential implications NBS are promoted in urban Africa, this paper focuses on transnational actors and presents a dataset covering 40 NBS initiatives in 57 cities across 19 African countries. A framing analysis is undertaken to understand to what degree NBS are mobilised in accordance with global discourses. To that end, the paper builds on existing work by Tozer et al. (2022, “Transnational Governance and the Urban Politics of Nature-Based Solutions for Climate Change.” Global Environmental Politics, 1–23) on globally circulating frames of urban nature. In further contributing to their framework, we delve into the underlying values or shades of green that are being signified through the frames by applying the IPBES Nature Futures Framework. Results indicate that urban nature comes to be seen as a solution within a climate resilience – integrated benefits nexus through which various types of transnational actors are bringing nature into the city. Two important findings can be highlighted: First, the deployed frames offer opportunities to address major African urban sustainability challenges, but initiatives may not yet be configured to adequately address their scope and magnitude. Second, the configurations of frames are predominantly informed by instrumental values that put "Nature for Society” perspectives in focus, missing opportunities for NBS to build on relational values, or “Nature as Culture” perspectives and for accommodating a plurality of worldviews on desirable futures for urban nature.

Transform coefficient distribution modeling based frame-level adaptive rate control for VVC

Rate control is a key issue in the research of video coding optimization. In this work, we propose a statistical modeling based frame-level distortion estimation model and a distortion dependency based rate control optimization algorithm for Versatile Video Coding (VVC). VVC has incorporated into more advanced coding tools, resulting in the distribution of transform coefficient more sharper. In response to this phenomenon, the TCD of VVC is modeled by the probability density function (PDF) of Cauchy distribution and generalized Gaussian distribution (GGD) individually. Then, a sliding window-based frame-level distortion model is proposed, which is used for derivation of inter-frame distortion dependency factor. According to the derived distortion dependency factor, a frame-level rate control optimization algorithm is presented to update the coding parameters in practical coding process. Experiments have shown that the proposed method could effectively improve rate–distortion performance, achieving an average rate distortion performance improvement of 0.72% in sequences blow 4K resolution, and 1.47% in 4K sequences in low delay P frame (LDP) configuration.

THE BIGGER, THE BETTER? TWO-RING CIRCULAR FRAMES AND DURATION OF TREATMENT IN THE MANAGEMENT OF TIBIAL FRACTURES: A RETROSPECTIVE COHORT STUDY

IntroductionFrame configuration for the management of complex tibial fractures is highly variable and is dependent not only on fracture pattern and soft tissue condition but also surgeon preference. The optimal number of rings to use when designing a frame remains uncertain. Traditionally, larger, stiffer constructs with multiple rings per segment were thought to offer optimal conditions for bone healing, however, the concept of reverse dynamisation questions this approach.Materials &amp; MethodsWe compared clinical outcomes in 302 consecutive patients with tibial fractures treated in our unit with either a two-ring circular frame or a three-or-more-ring (3+) frame. The primary outcome measure was time spent in frame. Secondary outcomes were the incidence of malunion and the need for further surgical procedures to achieve bone union. The groups were evenly matched for age, co-morbidities, energy of injury mechanism, fracture classification, post-treatment alignment and presence of an open fracture.ResultsThe mean time in frame was 168 days for the 2-ring group and 200 days for the 3+ rings group (p=0.003). No significant difference was found in the rate of malunion (p=0.428) or the requirement for secondary surgical intervention to achieve union (p=0.363). No significant difference in time in frame was found between individual surgeons.ConclusionsThis study finds that 2-ring frame constructs are a reliable option associated with significantly shorter duration of treatment and no increase in rates of adverse outcomes compared with larger, more complex frame configurations. Although this study cannot identify the underlying cause of the difference in treatment time between frame designs, it is possible that differences in mechanical stability lead to a more favourable strain environment for fracture healing in the 2-ring group.

Progressive Collapse of Typical and Atypical Reinforced Concrete Framed Buildings

This paper investigates the progressive collapse potential of eight-story reinforced concrete framed buildings with several atypical structural configurations and compares results with a typical structural configuration. The alternative load path mechanism, the linear-static analysis procedure amplified by dynamic increase factors, and the demand capacity ratio criterion limits from the U.S. General Services Administration guideline were used to evaluate the vulnerability of the different atypical and typical framed structures. Variations in bay size, plan irregularity, and closely spaced columns were used to represent the atypical structural configurations. The extracted demand-capacity ratio (DCR) of the global structural response showed that the demand-capacity ratio for the longitudinal frame with short-span beams had a larger DCR than the transverse frame with longer beam spans with significant potential for progressive collapse. Furthermore, atypical building configurations with closely spaced columns failed by shear and showed the highest DCR limits. In addition to the global structural response, the local member end actions were also evaluated. The evaluation showed that the critical atypical frame configuration with closely spaced columns had a 91% and 127% maximum shear force and support bending moment value difference, respectively, when compared to a baseline typical frame configuration.

Seismic Resilience of Steel-Braced Frames Incorporating Steel Slit Dampers: A Review and Comparative Numerical Analysis

Steel dampers, specifically steel slit dampers (SSDs), are crucial for enhancing the seismic resilience of buildings by absorbing energy and mitigating damage. SSDs are celebrated for their ability to produce stable hysteretic behavior, owing to the inelastic deformation of their strips, alongside benefits such as lightness, ease of manufacture, and straightforward post-earthquake replacement. This research extensively examines SSD applications, design principles, and innovations in their modeling, optimization, and production processes. The literature highlights SSDs' consistent performance in resisting both compression and tension, their adaptability in strength, ductility, and energy dissipation through modifications in strip configurations and the superiority of non-prismatic and hourglass-shaped designs over traditional options. Numerical analyses have been conducted to assess the effectiveness of non-prismatic slit dampers in comparison to their prismatic counterparts within braced frames. Three distinct braced frame configurations have been analyzed: one with a diagonal brace without a damper, another featuring a uniform prismatic slit damper, and a third incorporating a non-prismatic slit damper with an hourglass shape. The analysis primarily compared these systems' hysteresis behavior, ductility, and energy dissipation capacities. Results indicate a significant enhancement in performance when utilizing non-prismatic slit dampers. Notably, these dampers exhibited a remarkable 69% increase in cumulative energy dissipation compared to prismatic ones. Furthermore, the study reveals that a steel slit damper-braced frame, when equipped with optimally designed slit geometries, can tolerate inter-story drifts in excess of 2% while simultaneously achieving a greater than 12% increase in energy dissipation efficiency. Doi: 10.28991/CEJ-2024-010-04-019 Full Text: PDF

A clinical 3D pointing test differentiates spatial memory deficits in dementia and bilateral vestibular failure

BackgroundDeficits in spatial memory, orientation, and navigation are often neglected early signs of cognitive impairment or loss of vestibular function. Real-world navigation tests require complex setups. In contrast, simple pointing at targets in a three-dimensional environment is a basic sensorimotor ability which provides an alternative measure of spatial orientation and memory at bedside. The aim of this study was to test the reliability of a previously established 3D-Real-World Pointing Test (3D-RWPT) in patients with cognitive impairment due to different neurodegenerative disorders, bilateral vestibulopathy, or a combination of both compared to healthy participants.MethodsThe 3D-RWPT was performed using a static array of targets in front of the seated participant before and, as a transformation task, after a 90-degree body rotation around the yaw-axis. Three groups of patients were enrolled: (1) chronic bilateral vestibulopathy (BVP) with normal cognition (n = 32), (2) cognitive impairment with normal vestibular function (n = 28), and (3) combined BVP and cognitive impairment (n = 9). The control group consisted of age-matched participants (HP) without cognitive and vestibular deficits (n = 67). Analyses focused on paradigm-specific mean angular deviation of pointing in the azimuth (horizontal) and polar (vertical) spatial planes, of the preferred pointing strategy (egocentric or allocentric), and the resulting shape configuration of the pointing array relative to the stimulus array. Statistical analysis was performed using age-corrected ANCOVA-testing with Bonferroni correction and correlation analysis using Spearman’s rho.ResultsPatients with cognitive impairment employed more egocentric pointing strategies while patients with BVP but normal cognition and HP used more world-based solutions (pBonf 5.78 × 10-3**). Differences in pointing accuracy were only found in the azimuth plane, unveiling unique patterns where patients with cognitive impairment showed decreased accuracy in the transformation tasks of the 3D-RWPT (pBonf < 0.001***) while patients with BVP struggled in the post-rotation tasks (pBonf < 0.001***). Overall azimuth pointing performance was still adequate in some patients with BVP but significantly decreased when combined with a cognitive deficit.ConclusionThe 3D-RWPT provides a simple and fast measure of spatial orientation and memory. Cognitive impairment often led to a shift from world-based allocentric pointing strategy to an egocentric performance with less azimuth accuracy compared to age-matched controls. This supports the view that cognitive deficits hinder the mental buildup of the stimulus pattern represented as a geometrical form. Vestibular hypofunction negatively affected spatial memory and pointing performance in the azimuth plane. The most severe spatial impairments (angular deviation, figure frame configuration) were found in patients with combined cognitive and vestibular deficits.

Staged treatment of bicondylar tibial plateau fractures: influence of frame configuration and quality of reduction on outcomes.

Despite evolving treatment, the surgical management of high-energy tibial plateau fractures (TPF) remains challenging, associating high rates of complications. In recent decades, staged management has emerged as an encouraging option. The main goal of our study was to evaluate the influence of bridging external fixation (EF) frame configuration and the resultant quality of reduction (QOR) on outcomes after staged-treatment of bicondylar TPF. A retrospective review was conducted of patients with bicondylar TPF treated at our level-I trauma center using a staged-treatment protocol from January 2010 to January 2020. Data on baseline characteristics, injuries, treatments, and clinical/radiological results were collected. The QOR was evaluated on CT images after EF and on plain films after ORIF. Sixty-eight patients were eligible for analysis. By our criteria, QOR was good in 57.4% and 70.6% after EF and ORIF, respectively. A squared EF configuration was associated with superior EF QOR (p = 0.032), while better EF QOR was linked to improved ORIF QOR (p = 0.016). No relationship between ORIF delay and ORIF QOR was identified. Postoperative complications were documented in 19 patients. Average ROM at one-year follow-up was 114.9 ± 12.6°, and non-influenced by anterior femoral pin placement. Staged management of bicondylar TPF resulted in a reasonable rate of complications. A direct relationship between QORs obtained with EF and after ORIF was found. Squared frames were associated with faster and better reductions, regardless of the surgeon's background. Considering our results, we advocate for the wider use of squared EF configurations in these patients.

Impact of Inclination of Girders and Columns on the Effort and Stability of Flat Bar Frames.

The article describes a specific method of using innovative transverse systems of flat bar frames as structures forcing elastic shape transformations of nominally flat folded sheets into the forms of ruled shell roof coverings. An innovative method for parametric shaping these forms and arrangement of frames constituting structural systems of sheds with folded thin-walled roof coverings, taking account of the specificity of designing elastically transformed roof sheeting, was proposed. The proposed method for defining the loads of the considered frames supporting lower shelves of the folds of transformed roof sheeting, as loads distributed uniformly along the length of the upper chord of a roof frame girder, is also an innovative approach. The above unconventional premises result in the innovative topic of the research presented in terms of checking the impact of changing the shape of subsequent flat frames (intended for the construction of sheds roofed with the transformed sheeting) on the geometric and mechanical properties of the members of these frames. For the defined loads and the proposed parameterization of the frame forms, an innovative set of conditions was developed to optimize their performance, and then a theoretical analysis of the observed dependencies was carried out. This analysis was performed in an unconventional, novel way using section modules of the cross-sections of all members. The performed computer simulations confirmed the significance of changes in the inclination of girders and columns on the geometric and mechanical properties of the members. The obtained results are the basis and justification for simulations and tests in the scope of further modification of the form, loads, work, and methods of using various configurations of flat frames in constructions.

Design of ultra-lightweight and energy-efficient civil structures through shape morphing

This paper gives a new formulation to synthesize load-responsive structures through shape morphing. The design method is based on the minimization of the whole-life energy, which comprises an embodied share in the material and an operational share for adaptation. Target shapes that counteract the effect of the design loads are obtained through geometry and sizing optimization. Adaptation through shape morphing enables effective stress redistribution so that the design is not dominated by peak loads with long return periods. Material utilization is maximized, and therefore embodied energy is significantly reduced. The geometry is controlled through length changes of optimally-placed linear actuators. The actuator commands are computed through minimization of the operational energy to satisfy safety and serviceability criteria. Minimum energy solutions are obtained through a univariate optimization process in which embodied and operational energy minimization are nested. Numerical benchmarks between adaptive and mass-optimized passive solutions are provided on a truss bridge and multi-story frame configurations. Parametric studies show that mass and energy savings are significant for slender structures and when the live load is dominant over the permanent load. Generally, larger shape bounds result in a greater reduction of mass and embodied energy at the cost of a larger operational energy.

Measurement of Geometric Variations of a Railway Truss Bridge (Case Study: BH77 Railway Bridge)

Monitoring the condition of the railway track on a regular basis needs to be carried out regularly to minimize risk. One of the causes of the decrease in the strength of the bridge structure can be caused by changes in cross-sectional dimensions. The existing dimensions of the bridge structure need to be known because they will affect the steel frame profile area, where the steel frame area will affect the size or the small value of the deflection and stress of the bridge structure. The dimensions of the frame need to be seriously considered so that the stress and deflection values ??of the bridge structure remain constant. This research was conducted at the BH 77 Railway Bridge in Tegineneng, Tanjungkarang-Martapura, Lampung, which uses a type frame configuration warren truss. This location was chosen to fit the research that was also conducted by Badan Riset dan Inovasi Nasional (National Research and Innovation Agency of Indonesia). Based on the measurement of the dimensions of the bridge truss that has been carried out, the results show that there is a difference in the value of the circumference of each rod with the standard deviation for each similar profile. The biggest difference in the circumference of the truss is the profile of H beam, 113 and 115 rods with dimensions of 340×300×15×18, the initial circumference value is 1,280 mm, and after the measurement is 1,289.42 mm with a standard deviation value of 0.91 mm. while for the smallest difference, namely the H beam profile, rod 110 with dimensions of 340×310×39×21, the initial circumference value is 1,300 mm and after the measurement is 1,300.33 mm with a standard deviation value of 0.24 mm.

Modelling of non-structural components of an industrial multi-storey frame for seismic risk assessment

Seismic risk assessment of industrial facilities is complex due to the presence of different types of equipment. It represents a research issue that requires further investigation. To this end, some analytical approaches have been developed in the framework of performance-based earthquake engineering. Nonetheless, their accuracy in the case of complex critical facilities, such as nuclear and non-nuclear industrial plants, is still under investigation. Thus, the proposed study intends to research in depth, in a risk assessment framework, some critical aspects related to: (1) modelling of industrial facilities and their secondary equipment with different degrees of accuracy, also taking into account their dynamic interaction; (2) selection of seismic records for fragility analysis, due to the narrow distribution of frequency values for non-structural components; (3) effectiveness of performance-based earthquake engineering applied to this particular class of coupled structure-equipment for risk assessment. In this context, the proper selection of seismic records becomes relevant, and SCoRes, an innovative algorithm for accelerograms selection is worthy of investigation. On these premises, two different configurations of a primary industrial structure, i.e. a moment resisting frame and a braced frame, equipped with non-structural components and subjected to shake table test campaigns are selected as case studies. For the two configurations, a vulnerability assessment of two vertical tanks installed on the first floor was carried out. Along these lines, to establish the effectiveness of the proposed method for both the moment resisting frame and braced frame configurations, the mean annual frequency of exceedance of the bottom-wall strain of the above-mentioned tanks, both at the design basis and safe shutdown earthquake has been evaluated.

The influence of hinged and rigid connections on the seismic behaviour of “Inverted Y” bracing systems

AbstractThe present paper intends to illustrate the seismic behaviour of different configurations for a ten storeyed “inverted Y” eccentrically braced frame provided with rigid and/or pined beam/column and diagonal/column connections. Four configurations were analysed for the “inverted Y” braced frame, sized for the forces produced by the same code seismic base shear force. In the first configuration, rigid connections were used for all kind of structural elements. The second configuration had hinged beam/column and diagonal/column connections. In case of the third configuration, rigid connections were used among all kind of structural elements and additional potentially plastic zones with reduced cross‐sections (resembling the “dog‐bone” detail) were considered along the girders and braces, near the member ends connected to the columns. The fourth configuration had hinged diagonal/column connections and additional potentially plastic zones were considered only along the frame girders, near the girder ends connected to the columns. The behaviour of each frame configuration during static and dynamic nonlinear analyses was observed. The extreme values for deformations and member forces were compared. The steel consumption was estimated for each of the four considered configurations.

In-plane seismic fragility models for clay masonry infills in reinforced concrete frames

This study aims at deriving multi-damage state fragility functions/curves for clay masonry infills in low-to-medium-rise reinforced concrete frames designed according to a performance-based seismic design methodology. Different structural archetypes were identified and modelled numerically by means of distributed plasticity approaches in order to undertake multi-stripe nonlinear dynamic analysis and derive seismic lognormal fragility models through regression analysis. Both infilled and bare frame configurations were simulated and compared together, providing fragility curves corresponding to immediate occupancy, damage prevention, and, ultimately, life safety limit states, all of which can be integrated in general frameworks for seismic risk/loss assessment and management. To this end, fragility models are given in terms of three different intensity measures, namely peak ground acceleration, peak floor acceleration, and peak floor spectral acceleration, considering also two different methods for the calculation of the probability of occurrence/exceedance of a certain damage state, namely building-wise and storey-wise approaches.