Experimental and Numerical Analysis on the Core Lateral Thrust in Bolted BRBs

The paper aims at presenting numerical and experimental results on the lateral thrust exerted by the inner core of a buckling restraining brace (BRB) when, after buckling in compression, it arrives into contact with the external restraining case. The BRB consisted of a plate core restrained by bolted U- shaped member, thus allowing an easy assembly of the BRB, as well as the inspection and the substitution of its core after a seismic event [1, 2]. The results of six tests on BRBs having a plate core with a cross section of 5x50 mm2 and a dissipative length of 560 mm are shown. The gap dimension was varied between 0.25 and 0.70 mm. Cyclic displacements of increasing amplitude were applied to the core up to a steel strain of 2%, adopting the loading history prescribed by AISC standards [3]. The instrumented bolts connecting the restraining elements and a thin tactile pressure sensor placed within the gap allowed to steadily monitor both the lateral thrust and the buckling shape of the plate core during the experiment. The results showed that the lateral thrust increased linearly with the gap dimension, thus confirming the trend provided by the analytical formulation proposed by Genna and Gelfi [4]. As reported in Table 1, for a maximum axial force of about 110 kN, the value of the transverse thrust ranged from 36.5 kN in the specimen 1 with a gap of 0.25 mm to 86.6 kN in the specimen 3 with a gap of 0.70 mm. Furthermore, the specimens 6, without stiffening plates in the web of the restraining U- profiles, showed the significant role of the local transverse deformation on the value of the lateral thrust, which was twice the thrust of the specimen 1, characterized by the same gap of 0.25 mm but with a stiffened case. The experimental results allowed to validate a non-linear 3D Finite Element model performed with the code ABAQUS [5]. The numerical analyses accurately predicted the cyclic behaviour of the tested BRBs in term of axial load, buckling shape of the core and lateral thrust action. The difference between the measured thrust and the calculated thrust at the end of the loading history (steel strain c=2%) ranges between -8% to +17%, while the 2D plane stress model proposed in [6] overestimated the lateral thrust of +85%, owing to the inability of the 2D model to describe the local transverse deformations of the case

A Procedure for Performing Nonlinear Pushover Analysis for Tsunami Loading to ASCE 7

The new ASCE 7-16 Chapter 6 offers a comprehensive and practical methodology for the design of structures for tsunami loads and effects. While it provides prescriptive tsunami loading and design requirements, Chapter 6 also allows for the use of performance-based nonlinear analysis tools. However, the specifics of load application protocol and system and component evaluation for such a nonlinear approach are not provided. This paper presents a procedure for performing nonlinear static pushover analysis for tsunami loading within the framework of the ASCE 7-16 standard. Through this approach, the user can both estimate the effective systemic lateral load-resisting capacity of a building and the local component demand. This enables the identification of deficiencies in structural elements with respect to the ASCE 7-16 standard acceptance criteria. To demonstrate the procedure, a prototypical reinforced concrete multistory building exposed to high tsunami hazard on the US Northwest Pacific Coast is assessed. This is a building with sufficient height to provide last-resort refuge for people having insufficient time to evacuate outside the inundation zone. The results of the nonlinear static pushover analyses show that the structural system has sufficient lateral strength to resist ASCE 7-16 prescribed tsunami loads, but fails the checks for component-based loading, with the exterior ground-story columns observed to fail in flexure and shear. The example demonstrates that use of the tsunami nonlinear static analysis procedure allows the identification of structural deficiencies such that a targeted strengthening of the building can be conducted (i.e., flexural and shear strengthening of the seaward and inland columns for the case study building presented), leading to significantly reduced costs

A nonlinear static procedure for the tsunami design of a reinforced concrete building to the ASCE7 Standard

New ASCE 7-16 Chapter 6 offer a comprehensive and practical methodology for the design of structures for tsunami loads and effects. While they provide prescriptive tsunami loading and design requirements, they also allow for the use of performance-based analysis tools. However, no guidance is provided as to how the performance-based analysis should be performed. This paper presents an improved nonlinear static pushover procedure for the assessment of the nonlinear capacity of structures to tsunami, within the framework of the ASCE 7-16 provisions. For this purpose, a prototypical reinforced concrete multi-storey building exposed to high tsunami hazard in the US Northwest Pacific coast is assessed. This is a building with sufficient height to provide last-resort refuge for people having insufficient time to evacuate outside the inundation zone. Two different tsunami load discretisation methods are applied to investigate the structural capacity under tsunami systemic and component loading, respectively. The results of the nonlinear static pushover analyses show that the structural system has sufficient lateral strength to resist ASCE 7-16 prescribed tsunami loads. However, when component-based loading is considered, the seaward ground storey columns are observed to fail in shear, precipitating structural failure. This is in agreement with the ASCE 7-16 simplified systemic acceptance criteria, i.e. that the structure is unsafe for use as a refuge, and that it would require significant strengthening. However, the use of the VDPO provides information of what needs to be strengthened in order to improve the tsunami performance of the structure

Fragility functions for a reinforced concrete structure subjected to earthquake and tsunami in sequence

Many coastal regions lying on subduction zones are likely to experience the catastrophic effects of cascading earthquake and tsunami observed in recent events, e.g., 2011 Tohoku Earthquake and Tsunami. The influence of earthquake on the response of the structure to tsunami is difficult to quantify through damage observations from past events, since they only provide information on the combined effects of both perils. Hence, the use of analytical methodologies is fundamental. This paper investigates the response of a reinforced concrete frame subjected to realistic ground motion and tsunami inundation time histories that have been simulated considering a seismic source representative of the M9 2011 Tohoku earthquake event. The structure is analysed via nonlinear time-history analyses under (a) tsunami inundation only and (b) earthquake ground motion and tsunami inundation in sequence. Comparison of these analyses shows that there is a small impact of the preceding earthquake ground shaking on the tsunami fragility. The fragility curves constructed for the cascading hazards show less than 15% reduction in the median estimate of tsunami capacity compared to the fragility functions for tsunami only. This outcome reflects the fundamentally different response of the structure to the two perils: while the ground motion response of the structure is governed by its strength, ductility and stiffness, the tsunami performance of the structure is dominated by its strength. It is found that the ground shaking influences the tsunami displacement response of the considered structure due to the stiffness degradation induced in the ground motion cyclic response, but this effect decreases with increasing tsunami force

Observations from the EEFIT-TDMRC mission to Banda Aceh, Indonesia to investigate the recovery from the 2004 Indian Ocean Tsunami

On 26th December 2004 a subduction zone earthquake of magnitude Mw 9.3 struck off the coast of Sumatra in Indonesia. A large area of the Indian Ocean seabed was vertically displaced, and as a result a tsunami wave was generated that went on to affect many countries around the world. One of the worst hit places was the Aceh province of Sumatra where the capital city, Banda Aceh, experienced serious ground shaking and significant sea water inundation. In Indonesia at least 126,732 people were killed, a further 93,652 people were confirmed missing and 533,770 people were displaced. In 2022, nearly 20 years on from the disaster, engineers and scientists from the UK Earthquake Engineering Field Investigation Team (EEFIT) and from the Indonesian Tsunami and Disaster Mitigation Research Centre (TDMRC) conducted a joint longterm recovery mission. This paper reflects on how a society rebuilds after such a devastating loss and what lessons can be learnt as a community for future disaster risk reduction. The scope of the paper includes the rapid assessment of post-disaster housing, community infrastructure and preparedness measures

Advancing in the analysis of materials in electr(on)ic equipment

Despite there is a great effort to support strategies for a circular economy of electr(on)ics as maintenance, repair, remanufacture and reuse, recycling keeps being the final ultimate stage reached by them. As the supply of materials has become a key issue for the economic and technology development, more information about the content of materials in electr(on)ics is in order. This is especially for printed circuit boards contained in the majority of electr(on)ics which have a great variety of materials with a significant economic value. This paper discusses two methodologies to quantify the material composition of these parts. The first methodology quantifies the material content using two algorithms to identify the typologies of electr(on)ics components, and the average material composition of some typologies of electr(on)ic components given by original manufacturers. The second methodology uses the Database of SEmiconductors (DoSE) which contains the full material composition of about 250 different electr(on)ic components of printed circuit boards. A case study based on the analysis of two models of battery management systems contained in the batteries of electric vehicles is developed to compare the material composition results obtained from the two methodologies. Although the analysis is limited to some electr(on)ic components, mainly the integrated circuit and capacitors, the results of the composition of the battery management system are given for a list of materials including aluminum, copper, iron, gold, lead, nickel and tantalum. For two of the most economically relevant materials, copper and gold, the results obtained by the two methodologies differ 2% for copper and 4% for gold. To advance towards more automatized and systematic methodologies to estimate the material composition of the battery management systems, there are some further developments needed: to increase datasets for other electr(on)ic components as connectors, and better quantification of the number of layers and finishing of the circuit boards as they are made of significant quantities of copper and gold

Ultralow Cycle Fatigue Tests and Fracture Prediction Models for Duplex Stainless-Steel Devices of High Seismic Performance Braced Frames

This paper presents ultralow cycle fatigue tests and the calibration of different fracture models for duplex stainless-steel devices of high seismic performance braced frames. Two different geometries of the devices were tested in full scale under 14 cyclic loading protocols up to fracture. The imposed protocols consisted of standard, constant-amplitude, and randomly generated loading histories. The test results show that the devices have stable hysteresis, high postyield stiffness, and large energy-dissipation and fracture capacities. Following the tests, two micromechanics-based models, i.e., the cyclic void growth model and the built-in ABAQUS ductile fracture model, were calibrated using monotonic and cyclic tests on circumferentially notched coupons and complementary finite-element simulations. In addition, Coffin-Manson-like relationships were fitted to the results of the constant-amplitude tests of the devices, and the Palmgren-Miner’s rule was used to predict fracture of the devices under the randomly generated loading protocols. Comparisons of the experimental and numerical results show that the calibrated models can predict ductile fracture of the devices due to ultralow cycle fatigue with acceptable accuracy

Glutamatergic neurons induce expression of functional glutamatergic synapses in primary myotubes.

The functioning of the nervous system depends upon the specificity of its synaptic contacts. The mechanisms triggering the expression of the appropriate receptors on postsynaptic membrane and the role of the presynaptic partner in the differentiation of postsynaptic structures are little known.To address these questions we cocultured murine primary muscle cells with several glutamatergic neurons, either cortical, cerebellar or hippocampal. Immunofluorescence and electrophysiology analyses revealed that functional excitatory synaptic contacts were formed between glutamatergic neurons and muscle cells. Moreover, immunoprecipitation and immunofluorescence experiments showed that typical anchoring proteins of central excitatory synapses coimmunoprecipitate and colocalize with rapsyn, the acetylcholine receptor anchoring protein at the neuromuscular junction.These results support an important role of the presynaptic partner in the induction and differentiation of the postsynaptic structures

MICROPILES TRIPODS SHIELDS (MTS) AS UNCONVENTIONAL BREAKERS FOR THE CONTROL OF MODERATELY RAPID EARTHFLOWS (SASSI NERI LANDSLIDE, NORTHERN APENNINES)

The paper deals with the idea, design and implementation of unconventional one-of-a-kind Micropiles Tripods Shields (MTS) intended to break and decelerate moderately rapid earthflows surges in the track zone of the Sassi Neri landslide (Nure Valley, Northern Apennines, Province of Piacenza, Italy). The MTS are inspired to floating anchors and “chevaux de fries” used in wartime. The basic elements are tripods of 193 mm diameter steel micropiles laid out at triangle, driven into the stable bedrock and emerging some meters aboveground. Each tripod consists of a vertical upslope central pile and two lateral oblique piles, linked by two transversal beams and connection plates aboveground. Multiple tripods are spaced along transversal rows to form Micropiles Tripods Shields (MTS) to advancing earthflows. The design of MTS has been based on field investigations such as boreholes and geophysics, that indicated a limited thickness of landslide deposits in the track zone where MTS have been installed. The forces resulting from active earthflows fronts have been estimated both with geotechnical and hydraulic computations. The analysis of vertical and transversal forces as well as bending moments acting on a single tripod versus the characteristic resistances was carried out using a bi-dimensional scheme with finite-elements software Plaxis, that indicated that the stress levels were compatible with the structural resistance of the tripods. The construction of MTS took place in 2018, involving working site preparation with partial lime-treatment of the surficial layers, underground micropiles drilling and installation, aboveground micropiles welding, tripods completion with connection beams and plates. Some tripods have been instrumented with load cells for monitoring earth pressures against micropiles, electric transducers for groundwater monitoring next to the piles, tiltmeters for tripods rotations and a total station for slope and tripods movements monitoring. Results show that the acceleration of slope movements corresponds to a generalized increase of pore water pressure at all the monitored tripods and to temporary slight tilting of the tripods which has so far being fully recovered when the landside slowed down and pressure decreased. This pioneering application indicates that once the characteristics of the earthflows are carefully considered, the depth to the bedrock in the installation zone is limited, and the logistical conditions in the field during construction are adequate, the MTS can be taken into consideration as a possible unconventional solution to break down and control moderately rapid earthflow

Robustness assessment of a steel self-centering moment-resisting frame under column loss

The robustness of a seismically-designed steel self-centering moment-resisting frame (SCMRF) under a column loss scenario is numerically assessed. The prototype SC-MRF is equipped with post-tensioned bars and optimised stainless steel energy dissipation devices. The SC-MRF was modelled in full detail using solid finite elements. The numerical model was calibrated using results from previous tests on post-tensioned beam-column connections and isolated component tests on the energy dissipation devices. Quasi-static analyses were carried out to identify the failure modes of the SC-MRF under a column loss scenario. Nonlinear dynamic analyses were also performed to evaluate the dynamic response of the frame and to assess the acceptance criteria against progressive collapse according to the current codes of practice. The results show that the SC-MRF has superior robustness and it can guarantee a high level of safety under a sudden column loss scenario due to the high fracture capacity of the stainless steel energy dissipation devices and the tie force resistance provided by the post-tensioned bars