Machine Learning for Modeling the Bearing Capacity of Prestressed Concrete Elements Damaged by Corrosion

This work aims to study the prediction of bearing capacity of prestressed concrete beams subjected to accelerated corrosion process using Machine Learning (ML) techniques. After data collection, the results were used to model the behavior of flexural stress, and predict their final load capacity, considering position, length, and width of the cracks generated by corrosion as well as loss of bearing capacity. The study presents an analysis of 363 days old beams damaged by corrosion, connected to a galvanostat for 62, and 121 days to make faster the process. Six beams were analyzed; five of them were used to train the model, the other works as a basis to compare the results thrown by the model with the real data. After the treat, the results showed that Bagged Trees Model fits better to real data, it was seen that removing atypical data improves the correlation of predicted and real data. The actual data were compared with two different prediction analyzes; for the first one, the atypical data were not removed; in the second one, the atypical data were eliminated with a statistical analysis. Obtaining relative error percentages of 15.18%, 14.59%, presenting two predictions: final load of 1444 kg and 1126 kg. Which means a resistant moment of 650 T-m, and 506.7 T-m respectively, taking as a prediction the second value in the safe side.

Numerical modeling of structural capacity of corroded bolted assembly

PurposeValidate the resistance of bolted connections in terms of stresses, resistant moment and contact pressure.Design/methodology/approachFinite element modeling of corroded bolted joint.FindingsThe three types of corroded assemblies are resistant to the applied loads.Originality/valueThe research is original, it studies the stress corrosion cracking of a bolted assembly's end plate by the finite element method.

Lateral distortional buckling of cellular composite-beams

In the region of negative bending moments of continuous and semi-continuous steel and concrete composite beams, the inferior portion of the steel section is subjected to compression while the top flange is restricted by the slab, which may cause a global instability limit state know as lateral distortional buckling (LDB) characterized by a lateral displacement and rotation of the bottom flange with a distortion of the section’s web when it doesn’t have enough flexural rigidity. The ABNT NBR 8800:2008 provides an approximate procedure for the verification of this limit state, in which the resistant moment to LDB is obtained from the elastic critical moment in the negative moment region. One of the essential parameters for the evaluation of the critical moment is the composite beam’s rotational rigidity. This procedure is restricted only to to steel and concrete composite beams with sections that have plane webs. In this paper, an equation for the calculation of the rotational rigidity of cellular sections was developed in order to determine the LDB elastic critical moment. The formulation was verified by numerical analyses performed in ANSYS and its efficiency was confirmed. Finally, the procedure described in ABNT NBR 8800:2008 for the calculation of the critical LDB moment was expanded to composite beams with cellular sections in a numerical example with the appropriate modifications in geometric properties and rotational rigidity.

On the Robustness of Earthquake-Resistant Moment-Resistant Frames: Influence of Innovative Beam-to-Column Joints

Background: The deformation capacity of beam-to-column connections strongly influences the robustness of earthquake-resistant Moment Resistant Frames (MRFs) when subjected to a loss-of column scenario. As a consequence, with the aim of foresee the structural response up to the failure, an accurate modelling of the ultimate behaviour of the joints is needed. Objective: In this paper, the influence of the connections on the behaviour of MRFs under a loss-of-column scenario has been analysed considering an accurate modelling of the joints. Method: In addition, in order to achieve this goal, different beam-to-column joints designed for seismic actions and tested at the Salerno University, have been modelled and introduced in a case-study structure, whose response has been evaluated by means of push-down analyses. In particular, the connections analysed and modelled are of three different types: a dog-bone connection, a partial strength Double Split Tee (DST) joint and a partial strength connection with friction dampers. Results / Conclusion: The results of pushdown analyses performed by means of SAP2000 computer software have been examined with the aim to determine the Residual Reserve Strength Ratio (RRSR) index that, combined with the energy balance method proposed by Izzudin et al. (2008), allow to assess the structural ro-bustness.

Application Research on Horizontal Static Load for Elastic Long Pile

Based on Winkler model and engineering example, the behavior of elastic long pile under horizontal load was analyzed in test status while pile top at solid respectively. The analysis results show that under same horizontal static load, the maximum of pile shaft bending moment in work status is higher then it in test status. The horizontal bearing capacity of pile in work status can be get based on the proportion coefficient of the horizontal resistance coefficient, m, and crack-resistant moment calculated by critical load, Hcr. While m and Hcr can be obtained by horizontal static load test.

Characteristic Parameters of Surface Electromyography Signals of Cervical Muscles

Surface electromyography (SEMG) signals of cervical muscles are investigated by time-frequency analysis and biomechanics analysis. Medium frequency (MF) and integrated electromyography (IEMG) are extracted and analyzed from SEMG signals of subjects’ upper trapezius. The Experimental results show that the value of MF decreases and the value of IEMG increases with the increase of fatigue of the vertical muscles. Also, the values of IEMG at different testing points of same cervical muscle are compared. The value of IEMG with higher resistant moment is higher than that with lower resistant moment. That means the muscle with high resistance moment is easier to be fatigue. This investigation is important for people, especially those who work/read with bowing head or before computer for a long time, to prevent cervical spondylosis.

A Generalized Model for Adhesive Contact Between a Rigid Cylinder and a Transversely Isotropic Substrate

In this paper, a solution to the quasi-static adhesive contact problem between a rigid cylinder and a transversely isotropic substrate is extended to the most general case by taking adhesion hysteresis into account. An analytical solution to the contact stress is obtained by solving the integral equations established on the basis of the Green's function for the two-dimensional transversely isotropic half-space problem. By using equilibrium conditions and Griffith's criterion, the adhesion force and resistant moment to rolling are determined as functions of contact geometries and material properties of the contacting solids. Detailed discussions on the adhesion force and resistant moment are presented for some specific cases, revealing adhesion behaviors that have not been predicted by previous models. As the most generalized solution to the discussed problem, our results would have extensive applications in predicting the adhesion behavior between solids undergoing sophisticated mechanical loadings.