Reliability and Reliability-based Sensitivity Analyses of Steel Moment-Resisting Frame Structure subjected to Extreme Actions

The ground external columns of buildings are vulnerable to the extreme actions such as a vehicle collision. This event is a common scenario of buildings' damages. In this study, a nonlinear model of 2-story steel moment-resisting frame (SMRF) is made in OpenSees software. This paper aims investigating the reliability analysis of aforementioned structure under heavy vehicle impact loadings by Monte Carlo Simulation (MCS) in MATLAB software. To reduce computational costs, meta-model techniques such as Kriging, Polynomial Response Surface Methodology (PRSM) and Artificial Neural Network (ANN) are applied and their efficiency is assessed. At first, the random variables are defined. Then, the sensitivity analyses are performed using MCS and Sobol's methods. Finally, the failure probabilities and reliability indices of studied frame are presented under impact loadings with various collision velocities at different performance levels and thus, the behavior of selected SMRF is compared by using fragility curves. The results showed that the random variables such as mass and velocity of vehicle and yield strength of used materials were the most effective parameters in the failure probability computation. Among the meta-models, Kriging can estimate the failure probability with the least error, sample number with minimum computer processing time, in comparison with MCS

Influence of Geometric Parameters on The Performance of Welded Angle Seat Connections Under High-Temperature Loading

The prevalence of various types of experimental and numerical uses in this area is mostly due to the significance of welded connections in the behaviour of steel moment-resisting frames (SMRFs). The most effective conditions that aggravates the undesirable performance of welded connections is high-temperatures. With regard to conduct analytical research, three types of welded angle seat connections will be selected for finite element modeling (FEM) in ABAQUS software to investigate the performance of them under high-temperature loading. The parameters of increasing thickness, length of welded angle seat connection, and simple connection with angle by adding stiffener are assessed. For this aim, a flexible angle seat connection is used to help the web angle. The characteristics of the web angles and seats are determined based on the features of the beam. Based on the results, the sample COL-ST10-L50-SP15 has the best performance versus other samples. In this sample, beam to column connection is welded angle seat with dimensions such as 10 mm thickness, 50 mm length and 15 mm thickness of stiffener. The displacement of this sample is 502.52 mm under heat conditions. It means that the displacement ratio of the mentioned sample is 18.25% versus reference sample. Therefore, the results showed that by increasing the heat, two important factors should be suggested in the design of steel connections. These factors such as increasing the force due to longitudinal expansion and decreasing the strength and stiffness are considered.Journal of civil Engineering and Materials Applicatio

Finite Element Modeling of Self-Compacting Concrete Beams Under Shear

Development of self-compacting concrete (SCC) is a very desirable achievement in the reinforced concrete (RC) structures for overcoming issues associated with many problems such as congestions of steel reinforcement. This non-vibrating concrete is not affected by the skill of workers, and the shape and amount of reinforcing bar arrangement of a structure. Due to the high fluidity and resisting power of reinforcing of SCC, it can be pumped longer distances. In this study, the finite element (FE) modeling of three SCC beams in shear while taking into account, the flexural tensile strength of concrete is computed and the results are compared with the available experimental tested reinforced SCC beams. The stirrups are located at 75 mm apart from the end of beams up to the loading point. The electrical strain gauges (ESGs) have been embedded on the stirrups and their strain readings are taken for every step of load increment. For modeling longitudinal steel reinforcing bars and concrete, the 3-D elements with 2-node and 8-node, are used respectively. The comparison of results obtained by two methods is indicated that a good satisfactory agreement is achieved

Effectiveness of Executive Functions Training on Social Skills in Students with Dyslexia

The purpose of this study was examining the impact of executive functions training on social skills in students with dyslexia. This study is an experimental one with pre-test, post - test and control group design. The statistical population of this research includes all the students with dyslexia in second and third grade of elementary schools of Abbas Abad in Mazandaran province in school year of 2012-2013, which 20 of them were selected based on entering qualities and assigned in experimental and control groups randomly. Executive function training was taught to experimental group within ten sessions for a period of one month, while the control group did not receive this training. Both groups were assessed in pre- test and post- test using social skills questionnaire (Gresham, 1999). Analysis of data using multivariate covariance indicated that there was significant difference between two groups on social skills. So, we can conclude that in education and treatment students with dyslexia, strengthening executive functions should be considered on of the basic dimensions for experts and educators

Investigation of the Occurrence of Progressive Collapse in High-Rise Steel Buildings with Different Braced Configurations

The progressive collapse phenomenon refers to a chain of damages in a structure where all or a large part of the structure is destroyed by an initial local collapse in it, which can lead to very disastrous results. Therefore, the prevention of progressive collapse has become a necessary action in the design and analysis of buildings and it is vital to investigate this topic more accurately. This study aims to present a proposed pattern in the configuration of braces at the height of a high-rise steel building for reducing the probability of progressive collapse. In this regard, the vertical displacement of 18-story structure with four scenarios of column removal and five concentric bracing patterns including V, Inverted V, X, discontinuous X-bracing at height, and a combination of Xbracing in the side spans and discontinuous X-bracing at height in the middle spans are investigated and compared. In this study, the Alternative Path Method (APM) is used based on the GSA guideline for the analysis of progressive collapse. The results of this research showed that the use of X-bracing in the side spans and discontinuous X-bracing in the middle spans in nonlinear static and dynamic analyses performed better in reducing the probability of progressive collapse than other bracing configurations. Finally, it is recommended to use discontinuous X-bracing at the height that would place the bracings in one direction and providing alternative paths for force transferring in the structure