Effect of crack location on buckling analysis and SIF of cracked plates under tension

Parham Memarzadeh,Sayedmohammad Mousavian,Mohammad Hosseini Ghehi,Tadeh Zirakian 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.2

Cracks and defects may occur anywhere in a plate under tension. Cracks can affect the buckling stability performance and even the failure mode of the plate. A search of the literature reveals that the reported research has mostly focused on the study of plates with central and small cracks. Considering the effectiveness of cracks on the buckling behavior of plates, this study intends to investigate the effects of some key parameters, i.e., crack size and location as well as the plate aspect ratio and support conditions, on the buckling behavior, stress intensity factor (SIF), and the failure mode (buckling or fracture) in cracked plates under tension. To this end, a sophisticated mathematical code was developed using MATLAB in the frame-work of extended finite element method (XFEM) in order to analyze the buckling stability and collapse of numerous plate models. The results and findings of this research endeavor show that, in addition to the plate aspect ratio and support conditions, careful consideration of the crack location and size can be quite effective in buckling behavior assessment and failure mode prediction as well as SIF evaluation of the cracked plates subjected to tensile loading.

Regression and ANN models for durability and mechanical characteristics of waste ceramic powder high performance sustainable concrete

Babak Behforouz,Parham Memarzadeh,Mohammadreza Eftekhar,Farshid Fathi 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.2

There is a growing interest in the use of by-product materials such as ceramics as alternative materials in construction. The aim of this study is to investigate the mechanical properties and durability of sustainable concrete containing waste ceramic powder (WCP), and to predict the results using artificial neural network (ANN). In this order, different water to binder (W/B) ratios of 0.3, 0.4, and 0.5 were considered, and in each W/B ratio, a percentage of cement (between 5-50%) was replaced with WCP. Compressive and tensile strengths, water absorption, electrical resistivity and rapid chloride permeability (RCP) of the concrete specimens having WCP were evaluated by related experimental tests. The results showed that by replacing 20% of the cement by WCP, the concrete achieves compressive and tensile strengths, more than 95% of those of the control concrete, in the long term. This percentage increases with decreasing W/B ratio. In general, by increasing the percentage of WCP replacement, all durability parameters are significantly improved. In order to validate and suggest a suitable tool for predicting the characteristics of the concrete, ANN model along with various multivariate regression methods were applied. The comparison of the proposed ANN with the regression methods indicates good accuracy of the developed ANN in predicting the mechanical properties and durability of this type of concrete. According to the results, the accuracy of ANN model for estimating the durability parameters did not significantly follow the number of hidden nodes.

Study of buckling stability of cracked plates under uniaxial compression using singular FEM

Sina Saberi,Parham Memarzadeh,Tadeh Zirakian 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.4

Buckling is one of the major causes of failure in thin-walled plate members and the presence of cracks with different lengths and locations in such structures may adversely affect this phenomenon. This study focuses on the buckling stability assessment of centrally and non-centrally cracked plates with small-, intermediate-, and large-size cracks, and different aspect ratios as well as support conditions, subjected to uniaxial compression. To this end, numerical models of the cracked plates were created through singular finite element method using a computational code developed in MATLAB. Eigen-buckling analyses were also performed to study the stability behavior of the plates. The numerical results and findings of this research demonstrate the effectiveness of the crack length and location on the buckling capacity of thin plates; however, the degree of efficacy of these parameters in plates with various aspect ratios and support conditions is found to be significantly different. Overall, careful consideration of the aspect ratio, support conditions, and crack parameters in buckling analysis of plates is crucial for efficient stability design and successful application of such thin-walled members.

Numerical Investigation of I-Shaped Beam to Concrete Filled Tube Column Connection Without Continuity Plate

Shohreh Sohaei,Mehrzad Tahamouli Roudsari,Parham Memarzadeh 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.6

Circular columns are increasingly being used in today’s construction industry. Proper construction beam-circular column connections are an important problem in steel moment resisting frames with this type of connection. TahamouliRoudsari et al. introduced a new I-shaped beam-circular concrete-fi lled column connection in 2020. This connection makes use of a strengthened U-shaped profi le as an external stiff ener with simple detailing. Experimental tests showed that the connection satisfi es code-specifi ed criteria for rigid connections. The main objective of the present work is to present design guidelines and a more accurate numerical investigation of the detailing introduced by TahamouliRoudsari et al. For this, in the fi rst step, a numerical model of the experimental specimen was constructed and verifi ed in the ABAQUS fi nite element software. Then, through multiple nonlinear fi nite element analyses, it has been demonstrated that this type of connection can meet all the requirements of special moment resisting frames with rigid connections. The minimum thickness for the strengthened U-shaped profi le has been determined in such a way so that the plastic hinge could be created in the beam and the connection would have suffi cient stiff ness to be categorized as fully restrained. The eff ects of the geometry of the stiff ened channel link and the column-to-beam section modulus ratio on the behavior of the connection were investigated and a relationship has been developed to calculate the thickness of the stiff ened channel profi le. Also, evaluating the eff ects of axial loading in the column showed that the thickness of the U-shaped profi le and the stiff eners have no bearing on the axial load applied to the column.

Experimental evaluation of steel connections with horizontal slit dampers

Hossein Akbari Lor,Mohsen Izadinia,Parham Memarzadeh 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.1

This study introduces new connections that connect the beam to the column with slit dampers. Plastic deformations and damages concentrate on slit dampers. The slit dampers prevent plastic damages of column, beam, welds and panel zone and act as fuses. The slit dampers were prepared with IPE profiles that had some holes in the webs. In this paper, two experimental specimens were made. In first specimen (SDC1), just one slit damper connected the beam to the column and one IPE profile with no holes connected the bottom flange of the beam to the column. The second specimen (SDC2) had two similar dampers which connected the top and bottom flange of the beam to the column. Cyclic loading was applied on Specimens. The cyclic displacements conditions continued until 0.06 radian rotation of connection. The experimental observations showed that the bending moment of specimen SDC2 increased until 0.04 story drift. In specimen SDC1, the bending moment decreases after 0.03 story drift. Test results indicate the high performance of the proposed connection. Based on the results, the specimen with two slit damper (SDC2) has higher seismic performance and dissipates more energy in loading process than specimen SDC1. Theoretical formulas were extended for the proposed connections. Numerical studies have been done by ABAQUS software. The theoretical and numerical results had good agreements with the experimental data. Based on the experimental and numerical investigations, the high ductility of connection is obtained from plastic damages of slit dampers. The most flexural moment of specimen SDC1 occurred at 3% story drift and this value was 1.4 times the plastic moment of the beam section. This parameter for SDC2 was 1.73 times the plastic moment of the beam section and occurred at 4% story drift. The dissipated energy ratio of SDC2 to SDC1 is equal to 1.51.