Investigation of ship collision with floating pier structures

Chegenizadeh, Amin,Ghadimi, Behzad,Nikraz, Hamid Techno-Press 2014 Interaction and multiscale mechanics Vol.7 No.1

This study investigated the collision of ships withfloating pier structures. The nature of the collision phenomenon is complex, and the understanding of it has developed through the modelling of offshore structures. ABAQUS software was used to investigate the collision phenomenon. The interaction between the ship and structural system was modelled, and the stress distribution both at thetime of collision and afterwardswasobserved and modelled. The strain energy absorption by different structural partswas calculated and comparisonswere made.

Investigation of ship collision with floating pier structures

Chegenizadeh, Amin,Ghadimi, Behzad,Nikraz, Hamid Techno-Press 2014 Coupled systems mechanics Vol.3 No.3

This study investigated the collision of ships withfloating pier structures. The nature of the collision phenomenon is complex, and the understanding of it has developed through the modelling of offshore structures. ABAQUS software was used to investigate the collision phenomenon. The interaction between the ship and structural system was modelled, and the stress distribution both at thetime of collision and afterwardswasobserved and modelled. The strain energy absorption by different structural partswas calculated and comparisonswere made.

Landslide Risk Assessment by using a New Combination Model based on a Fuzzy Inference System Method

S. Reza Azimi,Hamid Nikraz,Abdolreza Yazdani-Chamzini 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

Landslides are one of the most dangerous phenomena that pose widespread damage to property and human lives. Over the recent decades, a large number of models have been developed for landslide risk assessment to prevent the natural hazards. These models provide a systematic approach to assess the risk value of a typical landslide. However, often models only utilize the numerical data to formulate a problem of landslide risk assessment and neglect the valuable information provided by experts’ opinion. This leads to an inherent uncertainty in the process of modelling. On the other hand, fuzzy inference systems are among the most powerful techniques in handling the inherent uncertainty. This paper develops a powerful model based on fuzzy inference system that uses both numerical data and subjective information to formulate the landslide risk more reliable and accurate. The results show that the proposed model is capable of assessing the landslide risk index. Likewise, the performance of the proposed model is better in comparison with that of the conventional techniques.

A novel two-dimensional approach to modelling functionally graded beams resting on a soil medium

Chegenizadeh, Amin,Ghadimi, Behzad,Nikraz, Hamid,Simsek, Mesut Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.5

The functionally graded beam (FGB) is investigated in this study on both dynamic and static loading in case of resting on a soil medium rather than on the usual Winkler-Pasternak elastic foundation. The powerful ABAQUS software was used to model the problem applying finite element method. In the present study, two different soil models are taken into account. In the first model, the soil is assumed to be an elastic plane stress medium. In the second soil model, the Drucker-Prager yield criterion, which is one of the most well-known elastic-perfectly plastic constitutive models, is used for modelling the soil medium. The results are shown to evaluate the effects of the different soil models, stiffness values of the elastic soil medium on the normal and shear stress and free vibration properties. A comparison was made to those from the existing literature. Numerical results show that considering real soil as a continuum space affects the results of the bending and the modal properties significantly.

A novel two-dimensional approach to modelling functionally graded beams resting on a soil medium

Amin Chegenizadeh,Behzad Ghadimi,Hamid Nikraz,Mesut Simsek 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.5

The functionally graded beam (FGB) is investigated in this study on both dynamic and static loading in case of resting on a soil medium rather than on the usual Winkler-Pasternak elastic foundation. The powerful ABAQUS software was used to model the problem applying finite element method. In the present study, two different soil models are taken into account. In the first model, the soil is assumed to be an elastic plane stress medium. In the second soil model, the Drucker-Prager yield criterion, which is one of the most well-known elastic-perfectly plastic constitutive models, is used for modelling the soil medium. The results are shown to evaluate the effects of the different soil models, stiffness values of the elastic soil medium on the normal and shear stress and free vibration properties. A comparison was made to those from the existing literature. Numerical results show that considering real soil as a continuum space affects the results of the bending and the modal properties significantly.

An Evaluation of Moisture Damage Resistance of Asphalt Concrete based on Dynamic Creep Characteristics

Peerapong Jitsangiam,Korakod Nusit,Hamid Nikraz 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4

The performance of asphalt concrete is severely influenced by moisture. The presence of moisture in asphalt pavement substantially reduces its designed service lifetime. Currently, the indirect tensile strength test with constant loading rate is employed to estimate the moisture damage potential to an asphalt mixture. This evaluation method is empirical in nature and, therefore, suitable for only empirically designed asphalt pavements. However, speculation exists in that the conventional testing method may inappropriately simulate actual field conditions. Therefore, this research aims to evaluate the moisture damage potential to asphalt concrete under cyclic loading using the dynamic creep testing platform. The dynamic creep test provides the flow number, which represents the number of loading cycles at the failure point of the asphalt mixture. Three different types of asphalt mixtures commonly used in Western Australia were investigated in this research. The dynamic creep test provided more reasonable evaluation results of potential moisture damage than the conventional method. The tensile strength ratio of all mixtures in this research were greater than 80%, which is the conventional design criteria. On the other hand, the dynamic creep test reveals that flow number ratio of two mixtures dropped below 80%. The flow number ratio of 14 mm mixture was 58%, while 56% was obtained from 20 mm mixture. However, high uncertainty in the dynamic creep test results was observed, due to the interpretation technique. In conclusion, based on the research findings, the dynamic creep test can be used as a complementary test of the stripping potential in asphalt concrete.

Effect of slag and bentonite on shear strength parameters of sandy soil

Sabbar, Ayad Salih,Chegenizadeh, Amin,Nikraz, Hamid Techno-Press 2018 Geomechanics & engineering Vol.15 No.1

A series of direct shear tests were implemented on three different types of specimens (i.e., clean Perth sand, sand containing 10, 20 and 30% bentonite, sand containing 1, 3 and 5% slag, and sand containing 10, 20 and 30% bentonite with increasing percentages of added slag (1%, 3% and 5%). This paper focuses on the shear stress characteristics of clean sand and sand mixtures. The samples were tested under different three normal stresses (100, 150 and 200 kPa) and three curing periods of no curing time, 7 and 14 days. It was observed that the shear stresses of clean sand and mixtures were increased with increasing normal stresses. In addition, the use of slag has improved the shear strength of the sand-slag mixtures; the shear stresses rose from 128.642 kPa in the clean sand at normal stress of 200 kPa to 146.89 kPa, 154 kPa and 161.14 kPa when sand was mixed with 1%, 3% and 5% slag respectively and tested at the same normal stress. Internal friction angle increased from $32.74^{\circ}$ in the clean sand to $34.87^{\circ}$, $37.12^{\circ}$ and $39.4^{\circ}$ when sand was mixed with 1%, 3% and 5% slag respectively and tested at 100, 150, and 200 kPa normal stresses. The cohesion of sand-bentonite mixtures increased from 3.34 kPa in 10% bentonite to 22.9 kPa, 70.6 kPa when sand was mixed with 20% and 30% bentonite respectively. All the mixtures of clean sand, different bentonite and slag contents showed different behaviour; some mixtures exhibited shear stress more than clean sand whereas others showed less than clean sand. The internal friction angle increased, and cohesion decreased with increasing curing time.