Genetics diversity of Aphanius ginaonis and Aphanius dispar in Hormozgan and Bushehr coastal zones respectively using PCRRFLP molecular marker

In this study, two populations of Aphanius ginaonis (Holly, 1929) and Aphanius dispar (Ruppell, 1828) were examined to determine genetic diversity using PCR-RFLP technique. A total of 60 individual specimens were collected from Hormozgan and Bushehr internal waters, comprising two sampling sites; from Geno hot spring (30 individuals of A. ginaonis) and Mir Ahmad hot spring (30 individuals of A. dispar). The D-loop region of mitochondrial DNA (550 bp) was amplified using PCR followed by RFLP analysis based on 5 restriction endonuclease enzymes (AluI, DpnI, Eco47I, HindIII HinfI). In order to undertake data analysis, Arlequin 3.11 was applied. Results at population levels indicated that Geno individuals have more haplotype diversity than Mir Ahmad individuals (9 and 3 haplotypes respectively). However, further investigation using genetic techniques is required to clarify the molecular history and evolution of Aphanius species in this area. Results obtained from this research would be applicable to understand conservation genetics and management of this important fish species in Iran

Genetic characterization of Sillago sp. from Hormozgan coastal waters using microsatellite markers

Using 5 microsatellite loci Sillago sp. From Hormozgan North Persian Gulf were investigated through 68 specimens in two stations: Minab (31 specimens) and Bandar Lengeh (38 specimens). DNA was extracted using modified CTAB (Hexadecyl trimethyl-ammonium bromide) protocol. 5-17 alleles were observed in 5 loci with 8.4 mean allelic frequency. Observed and expected heterozygosity values was calculated (0.115<Ho<0.792), (0.598<He<0.902). Genetic distance and identity according to Nei was estimated 0.520 and 0.595 respectively which shows genetic distance of genus level. Significant deviation from Hardy-Weinberg equilibrium (p<0.001) was observed at all loci at two stations. Analysis of Molecular Variance (AMOVA) of Genetic differentiation index (Fst) revealed mean significant (p=0.001) differentiation between two studied regions and 3.90 gen flow. Despite low distance of two studied regions (180km) there are probably two distinct populations of Sillago sp. which should be considered in management efforts

On the FE modeling of FRP-retrofitted beam-column subassemblies

The use of fiber reinforced polymer (FRP) composites in strengthening reinforced concrete beam-column subassemblies has been scrutinised both experimentally and numerically in recent years. While a multitude of numerical models are available, and many match the experimental results reasonably well, there are not many studies that have looked at the efficiency of different finite elements in a comparative way in order to clearly identify the best practice when it comes to modelling FRP for strengthening. The present study aims at investigating this within the context of FRP retrofitted reinforced concrete beam-column subassemblies. Two programs are used side by side; ANSYS and VecTor2. Results of the finite element modeling using these two programs are compared with a recent experimental study. Different failure and yield criteria along with different element types are implemented and a useful technique, which can reduce the number of elements considerably, is successfully employed for modeling planar structures subjected to in-plane loading in ANSYS. Comparison of the results shows that there is good agreement between ANSYS and VecTor2 results in monotonic loading. However, unlike VecTor2 program, implicit version of ANSYS program is not able to properly model the cyclic behavior of the modeled subassemblies. The paper will be useful to those who wish to study FRP strengthening applications numerically as it provides an insight into the choice of the elements and the methods of modeling to achieve desired accuracy and numerical stability, a matter not so clearly explored in the past in any of the published literature

Probabilistic models for curvature ductility and moment redistribution of RC beams

It is generally accepted that, in the interest of safety, it is essential to provide a minimum level of flexural ductility, which will allow energy dissipation and moment redistribution as required. If one wishes to be uniformly conservative across all of the design variables, curvature ductility and moment redistribution factor should be calculated using a probabilistic method, as is the case for other design parameters in reinforced concrete mechanics. In this study, simple expressions are derived for the evaluation of curvature ductility and moment redistribution factor, based on the concept of demand and capacity rotation. Probabilistic models are then derived for both the curvature ductility and the moment redistribution factor, by means of central limit theorem and through taking advantage of the specific behaviour of moment redistribution factor as a function of curvature ductility and plastic hinge length. The Monte Carlo Simulation (MCS) method is used to check and verify the results of the proposed method. Although some minor simplifications are made in the proposed method, there is a very good agreement between the MCS and the proposed method. The proposed method could be used in any future probabilistic evaluation of curvature ductility and moment redistribution factors

A probabilistic study on the ductility of reinforced concrete sections

Although the current design codes apply reliability-based calibration procedures to evaluate safety factors for the strength based limit state, the safety factors used to ensure minimum ductility capacities are rather simple and are not resulted from a probability-based procedure. This study examines level of safety delivered by the current design codes with regards to providing minimum curvature ductility for reinforced concrete (RC) beams made with normal strength concrete. Reliability analysis results show that with regard to the strength limit state, the considered design codes are in good agreement with one another. However, there is considerable disparity in the level of safety provided for minimum curvature ductility amongst the codes. The provided reliability for the design to remain ductile is too low in some and just about acceptable in the others. This signifies the importance and the need to introduce reliability based methods of design for ductility

Reliability-based study on ductility measures of reinforced concrete beams in ACI 318

All rights reserved.This paper presents a reliability-based investigation into the ductility requirements of reinforced concrete beams designed based on the ACI Code. Results showed that the code-specified model for predicting ductility measures, such as the neutral axis depth, is considerably less reliable than it is for predicting the flexural strength. The ratio of the strain at tensile reinforcement to yield strain of steel was used to define a limit state to ensure adequate ductility in reinforced concrete beams. Due to variability in the material properties and model error, there is high variability in ductility measures, leading to a high probability of compressive failure. Based on a target probability of failure taken from the literature, it was found that modification of the current ductility requirements is desired. This research highlights the need for more reliability-based studies into the safety factors provided by the ACI Code for ensuring adequate ductility in reinforced concrete beams

(In press) A reliability-based investigation into ductility measures of RC beams designed based on fib Model Code 2010

A reliability-based investigation into the ductility measures of reinforced concrete (RC) beams designed based on the current fib Model Code 2010 (MC 2010) is presented in this paper. Based on ductility ratio (strain at tensile rebar to yield stress of steel), a limit state to ensure adequate ductility in RC beams is proposed. Results show that the ductility ratio generally follows a right-skewed distribution, and due to variability in the material properties and model error, there is high variability in the strain ductility. This high variability in the ductility ratio leads to a high probability of non-ductile behaviour for RC beams designed based on the code. This is more pronounced for normal-strength concrete and grade S500 steel. Based on a target probability taken from the literature, a modification to the allowable neutral axis depth advised by the code is proposed. Results presented in this paper indicate that more reliability-based studies into the safety factors provided by the MC 2010 for ensuring adequate ductility in RC beams are needed

Effectiveness of modified pushover analysis procedure for the estimation of seismic demands of buildings subjected to near-fault ground motions having fling step

Near-fault ground motions with long-period pulses have been identified as being critical in the design of structures. These motions, which have caused severe damage in recent disastrous earthquakes, are characterized by a short-duration impulsive motion that transmits large amounts of energy into the structures at the beginning of the earthquake. In nearly all of the past near-fault earthquakes, significant higher mode contributions have been evident in building structures near the fault rupture, resulting in the migration of dynamic demands (i.e. drifts) from the lower to the upper stories. Due to this, the static nonlinear pushover analysis (which utilizes a load pattern proportional to the shape of the fundamental mode of vibration) may not produce accurate results when used in the analysis of structures subjected to near-fault ground motions. The objective of this paper is to improve the accuracy of the pushover method in these situations by introducing a new load pattern into the common pushover procedure. Several pushover analyses are performed for six existing reinforced concrete buildings that possess a variety of natural periods. Then, a comparison is made between the pushover analyses' results (with four new load patterns) and those of FEMA (Federal Emergency Management Agency)-356 with reference to nonlinear dynamic time-history analyses. The comparison shows that, generally, the proposed pushover method yields better results than all FEMA-356 pushover analysis procedures for all investigated response quantities and is a closer match to the nonlinear time-history responses. In general, the method is able to reproduce the essential response features providing a reasonable measure of the likely contribution of higher modes in all phases of the response