• Structural Engineering and Mechanics
• /
• v.77 no.4
• /
• pp.463-472
• /
• 2021

Fully rigid floor diaphragm is one of the main assumptions that are widely used in common practices due to its simple application. However, determining the exact degree of diaphragms flexibility cannot be easily accomplished without finite element modeling, which is an expensive and time-consuming procedure. Therefore, it is always possible that apparently rigid diaphragms, based on prescriptive limitations of seismic codes, experience some degrees of flexibility during the earthquakes. Since diaphragm flexibility has more uncertainties in asymmetric-plan structures, this study focuses on errors resulting from probable floor diaphragm flexibility of torsionally restrained structures. The analytical models used in this study were single-story buildings with asymmetric plan and RC shear walls. Although floor system is not considered explicitly, a wide range of considered diaphragm flexibility, from fully rigid to quite flexible, allows the results to be generalizable to a lot of lateral load resisting systems as well as floor systems. It has been shown that in addition to previously known effects of diaphragm flexibility, presence of orthogonal side elements during design procedure with rigid diaphragm assumption and rapid reduction in their absorbed forces can also be an important source to increase errors due to flexibility. Accordingly, from the obtained results the authors suggest designers to consider the possibility of diaphragm flexibility and its adverse effects, especially in torsionally restrained systems in their common designs.

• Structural Engineering and Mechanics
• /
• v.81 no.3
• /
• pp.317-333
• /
• 2022

Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

• Steel and Composite Structures
• /
• v.47 no.2
• /
• pp.185-201
• /
• 2023

Despite the high lateral stiffness and strength of the Concentrically Braced Frame (CBF), due to the buckling of its diagonal members, it is not a suitable system in high seismic regions. Among the offered methods to overcome the shortcoming, utilizing a metallic damper is considered as an appropriate idea to enhance the behavior of Concentrically Braced Frames (CBFs). Therefore, in this paper, an innovative steel damper is proposed, which is investigated experimentally and numerically. Moreover, a parametrical study was carried out to evaluate the effect of the mechanism (shear, shear-flexural, and flexural) considering buckling mode (elastic, inelastic, and plastic) on the behavior of the damper. Besides, the necessary formulas based on the parametrical study were presented to predict the behavior of the damper that they showed good agreement with finite element (FE) results. Both experimental and numerical results confirmed that dampers with the shear mechanism in all buckling modes have a better performance than other dampers. Accordingly, the FE results indicated that the shear damper has greater ultimate strength than the flexural damper by 32%, 31%, and 56%, respectively, for plates with elastic, inelastic, and plastic buckling modes. Also, the shear damper has a greater stiffness than the flexural damper by 43%, 26%, and 53%, respectively, for dampers with elastic, inelastic, and plastic buckling modes.

• Steel and Composite Structures
• /
• v.45 no.3
• /
• pp.455-466
• /
• 2022

Despite the considerable lateral stiffness and strength of the Concentrically Braced Frame (CBF), it suffers from low ductility and low seismic dissipating energy capacity. The buckling of the diagonal members of the CBF systems under cyclic loading ended up to the shortcoming against seismic loading. Comprehensive researches have been performing to achieve helpful approaches to prevent the buckling of the diagonal member. Among the recommended ideas, metallic damper revealed a better success than other ideas to enhance the behavior of CBFs. While metallic dampers improve the behavior of the CBF system, they increase constructional costs. Therefore, in this paper, a new steel damper with flexural mechanism is proposed, which is investigated experimentally and numerically. Also, a parametrical revision was carried out to evaluate the effect of thickness, slenderness ratio, angle of the main plate, and height of the main plates on the proposed damper. For the parametrical study, 45 finite element models were analyzed and considered. Experimental results, as well as the numerical results, indicated that the proposed damper enjoys a stable hysteresis loop without any degradation up to a high rotation equal to around 31% that is significantly considerable. Moreover, it showed a suitable performance in case of ductility and energy dissipating. Besides, the necessary formulas to design the damper, the required relations were proposed to design the elements outside the damper to ensure the damper acts as a ductile fuse.

• Geomechanics and Engineering
• /
• v.36 no.3
• /
• pp.277-293
• /
• 2024

Shored Mechanically Stabilized Earth (SMSE) walls are types of soil retaining structures that increase soil stability under static and dynamic loads. The damage caused by an earthquake can be determined by evaluating the probabilistic seismic response of SMSE walls. This study aimed to assess the seismic performance of SMSE walls and provide fragility curves for evaluating failure levels. The generated fragility curves can help to improve the seismic performance of these walls through assessing and controlling variables like backfill surface settlement, lateral deformation of facing, and permanent relocation of the wall. A parametric study was performed based on a non-linear elastoplastic constitutive model known as the hardening soil model with small-strain stiffness, HSsmall. The analyses were conducted using PLAXIS 2D, a Finite Element Method (FEM) program, under plane-strain conditions to study the effect of the number of geogrid layers and the axial stiffness of geogrids on the performance of SMSE walls. In this study, three areas of damage (minor, moderate, and severe) were observed and, in all cases, the wall has not completely entered the stage of destruction. For the base model (Model A), at the highest ground acceleration coefficient (1 g), in the moderate damage state, the fragility probability was 76%. These values were 62%, and 54%, respectively, by increasing the number of geogrids (Model B) and increasing the geogrid stiffness (Model C). Meanwhile, the fragility values were 99%, 98%, and 97%, respectively in the case of minor damage. Notably, the probability of complete destruction was zero percent in all models.

• Structural Engineering and Mechanics
• /
• v.91 no.1
• /
• pp.49-61
• /
• 2024

In recent decades, the majority of studies have concentrated on the utilization of Steel Square Hollow Section (SHS) columns, with minimal attention given to reinforcing columns exhibiting inherent defects. This study addresses this gap by introducing initial vertical and horizontal defects at three distinct locations (top, middle, and bottom) and employing Carbon-FRP for reinforcement. The research investigates the dimensional and positional impacts of these defects on the axial behavior of SHS columns. A total of 29 samples, comprising 17 with defects, 11 strengthened, and 1 defect-free control, underwent examination. The study employed ABAQUS modeling and conducted experimental testing. Results revealed that defects located at different positions significantly diminished the load-bearing capacity and initial performance of the steel columns. Axial loading induced local buckling and lateral rupture, particularly at the defect side, in short columns. Notably, horizontal (across the column's width) and vertical (along the column's height) defects in the middle led to the most substantial reduction in strength and load-bearing capacity. The axial compressive failure increased with the length-to-width ratio of the defect. Moreover, the application of four carbon fiber layers to strengthen the steel columns resulted in increased Energy Dissipation and a delayed onset of local buckling in the face of axial ruptures.

• Anatomy and Cell Biology
• /
• v.57 no.1
• /
• pp.18-24
• /
• 2024

The origin and distribution of median nerve varies among the different individuals. The median nerve variations in axillary region were reported by many authors previously. Understanding of these variations is especially necessary for clinicians to prevent iatrogenic nerve damage. The current work aimed to evaluate the possible anatomical variations of median nerve in the axillary region in a sample of the Iranian cadavers (Shiraz, Fars). We dissected 26 upper limbs from 13 male cadavers to investigate the different variations of median and musculocutaneous nerves according to Venieratos and Anagnostopoulou classification. In 23.07% of specimens (n=6), the medial root united with 2 lateral roots and formed the median nerve proximal to the coracobrachialis muscle. In one case, a communicating branch separated from the musculocutaneous nerve distal to the coracobrachialis and connected to the median nerve in upper arm. Our results suggest that there are anatomical variations of the median nerve in terms of its origin and its communication with the musculocutaneous nerve in the population of southern Iran. The anatomical knowledge of the median nerve variations is important for clinicians to improve patient health outcome. Theses variations of the median nerve should be considered during surgical procedures of the axillary region and nerve block of the infra clavicular part of the brachial plexus.

• Archives of Reconstructive Microsurgery
• /
• v.9 no.2
• /
• pp.120-126
• /
• 2000

Microsurgical reconstruction of the hand demands recovery of the sensation of the reconstructed free flap as well as microsurgeon's intelligence, technique and experience. Even with adequate soft tissue coverage and skeletal mobility, an insensate hand is prone to further injury and is unlikely to be useful to the patients. Authors have performed 8 cases of neurosensory free flaps in the hand, 4 cases of wrap around, 3 dorsalis pedis and 1 lateral arm flap, from July 1992 through June 1999 and followed up average 4 years and 4 months. Wrap around flap was performed for reconstruction of 4 cases of thumb, repairing deep peroneal nerve and superficial radial nerve by epineurial neurorrhaphy, and followed up for average 3 years and 10 months and calculated 9mm in the static 2 point discrimination test. Dorsalis pedis flap were 3 cases for reconstruction of the ray amputation, extensor tendon exposure and wrist exposure. Deep peroneal nerve and branch of the ulnar nerve was repaired by epineurial neurorrhaphy calculating 6mm and superficial peroneal nerve and superficial radial nerve averaging 18mm in the static 2 point discrimination test for follow up average 2 years and 9 months. Lateral arm flap was 1 case for reconstruction of the ray amputation in the hand repairing posterior cutaneous nerve to the arm to the superficial radial nerve calculating 20mm for follow up 6 years and 8 months.

• Archives of Plastic Surgery
• /
• v.38 no.3
• /
• pp.228-234
• /
• 2011

Purpose: Reconstruction of chest wall has always been a challenging problem. Muscle flaps for chest wall reconstruction have been helpful in controling infection, filling dead space and covering the prosthetic material in this challenge. However, when we use muscle flaps, functional and cosmetic donor site morbidities could occur. The authors applied and revised various partial muscle flaps and combination use of them to cover the prosthetic material for the chest wall reconstruction and evaluated the usefulness of partial muscle flaps. Methods: This study included 7 patients who underwent chest wall reconstruction using partial muscle flap to cover prosthetic material from 2004 to 2008. The pectoralis major muscle was used in anterior 2/3 parts of it leaving lateral 1/3 parts of it. The anterior 2/3 parts of the pectoralis major muscle were used while lateral 1/3 parts were left. In case of the rectus abdominis muscle flap, we used upper half of it, or we dissected it around its origin and then advanced to cover the site. The latissimus dorsi muscle flap was elevated with lateral portion of it along the descending branch of the thoracodorsal artery. If single partial muscle flap could not cover whole prosthetic material, it would be covered with combination of various partial muscle flaps adjacent to the coverage site. Results: Flap coverage of the prosthetic material and chest wall reconstructions were successfully done. There occurred no immediate and delayed post operative complications such as surgical site infection, seroma, deformity of donor site and functional impairment. Conclusion: When we use the muscle flaps to cover prosthetic material for chest wall reconstruction, use of the partial muscle flaps could be a good way to reduce donor site morbidity. Combination of multiple partial flaps could be a valuable and good alternative way to overcome the disadvantages of partial muscle flaps such as limitation of volume and size as well as flap mobility.

• Journal of Bio-Environment Control
• /
• v.21 no.4
• /
• pp.392-397
• /
• 2012

In this study, we investigated the changes of growth characteristics, mineral and chlorophyll content of young leafy vegetable of Chinese toon grown under greenhouse and open fields. Results showed that growth of young leafy vegetable of Chinese toon was somewhat accelerated in greenhouse compared to the open field. In case of apical bud growth, several parameters such as plant height, number of branch, fresh weight and chlorophyll content showed similar tendency in both greenhouse and open field. In the changes of minerals, N content in apical buds recorded significant increase to 3.1 times compared to that of later buds. Its content was 1.2 times higher in greenhouse than that of open field. Mineral contents including P, Ca, Mg and Fe were significantly increased in greenhouse. Highest ascorbic acid content was observed in lateral buds grown in greenhouse and then it was followed such as lateral bud in open field, apical bud in open field, and apical bud in greenhouse, in turn. These results indicate that greenhouse culture could be applicable to new culture in order to produce young leafy vegetable of Chinese toon with high quality.