Existing reinforced concrete (RC) columns may be structurally deficient due to variety of reasons such as improper transverse reinforcement, flaws in structural design, insufficient load carrying capacity, etc. Fiber reinforced polymer (FRP) is a new generation of materials which illustrates in order to enhance concrete compressive strength and ductility. Among the FRP types, Carbon fiber reinforced polymer (CFRP) is more common. CFRP can be effectively used for strengthening and confinement the deficient RC columns. This research conducts to evaluate the behavior of this fiber in improvement of aforementioned quantities. In this investigation, three categories of compressive strength of concrete were selected. The samples were warped with 0, 1, 3, and 5 layers of CFRP were subjected under stress-strain tests. The results display that carbon fiber is more effective in enhancing the compressive strength and ductility. Fiber performance is more effective on low-strength concretes, and its effective role decreases with increasing the number of layers. Manuscript profile

In this article, we tried to emphasis in how the range of torsionally stiff and flexible single story buildings works. The designed base was according to provisions of the Canadian standard, 2005 NBCC. The behavior of nonlinear dynamic time history of eight building models subjected to seven horizontal bi-directional ground motions compatible with design spectra are investigated. These models cover a wide range of torsionally stiff to flexible buildings. Response parameters are element ductility demand and building story drift ratio. These criteria are appropriate indices for structural and nonstructural damages, respectively. This investigation shows that the linear static and dynamic analysis of building codes such as the 2005 NBCC and its framework are not generally adequate for structures with extremely low torsional stiffness. The provisions in mentioned codes and its framework are able to limit ductility demand, but they do not limit drift to the allowable level for extremely torsional structure. Manuscript profile

This paper examines differences in performances of a range of torsionally stiff and flexible single story buildings designed with the provisions of Iranian Standard 2800. Seismic nonlinear dynamic time history behavior of eight building models subjected to seven horizontal bi-directional design spectra compatible ground motions are investigated. These models cover a wide range of very torsionally stiff to very flexible buildings. Response parameters are element ductility demand and building story drift ratio. These criteria are appropriate indices for structural and nonstructural damages, respectively. This investigation shows that the linear static analysis of building code such as Iranian Standard 2800 is not generally adequate for structures with very low torsional stiffness. Manuscript profile

Determination the optimal mix design plays an important role in order to gain the maximum characteristic strength. This research was conducted as a case study for Manjil tunnel project located in Qazvin-Rasht highway. For this purpose, 18 concrete mix designs were prepared at the study phase of the project with specifications such as conventional water-to-cement ratios of 0.4, 0.5 and 0.6, the use of two generations of new and old conventional superplasticizer in Iran (naphthalene sulphonate and polycarboxylate ether types, respectively) with cement weight percentages of 0.2, 0.4 and 0.6. Superplasticizers are used to increase the fluidity of concrete without adding excess water. The naphthalene sulphonate is a polymeric molecule formed by condensation of naphthalene sulfonic acid and formaldehyde, in which the hydrophilic groups are mainly sulfonic groups. It has been demonstrated that polycarboxylate ether can mitigate plastic shrinkage of matrix because of the reduction of the build-up rate of capillary pressure by polycarboxylate ether. Finally, the optimal water-to-cement ratio and superplasticizer weight percentage were determined. Concrete mix designs with different ages of curing were made (0, 3, 7, 14 and 28 days). Manuscript profile

هدف از اجرای تحقیق حاضر، تعیین تأثیر روش یادگیری معکوس بر یادگیری خود راهبر در درس کارآفرینی بوده است. این پژوهش نیمه آزمایشی از نوع پیش آزمون-پس آزمون با گروه کنترل بوده است. جامعه‌ی آماری این تحقیق ، شامل کلیه‌ی دانشجویان در دوره‌ی کارشناسی رشته‌ی حسابداری دانشگاه آزاد اسلامی واحد یادگار امام (ره) تهران در سال تحصیلی 97-1396 بوده است. برای نمونه‌گیری، از میان دانشجویان دوره‌ی کارشناسی رشته‌ی حسابداری دانشگاه آزاد اسلامی واحد یادگار امام 150 نفر به‌صورت تصادفی انتخاب شده است. سپس قبل از اجرای آموزش درس کارآفرینی به روش یادگیری معکوس و پس از آموزش، پرسشنامه‌ی یادگیری خود راهبر ویلیامسون (2007) که در 5 مؤلفه و 60 گویه (تفکیک مؤلفه‌ها عبارت است از :آگاهی، راهبردهای یادگیری ،فعالیت‌های یادگیری، ارزشیابی و مهارت‌های بین فردی) ساخته شده است بر روی همه آن‌ها اجرا شده است. به‌طورکلی نتایج تحقیق نشان می‌دهد، بین میانگین‌های نمرات گروه آزمایش و گروه گواه در خصوص تأثیر روش یادگیری معکوس بر یادگیری خود راهبر دانشجویان در درس کارآفرینی در مرحله پس‌آزمون تفاوت معناداری وجود دارد ( 0.01p<). Manuscript profile