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CONTENTS
Volume 22, Number 5, November 2018
 

Abstract
One of the important factors is the infill walls in the change of the structural rigidity, ductility, dynamic and static characteristics of the structures. The infill walls are not generally included in numerical analysis of reinforced concrete (RC) structural system due to lack of suitable theory and the difficulty of calculating the recommended models. In seismic regions worldwide, the residential structures are generally RC buildings with infill wall. Therefore, understanding the contribution of the infill walls to seismic performance of buildings may have a vital importance. This paper investigates the effects of infill walls on seismic performance of the existing RC residential buildings by considering requirements of the Turkish Earthquake Code (TEC). Seismic performance levels of residential RC buildings with and without walls in high-hazard zones were determined according to the nonlinear procedure given in the code. Pushover curves were obtained by considering the effect of masonry infill walls on seismic performance of RC buildings. The analysis results showed that the infill walls beneficially effected to the rigidity, roof displacements and seismic performance of the building.

Key Words
seismic performance; existing RC buildings; infill wall

Address
Hakan Dilmac, Hamide Tekeli and Fuat Demir: Suleyman Demirel University, Department of Civil Engineering, Isparta, Turkey
Hakan Ulutas: Burdur Mehmet Akif Ersoy University, Department of Civil Engineering, Burdur, Turkey

Abstract
Concrete is one of the most widely used construction materials in the world. Producing economical and durable concrete is possible by employing pozzolanic materials. The aim of this study is to underline the possibility of the utilization of natural zeolite in producing concrete and investigate its effects basically on the strength and durability of concrete. In the production of concrete mixes, Portland cement was replaced by the natural zeolite at ratios of 0%, 10%, 15%, and 20% by weight. Concretes were produced with total binder contents of 300 kg/m3 and 400 kg/m3, but with a constant water to cement ratio of 0.60. In addition to compressive and flexural strength measurements, freeze-thaw and high temperature resistance measurements, rapid chloride permeability, and capillary water absorption tests were performed on the concrete mixes. Compared to the rest mixes, concrete mixes containing 10% zeolite yielded in with the highest compressive and flexural strengths. The rapid chloride permeability and the capillary measurements were decreased as the natural zeolite replacement was increased. Freeze-thaw resistance also improved significantly as the replacement ratio of zeolite was increased. Under the effect of elevated temperature, natural zeolite incorporated concretes with lower binder content yielded higher compressive strength. However, the compressive strengths of concretes with higher binder content after elevated temperature effect were found to be lower than the reference concrete.

Key Words
natural zeolite; strength; durability; freeze-thaw; elevated temperature; rapid chloride permeability; capillary water absorption; microstructure

Address
Memduh Nas and Sirin Kurbetci: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey

Abstract
In this paper, to access the suitability of recycled aggregate for structural applications, concrete strength i.e., compressive, tensile and flexural strength were evaluated and compared with those specimens made of natural aggregates. Test results indicated that 30 to 42% of the mentioned strength decreases. To study the performance of frame structures made of recycled aggregate concrete (RAC) two reinforced RAC frames were prepared and tested under monotonic loading. The joint regions of one of the RAC frame were casted with micro-concrete. A reference specimen was also prepared using natural aggregate concrete (NAC) and subjected to a similar loading condition. The RAC frame resulted in a brittle mode of failure as compared to NAC frame. However, the presence of a micro-concrete at the joint region of an RAC frame improved the damage tolerance and load resisting capacity. Seismic parameter such as energy dissipation, ductility and stiffness also improves. Conclusively, strengthening of joint region using micro-concrete is found to have a significant contribution in improving the seismic performance of an RAC frame.

Key Words
RAC frame; recycled aggregate; mechanical strength; micro-concrete; monotonic loading; seismic performance

Address
Comingstarful Marthong, Risukka N. Pyrbot, Stevenly L. Tron, Lam-I D. Mawroh, Md. Sakil A. Choudhury and Ganesh S. Bharti: Department of Civil Engineering, National Institute of Technology Meghalaya, Shillong-793003, India

Abstract
The Brazilian tensile strength of concrete samples is a key parameter in fracture mechanics since it may significantly change the quality of concrete materials and their mechanical behaviors. It is well known that porosity is one of the most often used physical indices to predict concrete mechanical properties. In the present work the influence of porosity shape on concrete tensile strength characteristics is studied, using a bonded particle model. Firstly numerical model was calibrated by Brazilian experimental results and uniaxial test out puts. Secondly, Brazilian models consisting various pore shapes were simulated and numerically tested at a constant speed of 0.016 mm/s. The results show that pore shape has important effects on the failure pattern. It is shown that the pore shape may play an important role in the cracks initiation and propagation during the loading process which in turn influence on the tensile strength of the concrete samples. It has also been shown that the pore size mainly affects the ratio of uniaxial compressive strength to that of the tensile one in the simulated material samples.

Key Words
Brazilian tensile strength; pore shape effect; simulation by PFC2D; concrete specimens

Address
Hadi Haeri: MOE Key Laboratory of Deep Underground Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Zheming Zhu: MOE Key Laboratory of Deep Underground Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China
Mohammad Fatehi Marji: Department of Mining Engineering, Yazd University, Yazd, Iran

Abstract
In this paper, a new hybrid fiber system (NHFS) is investigated for the application of slab. The steel fiber, polyvinyl alcohol (PVA) fiber and calcium carbonate (CaCO3) whisker is added to form NHFS. The four-point bending test is carried out on the flexural properties of slab with plain, steel fiber, traditional hybrid fiber system (THFS) and NHFS reinforced cementitious composites. The flexural behavior is evaluated by ASTM C1018-97, JCI-SF4 and post-crack strength (PCS) technique. The evaluation parameters of flexural toughness such as toughness index (TI), equivalent flexural strength (EFS) and PCS are determined. The size of slab specimens is 15 mm (thickness)x50 mm (width)x200 mm (length). The results show that adding CaCO3 whisker to THFS can significantly improve the flexural strength, TI, EFS, PCS of the slab. The empirical relation between reinforcing index (RIv) and flexural parameters show that flexural parameters of slabs increase first and then decrease; which indicates that optimum RIv values can be helpful in the considering the mix design of steel-PVA fibers-CaCO3 whisker composites for achieving the desired flexural-related properties. The scanning electron microscopy is performed to observe the micro-morphological characteristics of the fracture surface, which proved the positive hybrid effect among the different fibers in cementitious composites. The NHFS can arrest the generation and propagation of the crack from micro to macro level.

Key Words
new hybrid fiber system; slab; CaCO3 whisker; flexural toughness; reinforcing index; scanning electron microscop

Address
Mingli Cao, Chaopeng Xie, Li Li and Mehran Khan: School of Civil Engineering, Dalian University of Technology,
Linggong Road, Ganjingzi District, Dalian, People\'s Republic of China

Abstract
Due to the fact that the ratio of their height to their openings is very large compared to normal beams, there are difficulties in the design and analysis of deep beams, which differ in behavior. In this study, the optimum horizontal and vertical reinforcement diameters of 5 different beams were determined by using genetic algorithms (GA) due to the openness/height ratio (L/h), loading condition and the presence of spaces in the body. In this study, the effect of different mutation operators and improved double times sensitive mutation (DTM) operator on GA

Key Words
evolutionary algorithms; artificial intelligence; genetic algorithms; mutation operator; deep beam

Address
Mustafa Kaya: Faculty of Engineering, Aksaray University, Aksaray, Turkey


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