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CONTENTS
Volume 8, Number 3, November 2019
 

Abstract
Progressive collapse is one of the factors which if not predicted at the time of structure plan; its occurrence will lead to catastrophic damages. Through having a glance over important structures chronicles in the world, we will notice that the reason of their collapse is a minor damage in structure caused by an accident like a terrorist attack, smashing a vehicle, fire, gas explosion, construction flaws and its expanding. Progressive collapse includes expanding rudimentary rupture from one part to another which leads to total collapse of a structure or a major part it. This study examines the progressive collapse of a 5-story concrete building with three column eliminating scenarios, including the removal of the corner, side and middle columns with the ABAQUS software. Then the beams and the bottom of the concrete slab were reinforced by (reinforcement of carbon fiber reinforced polymer) FRP and then the structure was re-analyzed. The results of the analysis show that the reinforcement of carbon fiber reinforced polymer sheets is one of the effective ways to rehabilitate and reduce the progressive collapse in concrete structures.

Key Words
progressive collapse; concrete frame; column elimination; reinforcement; FRP

Address
J. Esfandiari and M.K. Latifi: Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran

Abstract
This article presents a comparative study of the effect of steel layouts on the seismic behavior of transition steelconcrete composite connections, both experimental and analytical investigations of concrete filled steel tube-reinforced concrete (CFST-RC) and steel reinforecd concrete-reinforced concrete (SRC-RC) structures were conducted. The steel-concrete composite connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four full-scale connections extracted from a real project engineering with different levels of axial force. The effect of steel layouts on the mechanical behavior of the transition connections was evaluated by failure modes, hysteretic behavior, backbone curves, displacement ductility, energy dissipation capacity and stiffness degradation. Test results showed that different steel layouts led to significantly different failure modes. For CFST-RC transition specimens, the circular cracks of the concrete at the RC column base was followed by steel yielding at the bottom of the CFST column. While uncoordinated deformation could be observed between SRC and RC columns in SRC-RC transition specimens, the crushing and peeling damage of unconfined concrete at the SRC column base was more serious. The existences of I-shape steel and steel tube avoided the pinching phenomenon on the hysteresis curve, which was different from the hysteresis curve of the general reinforced concrete column. The hysteresis loops were spindle-shaped, indicating excellent seismic performance for these transition composite connections. The average values of equivalent viscous damping coefficients of the four specimens are 0.123, 0.186 and 0.304 corresponding to the yielding point, peak point and ultimate point, respectively. Those values demonstrate that the transition steel-concrete composite connections have great energy dissipating capacity. Based on the experimental research, a high-fidelity ABAQUS model was established to further study the influence of concrete strength, steel grade and longitudinal reinforcement ratio on the mechanical behavior of transition composite connections.

Key Words
steel layout; transition composite connections; concrete filled steel tube; steel reinforced concrete; axial compression ratio

Address
Liangjie Qi: Department of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an 710055, China; Disaster Prevention Research Institute, Kyoto University, Uji 611011, Japan
Jianyang Xue and Lei Zhai: Department of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an 710055, China

Abstract
Torsional behaviors of beams are investigated for the web reinforcement and the concrete type. Eight beams with self-compacting concrete (SCC) and twelve beams with conventional concrete (CC) were manufactured and tested. All the models manufactured as the 250x300x1500 mm were tested according to relevant standards. Two concrete types, CC and SCC were designed for 20 and 40 MPa compressive strength. From the point of web reinforcement, the web spacing was chosen as 80 and 100 mm. The rotation angles of the concrete beams subjected to pure torsional moment as well as the cracks occurring in the beams, the ultimate and critical torsional moments were observed. Moreover, the ultimate torsional moments obtained experimentally were compared with the values evaluated theoretically according to some relevant standards and theories. The closest estimations were observed for the skew-bending theory and the Australian Standard.

Key Words
reinforced concrete; self-compacting concrete; torsion; rotation capacity; ductility

Address
Abdulkadir C. Aydin and Baris Bayrak: Department of Civil Engineering, Faculty of Engineering, Ataturk University, 25240, Erzurum, Turkey

Abstract
High performance sandcretes (HPS) are new concretes characterized by particles having a diameter less than 5 mm, as well as very high mechanical strength and durability. This work consists in finding solutions to make sandcretes with good physico-mechanical and durability properties for this new generation of micro-concrete. However, upgrading ordinary sandcrete into high performance sandcrete (HPS) requires a thorough study of formulation parameters (equivalent water/binder ratio, type of cement and its dosage, kind and amount of super plasticizer, and gravel/sand ratio). This research study concerns the formulation, characterization and durability, in a sulphate environment, of a high performance sandcrete (HPS), made from local materials. The obtained results show that the rheological properties of fresh concrete and mechanical strength differ with the mineralogy, density and grain size distribution of sands and silica fume used.

Key Words
HPS; additive; sulphate environment; mechanical strength; durability

Address
Dalila Benamara: Civil Engineering Laboratory, Ziane Achour University, BP 3117, 17000 Djelfa, Algeria
Nadia Tebbal: Institute of Technical Urban Management, Geomaterials Development Laboratory, University of M\'sila, Algeria
Zine El Abidine Rahmouni: Geomaterials Development Laboratory, Civil Engineering Department, Faculty of Technology, M\'sila University, M\'sila, 28000, Algeria

Abstract
Application of nanotechnology can be used to tailor made cementitious composites owing to small dimension and physical behaviour of resulting hydration products. Because of high aspect ratio and extremely high strength, carbon nanotubes (CNTs) are perfect reinforcing materials. Hence, there is a great prospect to use CNTs in developing new generation cementitious materials. In the present paper, a parametric study has been conducted on cementitious composites reinforced by two types of multi walled carbon nanotubes (MWCNTs) designated as Type I CNT (10-20 nm outer dia.) and Type II CNT (30-50 nm outer dia.) with various concentrations ranging from 0.1% to 0.5% by weight of cement. To evaluate important properties such as flexural strength, strain to failure, elastic modulus and modulus of toughness of the CNT admixed specimens at different curing periods, flexural bending tests were performed. Results show that composites with Type II CNTs gave more strength as compared to Type I CNTs. The highest increase in strength (flexural and compressive) is of the order of 22% and 33%, respectively, compared to control samples. Modulus of toughness at 28 days showed highest improvement of 265% for Type II 0.3% CNT composites. It is obvious that an optimum percentage of CNT could exists for composites to achieve suitable reinforcement behaviour and desired strength properties. Based on the parametric study, a tentative optimum CNT concentration (0.3% by weight of cement) has been proposed. Scanning electron microscope image shows perfect crack bridging mechanism; several of the CNTs were shown to act as crack arrestors across fine cracks along with some CNTs breakage.

Key Words
carbon nano tubes; nano materials; nanotechnology; flexural strength; toughness; ductility

Address
Mohd Moonis Zaheer, Mohd Shamsuddin Jafri and Ravi Sharma: Department of Civil Engineering, Z.H. College of Eng. & Tech., AMU Aligarh-202002, India

Abstract
This paper presents the mechanical and microstructural properties of the geopolymer paste which was developed by utilizing the industrial by-products, rice husk ash (RHA) and ultra-fine slag. Ultra-fine slag particles with average particle size in the range of 4 to 5 microns. RHA is partially replaced with ultra-fine slag at different levels of 0 to 50%. Sodium silicate to sodium hydroxide ratio of 1.0 and alkaline liquid to binder (AL/B) ratio of 0.60 is taken. Setting time, compressive, flexural strengths were studied up to the age of 90 days with different concentrations of NaOH. The microstructure of the hybrid geopolymer paste was studied by performing the SEM, EDS, and XRD on the broken samples. RHA based geopolymer paste blended with ultrafine slag resulted in high compressive and flexural strengths and increased setting times of the paste. Strength increased with the increase in NaOH concentration at all ages. The ultra-small particles of the slag acted as a micro-filler into the paste and enhanced the properties by improving the CASH, NASH, and CSH. The maximum compressive strength of 70MPa was achieved at 30% slag content with 16M NaOH. The results of XRD, SEM, and EDS at 30% replacement of RHA with ultra-fine slag densified the paste microstructure.

Key Words
geopolymer; ultra-fine slag; rice husk ash; strength; setting time

Address
Parveen: Department of Civil Engineering, DCRUST Murthal, Haryana, India
Bharat Bhushan Jindal: School of Civil Engineering, Shri Mata Vaishno Devi University, Katra, J & K, India
M. Talha Junaid: Civil & Environmental Engineering Department, University of Sharjah, Sharjah, United Arab Emirates
Saloni: Department of Civil Engineering, DCRUST Murthal, Haryana, India

Abstract
Although applying self-consolidating concrete (SCC) in many modern structures is an inevitable fact, the high consumption of cement in its mixing designs has led to increased production costs and adverse environmental effects. In order to find economically viable sources with environmentally friendly features, natural pozzolan pumice and blast furnace slag in 10-50% of replacement binary designs have been investigated for experiments on the properties of fresh concrete, mechanical properties, and durability. As a natural pozzolan, pumice does not require advanced equipment to prepare for consumption and only needs to be powdered. Pumice has been the main focus of this research because of simple preparation. Also to validate the results, in addition to the control specimens of each design, fly ash as a known powder has been evaluated. Moreover, ternary mixes of pumice and silica fume were investigated to enhance the obtained results of binary mixes. It was concluded that pumice and slag powders indicated favorable performance in the high percentage of replacement.

Key Words
self-consolidating concrete; pumice powder; slag; silica fume; binary and ternary scheme

Address
Mahdi Shariati: Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam
Shervin Rafiei: Department of Construction Engineering and Management, Amirkabir University of Technology, Tehran, Iran
Peyman Mehrabi: Department of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran
Yousef Zandi: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Rouhollah Fooladvand: Department of Civil Engineering, Qeshm International Branch, Islamic Azad University, Qeshm, Iran
Behnam Gharehaghaj: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Ali Shariati: Division of Computational Mathematics and Engineering, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam; Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam
Nguyen Thoi Trung: Division of Computational Mathematics and Engineering, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam; Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam
Musab N.A. Salih: School of civil engineering, Faculty of engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia
Shek Poi-Ngian: Construction Research Center (CRC), Institute for Smart Infrastructure & Innovative Construction (ISIIC), School of Civil Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia

Abstract
Substitution of natural fine aggregates with industrial by-products like precious slag balls (PS Balls) offers various advantages like technical, economic and environmental which are very important in the present era of sustainability in construction industry. PS balls are manufactured by subjecting steel slag to slag atomizing Technology (SAT) which imparts them the desirable characteristics of fine aggregates. The main objective of this research paper is to assess the feasibility of producing good quality concrete by using PS balls, to identify the potential benefits by their incorporation and to provide solution for increasing their utilization in concrete applications. The study investigates the effect of PS balls as partial replacement of fine aggregates in various percentages (20%, 40%, 60%, 80% and 100%) on mechanical properties of concrete such as compressive strength, splitting tensile strength, and flexural strength. The optimum mix was found to be at 40% replacement of PS balls with maximum strength of 62.89 MPa at 28 days curing. Permeability of concrete was performed and it resulted in a more durable concrete with replacement of PS balls at 40% and 100% as fine aggregates. These two specific values were considered as optimum replacement is 40% and also the maximum possible replacement is 100%. Scanning electron microscope (SEM) analysis was done and it was found that the PS balls in concrete were unaffected and with optimum percentage of PS balls as fine aggregates in concrete resulted in good strength and less cracks. Hence, it is possible to produce good workable concrete with low water to cement ratio and higher strength concrete by incorporating PS balls.

Key Words
precious slag balls; concrete; sustainability; fine aggregates; durability

Address
S. Sharath: Department of Mining Engineering, National Institute of Technology Karnataka, Surathkal, Srinivasnagar P.O. Mangalore-575025, India
B.C. Gayana: Department of Mining Engineering, National Institute of Technology Karnataka, Surathkal, Srinivasnagar P.O. Mangalore-575025, India
Krishna R. Reddy: Department of Civil and Materials Engineering, University of Illinois at Chicago, USA
K. Ram Chandar: Department of Mining Engineering, National Institute of Technology Karnataka, Surathkal, Srinivasnagar P.O. Mangalore-575025, India


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