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CONTENTS
Volume 16, Number 3, September 2015
 

Abstract
1078 sets of mixtures in total that include fly ash, slag, and/or silica fume have been collected for prediction on concrete properties. A new database platform (Compos) has been developed, by which the stepwise multiple linear regression (SMLR) and BP artificial neural networks (BP ANNs) programs have been applied respectively to identify correlations between the concrete properties (strength, workability, and durability) and the dosage and/or quality of raw materials\'. The results showed obvious nonlinear relations so that forecasting by using nonlinear method has clearly higher accuracy than using linear method. The forecasting accuracy rises along with the increasing of age and the prediction on cubic compressive strength have the best results, because the minimum average relative error (MARE) for 60-day cubic compressive strength was less than 8%. The precision for forecasting of concrete workability takes the second place in which the MARE is less than 15%. Forecasting on concrete durability has the lowest accuracy as its MARE has even reached 30%. These conclusions have been certified in a ready-mixed concrete plant that the synthesized MARE of 7-day/28-day strength and initial slump is less than 8%. The parameters of BP ANNs and its conformation have been discussed as well in this study.

Key Words
concrete; mix proportioning; prediction; database; linear regression; artificial neural network

Address
Bin Chen, Qian Mao and Jingquan Gao, Institute of Water Resources and Environmental Engineering, Zhejiang University of Water Resources and Electric power, Xiasha University District, Hangzhou, China
Zhaoyuan Hu, Cixi Mingfeng Building Materials Co. Ltd, Ningbo, China

Abstract
In this study, a simple indeterminate strut-tie model which reflects complicated characteristics of the ultimate structural behavior of continuous reinforced concrete deep beams was proposed. In addition, the load distribution ratio, defined as the fraction of applied load transferred by a vertical tie of truss load transfer mechanism, was proposed to help structural designers perform the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie was introduced to ensure the ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete were reflected upon. To verify the appropriateness of the present study, the ultimate strength of 58 continuous reinforced concrete deep beams tested to shear failure was evaluated by the ACI 318M-11\'s strut-tie model approach associated with the presented indeterminate strut-tie model and load distribution ratio. The ultimate strength of the continuous deep beams was also estimated by the experimental shear equations, conventional design codes that were based on experimental and theoretical shear strength models, and current strut-tie model design codes. The validity of the proposed strut-tie model and load distribution ratio was examined through the comparison of the strength analysis results classified according to the primary design variables. The present study associated with the indeterminate strut-tie model and load distribution ratio evaluated the ultimate strength of the continuous deep beams fairly well compared with those by other approaches. In addition, the present approach reflected the effects of the primary design variables on the ultimate strength of the continuous deep beams consistently and reasonably. The present study may provide an opportunity to help structural designers conduct the rational and practical strut-tie model design of continuous deep beams.

Key Words
continuous deep beam; indeterminate strut-tie model; load distribution ratio; ultimate strength

Address
H.S. Chae and Y.M. Yun, Department of Civil Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 702-701, Republic of Korea

Abstract
Connections are the most important regions in a structural system especially for buildings in seismic zones. In R.C. structures due to large dimensions of members and lack of cognition of the stress distribution in a connection, reaching a comprehensive understanding of the connection behaviors becomes more complicated. The shear wall-to-floor slab connections in lateral load resisting systems have a potential weakness in transferring loads from slabs to shear walls which might change the path of load transformation to shear walls. This paper tries to investigate the effects of seismic load combinations on the behavior of slabs at their connection zones with the shear walls. These connection zones naturally are the most critical regions of the slabs in RC buildings. The investigation carried on in a simulated environment by considering three different structures with different shear wall layout. The final results of our study reveal that layout of shear walls in a building significantly affects the magnification of forces developed at the shear wall-floor slab connections.

Key Words
connection; floor slab; shear wall; FE method; seismic effects

Address
Mehdi Soleimani-Abiat: Department of Civil and Environmental Engineering, School of Engineering, Shiraz University, Fars 71348-51156, Iran ; Engineering Department, PAYSAZ Co., Ahvaz 61436-1570, Iran
Mohammad-Reza Banan: Department of Civil and Environmental Engineering, School of Engineering, Shiraz University, Fars 71348-51156, Iran

Abstract
Nowadays, fiber reinforced polymer (FRP) composites are widely used for rehabilitation, repair and strengthening of reinforced concrete (RC) structures. Also, recent advances in concrete technology have led to the production of high strength concrete, HSC. Such concrete due to its very high compression strength is less ductile; so in seismic areas, ductility is an important factor in design of HSC members (especially FRP strengthened members) under flexure. In this study, the Adaptive Neuro-Fuzzy Inference System (ANFIS) and multiple regression analysis are used to predict the curvature ductility factor of FRP strengthened reinforced HSC (RHSC) beams. Also, the effects of concrete strength, steel reinforcement ratio and externally reinforcement (FRP) stiffness on the complete moment-curvature behavior and the curvature ductility factor of the FRP strengthened RHSC beams are evaluated using the analytical approach. Results indicate that the predictions of ANFIS and multiple regression models for the curvature ductility factor are accurate to within -0.22% and 1.87% error for practical applications respectively. Finally, the effects of height to wide ratio (h/b) of the cross section on the proposed models are investigated.

Key Words
high strength concrete; FRP composites; multiple regression analysis; ANFIS; ductility

Address
H. Ebrahimpour Komleh and A.A. Maghsoudi: Civil Engineering Department, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, Iran

Abstract
Study on flexural retrofitting of RC beams using external bars with additional intermediate anchorages at soffit is reported in this paper. Effects of varying number of anchorages in the external bars at soffit were studied by finite element analysis using ANSYS 12.0 software. The results were also compared with available experimental results for beam with only two end anchorages. Two sets of reference and retrofitted beam specimens with two, three, four and five anchorages were analysed and the results are reported. FE modeling and non-linear analysis was carried out by discrete reinforcement modeling using Solid65, Solid45 and Link8 elements. Combin39 spring elements were used for modeling the frictional contact between the soffit and the external bars. The beam specimens were subjected to four-point bending and incremental loading was applied till failure. The entire process of modeling, application of incremental loading and generation of output in text and graphical format were carried out using ANSYS Parametric Design Language.

Key Words
external bars; anchorages; soffit; ANSYS

Address
G. Vasudevan: Perunthalaivar Kamarajar Institute of Engineering and Technology, Karaikal 609 603, India
S. Kothandaraman: Pondicherry Engineering College, Puducherry, 608 014, India

Abstract
The dams are huge structures storing a large amount of water and failures of them cause especially irreparable loss of lives during the earthquakes. They are named as a group of structures subjected to fluid-structure interaction. So, the response of the fluid and its hydrodynamic pressures on the dam should be reflected more accurately in the structural analyses to determine the real behavior as soon as possible. Different mathematical and analytical modelling approaches can be used to calculate the water hydrodynamic pressure effect on the dam body. In this paper, it is aimed to determine the dynamic response of concrete gravity dams using different water modelling approaches such as Westergaard, Lagrange and Euler. For this purpose, Sariyar concrete gravity dam located on the Sakarya River, which is 120km to the northeast of Ankara, is selected as a case study. Firstly, the main principals and basic formulation of all approaches are given. After, the finite element models of the dam are constituted considering dam-reservoir-foundation interaction using ANSYS software. To determine the structural response of the dam, the linear transient analyses are performed using 1992 Erzincan earthquake ground motion record. In the analyses, element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motions. Rayleigh damping is considered. At the end of the analyses, dynamic characteristics, maximum displacements, maximum-minimum principal stresses and maximum-minimum principal strains are attained and compared with each other for Westergaard, Lagrange and Euler approaches.

Key Words
concrete gravity dam; euler; dam-reservoir-foundation interaction; hydrodynamic pressure; lagrange; westergaard

Address
A.C. Altunisik and H. Sesli: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Abstract
This paper aims to study the local bond stress-slip behavior of reinforcing bars embedded in lightweight aggregate concrete (LWAC). The experimental variables of the local bond stress-slip tests include concrete strength (20, 40 and 60 MPa), deformed steel bar size (#4, #6 and #8) and coarse aggregate (normal weight aggregate, reservoir sludge lightweight aggregate and waterworks sludge lightweight aggregate). The test results show that the ultimate bond strength increased with the increase of concrete compressive strength. Moreover, the larger the rib height to the diameter ratio (h/db) of the deformed steel bars is, the greater the ultimate bond stress is. In addition, the suggestion value of the CEB-FIP Model Code to the LWAC specimen\'s ultimate bond stress is more conservative than that of the normal weight concrete.

Key Words
lightweight aggregate concrete; bond mechanisms; pull-out test

Address
Chao-Wei Tang: Department of Civil Engineering & Geomatics, Cheng Shiu University, No. 840, Chengcing Rd., Niaosong District, Kaohsiung City, Taiwan R.O.C.

Abstract
This paper presents a comprehensive work on determination of yield base shear coefficient and displacement ductility factor of three to eight story actual reinforced concrete buildings, instead of using generic frames. The building data is provided by a walkdown survey in different locations of the pilot areas. Very detailed three dimensional models of the selected buildings are generated by using the data provided in architectural and reinforcement projects. Capacity curves of the buildings are obtained from nonlinear static pushover analyses and each capacity curve is approximated with a bilinear curve. Characteristic points of capacity curve, the yield base shear capacity, the yield displacement and the ultimate displacement capacity, are determined. The calculated values of the yield base shear coefficients and the displacement ductility factors for directions into consideration are compared by those expected values given in different versions of Turkish Seismic Design Code. Although having sufficient lateral strength capacities, the deformation capacities of these typical mid-rise reinforced concrete buildings are found to be considerably low.

Key Words
existing reinforced concrete buildings; nonlinear static analysis; characteristic points of capacity curves; yield base shear coefficient; displacement ductility factor

Address
Taner Ucar, Department of Architecture, Dokuz Eylul University, Izmir, Turkey
Onur Merter and Mustafa Duzgun, Department of Civil Engineering, Dokuz Eylul University, Izmir, Turkey

Abstract
This study investigated particle expansion in basic oxygen furnace slag (BOF) and desulfurization slag (DSS) after heat curing by using the volume method. Concrete hydration was accelerated by heat curing. The compressive strength, ultrasonic pulse velocity, and resistivity of the concrete were analyzed. Maximum expansion occurred in the BOF and DSS samples containing 0.30-0.60 mm and 0.60-1.18 mm particles, respectively. Deterioration was more severe in the BOF samples. In the slag aggregates for the complete replacement of fine aggregate, severe fractures occurred in both the BOF and DSS samples. Scanning electron microscopy revealed excess CH after curing, which caused peripheral hydration products to become extruded, resulting in fracture.

Key Words
basic oxygen furnace slag (BOF); desulfurization slag (DSS); aggregate particle size; heat curing; expansion effect

Address
Chun-Ya Shu and Wen-Ten Kuo: Department of Civil Engineering, National Kaohsiung University of Applied Sciences, No. 415, Chien-Kung Rd., Sanmin District, Kaohsiung 80778, Taiwan, R.O.C.


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