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CONTENTS
Volume 14, Number 4, October 2014
 

Abstract
In the existing method for analyzing the liquid tightness of the outer concrete tank in an emergency LNG spillage, the temperature variation over time inside the tank, and the concrete properties dependent on temperature and internal moisture content, have not been taken into account. In this study, the analyses for a typical LNG concrete tank subjected to thermal load due to spillage were performed with three different cases: the existing method was adopted in the first case, the transient temperature variation was considered in the second, and the temperature-moisture content dependent concrete properties were taken into account as well as the transient states of temperature in the third. The analysis results for deformation, compressive zone size, cracking, and stress of reinforcements were compared, and a discussion on the difference between the results obtained from the different analysis cases was made.

Key Words
NG; spillage, liquid tightness; crack, compression zone

Address
Jeong Su Lee and Seung Hee Kwon: Department of Civil and Environmental Engineering, Myongji University, Yongin, 449-728, Republic of Korea

Chan Kyu Park: Construction Technology Research Institute, Samsung C&T Corporation, Seocho-Gu, Seoul,
137-857, Republic of Korea

Yun Lee: epartment of Civil Engineering, Daejeon University, Daejeon, 300-716, Republic of Korea

Ji-Hoon Kim: Energy System Team, Samsung C&T Corporation, Seocho-Gu, Seoul, 137-956, Republic of Korea

Abstract
The aim of this study is to assess the structural performance of deteriorated reinforced concrete bridge piers, and to provide method for developing improved evaluation method. For a deteriorated bridge piers, once the cover spalls off and bond between the reinforcement and concrete has been lost, compressed reinforcements are likely to buckle. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze reinforced concrete structures. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. Advanced deteriorated material models are developed to predict behaviors of deteriorated reinforced concrete. The proposed numerical method for the structural performance assessment of deteriorated reinforced concrete bridge piers is verified by comparing it with reliable experimental results. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of deteriorated reinforced concrete bridge piers.

Key Words
structural performance; deteriorated; reinforced concrete; bridge piers; material models

Address
T.H. Kim: Construction Product Technology Team, Samsung Construction & Trading Corporation, 5th Fl.,
Daerung Gangnam Tower, 826-20 Yeoksam1-dong, Gangnam-gu, Seoul 135-935, Korea

Abstract
The poor seismic performance of reinforced concrete buildings during the latest earthquakes has become a serious issue in the building industry in Turkey. This case, designing new buildings without structural irregularities against earthquake loads reveals to be quite significant. This study mainly is focused on the effects of different torsional irregularities on construction costs and earthquakes performance of reinforced concrete buildings. In that respect, structural torsional irregularities are investigated based on the Turkish Earthquake Code. The study consists of major eight main parametric models. In this models consist of totally 49 models together with the variations in the number of storey. With this purpose, the earthquake performances and construction costs (especially steel quantities) of reinforced concrete buildings which having different structural torsional irregularities were obtained with the help of Sta4-CAD program. Each model has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis. The obtained results reveal that the model-1 which has lower torsional irregularity coefficient shows the best earthquake performance owing to its regular plan geometry. Also, economical comparisons on costs of the torsional irregularity are performed, and results-recommendations are given.

Key Words
construction cost; torsional irregularity; earthquake performance

Address
Şenol Gürsoy: Department of Civil Engineering, Karabük University, 78050 Karabük, Turkey

Abstract
In this study experimental result of a total of eight SCC and FRSCC slabs with the same cross-section were monitored for up to 240 days to measure the time-dependent development of cracking and deformations under service loads are presented. For this purpose, four SCC mixes are considered in the test program. This study aimed to compare SCC and FRSCC experimental results with conventional concrete experimental results. The steel strains within the high moment regions, the concrete surface strains at the tensile steel level, deflection at the mid-span, crack widths and crack spacing were recorded throughout the testing period. Experimental results show that hybrid fibre reinforced SCC slabs demonstrated minimum instantaneous and time-dependent crack widths and steel fibre reinforced SCC slabs presented minimum final deflection.

Key Words
self-compacting concrete; fibre-reinforced self-compacting concrete; crack control; time-dependent; flexural cracking; deformations

Address
Farhad Aslani: Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering, University of New South Wales, Australia

Shami Nejadi: School of Civil and Environmental Engineering, University of Technology Sydney, Australia

Bijan Samali: Institute for Infrastructure Engineering, University of Western Sydney, Australia

Abstract
To solve structural optimization problems, it is necessary to integrate a structural analysis package and an optimization package. There have been many packages that can be employed to analyze reinforced concrete plane frames. However, because most structural analysis packages suffer from closeness of systems, it is very difficult to integrate them with optimization packages. To overcome the difficulty, we proposed a possible alternative, DAMDO, which integrates Design, Analysis, Modeling, Definition, and Optimization phases into an integration environment as follows. (1) Design: first generate many possible structural design alternatives. Each design alternative consists of many design variables X. (2) Analysis: employ the structural analysis software to analyze all structural design alternatives to obtain their internal forces and displacements. They are the response variables Y. (3) Modeling: employ artificial neural networks to build the models Y=f(X) to obtain the relationship functions between the design variables X and the response variables Y. (4) Definition: employ the design variables X and the response variables Y to define the objective function and constraint functions. (5) Optimization: employ the optimization software to solve the optimization problem consisting of the objective function and the constraint functions to produce the optimum design variables. The RC frame optimization problem was examined to evaluate the DAMDO approach, and the empirical results showed that it can be solved by the approach.

Key Words
artificial neural networks; optimization; reinforced concrete; plane frame

Address
Chin-Sheng Kao and I-Cheng Yeh: Department of Civil Engineering, Tamkang University, No.151, Yingzhuan Rd., Tamsui Dist.,New Taipei City, Taiwan,The Republic of China

Abstract
The modelling approach in the case of connections in precast buildings is specific. The assembly of the constitutive parts of the connection requires the inclusion of contact definitions in the model. In addition, the material non-linearity including the influence of the spatial stress distribution should be taken into account where appropriate. Here a complex model of a beam-to-column dowel connection is presented. Experiments on the analysed connection were performed within the framework of the European project SAFECAST (Performance of Innovative Mechanical Connections in Precast Building Structures under Seismic Conditions). Several material and interaction parameters were investigated and the influence of each of them was evaluated. The set of parameters which gave the best match with the experiments was chosen.

Key Words
dowel connection; precast buildings; concrete modelling; CDP model; interaction modelling; failure mechanism; failure analysis

Address
Blaž Zoubek and Yasin Fahjan: University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova 2, 1000 Ljubljana, Slovenia

Matej Fischinger and Tatjana Isaković: Gebze Institute of Technology, Department of Earthquake and Structural Engineering, Istanbul Caddesi 141, 41400 Gebze, Turkey



Abstract
This paper presents the improvement of the EC-2 and EHE-08 shear strength formulations for concrete beams with shear reinforcement. The employed method is based on the genetic programming (GP) technique, which is configured to generate symbolic regression from a set of experimental data by considering the interactions among precision, accuracy, safety and simplicity. The size effect and the influence of the amount of shear reinforcement are examined. To develop and verify the models, 257 experimental tests on concrete beams from the literature are used. Three expressions of considerable simplicity, which significantly improve the shear strength prediction with respect to the formulations of the different studied codes, are proposed.

Key Words
artificial intelligence; genetic programming; reinforced concrete; shear strength; beams; stirrups; concrete codes

Address
Antoni Cladera: Department of Physics, University of the Balearic Islands, Ctra. Valldemossa km. 7.5, E-07122 Palma, Spain

Juan L. Pérez-Ordóñez: School of Building Engineering and Technical Architecture, University of A Coruña, Campus de Elviña, E-15192 La Coruña, Spain

Fernando Martínez-Abella: Department of Construction Technology, University of A Coruña, Campus de Elviña, E-15192 La Coruña, Spain


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