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CONTENTS
Volume 20, Number 4, March20 2016
 

Abstract
Pile-to-pilecap connection performance is important as Integral abutment bridges (IABs) have no expansion joints and their flexible weak-axis oriented supporting piles take the role of the expansion joint. This connection may govern the bridge strength and the performance against various lateral loads. The intention of this study is to identify crack propagation patterns when the pile-to-pilecap connection is subjected to lateral loadings and to propose novel connections for improved performance under lateral loadings. In this study, eight different types of connections were developed and modeled, using Abaqus 6.12 to evaluate performances. Three types were developed by strengthening the connections using rebar or steel tube: (i) PennDOT specification; (ii) Spiral rebar; and (iii) HSS tube. Other types were developed by softening the connections using shape modifications: (i) cylindrical hole; (ii) reduced flange; (iii) removed flange; (iv) extended hole; and (v) slot hole connection types. The connections using the PennDOT specification, HSS tube, and cylindrical hole were shown to be ineffective in the prevention of cracks, resulting in lower structural capacities under the lateral load compared to other types. The other developed connections successfully delayed or arrested the concrete crack initiations and propagations. Among the successful connection types, the spiral rebar connection allowed a relatively larger reaction force, which can damage the superstructure of the IABs. Other softened connections performed better in terms of minimized reaction forces and crack prevention.

Key Words
pile-to-pilecap connection; crack control; FEM; integral bridge

Address
(1) Jaeha Lee, WooSeok Kim, Kyeongjin Kim:
Department of Civil Engineering, Korea Maritime and Ocean University, 727 Taejong-ro, Youngdo-gu, Busan, 606-791, Republic of Korea;
(2) Soobong Park, Yoseok Jeong:
Department of Civil Engineering, Chungnam National University, 99 Daehak-ro, Yusung-gu, Daejeon, 305-764, Republic of Korea.

Abstract
In this paper, a Performance Based Design (PBD) approach is validated for multi-storey concentrically braced frame (CBF) systems. Direct Displacement Based Design (DDBD) procedure is used and validated by designing 4- and 12-storey CBF buildings. Nonlinear time history analysis (NLTHA) is used to check the performance of the design methodology by employing different accelerograms having displacement spectra matching the design displacement spectrum. Displacements and drifts obtained from NLTHA are found to fall within the design displacement limits used in the DDBD procedure. In NLTHA, both tension and compression members are found to be resisting the base shear, Fb, not only the tension members as assumed in the design methodology and suggested by Eurocode 8. This is the reason that the total Fb in NLTHA is found to be greater than the design shear forces. Furthermore, it is found that the average of the maximum ductility values recorded from the time history analyses for the 4-and 12-storey buildings are close to the design ductility obtained from the DDBD methodology and ductility expressions established by several researchers. Moreover, the DDBD is compared to the Forced Based Design (FBD) methodology for CBFs. The comparison is carried out by designing 4 and 12-storey CBF buildings using both DDBD and FBD methodologies. The performance for both methodologies is verified using NLTHA. It is found that the Fb from FBD is larger than Fb obtained from DDBD. This leads to the use of larger sections for the structure designed by FBD to resist the lateral forces.

Key Words
codified approach; concentrically braced frames; design methodology; direct displacement based design; steel

Address
(1) Suhaib Salawdeh, Jamie Goggins:
Civil Engineering, College of Engineering & Informatics, National University of Ireland, Galway, Ireland;
(2) Suhaib Salawdeh, Jamie Goggins:
Centre for Marine and Renewable Energy Ireland (MaREI), Galway, Ireland;
(3) Jamie Goggins:
Ryan Institute, Galway, Ireland.

Abstract
One of the major components for performance based seismic design is accurate estimation of critical seismic demand parameters. While nonlinear seismic analysis is the most appropriate analysis method for estimation of seismic demand parameters, this method is very time consuming and complex. Single mode pushover analysis method, N2 method and multi-mode pushover analysis method, modal pushover analysis (MPA) are two nonlinear static methods that have recently been used for seismic performance evaluation of few lateral load-resisting systems. This paper further investigates the applicability of N2 and MPA methods for estimating the seismic demands of ductile unstiffened steel plate shear walls (SPSWs). Three different unstiffened SPSWs (4-, 8-, and 15-storey) designed according to capacity design approach were analysed under artificial and real ground motions for Vancouver. A comparison of seismic response quantities such as, height-wise distribution of floor displacements, storey drifts estimated using N2 and MPA methods with more accurate nonlinear seismic analysis indicates that both N2 and MPA procedures can reasonably estimates the peak top displacements for low-rise SPSW buildings. In addition, MPA procedure provides better predictions of inter-storey drifts for taller SPSW. The MPA procedure has been extended to provide better estimate of base shear of SPSW.

Key Words
nonlinear seismic analysis; N2 method; modal pushover analysis; finite element analysis

Address
Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Canada.

Abstract
In an actual design, none of the structures with shear behaviors will be designed for torsional moments. Any failure or damages to roofs, infills, shear walls, and braces caused by an earthquake, will inevitably result in relocation of center of mass and rigidity of the structure. With these changes, the dynamic characteristics of structure could be changed during an earthquake at any moment. The main objective of this paper is to obtain the relationship between time-varying eccentricity of load and corner lateral displacement. In this study, various methods have been used to determine the structural response for time-varying lateral corner displacement. As will be seen below, some of the structural calculation methods result in a significant deviation from the actual results, although these methods include the interaction effects of modes. Controlling the lateral displacement of structure can be performed in different ways such as, passive dampers, friction dampers, semi-active systems including the MR damper and active Systems. Selecting and locating these control systems is very important to bring the maximum safety with minimum cost into the structure. According to this study will be show the relation between the corner lateral displacements of structure and time-varying eccentricity by different kind of methods during an earthquake. This study will show that the response of the structure at the corners due to an earthquake can be very destructive and because of changing the eccentricity of load, calculating the maximum possible response of system can be carried out by this method. Finally, some kind of systems must be used for controlling these displacements. The results shows that, the CQC, DSC and exact methods is comply each other but the results of Vanmark method is not comfortable for these kind of buildings.

Key Words
torsional modes; shear modes; lateral displacement; eccentricity; earthquake; ABS, SRSS, CQC; vanmark; humar; Gupta and exact methods

Address
(1) Kambiz Takin, Masoud Nekooei:
Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;
(2) Behrokh H. Hashemi:
Structural Engineering Research Center (SERC), International Institute of Earthquake Engineering & Seismology (IIEES), Tehran, Iran.

Abstract
This research deals with the behavior of Composite Box Girder Bridges (CBGBs) subjected to environmental effects such as solar radiation, atmospheric temperature, and wind speed. It is based on temperature and thermal stress results, which were recorded hourly from a full-scale experimental CBGB segment and Finite Element (FE) thermal analysis. The Hemi-cube method was adopted to achieve the accuracy in temperature distributions and variations in a composition system during the daily environmental variations. Analytical findings were compared with the experimental measurements, and a good agreement was found. On the other hand, parametric investigations are carried out to investigate the effect of the cross-section geometry and orientation of the longitudinal axis of CBGB on the thermal response and stress distributions. Based upon individual parametric investigations, some remarks related to the thermal loading parameters were submitted. Additionally, some observations about the CBGB configurations were identified, which must be taken into account in the design process. Finally, this research indicates that the design temperature distribution with a uniform differential between the concrete slab and the steel girder is inappropriate for describing the thermal impacts in design objective.

Key Words
composite box girder bridge; environmental effects; temperature distribution; parametric thermal investigation

Address
Department of Civil Engineering, University of Gaziantep, 27310, Gaziantep, Turkey.

Abstract
Pre-stressing of existing structures using steel cables, FRP cables or FRP laminates has been successfully tried in the past. Retrofitting of beams using pre-stressed laminates does not utilize the full strength of the FRP due to de-bonding of the laminates before the fibre fracture. In the present study attempt has been made to overcome this problem by replacing the FRP laminates by the FRP sheets. In the present paper the effect of initial damage level and pre-stress level on strength, stiffness, cracking behaviour and failure mode of girders retrofitted using pre-stressed CFRP sheets has been studied. The results indicate that rehabilitation of initially damaged girders by bonding pre-stressed CFRP sheets improves the flexural behaviour of beams appreciably. However, it has been observed that with increase in pre-stressing force the load carrying capacity of the girders increases up to a particular level up to which the mode of failure is fibre fracture. Thereafter, the mode of failure shifts from fibre fracture to debonding and there is no appreciable increase in load carrying capacity with further increase in pre-stressing force.

Key Words
retrofitting; pre-stressed FRP sheets; girders; initial damage level; pre-stressing force level

Address
Department of Civil Engineering, Thapar University, Patiala, India.

Abstract
Cruciform sections are an appropriate option for columns of orthogonal moment resisting frames for equal bending strength and stiffness about two main axes and the implementation is easier for continuity plates. These columns consist of two I-shaped sections, so that one of them is cut out in middle and two generated T-shaped sections be welded into I-shaped profile. Furthermore, in steel moment frames, unbalance moment at the beamcolumn connection leads to shear deformation in panel zone. Most of the obtained relations for panel zone strength derived from experimental and analytical results are on I-shaped columns with almost thin flanges. In this paper, a parametric study has been carried out using Finite Element Method (FEM) with effective parameters at the panel zone behavior. These parameters consist of column flange thickness, column web thickness, and thickness of continuity plates. Additionally, a mathematical model has been suggested to determine strength of cruciform column panel zone and has been shown its accuracy and efficiency.

Key Words
panel zone; shear strength; cruciform column; FEM; beam-column connection

Address
(1) Hamed Saffari, Ali Fakhraddini:
Department of Civil Engineering, Shahid Bahonar University of Kerman, P.O. Box 76175-133, Kerman, Iran;
(2) Sina Sarfarazi:
Department of Civil Engineering, Graduate University of Advanced Technology, Kerman, Iran.

Abstract
The socket-spigot template supporting system is widely used in engineering applications in China. As a newer type of support structure, there has been growing research interest in its bearing capacity. In this paper, four vertical bearing capacity tests were carried out on the basic mechanical unit frame of a socket-spigot template supporting system. The first goal was to explore the influence of the node semi-rigid degree and the longitudinal spacing of the upright tube on the vertical bearing capacity. The second objective was to analyze the displacement trend and the failure mode during the loading process. This paper presents numerical analysis of the vertical bearing capacity of the unit frames using the finite element software ANSYS. It revealed the relationship between the node semi-rigid degree and the vertical bearing capacity, that the two-linear reinforcement model of elastic-plastic material can be used to analyze the socket-spigot template supporting system, and, through node entity model analysis, that the load transfer direction greatly influences the node bearing area. Finally, this paper indicates the results of on-site application performance experiments, shows that the supporting system has adequate bearing capacity and stability, and comments on the common work performance of a socket and fastener scaffold.

Key Words
socket-spigot template supporting system; basic mechanical unit frame; semi-rigid degree; application performance; numerical analysis

Address
College of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, P.R. China.

Abstract
Using the hyperbolic shear deformation plate model and including plate-foundation interaction (Winkler and Pasternak model), an analytical method in order to determine the deflection and stress distributions in simply supported rectangular functionally graded plates (FGP) subjected to a sinusoidal load, a temperature and moisture fields. The present theory exactly satisfies stress boundary conditions on the top and the bottom of the plate. No transversal shear correction factors are needed because a correct representation of the transversal shearing strain is given. Materials properties of the plate (elastic, thermal and moisture expansion coefficients) are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. Numerical examples are presented and discussed for verifying the accuracy of the present theory in predicting the bending response of FGM plates under sinusoidal load and a temperature field as well as moisture concentration. The effects of material properties, temperature, moisture, plate aspect ratio, side-to-thickness ratio, ratio of elastic coefficients (ceramic-metal) and three distributions for both temperature and moisture on deflections and stresses are investigated.

Key Words
FG plates; elastic foundation; hyperbolic shear deformation; hygro-thermal load

Address
(1) Imene Laoufi, Mohammed Ameur, Mohamed Zidi, El Abbes Adda Bedia, Abdelmoumen Anis Bousahla:
Laboratoire des Matériaux et Hydrologie, Université de Sidi Bel Abbes, BP 89 Cité Ben M'hidi 22000 Sidi Bel Abbes, Algérie;
(2) Mohammed Ameur:
Département de génie civil, Ecole Nationale Polytechnique d'Oran, Algéie;
(3) Mohamed Zidi, El Abbes Adda Bedia:
Département de génie civil, Faculté des Sciences de l'Ingénieur, Université Sidi Bel Abbes, Algérie.

Abstract
It is common practice to use Reduced Web Beam Sections (RWBS) in steel moment resisting frames. Perforation of beam web in these members may cause stress and strain concentration around the opening area and facilitate ductile fracture under cyclic loading. This paper presents a numerical study on the cyclic fracture of these structural components. The considered connections are configured as T-shaped assemblies with beams of elongated circular perforations. The failure of specimens under Ultra Low Cycle Fatigue (ULCF) condition is simulated using Cyclic Void Growth Model (CVGM) which is a micromechanics based fracture model. In each model, CVGM fracture index is calculated based on the stress and strain time histories and then models with different opening configurations are compared based on the calculated fracture index. In addition to the global models, sub-models with refined mesh are used to evaluate fracture index around the beam to column weldment. Modeling techniques are validated using data from previous experiments. Results show that as the perforation size increases, opening corners experience greater fracture index. This is while as the opening size increases the maximum observed fracture index at the connection welds decreases. However, the initiation of fracture at connection welds occurs at lower drift angles compared to opening corners. Finally, a probabilistic framework is applied to CVGM in order to account for the uncertainties existing in the prediction of ductile fracture and results are discussed.

Key Words
ultra low cycle fatigue; cyclic void growth model; perforated beams; fracture; finite element analysis

Address
Civil Engineering Department, Amirkabir University of Technology, Tehran, Iran.

Abstract
Ratcheting deformation of pressurized Z2CND18.12N stainless steel 90° elbow pipe with local wall thinning subjected to constant internal pressure and reversed bending was studied using finite element analysis. Chen-Jiao-Kim (CJK) kinematic hardening model, which was used to simulate ratcheting behavior of pressurized 90° elbow pipe with local wall thinning at extrados, flanks and intrados, was implemented into finite element software ANSYS. The local wall thinning was located at extrados, flanks and intrados of 90° elbow pipe, whose geometry was rectangular cross-section. The effect of depth, axial length and circumferential angle of local wall thinning at extrados, flanks and intrados on the ratcheting behaviors of 90° elbow pipe were studied in this paper. Threedimensional elastic-plastic analysis with Chen-Jiao-Kim (CJK) kinematic hardening model was carried out to evaluate structural ratcheting behaviors. The results indicated that ratcheting strain was generated mainly along the hoop direction, while axial ratcheting strain was relatively small.

Key Words
FEA; constitutive model; elbow pipe; ratcheting effect; local wall thinning; ANSYS

Address
(1) Xiaohui Chen:
School of Control Engineering, Northeastern University, Qinhuangdao 066004, China;
(2) Xiaohui Chen, Xu Chen:
School of Chemical Engineering and Technology, Tianjin University, 300072, China.

Abstract
The determination of the stress intensity factor at the crack tip is one of the most widely used methods to predict the fatigue life of aircraft structures. This prediction is more complicated for repaired cracks with bonded composite patch. This study is used to compute the stress intensity factor (SIF) and crack opening displacement (COD) for cracks repaired with single and double-sided composite patches. The effect of the presence of disbond region in adhesive at the crack was taken into consideration. The results show that there is a considerable reduction in the asymptotic value of the stress-intensity factors and the crack opening displacement at the crack tip. The use of a double-sided patch suppresses the bending effect due to the eccentricity of the patch on one side only.

Key Words
stress intensity factor (SIF); crack opening displacement (COD); crack; bonded composite repair; disbond

Address
(1) Aicha Benchiha, Kouider Madani:
LMPM, Department of Mechanical Engineering, University of Sidi Bel Abbes, Cité Ben M'hidi, Sidi Bel Abbes, Algeria;
(2) Sebastien Touzain, Xavier Feaugas:
La Rochelle University, Laboratoire des sciences pour l'ingénieur pour l'environnement (LASIE), La Rochelle, France;
(3) Mohan Ratwani:
R-Tec, Rolling Hills Estates, CA 90274, USA.


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