Techno Press
Tp_Editing System.E (TES.E)
Login Search


scs
 
CONTENTS
Volume 9, Number 5, October 2009
 

Abstract
Eight panel specimens were tested in one-way bending to study the behaviour and capacity of composite slab joists consisting of cold-formed steel C-sections and concrete. Various shear transfer mechanisms were implemented on the C-section flange embedded in the concrete to provide the longitudinal shear resistance. Results showed that all specimens reached serviceability limit state while in elastic range and failure was ductile. Shear transfer achieved for all specimens ranged from 42 to 99% of a full transfer while specimens employed with shear transfer enhancements showed a greater percentage and therefore a higher strength compared with those relying only on surface bond to resist shear. The implementation of pre-drilled holes on the embedded flange of the steel C-section was shown to be most effective. The correlation study between the push-out and panel specimens indicated that the calculated moment capacity based on shear transfer resistance obtained from push-out tests was, on average, 10% lower than the experimental ultimate capacity of the panel specimen.

Key Words
composite; cold-formed steel; light gage; shear transfer; flexural capacity.

Address
L. Shi; Dept of Civil Engineering, Univ. of New Brunswick, Fredericton, NB, Canada
Y. Liu; Dept of Civil and Resource Engineering, Dalhousie Univ., NS, Canada
J. L. Dawe; Dept of Civil Engineering, Univ. of New Brunswick, Fredericton, NB, Canada
P. Bischoff; Dept of Civil Engineering, Univ. of New Brunswick, Fredericton, NB, Canada

Abstract
Flange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. Reducing the flange-web slenderness ratios (FSR/WSR) of beams is the most effective way in mitigating local member buckling as stipulated in the latest seismic design specifications. However, existing steel moment frame buildings with beams that lack the adequate slenderness ratios set forth for new buildings are vulnerable to local member buckling and thereby system-wise instability prior to reaching the required plastic rotation capacities specified for new buildings. This paper presents results from a research study investigating the cyclic behavior of steel I-beams modified by a welded haunch at the bottom flange and reinforced with glass fiber reinforced polymers at the plastic hinge region. Cantilever I-sections with a triangular haunch at the bottom flange and flange slenderness ratios higher then those stipulated in current design specifications were analyzed under reversed cyclic loading. Beam sections with different depth/width and flange/web slenderness ratios (FSR/WSR) were considered. The effect of GFRP thickness, width, and length on stabilizing plastic local buckling was investigated. The FEA results revealed that the contribution of GFRP strips to mitigation of local buckling increases with increasing depth/width ratio and decreasing FSR and WSR. Provided that the interfacial shear strength of the steel/GFRP bond surface is at least 15 MPa, GFRP reinforcement can enable deep beams with FSR of 8-9 and WSR below 55 to maintain plastic rotations in the order of 0.02 radians without experiencing any local buckling.

Key Words
existing steel buildings; plastic local buckling; glass fiber reinforced polymers; stability.

Address
O. Ozgur Egilmez, Deniz Alkan and Timur Ozdemir; Dept. of Civil Engineering, Izmir Inst. of Technology, Izmir, 35430, Turkey

Abstract
This study proposes a system identification technique for a fiber-reinforced polymer deck with neural networks. Neural networks are trained for system identification and the identified structure gives training data in return. This process is repeated until the identified parameters converge. Hence, the proposed algorithm is called an iterative neural network scheme. The proposed algorithm also relies on recent developments in the experimental design of the response surface method. The proposed strategy is verified with known systems and applied to a fiber-reinforced polymer bridge deck with experimental data.

Key Words
fiber-reinforced polymer (FRP); system identification; neural network (NN); response surface method (RSM); iteration.

Address
Dookie Kim; Department of Civil and Environmental Engineering, Kunsan National University, Kunsan, Jeonbuk, Korea
Dong Hyawn Kim; 2Department of Coastal Construction Engineering, Kunsan National University, Kunsan, Jeonbuk, Korea
Jintao Cui; Department of Civil and Environmental Engineering, Kunsan National University, Kunsan, Jeonbuk, Korea
Hyeong Yeol Seo; Department of Civil and Environmental Engineering, Kunsan National University, Kunsan, Jeonbuk, Korea
Young Ho Lee; Structure Research Department, Korea Institute of Construction Technology, Goyang, Gyeonggi, Korea

Abstract
This study investigates the role of accidental torsion in seismic reliability assessment. The analyzed structures are regular 6-story and 20-story steel office buildings. The eccentricity in a floor plan was simulated by shifting the mass from the centroid by 5% of the dimension normal to earthquake shaking. The eccentricity along building heights was replicated by Latin hypercube sampling. The fragilities for immediate occupancy and life safety were evaluated using 0.7% and 2.5% inter-story drift limits. Two limit-state probabilities and the corresponding earthquake intensities were compared. The effect of ignoring accidental torsion and the use of code accidental eccentricity were also assessed. The results show that accidental torsion may influence differently the structural reliability and limit-state PGAs. In terms of structural reliability, significant differences in the probability of failure are obtained depending on whether accidental torsion is considered or not. In terms of limit-state PGAs, accidental torsion does not have a significant effect. In detail, ignoring accidental torsion leads to underestimates in low-rise buildings and at small drift limits. On the other hand, the use of code accidental eccentricity gives conservative estimates, especially in high-rise buildings at small drift limits.

Key Words
seismic performance; reliability-based assessment; fragility analysis; accidental torsion; mass eccentricity; steel buildings.

Address
Heui-Yung Chang; Department of Civil and Environmental Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Kaohsiung, 81148, Taiwan
Chu-Chieh Jay Lin; National Center for Research on Earthquake Engineering, National Applied Research Laboratories, No.200 Sec.3, ShinHai Rd., Taipei, 10668, Taiwan
Ker-Chun Lin; National Center for Research on Earthquake Engineering, National Applied Research Laboratories, No.200 Sec.3, ShinHai Rd., Taipei, 10668, Taiwan
Jung-Yu Chen; Department of Civil and Environmental Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Kaohsiung, 81148, Taiwan

Abstract
For the spatially coupled free vibration analysis of composite box beams resting on elastic foundation under the axial force, the exact solutions are presented by using the power series method based on the homogeneous form of simultaneous ordinary differential equations. The general vibrational theory for the composite box beam with arbitrary lamination is developed by introducing Vlasov

Key Words
free vibration; composite box beam; dynamic stiffness matrix; foundation effect.

Address
Nam-Il Kim; Department of Civil and Environmental Engineering, Myongji University, San 38-2, Nam-Dong, Yongin, Kyonggi-Do, 449-728, Korea


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com