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CONTENTS
Volume 19, Number 2, August 2015
 

Abstract
This study presents conceptual information of newly optimized shapes and connectivity of the so-called outrigger truss system for modern tall buildings that resists lateral loads induced by wind and earthquake forces. In practice, the outrigger truss consists of triangular or Vierendeel types to stiffen tall buildings, and the decision of outrigger design has been qualitatively achieved by only engineers\' experience and intuition, including information of structural behaviors, although outrigger shapes and the member\'s connectivity absolutely affect building stiffness, the input of material, construction ability and so on. Therefore the design of outrigger trusses needs to be measured and determined according to scientific proofs like reliable optimal design tools. In this study, at first the shape and connectivity of an outrigger truss system are visually evaluated by using a conceptual design tool of the classical topology optimization method, and then are quantitatively investigated with respect to a structural safety as stiffness, an economical aspect as material quantity, and construction characteristics as the number of member connection. Numerical applications are studied to verify the effectiveness of the proposed design process to generate a new shape and connectivity of the outrigger for both static and dynamic responses.

Key Words
conceptual design information; topology optimization; shape; topology; structural layout; outrigger

Address
(1) Dongkyu Lee, Jaehong Lee, Kihak Lee:
Department of Architectural Engineering, Sejong University, Seoul, 143-747, Korea;
(2) Soomi Shin:
Research Institute of Industrial Technology, Pusan National University, Busan, 609-735, Korea.

Abstract
Previous research has shown that steel plate shear walls (SPSWs) are efficient lateral force-resisting systems against both wind and seismic loads. A properly designed SPSW can have high initial stiffness, strength, and energy absorption capacity as well as superior ductility. SPSWs have been commonly designed with unstiffened and stiffened infill plates based on economical and performance considerations. Recent introduction and application of corrugated plates with advantageous structural features has motivated the researchers to consider the employment of such elements in stiffened SPSWs with the aim of lowering the high construction cost of such high-performing systems. On this basis, this paper presents results from a numerical investigation of the hysteretic performance of SPSWs with trapezoidally corrugated infill plates. Finite element cyclic analyses are conducted on a series of flat- and corrugated-web SPSWs to examine the effects of web-plate thickness, corrugation angle, and number of corrugation half-waves on the hysteretic performance of such structural systems. Results of the parametric studies are indicative of effectiveness of increasing of the three aforementioned web-plate geometrical and corrugation parameters in improving the cyclic response and energy absorption capacity of SPSWs with trapezoidally corrugated infill plates. Increasing of the web-plate thickness and number of corrugation half-waves are found to be the most and the least effective in adjusting the hysteretic performance of such promising lateral force-resisting systems, respectively. Findings of this study also show that optimal selection of the web-plate thickness, corrugation angle, and number of corrugation half-waves along with proper design of the boundary frame members can result in high stiffness, strength, and cyclic performances of such corrugated-web SPSWs.

Key Words
steel plate shear wall; trapezoidally corrugated web-plate; numerical simulation; cyclic behavior; energy dissipation capacity

Address
(1) Hamed Kalali, Farshid J. Alaee:
Department of Civil and Architectural Engineering, University of Shahrood, Shahrood, Iran;
(2) Mohammad Hajsadeghi:
School of Engineering Sciences, University of Liverpool, Liverpool L69 3BX, UK; and Civil Engineering Department, Xian Jiaotong-Liverpool University, Suzhou Industrial Park, Jiangsu Province, China;
(3) Tadeh Zirakian:
Department of Civil Engineering and Construction Management, California State University, Northridge, CA, USA.

Abstract
Interaction between the external thin-walled steel tube and the internal concrete core significantly increases the bending resistance of composite beams and beam-columns in comparison with the steel or concrete members. There is presented a developed method for design of hollow and solid concrete-filled steel tubular beams based on test data, which gives better agreement with test results than EC4 because its limitation to take an increase in strength of concrete caused by confinement contradicts the recommendation of 6.7.2(4) that full composite action up to failure may be assumed between steel and concrete components of the member. Good agreement between the results of carried out experimental, numerical and theoretical investigations allows recommending the proposed method to use in design practice.

Key Words
composite steel-concrete beams; concrete-filled circular steel tubes; hollow and solid concrete cores; design based on test data

Address
Department of Steel and Timber Structures, 2Department of Structural Mechanics, Vilnius Gediminas Technical University, 11 Sauletekio ave, Vilnius 10223, Lithuania.

Abstract
A convenient procedure for seismic retrofit of existing buildings is to use passive control methods, like using friction dampers in steel frames with bracing systems. In this method, reduction of seismic demand and increase of ductility generally improve seismic performance of the structures. Some of its advantages are development of a stable rectangular hysteresis loop and independence on environmental conditions such as temperature and loading rate. In addition to friction dampers, masonry-infill panels improve the seismic resistance of steel structures by increasing lateral strength and stiffness and reducing story drifts. In this study, the effect of masonry-infill panels on seismic performance of a three-span four-story steel frame with Pall friction dampers is investigated. The results show that friction dampers in the steel frame increase the ductility and decrease the drift (to less than 1%). The infill panels fulfill their function during the imposed drift and increase structural strength. It can be concluded that infill panels together with friction dampers, reduced structural dynamic response. These infill panels dissipated input earthquake energy from 4% to 10%, depending on their thickness.

Key Words
masonry-infill panel; seismic retrofitting; pall friction damper; earthquake energy; structural analysis

Address
(1) Seyed Mehdi Zahrai:
Center of excellence for Engineering and Management of civil Infrastructures, School of Civil Engineering, the University of Tehran, Tehran, Iran;
(2) Alireza Moradi:
Department of Civil Engineering, Islamic Azad University, Central Tehran Branch, Tehran, Iran;
(3) Mohammadreza Moradi:
Department of Civil and Environmental Engineering, Old Dominion University, Norfolk, VA, 23529, USA.

Abstract
A numerical procedure is presented that provides ultimate curvature and moment domains for composite rectangular and circular cross-sections of reinforced concrete columns with or without an embedded steel section subjected to combined axial loading and biaxial bending. The stress resultants for the concrete and reinforcement bars are calculated using fiber analysis and the stress resultants for the encased structural steel are evaluated using an exact integration of the stress-strain curve over the area of the steel section. A dimensionless formula is proposed that can be used for any section with similar normalized geometric and mechanical parameters. The contribution of each material to the bearing capacity of a section (resistance load and moments) is calculated separately so that the influence of each geometric or mechanical parameter on the bearing capacity can be investigated separately.

Key Words
biaxial bending; composite columns; dimensionless formulation; rectangular and circular cross-sections; ultimate strength analysis

Address
Department of Civil Engineering, Faculty of Engineering, Kharazmi University, No. 43, Dr. Mofatteh Ave., Tehran 15719-14911, Iran.

Abstract
This paper presents a new algorithm to find the optimal distribution of steel diagonal braces (SDB) using artificial bee colony optimization technique. The four different objective functions are employed based on the transfer function amplitude of; the top displacement, the top absolute acceleration, the base shear and the base moment. The stiffness parameter of SDB at each floor level is taken into account as design variables and the sum of the stiffness parameter of the SDB is accepted as an active constraint. An optimization algorithm based on the Artificial Bee Colony (ABC) algorithm is proposed to minimize the objective functions. The proposed ABC algorithm is applied to determine the optimal SDB distribution for planar buildings in order to rehabilitate existing planar steel buildings or to design new steel buildings. Three planar building models are chosen as numerical examples to demonstrate the validity of the proposed method. The optimal SDB designs are compared with a uniform SDB design that uniformly distributes the total stiffness across the structure. The results of the analysis clearly show that each optimal SDB placement, which is determined based on different performance objectives, performs well for its own design aim.

Key Words
steel diagonal brace; artificial bee colony algorithm; structural optimization; transfer functions

Address
(1) E. Aydin:
Department of Civil Engineering, Nigde University, 51240 Nigde, Turkey;
(2) M. Sonmez and T. Karabork:
Department of Civil Engineering, Aksaray University, 68100 Aksaray, Turkey.

Abstract
This work presents a free vibration analysis of functionally graded metal-ceramic (FG) beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. For this purpose, a simple displacement field based on higher order shear deformation theory is implemented. The proposed theory is based on the assumption that the transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The most interesting feature of this theory is that it accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the beam without using shear correction factors. In addition, it has strong similarities with Euler-Bernoulli beam theory in some aspects such as equations of motion, boundary conditions, and stress resultant expressions. The rule of mixture is modified to describe and approximate material properties of the FG beams with porosity phases. By employing the Hamilton\'s principle, governing equations of motion for coupled axial-shear-flexural response are determined. The validity of the present theory is investigated by comparing some of the present results with those of the first-order and the other higher-order theories reported in the literature. Illustrative examples are given also to show the effects of varying gradients, porosity volume fraction, aspect ratios, and thickness to length ratios on the free vibration of the FG beams.

Key Words
FG beam; shear deformation theory; vibration; porosity

Address
(1) Hassen Ait Atmane, Abdelouahed Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(2) Hassen Ait Atmane:
Faculté de Génie Civil et D\'Architecture, Université Hassiba Ben Bouali Chlef, Algérie;
(3) Abdelouahed Tounsi:
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria;
(4) Fabrice Bernard:
Laboratoire de Génie Civil et Génie Mécanique INSA de Rennes, France;
(5) S.R. Mahmoud:
Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia;
(6) S.R. Mahmoud:
Mathematics Department, Faculty of Science, University of Sohag, Egypt.

Abstract
This paper presents the status improvement of an old damaged deck type rural road steel truss bridge through the modal parametric study after partial retrofitting. The dynamic and static tests on bridge were carried out as in damaged state and after partial retrofitting. The dynamic testing on the steel bridge was carried out using accelerometers under similar environmental conditions with same speed of the moving vehicle. The comparison of the modal parameters i.e., frequency, mode shape mode shape curvature, modal strain energy, along with the deflection parameter are studied with respect to structural analytical model parameters. The status up gradation for the upper and downstream truss obtained was different due to differential level of damage in the bridge. Also after retrofitting the structural elemental behavior obtained was not same as desired. The damage level obtained through static tests carried out using total station indicated further retrofitting requirement.

Key Words
steel truss bridge; retrofitting; frequency; mode shape; modal strain energy

Address
(1) Suresh Kumar Walia, Hemant Kumar Vinayak:
Department of Civil Engineering, NIT Hamirpur, Anu, Hamirpur, Himachal Pradesh 177005, India;
(2) Ashok Kumar, Raman Parti:
Department of Earthquake Engineering, IIT Roorkee, Roorkee-Haridwar Highway, Roorkee, Uttarakhand 247667, India.

Abstract
We proposed the concept of nominal rigidity of a long-span V-shaped rigid frame composite arch bridge, analyzed the effects of structural parameters on nominal rigidity, and derived a theoretical nominal rigidity equation. In addition, we discussed the selection of the arch-to-beam rigidity ratio and its effect on the distribution of internal forces, and analyzed the influence of the ratio on the internal forces. We determined the delimitation value between rigid arch-flexible beam and flexible arch-rigid beam. We summarized the nominal rigidity and arch to beam rigidity ratios of existing bridges. The results show that (1) rigid arch-flexible beam and flexible arch-rigid beam can be defined by the arch-to-beam rigidity ratio; (2) nominal rigidities have no obvious differences among the continuous rigid frame composite arch bridge, V-shaped rigid frame bridge, and arch bridge, which shows that nominal rigidity can reflect the global stiffness of a structure.

Key Words
bridge engineering; V-shaped rigid frame composite arch bridge; nominal rigidity; structural parameters; arch-to-beam rigidity ratio

Address
Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, P.R. China.

Abstract
Many methods are developed for strengthening of reinforced concrete structural members against the effects of shear. One of the commonly used methods in recent years is turned out to be bonding of fiber reinforced polymers (FRP). Impact loading is one of the important external effects on the reinforced concrete structural members during service period among the others. The determination of magnitude, the excitation time, deformations and stress due to impact loadings are complicated and rarely known. In recent year impact behavior of reinforced concrete members have been researched with experimental studies by using drop-weight method and numerical simulations are done by using finite element method. However the studies on the strengthening of structural members against impact loading are very seldom in the literature. For this reason, in this study impact behavior of shear deficient reinforced concrete beams that are strengthened with carbon fiber reinforced polymers (CFRP) strips are investigated experimentally. Compressive strength of concrete, CFRP strips spacing and impact velocities are taken as the variables in this experimental study. The acceleration due to impact loading is measured from the specimens, while velocities and displacements are calculated from these measured accelerations. RC beams are modeled with ANSYS software. Experimental result and simulations result are compared. Experimental result showed that impact behaviors of shear deficient RC beams are positively affected from the strengthening with CFRP strip. The decrease in the spacing of CFRP strips reduced the acceleration, velocity and displacement values measured from the test specimens.

Key Words
shear deficient rc beam; impact behavior; cfrp strip; strengthening

Address
(1) Özgür Anıl:
Department of Civil Engineering, Faculty of Engineering, Gazi University,Maltepe, Ankara, Turkey;
(2) Tolga Yımaz:
Department of Civil Engineering, Faculty of Engineering, Eskişhir Osmangazi University, Odunpazarı Eskişhir, Turkey.

Abstract
This paper presents the experimental results of flexural and compression steel members strengthened with carbon fiber reinforced polymers (CFRP) sheets. In the flexural test, the five specimens were fabricated and the test parameters were the number of CFRP ply and the ratio of partial-length bonded CFRP sheets of specimen. The CFRP sheet strengthened steel beam had failure mode: CFRP sheet rupture at the mid span of steel beams. A maximum increase of 11.3% was achieved depending on the number of CFRP sheet ply and the length of CFRP sheet. In the compression test, the nine specimens were fabricated and the main parameters were: width-thickness ratio (b/t), the number of CFRP ply, and the length of the specimen. From the tests, for short columns it was observed that two sides would typically buckle outward and the other two sides would buckle inward. Also, for long columns, overall buckling was observed. A maximum increase of 57% was achieved in axial-load capacity when 3 layers of CFRP were used to wrap HSS columns of b/t = 60 transversely.

Key Words
FRP; CFRP; steel beam; Hollow Steel Section (HSS); long column; short column; retrofit

Address
(1) Jai-woo Park:
Korea Infrastructure Safety Corporation., 315, Goyang-Daero, Ilsan-Gu, Goyang-city, Gyeonggi-Do, 411-758, Republic of Korea;
(2) Jung-han Yoo:
School of Architecture, Seoul National University of Science & Technology, 232 Gongreung-ro, Nowon-gu, Seoul, 139-743, Republic of Korea.

Abstract
Seismic performances of dual steel moment-resisting frames with mixed use of rigid and semi-rigid connections were investigated to control of the base shear, story drifts and the ductility demand of the elements. To this end, nonlinear seismic responses of three groups of frames with three, eight and fifteen story were evaluated. These frames with rigid, semi-rigid and combined configuration of rigid and semi-rigid connections were analyzed under five earthquake records and their responses were compared in ultimate limit state of rigid frame. This study showed that in all frames, it could be found a state of semi-rigidity and connections configuration which behaved better than rigid frame, with consideration of the base shear and story drifts criterion. Finally, some criteria were suggested to locate the best place of the semi-rigid connections for improvement of the seismic performance of steel moment-resisting frames.

Key Words
semi-rigid connections; dual steel moment-resisting frames; seismic behavior, base shear; story drift

Address
Department of Civil Engineering, University of Tabriz, Tabriz, Iran.

Abstract
Channels are implemented in composite beams as shear connectors in two arrangements, face to face and back to back. No relevant explanation is found in the design codes to clarify the preference of the mentioned arrangements. Besides, the designers do not have a common opinion on this subject; i.e., some recommend the face to face and others, back to back status. In this research, channel shear connectors in composite beams are studied analytically for both arrangements using ABAQUS software. For this purpose, they have been modeled in simply supported beams in the arrangements of face to face and back to back; their effects on the crack initiation load of concrete slabs were monitored. The stiffness values of composite beams were also compared in the two arrangements using force-displacement curve; the results are relatively the same in both cases. Furthermore, the effects of compressive strength of concrete, channel size, length and spacing of channels as well as steel type of channels on the performance of composite beams have been investigated. According to the results obtained in this research, the face to face status shows better performance in comparison with that of back to back, considering the load of concrete fracturing.

Key Words
composite beam; channel shear connector; face to face; back to back; crack

Address
(1) Nader Fanaie, Farzaneh Ghalamzan Esfahani:
Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran;
(2) Soheil Soroushnia:
Islamic Azad University, Takestan Branch, Takestan, Iran.

Abstract
This paper presents an optimization process using Genetic Algorithm (GA) for minimum weight by selecting suitable standard sections from a specified list taken from American Institute of Steel Construction (AISC). The stress constraints obeying AISC-LRFD (American Institute of Steel Construction - Load and Resistance Factor Design), lateral displacement constraints being the top and inter-storey drift, mid-span deflection constraints for the beams and geometric constraints are considered for optimum design by using GA that mimics biological processes. Optimum designs for three different space frames taken from the literature are carried out first without considering concrete slab effects in finite element analyses for the constraints above and the results are compared with the ones available in literature. The same optimization procedures are then repeated for the case of space frames with composite (steel and concrete) beams. A program is coded in MATLAB for the optimization processes. Results obtained in the study showed that consideration of the contribution of the concrete on the behavior of the floor beams results with less steel weight and ends up with more economical designs.

Key Words
genetic algorithm; weight optimization; space frame; composite beams; fem analysis

Address
(1) Musa Artar:
Department of Civil Engineering, Bayburt University, Bayburt 69000, Turkey;
(2) Ayşe T. Daloğlu:
Department of Civil Engineering, Karadeniz Technical University, Trabzon 61000, Turkey.


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