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CONTENTS
Volume 64, Number 2, October25 2017
 

Abstract
In this article, a novel simple higher-order shear deformation theory for bending and free vibration analysis of functionally graded (FG) beams is proposed. The beauty of this theory relies on its 2-unknowns displacement field as the Euler- Bernoulli beam theory, which is even less than the Timoshenko beam theory. A shear correction factor is, therefore, not needed. Equations of motion are obtained via Hamilton‟s principle. Analytical solutions for the bending and free vibration analysis are given for simply supported beams. Efficacy of the proposed model is shown through illustrative examples for bending and dynamic of FG beams. The numerical results obtained are compared with those of other higher-order shear deformation beam theory results. The results obtained are found to be accurate.

Key Words
a simple 2-unknown theory; bending; vibration; functionally graded beams

Address
Mohamed Zidi, Mohammed Sid Ahmed Houari, Abdelouahed Tounsi, Aicha Bessaim: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia



Abstract
This paper presents a proposed method for producing reinforced composite concrete columns reinforced with various types of metallic and non metallic mesh reinforcement. The experimental program includes casting and testing of twelve square columns having the dimensions of 100 mmx100 mmx1000 mm under concentric compression loadings. The test samples comprise all designation specimens to make comparative study between conventionally reinforced concrete column and concrete columns reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh and tensar mesh. The main variables are the type of innovative reinforcing materials, metallic or non metallic, the number of layers and volume fraction of reinforcement. The main objective is to evaluate the effectiveness of employing the new innovative materials in reinforcing the composite concrete columns. The results of an experimental investigation to examine the effectiveness of these produced columns are reported and discussed including strength, deformation, cracking, and ductility properties. Non-linear finite element analysis; (NLFEA) was carried out to simulate the behavior of the reinforced concrete composite columns. The numerical model could agree the behavior level of the test results. ANSYS-10.0 Software. Also, parametric study is presented to look at the variables that can mainly affect the mechanical behaviors of the model such as the change of column dimensions. The results proved that new reinforced concrete columns can be developed with high strength, crack resistance, and high ductility properties using the innovative composite materials.

Key Words
ferrocement; concrete columns; composite material; experimental; FE modeling; strength; parametric study

Address
Yousry B.I. Shaheen: Civil Engineering Department, Faculty of Engineering, Menoufia University, Menoufia, Egypt
Ashraf M. Mahmoud: Civil Engineering Department, Faculty of Engineering, Modern University for Technology and Information (MTI), Al-Mokattam, Cairo, Egypt
Hala M. Refat : Civil Engineering Department, Faculty of Engineering, Benha University, Benha, Egypt

Abstract
This paper analyzes the influence of the construction process on short- and long-term deflections on a reinforced concrete structure poured on-site by a portable industrialized system. A parametric analysis was carried out by the Finite Elements Method (FEM) that considered: a) type of construction process with reshoring or clearing (partial striking); b) the number of successively shored floors and c) the number of shores used on each floor. All three factors were especially important for the values of short- and long-term deflections, which were highest in the reshoring processes with the lowest number of successively shored floors and the lowest number of shores per floor. Deflections obtained were compared with the limits laid down by ACI 318-14 and as calculated by this code

Key Words
clearing; construction process; creep; deflection; industrialized system; shores; shoring; striking

Address
Yezid A. Alvarado, María N. Domínguez, Miguel A. Cipagauta: Pontificia Universidad Javeriana, Calle 40 No. 5-50 Ed., José Gabriel Maldonado, S.J., Bogotá, Colombia
Manuel Buitrago, Isabel Gasch: ICITECH, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain

Abstract
This paper presents the experimental investigation into a new type of steel-concrete hybrid outrigger system developed for the high-rise building structure. The steel truss is embedded into the reinforced concrete outrigger wall, and both the steel truss and concrete outrigger wall work compositely to enhance the overall structural performance of the tower structures under extreme loads. Meanwhile, metal dampers of low-yield steel material were also adopted as a „fuse‟ device between the hybrid outrigger and the column. The damper is engineered to be „scarified‟ and yielded first under moderate to severe earthquakes in order to protect the structural integrity of important structural components of the hybrid outrigger system. As such, not brittle failure is likely to happen due to the severe cracking in the concrete outrigger wall. A comprehensive experimental research program was conducted into the structural performance of this new type of hybrid outrigger system. Studies on both the key component and overall system tests were conducted, which reveal the detailed structural response under various levels of applied static and cyclic loads. It was demonstrated that both the steel bracing and concrete outrigger wall are able to work compositely with the low-yield steel damper and exhibits both good load carrying capacities and energy dispersing performance through the test program. It has the potential to be applied and enhance the overall structural performance of the high-rise structures over 300 m under extreme levels of loads.

Key Words
composite structures; physical test; outrigger; damper; high-rise building

Address
A.J. Wang: Centre of Innovation for Building and Construction, CapitaLand China Corporate, Shanghai, P.R. China

Abstract
Analytical and experimental studies of the innovative pipe in pipe damper have been recently investigated by the authors. In this paper, by adding lead or zinc infill or slit diaphragm inside the inner pipe, it is tried to increase the equivalent viscous damping ratio improving the cyclic performance of the recently proposed multi-level control system. The damper consists of three main parts including the outer pipe, inner pipe and added complementary damping part. At first plastic deformations of the external pipe, then the internal pipe and particularly the added core and friction between them make the excellent multi-level damper act as an improved energy dissipation system. Several kinds of added lead or zinc infill and also different shapes of slit diaphragms are modeled inside the inner pipe and their effectiveness on hysteresis curves are investigated with nonlinear static analyses using finite element method by ABAQUS software. Results show that adding lead infill has no major effect on the damper stiffness while zinc infill and slit diaphragm increase damper stiffness sharply up to more than 10 times depending on the plate thickness and pipe diameter. Besides, metal infill increases the viscous damping ratio of dual damper ranging 6-9%. In addition, obtained hysteresis curves show that the multi-level control system as expected can reliably dissipate energy in different imposed energy levels.

Key Words
multi-level damper; metal infill; slit diaphragm; cyclic performance; ductility; numerical analysis

Address
Seyed Mehdi Zahrai: Center of Excellence for Engineering and Management of Civil Infrastructures, School of Civil Engineering, College of Engineering, The University of Tehran. P.O. Box 11155-4563, Tehran, Iran
Abdullah Cheraghi: 2Department of Civil Engineering, Arak branch, Islamic Azad University, Arak, Iran

Abstract
Based on the coupled elastic bending deformation features and relationships between the internal force and deformation of pre-twisted Euler beam, the generalized strain, the equivalent constitutive equation and the equilibrium equation of pre-twisted Euler beam are developed. Based on the properties of the dual-antisymmetric matrix, the general solution of pretwisted Euler beam is obtained. By comparison with ANSYS solution by using straight Beam-188 element based on infinite approach strategy, the results show that the developed method is available for pre-twisted Euler beam and also provide an accuracy displacement interpolation function for the subsequent finite element analysis. The effect of pre-twisted angle on the mechanical property has been investigated.

Key Words
pre-twisted beam; coupled displacement; generalized strain; general solution

Address
Ying Huang: School of Civil Engineering, Xi\'an, 710055, China
Chang Hong Chen: School of Mechanics and Civil Engineering, Northwestern Polytechnical University, Xi\'an, 710129, China
Leon M. Keer: Civil and Environmental Engineering, Northwestern University, Evanston, IL, 60286, USA
Yao Yao: School of Mechanics and Civil Engineering, Northwestern Polytechnical University, Xi\'an, 710129, China

Abstract
Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with nonlinear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.

Key Words
concrete bridges; fragility curves; non-linear dynamic analysis; incremental dynamic analysis; Pakistan

Address
Muhammad Waseem: National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan
Enrico Spacone: Department of Engineering and Geology, University of Chieti-Pescara, Viale Pindero, 42, 65127, Pescara, Italy

Abstract
Leaning-type arch bridge is a new spatial structural system composed of two vertical arches and two leaning arches. So far there has been no contrast analysis of leaning type arch bridge with different systems. This paper focus on a parametric study of leaning type arch bridge with different systems to find the influential rules on structural forces and stability and to provide some reference for practical designs. The parametric analysis is conducted with different rise-to-span ratios and bending rigidities of arch ribs by comparing internal forces. The internal forces decline obviously with the increase of the rise-to-span ratio. The bending moments at the centers of the main arches and the leaning arches are sensitive to the bending rigidities of arch ribs. Parametric studies are also carried out with different structural systems and leaning angles of the leaning arch by comparing the static stability. The lateral stiffness of leaning-type arch bridge is less than the in-plan stiffness. Compared with the leaning-type arch bridge without thrust, the leaning-type arch bridge with thrust has a lower stability safety coefficient. The stability safety coefficient rises gradually with the increase of inclining angle of the leaning arch. This study shows that the rise-to-span ratio, bending rigidities of arch ribs, structural system and leaning angles of the leaning arch are all critical design parameters. Therefore, these parameters in unreasonable range should be avoided.

Key Words
leaning-type arch bridge; parametric analysis; rise-to-span ratio; bending rigidities of arch ribs; leaning angle of the leaning arch

Address
Ying Li, Ru-Cheng Xiao and Bin Sun: Department of Bridge Engineering, Tongji University, Shanghai 200092, China

Abstract
Earlier numerous studies have been done on implementation of Tuned Liquid Damper (TLD) for structural vibration control by many researchers. As per current review there is no significant study on a sloped bottom TLD. TLD\'s are passive devices. A TLD is a tank rigidly attached to the structure and filled partially by liquid. When fundamental linear sloshing frequency is tuned to structure\'s natural frequency large sloshing amplitude is expected. In this study set of experiments are conducted on flat bottom and sloped bottom TLD at beach slope 20o, 30o and 45o, for different types of structures, mass ratio, and depth ratio to investigate the overall effectiveness of TLD and specific effect of TLD parameters on structural response. This experimental study shows that a properly designed TLD reduces structural response. It is also observed that effectiveness of TLD increases with increase in mass ratio. In this experimental study an effectiveness of sloped bottom TLD with beach slope 30o is investigated and compared with that of flat bottom TLD in reducing the structural response. It is observed from this study that efficiency of sloped bottom TLD in reducing the response of structure is more as compared to that of flat bottom TLD. It is shown that there is good agreement between numerical simulation of flat bottom and sloped bottom TLD and its experimental results. Also an attempt has been made to investigate the effectiveness of sloped bottom TLD with beach slope 20o and 45o.

Key Words
tuned liquid dampers; vibration control; sloshing; energy dissipation; TLD design and base excitation

Address
Amardeep D. Bhosale and Mohan M. Murudi: Department of Structural Engineering, Sardar Patel College of Engineering, Andheri (west), Mumbai - 400058, India

Abstract
Investigating the properties and durability of high-strength concrete exposed to sulfuric acid attack for the purpose of its application in structures exposed to this acid is of outmost importance. In this research, the resistance and durability of highstrength concrete containing macro-polymeric or steel fibers together with the pozzolans of silica fume or nano-silica against sulfuric acid attack are explored. To accomplish this goal, in total, 108 high-strength concrete specimens were made with 9 different mix designs containing macro-polymeric and steel fibers at the volume fractions of 0.5, 0.75, and 1.0%, as well as the pozzolans of silica fume and nano-silica with the replacement levels of 10 and 2%, respectively. After placing the specimens inside a 5% sulfuric acid solution in the periods of 7, 21, and 63 days of immersion, the effect of adding the fibers and pozzolans on the compressive properties, ultrasonic pulse velocity (UPV), and weight loss of high-strength concrete was investigated and the respective results were compared with those of the reference specimens. The obtained results suggest the dependency of the resistance and durability loss of high-strength concrete against sulfuric acid attack to the properties of fibers as well as their fraction in concrete volume. Moreover, compared with using nano-silica, using silica fume in the fibrous concrete mix leads to more durable specimens against sulfuric acid attack. Finally, an optimum solution for the design parameters where the crushing load of high-strength fibrous concrete is maximized was found using response surface method (RSM).

Key Words
sulfuric acid attack; fibers; silica fume; nano-silica; ultrasonic test; crushing load; high-strength concrete; response surface method; optimization

Address
Mahdi Nematzadeh and Saber Fallah-Valukolaee: Department of Civil Engineering, University of Mazandaran, Babolsar, Iran

Abstract
The stochastic vibration response of the sandwich beam with the nonlinear adjustable visco-elastomer core and supported mass under stochastic support motion excitations is studied. The nonlinear dynamic properties of the visco-elastomer core are considered. The nonlinear partial differential equations for the horizontal and vertical coupling motions of the sandwich beam are derived. An analytical solution method for the stochastic vibration response of the nonlinear sandwich beam is developed. The nonlinear partial differential equations are converted into the nonlinear ordinary differential equations representing the nonlinear stochastic multi-degree-of-freedom system by using the Galerkin method. The nonlinear stochastic system is converted further into the equivalent quasi-linear system by using the statistic linearization method. The frequencyresponse function, response spectral density and mean square response expressions of the nonlinear sandwich beam are obtained. Numerical results are given to illustrate new stochastic vibration response characteristics and response reduction capability of the sandwich beam with the nonlinear visco-elastomer core and supported mass under stochastic support motion excitations. The influences of geometric and physical parameters on the stochastic response of the nonlinear sandwich beam are discussed, and the numerical results of the nonlinear sandwich beam are compared with those of the sandwich beam with linear visco-elastomer core.

Key Words
stochastic nonlinear vibration; sandwich beam; nonlinear visco-elastomer core; stochastic excitation; statistic linearization

Address
Z.G. Ying: Department of Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, P.R. China
Y.Q. Ni: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Y. F. Duan: Department of Civil Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, P.R. China

Abstract
In this paper, we propose a new conjugate gradient method which possesses the global convergence and apply it to solve inverse problems of the dynamic loads identification. Moreover, we strictly prove the stability and convergence of the proposed method. Two engineering numerical examples are presented to demonstrate the effectiveness and speediness of the present method which is superior to the Landweber iteration method. The results of numerical simulations indicate that the proposed method is stable and effective in solving the multi-source dynamic loads identification problems of practical engineering.

Key Words
inverse problems; multi-source dynamic loads identification; finite element method; conjugate gradient method

Address
Lin J. Wang: Hubei Key Laboratory of Hydroelectric Machinery Design and Maintenance, College of Mechanical and Power Engineering,China Three Gorges University, Yichang, Hubei 443002, PR China; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4001, Australia
Qi C. Deng: Hubei Key Laboratory of Hydroelectric Machinery Design and Maintenance, College of Mechanical and Power Engineering, China Three Gorges University, Yichang, Hubei 443002, PR China
You X. Xie: College of Science Technology, China Three Gorges University, Yichang, Hubei 443002, PR China


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