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CONTENTS
Volume 27, Number 4, October 2024
 

Abstract
To improve the seismic behavior of composite column with high strength concrete-filled steel tubular in bridge engineering, four column specimens, including one specimen with vertical prestressing force and three specimens with tri-directional prestressing force, were conducted under low cyclic loading. Test parameters including axial compression ratio, degree of vertical prestressing and existence of prestressed steel strips were emphatically analyzed. Experimental results revealed that applying tri-directional prestressing force to column with high strength concrete-filled steel tubular produced more beneficial behavior in terms of ductility, energy-dissipation and self-centering capacity over that of specimens only with vertical prestress. Moreover, ultimate bearing capacity of composite column was improved with increase of degree of vertical prestress and external axial force, while ductility would be reduced. External axial force showed slight influence on the self-centering behavior. Finally, a calculation equation for predicting the shear capacity of the tri-directional prestressed composite column was proposed and the accuracy of the calculated results validated by experimental data.

Key Words
composite column; experimental study; quasi-static test; seismic behavior; self-centering capacity; shear capacity; tri-directional prestressing

Address
Yang Chen: 1) School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200444, China,
2) State Key Laboratory of Green Building, Xi'an University of Architecture & Technology, Xi'an, Shaanxi, 710055, China
Zhaowei Jiang: School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200444, China
Yingjun Gan: School of Digital Construction, Shanghai Urban Construction Vocational College, Shanghai, 201415, China
Jun Ye: Xi'an University of Architecture & Technology Engineering Technology Co., Ltd, Xi'an, Shaanxi, 710055, China

Abstract
This research introduces a new composite system that utilizes multiple moving masses to identify cracks in structures resembling beams. The process starts by recording displacement time data from a set of these moving masses and converting this information into a relative time history through weighted aggregation. This relative time history then undergoes wavelet transform analysis to precisely locate cracks. Following wavelet examinations, specific points along the beam are determined as potential crack sites. These points, along with locations on the beam susceptible to cracked point due to support conditions, are marked as crack locations within the optimization algorithm's search domain. The model uses equations of motion based on the finite element method for the moving masses on the beam and employs the Runge-Kutta numerical solution within the state space. The proposed system consists of three successive moving masses positioned at even intervals along the beam. To assess its effectiveness, the method is tested on two examples: a simply supported beam and a continuous beam, each having three scenarios to simulate the presence of one or multiple cracks. Additionally, another example investigates the influence of mass speed, spacing between masses, and noise effect. The outcomes showcase the method's effectiveness and efficiency in localizing crack, even in the presence of noise effect in 1%, 5% and 20%.

Key Words
crack; dynamic deflection; Euler Bernoulli; finite element method; moving sprang mass; optimization algorithm

Address
Siamak Ghadimi and Gholamreza Zamani-Ahari: Department of Civil Engineering, Faculty of Engineering, Urmia University, Urmia, Iran
Seyed Sina Kourehli: Department of Civil Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran

Abstract
Conducting nonlinear pushover analysis typically demands intricate and resource-intensive computational efforts, involving a highly iterative process necessary for meeting both design-defined and requirements of codes in performance-based design. This study presents a computer-based technique for reinforced concrete (RC) buildings, incorporating optimization numerical approaches, optimality criteria and pushover analysis to automatically enhance seismic design performance. The optimal design of concrete beams, columns and shear walls in concrete frames is presented using the artificial bee colony optimization algorithm. The methodology is applied to three frames: a 4-story, an 8-story and a 12-story. These structures are designed to minimize overall weight while satisfying the levels of performance including Life Safety (LS), Collapse Prevention (CP), and Immediate Occupancy (IO). The process involves three main steps: first, optimization codes are implemented in MATLAB software, and the OpenSees software is used for nonlinear static analysis. By solving the optimization problem, several top designs are obtained for each frame and shear wall. Pushover analysis is conducted considering the constraints on relative displacement and plastic hinge rotation based on the nonlinear provisions of the FEMA356 nonlinear provisions to achieve each level of performance. Subsequently, convergence, pushover, and drift history curves are plotted for each frame, and leading to the selection of the best design. The results demonstrate that the algorithm effectively achieves optimal designs with reduced weight, meeting the desired performance criteria.

Key Words
artificial bee colony algorithm; nonlinear pushover analysis; performance-based optimization; reinforced concrete buildings; seismic design

Address
Saba Faghirnejad: Department of Civil, Environmental and Architectural Engineering, The University of Kansas, Lawrence, Kansas, USA
Denise-Penelope N. Kontoni: 1) Department of Civil Engineering, School of Engineering, University of the Peloponnese, GR-26334 Patras, Greece, 2) School of Science and Technology, Hellenic Open University, GR-26335 Patras, Greece
Mohammad Reza Ghasemi: Department of Civil Engineering, University of Sistan and Baluchestan, Zahedan, Iran

Abstract
This study proposes a comprehensive methodology for estimating accumulative damage of bridge structures under multiple seismic excitations, in the framework of site-specific probabilistic hazard analysis. Specifically, a typical earthquake prone region in China is chosen to perform probabilistic seismic hazard analysis (PSHA) to find the mean annual rate (MAR) of ground motion intensity at a specific level, based on which, a mass of ground motion observations is selected to construct random earthquake sequences with various number of shocks. Then, nonlinear time history analysis is implemented on the finite element (FE) model of a RC girder bridge at the site of interest, to investigate structural responses under different earthquake sequences, and to develop predictive model for cumulative damage computation, in which, a scalar seismic intensity measure (IM) is adopted and its performance in damage prediction is discussed by an experimental column. Furthermore, a mathematic model is established to calculate occurrence probability of earthquakes with various number of shocks, based on PSHA and homogenous Poisson random process, and a modified cumulative damage indicator is proposed, accounting for probabilistic occurrence of various earthquake scenarios. At end, the applicability of the proposed methodology to main shock and aftershock scenarios is validated, and characteristics of damage accumulation under different multiple earthquake scenarios are discussed.

Key Words
cumulative damage; multiple earthquakes; probabilistic seismic hazard; RC bridges; seismic intensity measure

Address
Lang Liu, Hao Luo, Yanhang Wang, Changqi Zhao and Nanyue Shi: School of Civil Engineering, Chongqing Jiaotong University Chongqing 400074, China
Mingming Wang: Sichuan Earthquake Agency, Chengdu 610041, China

Abstract
Recent earthquakes have demonstrated that even when the beams and columns in a reinforced concrete frame remain intact, the integrity of the whole structure is undermined if the joint where these members connect fails. A good seismic performance of reinforced concrete frames depends on their ability to absorb seismic energy through inelastic deformations and to avoid a sudden development of collapse mechanism in event of a strong earthquake shaking. The primary objective of this investigation is to move the plastic hinge away from the beam-column joint region and hence reducing the damage to the joint region. In this research, the seismic performance of exterior beam-column joints with four types of confinement in joint region and inclined bars from column to beam is investigated experimentally. Control specimens without inclined bars and four types of confinement Square Hoop, Square Spiral, Circular Hoop and Circular Spiral were tested along with inclined bars were tested. Seismic performance was determined via load-deflection response, ductility, stiffness, energy dissipation, strain of beam reinforcement and crack pattern. Out of the four specimens with inclined bars, seismic performance of joint with Square Spiral confinement gave the best performance in terms of all parameters.

Key Words
beam; column; confinement; hinge; joint; plastic

Address
P.Asha: Meenakshi Sundararajan Engineering College,Chennai - 600024, Tamil Nadu, India
R.Sundararajan and K.Kumar: Government College of Technology, Coimbatore - 641013, Tamilnadu, India

Abstract
The performance of reinforced concrete buildings subjected to earthquake excitations depends on the structural behaviour of the superstructure as well as the type of foundation and the properties of soil on which the structure is founded. The consideration of the effects due to the interaction between the structure and soil- foundation alters the seismic response of reinforced concrete buildings subjected to earthquake motion. Evaluation of the structural response of buildings for quantitative assessment of the seismic fragility has been a demanding problem for the engineers. Present research deals with development of fragility curve for building specific vulnerability assessment based on different damage parameters considering the effect of soil structure interaction. Incremental Dynamic Analysis of fixed base and flexible base RC building models founded on different soil conditions was conducted using finite element software. Three sets of fragility curves were developed with maximum roof displacement, inter storey drift and plastic energy dissipated as engineering demand parameters. The results indicated an increase in the likelihood of exceeding various damage limits by 10-40% for flexible base condition with soft soil profiles. Fragility curve based on energy dissipated showed a higher probability of exceedance for collapse prevention damage limit whereas for lower damage states, conventional methods showed higher probability of exceedance. With plastic energy dissipated as engineering demand parameter, it is possible to track down the intensity of earthquake at which the plastic deformation starts, thereby providing an accurate vulnerability assessment of the structure. Fragility modification factors that enable the transformation of existing fragility curves to account for Soil-Structure Interaction effects based on different damage measures are proposed for different soil conditions to facilitate a congenial vulnerability assessment for buildings with flexible base conditions.

Key Words
energy dissipated; fragility curve; incremental dynamic analysis; soil-structure interaction

Address
Department of Civil Engineering, NITK, Surathkal, Karnataka, India

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