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CONTENTS
Volume 27, Number 6, December 2024
 

Abstract
In this contribution, the vibration behavior of laminated composite plates is studied using the refined simplified nth-higher-order shear deformation theory (RSHSDT). Thus, the dimensionless fundamental frequency obtained for the first vibration mode of the antisymmetric cross-ply and angle-ply laminates composite plates was calculated. In this study, we discuss the effect of the degree of orthotropy which is defined by the ratio of Young's moduli of two different directions, the effect of the geometry and the thickness of the plate, the number and of the stacking sequence of the layers, and the orientation angle of the fibers of the component layers. Finally, to evaluate the effect of shear deformation in the free vibration behavior of laminated composite plates, the numerical results obtained by the present theory are compared with those corresponding to the classical laminated plate theory (CLPT) which is considered a special case of this theory when the shear component of transverse displacement to zero. The results of this theory show good agreement with those predicted by shear deformation theories available in the literature in predicting vibration responses.

Key Words
cross-ply and angle-ply laminates; fiber orientation; laminated plates; RSHSDT; vibrations

Address
Yamina Kenouza: Department of Civil Engineering, University Tahri Mohammed of Bechar, Bechar 08000, Algeria
Mokhtar Bouazza: 1) Department of Civil Engineering, University Tahri Mohammed of Bechar, Bechar 08000, Algeria, 2) Laboratory of Materials and Hydrology (LMH), University of Sidi Bel Abbes, Sidi Bel Abbes 22000, Algeria
Ashraf M. Zenkour: 1) Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia, 2) Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafrelsheikh 33516, Egypt
Noureddine Benseddiq: Lille Mechanics Unit-UML, ULR 7512, University of Lille, Villeneuve d'Ascq, France

Abstract
Three post-earthquake repair techniques were developed to restore or upgrade the capacity of fractured pre-Northridge beam-column connections. Four full-scale beam-to-box column connections were prepared and cyclically loaded until fracture. Three of them fractured at the bottom flange under the drift of about 2 to 3%, and one fractured at the top flange. The bottom flange fractured connections were then repaired and tested again. The results showed that the combination of applying supplemental welds at the web and attaching wing plates to the bottom flange increased the strength and ductility. The repaired connection fractured at the top flange at the drift amplitude of 4%. When inner flange stiffeners were additionally applied on the top flange for enhancement, the stress concentration was moved to the beam from the connection and resulted in a most ductile behavior among the repair techniques. The weld-free repair technique, which attaching the reduced section plate at the bottom flange by high tension bolts, exhibited a comparable performance to the connection repaired by adding additional welds and wing plates. Overall, the combination of attaching wing plates and inner stiffeners at the bottom and top flanges, respectively, would provide reliable performance.

Key Words
ductility; fracture; post-earthquake repair; WUF-B connection

Address
Department of Architecture, National Cheng Kung University, 701 No.1, University Road, Tainan City, Taiwan

Abstract
Geotechnical earthquake engineering requires a comprehensive understanding of soil-structure interaction response to seismic activity. Shaking table and centrifuge tests using rigid and flexible soil box are carried out for physical modeling experiments to understand the soil-structure interaction response to seismic activity. In this study, a laminar shear box of 720 mm in length, 390 mm in width, and 720 mm in height was designed using 15 horizontal laminas of aluminum C-section for a small shake table instrument. The soil bed acceleration and nonlinearity were measured using a newly designed low-cost data acquisition (DAQ) system developed using the Arduino Uno board and the ADXL345 accelerometer sensor. The serial peripheral interface (SPI) protocol was utilized to collect output data from DAQ for data transfer. The calibration of the laminar shear box for boundary effect, inertia effect, and soil densification was determined for the flawless working of the box. Stress-strain behavior, acceleration, damping ratio, and strain-dependent modulus, such dynamic response parameters of the soil bed, are being studied. During the shaking table test, considerable strain and subsequent inelasticity are observed. Increased excitation energy in soil reduces shear modulus, and flatter loops indicate more nonlinearity and a higher damping ratio, meaning increased energy dissipation. The laminar shear box integrated with the developed DAQ system demonstrated reliable performance in recording soil response data and analyzing dynamic soil properties, providing insights into soil-structure interactions. The findings offer a cost-effective solution for dynamic soil testing, crucial for understanding soil behavior during earthquakes and other dynamic events and improving engineering practices.

Key Words
acceleration amplification; data acquisition system; ground response analysis; laminar shear box; nonlinearity of soil bed; stress-strain behavior

Address
Civil Engineering Department, Visvesvaraya National Institute of Technology, Nagpur 440010, Maharashtra, India

Abstract
Considering the development of precast structures in low-rise buildings, a new precast shear wall made of ceramsite concrete is proposed in this paper, with welded wire mesh (WWM) utilized as the load-bearing reinforcement. Three different dry connection methods were designed and fabricated: welding, bolting and bolting plus mortar-bonding. The seismic performance of three precast shear wall specimens and one cast-in-place shear wall specimen was assessed by quasi-static tests. The failure mode, bearing capacity, hysteresis characteristics, ductility, stiffness degradation, slip, and energy dissipation of the specimens were obtained by analyzing the test results of the hysteresis curve, crack distribution and WWM strain. The test results show that the failure modes of the new precast shear walls under the three connection methods differ. The damage is mainly concentrated at the joints, and the wall damage is less severe. Compared to cast-in-place shear wall, precast shear walls with bolted and welded connections show lower load-bearing capacity and stiffness but offer enhanced ductility and energy dissipation. These walls primarily dissipate energy through slip, with over 80% of the dissipation during elastic-plastic and damage stages. Bolted plus mortar-bonded connection exhibit increased stiffness in the walls but lead to earlier damage and reduced energy dissipation. Lastly, based on the research results and analysis, the analysis method and calculation model for predicting the transverse bearing capacity of new shear walls under dry connections are proposed.

Key Words
ceramsite concrete; low-rise building; precast concrete shear wall; seismic behavior; welded wire mesh

Address
Huadong Zhang, Kang Yuan and Gang Zhang: College of Water Conservancy & Architectural Engineering, Shihezi University, Shihezi, 832003, China
Yueyue Gao: Xinjiang Architectural Design Institute Co., Ltd, Wulumuqi, 830013, China

Abstract
This study aims to analyze the seismic behavior of reinforced concrete columns, based on various factors such as compressive strength, slenderness, and longitudinal reinforcement ratios. These factors are crucial in determining the ductility, strength, stiffness, and energy dissipation of reinforced concrete columns. The study examines the impact of different compressive strength, slenderness, and longitudinal reinforcement ratios on the seismic performance of reinforced concrete columns. To conduct the analysis, the FE computer program Seismo-structure was used to evaluate a series of reinforced concrete columns experimental tests. Special attention was given to selecting models for concrete, confined concrete, and steel components to accurately capture the behavior of the specimens. The results showed good agreement between experimental and analytical data in terms of lateral force-drift relationships and damage prediction.

Key Words
compressive strength; ductility; longitudinal reinforcement; slenderness

Address
National Earthquake Engineering Research Centre, C.G.S 01, Rue Kaddour Rahim, BP 252, Hussein Dey, Alger, Algeria

Abstract
Relying on the metro line 4 interval tunnel in Chongqing, the dynamic response of orthogonal tunnels at different locations under the influence of horizontal seismic wave sat different time intervals are studied with an earthquake of intensity VIII. By analysis the ANSYS numerical model simulation results and actual monitoring results, the following conclusions can be derive. (1) The lining stress change shows a positive parabolic phenomenon, and the optimal spacing of the upper and lower tunnels can be derived from the stress change as 1.5 times the hole diameter. (2) By studying the displacement values of the monitoring points in the orthogonal tunnel with different spacing between the upper and lower tunnels, it can be seen that the displacement in the horizontal direction of each monitoring point is significantly larger than that in the vertical direction, which leads to the conclusion that the seismic wave in the horizontal direction has a greater effect on the horizontal direction of the tunnel lining. (3) The upper tunnel is most affected by seismic waves at the arch top, followed by the arch waist and the arch foot, and finally the arch bottom. (4) The peak of horizontal displacement in the orthogonal tunnel under the action of horizontal seismic waves is 20 m from the portal of the upper tunnel, rather than the orthogonal part. The research results can provide a helpful manual for the design and construction of orthogonal tunnels in earthquake areas.

Key Words
dynamic response; numerical simulation; seismic wave; tunnel

Address
Chen Yang: School of Civil Engineering, Sichuan University Jinjiang College, Meishan 620860, China
Zelin Lu and Yinwen Wang: School of Civil Engineering, Qingdao University of Technology, Qingdao 266520, China

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