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CONTENTS
Volume 87, Number 4, August25 2023
 

Abstract
Targeted introduction of explosion-resisting and energy-absorbing materials and optimization of explosion-resisting composite structural styles in underground engineering are the most important measures for modern engineering protection. They could also improve the survivability of underground engineering in wartime. In order to test explosion-resisting and energy-absorbing effects of high-performance equal-sized-aggregate (HPESA) concrete, the explosive loading tests were conducted on HPESA concrete composite plates by field simple explosion craters. Time-history curves of the explosion pressure at the interfaces were obtained under six conditions with different explosion ranges and different thicknesses of the HPESA concrete plate. Test results show that under the same explosion range, composite plate structures with different thicknesses of the HPESA concrete plate differ significantly in terms of the wave-absorbing ability. Under the three thicknesses in the tests, the wave-absorbing ability is enhanced with the growing thickness and the maximum pressure attenuation index reaches 83.4%. The energy attenuation coefficient of the HPESA concrete plate under different conditions was regressively fitted. The natural logarithm relations between the interlayer plate thickness and the energy attenuation coefficient under the two explosion ranges were attained.

Key Words
energy absorption; explosion-resisting property; high-performance equal-sized-aggregate concrete; scaled explosion range

Address
Yizhong Tan: State Key Laboratory of Explosion Shock Prevention and Mitigation, National Defense Engineering College, Army Engineering University, Nanjing, 210007, China; Training Base, Army Engineering University, Xuzhou, 221004, China
Songlin Yue, Gan Li, Chao Li, Yihao Cheng: State Key Laboratory of Explosion Shock Prevention and Mitigation, National Defense Engineering College, Army Engineering University, Nanjing, 210007, China
Wei Dai: School of Science, Nanjing University of Science & Technology, Nanjing, 210094, China
Bo Zhang: Training Base, Army Engineering University, Xuzhou, 221004, China

Abstract
The idea of the combination of the fractional-order operators with the brain emotional learning-based intelligent controller (BELBIC) is developed for implementation in seismic-excited structures equipped with active mass damper (AMD). For this purpose, a new design framework of the mentioned combination namely fractional-order BEBIC (FOBELBIC) is proposed based on a modified-teaching-learning-based optimization (MTLBO) algorithm. The seismic performance of the proposed controller is then evaluated for a 15-story building equipped with AMD subjected to two far-field and two near-field earthquakes. An optimal BELBIC based on the MTLBO algorithm is also introduced for comparison purposes. In comparison with the structure equipped with a passive tuned mass damper (TMD), an average reduction of 44.7% and 42.8% are obtained in terms of the maximum absolute and RMS top floor displacement for FOBELBIC, while these reductions are obtained as 30.4% and 30.1% for the optimal BELBIC, respectively. Similarly, the optimal FOBELBIC results in an average reduction of 42.6% and 39.4% in terms of the maximum absolute and RMS top floor acceleration, while these reductions are given as 37.9% and 30.5%, for the optimal BELBIC, respectively. Consequently, the superiority of the FOBELBIC over the BELBIC is concluded in the reduction of maximum and RMS seismic responses.

Key Words
active mass damper; brain emotional learning-based intelligent controller; fractional-order controller; structural control; teaching-learning-based optimization algorithm

Address
Abbas-Ali Zamani: Department of Electrical Engineering, Technical and Vocational University (TVU), Tehran, Iran
Sadegh Etedali: Department of Civil Engineering, Birjand University of Technology, P.O. Box 97175-569, Birjand, Iran

Abstract
Understanding and analysing the behaviour and response of historical structures in the face of climate changes and environmental conditions is of utmost significance for their preservation. There are several structural hazards associated with climate and hydrology changes in the region, including the settlement of piers, the rotation of piers, and temperature changes. The present study investigates the experimental and numerical structural behaviour of skewed and non-skewed Persian brick masonry barrel vaults under various conditions. The external loading conditions included pier rotation in five modes, settlement, and temperature variations in four states. Initially, the experiments extracted the mechanical properties of the scaled materials. Then, three semi-circular brick barrel vaults were tested with gravitational loads. The outcomes were used to develop and validate the finite element model. Following the development of the finite element model, numerical and parametric studies were conducted on the effect of the aforementioned structural hazards on the response of brick masonry barrel vaults with various Persian geometries (semi-circular, drop pointed, and four-centred), angles of skew (0, 15, 30, and 45 degrees), and dimensional ratios. According to the findings, the fragility of masonry materials makes historical structures susceptible to failure under different loading. A brick barrel vault fails in the presence of minor rotation and settlement of the piers. The four-centred geometric shape has the lowest performance among the seven Persian geometries; therefore, its health monitoring and retrofitting should be prioritised. In Isfahan, Iran, temperature variations, particularly during the warm seasons, cause critical conditions in such structures.

Key Words
experimental study; finite elements method; masonry materials; Persian barrel vaults; structural hazards

Address
Saeid Sinaei, Esmaeel Izadi Zaman Abadi and Seyed Jalil Hoseini: Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

Abstract
This paper presents findings from an experimental study that was focused on evaluating the use of Forta-Ferro (FF) and Polyvinyl Alcohol (PVA) fibers on the response of moderate and special ductility beams under load cycles. For this reason, eight full-scale specimens, identical in geometry, were subjected to gradual cyclic loading. The specimens included two plain concrete beams with medium and special ductility, three beams with medium ductility and stirrup spacing of one-quarter the effective depth (d/4) and three beams with special ductility, and stirrup spacing of one-half the effective depth (d/2), strengthened with FF and PVA fibers separately. The use of fibers was aimed at reducing the amount of shear reinforcement in flexural members. Here, the variation of parameters including the maximum strength, ultimate strength, stiffness, ductility, damage index, energy dissipation, and equivalent damping was studied. Utilizing FF and PVA fibers improved the performance in beams with moderate ductility when compared to those beams with special ductility. Therefore, in special ductility beams, fibers can be used instead of crossties and in moderate ductility beams, fibers can be added to reduce the ratio of shear reinforcement. Furthermore, increasing the stirrup spacing in the moderate ductility beams from d/4 to d/2 and adding 0.6% FF or 1.5% PVA fibers resulted in behavior similar to those of the moderate ductility beam.

Key Words
cyclic loading; fiber-reinforced concrete; Forta-Ferro fiber; polyvinyl alcohol fiber; RC beams

Address
Hamed Rajabzadeh Gatabi: Department of Civil Engineering, Faculty of Engineering, Eastern Mediterranean University, Famagusta, North Cyprus, via Mersin 10, Turkey
Habib Akbarzadeh Bengar: Department of Civil Engineering, University of Mazandaran, Babolsar, Iran
Murude Celikag: Department of Civil Engineering, Faculty of Engineering, Eastern Mediterranean University, Famagusta, North Cyprus, via Mersin 10, Turkey

Abstract
This research aims to assess the behavior of reinforced concrete (RC) residential buildings when moment-resisting frames (MRFs) are used as the lateral resisting system. This investigation was conducted using MIDAS Gen v.19.0. Buildings with various plan footprints (Square, Rectangular, Circular, Triangular, and Plus-Shaped), and different heights (15 m, 30 m, 45 m, and 60 m) are investigated. The defined load cases, the equivalent static lateral load pattern, and the response spectrum function were defined as stated by the American Standard (ASCE 7-16), the 1997 Uniform Building Code (UBC97), the Egyptian Code for Loads (ECP-201), and the European Standard (EC8). Extensive comparisons of the results obtained by the different codes (including the story displacement, the story drift, and the base shear) were undertaken; to assess the response of moment-resisting multi-story framed buildings under lateral loads. The results revealed that, for all study cases under consideration, both ECP-201 and EC8 gave smaller base shear, displacement, and drift by one third to one fourth, around one fourth, around one fifth, respectively for both the ELF and RSA methods if compared to ASCE 7-16 and UBC97.

Key Words
buildings; codes; dynamic analysis; earthquake/seismic analysis; finite element method (FEM); reinforced concrete (RC) structure; space structure; static analysis; structural design

Address
Ahmed Ibrahim, Ibrahim El-Araby, Ahmed I. Saleh and Mohammed Shaaban: Department of Civil Engineering, Faculty of Engineering, Delta University for Science and Technology, Gamasa, Egypt

Abstract
Since the first family of structure-dependent methods can simultaneously integrate unconditional stability and explicit formulation in addition to second order accuracy, it is very computationally efficient for solving inertial problems except for adopting auto time-stepping techniques due to no nonlinear iterations. However, an unusual stability property is first found herein since its unconditional stability interval is drastically different for zero and nonzero damping. In fact, instability might occur for solving a damped stiffness hardening system while an accurate result can be obtained for the corresponding undamped stiffness hardening system. A technique of using a stability factor is applied to overcome this difficulty. It can be applied to magnify an unconditional stability interval. After introducing this stability factor, the formulation of this family of structuredependent methods is changed accordingly and thus its numerical properties must be re-evaluated. In summary, a large stability factor can result in a large unconditional stability interval but also lead to a large relative period error. As a consequence, a stability factor must be appropriately chosen to have a desired unconditional stability interval in addition to an acceptable period distortion.

Key Words
damped stiffness hardening systems; stability factor; stability property; structure-dependent method

Address
Shuenn-Yih Chang: Department of Civil Engineering, National Taipei University of Technology, Taipei 10608, Taiwan, Republic of China
Chiu-Li Huang: Fu Jen Catholic University, New Taipei City 242062, Taiwan, Republic of China

Abstract
In many fiber concrete beams with Carbon Fiber Reinforced Polymer (CFRP), debonding occurs between the carbon sheets and the concrete due to the low strength of the bonding resin. A total of 42 fiber concrete beams with a cross-section of 10x10 cm with a span length of 50 cm are fabricated and retrofitted with CFRP and subjected to a 4-point bending test. Graphene Oxide (GO) at 1, 2, and 3 wt% of the resin is used to improve the mechanical properties of the bonding resins, and the effect of length, width, and the number of layers of CFRP and resin material are investigated. The crack pattern, failure mode, and stress-strain curve are analyzed and compared in each case. The results showed that adding GO to polyamine resin could improve the bonding between the resin and the fiber concrete beam. Furthermore, the optimum amount of nanomaterials is equal to 2% by the weight of the resin. Using 2% nanomaterials showed that by increasing the length, width, and number of layers, the bearing and stiffness of fiber concrete beams increased significantly.

Key Words
carbon fiber; epoxy resin; fiber concrete beams; graphene oxide; retrofitting; strengthening

Address
Mohammad Reza Halvaeyfar, Ehsanollah Zeighami, S. Mohammad Mirhosseini: Department of Civil Engineering, Arak Branch, Islamic Azad University, Arak, Iran
Ali Hassani Joshaghani: Department of Chemical Engineering, Arak Branch, Islamic Azad University, Arak, Iran

Abstract
In this study, a new type of self-centering beam-column joint with tapered steel plate links is proposed. Firstly, mechanical property of the basic joint (with the prestressed steel strands only, to provide the self-centering ability) and the combined joint (with both the prestressed steel strands and tapered steel plate links, to provide self-centering and energy dissipation simultaneously) is theoretically analyzed. Then, three joints with different dimensions and combinations of tapered plate links are designed and tested through a series of quasi-static cyclic loading tests. Test results show that a nearly bilinear elastic moment-rotation relationship for the basic joint is obtained. With the addition of tapered steel plate links, typical flagshape hysteretic curves are obtained, which indicates good self-centering and energy dissipating ability of the combined joint. By installing multiple tapered plate links, stiffness and bearing capacity of the beam-column joint can be enhanced. The theoretical moment-rotation relationships agree well with the test results. A simplified macro model of the proposed joint is developed using OpenSees, which simulates reasonably well its hysteretic behavior.

Key Words
macro model; moment-rotation relationship; prestressed steel strands; self-centering beam-column joint; tapered plate link

Address
Liusheng He: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China; Department of Disaster Mitigation for Structures, Tongji University, Shanghai 200092, China
Yangchao Ru, Haifeng Bu: Department of Disaster Mitigation for Structures, Tongji University, Shanghai 200092, China
Ming Li: Department of Civil Engineering, Suzhou University of Science and Technology, Suzhou 215009, China

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