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inelastic cyclic behaviour of steel tubes infilled with rubberised alkali-activated concrete

ENGINEERING structures 2025年 325卷

作者： Elghazouli, A. Y. Elzeadani, M. Bompa, D. V. Imperial Coll Dept Civil & Environm Engn London England Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Peoples R China Univ Surrey Dept Civil & Environm Engn Guildford England

This study examines the lateral cyclic response of square steel tubes infilled with rubberised alkali-activated concrete through experimental investigations and complementary numerical assessments. The tests include steel members infilled with concrete incorporating up to 60% volumetric crumb rubber replacement of total natural aggregates and subjected to co-existing axial load levels of up to 20% of the cross-section axial capacity. Detailed numerical simulations are also carried out to provide further insights into the behaviour of the test specimens as well as to validate representative pushover procedures which are used for subsequent parametric evaluations. Key material, geometric and loading parameters are considered, including the rubber content, concrete infill strength, steel yield strength, tube cross-section slenderness, and applied axial load ratio. The experimental results, including those from detailed digital image correlation measurements, are used alongside those from numerical simulations, to assess salient response parameters related to the stiffness, capacity, and ductility of the composite members. It is shown that, despite the relatively low levels of confinement typically mobilised in rectangular tubes, the increase in rubber content can offer an enhancement in inelastic parameters such as the plastic hinge length and deformation ductility, depending on the specific cross-section properties. The results also indicate that alkali-activated concrete materials can be effectively used in infilled tubes, provided that the observed lower stiffness, when compared to conventional concrete, is accounted for in design. Finally, the adequacy of typical analytical expressions, used in codified guidance for evaluating the stiffness and capacity, is examined, and adjustments are proposed where necessary in support of practical design procedures.

关键词： concrete-filled steel tubes Composite members Rubberised concrete Alkali-activated materials inelastic cyclic response Hysteretic behaviour

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Collapse Potential of an Existing Reinforced concrete Bridge Structure

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APPLIED SCIENCES-BASEL 2025年第7期15卷 3500-3500页

作者： Yilmaz, Zeynep Kircil, Murat Serdar Yildiz Tech Univ Dept Civil Engn TR-34220 Esenler Turkiye

This article presents the results of a study conducted to obtain the fragility curves of an existing reinforced concrete highway bridge in Kocaeli, Turkey, to investigate the collapse potential. Bridges are key components of transportation systems, providing convenient and efficient access to different locations. However, these structures are susceptible to forces that can cause significant damage in the event of seismic activity. Thus, the fundamental target of designing earthquake-resistant bridges is to ensure that they can remain functional at an acceptable level during seismic activity. At least, they are expected to survive strong earthquakes without collapse. Turkey is a country located on active fault lines and has experienced devastating earthquakes in the past. This high earthquake risk requires the design and construction of bridges that are a critical part of the transportation infrastructure having adequate safety levels so that the collapse risk can be minimized. Therefore, damage estimation of bridges is an important part of earthquake preparedness and the response plans that will be followed immediately after earthquakes. In this study, the fragility curves of an existing reinforced concrete highway were obtained to investigate the collapse potential. The interstory drift limits related to the performance levels defined by the Turkish Bridge Seismic design Code 2020 were determined by the incremental dynamic analysis method, and fragility curves were obtained using 10 different earthquake records based on these determined limits. The results showed that the target performance level Uninterrupted Occupancy and Collapse Prevention performance level requirements, as defined by the Turkish Bridge Seismic design, were not met, and the Collapse Probability is %100.

关键词： fragility curves RC bridges structural damage performance level

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Influence of Effective Stiffness on Seismic response of RC Frame Building with Shear Walls

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JOURNAL OF VIBRATION ENGINEERING & TECHNOLOGIES 2024年第2 supplement期12卷 1635-1645页

作者： Reddy, K. K. K. Haldar, Putul Indian Inst Technol Ropar Dept Civil Engn Rupnagar 140001 Punjab India

Purpose This article aims to explore the implication of effective stiffness modifiers of structural elements on the seismic performance of high-rise RC frame buildings with shear walls. Contribution and method Effective stiffness of structural elements i.e., beams, columns, shear walls etc. plays a pivotal role in the seismic evaluation of Reinforced concrete (RC) shear wall buildings which are predominantly considered through the use of stiffness modifiers in Indian design standards like various national design standards worldwide. The reduction in stiffness of the structural members is mainly due to crack formation in members due to shrinkage, creep, bond-slip of the reinforcement, etc. which further aggravates due to large inelastic deformation caused by seismic events. stiffness modifiers for various structural members i.e., beams and columns have been recommended in revised Indian seismic standards (BIS inIS 1893 (Part 1)-2016 Indian Standard criteria for earthquake resistant design of structures, part 1: general provisions and buildings (fifth revision). Bureau of Indian Standards, New Delhi, 2016), however specific guidelines for the same are missing for RC shear walls. This paper presents a comprehensive review of the available effective stiffness recommendation by various national seismic design standards viz., ASCE (ASCE-41 in ASCE/SEI 41-17, seismic evaluation and retrofit of existing buildings. American Society of Civil Engineers, Reston, 2017), Eurocode (design of structures for earthquake resistance-part 1: general rules, seismic actions, and rules for buildings, 2005), New Zealand code (NZS in NZS 3101:2006 New Zealand Standard concrete structures Standard, 2006) and assess the influence of effective stiffness on seismic evaluation of high-rise RC shear wall buildings. It is observed that a significant difference in peak strength is observed with variation in stiffness modifiers of beam and column, whereas their peak strength is not significantly sens

关键词： RC shear wall Effective moment of inertia Stiffness modifiers Seismic performance

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Seismic Pounding Effects of Typical Midrise Reinforced concrete structures Subjected to Soil-Structure Interaction Effects

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JOURNAL OF STRUCTURAL ENGINEERING 2025年第2期151卷

作者： Oz, Ibrahim Kirsehir Ahi Evran Univ Dept Civil Engn TR-40100 Kirsehir Turkiye

In densely populated urban areas, construction spaces are often limited, resulting in insufficient separation between adjacent structures. This issue is compounded by soil-structure interaction (SSI), which significantly alters the dynamic response of buildings. Inadequate separation gaps can lead to increased seismic forces and interstory drift ratios (IDRs), potentially causing significant structural damage and resulting in the loss of life and property. Using inelastic time-history analyses with scaled ground motion records, this research investigated the rapid calculation of seismic gaps between adjacent structures, as well as the impact of SSI on seismic pounding forces and IDRs across different soil conditions, with comparisons made via fixed base. Nonlinear models of 8- and 10-story reinforced concrete (RC) structures, representative of the Turkish building stock, were analyzed in both standalone and adjacent scenarios. Ground motion records were scaled to match the seismic characteristics of Istanbul, a highly earthquake-prone region, and nonlinear time-history analyses were conducted in both horizontal directions simultaneously. This study primarily examined two scenarios. The first scenario involved a rapid assessment based on building height and soil conditions, which can be utilized during the design phase to prevent pounding between adjacent buildings and compared with gap separations calculated using more-complex formulas recommended by regulations. The second scenario addressed the additional shear forces resulting from pounding effects, which must be considered if pounding cannot be avoided. This study proposes a simplified method for determining seismic gaps, aiding practical application for field engineers. This study found that simultaneously considering both SSI and pounding significantly alters dynamic behavior in terms of maximum IDRs and acceleration demands, especially in shorter and lighter structures.

关键词： Soil-structure interaction Seismic pounding earthquake engineering Direct time-history analysis

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response modification factor evaluation for vertically irregular MRF buildings

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PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-structures AND BUILDINGS 2023年第7期177卷 618-632页

作者： Ahmed, Momen Mohamed M. Abdo, Mohamed Abdel-Basset Mohamed, Waleed Abo El-Wafa Assiut Univ Fac Engn Civil Engn Dept Assiut Egypt

Most design codes evaluate the non-linear seismic performance of structures using the response reduction/modification factor (R). The value of R is sensitive to a variety of factors in terms of overall ductility and over-strength. In this work, actual R values were assessed for vertical irregularity cases for reinforced concrete bare buildings with moment-resisting frames (MRFs). A significant relationship between R and the vertical irregularity index, calculated from the relative stiffness between adjacent storeys, was derived. Three-dimensional numerical modelling was carried out for soft storey and setback irregularity scenarios using Etabs. Modal pushover analysis was used to obtain the inelastic seismic capacity. It was found that vertically irregular buildings have weak inelastic seismic capacities compared with regular buildings. So, before the design stage, R should be scaled down by 15-40% for single and combined vertical irregularity scenarios. structures with a combined asymmetric setback with a soft ground storey were found to have the worst R value and R was sensitive to the vertical irregularity index (V-tm) that has R-squared of 80%. So, the vertical irregularity index can be used to specify the allowable vertical irregularity ratio, location and combination of vertical irregularities for each seismic zone.

关键词： concrete structures ductility dynamics earthquake modal non-linear pushover analysis modification factor (R) over-strength response reduction seismic engineering structural analysis vertical geometric irregularity

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Impact of Various High Intensity earthquake Characteristics on the inelastic Seismic response of Irregular Medium-Rise Buildings

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APPLIED SCIENCES-BASEL 2024年第21期14卷 9740页

作者： Pachla, Filip Tatara, Tadeusz Aldabbik, Waseem Cracow Univ Technol Fac Civil Engn PL-31155 Krakow Poland Cracow Univ Technol Doctoral Sch PL-31155 Krakow Poland

In the twenty-first century, the seismic design of buildings seems to have become a fully recognized topic. There are guidelines and standards which should be taken into account by designers in seismic areas. designers using modern international guidelines have ascertained that the behavior of structures is not as expected. New challenges in the construction industry result in the construction of structures with new, unusual shapes. These are structures that do not meet the assumptions of safe construction in seismic areas. Contemporary buildings are also characterized by their irregular distribution of structural elements. Such solutions are not beneficial from the point of view of seismic engineering and can lead to reduced dynamic resistance and damage in such structures. In this paper, a five-storey, irregular-shaped reinforced concrete (RC) building model was subjected to different earthquakes with varying magnitudes, PGA (peak ground acceleration) and PGV (peak ground velocity) values, and durations of the intense shock phase. Once the model was verified using previous in situ measurements, the building model was subjected to five earthquakes. A numerical nonlinear analysis of the building was performed using a verified FEA (finite element analysis) model in the time domain through non-linear time history analysis with the Broyden-Fletcher-Goldfarb-Shanno (BFGS) method. The building's dynamic properties were measured using various methods of excitation. The model was influenced, among others, by two far-field representative events caused by the last earthquake in Turkey, which resulted in strong ground motion. The analysis results identified the locations of structural damage and allowed for the assessment of the structure's dynamic resistance. The results of the calculations prove that the duration of the intensive phase of extortion is one of the reasons for building damage in earthquake-prone areas. Building damage occurs with earthquakes that are character

关键词： RC irregular structure dynamic model earthquake time history analysis dynamic response damage

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Multiscale Numerical Study of Enhanced Ductility Ratios and Capacity in Carbon Fiber-Reinforced Polymer concrete Beams for Safety design

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POLYMERS 2025年第2期17卷 234-234页

作者： Maidi, Moab Sherzer, Gili Lifshitz Gal, Erez Ben Gurion Univ Negev Dept Civil & Environm Engn IL-8410501 Beer Shev Israel Braude Coll Engn Dept Civil Engn IL-2161002 Karmiel Israel Ariel Univ Dept Civil Engn IL-4070000 Ariel Israel

Rigid reinforced concrete (RC) frames are generally adopted as stiff elements to make the building structures resistant to seismic forces. However, a method has yet to be fully sought to provide earthquake resistance through optimizing beam and column performance in a rigid frame. Due to its high corrosion resistance, the integration of CFRP offers an opportunity to reduce frequent repairs and increase durability. This paper presents the structural response of CFRP beams integrated into rigid frames when subjected to seismic events. Without any design provision for CFRP systems in extreme events, multiscale simulations and parametric analyses were performed to optimize the residual state and global performance. Macroparameters, represented by the ductility ratio and microfactors, have been analyzed using a customized version of the modified compression field theory (MCFT). The main parameters considered were reinforcement under tension and compression, strength of concrete, height-to-width ratio, section cover, and confinement level, all of which are important to understand their influence on seismic performance. The parametric analysis results highlight the increased ductility and higher load-carrying capacity of the CFRP-reinforced tested component compared to the RC component. These results shed light on the possibility of designing CFRP-reinforced concrete components that could improve ductile frames with increased energy dissipation and be suitable for applications in non-corrosive seismic-resistant buildings. This also shows reduced brittleness and enhancement in the failure mode. Numerical simulations and experimental results showed a strong correlation with a deviation of about 8.3%, underlining the reliability of the proposed approach for designing seismic-resistant CFRP-reinforced structures.

关键词： ductility ratio enhancement seismic performance CFRP high corrosion resistance energy dissipation performance limited displacement structural capacity ductility index

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Influence of masonry infills on blast response of earthquake-resistant reinforced concrete buildings

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structures 2023年 50卷 908-924页

作者： Baddipalli, Shivalinga Kulariya, Mahipal Saha, Sandip Kumar Indian Inst Technol Mandi IIT Mandi Sch Civil & Environm Engn Kamand 175075 Himachal Prades India

The present study investigates the influence of masonry infill strength on the blast performance of earthquake-resistant reinforced concrete (RC) buildings under surface burst. These buildings, having three-dimensional RC moment resisting frames, are designed to withstand different levels of seismic demand. The masonry infills are modelled as an equivalent diagonal strut using a macro-modelling approach to account for its in-plane strength and stiffness. The blast-induced loads are directly applied as nodal loads on the exposed beam-column joints, and nonlinear time history analyses are then performed to obtain the various response quantities such as top floor displacement, interstory drift ratio, and base shear. The comparative matrices of various response quantities are developed to examine the effect of infill's nonlinearity. Further, the influence of the infill strength and seismic design level of the considered buildings is probabilistically assessed by developing the blast fragility curves using an uncoupled approach. It is observed that the consideration of infill's nonlinearity influences the blast response up to a certain scaled distance only. Moreover, increasing the infill strength does not necessarily enhance the blast performance;however, designing the building to higher seismic demand results in improved blast per-formance. In addition, proper insight into seismic design level and infill strength of any RC building is required prior to plan and design them with suitable blast-mitigation measures.

关键词： Blast Fragility Curve Blast response earthquake resistant design Infill Strength Multi-Hazard Nonlinear Infill Seismic Demand Surface Burst

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Seismic response control of shear frame structure using a novel tuned-mass type composite column

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ENGINEERING structures 2025年 322卷

作者： Fang, Xiaojun Hao, Hong Bi, Kaiming Ding, Hao Yang, Xiaoqiang Song, Jian Cao, Yongsheng Guangzhou Univ Earthquake Engn Res & Test Ctr Guangzhou 510006 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong 999077 Peoples R China Curtin Univ Ctr Infrastruct Monitoring & Protect Sch Civil & Mech Engn Kent St Perth WA 6102 Australia Fuzhou Univ Coll Civil Engn Fuzhou 350116 Peoples R China

concrete filled steel tube (CFST) column is widely applied in shear frame structure in seismic-prone area owing to its superior earthquake resistant performance. However, CFST column might still suffer damage under a severe earthquake. This paper proposes a novel tuned-mass type column-in-column (CIC) system to improve the seismic behavior of the CFST column and hence protect the structure. The CIC system is formed by splitting the CFST column into a primary column and a secondary column, while the overall cross section area and hence the load- bearing capacity is not changed. By optimally selecting the springs and dashpots to interconnect the two columns, the CIC can act as a non-conventional tuned mass damper (TMD) to reduce seismic vibrations of structures. To demonstrate the proposed CIC concept, a single-story and a five-story frame structure with and without control are designed. Nonlinear time history analyses are performed to study the seismic responses of these structures considering different seismic design levels, earthquake ground motions and CIC control schemes. Numerical results show that the CIC system can effectively reduce the seismic induced story acceleration, displacement and drift ratio of frame structures with the reduction ratios approximately between 21 % and 30 %, and the ratios on reducing the base shear force and bending moment are between 27 % and 31 %, and between 34 % and 49 %, respectively. The proposed CIC control concept is a new solution for mitigations of seismic responses of CFST frame structures.

关键词： CFST frame structure Vibration control FE modelling Seismic response analysis Column-in-column

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Investigation of window opening effects on blast resistance of square reinforced concrete panels via numerical and machine learning-based methods

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structures 2025年 75卷

作者： Hua, Chaofeng Hao, Hong Wei, Jie Hao, Yifei Tianjin Univ Sch Civil Engn Tianjin 300350 Peoples R China Guangzhou Univ Earthquake Engn Res & Test Ctr Guangzhou 510405 Peoples R China Curtin Univ Ctr Infrastructural Monitoring & Protect Sch Civil & Mech Engn Kent St Bentley WA 6102 Australia Hebei Univ Technol Sch Civil & Transportat Engn Tianjin Key Lab Prefabricated Bldg & Intelligent C Tianjin 300401 Peoples R China

To accommodate functional requirements in modern buildings, such as door and window installations, structural panels used as building facade often feature pre-fabricated openings. Studying the dynamic response of reinforced concrete (RC) structural panels with openings offers valuable insights into the effectiveness of design strategies. This paper aims to investigate the behaviour of two-way square RC panels with openings subjected to blast loads. Firstly, numerical simulations were conducted to analyse the blast-resistant response of two-way square RC panels with window openings. The results showed that the maximum displacement and damage of the panels with openings were significantly lower compared to solid panels. This reduction is primarily due to the fact that part of the blast waves passes through the opening, thereby decreasing the blast load on the panel. Furthermore, parametric studies indicated that panels with square opening at center exhibited a lower blast response as compared to openings of other shapes and at other locations. Finally, a predictive model for the normalized maximum displacement of RC panels with openings under blast loading was developed using machine learning techniques, providing a reliable tool for future design applications.

关键词： Reinforced concrete (RC) panels Window opening Numerical blast test Predictive model

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