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This paper suggests a novel lateral load-resisting solution for RC (high-rise reinforced concrete) frames using superelastic SMA wires as friction dampers. The suggested SMA-friction damper has some advantages, such as an easy-to-configure and affordable application, in addition to being able to control the frictional energy dissipation components mechanism in line with the design procedure based on the suggested effectiveness thanks to its self-centering SMA wires. With the least amount of SMA use, it may produce hysteretic behavior and an intense tendency for self-centering. The research used two distinct design modes--common and with the recommended damper--to construct two tall, 18- and 22-story RC frames. Ten far-field earthquakes were studied using OpenSees software in a nonlinear time history fashion. Eighteen and twenty-two-story reinforced concrete frame high-rises were designed in two distinct ways: normally and with the recommended damper. Aside from the major advancement in ductility, the lateral strength and stiffness gave an exceptional capacity for self-centering, resulting in a substantial decrease in most drift and persistent distortions in the structure. The study's findings showed that the suggested damper may improve the RC frame's structural performance while using the fewest bracing spans and money. [ABSTRACT FROM AUTHOR]

The dual system buildings consisting of Unreinforced Masonry (URM) Shear Walls and Reinforced Concrete (RC) Frames are part of the existing buildings patrimony in Romania. Being a seismic zone, the qualitative evaluation of this type of structural system represents both a specific and a holistic approach. Thus, the in-depth knowledge of the initial situation of the building, including the level of degradation as well as the causes that produced these damages represents the present study. Also, notions such as: the level of degradation importance, the level of damage (destruction), the correction coefficient of the bending stiffness, the level of knowledge, the evaluation methodology are interpreted, in order to establish a score of the degree of seismic configuration of the lateral system and degree of structural damage. This information leads to the establishment of the seismic risk class of the analyzed building and to the establishment of the intervention works necessity. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on the seismic behavior of RC frames with masonry infills retrofitted by precast Ultra-Lightweight Insulated Cementitious Composites plates under cyclic loading. The objective was to provide an easy retrofit approach for concurrent seismic behavior and energy efficiency upgrading of existing RC frames. Three scaled RC frames were built including a control frame and two frames with different retrofit schemes. The experiments were conducted to investigate the effect of different retrofit schemes over the failure patterns, hysteretic curves, energy dissipation abilities, skeleton curves, and characteristic loads and displacements. The retrofitted RC frames provided higher carrying capacities, energy dissipation abilities, and displacement ductility. Retrofit schemes proposed can prevent severe damage of masonry infills, and alleviate shear failure of columns significantly. Based on the test results, ULICC plates influenced on the flexural moments of columns and beams, and base shear distribution were analyzed. Interactions between retrofitted infills and surrounding frames were discussed. A theoretical model based on equivalent strut was proposed to obtain initial lateral stiffness and carrying capacity of retrofitted RC frames. The experiments have demonstrated that precast ULICC plates retrofit strategy can enhance the seismic performances under low-frequency cyclic loading. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Irregular reinforced concrete framed buildings are peculiar and their seismic response is difficult to predict using simplified approaches. The irregularity in structural configuration is characterized by cross-sectional area reduction of the columns along the height, in-elevation and in-plan irregular distribution of the masses, complex floor geometry or floor geometry variation along the height. This study analyses the seismic response of several four-storey buildings with different types of irregularities, namely in-elevation floor height and floor geometry variation. Additionally, responses of both seismically designed and gravity load designed structures are compared for each geometry considered. A numerical model accounting for non-linear flexural and shear response of the structure is developed, aimed at conducting non-linear incremental dynamic analyses. The results are discussed in terms of inter-storey drift, floor acceleration profiles, fragility functions and floor response spectra. A significant influence of the irregularity on floor accelerations and displacements was observed, as well as on the spectral acceleration at collapse, mainly caused by mass and stiffness variation along the height. On the other hand, no significant influence was detected on failure modes. [ABSTRACT FROM AUTHOR]

Building code implementation in developing countries is a serious concern due to poorly regulated construction practices. Deficiencies in terms of material strength and structural detailing are found the most in reinforced concrete frames in Pakistan. This paper presents the results of quasi-static cyclic tests performed on reduced-scale RC frames with and without beam-column joint detailing and considering normal and low-strength concrete respectively. Fragility functions and loss curves for the standard/sub-standard frames were derived using an experimentally validated numerical model. Furthermore, the existing RC frames building stock was rehabilitated with various configurations of steel bracing i.e. one way diagonal, one way eccentric, two way diagonal, two way eccentric and concentric. The developed fragility and loss curves for the rehabilitated frames confirmed that the two way diagonal steel bracing system outclasses the other types. Moreover, inter-story drift limits for as-built and rehabilitated frames were proposed under design base earthquakes and maximum considered earthquakes. Maximum considered earthquakes pushed the ductile as-built frame further than the moderate damage state, thus rehabilitation after such an event will be required for the structure. The presented results will help in seismic risk assessment, decision-making and public awareness. [ABSTRACT FROM AUTHOR]

An experimental study was carried out to contribute to the rather limited data on the out-of-plane (OOP) behavior of masonry infills in reinforced concrete (RC) frames strengthened with the wall post and the textile-reinforced mortar (TRM). For this purpose, one unreinforced specimen served as the control, one specimen was reinforced with the wall post, and two specimens were reinforced with the TRM. They were fabricated and subjected to cyclic OOP loading until a drift ratio of 6%. Load and displacement values were recorded, and the research team discussed the failure mechanisms of the specimens. Results showed that the application of the wall post had the highest efficiency as it increased the load by about 3 times, while this value for TRM-strengthened walls was only 1.5. Strengthening modified the cracking, shifting it towards the middle parts of the wall, changing it from a brittle to a failure mode. Comparison of the envelope curves of specimens revealed significant improvements. The ultimate displacement and energy absorption capacity for the specimen reinforced with the post wall increased by 30% and 300% respectively. Similarly, for TRMstrengthened specimens, these values were 48% and 100%. [ABSTRACT FROM AUTHOR]

Technical investigations carried out after the devastating earthquakes in Turkey in the last 25 years show that one of the main causes of damage to reinforced concrete structures is reinforcement bar corrosion. The deterioration caused by reinforcement corrosion in reinforced concrete elements reduces the parameters that define the performance level of the structure, such as ductility, stiffness, bond-slip relationship, load carrying capacity, and energy absorption capacity. Therefore, determining the specified performance levels of reinforced concrete structures exposed to corrosion before any seismic activity occurs is of great importance in preventing loss of life and property. Cross-section behavior in reinforced concrete structures represents the load-bearing element behavior In order to accurately determine the section behavior, the Moment-Curvature relationship must be defined. In this study, the structural behavior of reinforced concrete frames exposed to corrosion was examined experimentally and analytically. For this purpose, 4 of the 5 reinforced concrete frame specimens constructed were corroded at different ratios using the accelerated corrosion method. After the corrosion process was completed, in the experimental part of the study, all specimens were tested under the effect of a 20% constant axial load and reversal-cyclic loading. In the analytical study, as a result of the cross-sectional analyzes carried out by taking into account the materialmechanical properties changing with the effect of corrosion, it was determined that the calculated moment values were in high predicted with the experimentally measured moment values. [ABSTRACT FROM AUTHOR]

Predicting the seismic response of masonry-infilled (MI) RC frames holds immense importance due to the significant influence of masonry on the structural performance. Despite numerous studies delving into the seismic behavior of these frames, their complex interaction of masonry infills and RC frame presents ongoing challenges for researchers, designers, and standards committees. Although numerous studies have been conducted to investigate the seismic behavior of masonry-infilled reinforced concrete frames, its complex behavior poses a challenge to researchers, designers, and the specification-making committees. In recent years, several national codes have been revised to include the estimation of the stiffness of reinforced and nonreinforced masonry walls and have provided guidelines for the modeling and analysis of structures considering MI. This article aims to provide a comprehensive review of how infilled masonry walls impact the seismic performance of RC frames, drawing comparisons with codal provisions. The focus lies on scrutinizing experimental, numerical, and analytical studies that explore in-plane and out-of-plane behaviors. Factors like masonry strength, stiffness, area of openings, stiffness degradation, energy dissipation capacity, and damage patterns are thoroughly examined. Key findings with critical implications are highlighted, shedding light on potential future research directions in this crucial field. [ABSTRACT FROM AUTHOR]

The structural behavior prediction of the multistory reinforced concrete (RC) buildings with masonry infill walls (MIWs) during earthquakes is challenging. This paper presents a nonlinear macromodeling strategy seeking a simple, reliable, and low-cost computational analysis of the multistory RC buildings that comprise MIWs, and that use frames or shear walls (SWs) for resisting the lateral load. The strategy employed four plastic hinge (PH) models for tracking the deformations (flexural, shear, and torsion) of the frame elements and joints, a multilinear plastic link for modeling the MIW, and a nonlinear multilayer shell element for modeling the SW. A flexural PH model characterized by discretization into fibers, a recommended position, and an iterative estimating for the PH length using a distinct formula for each loading level was proposed. This strategy was validated through eleven macromodels investigating four bare frames, four MIWs frames, and a SW where the average ultimate lateral load error was 9.2%, 3.6%, and 0.4%, respectively. Finally, the structural behavior of real ten-story buildings with/without MIWs was investigated. The results showed that the MIWs increased the shear capacity and the lateral stiffness with an average of 44.3% and 118.6%, respectively. Also, both the frames buildings with MIWs and the bare SWs buildings showed approximately equal lateral load capacities. Local damages in the RC vertical elements and yielding of the MIWs were recorded simultaneously. However, the MIWs yielding (and also failure) occurred earlier for the frames buildings compared with the SWs buildings in which the stress was relaxed in their MIWs. [ABSTRACT FROM AUTHOR]

The use of lateral bearing systems to rehabilitate reinforced concrete frames has been one of the most important research topics in structural engineering. Non-uniform Slit Dampers (NSD), as well as Bar dampers, are two types of novel yielding dampers whose effects on reinforced concrete structures have been evaluated in this research. In this research, three experimental samples with a one-third scale were constructed to assess the effect of the presence of NSD and Bar damper in reinforced concrete frames. Also, 16 numerical models were created to evaluate the number of used dampers in experimental specimens in order to determine the optimal mode of using these dampers. Seismic parameters of stiffness, ultimate strength, ductility, and energy dissipation capacity were investigated in this research. The research results showed that the use of lateral bearing systems with NSD and bar dampers can have a significant impact on the seismic performance of reinforced concrete moment resisting frames. Also, in the numerical models that were made using ABAQUS software, it was concluded that the use of a smaller number of dampers compared to the experimental models can still improve the seismic parameters of the system while the cyclic capacity of the system does not drop. [ABSTRACT FROM AUTHOR]

Abstract Fabric-reinforced cementitious matrix (FRCM) composites, also known as textile-reinforced mortars (TRMs), represent a new advancement in structural repair and reinforcement technology. Aiming to improve the energy efficiency and seismic performance of existing buildings, this research focused on the development of an FRCM system in combination with phase change materials (PCMs) and extruded polystyrene sheets (XPS) to achieve adequate mechanical and thermal properties for reinforced concrete (RC) and masonry structures. Accordingly, the in-plane behaviour of five FRCM-strengthened RC frames with hollow-brick wall infill was tested under cyclic loading to investigate the improvement in earthquake resistance. The system was comprehensively evaluated by calculating hysteresis curves; comparing the lateral stiffness, ductility, and energy dissipation capacity; measuring the deformations of the specimens; and analysing the failure modes mechanically. Finally, it was proved that this novel integrated approach could significantly enhance the mechanical and seismic performance of masonry-infilled RC frames.

The aim of this paper is to determine the optimum amount of carbon fiber-reinforced polymer (CFRP) for strengthening columns in reinforced concrete (RC) frames suffering from weak column/strong beam condition. In this study, several parameters affecting the behavior of these frames including the level of columns' axial force, Length and thickness of CFRP laminates are analyzed numerically. Nonlinear static analyses, employing three-dimensional finite element models are performed by an implicit method on 98 model frames having different length and thickness of CFRP and axial load. The results revealed improvements in both strength and ductility of the system when the columns of higher axial load were strengthened; while in strengthening of the columns under lower levels of axial load, the influence of CFRP was only observed in the strength of the system. An optimization method which takes into account the cost of the utilized material and the strength of the system was proposed, and the optimum CFRP length and thickness were determined. [ABSTRACT FROM AUTHOR]

Fabric-reinforced cementitious matrix (FRCM) composites, also known as textile-reinforced mortars (TRMs), represent a new advancement in structural repair and reinforcement technology. Aiming to improve the energy efficiency and seismic performance of existing buildings, this research focused on the development of an FRCM system in combination with phase change materials (PCMs) and extruded polystyrene sheets (XPS) to achieve adequate mechanical and thermal properties for reinforced concrete (RC) and masonry structures. Accordingly, the in-plane behaviour of five FRCM-strengthened RC frames with hollow-brick wall infill was tested under cyclic loading to investigate the improvement in earthquake resistance. The system was comprehensively evaluated by calculating hysteresis curves; comparing the lateral stiffness, ductility, and energy dissipation capacity; measuring the deformations of the specimens; and analysing the failure modes mechanically. Finally, it was proved that this novel integrated approach could significantly enhance the mechanical and seismic performance of masonry-infilled RC frames. [ABSTRACT FROM AUTHOR]

This paper deals with multi-story buildings erected mostly in interwar period in seismic areas and designed for gravitational actions only. The typical structural system is reinforced concrete frames and masonry infills. A usual multi-story interwar structure was chosen in order to evaluate its seismic resilience. There were made in situ measurements for its dynamic characteristics. The numerical model was calibrated according to in situ measurements. There were proposed two methods of increasing the seismic resilience. First method consists in improving the resilience by reshaping without reinforcing. The second method is additional to the first. It consists in reinforcing infilled frames in order to take over seismic loads.

Buckling-restrained braces (BRBs) have proven to be a valuable earthquake resisting system. They demonstrated substantial ability in providing structures with ductility and energy dissipation. However, they are prone to exhibit large residual deformations after earthquake loading because of their low post-yield stiffnesses. In this study, the seismic response of RC frames equipped with BRBs has been investigated. The focus of this research work is on evaluating the effect of the BRB yielding-core length on both the maximum and the residual lateral deformations of the braced RC frames. This is achieved by performing inelastic static pushover and dynamic time-history analyses on three- and nine-story X-braced RC frames having yielding-core length ratios of 25%, 50%, and 75% of the total brace length. The effects of the yielding-core length on both the maximum and the residual lateral deformations of the braced RC frames have been evaluated. Also, the safety of the short-yielding-core BRBs against fracture failures has been checked. An empirical equation has been derived for estimating the critical length of the BRB yielding cores. The results indicated that the high strain hardening capability of reduced length yielding-cores improves the post-yield stiffness and consequently reduces the maximum and residual drifts of the braced RC frames.

Pin-supported (PS) walls represent a possible solution for the seismic retrofit of existing reinforced concrete (RC) buildings, enabling linearization of the frame deformation along its height and consequently inhibiting soft storey collapse mechanisms. The effectiveness of this rehabilitation technology is strongly related to the characteristics of the existing frames, especially to the vertical distribution of the frame storey lateral stiffness. Since a larger 1st storey lateral stiffness may lead to a detrimental structural response of the retrofitted system, an alternative solution obtained from removing the connecting link between the 1st floor of the existing building and the pin-supported wall is investigated in this paper. An analytical method is proposed to derive the distribution of the internal actions in a dual 2D RC frame-PS wall system without the link at the 1st floor level, considering both a linear and nonlinear behaviour of the frame. It emerges that some parameters describing the structure type can provide straightforward information on the suitability of this solution in the seismic retrofit of existing RC buildings. As a result, a simplified procedure has been derived to preliminarily define the retrofit system configuration and evaluate the maximum demand in the PS wall. Such a procedure is finally applied with reference to a frame representing a RC building and finite element model analyses are carried out for validation purposes. [ABSTRACT FROM AUTHOR]

This research investigated the relation between the main earthquake parameters by incorporating information about ground motions and the difference in the fundamental period. This difference in the fundamental period is one method of assessing structural damage because it can express potential damage from an earthquake. Three RC (3-, 9- and 12-story) frames have been analyzed under far-fault earthquake records using nonlinear dynamic analysis. Mathematical methods then were applied to assess the correlation between the difference in the fundamental period and the principle seismic parameters of PGA, a RMS , I a , I c , A95, ASI and VSI that have been extracted from the records. The best correlations as calculated by the Pearson correlation coefficient values were between I a , I c and VSI and the difference in the fundamental period. The Pearson coefficients for I a and I c were between 0.621 and 0.767, which signifies a strong correlation. Regression equations indicated new parameters ( I c VS ) with even higher Pearson coefficients of 0.757–0.782 between every parameter and the difference in the fundamental period. The very strong correlation between the newly achieved parameters and the fundamental period indicates that they are appropriate indices for estimating potential structural damage from an earthquake. [ABSTRACT FROM AUTHOR]

Purpose: The current study evaluates the seismic vulnerability of the Indian code, confirming RC frame buildings located in the most severe seismic Zone V of India using fragility analysis. Method: Two-, four-, eight-, and twelve-storey RC frame buildings are designed based on the stiffness of the uncracked section as per IS 1893:2002 and the effective section as per IS 1893:2016, respectively, using relevant Indian codes. The seismic vulnerability of all designed RC frames is investigated by carrying out a performance assessment using pushover analysis followed by fragility evaluation. The design of RC frame building based on elastic stiffness of effective section in linear seismic analysis indirectly enhances the strong column to weak beam (SCWB) ratio, and noticeable improvement in the failure mechanism and lateral responses of RC moment-resisting frame is observed. Results: The results of fragility analysis suggest that an RC frame designed based on the full elastic stiffness of uncracked section during linear analysis had more seismic fragility than a frame designed based on the elastic stiffness of the effective section. The estimated values of the response reduction factor (R) using the idealised capacity curve suggest that the Indian seismic code overrates the R factor for the RC frame designed based on the elastic stiffness of the uncracked section, which leads to the potentially risky estimation of the design seismic base shear on the lower side. Conclusion: The collapse probability of the RC frame designed using effective section as per revised seismic code is approximately 57 per cent less than the frame designed using gross section as per older seismic code. [ABSTRACT FROM AUTHOR]

The retrofit of infill walls in reinforced concrete frames is often employed to avoid out-of-plane failure caused by earthquakes. Additionally, some strengthening techniques also increase in-plane capacity of the infill. The interaction between in-plane and out-of-plane response of infill walls significantly influences their contribution to the dynamic behaviour of the structure and, consequently, the seismic response. In some cases, the beneficial increase of global stiffness and strength caused by the infill can be nullified by out-of-plane mechanism. On the other hand, an excessive increase of infill's strength can cause brittle failure of gravity load designed columns, due to local interaction. In this study, a numerical macro model is developed to simulate the interaction between in-plane and out-of-plane response of infill walls in gravity load designed reinforced concrete frames. An infilled portal frame is modelled, considering the case of un-reinforced infill and two types of retrofitted infill. Non-linear dynamic analyses are conducted and the seismic performances are evaluated depending on the type of the infill. [ABSTRACT FROM AUTHOR]

Nowadays, reducing greenhouse gases is a major global challenge. The CO2 emission has a remarkable contribution and reinforced concrete (RC) frames largely contribute to the emission of this gas. One method to reduce CO2 emission from the construction industry is the use of optimization methods in the structural design phase. No study has been conducted on the trade-off between structural cost and CO2 emission of RC frames with non-prismatic columns. Therefore, this paper presents the optimal design of RC frame with non-prismatic beams and non-prismatic columns to minimize the cost and CO2 emissions. The procedure is applied for RC frames and also for RC industrial frames with pitched roof. Design variables are taken as the dimensions of the cross sections of beams and columns, reinforcements of the beams and columns, compressive strength of the concrete as well as the tapered length for the non-prismatic elements. Optimal structural solutions are obtained utilizing the enhanced colliding bodies optimization algorithm. Here, designs based on minimizing CO2 emission are compared with the cost-based designs. Results show that in CO2-based design, the amount of CO2 is reduced by 3.8% in RC frames with a 6% increase in cost, and in the RC industrial frames with 1.3% increase in cost, the amount of CO2 can be reduced by 7%. [ABSTRACT FROM AUTHOR]

The seismic retrofit of the existing building heritage represents an urgent issue to be faced and innovative solutions which allow to overcome renovation barriers are needed. In this scenario, pin-supported (PS) walls represent an eligible solution, enabling linearization of the deformation of the frame along its height and inhibiting soft storey collapse mechanisms. The PS wall can be connected to the existing building from outside, thereby avoiding disruption to occupants or their relocation, which are acknowledged as the main barriers to the renovation nowadays. Suitability of PS wall solutions in the seismic retrofit of the existing building stock has been investigated herein, particularly in the case of existing reinforced concrete (RC) buildings, preliminarily focusing on 2D RC frames. The paper shows the weaknesses and strengths of the PS wall solution in relation to the specific features of the considered buildings. An analytical closed-form formulation is proposed and applied as a preliminary tool to evaluate the load distribution in the existing frame and in the PS wall after the retrofit considering the first mode of vibration of the retrofitted system. The results show that, in some conditions, the application of PS walls may be detrimental to the structural response. Along with the evaluation of the effectiveness of the retrofit solution, the proposed formulation allows a preliminary design of the retrofit system. Finally, a series of finite element model analyses have been carried out for validation purposes showing a good agreement between the proposed analytical formulation and the numerical results. [ABSTRACT FROM AUTHOR]

A framework is presented for assessing the sensitivity of typical engineering demand parameters (EDP) to the conditional period selection when using conditional mean spectra (CMS) as targets for ground-motion selection in a performance-based seismic evaluation. The framework consists of computing a suite of CMS targets anchored at conditioning periods within a period range of interest to discretize the demand at a given hazard level, as represented by a uniform hazard spectrum (UHS). Ground motions are selected and scaled for the CMS suite and the associated UHS. The envelope of the median responses from the CMS suite is compared with the median response from the UHS. The framework is instrumental in identifying the conditioning period (T *) range for estimating CMS to capture the maximum median responses at the hazard level of interest. It also helps to characterize the relative difference in responses between using CMS targets and a UHS. The implementation of the methodology is illustrated by evaluating response quantities such as displacement-, acceleration, and force-based EDPs of four reinforced concrete moment frame structures of different heights under three levels of increasing hazard. Results confirm that the conditioning period used for ground-motion selection has a significant impact on the seismic response of displacement-based EDPs, and the sensitivity of the response varies with building height. For other EDPs, like maximum base shear and story acceleration, the results vary. Based on a limited-size ground motion set typically used in practice, the results indicate that UHS-targeted ground motions do not necessarily yield greater demand in comparison with using the CMS for estimating peak story drifts. For maximum floor accelerations, however, the CMS did produce smaller responses. [ABSTRACT FROM AUTHOR]

Infilled frames are usually modelled in the context of global building analysis using simplified procedures without considering the aspects resulting from the interaction between the panel and the frame. Other aspects, such as adequate design of the floor beams and the beam-columns' joints, and control of potential sliding shear failure of the columns, that significantly affect the structural response, are also typically not accounted for. In the present work it is intended to look over the literature to evaluate the state of the art regarding the lessons learn from recent earthquakes, the evolution of the structural codes considering the infill masonry panels, and how this influences the evolution of the numerical models and the experimental works to overcome the existent gaps. [ABSTRACT FROM AUTHOR]

Buckling-restrained braces (BRBs) have proven to be a valuable earthquake resisting system. They demonstrated substantial ability in providing structures with ductility and energy dissipation. However, they are prone to exhibit large residual deformations after earthquake loading because of their low post-yield stiffnesses. In this study, the seismic response of RC frames equipped with BRBs has been investigated. The focus of this research work is on evaluating the effect of the BRB yielding-core length on both the maximum and the residual lateral deformations of the braced RC frames. This is achieved by performing inelastic static pushover and dynamic time-history analyses on three- and nine-story X-braced RC frames having yielding-core length ratios of 25%, 50%, and 75% of the total brace length. The effects of the yielding-core length on both the maximum and the residual lateral deformations of the braced RC frames have been evaluated. Also, the safety of the short-yielding-core BRBs against fracture failures has been checked. An empirical equation has been derived for estimating the critical length of the BRB yielding cores. The results indicated that the high strain hardening capability of reduced length yielding-cores improves the post-yield stiffness and consequently reduces the maximum and residual drifts of the braced RC frames. [ABSTRACT FROM AUTHOR]

Numerous studies on masonry infill panels have greatly contributed to the research of strength, stiffness and energy dissipation capacity of various buildings. If the effects of masonry panels are disregarded, structural damage will occur under any significant ground motion, and even lead to collapse of the entire structure. The mode of failure is strongly dependent on the masonry and RC frame interaction. This work proposes an evaluation method for determining the participation ratio of masonry infill panels on RC frames under lateral loads.

The collapse and damage of large number of buildings during the November 26, 2019 (Mw 6,4) Albania earthquake caused 51 fatalities and injuries to at least 910 people. Most of collapsed or heavily damaged buildings were RC frame buildings. Although RC frame system is considered as very ductile seismic force-resisting system, its behaviour during earthquake highly depends on: (1) regularity in plan and elevation, and (2) global and local ductility. Based on the authors' visit to the earthquake-affected area on behalf of the Serbian Association of Earthquake Engineering and observations of collapsed and damaged buildings, it was concluded that among main reasons for underperformance of these flexible systems were inadequate analysis of interaction between infill walls and RC frames and reinforcement detailing of RC members.

The infill walls may lose their positive effects during the first stages of earthquakes, either by leaving their plane or through breakage. That is why it is common to strengthen these walls before design earthquakes or to repair and strengthen them after suffering slight or moderate damage due to the occurrence of an earthquake. In this study, the effects of adding and strengthening these walls on the structural behavior of reinforced concrete structures were investigated. For this purpose, the infill walls were strengthened with a single mesh of reinforcement and covered with plaster. Five one-story, single bay, and ½ scaled reinforced concrete frames were cast: one was built without infill, the second with a bare infill wall, and the other three with strengthened infill walls with anchorage of different diameters. All these specimens were tested under cyclic loading type reverse. The tests resulted in important relationships and curves, including the lateral load-lateral displacement, envelope curve-lateral load, and lateral displacement, as well as stiffness-lateral displacement and others. Through these results, the effects of adding infill walls and the strengthening procedure of these walls on the structural behavior of the structures were discussed. [ABSTRACT FROM AUTHOR]

Shake table tests were conducted on three 1:3 reduced scale two-story RC frames having weaker beam-column joints. The models were subjected to multi-levels input acceleration time histories to understand the seismic behaviour of test models. The models incurred severe damages in beam-column joint panels, forming shear hinging in joint panels, and were found in the incipient collapse state under input excitation below the design level excitation. Elastic hypothetical structures were considered having fundamental frequency that of test structures, which were subjected to actually recorded input excitation, in order to assess the seismic demands (base shear force and lateral roof displacement) using simplified analytical static procedure. The analytically predicted demands were correlated with the measured inelastic response, in order to calculate seismic response parameters (force reduction factor R and displacement modification factors Cd). On average, R = 2.0 and Cd = 1.86 were obtained for the considered structures. The derived seismic response parameters can be employed in the analytical static force-based procedure for the seismic vulnerability assessment of RC frame structures having weaker beam-column joints. Example study is presented for the vulnerability assessment of considered structure using the proposed analytical static force procedure and the derived seismic response parameters. [ABSTRACT FROM AUTHOR]

Research efforts are still required for modelling the seismic behaviour of infilled frames, especially for existing buildings, generally characterised by shear failures. This work discusses the experimental seismic behaviour and the related modelling of four conforming (compliant with modern seismic codes) and non-conforming (gravity-loads-designed) Reinforced Concrete (RC) frames with and without infills (with hollow-clay bricks). The experimental results are analysed, showing that non-conforming frames exhibited shear failures involving the infill panel and the RC columns/joints. A proposed modelling approach able to reproduce these shear failures is carried out, providing support towards more reliable numerical simulations of RC buildings. [ABSTRACT FROM AUTHOR]

Seismic damage investigations and previous studies show that adding wing walls on both sides of frame columns is an economical and practical enhancement measure to improve the seismic performance of reinforced concrete (RC) frames. Quasi-static tests of three 1/3 scale specimens were carried out to study the seismic performance of two schemes, i.e., wing walls mainly bearing lateral load named as functional separation structure, wing walls both bearing lateral and vertical load named as functional integration structure. The damage development, hysteresis behavior, stiffness degradation, energy dissipation capacity, and other seismic behaviors of the specimens were investigated. The obtained results showed that wing walls improved the structural stiffness, bearing capacity and energy dissipation, but reduced the structural ductility. For the two schemes of will walls, the functional integration structure had a higher load-bearing capacity, while the functional separation structure had a better ductility. There was no obvious difference between the seismic performance of the two schemes overall. Furthermore, seven different retrofitting structures were designed, the seismic collapse resistance of the structural systems is evaluated by the increment dynamic analysis (IDA) method, and design suggestions were given. [ABSTRACT FROM AUTHOR]

Infilled frames are usually modelled in the context of global building analysis using simplified procedures without considering the aspects resulting from the interaction between the panel and the frame. Other aspects, such as adequate design of the floor beams and the beam-columns’ joints, and control of potential sliding shear failure of the columns, that significantly affect the structural response, are also typically not accounted for. In the present work it is intended to look over the literature to evaluate the state of the art regarding the lessons learn from recent earthquakes, the evolution of the structural codes considering the infill masonry panels, and how this influences the evolution of the numerical models and the experimental works to overcome the existent gaps.

This study focused on characteristic cases of recently tested real-scale RC framed wall infilled structures with innovative seismic protection through polyurethane joints (PUFJ) or polyurethane-impregnated fiber grids (FRPU). The frames revealed a highly ductile response while preventing infill collapse. Herein, suitable 3D pseudo-dynamic FE models were developed in order to reproduce the experimental results. The advanced Explicit Dynamics framework may help reveal the unique features of the considered interventions. Externally applied double-sided FRPU jackets on OrthoBlock infills may maintain an adequate bond with the surrounding RC frame as well as with the brick infill substrate at up to a 3.6% drift. In a weak four-column RC structure, the OrthoBlock infills with PUFJ seismic joints may increase the initial stiffness remarkably, increase the base shear by three times (compared with the bare structure) and maintain a high horizontal drift of 3.7%. After this phase, the structure may receive FRPU retrofitting, reveal the redistribution of stress over broad infill regions, including predamaged parts, and still develop a higher initial stiffness and base shear (compared with the bare RC). The realization of a desirable ductile behavior of infilled frames through PUFJ of only 20 mm thickness, as well as through FRPU jacketing, may remarkably broaden the alternatives in seismic protection against the collapse of structures. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Polytechnic Institute of Iasi - Construction & Architecture Section is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The natural landscape in China exposes many existing RC buildings to aggressive environments. Such exposure can lead to deterioration in structural performance with regard to resisting events such as earthquakes. Corrosion of embedded reinforcement is one of the most common mechanisms by which such structural degradation occurs. There has been increasing attention in recent years toward seismic resilience in communities and their constituent construction; however, to date, studies have neglected the effect of natural aging. This study aims to examine the effect of reinforcement corrosion on the seismic resilience of RC frames that are designed according to Chinese seismic design codes. A total of twenty RC frames are used to represent design and construction that is typical of coastal China, with consideration given to various seismic fortification levels and elevation arrangements. Seismic fragility relationships are developed for case frames under varying levels of reinforcement corrosion, i.e., corrosion rates are increased from 5% to 15%. Subsequently, the seismic resilience levels of uncorroded and corroded RC frames are compared using a normalized loss factor. It was found that the loss of resilience of the corroded frames is greater than that of their uncorroded counterparts. At the Rare Earthquake hazard level, the corrosion-induced increase in loss of resilience can be more than 200%, showing the significant effect of reinforcement corrosion on structural resilience under the influence of earthquakes. [ABSTRACT FROM AUTHOR]