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In recent decades, various strategies have been employed to enhance the seismic resilience of structural systems in the event of earthquakes. One such innovative method is the elliptic-braced moment-resisting frame with a rotational friction damper (ELBRF-RFD), which serves as a displacement-restraint bracing technique connecting the elliptic brace to the upper beam. To design an ELBRF-RFD based on contemporary guidelines, for the first time, this study introduces the quantification of seismic performance factors (SPFs) through incremental dynamic analysis (IDA). The research then proceeded to design 3-story, 5-story, and 7-story archetypes in type II soil using the presumed SPFs. A comparative analysis was conducted with inverted-V braced frames equipped with rotational friction dampers (CBF-RFDs). The performance of each archetype was evaluated through nonlinear static pushover analysis (NSPA) and IDA, employing 15 earthquake records from the past and using the OpenSees software. For the response modification factor, suggested values of 11.2 (allowable stress method) and 7.8 (ultimate limit state methods) were identified. Furthermore, the collapse probability of archetypes was determined by employing fragility curves and considering sources of uncertainty. [ABSTRACT FROM AUTHOR]

Purpose: Damage to reinforced concrete (RC) structural elements is inevitable. Such damage can be the result of several factors, including aggressive environmental conditions, overloading, inadequate design, poor work execution, fire, storm, earthquakes etc. Therefore, repairing and strengthening is one way to improve damaged structures, so that they can be reutilized. In this research, the use of an ultra high-performance fibre-reinforced concrete (UHPFRC) layer is proposed as a strengthening material to rehabilitate damaged-RC beams. Different strengthening schemes pertaining to the structural performance of the retrofitted RC beams due to the flexural load were investigated. Design/methodology/approach: A total of 13 normal RC beams were prepared. All the beams were subjected to a four-point flexural test. One beam was selected as the control beam and tested to failure, whereas the remaining beams were tested under a load of up to 50% of the ultimate load capacity of the control beam. The damaged beams were then strengthened using a UHPFRC layer with two different schemes; strip-shape and U-shape schemes, before all the beams were tested to failure. Findings: Based on the test results, the control beam and all strengthened beams failed in the flexural mode. Compared to the control beam, the damaged-RC beams strengthened using the strip-shape scheme provided an increase in the ultimate load capacity ranging from 14.50% to 43.48% (or an increase of 1.1450 to 1.4348 times), whereas for the U-shape scheme beams ranged from 48.70% to 149.37% (or an increase of 1.4870–2.4937 times). The U-shape scheme was more effective in rehabilitating the damaged-RC beams. The UHPFRC mixtures are workable, as well easy to place and cast into the formworks. Furthermore, the damaged-RC beams strengthened using strip-shape scheme and U-shape scheme generated ductility factors of greater than 4 and 3, respectively. According to Eurocode8, these values are suitable for seismically active regions. Therefore, the strengthened damaged-RC beams under this study can quite feasibly be used in such regions. Research limitations/implications: Observations of crack patterns were not accompanied by measurements of crack widths due to the unavailability of a microcrack meter in the laboratory. The cost of the strengthening system application were not evaluated in this study, so the users should consider wisely related to the application of this method on the constructions. Practical implications: Rehabilitation of the damaged-RC beams exhibited an adequate structural performance, where all strengthened RC beams fail in the flexural mode, as well as having increment in the failure load capacity and ductility. So, the used strengthening system in this study can be applied for the building construction in the seismic regions. Social implications: Aside from equipment, application of this strengthening system need also the labours. Originality/value: The use of sand blasting on the surfaces of the damaged-RC beams, as well as the application of UHPFRC layers of different thicknesses and shapes to strengthen the damaged-RC beams, provides a novel innovation in the strengthening of damaged-RC beams, which can be applicable to either bridge or building constructions. [ABSTRACT FROM AUTHOR]

While the use of steel hysteretic dampers has spread in the last decade for both new and retrofitted constructions, the Italian Building Code (IBC), as well as the Eurocode 8, does not provide specific recommendations for the design and verification of structures equipped with this technology. Due to their strong non-linear behavior, the effectiveness of the design with these systems must be verified through non-linear analyses. Non-Linear Time-History analyses (NLTHAs) are the most reliable method, but they are computationally expensive. The aim of the study is to investigate the reliability of non-linear static procedures, allowed by the IBC as an alternative to NLTHAs, for the analysis of buildings equipped with hysteretic devices provided with high damping capability. A parametric study is conducted on two reinforced concrete residential buildings, typical of the Italian residential heritage, retrofitted with hysteretic braces characterized by different stiffness and ductility values. The retrofit design is verified using non-linear analyses, both static and dynamic, considering either natural or artificial accelerograms, as the IBC deems them as equivalent. Within this work, reference is made only to the IBC; however, given the significant similarity between the IBC and the European code, the outcomes are expected to have a broader impact and to be not limited to the Italian context. Therefore, although this work is a preliminary study, it is believed to offer some initial insights on the topic and serve as the foundation for a more in-depth study that could lead to a regulatory revision on the subject. [ABSTRACT FROM AUTHOR]

The importance of seismic probabilistic risk assessment has drawn considerable attention for improving the seismic safety of nuclear facilities against earthquakes that exceed the design input ground motion. The realistic seismic response of the equipment or piping in nuclear power plants for fragility assessment in seismic probabilistic risk assessment must be evaluated. In particular, because piping systems have plant-specific complex configurations, the arrangement and stiffness of piping support structures considerably affect the seismic response characteristics of the entire piping system. However, the current seismic design procedure adopts an evaluation method assuming an elastic response. Therefore, this study develops an elasto-plastic response analysis method to estimate the realistic response of piping systems, including piping support structures. The authors have performed loading tests on piping support structures and optimization studies of elasto-plastic property models to develop an elasto-plastic response analysis method for piping systems, including piping support structures. Herein, the applicability of this method is confirmed through a simulation analysis of the previously reported elasto-plastic response of piping support structure loading test. Consequently, a good correlation is found between the test and simulation analysis results for the ductility factor and the damage status. Therefore, the ductility factor is verified to be effective as a damage evaluation index for piping support structures.

The architectural use areas in the structure are formed by reinforced concrete (RC) slabs, which transport vertical loads to the beams, columns, load-bearing walls, and shear walls. The slab is an important structural member of reinforced concrete building structures and concrete-intensive parts of structural members. . The slab deflects significantly when the load acting on the slab or the clear span between columns is large. As a result, the slab's thickness increases to accommodate the load received. Since this slab's self-weight increases as the thickness increases, the slabs get heavier and causes the slab unable to withstand the load and to produce cracks on the surface. At the turn of the twentieth and twenty-first centuries, the creation of the bubble deck slab became an innovation to replace conventional slab. This study used bamboo as the bubble material in reinforced concrete bubble slab. This study examined and assessed the mechanical properties and structural behaviour of bamboo as a bubble in supported reinforced concrete double-layer bamboo bubble slab under a uniformly distributed load. In this research, 500 mm x 1250 mm x 175 mm supported reinforced concrete slabs C25 (1 sample) and C30 (1 sample) with double layer (DL) bamboo bubble slabs were constructed. Both samples were compared with the control sample (CS) for each slab type. It was found that the maximum displacement occurred at the centre of the slab, with 6.45 mm for DL25 and 6.89 mm for DL30. According to stress-strain analysis, the double layer bamboo slab produced a lower stress value than the control sample. Since the values were smaller than 2, DL25 and DL30 slab performed better for the ductility factor than CS25 and CS30. As a result, the displacement, ductility and section capacity were improved by employing bamboo as a bubble material in a reinforced concrete slab. [ABSTRACT FROM AUTHOR]

Rat-trap bond (RTB) masonry is a fast-growing building technique owing to its thermal insulation and cost saving. While cost and energy efficiency are important parameters, structural stability and performance are as important. The aim of this study is to experimentally investigate the behaviour of unreinforced and confined RTB masonry subjected to lateral load. The experimental work consists of in-plane quasi-static cyclic load tests of two full-scale specimens; an unreinforced wall and a confined masonry wall. Key parameters such as lateral strength, stiffness, damping, force-deformation behaviour and ductility modification factor of both specimens are determined to understand the lateral load behaviour of RTB masonry. The experimental results indicate that the addition of confining elements significantly improved the behaviour of RTB masonry by enhancing the lateral strength, stiffness and ductility ratio of RTB walls by 121%, 52.8% and 23.8%, respectively. [ABSTRACT FROM AUTHOR]

While the use of steel hysteretic dampers has spread in the last decade for both new and retrofitted constructions, the Italian Building Code (IBC), as well as the Eurocode 8, does not provide specific recommendations for the design and verification of structures equipped with this technology. Due to their strong non-linear behavior, the effectiveness of the design with these systems must be verified through non-linear analyses. Non-Linear Time-History analyses (NLTHAs) are the most reliable method, but they are computationally expensive. The aim of the study is to investigate the reliability of non-linear static procedures, allowed by the IBC as an alternative to NLTHAs, for the analysis of buildings equipped with hysteretic devices provided with high damping capability. A parametric study is conducted on two reinforced concrete residential buildings, typical of the Italian residential heritage, retrofitted with hysteretic braces characterized by different stiffness and ductility values. The retrofit design is verified using non-linear analyses, both static and dynamic, considering either natural or artificial accelerograms, as the IBC deems them as equivalent. Within this work, reference is made only to the IBC; however, given the significant similarity between the IBC and the European code, the outcomes are expected to have a broader impact and to be not limited to the Italian context. Therefore, although this work is a preliminary study, it is believed to offer some initial insights on the topic and serve as the foundation for a more in-depth study that could lead to a regulatory revision on the subject.

Self-compacting concrete (SCC) has been versatile over compaction of concrete by manual or mechanical vibrators. Compaction of concrete by traditional methods generates delays and imparts additional costs. Further, much research has been done on the effects of fiber on traditional concrete, but it has rarely been on SCC. Here, fiber-reinforced SCC was prepared by adding glass and steel fibers to study the effect of fibers on fresh properties like workability and hardened properties like compressive, split tensile and flexural strength. Geometrically similar reinforced specimens with 1.0% and 1.5% flexural reinforcement were also prepared to understand the flexural behavior of reinforced SCC with and without fibers. It was observed that the addition of fibers reduced workability and increased mechanical properties like compressive, split tensile, flexural strength, first crack load, ultimate load, and energy absorption capacity. It was also observed that as the size of specimens increased, the ductility factor decreased.

To better understand some physical aspects of nonlinear behaviour reduced to a linear elastic equivalent system an assumed bi-linear or (and) elasto-plastic model is proposed. Thus, this manuscript aims to exploit these approximate methods for analysing nonlinear systems reduced to linearly equivalent system that can be used as design or verification tool and rapid appreciation of the quality of non-linear responses to assess the degree of damage caused by accidental actions such as the dynamic or seismic shock pulses etc. The objective consists in derivation of analytical expressions of elastically equivalent model for a nonlinear system, which will be applied to multi-layer plates. Variation curves of frequency Feq and damping ξeq are obtained from ductility factor μ and slope factor α, as well as for various values of dimensions ratio and modal number. A decrease of frequency curves approaching a half has been observed compared to linear elastic case. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica 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.)

For safer structural design, a simple index that describes the plastic deformation capacity of composite beams is needed, similar to the connection coefficient in the case of strength. In this study, the relationships between the plastic deformation capacity and strength under varying material properties and geometric shapes of concrete and steel members were considered through finite element analyses. Based on the obtained results, the plastic deformation factor was defined as the ratio of two rotation angles. The minimum value of the connection coefficient in composite beams corresponding to the ductility factor under severe earthquakes was determined because the plastic deformation factor can be used similar to the ductility factor. In addition, the minimum value of the connection coefficient in bare steel beams that will be safe even if a concrete slab is added was determined; therefore, the design of bare steel beams and composite beams are connected by the connection coefficient. [ABSTRACT FROM AUTHOR]

Multi-level shaking table tests were performed on a 1:3 reduced scale two-story reinforced concrete (RC) intermediate moment resisting frame (IMRF) conforming to the requirements given in the ACI-318-19. The exterior joints lacked shear reinforcement to assess the viability of the ACI model recommended for determining the design shear strength of the beam–column joint panel. One of the horizontal components of the 1994 Northridge earthquake accelerogram (090 CDMG Station 24278, Source: PEER strong motion database) was input to the frame for multi-level shaking table testing. Plastic hinges developed in beams under base input motion with a maximum acceleration equal to 0.40 g. The exterior joints incurred extensive damage under base input motion with a maximum acceleration equal to 0.70 g. The frame achieved displacement ductility and overstrength factors (determined as the ratio of the maximum resistance of the frame to the design base share force) equal to 2.40 and 2.50, respectively. This gives a response modification factor equal to 6. The satisfactory performance of the frame is attributed to the high efficiency of the beam–column joint, which was confined by spandrel beams on two faces and the high strength of the concrete. The inherent minimal confinement is sufficient to ensure satisfactory seismic behavior. The analysis confirmed overstrength equal to 1.58 for joint shear strength in comparison to the design strength determined using the ACI model. The data might serve as a reference for calibrating and validating numerical modeling techniques for performance evaluation, which are crucial in the context of performance-based engineering. [ABSTRACT FROM AUTHOR]

The building structure with infill wall shows higher global stiffness along with the uncertain behaviour during 2015 Gorkha earthquake. It significantly increased the collapse rate of structures during earthquakes. The response of buildings with different infills during seismic excitations is not completely accounted by current seismic codes in the region. On the other hand, due to the different geological region, availability of infill materials for reinforced concrete building also differs on region to region. In most of the situations the burnt clay brick, concrete blocks and stone block are used as infill materials during building construction. In this scenario, this study explores the importance of selection of right infill material for better seismic performance during earthquakes. For this, building constructed at Pokhara Metropolitan City is considered for case study. The structural model is prepared with and without considering infills. The solid, hollow concrete block and clay brick masonry are taken as infill material during analysis. The structural behaviour during earthquakes is studied with non-linear static pushover. The result shows that the hollow concrete block masonry infill (INHB) shows better structural performance compared to other infill types.

Tall buildings featuring transfer structures are commonly constructed in lower seismicity regions. Discontinuities in load paths of structural systems in the building were found to compromise ductility of the building. In a force-based seismic design procedure, response modification (R) factor is uncertain to cater for the undesirable features. This article presents a methodical approach for evaluating the seismic performance of such buildings. Results of incremental dynamic analyses of case study buildings indicated a high R-factor, due to the inherent over-strength. A local amplification factor ( β D T ) is recommended to account for localised shear at structural walls above the transfer floor level. [ABSTRACT FROM AUTHOR]

In the context of reinforced concrete (RC) structures, standards aim to relate the ductility of these structures to the ductility of the steels used in their construction. Among other requirements, EC8 requires the use of special ductility steels to achieve high ductility in structures. After reviewing the relevant literature, this study aims to evaluate the impact of various parameters on the ductility at the cross-section level of RC elements subjected to bending. The study concludes that there is no consensus on the assessment of ductility, nor a standardized framework for the various alternatives. Additionally: i) Some contradictions exist regarding the impact of fundamental parameters on the assessment of ductility; ii) A one-size-fits-all methodology is impractical given the diverse factors influencing ductility in RC elements. It is proposed to consider the ductility of RC element sections as a function of the mechanical ratio of tensioned reinforcement. A proposal is also made to enhance the ductility of cross-sections without significantly increasing their strength: by increasing the width of the section while keeping other parameters unchanged. ● Ductility of RC beam section reviewed. ● A framework to analyse and evaluate the ductility. ● Impact of mechanical ratio of reinforcement on ductility. ● Impact of section parameters on ductility. ● A way to improve ductility. [ABSTRACT FROM AUTHOR]

One of the efficient methods for seismic design of structures is Performance-based Plastic Design (PBPD) in which by choosing the desired yield mechanism and the target drift at the beginning of the design, unlike that in conventional design methods, there is no need for a time-consuming process of trial and error to achieve the desired performance. On the other hand, recent earthquakes have shown that aftershocks can increase the damage to a building after the main earthquake and thereby threaten the safety of the inhabitants. However, the seismic hazard of aftershocks is still not explicitly included in the current design codes. In this study, attempts have been made to develop the PBPD method for considering the effects of aftershocks. For this purpose, by performing an incremental dynamic analysis (IDA), the ductility factor μ and the ductility reduction factor Rμ of six PBPD frames (2-, 4-, 6-, 8-, 10-, and 12-story) were calculated under mainshock and mainshock-aftershock sequences. Then, the energy modification factor γ, which is related to the two parameters μ and Rμ, was calculated for both the mainshock and the mainshock-aftershock sequences. An equation is presented in order to calculate the ratio of the energy modification factor of the mainshock-aftershock sequence to the mainshock energy modification factor ( γ m s + a s γ m s ) according to the design period, and the factor obtained is multiplied by the energy modification factor γ so that the effect of aftershock can be considered for the frame design, and by using this modification, the performance of the frame under the mainshock-aftershock sequence can be improved. The results of the time-history analysis performed on the modified PBPD frames show better performance by the frames designed on the basis of modified PBPD than the frames designed on the basis of the original PBPD method under MS-AS sequences in terms of inter-story drift and rotation of plastic hinges. [ABSTRACT FROM AUTHOR]

Additional hysteretic experiments for corroded rectangular reinforced concrete (RC) columns with an axial load ratio of 0.27 were implemented. A quasi-static cyclic lateral loading with constant axial force was subjected to tests. Herein, a modified ductility factor model for corroded RC column is developed on the basis of the previous work and additional experiments. The model involves the influence of both the corrosion ratio of longitudinal rebar and the axial load ratio. A four-linear envelope curve model concerning lateral load and displacement is proposed in a combination of determination rules of the peak point and the failure strength point. The hysteretic model of corroded RC columns is developed by considering both degraded unloading stiffness and reloading stiffness on the history peak point. The hysteretic model can predict the residual life of corroded RC columns under seismic loading. [ABSTRACT FROM AUTHOR]

Multi-level shaking table tests were performed on a 1:3 reduced scale two-story reinforced concrete (RC) intermediate moment resisting frame (IMRF) conforming to the requirements given in the ACI-318-19. The exterior joints lacked shear reinforcement to assess the viability of the ACI model recommended for determining the design shear strength of the beam–column joint panel. One of the horizontal components of the 1994 Northridge earthquake accelerogram (090 CDMG Station 24278, Source: PEER strong motion database) was input to the frame for multi-level shaking table testing. Plastic hinges developed in beams under base input motion with a maximum acceleration equal to 0.40 g. The exterior joints incurred extensive damage under base input motion with a maximum acceleration equal to 0.70 g. The frame achieved displacement ductility and overstrength factors (determined as the ratio of the maximum resistance of the frame to the design base share force) equal to 2.40 and 2.50, respectively. This gives a response modification factor equal to 6. The satisfactory performance of the frame is attributed to the high efficiency of the beam–column joint, which was confined by spandrel beams on two faces and the high strength of the concrete. The inherent minimal confinement is sufficient to ensure satisfactory seismic behavior. The analysis confirmed overstrength equal to 1.58 for joint shear strength in comparison to the design strength determined using the ACI model. The data might serve as a reference for calibrating and validating numerical modeling techniques for performance evaluation, which are crucial in the context of performance-based engineering.

The existing seismic provisions across the world account the non-linear response of a structure in a linear elastic design implicitly using a constant behavior factor, or response reduction factor (R). However, this factor (R) does not address the effects of changes in structural configurations, which eventually alters the dynamic behavior of the structure. Hence, the adequacy of prescribing a constant factor to account for the variable dynamic characteristics of structural systems always appears contentious. Further, seismic analysis of RC buildings usually ignores the interaction of the infill wall with the structural frame leading to inappropriate evaluation of dynamic characteristics of the structure. Hence, in the present research, it is attempted to investigate the sufficiency of the code-based 'R' factor in assessment of seismic behavior using non-linear static analysis (NLS) and non-linear dynamic analysis (NLD) for the structural models considered. Moreover, the results obtained, clearly envisages the influence of structural configuration changes and interaction of the infill wall with the RC MRF on dynamic characteristics in terms of ductility and over strength values. It can be clearly observed that, the code specified constant 'R' for a particular structural type appears erroneous, emphasizing the need for its adequate estimation. This should involve consideration of the dynamic characteristics of the structure resulting in a realistic assessment of seismic demand, thereby contributing to a safe, functional and economical design configuration. [ABSTRACT FROM AUTHOR]

The seismic performance of elliptic braced moment resisting frame (ELBRF) is assessed here and is found that the structural behavior is improved and is of free of architectural space. The demand for seismic performance of ELBRF is estimated through conventional pushover methods of 3, 5, 7, and 10-story ELBRF frames and they are compared with special moment resisting frames (SMRF) and X-Braced CBF and Inverted V-Braced CBF concentrically braced frames. The effective parameters in the seismic design of structures, like the ductility, overstrength and response modification factors are evaluated. The response modification factor for ELBRF in the design by ultimate limit state and allowable stress methods is proposed as 10 and 14.4, respectively. Finally, the process of forming plastic hinges in ELBRF is assessed and it is found that an increase in height makes the plastic hinges to be transmitted to the upper stories, allowing the structure to collapse at higher stories.

In existing seismic design codes, base shear is measured using the elastic force requirement divided by the strength reduction factor. This factor is used to take account of structures’ ability to dissipate energy by inelastic deformations. The main objective of this study is to determine the response modification factor (R) for RC frames with non-uniform spans and heights and compare the values to the Egyptian Code of Practice ECP-201. The case study consists of three groups of RC frames with detailed structural design: uniform spans and heights, non-uniform spans, and non-uniform heights. A sum of 30 systems of frames is analyzed by nonlinear static analysis, “pushover analysis,” using SAP2000 with FEMA-356 provisions to assess the R factor. Also, a comparison is held with R factor in the Egyptian code. It was found, considering the limitations mentioned in the conclusions, that R factor decreases with increasing the height of selected floors and it is greatly affected by the non-uniformity of span lengths. The listed values of R factor in the Egyptian code are conservative and not economic. Thus, it is recommended to include the non-uniformity in spans and heights, to get more accurate values of R factor.

Code requirements are usually fulfilled during the design of a building. On the other hand, reinforced concrete (RC) frames (particularly in the developing regions of the world) are deficient (in many cases) due to unregulated construction. Majority of such deficient structures lack shear reinforcement in beam-column joints. Collapse of these deficient buildings (as a result of limited ductility) triggered many socio-economic and human losses which is evident from recent earthquake disasters. This paper presents an experimental study which was conducted on a 1:4 reduced scale three-storey RC special moment resisting frame (SMRF) lacking shear reinforcement in the beam-column joints. The lack of confinement bars causes shear hinging of joints that reduces the displacement ductility of the frame. Shake-table tests were conducted on test model that was subjected to acceleration time history of 1994 Northridge earthquake, having a peak ground acceleration of 0.57 g. The acceleration was linearly scaled to multiple levels and to sinusoidal base excitations of various frequencies and displacements. Moderate to severe damage at each storey level was observed in the joint panels due to the lack of lateral reinforcing ties in the joints. The data obtained from shake table tests were processed and analysed to develop a lateral force-deformation capacity curve, which was bi-linearized as an elasto-plastic curve to compute various response parameters of frame. The ductility factor (Rm) of the tested model was found to be equal to 1.95, which is thirty-five percent less than the code recommended value of Rm for RC SMRF structures. [ABSTRACT FROM AUTHOR]

In existing seismic design codes, base shear is measured using the elastic force requirement divided by the strength reduction factor. This factor is used to take account of structures' ability to dissipate energy by inelastic deformations. The main objective of this study is to determine the response modification factor (R) for RC frames with non-uniform spans and heights and compare the values to the Egyptian Code of Practice ECP-201. The case study consists of three groups of RC frames with detailed structural design: uniform spans and heights, non-uniform spans, and non-uniform heights. A sum of 30 systems of frames is analyzed by nonlinear static analysis, "pushover analysis," using SAP2000 with FEMA-356 provisions to assess the R factor. Also, a comparison is held with R factor in the Egyptian code. It was found, considering the limitations mentioned in the conclusions, that R factor decreases with increasing the height of selected floors and it is greatly affected by the non-uniformity of span lengths. The listed values of R factor in the Egyptian code are conservative and not economic. Thus, it is recommended to include the non-uniformity in spans and heights, to get more accurate values of R factor. [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.)

Incremental dynamic analysis and nonlinear static pushover analysis are carried out on a performance-based design to determine the seismic demands and capacities of an elliptic braced moment resisting frame (ELBRF). The objective is to assess ductility, overstrength and response modification factors in a modern steel-braced structural system based on incremental dynamic analysis. This integrated system is connected to a beam and column with an appropriate length while providing enough architectural space to allow for an opening without having the common problems associated with architectural spaces in braced systems. Several different classes of buildings are considered on soil type II. Linear dynamic analysis, nonlinear static pushover analysis and incremental nonlinear dynamic analysis related to 12 records from past earthquakes are carried out using OpenSees software. The factors of ductility, overstrength and response modification are calculated for this system. The values of 9.5 and 6.5 are found and suggested only for the response modification factor for ELBRF systems in allowable stress and ultimate limit state methods, respectively. The fragility curves are plotted for the first time for this type of bracing, which contributes to the assessment of building seismic damage. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the longitudinal seismic displacement of the Quasi Seismic Isolation Bridge (QSIB) based on the Energy-based Multimodal Pushover Method (EMPM), including the pier-beam relative displacement and the collision effect. As a simplified seismic analysis method, the EMPM invokes the concept of energy balance into the modal pushover analysis to assess the nonlinear seismic behavior of Laminated Rubber Bearing (LRB) on bridges. In this method, the energy-based capability curve is obtained by the modal pushover analysis, while the energy-based demand curve is estimated under the ground motion record. The target performance criterion can be derived by intersecting the capability curve with the demand curve. The effect of several key factors in EMPM, such as the mode classification and selection, collision effect, energy coefficient and ductility factor, are studied by a case study of a prototype QSIB under ChiChi and El Centro earthquakes. The results of EMPM are compared with those from Nonlinear Time History Analysis (NTHA), to illustrate the effectiveness and accuracy of this method for evaluating the maximum seismic displacement, and the pier-beam relative displacement with and without collision. Results show that the EMPM is found to be able to estimate the longitudinal seismic displacement of the QSIB with and without collision, and can be used as an effective alternative for rapid assess the seismic performance of bridges. The results also indicate that LRB stiffness for modal analysis should be taken as the stiffness pre- or post-sliding when without or with the gap element. Collision effect enlarges the peak displacement and the maximum bias of EMPM. • A novel method is found to be able to evaluate the seismic displacement with and without collision. • The mode classification and selection for the novel method are proposed and verified by case study. • The collision effects can be incorporated in the novel method. • The inverse vibration mode is pointed out to be the key mode to assess the pier-beam relative displacement and the collision. [ABSTRACT FROM AUTHOR]

The manuscript deals with a study on the performance/reliability analysis of steel hysteretic dampers designed for the seismic retrofit of RC frame structures at the Basic Design Earthquake, BDE (characterized by a 10 % probability of being exceeded over the reference lifespan, V R) for higher hazard levels, represented by a Maximum Considered Earthquake, MCE, with either 5 %/V R or 2.5 %/V R exceedance probabilities. Indeed, seismic codes prescribe that anti-seismic devices designed to satisfy the performance requirements at the BDE must be able to resist earthquakes of higher intensity. Therefore, γ-factors amplifying the design displacement or force must be considered for the design of the device capacity. The objective of the study consists in evaluating the over-demand caused on the steel dampers incorporated in dissipative bracing systems when passing from the BDE to the two higher hazard levels, and comparing this over-demand to the values of the corresponding γ-factors proposed in current codes. Dampers with various ductility factors are considered to include the majority of current hysteretic devices. The amplification factors recommended in the codes for hysteretic dampers are shown to be not suitable for guaranteeing the damper reliability; moreover, a dependence of the reliability of the retrofitted structures upon the ductility of the damped braces is highlighted. • Reliability of RC buildings with hysteretic dampers designed for ultimate limit state is studied. • No failure of RC structure and dampers is checked at non-collapse limit states. • Likelihood of building failure decreases as the damper ductility increases. • Displacement capacity of dampers prescribed by current codes is not conservative. • Displacement demand of dampers seems to depend linearly on the PGA of the site. [ABSTRACT FROM AUTHOR]

Steel–concrete–steel (SCS) sandwich composite system consists of steel plates covering both sides of the concrete core and connected by mechanical means such as shear connectors. In conventional steel–concrete–steel system, shear connectors are welded to the steel cover plates. Laced steel–concrete composite (LSCC) system is a new form of steel–concrete–steel, proposed earlier by the authors. In LSCC system, steel cover plates are connected in a novel way using lacings and cross rods and hence is devoid of welding. Proposed sandwich composite system is being evaluated systematically for its structural behaviour under various modes of loading for use in special structures under severe loading such as blast loading. Damage under cyclic loading and energy absorption are extremely important, which are highlighted in this paper. An experimental investigation on the cyclic response behaviour of two LSCC beams is carried out. Angle of lacing is the parameter that is varied between the two beams. Both the beams are found to exhibit similar behaviour on most of the aspects. The envelope of hysteretic response indicates mild softening behaviour after reaching peak value. Maximum load resisted under both sagging and hogging moment conditions is found to be nearly equal, thus making the LSCC system suitable for situations where reversal of loads are encountered. Dissipated energy is observed to be nearly the same for the load applied in the upward as well as in the downward direction. Analytical prediction on energy absorption capacity is carried out by adopting a hysteretic model with strength deterioration. Cyclic ductility factor is evaluated to be about 20 for LSCC beams, while support rotation is calculated to be about 8° and 10° for beams with 45° and 60° angles of lacing, respectively. Spalling of concrete is prevented in LSCC beams by the steel cover plates. [ABSTRACT FROM AUTHOR]

All-steel buckling restrained brace (BRB) is a type of relatively new common bracings considering its low weight and whilst it is not required curing of mortar at the core of braces. In this study, a new form of all-steel BRB is introduced with corrugated edges of the core and the external sheath, and it was analyzed by using of finite element method. Existence of corrugated and ribbed edges led to enhance of buckling resistance. Numerical model was validated with laboratory samples, and after receiving an acceptable compliance in model behavior, the numerical models were offered. In this analysis, key parameters were size of brace section and distance of gap between the internal and external sheaths. The most appropriate size for gap between the core and external tube was determined to be 10 mm. Upon specifying the non-linear modeling parameter, two cases of frame with ordinary concentrically brace and the proposed all-steel BRB were compared for three structures with 4, 8 and 12 floors using pushover and non-linear time history analysis. The results demonstrated that utilizing of the proposed BRB will lead to an increase in behavior coefficient and structure ductility as well as an alteration in performance level of tall structures from collapse prevention to life safety level. [ABSTRACT FROM AUTHOR]

This study proposes a procedure for determining design input energy spectra for self-centering single-degree-of-freedom (SDOF) systems using a characteristic flag-shaped hysteretic model. The procedure for determining design input energy spectra considers the influence of ground motion factors, hysteretic models, damping ratios, and ductility factors. First, nonlinear dynamic time history analyses are performed using 40 representative ground motion records to establish the relationship between input energy spectra and critical parameters. Based on this, normalized design input energy spectra and relevant parameters are proposed. The results of this study indicate that the bilinear hysteretic model is not suitable to accurately predict the input energy spectra for self-centering systems. Meanwhile, both the damping ratio and ductility factor have a significant influence on the resulting input energy spectra throughout the entire period range. The proposed procedure can be used to predict earthquake input energy spectra for self-centering SDOF systems. • The parameters influencing the earthquake input energy spectra for self-centering SDOF systems are investigated. • The classification for ground motion is based on earthquake records properties, including PGV/PGA and effective duration t D. • The normalized design input energy spectra for self-centering SDOF systems have been proposed. [ABSTRACT FROM AUTHOR]

In this paper, a new type of structure was introduced. The spatial steel grid structure was composed of the top layer, lower layer H-shaped steel ribs and square steel tubes. The shear key is the key part of the structure. Based on the real dimensions of a practical prototype, two sets of full-scale shear key specimens were made, one of which has vertical stiffening ribs. The loading tests of two groups of specimens were carried out to simulate cases under pure shears and the experimental results were compared with the simulations from the finite element analysis. The effects of vertical stiffeners on failure modes, ultimate loads, strengthyield ratio and ductility of shear key were studied through experiments. By parametric analyses in the present article, relations of the stiffening plates width and thickness was recommended. [ABSTRACT FROM AUTHOR]

Highlights • Correct steel slit panels modeling in finite element software (Abaqus). • Overstrength factor of dual moment-resistant frame with steel slit panel is 4.16. • Reduction factor due to the ductility for this system is 1.91. • Response modification factor (behaviour factor) for this system is 8.11. • Overstrength factors decrease up to 6 story and keep unchanged for higher structures. • Ductility factors decrease up to 10 story and keep unchanged for higher structures. • Behaviour factors decrease up to 10 story and keep unchanged for higher structures. Abstract In this paper, the overstrength, ductility and response modification factors of moment resistant frame (MRF) with steel vertical slit panel (SSP-MRF) were investigated and determined. For this purpose, buildings with various stories were used. Abaqus software was used to perform the static pushover analysis, linear dynamic analysis, and nonlinear incremental dynamic analysis. In this research, seismic response modification factor has been evaluated for each model structure using pushover analysis, and the tentative value 8.11 has been proposed for the ultimate limit state design method. Some of the results of pushover analysis and nonlinear incremental dynamic analyses were compared. According to this comparison, the response modification factor of 10-story model structure derived from pushover analysis (6.14) was slightly smaller than those obtained from incremental dynamic analyses (7.5). [ABSTRACT FROM AUTHOR]

When considering models for seismic assessment and retrofit design, designers need to account for any changes in the structural ductility factor and performance factor between an original unreinforced masonry structure and one which has been subsequently retrofitted. There are enough data available in the literature and the standards to suggest ductility and performance factors for existing unreinforced masonry walls or buildings. However, there is a lack of information regarding the above-mentioned factors for retrofitted structures or walls. Retrofitting unreinforced masonry buildings can improve the behaviour factors, displacement capacity, stiffness and performance of the structure. Retrofit strategies are aimed at improving the performance of the structure locally by considering the weak or brittle elements, and/or to improve the global behaviour of the building by focusing on the connections of the elements. In the present paper, the different retrofitting techniques for unreinforced masonry walls and unreinforced masonry buildings are considered. The structural factors for retrofitted walls and structures are calculated using experimental data extracted from the literature and are compared, together with a discussion, to the pre-retrofitting factors available in the literature and different standards. The implications for the relevant standards regarding the performance of retrofitted masonry structures are also discussed. [ABSTRACT FROM AUTHOR]