Seismic Behavior Of Structures Research Articles

Analysis Seismic Behavior of Structures with Planar Imperfections: A Comprehensive Numerical Analysis

This paper presents a comprehensive approach to the seismic analysis and design of a tall hospital building, accounting for horizontal irregularities and employing equivalent static analysis (ESA) methodology. The study initiates with the collection of relevant site data and building specifications, including the identification and characterization of horizontal irregularities such as setbacks, mass distribution variations, and irregular floor plans. Equivalent static lateral loads are calculated based on applicable building codes and standards, taking into account the effects of horizontal irregularities on seismic response. Structural modeling and analysis are then conducted using sophisticated software to evaluate the building's behavior under seismic forces, considering the influence of irregularities on structural performance. Design criteria, encompassing drift limits, strength requirements, and detailing considerations for mitigating irregularity effects, are rigorously adhered to ensure compliance with safety regulations and performance objectives. The iterative process of evaluation and adjustment ensures optimal seismic performance and adherence to design criteria despite the presence of horizontal irregularities. Documentation of the analysis and design process, coupled with meticulous construction oversight, guarantees the implementation of a robust seismic design strategy tailored to the unique characteristics of the tall hospital building. Post-construction evaluations are carried out to validate predicted seismic performance, accounting for the influence of horizontal irregularities. Through collaborative efforts and adherence to best practices, the seismic design of the tall hospital building prioritizes safety and resilience, even in the face of horizontal irregularities, aiming to safeguard occupants and critical healthcare infrastructure during seismic events.

Comparative Study of One-Dimensional Site Response Analysis on Deep Soft Clay Deposit using DEEPSOIL and NERA

Numerous high-rise buildings have been built in major cities in Indonesia. In high seismicity areas, such as Surabaya, the seismic behavior of structures is notably affected by the seismic characteristics of the subsurface soils. Typically, site-specific response analysis (SSRA) is conducted to determine the peak ground acceleration experienced at the ground surface. This paper compares one-dimensional site response analysis on deep soft clay deposits in Surabaya city using two commonly used 1D site response programs: DEEPSOIL and NERA (Non-linear Earthquake Site Response Analyse). A soil column model with 24 m thick very soft clay was developed. To represent different ground motion intensity, three levels of input motion were applied at the bedrock with peak ground accelerations (PGA) of 0.07g, 0.3g, and 0.51g. These input motions were then applied in a one-dimensional non-linear site response analysis to evaluate the seismic soil response at the surface. The evaluation involves examining the peak ground acceleration (PGA) and maximum shear strain profiles obtained from both software programs. The results indicate that the non-linear analysis conducted with NERA yielded greater amplification factors across all periods compared to the results obtained from DEEPSOIL. For the low-intensity motion, both software showed amplification of the input motion for all periods. In contrast, the spectral response obtained with DEEPSOIL demonstrated de-amplification trends for periods less than 1 s for the case of medium and high-intensity motions, whereas no de-amplification was observed from the results of NERA. This difference results in the amplification for medium and high-intensity motions can be attributed to the strength correction factors that are implemented in the DEEPSOIL software to take into account the representative shear strength of the soil layers.

Investigating the effect of steel micro‐ and macro‐fibers on the bond behavior of steel rebar embedded in ultra‐high performance concrete

AbstractIn recent years, the use of ultra‐high performance concrete (UHPC) has been widely considered in special structures and retrofitting of existing structures. Since most of the relations proposed by the regulations are based on the behavior of concrete with normal strength concrete, it is necessary to conduct more experimental studies to predict the behavior of UHPC. One of these notable behaviors is the bond and cohesion between rebar and UHPC, which plays a critical role in the design and seismic behavior of structures. In the present study, a series of experimental tests of uniaxial compressive strength, splitting (Brazilian) tensile strength, elastic modulus, and pull‐out of ribbed steel bars from ultra‐high performance fiber‐reinforced concrete (UHPFRC) were performed. The tests were done considering the four‐volume fractions of hooked‐end steel macro‐fibers, straight steel micro‐fibers, a hybrid combination of these two fibers, three different diameters of ribbed steel bars, and several embedded lengths. Moreover, direct tensile and compressive stress–strain curves, Young's modulus, bonding properties of rebar with UHPFRC, and fracture mechanisms were considered. The results indicated that applying micro‐fibers may enhance the bond stress between rebar and UHPC better than macro‐fibers. Also applying hybrid fibers resulted in the concurrent enhancement of bond stress and the optimum point slip of UHPC in the stress–slip diagram. This finding maybe attributed to the satisfactory performance of micro‐fibers in reducing the growth speed of micro‐level cracks and the suitable effect of macro‐fibers in decreasing the progression speed of macro‐level cracks. Furthermore, it was revealed that the increase in rebar diameter and embedding length leads to the reduction of maximum bond stress in UHPFRC.

Comparative Analysis and Evaluation of Seismic Response in Structures: Perspectives from Non-Linear Dynamic Analysis to Pushover Analysis

This study presents a detailed comparative analysis of different methods for evaluating seismic response in structures, focusing on maximum displacements and collapse assessment. The results obtained through modal spectral analysis, non-linear dynamic analysis, and the incremental pushover analysis applied to a specific structure are compared. It has been found that the choice of time step and the consideration of ductility are critical for obtaining accurate predictions. The results of the non-linear dynamic analysis of the building’s response indicate that an earthquake equivalent to the one that affected the city of Lorca (southeast Iberian Peninsula) in 2011 would have a devastating impact on the studied structure, highlighting the importance of the finite element method modelling in predicting the formation of plastic hinges and assessing structural safety. These findings highlight the importance of utilising multiple analysis approaches and detailed modelling to fully understand the seismic behaviour of structures and ensure adequate resistance and stability to extreme events.

Time-History Analyses on the Effect of Partial Infill Walls on the Seismic Response of a Reinforced Concrete Frame Structure

Time-history analysis (THA) is based on direct step-by-step integration of the equation of motion in time domain considering as input either the recorded accelerograms of real or artificially generated earthquakes. Numerical simulations are sensitive in terms of material properties, geometry, boundary conditions and applied loading scenarios correct definition. Therefore, additional care is required in the pre-processing stage of the analysis when the numerical model is defined. Infill walls play an important role on the seismic behaviour of structures during earthquakes. The response of the structure to seismic action changes due to the presence of the infill walls. The paper presents the results obtained by means of THA on the effect of partial infill walls on the seismic response of a scaled-down RC frame structure subjected to four consecutive uniaxial seismic motions. The parameters of the research were the presence of the partial infill wall and the thickness of the wall. The obtained results are discussed from the point of view of maximum lateral displacements and response spectra expressed in terms of accelerations. The results contribute towards the setting up of the subsequent shake table tests of scaled-down RC frame models with different configurations that would validate and help calibrate the numerical model.

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Assessment of seismic behavior of historical masonry cupolas: Case of Emir Saltuk Cupola

The protection of historical masonry structures against earthquakes requires a comprehensive understanding of their nonlinear behavior; including damage and collapse mechanisms. Throughout history and in present times, these structures have undergone multiple strengthening interventions to enhance their seismic resilience. In this context, the utilization of nonlinear analysis on 3D finite element models has become a common and reliable approach. This article focuses on the seismic performance of historical Emir Saltuk Cupola of Erzurum city which is recognized as a cultural asset by the Ministry of Tourism and Culture of the Republic of Türkiye. Emir Saltuk Cupola is a rare work built in the 12th century as a monumental grave for the founder of Saltuklu Government. The study specifically examines the impact of a reinforced concrete pulley and dome, previously added to the cupola for the purposes of seismic strengthening, on its seismic behavior, force-displacement capacity, and collapse mechanism. Determining the seismic behavior of the structure is aimed to create an important reference for cupola structures, which are frequently encountered in the Turkish-Islamic geography. Notably, this study marks the first instance where advanced numerical simulation methods have been employed to analyses the cupola. Additionally, no prior research has been conducted to assess the propagation of damage and collapse mechanisms within this type of structure. Finite element model of the structure was developed considering the architectural characteristics of the cupola. The model was calibrated based on the findings of operational modal analysis. Nonlinear dynamic analyses were performed using ground motion records from significant earthquakes, including the 1992 Erzincan, 1995 Kobe and 2023 Kahramanmaraş earthquakes, to study the seismic behavior and collapse mechanisms of the cupola. The study evaluated the reinforced concrete pulley and dome in terms of maximum principal strains, maximum displacements, crack distributions, and failure mechanisms of the cupola. The reinforced concrete elements added to the structure in previous years, while assisting in a significant increase in strength capacity, did not contribute significantly to displacement capacity of the masonry. Additionally, it has been determined that under strong ground motions, these elements completely alter the collapse mechanism of the structure, leading to damage in the reinforced concrete elements and thus helping to prevent complete collapse. The findings highlight the substantial impact that strengthening interventions may be altering the seismic behavior of historical structures. Overall, this research contributes to our understanding of the seismic performance of historical masonry cupolas and emphasizes the importance of accurately assessing their behavior through advanced numerical simulations which are supported by in-situ experimentation.

Seismic Behavior of Structures with Different Cantilever Projections in Different Zones

Abstract: This research paper focuses on studying how structures with different cantilever projections (1m, 1.25m, and 1.5m) behave during seismic events in different seismic zones. The analysis is conducted for both 5-story and 10-story buildings, following the guidelines provided in IS 1893 (Part 1):2016. The static method is used to assess various parameters, including story drift, frequency and time period in ETABS software. By examining these factors, we can better understand how these structures perform under seismic forces.

The Seismic Behavior of Buildings with Flat Slab Systems under Near-Fault Ground Motions

It is well known that structural displacement or ductility demands of structures subjected to near-fault ground motions are generally greater than ordinary ground motions. Therefore, the effect of earthquake records in the near region on the seismic behavior of structures has been widely studied in the last decades. Peak ground acceleration (PGA) is an important key parameter, which determines structural behavior. However, structural behavior depends on the distance of the structure to the fault zone, the ratio of peak ground velocity (PGV) to peak ground acceleration, the velocity pulse duration of ground motion, and the natural period of the structure. In this study, the seismic behavior of buildings with flat slab systems was investigated under near-fault ground motions. Linear time history analysis was performed for a 30-storey building designed according to TBEC-2018 using SAP 2000 finite element analysis software. Results were compared with the behavior of the building with a solid slab system. It is concluded that the ratio of PGV/PGA is very effective on the flat slab systems.

Seismic Behavior of Structure with Cantilever Projections in Different Zones

Abstract: In this research paper, the main focus is on understanding how structures with constant cantilever projections of 1m perform when subjected to seismic forces. To carry out the analysis, the researchers utilize ETABS software, which is commonly used in the field of structural engineering. The study investigates two types of buildings: a 5-storey building and a 10-storey building. By using the static method, the researchers evaluate various aspects of the structure’s seismic behavior. This includes examining the story displacement, which refers to how much each floor moves during an earthquake. They also examine the overturning moment, which helps to assess the potential for the structure to rotate or tip over due to seismic forces. Additionally, the researchers analyze the base shear, which represents the total force experienced by the building's foundation due to seismic activity. By conducting these analyses, the researchers aim to gain insights into how the structures with 1m cantilever projections perform in different zones under seismic conditions. This information can be valuable for designing safer and more resilient buildings in earthquake-prone areas.

Assessing the seismic behavior of structures controlled with a novel elastoplastic-tuned mass damper inerter considering the effects of soil-structure interactions

In this paper, an elastoplastic-tuned mass damper inerter (PTMDI) is introduced, and its practical advantages under soil-structure interaction are investigated.For this purpose, a nine-story building frame equipped with PTMDI is modeled nonlinearly in the OpenSees software using the concentrated plasticity model. The Bald Eagle Search Optimization Algorithm calculates the PTMDI parameters for a structure with a fixed base or located on three soil types (i.e., soft, medium, and stiff soils).The objective function is the minimization of the Park-Ang damage index of the controlled structure. The results show that PTMDI has dramatically reduced the Park-Ang damage index in the controlled structure using the inertia-strengthening effect and the nonlinear behavior of the PTMDI system. The results show that the PTMDI has reduced the structural damage index of the controlled structures by more than 50% compared to the uncontrolled ones since the controlled system reduces the deformation of the members and drift story. Also, more energy is dissipated because the spring of the control system goes into the nonlinearity. It has also depicted that the PTMDI increases the performance level of the structure from the collapse state to the life safety state. Due to the inertia-enhancing effect of the PTMDI, the mass ratio of the proposed control system does not significantly affect the behavior of the structure. Therefore, the dynamic responses of the structure can be controlled with a small mass.

In‐plane quasi‐static tests for the evaluation of seismic demand on Power Actuated Fasteners (PAF)

AbstractRecent research showed that the damage in non‐structural components significantly affects the seismic behaviour of structures, indeed it is crucial to evaluate the seismic behaviour of non‐structural components. For this purpose, the University of Naples “Federico II” started a cooperation with the Hilti Corporation, to evaluate the seismic demand on fasteners connecting drywalls to supporting elements. In particular, the seismic displacement demand on Power Actuated Fasteners (PAF) was obtained through quasi‐static in‐plane cyclic tests on full‐scale drywall partitions.Test specimens consisted of 2285 mm long and 2600 mm high partition walls and in total seven tests were carried‐out at the Lab of the Department of Structures for Engineering and Architecture. A specific test set‐up was developed for the experimental tests and the optimal instrumentation layout was studied to allow to capture the significant measurements on PAFs. A FEMA 461 protocol was employed for all the tests.The paper summarizes the experimental program, describing wall configurations, test set‐up, loading protocol and instrumentation layout. A special focus is dedicated to the comments of experimental results.

On the Role of Seismic Damage Tolerance on Costs and Life Cycle of CLT Buildings

This paper presents a contribution to reviewing the most common seismic design procedures of CLT buildings and their implications on structural features and technological solutions. Attention is particularly focused on the overall seismic performance, damage tolerance, construction costs and environmental impact. It is intended as a baseline for a more comprehensive study, thus the assessment is made with reference to a real building, representative of a class of common buildings recently designed and erected in many Italian regions exposed to low and moderate seismic hazards. As usual, the analysis was carried out according to a two-dimensional model of the panels, assumed to be elastic, varying the type of connections at the base, the presence of pre-stressing steel bars for rocking control and dissipative devices. The main outcomes of the study can be summarized as follows: (i) the structural seismic behavior of CLT buildings is significantly influenced by the structural schemes adopted for walls and connections; (ii) construction costs and environmental impact decrease whenever damage tolerance is accounted for in design procedures.

Effects of constitutive soil models on the seismic response of an offshore jacket platform in clay by considering pile-soil-structure interaction

Offshore jacket platforms are widely used for wind energy generation and gas and oil field development. The South Pars gas field, located in the Persian Gulf, stands as one of the largest gas fields in the world. This gas field is situated in a seismically active region predominantly characterized by clay soil. Considering the significant impact of clay soil on the seismic response of offshore structures and their vulnerability to damage, it is essential to conduct comprehensive studies on the seismic behavior of offshore structures in this particular area while considering the nonlinear behavior of soil and pile-soil-structure interaction (PSSI). However, due to the laboratory limitations, it is difficult to experimentally investigate the seismic behavior of these structures on a real scale by considering the actual soil environment. This paper aims to adopt a nonlinear kinematic hardening model for clay in Abaqus software and calibrate this model parameters for the South Pars gas field region to carefully investigate the effects of nonlinear behavior of soil and PSSI on the seismic response of an offshore jacket platform. In addition, the perfectly elasto-plastic Mohr-Coulomb model is employed as a simple and common constitutive soil model to compare the results. To achieve the study goals, firstly, the numerical modeling techniques are validated. Subsequently, the main parameters of the nonlinear kinematic hardening model are calibrated for the South Pars gas field region, which has not been done for this region in previous works. Detailed numerical models, including the fixed-base model and the pile-soil-structure (PSS) model, are then developed and analyzed using different selected ground motion records. The results indicate that considering the effect of PSSI has a significant effect on the seismic responses of the structure. Moreover, PSSI effect has a great dependence on the constitutive soil model. The results of this study are expected to provide useful insights into the seismic design of offshore structures in similar geological conditions.

Experimental analysis on the structural seismic behavior of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting

The structural seismic performance of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting is analyzed, and the structural strength of steel frame-precast SRC infill wall with lateral force resisting is improved. The structural seismic performance optimization model of SRC lateral force resisting wall based on buckling restrained brace is proposed. Through the finite element simulation software, the seismic performance and response results of ordinary steel frames, buckling restrained braced steel frames and a relatively new type of sacrificial-energy dissipation braced steel frames under earthquake are compared and analyzed to demonstrate the applicability and performance advantages of sacrificial-energy dissipation braced steel frames in the steel frame braced structure system. Under the action of horizontal earthquake, the supporting members experience reciprocating axial tension and compression cycles, which dissipate a large amount of seismic energy input into the structure. Therefore, the buckling restraint support method can be used in the structure to improve the support strength. Under horizontal reciprocating load action of earthquake, the ability to consume seismic energy through self-hysteresis of the brace is poor. Experimental research shows that, the unbalanced force formed in the beam of the frame beam under seismic action will form a plastic hinge at the beam end at both ends of the frame beam. Especially when the brace is buckling unstable and the stiffness of the frame beam is small, the plastic hinge effect at the beam end is significant. This phenomenon may cause damage to the frame beam or even local floor subsidence. The buckling restraint support has a full hysteresis area under axial tension and compression, and its mechanical performance is excellent. It is obviously superior to ordinary steel bracing in energy dissipation capacity and seismic performance. It can accurately predict the bearing capacity of reinforced concrete under strong earthquake, and the energy dissipation distribution is more in line with the requirements of “energy seismic design method”.

Prediction of post-fire seismic performance of reinforced concrete frames

Due to the importance of evaluating the seismic behavior of structures after a fire, a numerical study was conducted on RC frames using the detailed finite element method. The simulation process consists of two separate steps. The first step is heat transfer analysis to estimate heat distribution in the various elements of RC frames, and the second step is evaluating the post-fire seismic performance of the frames using thermal–mechanical analysis. The test specimens used to verify the proposed FE model include two RC frames with different beam-column bending capacity ratios, which are in two different conditions, including the specimens at ambient temperature as control specimens and fired specimens inside of the furnace chamber. In the heat transfer analysis step, the sensitivity of responses to two effective parameters, including the moisture content and the emissivity of the concrete surface has been investigated. In the post-fire analysis, among the various models presented for the post-fire behavior of concrete, three stress–strain models were selected for cyclic analysis of RC frames and the results were compared with the test data. Also, the bond-slip behavior of the concrete-steel interface has been simulated using the equivalent springs technique. It was seen from the comparison of the numerical results with the test data, that the proposed model accurately estimates the resistance and the dissipated energy of frames in each cycle. In addition, parametric studies showed that every 30 min increase in the fire duration based on the ISO 834 standard curve causes a 10% decrease in post-fire seismic resistance compared to the control specimen.

Seismic Behaviour of Multistorey Steel Framed Tall Buildings Using Intentionally Eccentric Braces

Braces with intentional eccentricity (BIE) are recently proposed to improve the seismic behaviour of conventional buckling braces (CBBs) by inserting intentional eccentricity along the brace length. Due to this eccentricity and the resultant bending moment, the BIE bends uniformly from small storey drifts and moves smoothly into the postbuckling behaviour under compression and sustains trilinear behaviour under tension. This behaviour delays the appearance of midlength local buckling which causes unstable energy dissipation. BIEs have a desirable postyielding stiffness which results in stable energy dissipation during cyclic loading and are capable of dissipating energy during low-intensity earthquakes. The seismic behaviour of structures with BIEs for use in buildings has not yet been investigated, specifically in tall buildings. Therefore, this study concentrates on investigating the seismic behaviour of tall buildings equipped with BIEs that uses a 3-dimensional (3D) finite element model in ETABS. In the first step, a 20-storey structure is designed using both eccentric brace frame (EBF) and BIE system and their seismic performance under the TABAS earthquake record is compared. In the second step, the seismic performance of a 25-storey irregular structure is assessed to evaluate the efficiency of the BIE system in irregular structures. Results show the desirable performance and energy dissipation capacity of the BIE system but it also shows large out-of-plane deformation in some cases.

Behavior and design of earthquake resistant concrete structure

Earthquake and seismic-resistant concrete structures are essential components and requirements of structural design. The performance and response of concrete structures during/after the earthquake event are significant to determine the condition of the structures as well as to identify the possibility of structural failure. The main objective is to investigate the appropriate method to evaluate the impact on the structure due to earthquakes based on closed-form solutions, and to determine its differences with the results of numerical modelling. The seismic behavior of structures is required to be designed in accordance with the minimum design requirements specified in the Standard. Seismic design, where ground behavior is considered, is presented as a significant part of design analyses, and ground movement and shaking, are associated with the ground deformation which is the primary seismic load consideration for the design of plain or reinforced concrete structures. The outcome of the longitudinal analysis provided the maximum axial and bending strain which is adopted to calculate the combined strain. These results of strain are considered with the design of concrete structures against Ultimate Limit State and Service Limit State design phases. Therefore, the results evaluate the effect of seismic design on the performance of the concrete structure.

An efficient reliability-based design of TMD & MTMD in nonlinear structures under uncertainty

One of the methods to improve the performance of tuned mass dampers is to combine the primary and auxiliary mass dampers in series, known as multiple tuned mass dampers. The mechanical properties of these dampers influence the seismic behavior of structures equipped with tuned mass dampers. Generally, the determination of TMD parameters to achieve optimal seismic behavior is defined in the framework of optimization problems. In structures with nonlinear behavior, there are several sources of uncertainty in the structure, which emphasizes the importance of using the reliability-based design optimization method. For this purpose, two strategies based on the meta-heuristic optimization and reliability-based design optimization method are used for the optimal design of TMD and MTMD. In the RBDO method, the optimal design is performed based on the objective function established on the target reliability of the structure. Furthermore, a hybrid metaheuristic method was developed based on BOA and CSS algorithms to increase search-ability. The results show the efficiency of the HBC algorithm in solving engineering design problems. Also, reliability analysis and sensitivity analysis are conducted on passive controlled structures to display the effect of uncertainty in mechanical parameters of the system and their importance in the reliability of the system. Also, the optimum design of TMD and MTMD was evaluated based on the target reliability using the efficient RBDO method. The results show that the RBDO strategy has an excellent ability to design TMD and MTMD with a good performance in reducing seismic responses.

Base Isolation Compared to Capacity Design for Long Corner Periods and Pulse-Type Seismic Records

Southern Romania is a geographic region with alluvial deposits. This soil type leads to rather long corner periods and provides as a particularity of the response spectrum an enlarged plateau. These conditions produce large displacement demands. Moreover, pulse-type ground acceleration records make this seismic area more unique. Research on the seismic behaviour of structures built under such unusual conditions is limited and Romanian engineers are not confident to apply alternative solutions such as base isolation. Although capacity design is still the regular design method applied in Romania, modern base isolation solutions may overcome the large displacement demand expectation produced by seismic events and fulfil immediate occupancy requirements. This study presents the seismic performance of an existing hospital from Bucharest, for which two seismic design solutions were applied: (i) classical approach based on capacity design and (ii) base isolation. Both approaches are compared in terms of drift, acceleration and base shear values. Static as well as non-linear dynamic analysis methods were applied.