Showing papers on "Earthquake resistant structures published in 2013"

Fragility Analysis of Retrofitted Multicolumn Bridge Bent Subjected to Near-Fault and Far-Field Ground Motion

Abstract: This paper focuses on the fragility-based seismic vulnerability assessment of retrofitted multicolumn bridge bents. Fragility curves are developed to assess the relative performance of various retrofit methods under both near-fault and far-field ground motions. A probabilistic seismic demand model (PSDM) is used in generating the fragility functions. Through nonlinear dynamic analysis, fragility curves are developed for multicolumn bridge bents retrofitted with four different retrofit techniques, specifically carbon fiber–reinforced polymer (CFRP) jacketing, steel jacketing, concrete jacketing, and engineered cementitious composite (ECC) jacketing. Following the performance-based evaluation approach, this study aims to investigate the effectiveness of different retrofitting methods to minimize the overall seismic vulnerability of deficient bridge bents. To investigate the seismic responses of the retrofitted bridge bents, a total of 40 earthquake excitations, of which 20 are near-fault and 20 are ...

Seismic Behavior of Building Frames Considering Dynamic Soil-Structure Interaction

Abstract: The seismic excitation experienced by structures is a function of the earthquake source, travel path effects, local site effects, and soil-structure interaction (SSI) influences. The result...

Shear and friction response of nonseismic laminated elastomeric bridge bearings subject to seismic demands

Abstract: Laminated elastomeric bridge bearings are commonly used in areas with low-to-moderate seismicity, although the applications are typically intended for service-level considerations such as thermal movements of the bridge superstructure. These components provide a potential source of displacement capacity frequently neglected in seismic design. An experimental program was carried out to evaluate the behavioral characteristics and performance of steel-reinforced, laminated elastomeric bearings, which had not been designed for seismic demands, as the primary quasi-isolation components for seismic events by permitting slip at the interface of the bearing and substructure. The rubber at the top of the bearing is vulcanized to a steel plate, which is bolted to the test frame to simulate a connection to the superstructure. At the base of the bearing, the elastomer directly contacts concrete representing the substructure, with no restraint of horizontal motion other than friction. The elastomeric bearings ...

Experimental investigation of the seismic response of bridge bearings.

Abstract: The Illinois Department of Transportation (IDOT) commonly uses elastomeric bearings to accommodate thermal deformations in bridges. These bearings also present an opportunity to achieve a structural response similar to isolation during seismic events. IDOT has been developing an earthquake resisting system (ERS) to leverage the displacement capacity available at typical bearings in order to provide seismic protection to substructures of typical bridges. The research program described in this report was conducted to validate and calibrate IDOT’s current implementation of design practice for the ERS, based on experiments conducted on typical full-size bearing specimens, as well as computational models capturing full bridge response. The overall final report is divided into two volumes. This first volume describes the experimental program and presents results and conclusions obtained from the bearing and retainer tests. The experiments described in this volume provide data to characterize force-displacement relationships for common bearing types used in Illinois. The testing program comprised approximately 60 individual tests on some 26 bearing assemblies and components (i.e., retainers). The testing program included (1) Type I elastomeric bearings, consisting of a steel-reinforced elastomeric block vulcanized to a thick top plate; (2) Type II elastomeric bearings, distinct from Type I bearings with a steel bottom plate vulcanized to the bottom of the elastomeric block, and a flat sliding layer with polytetrafluoroethylene (PTFE) and stainless steel mating surfaces between the elastomer and the superstructure; and (3) low-profile fixed bearings. Tests conducted to simulate transverse bridge motion also included stiffened L-shaped retainers, consistent with standard IDOT practice. Tests were conducted using monotonic and cyclic displacement protocols, at compression loads corresponding to a range of elastomer compression stresses from 200 to 800 psi. Peak displacements from initial position ranged from 7-1/2 in. to 12-1/2 in., depending on bearing size. Test rates were generally quasi-static, but increased velocities up to 4 in./sec were used for bearings with PTFE and for a subset of other elastomeric bearings. On the basis of all of the experimental findings, bearing fuse force capacities have been determined, and appropriate shear stiffness and friction coefficient values for seismic response have been characterized and bracketed.

Evaluating Code Criteria for Regular Seismic Behavior of Continuous Concrete Box Girder Bridges with Unequal Height Piers

Abstract: The seismic design and response prediction of irregular bridges supported on piers of unequal heights—a commonly adopted solution when crossing steep-sided valleys—represent a particularly challenging problem that is yet to be effectively addressed by seismic design code provisions worldwide. From a force-based design perspective, shorter piers are subjected to increased ductility demand, and consequently damage tends to localize in these relatively stiff piers at increasing seismic hazard levels. This paper presents an investigation of the seismic response of a few schemes of a three-span case-study continuous bridge (commonly encountered in practice), featuring two unequal piers with relative heights of 0.5, 0.64, 0.75, and 0.86, respectively. Static pushover and time history (under incrementally scaled-up actual records) nonlinear inelastic analyses are performed using OpenSees to check the validity of Eurocode 8 (EC8) and recently proposed AASHTO-LRFD provisions for regular seismic behavior of...

Demonstration of Compatible Yielding between Soil-Foundation and Superstructure Components

Abstract: Although the nonlinear behavior of rocking shallow foundations has been experimentally and numerically demonstrated as an effective tool to dissipate vibrational energy during seismic loading, the engineering community has yet to uniformly accept it as a targeted design mechanism for diffusing seismic energy in a structure. This paper presents results of a centrifuge test program that incorporated inelastic behavior into model building systems via yielding of both structural and foundation components. Three 2-story-1-bay building models were designed with similar layouts but different combinations of foundation and structural component yield strengths and were shaken with a similar suite of earthquake motions. Measurements of behavior of each of the model buildings are presented and cross-compared in terms of time history responses, hysteretic responses of the structural and foundation fuses, and maximum response parameters. A balanced design configuration, wherein the rocking foundation and struc...

Nonlinear Seismic Response and Parametric Examination of Horizontally Curved Steel Bridges Using 3D Computational Models

Abstract: The seismic behavior of horizontally curved steel bridges is more complex than straight bridges because of their curvature and other parameters. Studies that attempt to develop methods to efficiently predict their seismic response have been somewhat limited to date. A computational modeling approach was examined to assist with understanding the seismic behavior of these bridges. The computational, three-dimensional (3D) bridge models consisting of the concrete deck, steel girders, cross-frames, pier columns and caps, and abutments and footings were created in OpenSees and examined for accuracy via application to a representative, three-span continuous curved steel plate girder bridge in Pennsylvania. Sensitivity studies in the form of tornado analyses were also carried out to investigate the influence of critical curved bridge parameters on the seismic response using a group of representative bridges. Each representative bridge was subjected to an ensemble of synthetic ground motions, and seismic ...

Effect of Shear Wall Area to Floor Area Ratio on the Seismic Behavior of Reinforced Concrete Buildings

Abstract: An analytical study is performed to evaluate the effect of shear wall area to floor area ratio on the seismic behavior of midrise RC structures. For this purpose, 24 midrise building models that have five and eight stories and shear wall ratios ranging between 0.51 and 2.17% in both directions are generated. Then, the behavior of these building models under earthquake loading is examined by carrying out nonlinear time history analyses. In the analyses, seven different ground motion records are applied to the building models, and the average of the obtained data is used in the evaluation of the seismic performance. Main parameters considered in this study that affect the overall seismic performance of the buildings are the roof and interstory drifts and the base shear responses. The analytical results indicate that at least 1.0% shear wall ratio should be provided in the design of midrise buildings to control the drift. In addition, when the shear wall ratio increases beyond 1.5%, it is observed th...

Large-Scale Experimental Studies of Structural Control Algorithms for Structures with Magnetorheological Dampers Using Real-Time Hybrid Simulation

Abstract: Real-time hybrid simulations using large-scale magnetorheological (MR) dampers were conducted to evaluate the performance of various structural control strategies to control the seismic response of a three-story steel-frame building. Magnetorheological dampers were installed in the building to limit the story drift to less than 1.5% under the design-basis earthquake (DBE). The laboratory specimens, referred to as experimental substructures, were two individual MR dampers, with the remainder of the building modeled as a nonlinear analytical substructure. The experimental technique enables an ensemble of ground motions to be applied to the building, resulting in various levels of damage, without the need to repair the experimental substructures because the damage will be within the analytical substructure. Five different damper control algorithms, including passive and semiactive control algorithms, were selected. An ensemble of five ground motions scaled to the DBE was used for the real-time hybrid...

Analytical investigation of response modification (behaviour) factor, R, for reinforced concrete frames rehabilitated by steel chevron bracing

Abstract: Steel bracing of reinforced concrete (RC) frames has received noticeable attention in recent years as a retrofitting measure to increase the shear capacity of the existing RC buildings. In order to evaluate the seismic behaviour of steel-braced RC frames, some key response parameters, including the ductility and the overstrength factors, should first be determined. These two parameters are incorporated in structural design through a force reduction or a response modification factor. In this paper, the ductility and the overstrength factors as well as the response modification factor (or seismic behaviour factor) for steel chevron-braced RC frames have been evaluated by performing inelastic pushover analyses of brace-frame systems of different heights and configurations. The effects of some parameters influencing the value of behaviour factor, including the height of the frame and share of bracing system from the applied lateral load have been investigated. It is found that the latter parameter has a more ...

Pivot hysteresis model parameters for reinforced concrete columns, joints, and structures

Abstract: Inelasticity in reinforced concrete (RC) frame structures due to seismic loads is generally considered to be concentrated in the form of hinges in beams, columns, and joints. In this paper, the parameters for rectangular RC beams, columns, and nonseismically detailed beam-column joints are suggested, keeping the simplicity of the original pivot hysteresis model. With the proposed parameters, the existing model can be effectively used to perform nonlinear dynamic analysis of nonseismically detailed RC structures. Two major improvements in the parameters for columns as compared to the original model are: 1) new parameters cover the complete range of axial load on the column; and 2) it gives due consideration to the transverse reinforcement on pinching behavior of the members. Additionally, several parameters are proposed for poorly detailed exterior joints. It is shown that the model with the proposed parameters nicely captures the hysteretic behavior of RC members, joints, and structures.

Comparative Study of Seismic Response for Seismic Coefficient and Response Spectrum Methods

Abstract: Right from the evolution of the earth, Earthquakes have been cause great disasters in the form of destruction of property, injury and loss of life to the population. The effective design and construction of earthquake resistant structures has much greater importance in this country due to rapid industrial development and concentration of population in cities. In this thesis, the earthquake response of symmetric multi-storied building by two methods are studied. The methods include seismic coefficient method as recommended by IS Code and modal analysis using response spectrum method of IS Code in which the stiffness matrix of the building corresponding to the dynamic degrees of freedom is generated by idealizing the building as shear building. The responses obtained by above methods in two extreme zones as mentioned in IS code i.e. zone II and V are then compared. Test results Base Shears, Lateral Forces and Storey Moments are compared.

A new scheme for the seismic retrofit of multi-span simply supported bridges

Abstract: There are two alternative strategies that a designer may adopt and combine when faced with the retrofitting of a bridge: (a) the increase in the capacity or (b) the reduction in the actions of the structure. In this article, a new scheme, based on the second strategy, is proposed for the retrofit of existing multi-span simply supported (MSSS) bridges. The reduction in the actions of the bridge was mainly achieved by utilising an external restraining system consisting of I-shaped steel piles driven in the backfill soil and a slab that is the pile-cap of the piles. The restraining system was preliminarily designed and assessed in an existing MSSS bridge system, whose deck slab was made continuous. The existing and the retrofitted bridge were analysed by means of non-linear dynamic time history analysis and their response was compared in terms of serviceability and earthquake resistance performance. The study showed that the retrofitting scheme enhanced effectively the earthquake resistance of the existing b...

Earthquake-Resistant Structures: Design, Build, and Retrofit

Abstract: Earthquake engineering is the ultimate challenge for structural engineers. Even if natural phenomena involve great uncertainties, structural engineers need to design buildings, bridges, and dams capable of resisting the destructive forces produced by them. These disasters have created a new awareness about disaster preparedness and mitigation. Before a building, utility system, or transportation structure is built, engineers spend a great deal of time analyzing those structures to make sure they will perform reliably under seismic and other loads. The purpose of this book is to provide structural engineers with tools and information to improve current building and bridge design and construction practices and enhance their sustainability during and after seismic events. The author explains the latest theory, design applications and Code Provisions. This book features seismic design and retrofitting techniques for low and high raise buildings, single and multi-span bridges, dams and nuclear facilities. The author also compares and contrasts various seismic resistant techniques in the United States, Russia, Japan, Turkey, India, China, New Zealand, and Pakistan.

Behavior of Reinforced Concrete Wide Concealed-Beam/Narrow-Column Joints under Lateral Earthquake Loading

Abstract: This study discusses an experimental program carried out for evaluating the behavior of reinforced concrete wide concealed-beam/narrow-column joints when subjected to lateral earthquake loading. The first part of the study focuses on as-built joints, designed and constructed without taking earthquake loads into account. The second part of the study concentrates on the seismic performance of the same joints tested in the first part, except that the reinforcement details are improved in part in accordance with ACI 318-08 provisions for earthquake-resistant structures. Four full-scale interior and exterior beam-column subassemblages were tested under quasi-static cyclic lateral loads. The joints satisfied some of the ACI 318-08 design and steel detailing requirements but still violated the dimension limitations specified in the same code or recommended by ACI 352R-02. All joint specimens developed considerably improved seismic performance, manifested by preventing or delaying joint shear failure, higher lateral load capacities, lower stiffness degradation, larger energy dissipation capacities, and a stable overall hysteretic response when compared with the as-built joints.

A new control algorithm to protect nonlinear base‐isolated structures against earthquakes

Abstract: SUMMARY Currently, nonlinear base isolation systems are widely used in the construction of earthquake resistant structures. However, they are found to be vulnerable in near-fault regions as a result of long-period pulses that may exist in near-source ground motions. Various control strategies including passive, active and semi-active control systems have been studied in order to handle this issue. In this study, a semi-active control algorithm based on the different performance levels anticipated from an isolated building during different levels of ground shaking was developed. The proposed performance-based algorithm is based on a modified version of the well-known semi-active skyhook control algorithm. A series of analyses were performed on the base-isolated benchmark building, suggested by the American Society of Civil Engineers committee, subject to seven pairs of scaled ground-motion records. The results proved that the new control algorithm is successful in improving structural and nonstructural performance of isolated buildings under near-fault earthquakes. Copyright © 2012 John Wiley & Sons, Ltd.

Axial Hysteretic Modeling of Cold-Formed Steel Members for Computationally Efficient Seismic Simulation

Abstract: Analysis and design of cold-formed steel (CFS) structures subjected to seismic forces usually focuses on the behavior of systems such as strapped/sheathed shear walls. Experimental data from tests on these systems offers limited information concerning the seismic performance of the individual CFS components or other configurations of shear walls. Buckling and cross-sectional deformations (unique to thin-walled steel sections) highly influence the response under cyclic loading of CFS members and the associated systems. Therefore, accurate and computationally efficient hysteretic models are required to predict the seismic performance of individual CFS components and CFS buildings. Experimental data from twenty-four axial tests is utilized to calibrate a hysteretic model that represents the axial cyclic response of cold-formed steel C-section structural framing members. The model includes strength degradation, unloading stiffness degradation and pinching behavior of the observed experimental response. Model parameters and damage rules are calibrated for local, distortional and global buckling based on the hysteretic energy dissipated. The calibrated parameters can be utilized to develop a toolbox of nonlinear hysteretic springs to represent framing axial members in CFS structures for seismic analysis and facilitate performance based earthquake engineering of CFS structures.

Aseismic Analysis of Circular Deep Grouting for Tunnel Surrounding Rock in Strong Earthquake Zone

Abstract: Many tunnels were severely damaged during high-intensity earthquakes in recent years, especially for those in mountainous areas. This paper analyzes the seismic responses of the circular deep grouting technique for mountain tunnels with surrounding rocks. Eight circular, deep grouting, pre-reinforcement schemes are simulated using 3D Finite Element Method. The deformation and stress characteristic and dynamic responses of the tunnel structure are analyzed. Results demonstrate that different grouting schemes should be applied for tunnel structure in the high-intensity areas. A new seismic performance evaluation approach is proposed in the paper based on the maximum relative displacements of adjacent locations on the tunnel lining. This evaluation method provides a better interpretation of the tensile and compressive states of tunnel structures that are subject to strong ground motion during an earthquake. The approach described in the paper provides guidance to seismic design and construction of tunnels in seismic, active, mountainous areas.

Seismic Evaluation and Retrofit of Deteriorated Concrete Bridge Components

Abstract: Corrosion of steel bars in reinforced concrete structures is a major durability problem for bridges constructed in New York State (NYS). The heavy use of deicing salt compounds this problem. Corrosion of steel bars results in loss of steel cross section, deterioration of bond between concrete and reinforcing bars, and more importantly, in most cases, it results in unsymmetrical concrete sections that are susceptible to shear stresses produced by torsion. Though earthquake frequency of occurrence and expected ground accelerations in NYS is less than in western states, the potential for earthquake damage in or around NYS is still very real. Given the level of deterioration in many reinforced concrete bridges in NYS, they are considered very vulnerable to major damage during a moderate seismic event. There is an urgent need for proper guidance for evaluation of deteriorated reinforced concrete bridge components that could assist structural engineers in estimating the reserved strength of deteriorated bridges and designing cost-effective methods for retrofit. Proper evaluation and retrofit of existing deteriorated reinforced concrete bridges will limit the collapse of bridges during moderate seismic events in NYS and the surrounding states, and consequently save people’s lives. The findings of this investigation suggest the need for seismic retrofit of deteriorated reinforced concrete bridge columns, particularly those with corroded lap splice in longitudinal reinforcement. The study also suggests the need for retrofit of corroded pedestals over piers and abutments, as they may cause sudden unseating of girders.

Analisis Perbandingan Simpangan Lateral Bangunan Tinggi dengan Variasi Bentuk dan Posisi Dinding Geser. Studi Kasus: Proyek Apartemen The Royale Springhill Residences

Abstract: A building should at least be able to bear the loads that work on the structure . Lateral loads such as wind loads and seismic loads that can cause lateral deflection and gravity loads including dead load and live load. The higher the building , the lateral deflection occurs also greater in atas. Structure Engingeer planners are required to better understand the design of earthquake resistant structures that are not just simply follow in designing the building , but must comply with the Earthquake Resilience Planning Procedures for Building a goal is for earthquake resistance of building structures are planned to function properly in designing a building structure must be considered rigidity , stability of the structure withstand any loading imposed on them and how the behavior of the structure to withstand such loads . ETABS is a 3D Extended program of Building Systems of Computer and Structure inc that use the Windows operating system . The use of simulation program ETABS memperlihat pattern collapse was going to happen so it can be input for the planning and construction of high-rise buildings better . In this study will be compared to the horizontal deflection obtained from the comparison position and shape shear walls . Results from this research is a comparison of deflection that occurs , a review of the limits of serviceability and ultimate limit each building models to be compared .

Post-Earthquake Bridge Damage Mitigation – Post-Earthquake Damage Repair of Various Reinforced Concrete Bridge Components

Abstract: The main objective of the present study was to develop repair methods using carbon fiber reinforced polymer (CFRP) for various reinforced concrete (RC) bridge components. A detailed review of damage and repair in past earthquakes was conducted and the data were compiled in tables and gaps in available repair methods were identified. Practical methods were developed to access the condition of an earthquake damaged bridge structural components in terms of apparent damage states (DS’s). For this approach to be successful, internal earthquake damage was quantified and correlated to a series of visible DS’s. DS’s defined for bridge columns were used as the framework for other components. Repair design recommendations and design examples were developed to aid bridge engineers in quickly designing the number of CFRP layers based on the apparent DS. Repair methods to repair bridge components such as abutments, shear keys, girders, and cap beam-column joints were developed. To simplify repair, a new equation was developed to calculate the effective strain in the CFRP for side-bonded CFRP configuration. In cases where the extent of damage precludes an economically feasible repair, reconstruction of damaged bridge component is recommended. Because the available data base for components other than columns is limited, many simplifying and conservative assumptions were made about the residual capacity of damaged components.

Design And Analysis Of Base Isolated Structures

Abstract: Development in the design of earthquake resistant buildings has been growing since about 100 years ago. In the design of earthquake resistant buildings, the main aspects to consider are life safety and damage reduction on architectural element caused by the earthquake. However, with the development of age, modern buildings contain sensitive and expensive equipment that become vital for business, commercial, education and healthcare. Hence, the equipment inside the building needs to be protected when the earthquake occurs. The basic principle of a base isolation system is to provide flexibility in the building and at the same time provide damping to prevent amplification caused by the earthquake. By placing structure on the base isolation system, it will prevent horizontal movement of the ground transferred to the structure and produce a significant reduction in the acceleration of the earthquake. This paper explains about the design and analysis of a base isolated structure. The base isolation system used is Lead Rubber Bearings, High Damping Rubber Bearings, and a combination of those two bearings on a 20-story building. The main focus of this paper is the comparison of the response between a fixed base structure and the base isolated structure and the comparison of the response generated by each type of base isolation system. The compared responses are the natural vibration period, the base shear, and the base isolation hysteretic curve. The design procedure used is based on SNI 1726-2012. The conclusion of this paper is the effectiveness of a base isolated structure is based on the generated response.

Experiences with Friction Pendulum TM seismic isolation in California

Abstract: Seismic isolation shines as the top performance system for earthquake resistant structures, having involved a large variety of essential facilities since the late 1980s. Within the available devices, friction pendulum bearings present beneficial dynamic characteristics which are not intrinsically provided by other isolation systems. Developed and engineered by Earthquake Protection Systems, Inc. in California, these bearings have become a popular choice for designers. This paper firstly presents the experience of Skidmore, Owings & Merrill LLP (SOM) on the design of friction pendulum base isolated buildings, with systems evolving from the single concave to the Triple Friction Pendulum TM

A study of seismic assessment of a govt. middle school in ganaihamam, baramullah in j&k

Abstract: Earthquakes are one of the nature’s greatest hazards on our planet which have taken heavy toll on human life and property since ancient times. The sudden and unexpected nature of the earthquake event makes it even worse on psychological level and shakes the moral of the people. Man looks upon the mother earth for safety and stability under his feet and when it itself trembles, the shock he receives is indeed unnerving. Mitigation of the devastating damage caused by earthquakes is of prime requirements in many parts of the world. Since earthquakes are so far unpreventable and unpredictable, the only option with us is to design and build the structures which are earthquake resistant. Accordingly attempts have been made in this direction all over the world. Results of such attempts are very encouraging in developed countries but miserably poor in developing countries including our country India. This is proved by minimal damage generally without any loss of life when moderate to severe earthquake strikes developed countries, where as even a moderate earthquake cause’s wide spread devastation in developing countries as has been observed in recent earthquakes. It is not the earthquake which kills the people but it is the unsafe buildings which is responsible for the wide spread devastation. Keeping in view the huge loss of life and property in recent earthquakes, it has become a hot topic worldwide and lot of research is going on to understand the reasons of such failures and learning useful lessons to mitigate the repetition of such devastation. If buildings are built earthquake resistant at its first place (as is being done in developed countries like USA, Japan etc) the devastation caused by earthquakes will be mitigated most effectively. The professionals involved in the design/construction of such structures are structural/civil engineers, who are responsible for building earthquake resistant structures and keep the society at large in a safe environment. Apart from the modern techniques which are well documented in the codes of practice, there are some other old traditional earthquake resistant techniques which have proved to be effective for resisting earthquake loading and are also cost effective with easy constructability.

Damage Detection in RC Earthquake Systems Using Dense Sensor Networks

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An experimental investigation on flexural behaviour of stainless steel fiber reinforced concrete beam elements

Abstract: Concrete is the most widely used construction material because of its specialty of being cast into any desirable shape. Ductility and energy absorption capacity are the main requirements of earthquake resistant structures. However the conventional concrete has low tensile strength, lower energy absorption and little resistance to cracking. Therefore, it cannot fulfill the requirements of the earthquake or seismic resistant structure. Extensive researches have shown that the most significant influence of the inclusion of steel fiber in concrete is to delay and control tensile cracking of the composite material. The primary variables are fiber content and matrix composition. The addition of steel fiber to matrix leads to improvement in several properties of concrete. In this investigation the strength properties are determined by using different geometrical steel fibers. The various parameters like load carrying capacity, stiffness, ductility character and energy absorption capacity has to be analyzed.