Seismic Isolation, Structural Health Monitoring, and Performance Based Seismic Design in Earthquake Engineering

New structural seismic isolation system named Spherical Foundation Structural Seismic Isolation (SFSSI) system which has been discovered and first prototyped on a 104 m height (26 storey) building example is presented. Creation of SFSSI system aimed to build structural seismic isolation system, of which period must be more than the predominant period ground motion of majority existing earthquakes including near-fault zones also. As known, classical period-dependent isolation systems and not isolated (fixed base-FB) buildings are vulnerable under long-period earthquakes and it is required to design resistant structural system components. For this purpose, a system has been realised as a structure with inverse pendulum system’s behavior. Structure foot base and foundation contact surface are formed in spherical appearance and they are separated by known Lead Core Rubber Bearing (LCRB) or Laminate Rubber bearing (LRB) isolators which are installed through spherical contact surfaces. Dampers are installed through base (structure foot) plate counter for controlling system’s response. This allows spherical foundation’s turning around gyration center through rubber bearing contact and keeps the same behavior to superstructure. In the SFSSI system it is possible to keep the natural period of the structure in a large interval, which is much more than predominant period of ground motion of the majority of the existing earthquakes including near-fault zones also. In this study, behavior of the both classical base-isolated building using LCRB and not isolated-FB building has been investigated under long-period ground motion. Obtained results are compared with SFSSI system with the same stiffness and equivalent damping and number of LCRB which was installed on spherical foundation. It was shown that, SFSSI system deprived from known deficiency period-dependent isolation systems and it is the progress of the new type earthquake-resistant structures. SFSSI system exhibits improved Roly-poly (‘Haciyatmaz’, ‘Okiogary-Koboshi’) behavior. We believe that as Roly-poly, structures with SFSSI system will symbolize the ability to have success overcome adversity, and recover from misfortune.

An approach to develop resilient structures using seismic response control with a semi-active system is introduced. Actual system performance of control device installing to the practical building structure is evaluated with a RTHS (real-time hybrid simulation) test and an online simulator with the shaking table of Kobe University is used. Specifications of this online simulator system are explained in detail. As one example operating the RTHS tests, performance evaluation for the mid-story isolated building structure controlled by a semi-active device is focused. First, mechanical properties of the testing apparatus of the MR (magneto-rheological) rotary inertia mass damper used for semi-active control are quantified by the device tests, and then numerical simulation model of this damper is provided. Next, the RTHS test studies are operated and the test results are compared with the pure numerical simulation results by the fully modeled analyses. Validity of this online simulator and exactness of numerical model of the semi-active damper are confirmed. Moreover, reproducibility and reliability of the operation for the RTHS tests are evaluated by observing the displacement and the acceleration generated on the shaking table. As a result, it is assured that both the target displacement and acceleration of the shaking table were accurately reproduced under the real-time calculation in this online simulator. And it is confirmed that performance evaluations for the actual test specimen of the semi-active control device were also accurately done through the RTHS test method by using the shaking table.

The purpose of this study is to demonstrate the applicability of the Horasan mortar friction interface, which has been used for many long years in the past historical periods, as a seismic isolator in lightweight building structures with no overturning moment. To this end a four-storey hospital building has been selected as an example. Using the beyond-linear mathematical model simulation the results for Horasan mortar, stainless steel, gray-iron/mortar friction interfaces have been compared. For each interface the base acceleration is seen to be reduced in the ratio of 45, 38, 33% compared to the built-in building. For complete these favorable results-NSI device’s material stress- and strain rang assessment have been modeled by the FEM in ANSYS, LS-DYNA environments and compute results to be compared to the related material ultimate values. Generally different devices are used to restore the superstructure to the initial position. In this study it has been proven that the earthquake has a restoring property and this phenomena have been used as the indirect restoring device. Full details of the application of Horasan mortar, which is economically favorable and has been used for many centuries in the history as a friction interface, has been given.

The University of British Columbia (UBC) and the British Columbia Ministry of Transportation and Infrastructure in Canada, have been instrumenting key structures in recent years to provide confirmation of their seismic capacity, assist in focusing retrofit efforts, detect damage from any cause, and provide rapid damage assessment of those structures following a seismic event. The program now includes more than 15 monitored bridges and is expanding to include public schools and other buildings. The newest addition to the bridge monitoring program is the incorporation of an earthquake early warning system developed at UBC. This paper describes how the EEW system will be used as part of the existing seismic structural health monitoring program in British Columbia.

Department of Earthquake Engineering of Kandilli Observatory and Earthquake Research Institute, Boğaziçi University (DEE-KOERI) has designed and been operating a significant number of structural monitoring networks in Istanbul. They are installed in a large number of historical structures (i.e., mosques, minarets, and museums), lifeline structures across the Bosphorus (i.e., suspension bridges and tunnels) and several tall buildings including the Sapphire tower, currently the tallest building in Europe. The structural monitoring networks record the dynamic motions of the structures continuously, and the data are transmitted in real time to the monitoring center at the DEE-KOERI. The majority of the systems use accelerometers for monitoring. Some structures are also instrumented with tiltmeters and GPS sensors. In-house real-time modal analysis software is used to process and analyze the data. The software includes data processing, spectral identification, and animation modules. The results are displayed in real time, showing the time variations of modal properties and the structure’s configuration. This chapter provides an overview of these monitoring systems in Istanbul. Moreover, it presents major findings related to the dynamic response properties of monitored structures particularly focusing on structural response to long-distance, long-period earthquakes; on the sensitivity of dynamic modal parameters to variations in atmospheric conditions; on structural response characteristics due to explosions; and on damping in tall buildings.

Hagia Sophia, during its history, was affected by many earthquakes, resulting in several reconstructions of parts of its main dome and main arches. Being one of the most important buildings of the mankind’s common heritage and given Istanbul’s high seismic risk, the worthiness of the present-day structure in a future major earthquake and what, if any, strengthening interventions will be needed to carry the edifice intact to the future were reviewed. The review encompasses studies conducted on structural and sub-structural assessments, material characterization, linear and nonlinear finite element dynamic analysis, nondestructive structural testing, ambient vibration testing, and the analysis of the strong motion data. The expected earthquake response, possible failure modes, and the retrofit proposals for the improvement of the earthquake performance of Hagia Sophia covered in different studies were comparatively and critically analyzed.

Over the last 25 years there have been a series of academic efforts to understand the particulars associated with earthquake performance and vulnerability of Hagia Sophia. Linear and nonlinear structural analyses; literary investigations; non-destructive tests and investigations involving its construction materials, foundations and main structural elements; ambient vibration tests; monitoring its earthquake response with the help of an accelerometric network were among them. More recently the foci of efforts were the analysis of long-term dynamic response of Hagia Sophia to earthquakes and variations in atmospheric conditions, shake table testing of a scaled model of the structure, analysis of recently added tiltmeter recordings, evaluation of strengthening alternatives and monitoring of its static deformations via laser technology. This contribution presents an overall picture of the research efforts carried out so far on earthquake response analysis of Hagia Sophia, emphasizing the studies over the last 5 years.

The mosques are the most important pieces of Islamic culture in terms of their architectural and structural properties. The mosques and complexes are built in the center of living areas and constituted important structures in the surroundings in Islamic culture. Therefore, it is very common to observe the mosques in almost every city center. In this study, Merzifon Dönertaş Mosque, which is located in the city, center of Merzifon and which takes an important part among Amasya’s historical monuments is investigated by means of static and dynamic analyses by the use of finite element method. The material properties and formulas, given in the literature, have been considered in order to obtain the structural behavior of the structure. The results of the analyses show that the most critical parts of the mosque.

In this study was investigated the possibility of using the recorded micro-tremor data on ground level as ambient vibration input excitation data for investigation and application Operational Modal Analysis (OMA) on the bench-scale earthquake simulator (The Quanser Shake Table) for model cold formed steel (cfs) structures. As known OMA methods (such as EFDD, SSI and so on) are supposed to deal with the ambient responses. For this purpose, analytical and experimental modal analysis of a model (cfs) structure for dynamic characteristics was evaluated. 3D Finite element model of the building was evaluated for the model (cfs) structure based on the design drawing. Ambient excitation was provided by shake table from the recorded micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition is used for the output-only modal identification. From this study, best correlation is found between mode shapes. Natural frequencies and analytical frequencies in average (only) 2.99% are differences.

A novel approach of system characteristic matrix’s correction in modal identification from ambient vibration is presented. As a result of this approach, actual system characteristic matrices are determined more accurately with minimum error. It is reflected on to updating system parameters more reliable. In first approximation, actual system characteristic matrices determined by singular value decomposition of block Hankel matrix, which build from the response correlation matrix. In second approximation, to make the system characteristic matrices optimal definite, for black-box modeling the input–output relation of the system used Kalman theory. Covariance of the nonmeasurable process noise and measurement noise matrixes are contained in Riccati equation are determined by expressing Hankel matrix’s multiplicities from eigensolution of the system state matrix obtained in previous iteration. Another word process and measurement noises covariance matrixes indirectly is constructed only from measured output data. These iterations are repeated until satisfying estimated error. As a result of these iterations, actual system characteristic matrices are determined more accurately with minimum error. Then, from determined system characteristic, matrices are extracted system modal parameters. These system modal parameters are used for the system modal updating for which direct and iterative methods are applied. Supporting to this algorithm realized code maybe interfaced with finite element codes.

An overview of current performance-based methodologies utilized for design of tall buildings is presented. The reasons why common prescriptive code provisions are incapable of addressing the needs of tall building design engineers are explained. The performance objectives commonly associated with tall building design are identified and the evolution of current component-based performance objectives to a more rigorous and fully probabilistic approach to performance-based design is discussed. Modeling and acceptance criteria associated with various performance-based design guidelines are explained and special issues such as selection and scaling of ground motion records, soil–foundation–structure interaction issues, and seismic instrumentation and peer review needs are discussed.

Hydrocarbon steel pipes have undertaken a very important and fundamental role in the oil and gas industries in the world. Although these pipes are simple structural forms, their structural behaviors are very complex and challenging for the structural engineering community. One of the fundamental problems for pipelines is plastic deformations under internal pressure. This study focuses on to develop a methodology for the performance evaluation of hydrocarbon steel pipes under internal pressure. In this perspective, a hydrocarbon pipe, which is used in natural gas pipelines, is modeled by nonlinear finite element model (FEM) and investigated in terms of structural behavior under different internal pressure conditions; operating pressure (100 bar), design pressure (150 bar) and high pressure (250 bar). In order to obtain an accurate solution, the finite element model is calibrated with a hydrostatic test, which is conducted on a pipe under 133 bar.

It is known that structures act a nonlinear movement when strong ground motion cycle begins. Energy concept has been progressive tool to evaluate the structural system associated with performance-based design. Energy-based design can be expressed as the balance of energy input and the energy dissipation capacity of the structure. Researches that have been usually done for single degree of freedom system are needed for multi degree of freedom systems (MDOFs) in framework of the energy-based design methodology. In this paper, energy parameters in term of total energy input and hysteretic energy are evaluated and observed changes in height of the buildings for the energy concept. Structures are selected to demonstrate low and medium-rise steel inverted V-braced frames examined in linear and nonlinear dynamic time history analysis. The results are developed to obtain seismic energy demands.

The article presents the main principles of a new approach to the calculation of reinforced concrete structures. A new chart-energy method for the calculation is developed with an additional stress–strain state stage. It helps to solve the problem of a stochastic crack. The absence of transition from a state of continuity to the state of “section with a crack” does not allow to make uniform the calculation of strength, stiffness, and fracture toughness. According to the energy theory of reinforced concrete resistance at the time of crack formation stretched concrete energy redistributes to armature, which acts as a brake element and restrains crack propagation in the cross section. The sudden nature of a crack appearance is accompanied by an instantaneous change of cross-section stress state. The change is dynamic in nature. The problem of a reinforced concrete section transition from “solid” state to state “with a crack” in a stretched zone and determining the depth of cracks was solved. The proposed approach allows to create a uniform methodology for calculating strength, stiffness, and fracture toughness, as well as offer a number of constructive measures to improve the earthquake resistance of buildings and structures. A series of experiments was conducted in relation to key provisions of the energy theory of reinforced concrete resistance. The proposed variant of a seismic load damper will significantly dissipate the earthquake energy and protect the structural system from damage. The use of internal clamps in vertical elements significantly increases a resistance to shear, while enhancing the junction of column and slab.

The effects of axial compressive load and internal viscous damping on the free vibration characteristics of Timoshenko beams are carried out using the dynamic stiffness formulation and the differential transformation method. The governing equations of motion are derived using the Hamilton’s principle. After the analytical solution of the equation of motion has been obtained, the dynamic stiffness method (DSM) is used and the dynamic stiffness matrix of the axially loaded Timoshenko beam with internal viscous damping is constructed to calculate natural frequencies. Moreover, an efficient mathematical technique called the differential transform method (DTM) is used to solve the governing differential equations of motion. The calculated natural frequencies of Timoshenko beams with various combinations of boundary conditions using the DSM and DTM are presented and compared with the analytical results where a very good agreement is observed.

Reinforced concrete (RC) square columns are vulnerable to sudden dynamic impact loadings such as vehicle impact to bridge column or air blast shock due to blast effects. In this experimental study, RC square columns strengthened with CFRP strip subjected to sudden low-velocity lateral impact loading were investigated. A free falling weight test setup was used to apply the impact loading to RC square columns. The test specimens were manufactured with square cross sections with one-third geometric scale. In scope of the study, four test specimens were manufactured and tested. The main variables considered in the study were the application point of impact loading and CFRP strip spacing. A 9.0 kg mass was allowed to free fall from a height of 1.0 m to apply the impact loading on the columns. During the impact tests, acceleration, impact force, column midpoint displacement, and CFRP strip strains measurements were taken. The general behavior of test specimens, collapse mechanisms, acceleration, displacement, impact load, and strain–time relationships were interpreted and the load–displacement relationships were obtained. The data from the experimental study was used to investigate the effect of variables on the impact performances of RC columns.

Precast concrete frame systems are widely preferred for the single storey industrial buildings in Turkey and Europe due to its rapid and economical construction practice. Field investigations after past major earthquakes revealed that the damage in such structures was primarily due to the improper detailing in beam–column connections and lack of required lateral stiffness. In this study, two different precast industrial buildings, damaged during the 1999 Marmara earthquake, were numerically investigated. The seismic performances of the buildings were evaluated by using Incremental Equivalent Seismic Load Method and strain-based damage definitions as recommended in Turkish Earthquake Code. The analytical results obtained from performance evaluations are compared with the findings from the field investigations.

Reinforced concrete (RC) beams with light transverse reinforcement are vulnerable to shear failure during seismic response. The codes require the use of a certain amount of transverse reinforcement to resist the expected total shear demand to prevent brittle shear failure at plastic hinge regions. Some codes ignore the contribution of concrete to shear strength when the shear demand due to seismic effects is above a certain level. This research studied the contribution of concrete to shear strength of beams reinforced with longitudinal bars and polypropylene fibers (PPF). The beams including two reference and two macro-synthetic polypropylene fibers reinforced concrete (PPFRC) beams tested under concentrated loads at mid-span to determine the shear strength. The variable parameters are volume fraction of polypropylene fibers (V_f) and shear span-to-depth ratio (a/d). Deflection of the beam and the cracking pattern were monitored during the test at different stages of the monotonic loading until failure. When the beams with a/d = 2.5 and 3.5 are compared, it is concluded that the contributions of PPF to the shear strength at ultimate state are 0.39 MPa and 0.34 MPa, respectively, in case of the beams with volume fractions of PPF equal to 1.0%. It is observed that the contribution of PPF to shear strength decreases with the increasing a/d. It can also be stated that the dissipated energies under the area of load-deflection curve by the PPFRC beams are 341 and 226 times the energy dissipated by a/d = 2.5 and a/d = 3.5 reference beams, respectively.