Seismic Performance Comparison of Simply Supported Hollow Slab on Pile Group Structure with Different Operational Category and Shear Panel Damper Application

This study is aimed to compare the seismic performance of simply supported hollow slab on pile group (SHSPG) structures designed as “critical” and “essential” viaducts with shear panel damper (SPD) devices. There were three numerical models to be compared, namely SHSPG-A, SHSPG-B, and SHSPG-C. SHSPG-A is a “critical” viaduct with 35 piles per one pile head. SHSPG-B is an “essential” viaduct with 18 piles per one pile head. SHSPG-C is an “essential” viaduct with 18 piles per one pile head plus sixteen SPDs. Numerical models considered the prestressing effect of the spun pile. Nonlinear time history analyses were executed using seven pairs of recorded ground motions that had been scaled and adjusted to the seismic characteristics of Yogyakarta, Indonesia. As the result, the performance level of SHSPG-A was much better than SHSPG-B. The SPDs application could maintain SHSPG-C’s performance at the same level as SHSPG-A and dissipate 34.28%-53.03% of the seismic energy

Detection of defects in concrete structures using vibration technique

This thesis investigates the dynamic behaviour of reinforced concrete beams as they are loaded to failure. Four beams have been investigated. Two types of crack pattern and two types or reinforcement pattern were the main variable parameters. Partially bonded reinforcement as artificially created (by greasing the bars) and positioned at the center third span in two of the four beams investigated. The remaining two beams had conventional bonded reinforcement. Flexural and diagonal splitting patterns were created by loading mechanisms individually applied on two beams of each type of reinforcement. Stage by stage application of static loadings was used. Steady state vibration tests were applied at prior to loadings the beams and at several load stages as gradually increasing defects occurred. There are four parts to this investigation and these are presented in this thesis. The first part investigates the accuracy of several techniques dealing with signal parameters from a digital response spectrum in the signal processing. A logic geometry was developed and was applied on the line spectra of the response spectrum. Numerical evaluation found that the error induced in the proposed technique decreased exponentially with increasing numbers of cycles. A maximum of 0.17% errors may exist when examining 100 cycles of the frequency of interest. A regression analysis was used to achieve further accuracy of the results. The second part investigates the jump phenomenon of mechanical exciters and the sharp drop phenomenon of magnetic exciters. Both of which may confuse the analysis of structural dynamic behaviour. By accounting for the stiffness of the magnetic field of the magnetic exciter in a mathematical model, the jump phenomena was shown to be due to the effect of the reflected force in the excited structure. Practical equations were also proposed to relate absolute to relative parameters. The third part of the thesis concerns the algorithms required in filter processing and includes the development of a computer solution. Two algorithms were developed to obtain coefficients of a polynomial equation which was set up from elementary equations and from a rational function respectively. The algorithms were simple and easy to program. The last part of the thesis discusses the detection of flexural and diagonal splitting defects and non-linear behaviour of the beams during the vibration tests. Static and dynamic comparisons are also discussed. Based on the characteristics of the polar diagrams it was found that several possible types of non-linear damping were demonstrated in the experiments. The typical viscous and non-linear higher polynomial damping existed mostly in the models although the crack pattern and intensity of cracks contributed to changes in the type of damping. In addition the beam models in almost all conditions showed non-linear soft spring behaviour. Diagonal splitting crack patterns can be idenuried from a small decrease of resonant frequency and from the sharp drop of resonant amplitude. The presence of single deep cracks greatly reduced the stiffness. The experiments show that a sharp decrease of resonant frequency indicates that a large amount of residual strain exists. It is concluded that defects of the reinforced concrete beams can be identified from the changes of the dynamic parameters using the proper digital signal analyses. The jump phenomenon is shown to be due to the effect of the reflected force on the moving exciter mass rather than due to the presence of the non-linear soft spring system.This thesis investigates the dynamic behaviour of reinforced concrete beams as they are loaded to failure. Four beams have been investigated. Two types of crack pattern and two types or reinforcement pattern were the main variable parameters. Partially bonded reinforcement as artificially created (by greasing the bars) and positioned at the center third span in two of the four beams investigated. The remaining two beams had conventional bonded reinforcement. Flexural and diagonal splitting patterns were created by loading mechanisms individually applied on two beams of each type of reinforcement. Stage by stage application of static loadings was used. Steady state vibration tests were applied at prior to loadings the beams and at several load stages as gradually increasing defects occurred. There are four parts to this investigation and these are presented in this thesis. The first part investigates the accuracy of several techniques dealing with signal parameters from a digital response spectrum in the signal processing. A logic geometry was developed and was applied on the line spectra of the response spectrum. Numerical evaluation found that the error induced in the proposed technique decreased exponentially with increasing numbers of cycles. A maximum of 0.17% errors may exist when examining 100 cycles of the frequency of interest. A regression analysis was used to achieve further accuracy of the results. The second part investigates the jump phenomenon of mechanical exciters and the sharp drop phenomenon of magnetic exciters. Both of which may confuse the analysis of structural dynamic behaviour. By accounting for the stiffness of the magnetic field of the magnetic exciter in a mathematical model, the jump phenomena was shown to be due to the effect of the reflected force in the excited structure. Practical equations were also proposed to relate absolute to relative parameters. The third part of the thesis concerns the algorithms required in filter processing and includes the development of a computer solution. Two algorithms were developed to obtain coefficients of a polynomial equation which was set up from elementary equations and from a rational function respectively. The algorithms were simple and easy to program. The last part of the thesis discusses the detection of flexural and diagonal splitting defects and non-linear behaviour of the beams during the vibration tests. Static and dynamic comparisons are also discussed. Based on the characteristics of the polar diagrams it was found that several possible types of non-linear damping were demonstrated in the experiments. The typical viscous and non-linear higher polynomial damping existed mostly in the models although the crack pattern and intensity of cracks contributed to changes in the type of damping. In addition the beam models in almost all conditions showed non-linear soft spring behaviour. Diagonal splitting crack patterns can be idenuried from a small decrease of resonant frequency and from the sharp drop of resonant amplitude. The presence of single deep cracks greatly reduced the stiffness. The experiments show that a sharp decrease of resonant frequency indicates that a large amount of residual strain exists. It is concluded that defects of the reinforced concrete beams can be identified from the changes of the dynamic parameters using the proper digital signal analyses. The jump phenomenon is shown to be due to the effect of the reflected force on the moving exciter mass rather than due to the presence of the non-linear soft spring system

Analisis dinamika struktur dan aplikasi di bidang teknik sipil

vii, 154 halaman: 23 c

Perancangan dan Analisis Struktur Beton Bertulang 1

xxvi, 244 hlm.; 23 c

Detection of Defect in Concrete Structures Using Vibration Technique

This thesis investigates the dynamic behaviour of reinforced concrete beams as are loaded to failure. Four beams have been investigated. Two types of crack pattern and two tyles of reinforcement pattern were the main variable parameters. Partially bonded reinforcement as artificially created (by greasing the bars) and positioned at the center third span in two of the four beams investigated. The remaining two beams had conventional bonded reinforcement. Flexural and diagonal splitting patterns were created by loading mechanisms individually applied on two beams of each type of reinforcement. Stage by stage application of static loadings was used. Steady state vibration tests were applied at prior to loadings the beams and at several load stage as gradually increasing defects occurred. There are four parts to this investigation and these are presented in this thesis. The first part investigates the accuracy of several techniques dealing with the signal parameters from a digital response spectrum in the signal processing. A logic geometry was developed and was applied on the line spectra of the response spectrum. Numerical evaluation found that the error induced in the proposed technique decreased exponentially with increasing numbers of cycles. A maximum of 0.17% errors may exist when examining 100 cycles of the frequency of interest. A regression analysis was used to achieve further accuracy of the results. The second part investigates the jump phenomenon of mechanical exciters and the sharp drop phenomenon of magnetic exciters. Both of which may confuse the analysis of structural dynamic behaviour. By accounting for the stiffness of the magnetic field of the magnetic exciter in a mathematical model, the jump phenomena was shown to be due to the effect of the reflected force in the excited structure. Practical equations were also proposed to relate absolute to relative parameters. The third part of the thesis concerns the algorithms required in filter processing and includes the development of a computer solution. Two algorithms were developed to obtain coefficients of a polynomial equation which was set up from elementary equations and from a rational function respectively. The algorithms were simple and easy to program. The last part of the thesis discusses the detection of flexural and diagonal splitting defects and non-linear behaviour of the beams during the vibration tests. Static and dynamic comparisons are also discussed. Based on the characteristics of the polar diagrams it was found that several possible types of non-linear damping were demonstrated in the experiments. The typical viscous and non-linear higher polynomial damping existed mostly in the models although the crack pattern and intensity of cracks contributed to changes in the type of damping. In addition the beam models in almost all conditions showed non-linear soft spring behaviour. Diagonal splitting crack patterns can be identified from a small decrease of resonant frequency and from the sharp drop of resonant amplitude. The presence of single deep cracks greatly reduced the stiffness. The experiments show that a sharp decrease of resonant frequency indicates that a large amount of residual strain exists. Is is concluded that defects of the reinforced concrete beams can be identified from the changes of the dynamic parameters using the proper digital signal analyses. The jump phenomenon is shown to be due to the effect of the reflected force on the moving exciter mass rather than due to the presence of the non-linear soft spring system

The Maximum Allowable Peak Ground Acceleration of a Six Storey Building Based on Micro Tremor and Numerical Analysis

It is widely known that the natural frequency of building structures can be determined by analyzing Fourier transforms from micro vibrational records. This research was conducted in the structural laboratory of the Department of Civil and Environmental Engineering of UGM, which is a six-storey building. The aim of this study is to verify if maximum ground acceleration of the building in accordance to SNI: 1726-2012 can be approximated by means of analysing amplitudes of microtremor data of the building at resonance. In addition, a numerical calculation is also presented using SAP 2000 for a comparison purpose. The accelerometers were positioned alternately in the direction of N-S and E-W, at the lower end of the columns, close to the center of gravity of the building, on each floor. One of the PCB-Piezotronics accelerometers was placed at the bottom end of the ground floor column while the other one was placed at the bottom end of the consecutively above floor columns. Natural frequencies of the building, resulting from the site measurement, were utilized for validation of the model. The results of this measurement indicate that the first natural frequencies in the direction of N-S and E-W are respectively 2.2473 and 2.1496 Hz. Based on Nakamura theorem (Clear identification of fundamental idea of Nakamura’s technique and its applications, 2000 1), the highest vulnerability index occurs in the N-S direction, on the 4th story but for the E-W direction it does in the 3rd story. The predicted maximum allowable ground accelerations, based on the minimum acceptable acceleration at the drift ratio between floors at 1% of resonance, are 216.576 cm/s2 (gal) and 177.037 cm/s2 (gal) in the N-S and E-W directions respectively. If the lowest value binds, the maximum allowable ground acceleration of the building is 177.037 cm/s2. The bi-axial analysis on column K1 at 4th and 3rd story approves that the column cannot withstand peak ground acceleration at resonance with amplitude of 216.576 cm/s2 (gal). The numerical comparison using SAP 2000 and sinusoidal function at the resonance frequency of 2.1705 Hz in the N-S direction, shows that the maximum allowable acceleration is of 241.33 cm/s2 (gal) which is similar to the experimental results in the same direction. On the other hand, the numerical analysis using a sinusoidal frequency at out of resonance (4 Hz) in the E-W direction predicts allowable ground acceleration of 943.643 cm/s2 (gal). Such a prediction is 533% greater than the results of site measurement. This concludes that if there is no resonance to occur during the earthquake shake, the building can accept significantly higher ground acceleration. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd

An Investigation on Mechanical Properties and Damping Behaviour of Hardened Mortar with Rubber Tire Crumbs (RTC)

Masonry wall has been used for ages as a part of non-engineered building structures, due to its ease of manufacture, strength, and stiffness to support gravity loads, but brittle enough to resist earthquake shake. One solution to increase its ductility when the earthquake shake stroked, ductile materials at bed joints that binding the masonries may apply. Mortar is a composite material consisting of sands, cement, and water that is generally used for masonry construction as a binder at bed joints. On the other hand, rubber has been used to isolate vibration of machinery because of its good damping behaviours. Those materials will be mixed and be elaborated to provide a ductile mortar binder at bed joints. This research aims to investigate the mechanical properties and the damping behaviour of hardened mortar with rubber tire crumbs at proportions of 0%, 40%, and 60%. Three types of specimens in forms of mortar cubes of 50x50x50 mm3, tensile specimens and mortar beams of 100x100x500 mm3 were tested to provide strength and damping behaviour. The addition of rubber tire crumbs in the mortar decreased the compressive strength, tensile strength, flexural strength and unit weight. Despite its weakness in the mechanical strengths, the addition of rubber tire crumbs could increase the damping behaviour significantly. This research recommended that mortar containing RTC is still appropriate use for non-structural component although it has low mechanical properties

The Bond Strength and Damping Properties of Mortar Joint Using Rubber Tire Crumbs

Recently, the utilization of rubber from used car tires known as rubber tire crumbs (RTC) was an interesting discussion in the world. Many researchers have studied the utilization of RTC in Civil Engineering field, which is the RTC as a substitute material for the sand part in concrete or mortar mixtures. The mortar using RTC (RTC-mortar) was also proposed to apply as a mortar joint on masonry walls. The strength of the bond between the mortar and the brick is needed to withstand the in-plane loads, such as shear strength, ductility, and damping capacity. This study investigated the bond strength, shear modulus, stiffness, and damping properties of the RTC-mortar joint due to horizontal cyclic load due to earthquake in-plane load. Mortar specimens consisted of normal mortar (0 RTC) and RTC-mortar with 20, 40 and 60 RTC contents. This study results in the prediction of the optimum content of rubber tire crumbs (RTC) in a mortar mixture to be applied as a mortar joint on a masonry wall, which is 20 of sand volume. Mortar joint using 20 RTC content have the bond strength of 0.361 MPa and a damping ratio of 14.9. Based on previous research, the use of mortar containing 20 RTC as a mortar joint of masonry wall also meets the strength requirements, where the compressive strength of mortar joint must exceed the compressive strength of the brick unit. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd