In this study steel framing systems are investigated with regards to their lateral load carrying capacity and in this context seismic response modification factors of individual systems are analyzed. Numerous load resisting layouts, such as different bracing systems and un-braced moment resisting frames with various bay and story configurations are designed and evaluated in a parametric fashion. Three types of beam to column connection conditions are incorporated in evaluation process. Frames, designed according to Turkish seismic code, are investigated by nonlinear static analysis with the guidance of previous studies and recent provisions of FEMA. Method of analysis, design and evaluation data are presented in detail. Previous studies in literature, history and the theory of response modification phenomenon is presented. Results are summarized, main weaknesses and ambiguities introduced to design by the use of &ldquo / R&rdquo / factors are stated depending on the observed behavior.

In the seismic design of reinforced concrete frames, plastic hinges are allocated to beams such that a ductile beam-sway mechanism will form in preference to other less ductile mechanisms in the event of a major earthquake. This is achieved by ensuring that the flexural strength of columns is greater than that corresponding to the maximum likely flexural strength of beam plastic hinges. Recent experimental studies in New Zealand have shown that elongation of ductile beam plastic hinges, and its interaction with nearby floor slab containing precast-prestressed floor units, increases the strength of beams much more than that specified in New Zealand and American Concrete standards. This level of strength enhancement has raised concern on the adequacy of the current design provisions. To further investigate this problem, a research project was initiated to examine the strength of beam plastic hinges in reinforced concrete frames containing precast-prestressed floor units. In this research, the strength of beam plastic hinges was assessed through experimental and analytical studies. A three-dimensional, one-storey, two-bay reinforced concrete moment resisting frame with prestressed floor units and cast-in-situ concrete topping was tested under quasi-static displacement-controlled cyclic loading. The experimental results provided insight into the mechanics associated with frame-floor interaction. Subsequently, improved design specifications were proposed based on the observed behaviour. To analytically predict the beam-floor interaction, a ductile reinforced concrete plastic hinge multi-spring element was developed and validated with experimental results from cantilever beam and frame sub-assembly tests reported in the literature. The comparisons have demonstrated the ability of the proposed plastic hinge element to predict the flexural, shear, axial, and most importantly, elongation response of ductile plastic hinges. The proposed plastic hinge element was implemented into an analytical model to simulate the behaviour of the frame-floor sub-assembly tested in this research. Specially arranged truss-like elements were used to model the linking slab (the region connecting the main beam to the first prestressed floor unit), where significant inelastic behaviour was expected to occur. The analytical model was found to be capable of predicting the non-linear hysteretic response and the main deformation mechanisms in the frame-floor sub-assembly test. The analytical frame-floor model developed in this study was used to examine the effect of different structural arrangements on the cyclic behaviour of frames containing prestressed floor units. These analyses indicated that slab reinforcement content, the number of bays in a frame and the position of frame in a building (i.e., perimeter or internal frame) can have a significant influence on the strength and elongation response of plastic hinges.

Pushover analysis involves certain approximations and simplifications that some amount of variation is always expected to exist in seismic demand prediction of pushover analysis. In literature, some improved pushover procedures have been proposed to overcome the certain limitations of traditional pushover procedures. The effects and the accuracy of invariant lateral load patterns utilised in pushover analysis to predict the behavior imposed on the structure due to randomly selected individual ground motions causing elastic and various levels of nonlinear response were evaluated in this study. For this purpose, pushover analyses using various invariant lateral load patterns and Modal Pushover Analysis were performed on reinforced concrete and steel moment resisting frames covering a broad range of fundamental periods. Certain response parameters predicted by each pushover procedure were compared with the &#039 / exact&#039 / results obtained from nonlinear dynamic analysis. The primary observations from the study showed that the accuracy of the pushover results depends strongly on the load path, properties of the structure and the characteristics of the ground motion. Pushover analyses were performed by both DRAIN-2DX and SAP2000. Similar pushover results were obtained from the two different softwares employed in the study provided that similar approach is used in modeling the nonlinear properties of members as well as their structural features. The accuracy of approximate procedures utilised to estimate target displacement was also studied on frame structures. The accuracy of the predictions was observed to depend on the approximations involved in the theory of the procedures, structural properties and ground motion characteristics.

Reinforced concrete shear walls as seismic force resisting systems may experience inelastic deformations if subjected to strong seismic excitations. These walls are designed to provide strength, stiffness, energy dissipation capacity and lateral drift control for seismic resistance. Shear wall deformability is largely dependent on adequate confinement of core concrete in boundary elements, prevention of longitudinal bar buckling, as well as proper design and detailing of the web section. Conventional transverse reinforcement placed in shear wall boundary elements consists of hoops, overlapping hoops and crossties, based on the geometry and number of longitudinal bars used. The confinement steel requirement of current building codes (ACI 318 or CSA A23.3) often results in congestion of steel cage due to the high transverse reinforcement ratio required. Placing multiple hoops with 135-degree bends combined with crossties to satisfy the code confinement requirements can create concrete placement and construction problems. In addition, the required time to assemble conventional steel cages with multiple individual ties per spacing can be time consuming, potentially impacting the overall cost and duration of construction. Welded Wire Reinforcement (WWR) is available in the construction industry as concrete reinforcement in the form of welded wire fabric (WWF) manufactured from relatively small diameter wires in comparison to the bar sizes typically used in structural applications. As an alternative to using conventional transverse hoops, prefabricated WWR grids can be used to provide required transverse reinforcement in boundary elements. WWR grids are manufactured using robots to weld cut steel pieces accurately before they are shipped to the job site, resulting in better construction quality and reduced construction time. However, research on the use of WWR is limited in the literature. Further experimental and analytical research is needed to establish design requirements for such reinforcement, especially when used in earthquake resistant construction with requirements for ductile response. The current research project, involved three main phases; i) tests of 3 large-scale reinforced concrete shear walls with WWR grids used as boundary element transverse reinforcement, ii) material tests of grid samples, including those cast in concrete, iii) non-linear finite element analysis. The wall tests were conducted under slowly-applied lateral deformation reversals to investigate their strength and ductility for suitability as seismic resistant structural elements. Material tests were conducted to have a better understanding of WWR behavior, especially their weld capacity. Analytical research was undertaken to expand the experimental findings on shear wall behavior, as well as to conduct parametric investigation to understand the impact of changes in grid strength and ductility. The results indicated that WWR grids can be used as boundary element transverse reinforcement in earthquake resistant shear wall. However, strength and ductility of grids should be established carefully prior to such application. Design strength of WWR grids should be established through burst tests to ensure ductile yielding of wire reinforcement prior to premature weld failure. Those grids that exhibit weld failures may be used with reduced design strength to permit the development of sufficient inelastic deformability in flexure-dominant shear walls.

As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated. The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens, on the other hand, all showed local buckling of FRP tubes. Compared with conventional RC columns, CFFT column possesses higher flexural strength and energy dissipation with an extended plastic hinge region. Among all CFFT columns, the hybrid lay-up demonstrated the highest flexural strength and initial stiffness, mainly because of its high reinforcement index and FRP/concrete stiffness ratio, respectively. Moreover, at the same drift ratio, the hybrid lay-up was also considered as the best in term of energy dissipation. Specimens with glassfiber tubes, on the other hand, exhibited the highest ductility due to better flexibility of glass FRP composites. Furthermore, ductility of CFFTs showed a strong correlation with the rupture strain of FRP. Parametric study further showed that different FRP architecture and rebar types may lead to different failure modes for CFFT columns. Transient analysis of strong ground motions showed that the column with off-axis nonlinear filament-wound glass FRP tube exhibited a superior seismic performance to all other CFFTs. Moreover, higher FRP reinforcement ratios may lead to a brittle system failure, while a well-engineered FRP reinforcement configuration may significantly enhance the seismic performance of CFFT columns.

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In the last two decades, two major earthquakes have occurred in Japan: the 1995 Kobe earthquake and the 2011 Great East Japan earthquake. In the 2011 Great East Japan earthquake, many bridge structures were destroyed by the tsunamis, but it is interesting to study the ground motion induced damage and also how this earthquake differed from the one in 1995. In this thesis, the seismic response of a bridge designed according to the current Japanese Design Specifications was evaluated when it is subjected to near-field ground motions recorded during the 1995 Kobe earthquake and far-field ground motions recorded during the 2011 Great East Japan earthquake. For this purpose, a series of nonlinear dynamic response analysis was conducted and the seismic performance of the bridge was verified in terms of its displacement and ductility demand. It was found from the dynamic response analysis that the seismic response of the target bridge when subjected to the ground motions from the 2011 Great East Japan earthquake was smaller than during the 1995 Kobe earthquake. Although the ground motions from the 2011 Great East Japan earthquake were very strong, they were not as strong as the ground motions from the 1995 Kobe earthquake. The results obtained in this thesis clarify the validity of the Type I and Type II design ground motions. The target bridge used in this thesis was designed according to the post-1990 design specifications and showed limited nonlinear response when subjected to the different ground motions which shows how efficient the enhancement of the seismic performance of bridges has been since the 1990’s.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22757号 / 工博第4756号 / 新制||工||1744(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 五十嵐 晃, 教授 高橋 良和, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

When a structure undergoes seismic excitation, the intensities and spatial distributions of the reactive weights on the structure may not be the same as those assumed in original design. Such a difference is inevitable due to many facts with the random nature (e.g., redistribution of live load), resulting in accidental eccentricity and consequently torsional response in the system. The added torsion can cause excessive deformation and premature failure of the lateral force resisting system and its detrimental effect is typically accounted for in most building design codes with an arbitrarily specified accidental eccentricity value. While it tends to amplify drift response of buildings under earthquake excitations, it is unclear whether the code specified accidental eccentricity is quantitatively adequate or not in seismic fragility assessment of steel moment frames (including low-rise, mid-rise and high-rise frames) with random reactive weight distributions. This thesis applies surveyed dead and live load intensities and distributions to three representative steel moment resisting frame structures that have been widely investigated in a series of projects under the collaboration of the Structural Engineers Association of California (SEAOC), the Applied Technology Council (ATC), and Consortium of Universities for Research in Earthquake Engineering (CUREE), known as SAC. Based on an extensive parametric study and incremental nonlinear dynamic analyses, it is found that variable load intensity and eccentricity had negligible impacts on the inter-story drifts of the low- and high-rise steel moment frames. However, they affect to a higher degree the performance of the mid-rise steel moment frames. Moreover, it is found that under the maximum considered earthquake (MCE) event, the actual drifts in steel moment frames with random reactive weight distributions can be conservatively captured through consideration of the code specified accidental eccentricities.