Many intra-tectonic plate regions are considered to have low to moderate seismic risk. However, devastating earthquakes can occur in these regions and result in high consequences in terms of casualties and damage. Non-ductile detailing practice employed in these structures make them prone to potential damage and failure during an earthquake. Furthermore, the use of infill walls is a divisive issue as on positive side dual wall-frame systems have beneficial effects related to strength, stiffness, and ductility. However, if not designed properly infill wall can also lead to undesirable structural failures of complete wall frame system. Although, there has been significant amount of international research in this area, it is worth noting that very little research exists for Australian frames. This thesis presents the experimental and analytical research conducted at The University of Adelaide to gain some insight into the behaviour of typically detailed Australian reinforced concrete frames subjected to ground motions. The main objectives of this research were (1) to investigate the behaviour of non-seismically designed reinforced concrete frames under a 500-YRP earthquake; (2) to determine the different magnitudes of earthquake (YRP) that are likely to cause excessive drifts in or collapse of gravity-load-designed reinforced concrete frames and (3) to investigate the effect of infill walls on the moment-resisting frames subjected to seismic loads. The experimental program consisted of earthquake simulation tests on a 1/5 scale model of a 3-storey reinforced concrete frame and four ½-scale reinforced concrete brick infilled frame specimens subjected to quasi-static cyclic loading. The analytical study included static pushover and non-linear dynamic analyses of the 3-, 5- and 12-storey reinforced concrete frames. From the overall performance of gravity-load-designed bare reinforced concrete frames considered in this study, it was concluded that the non-seismically designed frames appear to be capable of resisting a “design magnitude earthquake” (i.e., 500- YRP) in low earthquake hazard regions. However, their behaviour under more severe earthquakes (e.g. a 2500-YRP earthquake) is questionable. Perhaps the earthquake design requirements should consider as an alternative the ‘collapse prevention’ limit state for longer return period earthquakes, of the order of 2000–2500-YRP. The experimental research on reinforced concrete infilled frame indicated that the infill wall does not adversely effect the in plane ultimate strength, stiffness, and ductility of the bare reinforced concrete frame. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1372229 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Civil, Environmental and Mining Engineering, 2009

Tunnels, culverts, and subway stations are the main parts of an integrated infrastructure system. Most of them are constructed by the cut-and-cover method at shallow depths (mainly lower than 30 m) of soil deposits, where large-scale seismic ground deformation can occur with lower stiffness and strength of the soil. Therefore, the transverse racking deformation (one of the major seismic ground deformation) due to soil shear deformations should be included in the seismic design of underground structures using cost- and time-efficient methods that can achieve robustness of design and are easily understood by engineers. This paper aims to develop a simplified but comprehensive approach relating to vulnerability assessment in the form of fragility curves on a shallow two-story reinforced concrete underground box structure constructed in a highly-weathered soil. In addition, a comparison of the results of earthquakes per peak ground acceleration (PGA) is conducted to determine the effective and appropriate number for cost- and time-benefit analysis. The ground response acceleration method for buried structures (GRAMBS) is used to analyze the behavior of the structure subjected to transverse seismic loading under quasi-static conditions. Furthermore, the damage states that indicate the exceedance level of the structural strength capacity are described by the results of nonlinear static analyses (or so-called pushover analyses). The Latin hypercube sampling technique is employed to consider the uncertainties associated with the material properties and concrete cover owing to the variation in construction conditions. Finally, a large number of artificial ground shakings satisfying the design spectrum are generated in order to develop the seismic fragility curves based on the defined damage states. It is worth noting that the number of ground motions per PGA, which is equal to or larger than 20, is a reasonable value to perform a structural analysis that produces satisfactory fragility curves.

The capacity spectrum method is a very popular tool in the performance based earthquake resistant design of structures. Though it involves nonlinear static analysis, it can be used to predict the dynamic behaviour of the building under earthquake load. Since the analysis is only static and not dynamic, it is very well suited for the design offices and low end computer terminals as opposed to dynamic analysis which is very resource consuming. There are several methods/variations of methods, to perform the nonlinear static analysis, popularly known as pushover analysis and convert it to capacity spectrum. Displacement based pushover analysis, force based pushover analysis, modal pushover analysis, energy based pushover analysis etc. are some of the variations of pushover analysis. There are a few attempts to consider the change in mode shape but all the methods are silent about the change in frequency due to formation of hinges in the structure. The available codes for building design such as ATC-40 provide some guidelines for getting the capacity spectrum but are not yet developed for proper ductility consideration while converting the pushover curve to capacity spectrum. The present study tries to address the above issues while proposing a new energy based approach to draw capacity spectrum. The chapter 1 introduces the concept of pushover analysis and capacity spectrum concepts. Different approaches to get these curves, their theoretical background, variations and limitations are discussed as a quick review. Chapter 2 is about the review of literature present on these topics. It is found that most of the studies have been carried out in the past on the framed buildings regarding the pushover analysis. In the last few years attempts are also made to consider the effect of torsion. Summarising the various contributions till now, it may be concluded that even in the earlier multimode pushover analysis the effect of different modes on the only static force distribution was considered. Further the spectral acceleration is obtained as a ratio of base shear and α times the weight of the building, where α is the modal mass coefficient. Only the first mode frequency could be utilized to convert the maximum displacement at the top to the spectral acceleration and the corresponding maximum potential energy (P.E.) could be used for equivalence of MDOF and SDOF. Therefore in chapter 3 which follows, the above limitation is removed as explained below. In chapter 3, the new methodology based on energy equivalence consideration is proposed step by step. For the given multistorey building, a displacement profile is applied to the building which is proportional to the effective mode shape. The effective mode shape can be the first mode shape or a combination of first few mode shapes. In the present study, two cases are considered. In the first case, the effective mode shape is considered to be the first mode shape itself whereas in the second case the effective mode shape is considered to be a linear combination of first three modes weighted by corresponding participation factors. After this, a nonlinear static analysis is performed on the structure considering the above displacement profile. Due to the above provided displacement profile, there will be yielding in the structure at a few locations. The yielded structure is again analysed for eigenvalues and mode shapes and the first three mode shapes are extracted along with their participation factors. Again the deflected structure is subjected to the deflection proportional to the effective mode shape and the analysis is continued until the collapse. The chapter also describes the details of the model used for simulation. Two kinds of simulation are performed on the model. One is considering only single mode of vibration whereas the other is considering the multiple modes (3 in this case) of vibration of the structure. Chapter 4 discusses the results of the simulations performed on the model. Single mode and multimode cases are treated and discussed separately. The proposed method is in its nascent stage and hence a lot of modification and validation work is needed to consider the method acceptable. The chapter 5 concludes the overall outcome of the present study and provides scope for the further study.

No description available.

In practice, steel frames are analyzed and designed by assuming all beam to column connections as either rigid or simple. In real life, there are no such idealizations as rigid or simple and all connections would actually belong to a group of connections named as semi rigid connections. Various difficulties exist in modeling an accurate non-linear behavior of a steel structure, where one of these challenges is the modeling of semi-rigid behavior of connections. A detailed finite element model would take into account the complex interaction between all surfaces due to contact, friction and bolt pretension besides the material and geometrical nonlinearity effects. All these nonlinearity effects could be simply lumped as a moment-rotation type model at the connection region. Such a methodology is followed in this thesis and the main aim is to study the lumped nonlinear behavior of steel semi-rigid connections on the overall structural responses of steel Special Moment Frames. In this thesis three, nine and fifteen story steel Special Moment Frames are analyzed and designed as rigid frames first, and then the frames are reanalyzed considering non-linear effects due to semi-rigid connections. Changes in the ductility and overstrength reduction factors obtained from pushover curves are compared between the rigid and semi rigid modeling alternatives.

Cold-Formed Steel (CFS) is a material used in the fabrication of structural and non-structural elements for the construction of commercial and residential buildings. CFS exhibits several advantages over other construction materials such as wood, concrete and hot-rolled steel (structural steel). The outstanding advantages of CFS are its lower overall cost and non-combustibility. The steel industry has promoted CFS in recent decades, causing a notable increase in the usage of CFS in building construction. Yet, structural steel elements are still more highly preferred, due to the complex analysis and design procedures associated with CFS members. In addition, the seismic performance of CFS buildings and their elements is not well known. The primary objective of this study is to develop a method for the seismic assessment of the lateral-load resistant shear wall panel elements of CFS buildings. The Performance-Based Design (PBD) philosophy is adopted as the basis for conducting the seismic assessment of low- and mid-rise CFS buildings, having from one to seven storeys. Seismic standards have been developed to guide the design of buildings such that they do not collapse when subjected to specified design earthquakes. PBD provides the designer with options to choose the performance objectives to be satisfied by a building to achieve a satisfactory design. A performance objective involves the combination of an earthquake (i.e., seismic hazard) and a performance level (i.e., limit state) expected for the structure. The building capacity related to each performance level is compared with the demand imposed by the earthquake. If the earthquake demand is less than the building capacity, the structure is appropriately designed. The seismic performance of a CFS building is obtained using pushover analysis, a nonlinear method of seismic analysis. This study proposes a Simplified Finite Element Analysis (SFEA) method to carry out the nonlinear structural analysis. In this study, lateral drifts associated with four performance levels are employed as acceptance criteria for the PBD assessment of CFS buildings. The lateral drifts are determined from experimental data. In CFS buildings, one of the primary load-resistant elements is Shear Wall Panel (SWP). The SWP is constructed with vertically spaced and aligned C-shape CFS studs. The ends of the studs are screwed to the top and bottom tracks, and structural sheathing is installed on one or both sides of the wall. For the analysis of CFS buildings, Conventional Finite Element Analysis (CFEA) is typically adopted. However, CFEA is time consuming because of the large number of shell and frame elements required to model the SWP sheathing and studs. The SFEA proposed in this study consists of modeling each SWP in the building with an equivalent shell element of the same dimensions; that is, a complete SWP is modeled by a 16-node shell element. Thus, significantly fewer elements are required to model a building for SFEA compared to that required for CFEA, saving both time and resources. A model for the stiffness degradation of a SWP is developed as a function of the lateral strength of the SWP. The model characterizes the nonlinear behaviour of SWP under lateral loading, such that a realistic response of the building is achieved by the pushover analysis. The lateral strength of a SWP must be known before its seismic performance can be assessed. In current practice, the lateral strength of a SWP is primarily determined by experimental tests due to the lack of applicable analytical methods. In this investigation, an analytical method is developed for determining the ultimate lateral strength of SWP, and associated lateral displacement. The method takes into account the various factors that affect the behaviour and the strength of SWP, such as material properties, geometrical dimensions, and construction details. To illustrate the effectiveness and practical application of the proposed methodology for carrying out the PBD assessment of CFS buildings, several examples are presented. The responses predicted by the SFEA are compared with responses determined experimentally for isolated SWP. In addition, two building models are analyzed by SFEA, and the results are compared with those found by SAP2000 (2006). Lastly, the PBD assessment of two buildings is conducted using SFEA and pushover analysis accounting for the nonlinear behaviour of the SWP, to demonstrate the practicality of the proposed technology.

Cold-Formed Steel (CFS) is a material used in the fabrication of structural and non-structural elements for the construction of commercial and residential buildings. CFS exhibits several advantages over other construction materials such as wood, concrete and hot-rolled steel (structural steel). The outstanding advantages of CFS are its lower overall cost and non-combustibility. The steel industry has promoted CFS in recent decades, causing a notable increase in the usage of CFS in building construction. Yet, structural steel elements are still more highly preferred, due to the complex analysis and design procedures associated with CFS members. In addition, the seismic performance of CFS buildings and their elements is not well known. The primary objective of this study is to develop a method for the seismic assessment of the lateral-load resistant shear wall panel elements of CFS buildings. The Performance-Based Design (PBD) philosophy is adopted as the basis for conducting the seismic assessment of low- and mid-rise CFS buildings, having from one to seven storeys. Seismic standards have been developed to guide the design of buildings such that they do not collapse when subjected to specified design earthquakes. PBD provides the designer with options to choose the performance objectives to be satisfied by a building to achieve a satisfactory design. A performance objective involves the combination of an earthquake (i.e., seismic hazard) and a performance level (i.e., limit state) expected for the structure. The building capacity related to each performance level is compared with the demand imposed by the earthquake. If the earthquake demand is less than the building capacity, the structure is appropriately designed. The seismic performance of a CFS building is obtained using pushover analysis, a nonlinear method of seismic analysis. This study proposes a Simplified Finite Element Analysis (SFEA) method to carry out the nonlinear structural analysis. In this study, lateral drifts associated with four performance levels are employed as acceptance criteria for the PBD assessment of CFS buildings. The lateral drifts are determined from experimental data. In CFS buildings, one of the primary load-resistant elements is Shear Wall Panel (SWP). The SWP is constructed with vertically spaced and aligned C-shape CFS studs. The ends of the studs are screwed to the top and bottom tracks, and structural sheathing is installed on one or both sides of the wall. For the analysis of CFS buildings, Conventional Finite Element Analysis (CFEA) is typically adopted. However, CFEA is time consuming because of the large number of shell and frame elements required to model the SWP sheathing and studs. The SFEA proposed in this study consists of modeling each SWP in the building with an equivalent shell element of the same dimensions; that is, a complete SWP is modeled by a 16-node shell element. Thus, significantly fewer elements are required to model a building for SFEA compared to that required for CFEA, saving both time and resources. A model for the stiffness degradation of a SWP is developed as a function of the lateral strength of the SWP. The model characterizes the nonlinear behaviour of SWP under lateral loading, such that a realistic response of the building is achieved by the pushover analysis. The lateral strength of a SWP must be known before its seismic performance can be assessed. In current practice, the lateral strength of a SWP is primarily determined by experimental tests due to the lack of applicable analytical methods. In this investigation, an analytical method is developed for determining the ultimate lateral strength of SWP, and associated lateral displacement. The method takes into account the various factors that affect the behaviour and the strength of SWP, such as material properties, geometrical dimensions, and construction details. To illustrate the effectiveness and practical application of the proposed methodology for carrying out the PBD assessment of CFS buildings, several examples are presented. The responses predicted by the SFEA are compared with responses determined experimentally for isolated SWP. In addition, two building models are analyzed by SFEA, and the results are compared with those found by SAP2000 (2006). Lastly, the PBD assessment of two buildings is conducted using SFEA and pushover analysis accounting for the nonlinear behaviour of the SWP, to demonstrate the practicality of the proposed technology.

Interstory drift ratio is an important parameter for the determination of the structural performance under strong ground motions. A probabilistic procedure is proposed in this study to estimate the inelastic maximum interstory drift ratio. The procedure considers the uncertainties associated with the strong ground motions and structural behavior. Elastic and inelastic response history analyses of reinforced-concrete, moment-resisting frames are used together with a near-fault strong ground motion data set to derive the probabilistic procedure. The elastic and inelastic response history analysis results are evaluated in a statistical manner to present the probabilistic approach proposed here. The method presented basically makes use of the fundamental mode properties of the frame systems and modifies the elastic maximum interstory drift ratio by a modifying factor that is determined from the idealized lateral strength capacity (pushover analysis) of the structure. As a part of this thesis, the performance of recently improved nonlinear static procedures that are used in estimating the deformation demands on structural systems are also evaluated using the single- and multi-degree-of-freedom response history analyses results obtained during the conduct of the study.

The analysis procedures employed in earthquake engineering can be classified as linear static, linear dynamic, nonlinear static and nonlinear dynamic. Linear procedures are usually referred to as force controlled and require less analysis time and less computational effort. On the other hand, nonlinear procedures are referred to as deformation controlled and they are more reliable in characterizing the seismic performance of buildings. However, there is still a great deal of unknowns for nonlinear procedures, especially in modelling the reinforced concrete structures. Turkey ranks high among all countries that have suffered losses of life and property due to earthquakes over many centuries. These casualties indicate that, most regions of the country are under seismic risk of strong ground motion. In addition to this phenomenon, recent studies have demonstrated that near fault ground motions are more destructive than far-fault ones on structures and these effects can not be captured effectively by recent nonlinear static procedures. The main objective of this study is developing a simple nonlinear dynamic analysis procedure which is named as &ldquo / Dynamic Pull Analysis&rdquo / for estimating the seismic response of multi degree of freedom (MDOF) systems. The method is tested on a six-story reinforced concrete frame and a twelve-story reinforced concrete frame that are designed according to the regulations of TS-500 (2000) and TEC (1997).

Lateral load carrying capacities of reinforced concrete structures which are designed by considering only gravity loads or according to outdated earthquake codes can be insufficient. The most important problem for these buildings is the limited ductility of the frame elements. How to evaluate the performance of an existing structure and to what level to strengthen it had been major concerns for structural engineers. Recent earthquakes which occurred in the Marmara Region in the last decade have increased the number of seismic assessment projects drastically. However, there was no special guideline or code dealing with the assessment of existing buildings. In order to have uniformity in assessment projects, a new chapter has been included in the revised Turkish Earthquake Code (2006). In this study, the existing and retrofitted conditions of a reinforced concrete building were assessed comparatively by employing linear and nonlinear assessment procedures according to different seismic rehabilitation codes. The study was carried out on a six storey reinforced concrete telephone exchange building. Although there was no damage in the structure due to the recent earthquakes that occurred in the Marmara Region, the building was assessed and retrofitted in 2001 by using equivalent lateral load analysis results. The results of linear and nonlinear assessment procedures performed in the scope of this thesis, were also compared with the assessment results of this previous study. In the nonlinear assessment procedures, pushover analysis results were used. In addition to comparison of the assessment procedures, efficiency of a widely used approximate pushover method was also investigated.