Stochastic vulnerability assessment of masonry structures: Concepts, modeling and restoration aspects

A methodology aiming to predict the vulnerability of masonry structures under seismic action is presented herein. Masonry structures, among which many are cultural heritage assets, present high vulnerability under earthquake. Reliable simulations of their response to seismic stresses are exceedingly difficult because of the complexity of the structural system and the anisotropic and brittle behavior of the masonry materials. Furthermore, the majority of the parameters involved in the problem such as the masonry material mechanical characteristics and earthquake loading characteristics have a stochastic-probabilistic nature. Within this framework, a detailed analytical methodological approach for assessing the seismic vulnerability of masonry historical and monumental structures is presented, taking into account the probabilistic nature of the input parameters by means of analytically determining fragility curves. The emerged methodology is presented in detail through application on theoretical and built cultural heritage real masonry structures

Overstrength of Displacement-Based Designed Eccentrically Braced Steel Frames

Direct Displacement-Based Design (DDBD) is a performance-based seismic design method that has been proposed and developed over the past two decades for RC frame structures, shear walls and bridges design. The aim of this study is to evaluate overstrength of EBFs with short, intermediate and long link beams designed according to the DDBD method. For this purpose, twelve EBFs with 3, 5, 9 and 12 stories having short, intermediate and long link beams designed using the DDBD method. To investigate the seismic behavior of the considered EBFs, it is first necessary to model properly the nonlinear cyclic behavior of link beams properly. In this regard, the macro-model developed and proposed by Richards was utilized in this study to simulate the nonlinear behavior of some tested link beams available in the literature. After validating the finite-element model, the seismic behavior of the considered EBFs was studied using nonlinear static analyses. The results show that the overstrength factors of the DDB designed EBFs are variable depending on their links length ratio and may even be less than the factor proposed in the DDBD method (i.e. 1.5). This factor was evaluated as 1.51, 1.37 and 1.19 for the investigated EBFs in this study with short, intermediate and long link beams, respectively

6) The Relation of Business Strategy with Earnings Quality and Stock Return in Firms listed in TSE

This study is aimed to examine the relation of business strategy with earnings quality and stock return in firms listed in Tehran Stock Exchange during the period from 2005 to 2012. The sample includes 99 firms and  the study is a descriptive correlation one.  To test the hypothesis, the panel data model and ordinary least squares (OLS) method are applied. In this study, from the business strategy point of view, firms are classified into two groups of prospective and defensive ones. To determine a firm's strategy, Ittner et al (1997) composite scoring system has been used. Also, to measure earnings quality variable, two indices of accounting conservatism and earnings management are employed. To measure accounting conservatism, the Givoly and Hayn (2000) conservatism index and to measure earnings management, the scale of the total discretionary accruals (according to adjusted Jones model) have been used. The results indicate that the level of earnings management in defensive corporations is higher than offensive (pioneer) corporations. Also, the results imply that the economic environment affects the relation between business strategies and earnings quality of a firm. Moreover, the results show no significant relation of firms' strategy with their level of conservatism and stock returns. Furthermore, it was found that the economic environment has no influence on the relation between business strategies and stock return of firms

An investigation on the effect of gusset plate connection rigidity on the seismic behavior of special concentrically braced frames

Special concentrically braced frames (SCBFs) are commonly used to resist lateral loads in buildings. The bracing system sustains large deformations due to inelastic behavior in bracing members (buckling and yielding in tension). Generally, in the conventional modeling strategy, the effect of gusset plates in providing beam-column connections rigidity and hence, improving the post-buckling performance of these frames is not taken into account. This paper deals with the effect of gusset plate rigidity on the seismic behavior of SCBFs using Roeder’s proposed model in the literature. In this paper, four 3, 6, 9 and 12-story SCBFs were designed and modeled using two distinct methods: conventional method with hinged connections and Roeder’s method with semi-rigid connections. Then, the models behavior was investigated with both pushover analysis and nonlinear time-history analysis using OpenSees software. The results showed that lateral load capacity of the frames modeled with the Roeder’s proposed model are about 10% larger than the conventional method’s capacity. Also, it was found that the semi-rigid model leads to a less drift ratios and more overstrength factors

Direct displacement-based design of special composite RC shear walls with steel boundary elements

Special composite RC shear wall (CRCSW) with steel boundary elements is a kind of lateral force resisting structural system which is used in earthquake-prone regions. Due to their high ductility and energy dissipation, CRCSWs have been widely used in recent years by structural engineers. However, there are few studies in the literature on the seismic design of such walls. Although there are many studies in the literature on the Direct Displacement-Based Design (DDBD) of RC structures, however, no study can be found on DDBD of CRCSWs. Therefore, the aim of present study is to evaluate the ability of DDBD method for designing CRCSWs. In this study, four special composite reinforced concrete shear walls with steel boundary elements of 4, 8, 12 and 16 story numbers were designed using the DDBD method for target drift of 2%. The seismic behavior of the four CRCSWs was studied using nonlinear time-history dynamic analyses. Dynamic analyses were performed for the mentioned walls using 7 selected earthquake records. The seismic design parameters considered in this study includes: lateral displacement profile, inelastic dynamic inter-story drift demand, failure pattern and the composite RC shear walls overstrength factor. For each shear wall, the overall overstrength factor was calculated by dividing the ultimate dynamic base shear demand (Vu) by the base shear demand (Vd) as per the Direct Displacement Based-Design (DDBD) method. The results show that the DDBD method can be used to design CRCSWs safely in seismic regions with predicted behavior

Seismic Behavior of the Cube of Zoroaster Tower Using the Discrete Element Method

There are several ancient stone masonry structures of great archeological significance in earthquake-prone areas around the world. Kaʻba-ye Zartošt (Cube of Zoroaster) is a 14.0 m square in shape tower, which was built using white limestone blocks and dry joints. The tower dates back to the Achaemenid empire era and is located in the earthquake-prone area of Nagsh-e Rustam in Fars, Iran. Although, after approximately 2,500 years the tower is still standing, it is now in a severely deteriorated condition and may be vulnerable against future large in magnitude earthquakes. This paper presents the application of a previously developed three-dimensional numerical model based on the discrete element method of analysis to investigate the seismic behavior of the Cube of Zoroaster tower. The tower was represented by a series of distinct blocks separated by zero-thickness interfaces. The developed model allows finite displacements and rotations of distinct blocks while new contacts between the blocks are automatically recognized and updated as the calculation progresses. A series of non-linear dynamic analysis have been performed. To this end, the behavior of the tower to different ground shaking motions is discussed and the possible failure modes for each case are explored