Volume 2 Issue 3
Authors: Luca Facchini; Michele Rizzo
Abstract: The study of the dynamic behaviour of disordered structures often implies the analysis of the sensitivity of the structural response to the random parameters which characterize its stiffness and damping. This consideration actually involves the solution of many more differential equations than the “ordered” structure (i.e., the structure not affected by randomness of material or geometry). In order to reduce the computational effort, a methodology is proposed, which makes use of the nonlinear normal modes to investigate both the dynamic behaviour of the structure, and its sensitivity to random parameters.
Keywords: Random Dynamics; Disordered Structures; Nonlinear Normal Modes; Nonlinear Structures; Sensitivity Analysis
Authors: Cheng-Chung Chen; Qiang Xue
Abstract: A basic earthquake insurance policy associated with total loss coverage has been implemented in Taiwan to transfer risk caused by devastating earthquake. Acceptance of such an insurance claim depends on two criteria. One is that a building is identified as uninhabitable and required rebuilding. The other is that the repair to replacement cost ratio of a building exceeds 50%. Whether the first criterion is met or not depends on the building damage state which can be determined through a damage rating system based on post-earthquake damage inspection on structural components and system. However, the second criterion has not been implemented for an adjuster to follow without detail financial loss estimation by specialized engineers. Besides, there is no reference to show that these two criteria are consistent. This paper aims to link post-earthquake damage of structural components and direct financial loss for RC residential buildings based on post-earthquake damage evidence. As a result, the second acceptance criterion can be implemented. The statistical analysis shows that the two criteria are consistent in average. A new assessment procedure by incorporating criteria in terms of both damage and direct financial loss has been introduced. With this loss model, half loss coverage or partial loss coverage could be introduced into the basic earthquake insurance in this region.
Keywords: Residential Earthquake Insurance; Earthquake; Total Loss Claims Identification; Reinforced Concrete Structure; Underwriters
Authors: S. K. Mandal; M. M. Singh; N. K. Bhagat
Abstract: Magnitude of particle velocity of each orthogonal component and the component triggering the sensor to monitor depends upon blast geometry and location of measurement with respect to source of vibration. Considering experimental investigations carried out at four different sites, the paper communicates that wide blast geometry (burden and spacing) with respect to depth of blastholes and location of measurement i.e., measurements made at higher altitudes (greater vertical distances) with respect to horizontal distance from vibrating source will result into higher magnitude of vertical or transverse components and will also trigger the sensor to monitor. Similarly, when measurements are made at same altitudes, vertical or transverse component will trigger the sensor to monitor when placed at closer distances and longitudinal component will trigger the sensor when placed at far off distances. The paper lastly communicates that since, each orthogonal vibration component behaves indifferently to cause structural damage, magnitude of each orthogonal component and the component triggering the structure plays an important role to ascertain safety of structure. Longitudinal component in comparison to vertical or transverse component generates more stress on structures and is more susceptible to cause damage to structures.
Keywords: P-wave Velocity; Blast Geometry; Distance of Measurement; Structural Stability
Authors: V. Rajendran; R. Murugesan
Abstract: In recent years, focus has been shifting towards repair and rehabilitation of deficient concrete infrastructures rather than replacement, either in full or replacing the structural members. While carrying out the rehabilitation, one should keep in mind that the methodology should have cost effective strategy and durability. The deterioration caused by the corrosion of reinforcing steel in concrete structures has been recognized as one of the greatest maintenance challenges being faced by many government agencies and other private owners including the engineering contracting companies in the field of construction industry today. Technological advances have created a wide range of new product and systems, which claim to provide long-lasting protection and serviceability for these structures. Usage of different types of surface coating on rebars for the corrosion protection is no longer a proven system on account of many reasons like, reduction in bond stress between the concrete & rebar and so on. Also in the eventuality of rehabilitation of structural elements after a few years, the entire process including chipping the cover concrete, exposing the rebar, cleaning rebars, applying corrosion protection coating to the rebar, providing formwork, pumping of micro concrete, etc., becomes cumbersome and uneconomical in addition to a lot of disturbance to the occupants. However, in order to effectively address the problem it is essential to first understand the cause of the corrosion. The paper describes in detail the philosophy of the corrosion and evaluates the effect of having anodes installed in the concrete members. The paper also describes in detail investigations conducted on a corrosion damaged marine structure at main land and also at an Island, and the repair methodology suggested for the rehabilitation of the structure and executed. The repair methodology proposed included the provision of galvanic anodes. The data presented on the monitoring of the repaired marine structures through half cell potential test conducted over a period of one year from the time of completion of the repair to assess the effectiveness of the sacrificial anodes. The investigations have clearly demonstrated that galvanic anodes have proved to be an effective corrosion control technique for reinforced concrete structures.
Keywords: Corrosion; Galvanic Anodes; Concrete; Half Cell Potential; Rehabilitation; Marine; Methodology; Reinforcement; Cos; Micro Moncrete; Shear Connector
Authors: U?ur Akp?nar; Bar?? Binici
Abstract: Infill walls are generally used as partition walls in structural systems. Their contributions to stiffness and strength during earthquakes are often neglected in the design of new buildings. 1999 Kocaeli, 2003 Bingol and 2011 Van earthquakes in Turkey revealed that the presence of infill walls may significantly affect the vulnerability of structures depending on failure of walls in first stories and formation of soft story mechanism. Since the building stock in Turkey is mostly composed of reinforced concrete frame buildings with masonry infill walls, simulation of building collapse under seismic loads becomes an important issue. In this paper, the failure mechanisms of the infill walls were numerically simulated by integrating an element removal algorithm to the traditional diagonal strut models. The possible unfavourable effects of infill walls on the reinforced concrete structures were investigated under the earthquake loads. For this purpose, a 4-story 3-bay deficient reinforced concrete frame with infill walls was examined and the results were compared with those of the bare frame. 7.4 magnitudes 1999 Duzce earthquake was used as the ground motion record in the nonlinear time history analyses. The analysis results indicated that including infill wall collapse in analyses resulted in large deformation demands, sudden stiffness degradations and formation of a soft story. These detrimental damage events were not observed when the presence of infill walls was neglected.
Keywords: RC Frames; Infill Walls; Nonlinear Analyses; Soft-Story; Element Removing
Authors: M. L. Papadopoulos
Abstract: Field evidence from recent strong earthquakes in the Balkan peninsula has reinforced the belief that the Local Historical Structural System of the region, known as timber-laced masonry construction, shows dependable resistance and significant resilience under earthquake action, rarely reaching the state of catastrophic collapse that typifies other old buildings such as brittle (poorly constructed) reinforced concrete structures. This paper examines the seismic behavior of example traditional houses from the old city of Xanthi, by using simulation models to study the dynamic characteristics of the structures, exploring the possibilities of restoration through pertinent modification of the connecting material properties. The effectiveness of the interventions is gauged through a comparative evaluation of the results obtained from the initial and the post-intervention models, with particular emphasis placed on the global modification of the dynamic characteristics and the anticipated mitigation of localized deformation demands throughout the structures. The variability of the results owing to parameter changes enables a first assessment of the uncertainties associated with the actual details, geometry and state of materials and the mechanical properties thereof, on the dynamic properties and dependable deformation capacity of the structure at the life-safety performance limit state.
Keywords: Timber-Laced Masonry Construction; Local Historical Structural Systems; Non-invasive Interventions; Seismic Behavior; Simulation Models
Authors: S. Ali Ghafari Oskoei; Mahtab Ghafari Osgoie; Ghyslaine McClure
Abstract: Ghafari and McClure (2011, 2012) have developed a new robust linearized seismic analysis method for tall guyed telecommunication masts for design check purposes. This method provides a conservative prediction of the maximum lateral seismic displacements of the mast at the multiple stay levels. Its analytical development duly accounted for the geometric nonlinear response of the guy cables and the cable-mast dynamic interactions. The method was calibrated using detailed nonlinear dynamic analysis of nine real guyed masts subjected to a few earthquake signatures. This paper presents a more extensive evaluation of the proposed method and discusses some trends observed in the results for two selected guyed telecommunication masts under the effects of eighty-one recorded Californian earthquakes. Based on the maximum mast displacements predicted by the linearized method, approximate values are calculated for the maximum cable reactions at their tower attachment point, the maximum cable tensions, and the internal bending moments and horizontal shear forces in the mast. A comparison of the detailed nonlinear dynamic analysis results with those obtained from the linearized simplified method confirms the reliable performance of the simplified method.
Keywords: Seismic Design; Telecommunication Masts; Guyed Towers; Ambient Vibration Measurement; Structural Dynamic
Authors: Mikayel G. Melkumyan
Abstract: Extensive implementation of seismic isolation technologies in Armenia provided a good basis for the development and inclusion of a separate chapter on seismic isolation of buildings in the last edition of the National Seismic Code RABC II-6.02-2006. This chapter is presented in the paper. Since 1994 during a short period of 19 years about 46 buildings and structures have been designed by the author of this paper with application of base or roof isolation systems. Of these designed buildings the total number of already constructed and retrofitted buildings or those currently under construction has reached 37. Information on some of these buildings is given in the paper. Based on the analyses carried out for the considered buildings it is emphasized that seismic isolation significantly reduces the maximum spectral acceleration, also proving to be cost effective and ensuring high reliability of their behaviour under seismic impacts. Seismic isolation techniques developed in Armenia lead to significant savings in construction costs. Several reasons for savings are mentioned in the paper. Comparison of the Code based analyses results with those obtained by the time history analyses indicates that the shear forces at the level of isolation systems, the maximum displacements of the isolators, and the maximum story drifts in the superstructures calculated based on the Armenian Seismic Code provisions are considerably higher than the same values calculated by the time histories. It is concluded that the Code needs a more accurate designation of reduction factors for seismic isolation systems. Corresponding suggestion is made in the paper for the Code revision.
Keywords: Seismic Isolated Buildings; Earthquake Response Analysis; High Reliability; Cost Savings; Time History; Seismic Code; Comparison of Results; Reduction Factors
Authors: Claudio Amadio; Chiara Bedon
Abstract: Monolithic and laminated glass elements, as known, offer interesting opportunities in the realization of innovative architectures of modern buildings. Nevertheless, similar structural elements are typically brittle and slender, thus frequently subjected to buckling phenomena. In these hypotheses, the paper focuses on the load-carrying behavior of 2-layer and 3-layer simply supported laminated glass panels subjected to in-plane shear loads. Analytical formulations based on the concept of equivalent thickness are presented to describe with accuracy their typical behavior. As shown, predicted critical loads and load-transversal displacement relationships are in good agreement with numerical data obtained by using sophisticated 3D-FE models, as well as simplest but accurate geometrical simplified FE models. According to the suggestions that the Eurocodes give the verification of traditional structural elements, a suitable verification criterion appropriately calibrated to numerical and experimental predictions available in literature is suggested to guarantee the requisites of resistance, serviceability and durability typically imposed in the design of conventional structural systems made of steel, concrete or timber. As a result, the proposed approach could be used in daily practice to perform a suitable and rational buckling verification of such brittle load-bearing elements.
Keywords: Equivalent Thickness; Sandwich Theory; In-Plane Shear Loads; 2 Or 3-Layer Laminated Glass Panels; Buckling Verification; Standardized Buckling Curve
Authors: Onur Merter; Taner Ucar
Abstract: Both static and dynamic analysis methods, which may be linear elastic or nonlinear, are used for structural analysis of structures. In nonlinear analysis methods, geometric nonlinearity and behaviour of material beyond linear elastic limit are taken into consideration. Artificial or recorded ground motions are used in nonlinear dynamic analysis, which are also known as nonlinear time history analysis. In this study, both linear and nonlinear dynamic analyses of six and ten-story RC frame structures, which are primarily designed according to Turkish Seismic Design Code, are performed by using seven ground motions recorded at different soil sites of Turkey. However, nonlinear static analyses or so-called pushover analyses of frames are carried out. Base shear forces and interstory drift ratios are obtained as analysis results and the comparison of above mentioned methods are made by using these analysis results.
Keywords: Linear and Nonlinear Analysis Methods; Pushover Analysis; Time History Analysis; Base Shear Forces; Interstory Drift Ratios
Authors: F. Hagechehade; A. Fawaz; E. Farah
Abstract: This paper presents the results of several series of in-situ pressuremeter tests in boreholes with different depths. Laboratory tests were performed on samples taken from these boreholes. Numerical simulations of the pressuremeter tests were carried out using Plaxis software. This numerical analysis permitted the deduction of the shear resistance of soil. A comparison between the numerical results, the experimental ones and the analytical studies has been performed.
Keywords: Pressuremeter; Soil; Numerical Simulation; Shear Resistance; Modulus; Borehole