Sharif Digital Repository

Conventional methods of seismic rehabilitation with concrete shear walls or steel bracing are not considered suitable for some buildings as upgrades with these methods would have required expensive and time consuming foundation work. Supplemental damping in conjunction with appropriate stiffness offered an innovative and attractive solution for the seismic rehabilitation of such structures. This paper deals with the use of friction damper as a passive dissipative device in order to seismic retrofit of existing structures and discusses the design criteria and seismic analysis of a building. The structure is modeled using the finite element program Sap2000 and is analysed using both non-linear... 

This paper presents results of an experimental study to evaluate a new retrofit technique for strengthening shear deficient short concrete beams and columns. In this technique a mortar jacket reinforced with expanded steel meshes is used for retrofitting. Twelve short reinforced concrete specimens, including eight retrofitted ones, were tested. Six specimens were tested under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross section, Ag, and the concrete compressive strength, fc′. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching... 

The sustainable retrofit options may significantly improve the energy consumption and the environmental impacts of the existing buildings. This paper presents a multi objective optimization framework to reach the minimum economic costs and Global Warming Potential (GWP) impact of existing buildings. New energy-efficient technologies for the supply side of the energy system are considered which may minimize life cycle environmental impacts of buildings. Two educational buildings in the campus of Sharif University of Technology are studied. The results show that utilizing reciprocating engine and exhaust-fired absorption chiller reduce the GWP to 133 tons (17.79% of reduction) and 190 tones... 

This paper presents the results of an experimental study on retrofitting RC beams using FRP strengthening and RC jacketing. Three-point loadings are applied to twelve strengthened beams and three reference specimens to put the two techniques into perspective. Formation of first cracks, FRP debonding, and onset of concrete crushing are compared and discussed. Load-deflection behavior, failure modes, and crack propagation patterns are studied extensively. The experiments demonstrate that the RC jacketed beams exhibit a flexural failure identical to the reference beams. However, the FRP strengthened beams fail in a relatively small deflection due to the premature FRP debonding. Furthermore, the... 

In this paper, a novel method of retrofit design in total site cogeneration systems based on constructal theory is presented. In this regard, the total site cogeneration system is decomposed into three constructs: turbines, turbine arrays, and steam generators. The objective function to be minimised is the total annual cost of existing total site. Using constructal theory simplifies the optimisation procedure of total site in addition to reaching better conceptual design especially in more sophisticated systems. A case study from literatures has been taken up to examine the applicability of the algorithm and excellent agreement has been observed. Copyright  

The presented studies have been conducted on the scope and magnitude of damages inflicted by earthquakes over the years. Many RC buildings, designed and constructed in the 1960s and 1970s, have serious structural deficiencies, especially in their beam-column joints. Such deficiencies result from inadequate joint shear strength or confinement of column reinforcement. The joints require elaborate retrofit measures to ensure the performances comparable to those of new designed structures. In this research, a new seismic retrofitting method is presented for beam-column joints based on the two-dimensional enlargement of the joint by using steel plate, angles, and posttensioning rods. The seismic... 

This paper presents results of an experimental study to evaluate a retrofit technique for strengthening shear deficient short concrete columns. In this technique a ferrocement jacket reinforced with expanded steel meshes is used for retrofitting. Six short concrete columns, including four strengthened specimens, were tested. Specimens were under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross, A g, and the concrete compressive strength, fc′. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching their nominal calculated flexural... 

In the present study, numerical simulations are conducted to estimate the in-plane response of adobe walls subjected to pseudo-static cyclic loading based on the finite element code ABAQUS. The simplified micro-modeling approach is adopted and an interface model reported in ABAQUS material library is applied as material model for zero-thickness interface elements. The comparison between obtained results and field test data results in good agreement. Parametric studies are carried out to evaluate the effectiveness of independent parameters changes on response of adobe walls. It is noted that mechanical properties of joints and adobe units play an active role on in-plane behavior of walls. A... 

Building owners’ appropriate risk-mitigation decisions can minimize the social, economic, and socioeconomic consequences of earthquakes. Implementation of appropriate policies can increase the adoption of seismic retrofit measures through the modification of owners’ beliefs. Social interactions among owners can influence their response to the implemented policies. There is a need for appropriate tools that consider the social interactions among the owners and facilitate the evaluation of their response to seismic retrofit promotion policies. The agent-based simulation model in this manuscript addresses this need. The implementation of policies and interactions among agents can influence... 

Building owners’ appropriate risk-mitigation decisions can minimize the social, economic, and socioeconomic consequences of earthquakes. Implementation of appropriate policies can increase the adoption of seismic retrofit measures through the modification of owners’ beliefs. Social interactions among owners can influence their response to the implemented policies. There is a need for appropriate tools that consider the social interactions among the owners and facilitate the evaluation of their response to seismic retrofit promotion policies. The agent-based simulation model in this manuscript addresses this need. The implementation of policies and interactions among agents can influence... 

Interventions such as seismic retrofits and reconstruction of vulnerable buildings can minimize the social and economic consequences of future earthquakes. Various policies can reduce the vulnerability of communities in the face of future earthquakes by enhancing the public risk perception and reducing the costs of interventions for the landlords. There is a need for appropriate tools that can characterize the dynamics of the housing market in response to these policies. The simulation model presented in this manuscript addresses this need. In this model, the decision of the tenants and landlords is characterized by utilizing prospect theory. The impact of candidate policy interventions on... 

In many earthquake prone regions in developing countries, substandard steel moment resisting frame (SMRF) systems pose a profound danger to people and economy in the case of a strong seismic event. Eccentric bracing systems with replaceable vertical links can be utilized as an efficient and practical seismic retrofitting technique to reduce future earthquake damages to such structures. This paper aims, for the first time, to demonstrate the efficiency of eccentric bracing systems with vertical links as a seismic retrofitting technique for the SMRF structures with WCSB and to develop fragility curves for such structures. To achieve this aim, first, the effect of the vertical links on the... 

A new beam-to-column and bracing-to-frame connection that can tolerate high rotational and shear overload is described. The connection is a self-contained separate entity that comprises two parallel attachment plates between which two circular tubes are laid and fixed through welding. The whole combination can also be produced by extrusion, where the plates are laid in an orthogonal relation with the axis of bending. In the welded version, the two plates are laid in a parallel relation with the axis of bending  

A new general semi-rigid beam-to-column connection for skeletal structures, also applicable to offshore platforms, was devised. In a previous paper (OMAE02-28264), the general features of this joint together with some proposed details for its use in fabricating new platforms, as well as retrofitting and repair of existing platforms, were introduced. Moreover, the results of some quasi-static tests on the 'original' version of the connection, in which the energy-dissipating elements (tubes) of the connection are laid in a parallel relation to the axis of bending, were reported. Here, in this paper, the results of recent experimental work on the 'alternate' version of the connection, in which... 

This study presents a framework that utilizes Bayesian regression to create probabilistic cost models for retrofit actions. Performance improvement is the key parameter introduced in the proposed framework. The incorporation of this novel feature facilitates the characterization of retrofit cost as a continuous function of the desired performance improvement. Accounting for the performance gained from retrofit enables the use of the models in determining the optimal level of retrofit. Furthermore, accounting for the model uncertainty facilitates the use of the models in risk and reliability analyses. The proposed framework is applied to create seismic retrofit cost models for masonry school... 

This paper presents the results of an experimental study on the application of pre-stressed high strength metal strips in retrofit of RC columns. Six 2/3 scale were deliberately designated with insufficient transverse reinforcement details and tested under constant axial and cyclic lateral load reversals. The level of axial load and the pattern of strengthening were parameters of this study. It was observed that the technique has been capable to enhance the lateral behavior of columns significantly, in terms of ductility. Very ductile behavior was obtained. The height-wise variations of lateral strain on confining strips are studied. The analysis of the fiber-based model of tested columns... 

This paper presents the results of experimental and analytical study on a new technique of seismic retrofitting of concrete columns. In this technique, standard strapping devices, which are used in the packaging industry, are used to post-tension metal strips around concrete columns. The two ends of the strip are tightened in sealed clamps to maintain the pre-stress force in the strip. Experimental program included axial compressive tests on 30 cylindrical as well as 30 prismatic small-scale columns which were actively confined by pre-stressed metal strips. Longitudinal and lateral strain of concrete and strain in the strips were monitored. Test Results showed significant increase in... 

A friction damper device (FDD) is used for vibration control of an existing steel jacket platform under seismic excitation. First, the damping is presented for vibration mitigation of structures located in seismically active zones. A new method for quick design of friction or yielding damping devices is presented. The effectiveness of the damping system employing such FDDs in a jacket platform is evaluated numerically. The influence of key parameters of the damping system on the vibration suppression of the offshore structure is studied in detail. To examine the vibration control effectiveness of the FDD for the jacket platform, performance of the controlled structure under the seismic...