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Web-based collaborative systems support a variety of complex scenarios. Not only the interaction among one user and a computer has to be modeled but also the interaction among the collaborating users as well. As a result, the user interfaces of many web-based collaborative systems are quite complex, but hardly use approved user interface concepts for the design of interactive systems. Thereby, web-based collaborative systems aggravate the interaction of the users with the system and also with each other. In this article, we describe how the adaptability and usability of such systems can particularly be improved by supporting direct manipulation techniques for navigation as well as tailoring. The new functionality for tailoring and navigation is complemented by new forms of visualizing synchronous awareness information and supporting communication in web-based systems. We show this exemplarily by retrofitting the web-based collaborative system CURE while highlighting the concepts that can be easily transferred to other web-based collaborative systems.

In this research, a seismic retrofitting method for chevron-braced frames (CBFs) is proposed. The key idea here is to prevent the buckling of the chevron braces via a conventional construction technique that involves a hysteretic energy-dissipating element installed between the braces and the connected beam. The energy-dissipating element is designed to yield prior to buckling of the braces, thereby preventing the lateral stiffness and strength degradation of the CBF caused by buckling, while effectively dissipating the earthquake input energy. Nonlinear static pushover, time history and damage analyses of the CBF and retrofitted CBF (RCBF) are conducted to assess the performance of the RCBF compared with that of the CBF. The results of the analyses reveal that the proposed retrofitting method can efficiently alleviate the detrimental effects of earthquakes on the CBF. The RCBF has a more stable lateral force–deformation behavior with enhanced energy dissipation capability than the CBF. For small-to-moderate intensity ground motions, the maximum interstory drift of the RCBF is close to that of the CBF. But, for high intensity ground motions, it is considerably smaller than that of the CBF. Compared with the CBF under medium-to-large intensity ground motions, the RCBF experiences significantly less damage due to prevention of buckling of the braces.

Realizing the importance of widely used technique of plating for flexural retrofitting of reinforced concrete (RC) beams and its drawbacks due to premature failure(s), present work concentrates in developing a finite element tool model capable of successfully capturing multiple premature failure modes and their corresponding behaviors. The model is simple but focused; the capability and accuracy of the results have been validated through test literature, particularly focusing on the load capacities of beams at progressive stages of failure modes; which is from crack initiation through to complete failure, such as the load of crack initiation, first crack and complete failure. Acceptable accuracy is shown in terms of crack type(s), crack patterns, sequence, location and direction of propagation through the innovative use of cohesive zone model (CZM). The model clearly explains that debonding and peeling, although originating from a same location for most cases, are extensions of different types of cracks.

An extensive program of shaking table tests on 1/4-scale three-dimensional R/C frames was jointly carried out by the Department of Structure, Soil Mechanics and Engineering Geology (DiSGG) of the University of Basilicata, Italy, and the National Laboratory of Civil Engineering (LNEC), Portugal. It was aimed at evaluating the effectiveness of passive control bracing systems for the seismic retrofit of R/C frames designed for gravity loads only. Two different types of braces were considered, one based on the hysteretic behaviour of steel elements, the other on the superelastic properties of Shape Memory Alloys (SMA). Different protection strategies were pursued, in order to fully exploit the high energy dissipation capacity of steel-based devices, on one hand, and the supplemental re-centring capacity of SMA-based devices, on the other hand. The experimental results confirmed the great potentials of both strategies and of the associated devices in limiting structural damage. The retrofitted model was subjected to table accelerations as high as three times the acceleration leading the unprotected model to collapse, with no significant damage to structural elements. Moreover, the re-centring capability of the SMA-based bracing system was able to recover the undeformed shape of the frame, when it was in a near-collapse condition. In this paper the experimental behaviour of the non protected and of the protected structural models are described and compared.

An experimental study on half-scale brick-masonry models with different strengthening and retrofitting measures has been studied under cyclic loading in a quasi-static test facility. The strengthening measures undertaken for the studies are the horizontal bond beam at the lintel and sill level with a combination of vertical reinforcement at corners and openings. The retrofitting measures studied are grouting with epoxy-sand-mortar and cement-grout-injection with welded wire mesh in the cracked region. The tests reveal that the horizontal bond beam at lintel level with vertical reinforcement is effective in reducing the cracking above the lintel level. The insertion of an additional sill-band significantly reduces the cracking in walls. The epoxy-sand-mortar techniques for retrofitting of cracked regions prove to be effective enough to restore the initial strength, stiffness and deformation capacity. Although specimen retrofitted with cement-grout-injection with welded wire mesh is effective to regain the ultimate strength yet the brittle failure is observed as the specimen is stressed beyond the elastic limit.

In the context of capacity design philosophy, where a desired failure mode exhibiting adequate levels of energy absorption capacity is envisaged, control must be exercised on the member behaviour to safeguard the achievement of the target overall response. Therefore, local repair and retrofitting methods that result in unquantifiable effects on seismic response characteristics should be re-assessed. In contrast, techniques to affect, in a controlled and easy-to-monitor fashion, individual design response parameters, i.e. stiffness, strength and ductility, may provide a new framework for repair and retrofitting earthquake-damaged structures to mirror 'capacity design' principles used for new structures. Such an approach is discussed in this paper and possible scenarios where selective intervention may be required are identified. A number of tests on RC walls are also reviewed to confirm the feasibility of the proposed intervention techniques. Finally, extensive parametric studies are carried out, using verified analytical models, leading to the derivation of selective re-design expressions and guidelines.

Uttarakhand in the foothills of Himalayas is considered to be one of the most tectonically active regions of northern India as it had experienced several destructive earthquakes such as Pithoragarh (1980), Uttarkashi (1991), Chamoli (1999) and Gopeshwar (2005). The state of Uttar Pradesh (now Uttarakhand) being the center of activity during British regime is having numerous historical brick masonry structures such as churches, missionaries, hospitals, administrative building and educational institutions required to be safeguarded against catastrophic future earthquakes. One such building: Forest Research Institute Dehradun which suffered extensive damages during the Uttarkashi earthquake has been considered for seismic vulnerability assessment and achieving a generalized retrofitting strategy for the region which can be extrapolated globally. Structural assessment by non-linear static analysis has been carried out for FRP retrofitted and an un-retrofitted building using FEM. Different types of FRP has been modeled numerically as wrapped around the piers of huge brick masonry structure and analyzed under site specific earthquake loading which reported in an improved performance of strengthened structure.

To validate the seismic retrofitting of buildings quantitatively, we observed microtremors in the Uji campus buildings at Kyoto University. We compared the dynamic characteristics derived from the resonant frequency of microtremors in a five-story steel-frame structure and a three-story reinforced-concrete (RC) building before and after retrofitting. We calculated the weight of the building from the retrofitting design plan and constructed a numerical model of the structure by estimating the building stiffness that fits the resonant frequency. Assuming the characteristics of the restoring force for each story of the numerical model from previous studies, we calculated the non-linear response of the building to the strong motions predicted for earthquakes occurring at the Obaku fault system that runs right in front of the Uji campus. We compared the response of the numerical models constructed before and after retrofitting to verify the effects of the seismic retrofitting. We found that the proposed method of dynamic response model construction using microtremor observations is effective when the reinforcement members are rigidly fixed to the existing structure, as is the case for RC buildings.

This research provides a practical and feasible retrofitting solution for soft story in reinforced concrete (RC) buildings with masonry infill walls for example in Nepal through numerical analysis. It is well understood that stiffness and strength of the soft story floor can be increased significantly by adding RC shear wall in the frame opening of the ground floor, making lateral deformation of that floor negligible. With this consideration, the authors have developed a numerical optimization framework for optimizing the RC shear wall in the open floor of soft story building incorporating socio-technical aspects from their previous publication [Timsina, K., Gadagamma, C. K., Numada, M. and Meguro, K. [2019b] “Development of a numerical optimization framework for solving soft-story problem in reinforced concrete frame buildings,” Seisan-Kenkyu]. The objective function for numerical optimization is cost minimization with the constraints of usability, performance, and complexity from a detailed field study. In this paper, the numerical optimization framework is developed and solved using the sequential quadratic programing (SQP). The whole scheme has been incorporated inside the 2D-Applied Element Method (AEM). The retrofitting solution thus obtained from the numerical optimization has been analyzed using the incremental dynamic analysis to know the capacity of the frame structure in earthquake ground motion. It shows that the retrofitting method can significantly enhance the soft story frame’s capacity and ensure the dwellers’ interests are not compromised.

Heat exchanger networks (HENs) are employed in process industries to decrease external utilities required. Retrofitting HENs in numerous plants designed in the past and operating currently can achieve significant energy savings for a small investment. For solving HEN retrofitting problems, stochastic global optimization (SGO) methods such as genetic algorithm and differential evolution are gaining popularity. This chapter is on an important issue in HEN retrofitting using SGO methods. HEN retrofitting often has inequality constraints on approach temperatures, which can be handled in SGO methods by using the penalty function method or feasibility approach. In this chapter, these two common methods are analyzed for HEN retrofitting by integrated differential evolution for single-objective optimization and elitist nondominated sorting genetic algorithm for multi-objective optimization, to establish their relative advantages. Results on two case studies for single and bi-objective optimization show that the penalty function method with a reasonable value for the penalty parameter gives better optimal solutions than the feasibility approach for HEN retrofitting problems tested.