Key issues regarding interaction of adjacent RC structures

In this study, the key parameters of structural pounding and their influence on the ductility and shear requirements of reinforced concrete structures with different story heights are presented. The examined structures are multistory reinforced concrete (RC) frames with unequal total heights designed according to the codes EC2 and EC8. Results of an extensive investigation in this field indicate that the most vital issues for the seismic response of the RC structures with interaction problems are: the gap distance separation between the adjacent structures, the location of the point of the column that suffers the hit, the difference of the number of stories between the adjacent structures, the local response of the columns that suffer the impact, the local response of the RC beam-column joints at the level of the pounding the existence of masonry infill panels and their response. Each of these parameters is analysed and its importance on the seismic performance of the RC structures is evaluated. Further, initial results based on dynamic step by step analyses have shown that the seismic demand and the level of the seismic hazard are important parameters for the assessment of RC structures with pounding problems. These parameters could be used in the design process in order to eliminate the critically increasing local requirements of the structural members due to the pounding effect. In this view, it seems to be appropriate that the codes provisions for the evaluation of an adequate gap distance between adjacent RC structures take into account the seismic demand and the level of the seismic hazard.

Interaction of adjacent multi-storey RC frames at significant damage and near collapse limit states

The interaction problem between adjacent multi-storey reinforced concrete structures with unequal storey levels and different total heights at different limit states for three intensity levels of seismic hazard is evaluated. The seismic performance of the external column of the tall building that suffers the impact from the upper floor slab of the adjacent shorter structure is under consideration. The critical column’s local requirements are checked at three different seismic demands according to the Eurocode 8 – part 3: (a) demand for damage limitation limit state (b) demand for significant damage limit state and (c) demand for near collapse limit state. More than 252 nonlinear dynamic step by step analyses have been performed. The results indicate that the column that suffers the impact appears to be in a critical condition due to high ductility demands when the limit state for the assessment is increased from damage limitation to significant damage and to near collapse state. As expected, the column that suffers the hit is always in a critical condition due to shear action. The limit state that is adopted for the evaluation of the pounding effect on the maximum shear requirements of the column slightly altered the results. However, the level of the seismic intensity influences the number of times the shear demands of the column exceed the available strength during the analysis. An increase of the developing requirements for inter-storey drift is also observed in all the cases where the seismic intensity is increased and the limit state becomes more exigent. The minimum gap distance between the adjacent structures that is required in order to eliminate the shear demands of the column seems to be depended on the limit state and the level of the seismic hazard that is used for the evaluation.

Plastic disconnection of storey masses for seismic stress control

The paper detects the role of affecting parameters in the performance of a stress\udcontrol technique based on disconnecting seismic masses during strong\udearthquakes. Such a technique assumes that rigid-plastic connectors are inserted\udbetween structural and non-structural floor masses to detach portions of active\udmass as soon as a pre-set level of horizontal load is reached. By means of a wide\udnumerical investigation on linear and non-linear single-storey frames acted upon\udby different strong recorded ground motions, the present paper highlights the\udranges within which the governing parameters should be set to make the stress\udcontrol effective. In view of a practical application of the considered technique, a\udsimple procedure is also provided to derive the stress reduction from the EC8\uddesign response spectrum for given values of the key parameters

The local site response for upgrading the existing buildings against seismic hazard

The analysis of seismic ground response at the site was conducted using a numerical method, which is developed in three main phases: the definition of the geometric, geological and geotechnical model of the subsurface, the definition of the seismic input, the choice of one or more computer codes to use and the processing of the results. The reconstruction of the geological and geotechnical model of the subsurface has highlighted a morphology quite irregular especially with regard to the covers. In order to assess the effects due to the local stratigraphy, it has been decided to carry out seismic 1-D response analyses, using the computer codes EERA and STRATA. The 1-D analysis was also used for the calibration of computer codes by the modelling of simplified systems and comparing the results obtained by the different codes in order to verify its adequacy. The site response analyses have been developed for some sites in the city of Catania (Italy). On the sites some strategic buildings are localised to upgrade against seismic risk. In situ investigations were carried out in order to determine the soil profile and the geotechnical characteristics for the sites under consideration, with special attention given to the variation of shear modulus and damping with depth. Seismic Dilatometer Marchetti Tests (SDMT) have been carried out, with the aim of evaluating the soil profile of shear wave velocity (Vs). Moreover the following investigations in the laboratory were carried out on undisturbed samples: Resonant Column tests; Direct shear tests; Triaxial tests. The available data obtained from the Seismic Dilatometer Marchetti Tests results enabled us to evaluate the shear modulus profile.

Experimental application of a wireless earthquake damage monitoring system (WiAMS) using PZT transducers in reinforced concrete beams

An innovative portable wireless real time structural health monitoring system that can detect the earthquake damage and the structural integrity of reinforced concrete members in seismic-prone regions is experimentally evaluated. Damage detection is achieved by the use of piezoelectric transducers (actuators/sensors) and the implementation of an integration analytical approach based on the electromechanical impedance method. In this direction, piezoelectric lead zirconate titanate (PZT) transducers are bonded on the surface of the steel reinforcing bars of two large-scale reinforced concrete beams. Tested beams subjected to typical flexural monotonic and cyclic loadings and damage monitoring was performed at different loading levels, before and after yielding, using the developed system. Comparisons of the response signals acquired from the bonded piezoelectric patches for the healthy and the damaged states showed a clear gradation of the examined damage levels and provide cogent evidence that the monitoring system is sensitive from an early stage of the performed tests. The effectiveness of this structural health Wireless impedance or Admittance Monitoring System (WiAMS) to detect concrete cracking and steel yielding due to seismic excitations is also commented on. First results showed that the use of PZTs for detecting earthquake damages in reinforced concrete structures by

Experimental assessment of RC exterior beam-column joints without transverse reinforcement

In the assessment of the performance of typical existing buildings, seismic \udcollapse safety might be significantly affected by the non-linear behaviour of the \udjoints that are involved in the failure\ud mechanisms, especially if they are \udcharacterized by poor structural detaili\udng, such as the lack of an adequate \udtransverse reinforcement in the joint panel. \udMany retrofit strategies for ex\udisting joints are available, but commonly \udaccepted tools to assess existing joint capac\udity – which is the starting point for \udretrofit – are not available. Few reliable \udapproaches for modelling all sources of \udnonlinearity are proposed in literature for poorly designed beam-column joints \udbecause of relatively poor informa\udtion from experimental tests. \udThe current study aims to improve the understanding of exterior joint seismic \udperformance without transverse reinforcement in existing RC buildings through \udexperimental tests. \udTwo full-scale exterior unreinfor\udced beam-column joint sub-assemblages are \udtested under cyclic loading. Two different kinds of joint failure are expected, \udwith or without the yielding of the adjacent beam, basically depending on the \udbeam longitudinal reinforcement ratio. Stra\udin gauges located on beam bars and \udLVDTs on the joint panel allow the complete definition of the deformability \udcontributions. \udDesign criteria, adopted setup and \udmain experimental results are described

Estimation of landfill gas production and the energy potential of municipal solid wastes from the Upper Dagong dumpsite using the Philippine Landfill Gas Model v.1

Landfill gas (LFG) emissions are an important environmental concern in the Philippines due to the existence of several uncontrolled dump sites. LFG mostly results from the anaerobic decomposition of the biodegradable fraction, i.e. kitchen and yard wastes, in municipal solid wastes (MSW) that are disposed of in these disposal sites. This investigation was conducted to estimate the amount of LFG production and the amount of power that could be generated from the Upper Dagong dump site in Cagayan de Oro City, Philippines. This dump site started operating in 1996 and is expected to have a life span of up to 25 years. The Philippine Landfill Gas Model v.1 was used to estimate the rate of LFG generation. Model results show that the rate of LFG generation from MSW plateaued at around 2.4 Mm 3 for 5 years from 2005, one year after the highest waste acceptance at the site, until 2008. The years 2004 and 2005 showed a decrease in waste acceptance rates at the dump site, but increased by around 17% in the following years. Methane generation rates could be seen to rise again from 2009 to reach its projected second peak in 2022. The power that could have been obtained from the MSW in the dump site, with 39% LFG recovery, was estimated to be around 2.1 GWh in 2015. This provides a potential for power generation at the Upper Dagong dumpsite. Aside from generating energy, the utilization of the LFG will also create a source of revenue from the sale of certified emission reductions under the Clean Development Mechanism.

Aquatic ecosystem services of reservoirs in semi-arid areas: sustainability and reservoir management

The multiple use of reservoirs is widely accepted, but there are frequent conflicts between water users based on ecological, economic and sociological concerns. The promotion of aquatic ecosystem services is a successful approach to advanced reservoir management. The main aquatic ecosystem services are goods and human benefits such as clean water and hydropower. The sustainability of aquatic ecosystem services must be the aim of a reservoir management plan, and hence adequate water quality and predominantly mesotrophic conditions are necessary. However, eutrophication processes are advanced in many tropical reservoirs, and re-oligotrophication is needed, as has been successfully implemented in temperate lakes. The eutrophication processes and re-oligotrophication potential of tropical reservoirs are significantly different from temperate ecosystems. Studies to quantify the impact of ecosystem services were conducted on the Itaparica reservoir, Sao Francisco River, Brazil, which is located in a semi-arid area. The main disturbance to tropical reservoirs is the change in water level due to hydropower operational conditions. Desiccated areas on the lakeshore have a high potential for nutrient release by sediment mineralization. An increase in the water level promotes the growth of some pioneer plants, such as the water pest, Egeria densa. Intensive net cage aquaculture can lead to an overcharge of the reservoir, and therefore the carrying capacity should be considered. Furthermore, sediment management and the abstraction and re-use for soil amendment has to be managed. The multiple water uses and sustainability of aquatic ecosystem services must be the aim of any reservoir management plan, and the eutrophic level is a key factor due to its impact on water quality.

Effect of plan layout on the sediment control efficiency of slit-check dams for stony type debris flows mitigation

Understanding farmers’ groundwater attitudes for better groundwater management

In India, many farmers rely on groundwater for agricultural production. The individually constructed and managed tube well access to groundwater in hard rock aquifers has enabled the majority of these farmers to improve farm incomes and diversify livelihoods. Extensive groundwater exploitation coupled with the lack of institutional rule to establish new wells and regulate pumping levels by individual well owners had led to over extraction of the resource. This paper presents results of the study conducted in the states of Gujarat and Rajasthan to examine farmers’ attitudes to groundwater use and management; and to test whether their attitudes across catchments are the same. A hierarchical cluster analysis of groundwater attitude held by survey respondents in Megraj (Gujarat) and Dharta (Rajasthan) watersheds was utilised to ascertain this. The results show that there are four distinct clusters present in each watershed. In addition, preferred water management by cluster membership is reported. The paper concludes that there is a need to account for attitudinal diversity when designing groundwater policies and processes to assist communities shape coordinating instruments to sustainably manage local aquifers.