Owing to strong winds during the typhoon season, damage to pilotis in the form of dropout of the exterior materials occurs frequently. Pilotis placed at the end exhibit a large peak wind pressure ...coefficient of the ceiling. In this study, the experimental wind direction angle of wind pressure tests was conducted in seven directions, with wind test angles varying from 0° to 90° at intervals of 15°, centered on the piloti position, which was accomplished using the wind tunnel experimental system. Regardless of the height of the building, the maximum peak wind pressure coefficient was observed at the center of the piloti, whereas the minimum peak wind pressure coefficient was noted at the corners, which corresponds with the wind direction inside the piloti. The distribution of the peak wind pressure coefficient was similar for both suburban and urban environments. However, in urban areas, the maximum peak wind pressure coefficient was approximately 1.4–1.7 times greater than that in suburban areas. The maximum peak wind pressure coefficient of the piloti ceiling was observed at the inside corner, whereas the minimum peak wind pressure coefficient was noted at the outer edge of the ceiling. As the height of the building increased, the maximum peak wind pressure coefficient decreased. Suburban and urban areas exhibited similar peak wind pressure distributions; however, the maximum peak wind pressure coefficient in urban areas was approximately 1.2–1.5 times larger than that in suburban areas.
A strength–ductility type seismic retrofit technique for soft first-story reinforced concrete (RC) buildings via adding wing-walls to the existing RC columns is called thick hybrid wall (THW) ...technique. In this technique, the additional wing-wall does not require longitudinal, transverse and anchor reinforcements; therefore, its construction is easy and cost-effective. In this study, THW technique was applied to an existing pilotis RC building in Okinawa. The objectives of this study were (1) to compare the advantages of THW and conventional retrofit techniques applied to this pilotis building, and (2) to assess the future retrofitting activities through this study.
•An innovative resilient recycled aggregate piloti-type brick masonry structure was proposed.•UHSB were applied to the bottom-storey frame-shear wall structure to achieve the resilient ...performance.•The proposed resilient frame-shear wall structure of bottom storey presented excellent reparability.•The piloti-type brick masonry structure with resilient bottom storey can give full play to the resilience and deformation ability of its bottom-storey structure even with a higher storey stiffness ratio.
A resilient recycled aggregate piloti-type brick masonry structure equipped with ultra-high strength bars (UHSB) in the pilotis and shear walls was proposed. Quasi-static test and finite element analysis based OpenSees were conducted to study its seismic performance. The main parameters include different steel bar categories, reinforcement configurations, storey stiffness ratios and shear wall distributed reinforcement ratios. The results revealed that both the recycled aggregate concrete (RAC) frame-shear wall structure at the first storey and the upper recycled brick masonry structure showed satisfactory deformation performance and stable load-carrying capacity. The frame-shear wall structure at the weak first storey is prone to suffer from shear failure of the shear wall under the relatively large drift due to the larger proportion of shear deformation. The plastic damage of the pilotis and shear wall reinforced with UHSB was obviously reduced. The arrangement of diagonal UHSB in the shear wall can significantly improve the shear resistance and prevent the premature shear failure of the shear wall, and further enhance the resilience and seismic performance of the bottom-storey structure. The proposed resilient frame-shear wall structure of bottom storey presented excellent repairable performance. The innovative piloti-type brick masonry structure with resilient bottom storey can give full play to the resilience and seismic performance of its bottom-storey frame-shear wall structure even with a relatively higher storey stiffness ratio.
This study aims to investigate the influence of shear‐axial force interaction on the seismic performance of a piloti‐type building subjected to the Pohang earthquake. For this purpose, a four‐story ...piloti‐type building in Pohang, Korea whose columns were brutally damaged by the 2017 Pohang earthquake, one of this country's strongest earthquakes in modern history, was chosen as the object of the study. Columns of this piloti‐type building were designed with insufficient transverse reinforcement, resulting in an increased potential for shear‐axial failure. The piloti‐type building was simulated using Zeus‐NL, an efficient analysis and simulation platform developed for earthquake engineering applications to perform nonlinear time history analysis. A hysteretic shear model in Zeus‐NL capable of accounting for the variation in column axial force was adopted to capture the effect of the shear‐axial force interaction, caused by a combination of horizontal and vertical ground motions. The shear model was validated by comparing the simulated and experimental results. The seismic performance of the piloti‐type building under the effect of the shear‐axial force interaction was compared with that under the shear effect only. Results have indicated that shear effect and shear‐axial force interaction effect significantly reduce column maximum shear force and increase column drift demand. The influence is more intense considering shear‐axial interaction. The seismic response in terms of hysteretic behavior, energy dissipation, and stiffness degradation is presented and discussed.
•Establish a numerical model for typical piloti-type building structures with vertical irregularities in Korea.•Show the inadequacy of existing limit states through correlation analysis between IDR ...and concrete strain.•Propose strain-based limit states for piloti-type structures to exhibit local damage due to vertical irregularity.•Develop new IDR-based limit states having damage probabilities equivalent to the strain-based limit states.•Verify the developed limit states with observed damage data by introducing a damage probability measure.
Limit states have been widely used as a threshold for classifying and evaluating building damage states either analytically or empirically, and current guidelines or codes generally provide the limit state as interstory drift ratio (IDR) for a single lateral-load resisting system. However, piloti-type structures in Korea have a vertically irregular system consisting of a moment frame for parking lots at the first story and a shear wall system for residential space at upper stories, making it difficult to evaluate the damage states against earthquakes using existing limit states. In this regard, new limit states for the typical piloti-type building structures were developed to evaluate the damage states probabilistically via seismic fragility assessments and verified with observed damage data using a damage probability estimator (DPE). The DPE was introduced as a probabilistic damage measure available from both analytical and empirical ways. First, a prototype model for the typical piloti-type structures damaged during the 2017 Pohang earthquake was proposed to simulate seismic demands in terms of both IDR and concrete strain. Second, strain-based limit states were examined and determined to use as an alternative to the existing IDR-based limit states. Finally, the new IDR-based limit states were developed on the basis of correlation between IDR and concrete strain to reflect local damage under vertical irregularity. The results revealed that the new IDR-based limit states were determined as approximately 30% reduction from the existing IDR-based limit states and the feasibility of the new limit states was validated with the observed damage data obtained from the 2017 Pohang earthquake. The seismic fragility function updated based on the new limit state could estimate more reliable damage states of the piloti-type residential buildings.
To investigate the post-earthquake repairability of the resilient structure utilizing ultra-high strength bar, an earthquake-damaged piloti-type masonry structure specimen reinforced with ultra-high ...strength bar was rehabilitated through a composite rehabilitation strategy. The rehabilitation approach incorporated a prefabricated steel sleeve and carbon fiber reinforced polymer was adopted for the frame-shear wall structure at the piloti-storey, along with a combination of steel plate application and steel mesh mortar for repairing the masonry wall. The seismic behavior of the rehabilitated structure was investigated through quasi-static test and OpenSees numerical simulation platform. The results showed that: The piloti-type masonry structure with ultra-high strength rebar showed excellent repairability. The rehabilitation strategy in this study significantly enhanced the stiffness of the damaged recycled aggregate masonry wall, improved the shear resistance of the shear wall, and enhanced the deformation performance of the rehabilitated piloti-type structure. In comparison with the control specimen, the stiffness degradation rate of the rehabilitated specimen decreased obviously, the peak carrying capacity and ultimate drift increased by 21.6 % and 35.4 %, respectively. Moreover, the piloti-storey drift of the rehabilitated specimen can reach 2 %. These research findings serve as a solid foundation for further exploration of post-earthquake repairability in resilient structures and the seismic performance of rehabilitated structures.
•The research object was a resilient recycled aggregate piloti-type masonry structure with ultra-high strength bars.•A rehabilitation scheme was proposed for the earthquake damaged specimen.•The seismic behavior of the rehabilitated structure was investigated through quasistatic test and numerical simulation.•The RAC frame-shear wall structure with ultra-high strength bars at piloti-story presented excellent repairability.•The rehabilitated structure still presented satisfactory seismic and resilient performance.
This study aimed to evaluate the impact of climate change on flood damage and the effects of mitigation measures and combinations of multiple adaptation measures in reducing flood damage. The ...inundation depth was calculated using a two-dimensional unsteady flow model. The flood damage cost was estimated from the unit evaluation value set for each land use and prefectures and the calculated inundation depth distribution. To estimate the flood damage in the near future and the late twenty-first century, five global climate models were used. These models provided daily precipitation, and the change of the extreme precipitation was calculated. In addition to the assessment of the impacts of climate change, certain adaptation measures (land-use control, piloti building, and improvement of flood control level) were discussed, and their effects on flood damage cost reduction were evaluated. In the case of the representative concentration pathway (RCP) 8.5 scenario, the damage cost in the late twenty-first century will increase to 57% of that in the late twentieth century. However, if mitigation measures were to be undertaken according to RCP2.6 standards, the increase of the flood damage cost will stop, and the increase of the flood damage cost will be 28% of that in the late twentieth century. By implementing adaptation measures in combination rather than individually, it is possible to keep the damage cost in the future period even below that in the late twentieth century. By implementing both mitigation and adaptation measures, it is possible to reduce the flood damage cost in the late twenty-first century to 69% of that in the late twentieth century.
People in hot and humid areas prefer exercising in sheltered spaces, such as pilotis, to avoid direct solar radiation. However, as a piloti space for exercise (PSE) is susceptible to the outdoor ...environment, it is unclear whether the thermal environment in the PSE satisfies the thermal needs of exercisers exhibiting high metabolic rates. This study investigated the relationship between the thermal environment of PSEs and the thermal response of exercisers. A field survey was conducted in the PSE of a gymnasium in Guangzhou, China, during the summer of 2019. The subjective responses of 28 subjects were collected through questionnaires under various activities, including 3.6 MET shoot (Ex 1), sitting (Post-Ex 1), 5.2 MET layup (Ex 2), sitting (Post-Ex 2), 6.8 MET full-court dribbling shuttle run (Ex 3), and sitting (Post-Ex 3). The environmental and physiological data were recorded using instruments. We documented the fluctuations of mean skin temperature, thermal sensation, thermal acceptability, and sweat feeling index of subjects during the aforementioned activities. The recovery times of thermal acceptability returning to the acceptable state were within 5, 4–22, and 10–39 min during Post-Ex 1, 2, and 3, respectively. The upper limits of the 80% acceptable operative temperatures during Ex 1, 2, and 3 were 32.6, 31.2, and 29.0 °C, respectively. This study contributes to a better understanding of the dynamic changes of exercisers’ thermal responses in the naturally ventilated environment and provides a reference for the evaluation and design of PSEs in hot and humid areas.
•Thermal response of exercisers was explored in piloti space for exercise.•Shooting, layup and shuttle run (Ex 1–3) were 3.6, 5.2, and 6.8 MET, respectively.•Upper limits of acceptable temperature under Ex 1–3 were 32.6, 31.2 and 29 °C.•The relationship between acceptable temperature and exercise duration was built.•Recovery times of thermal acceptability under Ex 1–3 were <5, 4–22 and 10–39 min.
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