A Study On The Weight-reduction And Water-retained Green Roof

Many advances have already been made on rain-retained green roof.However,due to the backward roof design and some construction reasons,the rain-retained green roof is far from the realization to popularize and apply.Issue like the overweight load has caused the increase in construction costs and the existing roof construction load limited hysteresis of rainwater runoff that becomes the main reason for popularize of rain-retained green roof.Which of the two questions ‘overweight load caused the increase construction costs' and ‘the limited building roof construction load' are related to the key word ‘load'.Reduce the rain-retained green roof's load becomes the key to solve the popularization and the application problems.From the perspective of architecture,analysised the hysteresis of stormwater runoff building roof through different construction and form of the green roof.Summerised the rain-retained green roof's type(the infiltrated green roof and the storaged green roof)and their load requirements.A new light and rain-retained green roof imagination which combined with the infiltration green roof technology and the storage green roof technology has been put forwared.According the objects of lithten the load and strenthenging the hysteresis stormwater runoff function,and the analysis of the releted simulate test device,the five new green roof devices under different rain fall intensity were deisgned to do the storm water runoff simulation test.All simulate test data were analyzed to validate the new light and rain-retained green roof pla in keeping the hysteresis of storm water runoff utility and lighten the load utility.Firstly,analyzes the external factors,the rainfall intensity effect the flow performance of the system,found the interception of rainfall intensity on the roof system ability is affected,but the runoff delay had a greater influence on the discharge capacity,system exhaust performance under low rainfall intensity will be stronger.The second focuses on the influence factors of equipment,and the main analysis are followings: the water detention and retention performance of the convave and convex typed drainage plate compare to the ceramsite grain is superior,and has a smaller weight;the water detention and retention performance of the susbtrate materaials mixed with the light pearlite matrix compare to the original susbstrate is worse,even if its weight is reduced.The perlite substrate material is not suitable for green roof system;the water detention and retention performance of the storage volume proportion in drainage system are analyzed: improving drainage layer storage volume proportion can significantly reduce the roof additioncal load,and water detention and retention ability not to drop much;Considering the overall water detention and retention capacity,it is recommended that the storage volume of drainage layer should not be greater than 50%.A design strategy on the stormwater detention-retention capacity and the additional load analysis of green roof was put forward.For green roof structural materials,a thin vegetated layer and a comination with the soiless cultivate substrate and thick drianage layer should be considered.For green roof construction forms,can be designed as both vertical and horizontal type: green rood on vertical type that added appropriate water storage space(thickning of the drainage layer)would be more efficient to collect rainwater and delay the process of rainwater infiltration,and has a lower relative load;green roof on horizontal type that arrange the ‘green module' area and the ‘reservoir' area in horizontal form can extend the rainwater infiltration process,such as set the reservior under walking panel to collect rainwater for a short time.This study proposed the hysteresis based on load reducing stormwater runoff in green roof design technology will break through the bottleneck of construction cost and the load adaptability,the building green roof technology of hysteresis stormwater runoff is a wider range of popularization and application,will make greater contribution to sponge city construction.