Experimental dynamic assessment of physical model structure towards holistic renovation
Design, construction, instrumentation, testing and assessment of performance of 3d VF structure towards holistic renovation.
D2.1 Designs and photos of detailing and instrumentation of constructed as-built 3d structure
GREENERGY envisions forest diffusion to alleviate extreme weather conditions impacts in coastal seismic urban regions and to optimize inclusive people-centric social engagement towards habitant comfort and satisfaction, through high-density urban forestation starting from green- renovated buildings. Based on the poor state of the art in the field of renovation towards vertical forests and the great necessity for their urgent development, GREENERGY aims to really cope with detrimental climate change consequences and advance environmental resilience. In that aspect, the experimental quantification of the influence of critical parameters for green holistic renovation of common building to VF building with advanced structural, energy, forestry and habitant comfort performance is crucial. This deliverable concerns the designs and photos of detailing and instrumentation of constructed as-built 3d structure within the framework of workpackage of the experimental dynamic assessment of physical model structure towards holistic renovation. The one-bay, one-storey 3d-structure consists of a slab, four columns, four foundation beams and four brick infill walls. It is scaled down to the capacity of the seismic table of DUTh and refers to old generation design codes for reinforced concrete buildings, having sparse and inadequate steel stirrups and in general poor steel detailing. Further, low strength brick wall infills with low strength brick-joint mortar, cover the two opposite RC frames subjected to out of plane dynamic excitation. Finally, the two opposite RC frames subjected to in plane dynamic excitation include two partial brick wall infills of identical mechanical characteristics. The instrumentation of the structure involves advanced embedded a) innovative PZT sensors inside the concrete mass (columns, slab, and beams hidden in the slabs) as well as b) strain gauges, glued on the longitudinal bars of the four columns. Further, 3d accelerometers are attached on the slab, on the foundation beam and on the infill wall subjected to out of plane dynamic excitation. Finally, draw wire displacement meters are attached on the slab, on the foundation beams and along the diagonals of the partial infill walls subjected to in-plane dynamic excitations. The dynamic excitation of the seismic table will be based on the dynamic characteristics and severity of well-known disastrous Thessaloniki (Volvi) 1978 earthquake. With the as-built reinforced concrete brick infilled structure, GREENERGY aims to assess the dynamic performance of old type deficient structures with the next deliverable D23. GREENERGY envisions forest diffusion to alleviate extreme weather conditions impacts in coastal seismic urban regions and to optimize inclusive people-centric social engagement towards habitant comfort and satisfaction, through high-density urban forestation enabled with innovative and resilient renovations and structural health monitoring.
D2.2 Designs and photos of detailing and instrumentation and structural, energy, forestry retrofit of renovated 3d VF structure
GREENERGY aims to investigate Reinforced Concrete Structure in Seismic Prone Areas after Resilient Vertical Forest Renovation. This report focuses on the retrofitting process of the columns and brick infills of the test specimen, along with the modifications and additions made to receive Vertical Forest (VF) renovations. Special constructions are attached on the structure to simulate eight cases of vertical living walls attachments with different detailing as well as five critical cases of anchoring of simulated planters with wooden trees. The mass and stiffness of the VF constructions and their interfaces are presented in detail. The report outlines, step by step, the applied renovation techniques.
In addition to the extensive instrumentation presented in previous reports of workpackage 2, PZT sensors have been installed in the lightweight PU flexible joint (PUFJ) regions between the brick walls and the concrete columns, on the lightweight external PU glass grid jackets (FRPU jackets) as well as on the basalt rope confinement of columns. Further, PZT sensors instrumented the bottom steel anchors of the vertical living walls as well as their top basalt rope anchor detailing. The PUFJs and the top basalt rope anchors of the vertical living walls received in addition strain gauge.
D2.3 Recorded results and photos of damages of tested as-built structure
GREENERGY aims to assess the dynamic performance of old type deficient structures. This deliverable concerns the recorded results and photos of damages of tested as-built structure within the framework of workpackage of the experimental dynamic assessment of physical model structure towards holistic renovation. The 3d structure is fully instrumented with internal strain gauges on the steel bar surfaces and embedded smart aggregates with PZT sensors. Further, externally bonded PZT patches, attached accelerometers, displacement wire-meters and externally bonded strain gauges are utilized. Two types of tests have been performed, i.e. dynamic shake table tests and tests for determination of dynamic characteristics of the as-built structure. The dynamic shake table tests comprised of gradually increasing maximum input intensity level (peak acceleration of the excitation) from 0,1g to 1,1g based on the adopted earthquake of Thessaloniki 1978. Minor concrete cracking and infill wall partial debonding from the surrounding concrete frames is evidenced without infill wall collapse, at SLS performance level. The PZTs reveal remarkable sensitivity to minor damages inside concrete columns or at the brick infill wall – concrete frame interfaces. Finally, the report gathers the results on material properties for concrete, steel, brick, binder for brick infill construction and for the brick-binder interface (shear strength). Next deliverable D25 will conclude the assessment of the performance of the as-built tested structure in order to receive the Vertical Forest renovation construction.
D2.4 Recorded results and photos of damages of tested renovated 3d VF structure
This deliverable concerns the recorded results and the photographs of damage from experimental tests on the VF renovated structure. The structure is further instrumented with strain gauges and PZTs related to the PUFJs and basalt ropes. The seismic excitations refer to the seismic table acceleration levels followed during the first phase. Furthermore, additional excitation levels cover the equivalent (mass times acceleration) levels because of the additional top slab mass due to VF renovations (simulations of vertical living walls and planters with trees within GREENERGY project). That is, gradually increasing maximum input intensity level (peak acceleration of the excitation based on Thessaloniki 1978 earthquake) from 0.07g, to 0.1g, 0.14g, 0.2g, 0.34g, 0.5g, 0.55g, 0.74g, 0.8g, 1.10g, 1.30g and up to 1.40g. Dynamic table tests for the determination of the dynamic characteristics of the VF renovated rc structure were included for each different level as well. The innovative full green basalt rope wrapping of bottom and top critical regions of rc columns, the innovative construction of PUFJs between the wrapped concrete columns and the brick infills as well as of the one-sided FRPU jacketing of the brick infills resulted in increased stiffness and strength of the structure when compared to the as-built tested structure. The different detailing of attachment, of the vertical living wall constructions and of the planters with wooden sticks, with the use of basalt ropes and PU pads offered remarkable alternatives for innovative Vertical Forest renovations. The Vertical Forest renovations resulted in a significant increase of the top slab mass. Yet, the innovative renovations of the structure prevented out of plane or in plane collapse of brick infill walls as well as rc structure collapse for advanced ULS limit states. It prevented damage of the simulated vertical living walls or of the planters. The PZTs reveal remarkable sensitivity to the damage accumulation inside concrete core or at the brick – mortar joints, feeling also the rocking behavior of planters. Finally, the report gathers the results on brick to brick mortar joints when jacketed with one-side FRPU (brick triplets). Next deliverable D26 will conclude the assessment of the performance of the VF renovated structure.
D2.5 Assessment of the performance of tested as-built structure
GREENERGY aims to assess the dynamic performance of old type deficient structures. The project involves a series of shaking table tests on a one-storey brick wall infilled reinforced concrete building. The as-built structure is subjected to five main different levels of shaking intensity. The earthquake excitations are based on Thessaloniki, 1978 recording with maximum acceleration adjusted to 0,1g or 0,2g or 0,5g or 0,8g or 1,1g accordingly. Also, before and after each earthquake shaking, the structure was excited through the whole range of frequencies of the structure under low acceleration intensity in order to investigate changes in eigen periods of the structure. This assessment focuses on and evaluates the damage caused by shaking table excitations. Regarding damages, after excitations, the structure presented debonding of the full Infill wall between columns 1-2 and 3-4 from the top slab and the adjacent columns’ surfaces. Also, the structure presented debonding of the partial infill walls from column 1 or 2 and from the top slab. The full and partial infill revealed cracking of the horizontal bed joints. The report gathers all maximum and minimum values of bottom foundation and top slab accelerations, column displacement drifts and steel rebar strains. Further, PZT recordings before and after main excitations are thoroughly elaborated.
D2.6 Assessment of the performance of tested renovated 3d VF structure.
The report cites all critical results from the different accelerometers, relative top and bottom accelerations and displacement drifts of the structure during each testing. Further, numerous strain gauges glued at different positions of longitudinal steel bars within critical regions of columns, allow for straight foreword assessment of their axial strain level. The detailed assessment of the renovated structure after the second phase of testing concludes that the partial infill walls suffer bed joint cracking. Damage with crushing of bottom brick at both partial infill walls occurred. No further disintegration of brick infills 1 – 2 and 4 – 3 (out of plane) was observed. No collapse of brick infills was observed for severe seismic excitations, higher than 2g. The columns entered yielding strain of their longitudinal steel reinforcements at the bottom and at the top critical regions (columns 1, 2, 3, 4), leading to a ductile behavior, without disintegration of the concrete core under compression. Basalt rope wrapping of the columns, together with PUFJs and FRPU jacketing of the brick infills resulted in a resilient renovation allowing for interesting damage redistribution and damage barrier mechanisms (through elastic materials). No damage of the retrofit was observed, other than the local fracture of the glass grid of the FRPU near the crushed brick of the partial infill. The structure sustained extremely severe earthquake excitations and developed 2.62% relative displacement drift without accumulation of severe local structural damages or collapse. The tests were terminated as after the successive severe seismic excitations and the crushing of two bottom bricks, the structure exhibited very low stiffness (development of horizontal displacement for very low horizontal loads) but with recovery capacity (because of the elastic PUFJ and FRPU jacketing and VF renovations) and relatively low residual drift. The crushing of two bottom bricks did not pose any threat to human life at advanced ULS performance levels for brick infills or RC structure. The 5 different simulated planters with the trees (P) presented a remarkably resilient performance up to very severe seismic excitations, avoiding planter overturning or damage. The different anchoring detailing provided a holistic insight on the design of common steel or green, natural recyclable, replaceable, non-corrosive, lightweight and fire-resistant anchoring through basalt ropes. PM pads offered a very resilient alternative foundation of planter 4 up to significant seismic excitations. The 8 different simulated vertical living walls (LW) presented a remarkably resilient performance up to very severe seismic excitations offering several alternatives for top elastic support through basalt ropes and flexible PM pads against the concrete slab to avoid local damage and non-desirable interaction or slip. No serious damage accumulation for different LWs was observed up to severe seismic excitations. PZTs provide a reliable framework for assessing the health condition of renovated RC structures at various locations. They also show potential for evaluating additional materials incorporated into the VF structure. This assessment is based on RMSD values obtained from PZT measurements, which enable a detailed correlation between sensor data and the location and extent of damage observed in situ. For all PZTs, including those attached to VF materials, the RMSD values demonstrate a consistent increasing trend from the initial 0.1g excitation through subsequent excitations. The VF renovated showed lower displacement drifts for equivalent acceleration top mass levels (accounting for the additional top mass because of the planters and living wall structures) because of the innovative lightweight, non-corrosive, flexible retrofits. That is an interesting increase of stiffness. For EQ1.1g the drift of the renovated structure was similar to the one during the first phase despite the significantly increased top mass of the VF renovated structure. The second phase of the seismic testing is completed successfully, based on the advanced ULS level damages of the VF renovated structure after the execution of 28 dynamic tests, including 13 levels of earthquake excitations. The large number of severe excitations reveal a high potential for energy absorption by the VF renovated structure.
