New Eco-friendly Two-way Void Slab

Transcription

1 New Eco-friendly Two-way Void Slab Tae-Young Jang 1, a, Sang-Mo Kim 2, b, Sang-Dae Kim 3, c 1 TVS Forum co., Ltd., , Seocho-dong Seocho-gu, Seoul, Korea, TVS Forum co., Ltd., , Seocho-dong Seocho-gu, Seoul, Korea, Dept. of Civil, Environmental and Architectural Eng., Korea University, Seoul, Korea, a jjang0121@korea.ac.kr, b sensesm@yahoo.co.kr, c sdkim@korea.ac.kr ABSTRACT In order to reduce environmental burdens causing global warming, construction industry, known as anti-environmental industry, makes an effort to reduce fossil energy consumption by the reduction of CO 2 emissions in the construction stage. This paper shows a new way to reduce environmental impacts through the usage of Eco-friendly Two-way Void Slab System has been being applied to many projects in the world. (E.g. Europe, North America, Oceania, and so on) So this paper verified structural concept and performance, economic effects of Two-way Void Slab and analyzed CO 2 emission reduction effect through construction materials. KEYWORDS: Two-way Void Slab (TVS), Flat Plate, CO 2 emission reduction 1. INTRODUCTION The environmental sustainability caused by greenhouse gas increase is the most critical issue nowadays in the global society. According to the declaration on Low Carbon Green Growth in South Korea, the interest in green building, ecological building, or sustainable building has been increased. Here, sustainable means the environment-friendly design, construction, maintenance and demolition of buildings. Also the macroscopic concept of sustainable includes the economic, environmental, and social aspects during the total life cycle of buildings. Two-way Void Slab was developed already in 90's in foreign countries and applied to the numerous projects. But it was developed just a few years ago in South Korea and started to apply to the some projects. Two-way Void Slab System qualified for green building certification in Europe, North America, Oceania, and so on. The certification are due to eco-friendly effects such as saving fossil energy and reducing CO 2 emission by the reduction of concrete and reinforcing bar, increasing insulation performance and using reducing seismic load by vacating middle of slab through recycled plastic ball as void former. 2. CONCEPT OF TVS SYSTEM Two-way Void Slab is an efficient two-way slab system eliminating concrete form the middle of flat plate without any beams and it is similar to the concept waffle slab. The structural dead weight reduction by concrete savings permits long span structure. In Figure 1 one unit and install concept of TVS system are shown. 671

2 (a) One unit Figure 1. Figure of TVS System (b) Install Concept As Two-way Void Slab has the most efficient section for bending stress like H-shape steel beam, it is very reasonable slab system containing concrete savings effect. Figure 2 shows the structural concept of TVS system. (a) Section Figure 2. Structural Concept of TVS System (b) Stress-block 3. STRUCTURAL PERFORMANCE TESTS OF TVS SYSTEM This paper was referred to experimental results of TVS system developed by TVS Forum in South Korea in order to evaluate the structural performance and compare with flat plate system. In foreign countries, the paper related with structural performance of Two-way Void Slab has been released and received various project awards. But research and interest of Two-way Void Slab in South Korea are at the very beginning. Figure 3, 4 shows image of specimens and test setup. Also specimens were occurred crack-patterns as shown in Figure 5. Figure 3. Figure of Specimens 672

3 Figure 4. Test setup Figure 5. Crack-pattern From the results of structural performance tests, it can be seen that the bending strengths of all the bending specimens were larger than the ultimate bending strength on a basis of theory and the shear strengths of all the shear specimens were larger than 60 percent of the shear strength as shown in Figure 6. In order to increase the shear strength capacity and bending moment in the areas with stress concentration (E.g. near the columns or walls) it is possible that plastic balls as void former are uninstalled. Due to advantage of dead weight reduction of floor slabs, TVS system is more structural safety and economic than flat plate system as other papers in foreign countries. Figure 6. Load-Displacement Curve 4. ECONOMIC EVALUATION OF TVS SYSTEM 4.1 Seismic Load Resisting Effects Copenhagen Technical Academy in Denmark, 2008 released a paper for earthquake resistance building methods. (E.g. Soft first floor, Damper system, Base Isolators, Bubbledeck, etc.) That paper introduced two-way void slab system as one of earthquake resistance systems. Also the analysis verified the impact of seismic load reduction on dynamic load of buildings resulted from dead weight reduction of TVS system. Civil and Environmental Department of University of Iceland, 2005 released a paper on seismic analysis of high building with biaxial hollow slabs. But no cases of these researches are reported in South Korea. 673

4 The objective building is actually being constructed nearby Seoul and is reinforced concrete structure. Also the building size is ground 66 stories and underground 7 stories. TVS system is applied to the project (Slab thickness, 250mm) on behalf of flat plate system. (Slab thickness, 250mm) And other structural members equal to the original size. In case of TVS system, it is able to modify the section area of vertical members according to advantages of more gravity and seismic load reduction than flat plate system. But no modification compared with floor to floor slab in order to convenience of analysis. Figure 7 shows the 3D modelling image of the objective building. In the results of analysis, floor load reduced 15 percent for gravity load and dead load reduced 8 percent of typical floor contained vertical member. Total dead load of ground floor reduced 6 percent. Also dead weight of floor slab reduced 29 percent because of TVS system. Finally seismic load reduced 6 percent according to reduction of total building weight. Story shear force is as shown in Figure 8. Figure 7. 3D Modelling (a) X-dir. (b) Y-dir. Figure 8. Story Shear Force 4.2 Savings Effects under Framings In case of object building applied TVS system, concrete and reinforcing bar savings is the same as graphs shown as Figure 9~11. There is no concrete savings of column and wall because the structural design was carried out with existing section area size of vertical structural members. (a) Column (b) Wall Figure 9. Reinforcing bar Savings In this paper, quantity or volume for concrete and reinforcing bar of vertical structural members was compared simply. Therefore it is possible to compare construction cost through those values times a unit cost of TVS system. Concrete and reinforcing bar savings effect on typical floor coming from building weight reduction through 29 percent concrete savings in floor slabs is shown as Figure 11. And Figure 12 shows reinforcing bars savings on columns, walls, and slabs. In addition, there are 674

5 considerable effects on construction cost-benefits if secondary saving effects (I.e. foundation volume, excavation, fast installation, etc.) are considered. In case of object building applied TVS system, concrete and reinforcing bar saving is the same as graphs shown as Figure 9~11. There is no concrete savings of column and wall because the structural design was carried out with existing section area size of vertical structural members. Figure 10. Typical Floor Figure 11. Total Reinforcing bar Savings In this paper, quantity or volume for concrete and reinforcing bar of vertical structural members was compared simply. Therefore it is possible to compare construction cost through those values times TVS unit cost. Concrete and reinforcing bar savings effect of typical floor because of building weight reduction through 29 percent concrete savings of floor slabs is shown as Figure 11. And Figure 12 shows reinforcing bars savings on columns, walls, and slabs. In addition, there are considerable effects of construction cost savings if secondary savings effects (I.e. foundation volume, excavation, fast installation, etc.) were reflected. 4.3 Savings Effects after Framings In building construction applied TVS system, economic effects after frame work are as follows: The finishing material saving effect is expected through saving story height compared with general rahmen structure. It will be allowed for elimination of vibration isolating material for reduction of floor impact sound because of performance enhance of floor vibration. Also it is able to expect energy savings effect through insulation performance enhancement by installation of recycled plastic ball as void formers and CO 2 emissions reduction effect through concrete and reinforcing bar savings. 5. ENVIRONMENTAL EVALUATION OF TVS SYSTEM 5.1 Less Material Consumption Effects There is energy saving effect due to reducing unnecessary construction materials by applying TVS system. In foreign countries, two-way void slab qualified for green building certification (E.g. LEED, BREEAM, Green Star, etc.) in materials and resources. 5.2 CO2 Emission Reduction Effects The total amount of CO 2 emissions of South Korea reaches 480 million tons approximately and recently ranked 9 th in the world. Besides, the total amount of CO 2 emissions in the building sector reaches 23 percent. And the CO 2 emissions quantity in the construction stage of total life cycle of buildings reaches especially 7.8 percent. It is known that the reinforced concrete work among whole construction works occupies 90 percent or more. In order to estimate the amount of CO 2 emissions in floor slab work of buildings, we assumed that the average slab thickness is 210mm and that the reinforcing bar quantity is 120kg/m 3 and the average construction areas (about 85,000,000m 2 ) are based on data for the last three years. Accordingly, the amount of CO 2 emissions in building s floor slab reaches about 13 million tons per year. (I.e. 5.4 million tons by concrete and 7.6 million tons by reinforcing bar) This is large amount of CO 2, which accounts for 3 percent of the South Korea s total CO 2 emissions in a year. But the actual amount of CO 2 emission may be larger than that because we exclude the concrete and reinforcing bar quantities of beam members in assessment for the convenience. Finally, the reduction of CO 2 emissions through TVS system as shown in Figure 12 reaches about 3.7 million tons even if that is estimated conservatively for being limited to housing and office building 675

6 (a) Concrete Figure 12. CO2 emission reduction (b) Reinforcement 5.3 Recycled Resources Effects The void former, one of t he primary elements of TVS sy stem, is made from recycled plastic and it i s effective to saving the resources through reuse of waste materials. Also such effects will be maximized by new eco t echnologies all the m ore. (E.g. th e plastic production technology using trapped CO 2 and recycled plastic, etc.) 6. CONCLUSIONS TVS sy stem, new eco-friendl y slab s ystem, has the structural, economic, and environmental effects compared with existing general floor slabs during th e total life cycle of buildings. Also TVS sy stem can be a potent alternative for sustainable natu re, and symbiosis between hu man and nat ure beyond green and ecological bu ilding. We have to tr y to develop green technologies to minimize environmental im pacts by improving the eco-friendly technologies in field of construction work of buildings as long as mankind exists on this planet. REFERENCES 한용섭, 김상대, 구조계획측면에서본구조재료별 CO2 발생량비교연구, 대한건축학회추계학술발표대회논문집 ( 구조계 ), v.25 n.01, pp.203~206, 김상모, 장태영, 김상섭, 이방향중공슬래브의구조성능평가, 대한건축학회논문집 ( 구조계 ), v.25 n.08, pp.35~42, 김상우, 황현복, 황현식, 이기장, 이동근, 이정윤, 철근콘크리트이방향중공하프슬래브의휨성능에관한실험적연구, 대한건축학회논문집 ( 구조계 ), v.25 n.08, pp.11~18, 김민균, 박현재, 이동근, 황현식, 김현수, 보행하중에대한 2 방향중공슬래브의진동성능평가, 한국지진공학회논문집, v.13 n.05, pp.11~21, 이우석, 조승호, 이상현, 조상규, 정란, 타원구를사용한중공슬래브의휨강도와휨강성, 대한건축학회논문집 ( 구조계 ), v.25 n.01, pp.49~56, Markus Aldejohann, Martina Schnellenbach-Held, Investigations on the Shear Capacity of Biaxial Hollow Slabs Test Results and Evaluation, Darmstadt Concrete 18, Markus Aldejohann, Martina Schnellenbach-Held, Zweiachsige Hohlkorperdecken in Theorie und Versuchen; Biaxial hollow slabs, theory and tests, Betonwerk + Fertigteil-Technik, seiten 50-59, 10/ Leonhardt, F., Walther, Reducing the Shear Reinforcement in Reinforced Concrete Beams and Slabs, Magazine of Concrete Research, Vol.17, No.53, pp December BubbleDeck Tests and Reports Summary, June 2006, Issue 1. Earthquake Engineering Structures on earthquake areas and earthquake technology, KOBENHANVS technical school business college, B.Sc Dissertation in Constructing Architecture 7 th semester Seismic analysis high building with biaxial hollow slab, University of Iceland, Master of Civil and Environmental Department, April