There is a global trend for seismic response improvement of new buildings to reduce cost and future damage. It is also important to improve existing structures that are designed without consideration of seismic load or using old provisions that cannot meet the new one. The objective of this paper is to draw attention to evaluate existing reinforced concrete school buildings, then to present a proposed methodology to improve the behaviour of such schools with low cost especially in a developing country. The proposed method uses overhead water tanks as a tuned mass damper. A pushover analysis has been performed to evaluate the existing schools and perform a feasibility study to select the best solution to achieve seismic response improvement of the existing structure. Of course, the proposed methodology can be applied easily to other existing structures.
Egypt is a developing country and many buildings are not designed to sustain lateral seismic loads. Moreover, there is no governmental interest to evaluate, upgrade buildings to sustain lateral loads or to check buildings with current Egyptian code for loads.
Schools are considered lifeline structures in Egypt, because of its high occupancy, being used as a shelter in case of a catastrophic problem, and its importance to keep development in education and future.
After 1992 Dahshour Earthquake, the Egyptian government has established the Governmental Authority for Educational Buildings (GAEB) and released Egyptian code for loads ECP 201-1993 [
This paper presents an evaluation of an existing school prototype building under 1993 and 2012 Egyptian codes, and then displays a proposed system for seismic response improvement. The proposed seismic improvement methodology is based on using water tanks as a Tuned Mass Damper (TMD). Pushover analysis is used as a tool and technique to evaluate the nonlinear behaviour of existing building and examine the feasibility of the proposed improvement method.
Although many research works addressed the problem of seismic risk evaluation of existing building in Egypt [
Port Said is a coastal city in Egypt and located in zone 3 on the seismic zone map [
SAP 2000 V17 [
Base shear = V = ZICKSW | |
---|---|
Z = Seismic zoning factor | 0.3 |
I = Importance factor | 1.25 |
T = Period | 0.09 H/B |
K = Structural system factor | 0.8 |
S = Soil factor | 1.15 |
V = Base shear | 109 ton (working load) |
Base shear = Sd(t) = ag γ S 2.5/R | |
---|---|
ag = Ground acceleration | 0.15 g |
γ = Importance factor | 1.25 |
S = Soil factor | 1.15 |
R = Response modification factor | 5 |
TB | 0.2 |
TC | 0.6 |
TD | 2 |
Ct | 0.075 |
V = Base shear | 166 ton (working load) |
After checking of the building elements, it is found that, the building is safe when subjected to the seismic load from ECP201-1993, as shown in
Liquid Mass Dampers have been used to stabilize marine vessels or to control a wobbling motion of satellites since 1950, and then was used in structural engineering to reduce lateral displacement. Many experimental and analytical studies have been done to measure the effectiveness of water damper. Some studies use water tanks as Tuned Mass Damper (TMD) based on Water-Structure mass ratio [
Moreover, some researchers discuss the combination of TMD and TLD at the same model and its effect on earthquake response control of buildings [
It worthy to mention that American code ACI 350.3 [
resist lateral load developing from water structure interaction (impulsive and convective force), i.e., to design water containing tanks itself without considering the effect of tanks at the roof of structures.
This paper presents a study for improvement of an existing school building in Port Said, Egypt. As Egypt is a developing country, the proposed methodology is to use tanks as a TMD. This paper presents an appropriate solution for existing important structures in developing country, and draws attention to improving seismic behaviour of existing structures with low cost using tanks to act in two options; the first is to satisfy the fire fighting requirement of Civil Defence Authority (CDA), second, is to improve the seismic response behaviour of the existing building.
This study has been done considering variation in the mass ratio (water to structure mass ratio μ) in two cases. The first case with one tank at the centre of the roof area, the second case with two tanks on the roof located in a symmetrical position as displayed in
Three-dimensional pushover analysis has been done for 20 models in X and Y direction using SAP 2000 V 17. Then a feasibility study of various water TMDs is studied using pushover analysis. This feasibility study has been done to evaluate which case is the optimum solution to improve the seismic response of the existing building.
Pushover analysis is a nonlinear static analysis which is widely used all over the world to evaluate of buildings. This paper uses pushover analysis as a tool to evaluate existing structure with and without tanks. The analysis procedure is done based on a gradually lateral movement of structure to reach a target displacement. The target displacement based on building height and applied lateral load. During this movement, there is a formation of plastic hinges in each step.
Pushover analysis has been used in many researches as a technique to evaluate structures, and discuss nonlinear behaviour of structures such as:
・ Devi and Nandini, (2015) [
・ Oyguc and Boduroglu, (2012) [
・ Bhatti, and Varum, (2012) [
・ Yasrebinia and Pourshrifi (2012) [
・ Ismaeil, (2014) [
・ Pednekar et al., (2015) [
The analysis using sap 2000 provides the capacity curve, i.e., the force-displacement curve as shown in
After reaching the performance point and corresponding T effective, one can indicate the level, number of plastic hinges and corresponding base shear.
Mass Ratio μ | Water Volume m3 | 1 Tank | 2 Tank | ||
---|---|---|---|---|---|
Variable Water Height G1 | Fixed Water Height G2 | Variable Water Height G3 | Fixed Water Height G4 | ||
B × L × H (m) | B × L × H (m) | B × L × H (m) | B × L × H (m) | ||
0.25% | 7.6 | 3 × 3 × 0.85 | 1.95 × 1.95 × 2.00 | 2 × 2 × 0.95 | 1.38 × 1.38 × 2.00 |
0.50% | 15.2 | 3 × 3 × 1.69 | 2.76 × 2.76 × 2.00 | 2 × 2 × 1.90 | 1.95 × 1.95 × 2.00 |
0.70% | 22.8 | 3 × 3 × 2.53 | 3.38 × 3.38 × 2.00 | 2 × 2 × 2.85 | 2.38 × 2.38 × 2.00 |
1.00% | 30.4 | 3 × 3 × 3.78 | 3.90 × 3.90 × 2.00 | 2 × 2 × 3.80 | 2.76 × 2.76 × 2.00 |
1.50% | 45.6 | 3 × 3 × 5.00 | 4.78 × 4.78 × 2.00 | 2 × 2 × 5.70 | 3.38 × 3.38 × 2.00 |
Level | Description |
---|---|
Operational | Very light damage, no permanent drift, structure retains original strength and stiffness; all systems are normal |
Immediate Occupancy (IO) | Light damage, no permanent drift, structure retains original strength and stiffness, elevator can be restarted, Fire protection operable |
Life Safety (LS) | Moderate damage, some permanent drift, some residual strength and stiffness left in all stories, damage to partition, building may be beyond economical repair |
Collapse Prevention (CP) | Severe damage, large displacement, little residual stiffness and strength but loading bearing column and wall function, building is near collapse |
displacement curve is affected by the variation of mass ratio in the presence of one tank as shown in
Direction | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP |
---|---|---|---|---|---|---|---|---|
X | 1.124 | 22 | 1.1194 | 532.36 | 0.0860 | 464 | 1 | 0 |
23 | 1.1371 | 542.17 | 0.0901 | 467 | 7 | 0 |
Direction | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP |
---|---|---|---|---|---|---|---|---|
Y | 1.107 | 12 | 1.0764 | 493.415 | 0.044 | 295 | 17 | 0 |
13 | 1.1106 | 509.186 | 0.048 | 305 | 23 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.193 | 21 | 1.1874 | 499.00 | 0.085 | 487 | 39 | 0 | |
22 | 1.2185 | 505.31 | 0.090 | 486 | 50 | 0 | |||
0.50% | 1.033 | 21 | 1.0185 | 618.47 | 0.075 | 521 | 21 | 0 | |
22 | 1.0505 | 627.53 | 0.080 | 512 | 35 | 0 | |||
0.70% | 1.108 | 22 | 1.0957 | 545.55 | 0.083 | 468 | 1 | 0 | |
23 | 1.1162 | 555.88 | 0.087 | 472 | 3 | 0 | |||
1.00% | 1.113 | 22 | 1.1128 | 551.70 | 0.086 | 471 | 2 | 0 | |
23 | 1.1311 | 561.09 | 0.090 | 475 | 8 | 0 | |||
1.50% | 1.043 | 21 | 1.0380 | 622.80 | 0.078 | 520 | 25 | 0 | |
22 | 1.0659 | 631.02 | 0.082 | 515 | 37 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.172 | 12 | 1.1618 | 463.98 | 0.044 | 318 | 32 | 0 | |
13 | 1.1998 | 472.07 | 0.048 | 321 | 42 | 0 | |||
0.50% | 1.037 | 12 | 1.0038 | 551.02 | 0.040 | 345 | 26 | 0 | |
13 | 1.0781 | 571.98 | 0.046 | 359 | 44 | 0 | |||
0.70% | 1.093 | 14 | 1.0879 | 522.63 | 0.048 | 333 | 21 | 0 | |
15 | 1.1281 | 536.22 | 0.052 | 345 | 30 | 0 | |||
1.00% | 1.098 | 13 | 1.0673 | 511.96 | 0.045 | 317 | 16 | 0 | |
14 | 1.0998 | 525.56 | 0.049 | 337 | 21 | 0 | |||
1.50% | 1.155 | 13 | 1.1466 | 489.89 | 0.045 | 225 | 56 | 0 | |
14 | 1.1786 | 499.41 | 0.049 | 334 | 62 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.096 | 22 | 1.0856 | 546.25 | 0.082 | 466 | 1 | 0 | |
23 | 1.1015 | 554.62 | 0.086 | 470 | 2 | 0 | |||
0.50% | 1.102 | 27 | 1.1881 | 596.37 | 0.105 | 491 | 37 | 0 | |
28 | 1.2096 | 607.72 | 0.111 | 490 | 47 | 0 | |||
0.70% | 1.156 | 23 | 1.1488 | 518.97 | 0.085 | 521 | 0 | 0 | |
24 | 1.1667 | 526.49 | 0.089 | 529 | 0 | 0 | |||
1.00% | 1.11 | 22 | 1.0970 | 545.47 | 0.083 | 468 | 1 | 0 | |
23 | 1.1159 | 555.31 | 0.087 | 471 | 3 | 0 | |||
1.50% | 1.12 | 22 | 1.1180 | 550.76 | 0.086 | 472 | 2 | 0 | |
23 | 1.1419 | 563.43 | 0.091 | 475 | 12 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.08 | 13 | 1.0625 | 515.36 | 0.044 | 316 | 18 | 0 | |
14 | 1.0981 | 529.39 | 0.048 | 338 | 26 | 0 | |||
0.50% | 1.087 | 13 | 1.0631 | 513.84 | 0.045 | 313 | 17 | 0 | |
14 | 1.0957 | 527.19 | 0.049 | 338 | 23 | 0 | |||
0.70% | 0.985 | 17 | 0.9772 | 650.44 | 0.063 | 287 | 0 | 0 | |
18 | 0.9931 | 686.27 | 0.069 | 290 | 0 | 0 | |||
1.00% | 1.096 | 14 | 1.0898 | 523.00 | 0.048 | 334 | 21 | 0 | |
15 | 1.1309 | 537.56 | 0.053 | 345 | 30 | 0 | |||
1.50% | 1.107 | 13 | 1.0639 | 507.50 | 0.045 | 320 | 10 | 0 | |
14 | 1.0945 | 521.27 | 0.049 | 340 | 20 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.105 | 21 | 1.0961 | 499.00 | 0.0851 | 462 | 1 | 0 | |
22 | 1.1167 | 505.31 | 0.0900 | 467 | 4 | 0 | |||
0.50% | 1.108 | 22 | 1.0983 | 557.59 | 0.0878 | 469 | 4 | 0 | |
23 | 1.1198 | 570.69 | 0.0934 | 469 | 20 | 0 | |||
0.70% | 1.11 | 22 | 1.0896 | 541.05 | 0.0811 | 460 | 0 | 0 | |
23 | 1.1183 | 555.75 | 0.0872 | 467 | 3 | 0 | |||
1.00% | 1.114 | 21 | 1.0937 | 541.37 | 0.0813 | 461 | 0 | 0 | |
22 | 1.1210 | 555.58 | 0.0872 | 469 | 2 | 0 | |||
1.50% | 1.12 | 21 | 1.1054 | 544.45 | 0.0830 | 463 | 1 | 0 | |
22 | 1.1242 | 554.04 | 0.0871 | 470 | 2 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.09 | 13 | 1.0694 | 514.96 | 0.0448 | 318 | 18 | 0 | |
14 | 1.1036 | 528.74 | 0.0489 | 339 | 24 | 0 | |||
0.50% | 1.093 | 13 | 1.0729 | 571.98 | 0.0459 | 319 | 17 | 0 | |
14 | 1.1027 | 584.83 | 0.0501 | 338 | 23 | 0 | |||
0.70% | 1.095 | 13 | 1.0683 | 511.99 | 0.0443 | 317 | 17 | 0 | |
14 | 1.1026 | 526.32 | 0.0485 | 334 | 23 | 0 | |||
1.00% | 1.099 | 13 | 1.0693 | 511.41 | 0.0446 | 316 | 16 | 0 | |
14 | 1.1004 | 525.07 | 0.0485 | 334 | 21 | 0 | |||
1.50% | 1.104 | 11 | 1.0075 | 479.74 | 0.0376 | 303 | 0 | 0 | |
12 | 1.0422 | 496.38 | 0.0413 | 317 | 5 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.096 | 21 | 1.0760 | 541.72 | 0.080 | 459 | 0 | 0 | |
22 | 1.1031 | 555.77 | 0.086 | 467 | 2 | 0 | |||
0.50% | 1.104 | 18 | 1.0025 | 501.17 | 0.065 | 427 | 0 | 0 | |
19 | 1.0231 | 511.07 | 0.069 | 434 | 0 | 0 | |||
0.70% | 1.109 | 21 | 1.0968 | 545.78 | 0.083 | 461 | 1 | 0 | |
22 | 1.1201 | 557.80 | 0.088 | 471 | 3 | 0 | |||
1.00% | 1.116 | 22 | 1.0981 | 542.97 | 0.082 | 462 | 1 | 0 | |
23 | 1.1198 | 553.98 | 0.087 | 468 | 2 | 0 | |||
1.50% | 1.124 | 28 | 1.2320 | 607.99 | 0.111 | 475 | 50 | 0 | |
29 | 1.2570 | 620.45 | 0.118 | 486 | 53 | 0 |
μ % | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | |
---|---|---|---|---|---|---|---|---|---|
0.25% | 1.081 | 13 | 1.0660 | 515.88 | 0.044 | 316 | 20 | 0 | |
14 | 1.1080 | 531.41 | 0.049 | 335 | 30 | 0 | |||
0.50% | 1.089 | 13 | 1.0709 | 515.78 | 0.045 | 318 | 18 | 0 | |
14 | 1.1019 | 528.27 | 0.049 | 339 | 23 | 0 | |||
0.70% | 1.094 | 13 | 1.0720 | 514.74 | 0.045 | 318 | 17 | 0 | |
14 | 1.1033 | 527.57 | 0.049 | 339 | 22 | 0 | |||
1.00% | 1.101 | 13 | 1.0753 | 513.82 | 0.046 | 318 | 16 | 0 | |
14 | 1.1038 | 526.13 | 0.049 | 334 | 21 | 0 | |||
1.50% | 1.108 | 13 | 1.0793 | 513.14 | 0.046 | 318 | 16 | 0 | |
14 | 1.1067 | 525.47 | 0.049 | 335 | 21 | 0 |
sidering performance points and number of plastic hinges in both directions X and Y.
Comparing the results shown in
This study shows that; the use of one tank has a significant effect on improving the seismic response of the
μ = 0.7% | Direction | Teff | Step | T | Base shear (ton) | Displacement (m) | B to IO | IO to LS | LS to CP | Rank | |||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 Tank | Variable water height | G1 | X | 1.108 | 22 | 1.0957 | 545.55 | 0.083 | 468 | 1 | 0 | D | |
23 | 1.1162 | 555.88 | 0.087 | 472 | 3 | 0 | |||||||
Y | 1.093 | 14 | 1.0879 | 522.63 | 0.048 | 333 | 21 | 0 | |||||
15 | 1.1281 | 536.22 | 0.052 | 345 | 30 | 0 | |||||||
Fixed water height | G2 | X | 1.156 | 23 | 1.1488 | 518.97 | 0.085 | 521 | 0 | 0 | A | ||
24 | 1.1667 | 526.49 | 0.089 | 529 | 0 | 0 | |||||||
Y | 0.985 | 17 | 0.9772 | 650.44 | 0.063 | 287 | 0 | 0 | |||||
18 | 0.9931 | 686.27 | 0.069 | 290 | 0 | 0 | |||||||
2 Tank | Variable water height | G3 | X | 1.11 | 22 | 1.0896 | 541.05 | 0.0811 | 460 | 0 | 0 | C | |
23 | 1.1183 | 555.75 | 0.0872 | 467 | 3 | 0 | |||||||
Y | 1.095 | 13 | 1.0683 | 511.99 | 0.0443 | 317 | 17 | 0 | |||||
14 | 1.1026 | 526.32 | 0.0485 | 334 | 23 | 0 | |||||||
Fixed water height | G4 | X | 1.109 | 21 | 1.0968 | 545.78 | 0.083 | 461 | 1 | 0 | B | ||
22 | 1.1201 | 557.80 | 0.088 | 471 | 3 | 0 | |||||||
Y | 1.094 | 13 | 1.0720 | 514.74 | 0.045 | 318 | 17 | 0 | |||||
14 | 1.1033 | 527.57 | 0.049 | 339 | 22 | 0 |
studied building more than the use of two tanks. However Patil et al. [
The results obtained herein agrees with those obtained by Dattatray et al. [
Besides, the mass ratio of 0.7% that gives best results agrees with the mass ratio of 0.7% to 3% obtained by Dattatray et al. [
It is worthy to mention that; the present study considers the nonlinear behaviour of structure while other previous studies considered the static linear analysis.
Seismic response evaluation has been done for existing school prototype building based on the current code for loads, and some vertical elements could not sustain seismic loads. Use the water Tank as TMD is the proposed methodology to improve seismic response for the building. Pushover analysis is performed as a tool to identify the best tank from 20 proposals for different mass ratios, water heights, tank dimensions and number of tanks. It is found that:
1) Using one tank is better than using two tanks with the same mass ratio, and this result is presented in the force-displacement curve.
2) The mass ratio of 0.7% is the best value that can improve the seismic behaviour of the existing prototype school building.
3) Not all the discussed tanks can upgrade the seismic building performance. Some of them decrease the building performance, so it is important to make iterations to select the best solution.
4) The proposed methodology is economical and can be easily performed in all existing reinforced concrete school buildings as it satisfies the following criteria.
a) Meet the civil defence requirement for adding tanks at the roof for fire fighting purposes.
b) Improve seismic performance of the structure.
c) Tanks as a TMD do not need maintenance, just to keep water volume constant.
5) In General, the mass ratio of 0.5% to 1.0% gives better performance more than the other mass ratios.
Therefore, it is recommended that:
1) The proposed methodology can be applied in old buildings to improve the seismic response of structures.
2) The proposed method is economical and the tanks are used for fire fighting and plumbing issue and are used to improve the seismic response of structures, so it is appropriate for developing countries.
3) Three-dimensional pushover analysis can be done to evaluate existing buildings.
4) For the new buildings, it is important to study the effect of top roof tanks on the behaviour of structure regarding lateral loads.
5) American (ACI) and Egyptian (ECP) codes should pay attention to the top-roof tanks. As some can improve the response of structures while others can be harmful to the structure in case of seismic loads.
The authors would like to thank the Governmental Authority for Educational Buildings (GAEB) at Port Said city, Egypt. The research in this paper is based on the data for the existing schools provided by GAEB.
Batool Wahba,Mohamed Sobaih,Adel Akl, (2016) Seismic Response Improvement of Existing Prototype School Buildings Using Water Tanks, Port Said City, Egypt. Open Journal of Civil Engineering,06,117-130. doi: 10.4236/ojce.2016.62011