3 story hospital seismic loading

ICCBT 2008 - C - (35) - pp377-388

ICCBT2008

Analysis and Design of 3 Storey Hospital Structure Subjected To Seismic Load Using STAAD PRO

M. I. Adiyanto*, Universiti Sains Malaysia, MALAYSIA

T. A. Majid, Universiti Sains Malaysia, MALAYSIA S. S. Zaini, Universiti Sains Malaysia, MALAYSIA ABSTRACT Before the disaster of the century known as ‘The Terrible Tsunami’ caused by heavy Sumatra Andaman earthquake in December 2004, it can be said that no one in Malaysia care about earthquake. Majority of Malaysian citizen does not worry to earthquake hazard. However, after experienced several tremors in Sabah and Peninsular Malaysia due to earthquakes occurred in Philippines and Indonesia, the question about ability of buildings in Malaysia to withstand the tremors are rising up. This issue has become serious when several earthquakes had occurred in Bukit Tinggi, Pahang in 2007. Since hospital is the most important place during disaster to give humanitarian aid and medical treatment, it is important to make sure that the hospital building can withstand the earthquake. The objective of this study is to make comparisons of analysis and design of a 3-storey hospital building. Several cases of seismic loads had been applied to the building separately to represent the different intensity of earthquake between Malaysia and Indonesia. The results of analysis show that the same building can withstand any intensity of earthquake. It mean that the building are suitable to be built in any area located near the epicenter such as Indonesia, or at a distant from the epicenter like Malaysia. The comparison of design due to all cases showed that the design for building located near the epicenter need more steel reinforcement to resist the bending moment. Keywords: 3 Storey Hospital, Seismic Loads, STAADPRo Software. *Correspondence Author: Mr. Mohd Irwan Adiyanto, Universiti Sains, Malaysia. Tel: +60175316653, Fax: +6045996282. E-mail: [email protected]

http://www.uniten.edu.my/newhome/content_list.asp?contentid=4017

Analysis and Design of 3 Storey Hospital Structure Subjected To Seismic Load Using STAAD PRO.

378 ICCBT 2008 - C - (35) - pp377-388

1 INTRODUCTION Before the year of 2004, nobody concern about earthquake in Malaysia. This is because Malaysia was lucky to be located outside the earthquake region and logically, it will be no hazards for Malaysian due to the earthquake. However, after a great ‘Asian Disaster’ of tsunami on 26th December 2004 [1], followed by several earthquakes in 2005 until nowadays, the safety of buildings in Malaysia subjected to seismic loading had become an issue. The government, local authorities, structural engineers, architects, and other related professionals now start to discuss about the relevant of building with consideration of seismic load in Malaysia.

From 26th December 2004 until nowadays, so many earthquakes had occurred in South East Asia especially in Indonesia and Philippines. The tsunami disaster on December 2004 [1] was followed by tremor in Nias Island, Indonesia in March 2005 [2]. Then, the earthquake also occurred in Jogjakarta in May 2006 before the disaster was come again in September 2007 in Bengkulu. However, the epicenter of earthquakes was located outside Peninsular Malaysia and the tremors not give any effect to buildings in Malaysia. But, a small scale of tremor then was occurred in Bukit Tinggi, Malaysia in December 2007 [3]. Thus, a panic situation was happened to the residents of Bukit Tinggi due to the ‘unexpected’ disaster. On 28th March 2005, a heavy earthquake at 8.7 Richter scale was occurred in Nias Island [2], Indonesia (Figure 1). The tremor also was felt at several places in Peninsular Malaysia especially Penang and Kuala Lumpur. Although that earthquake did not cause any Tsunami wave, the shocking tragedy had killed more than 1000 people and caused damage to many buildings in Gunung Sitoli, Nias. This also happened to the Gunung Sitoli General Hospital which was also functioned as operation center to give medical treatment to the victims. In this paper, the main focus is to analyze the bending moment, shear force, and inter-storey drift of 3-storey hospital building due to different intensity of seismic load using STAAD Pro. Then, to design a selected beam of 3-storey hospital building due to different intensity of seismic load based on American Concrete Institute [4]. Finally, this paper had done the comparison of design and detailing for the selected beam due to different intensity of seismic load.

Figure 1: Location of Nias Island (Google Earth)

PENINSULAR MALAYSIA

NORTH SUMATRA

NIAS ISLAND

M. I. Adiyanto et. al.

ICCBT 2008 - C - (35) - pp377-388 379

2. METHOD AND BASIC THEORY This paper contains several steps in order to achieve its objectives. The important steps are simplification of floor plan, modeling using STAAD Pro software with different input of seismic intensity, analysis of bending moment, shear force, and inter-storey drift. Then, the design for a selected symmetrical beam had been done to compare the changes of steel reinforcement required and provided due to different intensity of seismic load. The dead loads and live loads are taken from BS6399:1997 [5] and seismic load will be determined by using UBC 1994 equivalent lateral force procedure [6]. 2.1 Determination of Seismic Load Intensity The determination of seismic load intensity is based on equivalent static force procedure in UBC 1994 [6]. Step 1: Determination of numerical coefficient, C:

C = 1.25 S / T2/3 (1) Step 2: Determination of total seismic weight of the structure, W:

∑=

=n

iXWW

1

(2)

Wx = WA + WB + WC +WD +Wequip (3)

Figure 2: Tributary weight for seismic load calculation (UBC94) Step 3: Determination of design base shear:

V = [Z I C / Rw] W (4)


380 ICCBT 2008 - C - (35) - pp377-388

Step 4: Distribution of lateral force:

∑=

+=n

iit FFV

1

(5)

( )∑=

−= N

iii

iiti

hw

hwFVF

1

(6)

2.2 Beam Design for Gravity Load The beam design for selected beam under consideration of gravity load only is based on Clause 3.4.4.4 in BS 8110: part 1:1997 [7]. Step 1: Area of steel reinforcement required:

2bdf

MKCU

= (7)

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ −+=

9.025.05.0 KdZ (8)

ZfMA

YS 95.0= (9)

Step 2: Checking for minimum and maximum reinforcement:

0.4100

13.0 <<bd

AS (10)

2.3 Beam Design for Seismic Load For case of combination between gravity and seismic load, the beam design is referred to special provisions for seismic design as mentioned in chapter 21, American Concrete Institute [4]. The steps of flexural reinforcement design are following several equations as shown below: Step 1: Area of steel reinforcement required:

djfMuAY

S φ= (11)

Step 2: Moment capacity checking:


ICCBT 2008 - C - (35) - pp377-388 381

WC

YS

bfFA

a'85.0

= (12)

⎟⎠⎞

⎜⎝⎛ −=

2adfAM YSp φφ (13)

Step 3: Checking for minimum and maximum reinforcement:

Y

WW

Y

CSovidedS f

dbdb

ff

AA200

,'3

minPr => (14)

dbA

W

S=ρ < 0.025 (15)

3. RESULT AND ANALYSIS In this paper, the observation about effect of different values of seismic load on bending moment has been done to a selected beam in z-direction. A three span beam labeled as member 575, 576, and 577 located at gridline F/1-F/6 has been chosen since the beam supports widest floor area among other beams in z-direction. So, the beam will support the highest distribution of dead load and live load compared to other beams in z-direction. Figure 3 shows the location of selected frame while Figure 4 shows the side elevation of selected frame.

Figure 3: Location of selected frame in z-direction


382 ICCBT 2008 - C - (35) - pp377-388

Figure 4: Side elevation of selected frame 3.1 Effect on Bending Moment for a Selected Beam in Z-Direction Due to Different Values of Seismic Load

Figure 5: Comparison of bending moment diagram for different intensity of seismic load

Figure 5 shows the comparison of bending moment diagram for different intensity of seismic load applied to the structure. The comparison showed clearly that the values of bending moment caused by high intensity of seismic load are highest compared to other intensities. Table 1 below shows the comparison for the percentage of different for maximum bending moment due to different intensity of seismic load. The changing of maximum bending moment due to high seismic load applied compared to action of gravity load only is very high up to 82.4 percent. The comparison of maximum moment then is presented graphically in Figure 6.

3.5

m

3.5

m

3.5

m

5 m 6 m 5 m

577576575

110 123 135 146 SEIS

MIC

LO

AD

(Z

-DIR

ECTI

ON

)

Ground level

-200

-100

0

100

200

300

400

500

0 5 10 15 20

Section of beam (m)

Bend

ing

mom

ent (

kN.m

)

Gravity load Low seismic loadMedium seismic load High seismic load

101 123 135 146


ICCBT 2008 - C - (35) - pp377-388 383

Table 1: Comparison of maximum bending moment value for selected

beam under various intensity of seismic load in Z-direction Type of loading Maximum moment (kN.m) Percentage of different (%)

Gravity load 205.160 0 Low seismic load 208.352 1.56 Medium seismic load 259.408 26.4 High seismic load 374.290 82.4

Figure 6: Comparison of maximum bending moment due to various type of loading.

3.2 Effect on Shear Force for a Selected Beam in Z-Direction Due to Different Values of Seismic Load

Figure 7: Shear force diagram for each type of loading

205.16 208.352

259.408

374.29

0

50

100

150

200

250

300

350

400

Type of loading

Max

imum

ben

ding

mom

ent

(kN

.m)

Gravity load Low seismic load Medium seismic load High seismic load

-300

-200

-100

0

100

200

300

0 5 10 15 20

Section of beam (m)

Shea

r fo

rce

(kN)

Gravity load Low seismic loadMedium seismic load High seismic load


384 ICCBT 2008 - C - (35) - pp377-388

Figure 7 shows the comparison of shear force diagram for different intensity of seismic load applied to the structure. The comparison showed clearly that the values of shear force caused by high intensity of seismic load are highest compared to other intensities. Table 2 below shows the comparison for the percentage of different for maximum shear force due to different intensity of seismic load. The changing of maximum shear force due to high seismic load applied compared to action of gravity load only is high up to 13.2 percent. The comparison of maximum shear then is presented graphically in Figure 8.

Table 2: Comparison of maximum shear force value for selected beam under various intensity of seismic load in Z-direction

Type of loading Maximum shear (kN) Percentage of different (%)

Gravity load 227.055 0 Low seismic load 230.656 1.59 Medium seismic load 240.236 5.81 High seismic load 257.056 13.2

Figure 8: Comparison of maximum shear force due to various type of loading. 3.3 Inter-storey Drift Index Checking Inter-storey drift is the lateral displacement of one level of a multi-storey structure relative to the lower level. According to Smith and Coull [8], the inter-storey drift index can be defined as:

Inter-storey drift index = maximum deflection at a particular storey (16)

Storey height In accordance with UBC 1997 code, for the building with fundamental period, T is less than 0.7 seconds, the inelastic drift are limited to a maximum 0.025 times the storey height. For a building with natural periods 0.7 seconds or greater, the limitation for inter-storey drift is

227.055230.656

240.236

257.056

210215220225230235240245250255260

Type of loading

Max

imum

she

ar fo

rce

(kN

)

Gravity load Low seismic load Medium seismic load High seismic load


ICCBT 2008 - C - (35) - pp377-388 385

0.020 times the storey height. Since the value of period, T in this study was 0.43 second, the limitation for inter-storey drift is 8.75 cm.

Table 3: Inter-storey drift in x-direction at particular storey under various seismic load values

Inter-storey drift at particular storey (cm) Gravity

load

Low seismic

load (x-

direction)

Medium seismic

load (x-

direction)

High seismic

load (x-

direction)

Level

1.0DL

+ 1.0LL

1.0DL +

1.0LL +

1.0ELZ

1.0DL +

1.0LL +

1.0ELZ

1.0DL +

1.0LL +

1.0ELZ

Inter-storey drift limit,

h/40 (cm)

3 0.0152 0.1954 0.4722 0.9144 8.75 2 0.0142 0.4844 1.2828 2.5612 8.75 1 0.0113 0.5967 1.5800 3.1534 8.75

Table 4: Inter-storey drift in z-direction at particular storey under various

seismic load values Inter-storey drift at particular storey (cm)

Gravity load

Low seismic

load (z-

direction)

Medium seismic

load (z-

direction)

High seismic

load (z-

direction)

Level

1.0DL

+ 1.0LL

1.0DL +

1.0LL +

1.0ELZ

1.0DL +

1.0LL +

1.0ELZ

1.0DL +

1.0LL +

1.0ELZ

Inter-storey drift limit, h/40 (cm)

3 0.0093 0.1944 0.5241 1.0515 8.75 2 0.0083 0.6989 1.8767 3.7619 8.75 1 0.0142 0.8766 2.3532 4.72 8.75

Table 3 and Table 4 represent the result for inter-storey drift at particular level in x-direction and z-direction respectively. For both table, the inter-storey drift at particular level due to action of different type of loading are not exceeding the inter-storey drift limit. This result mean that the horizontal movement of columns joint are below the limitation and acceptable for design purposes even for high seismic load. From Table 3 and Table 4, it can be observed that the inter-storey drift for each level are different due to type of loading applied. At the same level, the value of inter-storey drift is


386 ICCBT 2008 - C - (35) - pp377-388

increase start from gravity load, low seismic load, medium seismic load, and followed by the high seismic load. Since maximum displacement of each level cause by the action of high seismic load to the building, it is now the same result for inter-storey drift. Maximum value of inter-storey drift in x and z-direction is 3.1534 cm and 4.72 cm respectively. The maximum inter-storey drift was occurred at first level for all cases of seismic load and for both x and z direction. The inter-storey drift then decreased until the top level. So, the lateral displacement for both x and z direction at the roof level are smaller relative to the third level of the building. This is due to smaller value of seismic load act on roof joint compared to the lower joints for all cases of seismic load. 3.4 Comparison of a Beam Design Due to Different Type of Loading Applied. As well as the analysis for bending moment, the comparison on beam design also using the same beam. Hence, the value of bending moment as discussed before is used for design purposes. In this study, the comparison of beam design are based on three different section that are the exterior support, middle span, and interior support of the beam. The location of exterior support, middle span, and interior support are shown in Figure 9.

Figure 9: Location of exterior support, middle span, and interior support

The comparison of beam design in term of size of section and bending reinforcement are tabulated in Table 5. From that table, it can be observed clearly that the area of steel reinforcement required is increase directly with the value of maximum moment for exterior support, middle span, and interior support. The cross section area of steel required for high seismic load is the highest among all cases.

Interior support

Middle span

5m 6m 5m

110 123 135 146

Exterior support


ICCBT 2008 - C - (35) - pp377-388 387

From Table 5, the flexural reinforcements provided for interior support are highest compared to flexural reinforcement provided for exterior support and middle span of the beam. This is due to the value of bending moment are highest at interior support compared to other section for all cases of loading. However, the section of beam is remaining same for all cases by using 200 mm for width and 600 mm for height. The cross section areas of steel reinforcements provided are higher than required.

Table 5: Comparison of beam design due to different type of loading applied

Sect

ion

Design parameter

Gravity load

Low seismic

load

Medium seismic

load

High seismic

load

Size of section (mm2) 200 x 600 200 x 600 200 x 600 200 x 600 Maximum moment (kN.m)

39.757 88.889 187.238 344.752

Bending reinforcement 2Y12 2Y20 3Y20 4Y25 As required (mm2) 175 438.7 922.6 1690

Exte

rior s

uppo

rt (to

p re

inf)

As provided (mm2) 226 628 942 1964 Size of section (mm2) 200 x 600 200 x 600 200 x 600 200 x 600 Maximum moment (kN.m)

135.543 137.754 137.754 137.754

Bending reinforcement 4Y16 4Y16 4Y16 3Y20 As required (mm2) 637 677.42 677.42 677.42 M

iddl

e sp

an

(bot

tom

rein

f)

As provided (mm2) 804 804 804 942 Size of section (mm2) 200 x 600 200 x 600 200 x 600 200 x 600 Maximum moment (kN.m)

205.160 208.352 260.420 374.290

Bending reinforcement 4Y20 4Y20 3Y25 3Y25 + 2Y20

As required (mm2) 1060 1026 1277.4 1838.7 Inte

rior s

uppo

rt

(top

rein

f)

As provided (mm2) 1256 1256 1473 2101 5.0 CONCLUSION In this paper, it is observed that the values of seismic load in this study are higher where the coefficient for importance factor was taken as 1.25 for hospital building. So, the value of shear base, V is higher than residential buildings by 20 percent. Since the height of that hospital is just 10.5 meter, so the time period of loading, T is short and less than 7.0 second. Thus, the value of Ft is equal to zero. In this case, Ft was not applied at the top of the building. So, seismic loads act on roof level was less than the lower level. The value of bending moment at any reference points at the beam is differ due to different type of loading applied to the beam and joint. From the analysis, the value of bending


388 ICCBT 2008 - C - (35) - pp377-388

moment at all supports are increase from gravity load to low, medium, and high seismic load applied. For bending moment at each middle span of the beam, no dramatic change occurred due to different type of loading applied. However, no dramatic change for bending moment at any section of the beam due to low seismic load applied compared to gravity load only. From the analysis of shear force, it had been observed that the value of shear force in any reference points at the beam is differ due to different type of loading applied to the beam and joint. From the analysis, the value of shear forces at all supports are increase from gravity load to low, medium, and high seismic load applied. In can be concluded that higher load will produce higher bending moment and shear force. In term of inter-storey drift checking, the inter-storey drift limit for both x and z direction is 8.75 cm. At the same level, the value of inter-storey drift is increase start from gravity load, low seismic load, medium seismic load, and followed by the high seismic load. Maximum value of inter-storey drift in x and z-direction is 3.1534 cm and 4.72 cm respectively. Since the limit of inter-storey drift was not exceeded for all cases of loading, hence the low rise hospital building can withstand any type of seismic load. The beam design for all cases of loading are satisfy with 200 mm x 600 mm rectangular section. However, the cross sectional area of steel reinforcement required for bending are differ due to different type of loading. High seismic load requires the highest cross sectional area of steel reinforcement compared to other loads. Hence, the material costs to build the building near the epicenter are higher than in a distant location from epicenter. Acknowledgements The authors would like to thanks the School of Civil Engineering, Universiti Sains Malaysia (USM). REFERENCES [1]. Tsunami, 2004 Indian Ocean Earthquake,

available from: http://en.wikipedia.org/wiki/2004_tsunami [2]. Nias Earthquake, 2005 Sumatra Earthquake,

available from: http://en.wikipedia.org/wiki/2005_Sumatra_earthquake [3]. Malaysian Meteorological Services, Ministry of Science technology and Innovation,

available from: http://www.kjc.gov.my [4]. American Concrete Institute: Building code requirements for structural concrete (ACI

318-05) and commentary (ACI 318R-05). [5]. BS 6399: Part 1:1996: Loading for building, Part 1, Code of practice for dead and

imposed load. [6]. 1994 Uniform Building Code, Equivalent Lateral Force Procedure (Static Method) [7] BS 8110: Part 1: 1997. Structural use of concrete, Part 1. Code of practice for design and

construction. [8] Smith, B.S. and Coull, A. (1991). “Tall Building Structures: Analysis and Design”, John

Wiley & Sons, INC, Canada.

3 story hospital seismic loading

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