UNIVERSITY OF NAIROBI
DEPARTMENT OF CIVIL AND CONSTRUCTION ENGINEERING
FCE 531: ADVANCED STRUCTURAL DESIGN
SEISMIC ANALYSIS OF STRUCTURES
MAY 2019
Group V
NAME
REGISTRATION NO.
BILLY KOECH KIPCHRCHIR
F16/1636/2015
DAVIES MUTIA MUTUA
F16/1635/2015
TIMOTHY MULI KIMUYA
F16/35258/2014
PATIENCE MWIKALI MUTUA
F16/1619/2015
DENNIS MBURU NG’ANG’A
F16/31494/2015
EDWINA ACHIENG ODHIAMBO
F16/35104/2014
CHRIS KINYANJUI KAMAU
F16/35157/2014
LEON K TERIGIN
F16/37910/2016
CHAMIA CHRIS CHAMIA
F16/1639/2015
DAVID MULI MASWILI
F16/53893/2012
SIGNATURE
EXERCISE 2
Every county in Kenya plans to put up a 20 storey reinforced concrete (or steel) structure within
a town of its choice. The building will be used by the local tertiary education institutions for
academic and administrative purposes. The plan dimensions of the proposed building is
approximately 50 metres in length and 40 metres wide. The external façade of the building will
be covered with 6mm thick glass mounted on aluminum framing. The typical floors will have
hollow blocks partitioning. The building will have two basement parkings and apart from the
ground floor that will be 4.0 metres high, all other floors will be 3.0 metres high. There will be
100,000 litres capacity water storage tank positioned in the lower basement. Other water tanks
with total capacity of 30,000 litres will be positioned on the roof level. The site of the building
will be level and the foundation will be on firm ground. Using the traditional Kenya earthquake
code, estimate the horizontal force resisting capacity of the building at the specified towns. Work
out the horizontal load distribution at each level including the roof. State any assumptions made.
SOLUTION
i)
What is the Seismic Zone for the town?
According to the Kenya Earthquake Code, the seismic zone for Karatina Town is Zone VII, this
earthquake intensity is characterized by negligible damage to buildings of good design and
construction; slight to moderate damage to well-built ordinary structures; considerable damage
to poorly built or badly designed structures; some chimneys are broken.
ii)
What is the building classification by usage and value?
The building is to be used for academic and administrative purposes and therefore it is classified
as a Class A (Buildings for Public Assembly and Use) building by usage and value.
iii)
What is the building classification by type of structure?
The building is to be a reinforced concrete frame structure. The frame is to be a rigid frame, that
is, vertical forces are transmitted to the ground by columns and walls, and horizontal forces by
shear walls or by direct forces on bracing. Therefore classification by type of structure is Framed
Buildings; Rigid Frame.
iv)
Comment on the shape of the building.
The plan of the building is rectangular in shape with length to width ratio of (50/40) 1.25 which
is less than 3 and therefore its configuration is sufficiently uniform and compact.
v)
Estimate the real weight of the building.
The calculations below resulted to a weight W = Total Dead Weight =289504KN
vi)
Which coefficients are applicable for the structure?
The coefficient that was used to obtain the total horizontal force from Table 2 for rigid frame
with 20 storeys on hard ground was 0.020.
vii)
Estimate the horizontal load capacity at each floor level
Calculations for load capacities at each level are shown below.
UNIVERSITY OF NAIROBI
DEPARTMENT OF CIVIL &
DESIGNED BY:
STRUCTURAL ENGINEERING GROUP 5
CALCULATIONS
REFERENCE
DATE:
30/05/2019
ELEMENT LOADINGS
Slab sizing
BS 81101;1997, T 3.14
& T 3.15
+ concrete cover +
Dmin =
=
.
= 137.36 +30+8=175.36mm
Assume slab thickness is 200mm.
Density of concrete = 24KN/m3
Slab Loading
BS 648;1964
BS 6262; T16
Self-weight: 0.2m x 24KN/m3 = 4.8KN/m2
Finishes:
0.05m x 24KN/m3 = 1.2KN/m2
Façade Loading
Density of glass = 25KN/m3
Thickness of glass = 6mm
Self-weight: 0.006mx 25KN/m3 = 0.15KN/m2
Internal Walls
BS 648;1964
Wall thickness = 200mm
Density of clay hollow blocks = 25.9Kg/m3 per 25.4mm
Self- weight: 0.2m x 203.94Kg/m3 = 0.41KN/m2
Plaster thickness: 0.024m x 24KN/m3 = 0.576 KN/m2
Total wall loading = 0.986 KN/m2
Lift walls
Wall thickness=200mm
Self-weight= 0.2m x 24KN/m3=4.8KN/m2
∅
UNIVERSITY OF
NAIROBI
DEPARTMENT OF CIVIL &
DESIGNED BY:
STRUCTURAL ENGINEERING GROUP 5
CALCULATIONS
REFERENCE
Level
Roof
DATE:
30/05/2019
Calculation
Load (KN)
Total (KN)
Slab
Finishes
Tank
4.8 x ( 50 x40)
1.2 x (50 x 40)
30,000ltrs x 10/1000
9600
2400
300
12300
Slab
Finishes
Façade
Internal
Walls
Lift walls
4.8x (50 x40)
1.2 x(50 x40)
0.15 x (2 x (40+50) x3)
9600
2400
81
272m x 3 x 0.986
804.6
{(10 +4) x 2} x 2x 3 x 4.8
806.4
Slab
Finishes
Façade
Internal
Walls
Lift walls
4.8x (50 x40)
1.2 x(50 x40)
0.15 x ( 2 x (40 +50) x 4)
9600
2400
108
272m x 4 x0.986
1072.8
{(10 +4) x 2} x 2x 4 x 4.8
1075.2
Slab
Finishes
Shear
Wall
4.8x (50 x40)
1.2 x(50 x40)
9600
2400
3 x 0.2 x (2 x(50+40)) x 24
2592
4.8x (50 x40)
1.2 x(50 x40)
9600
2400
3 x 0.2 x (2 x(50+40)) x 24
2592
100,000ltrs x10/1000
Total Dead Weight
1000
Level 1-17
13692
Ground floor
14256
Basement 1
14592
Basement 2
Slab
Finishes
Shear
Wall
Tank
15592
289504
UNIVERSITY OF
DEPARTMENT OF CIVIL &
DESIGNED BY:
NAIROBI
STRUCTURAL ENGINEERING GROUP 5
REFERENCE
CALCULATIONS
Kenya
Earthquake TOTAL HORIZONTAL FORCE
Code 1973; Coefficient C
Table 2
Rigid Frame of 20 Storeys in Zone VII on Hard Ground = 0.020
Pg 15&16
DATE:
30/05/2019
Horizontal Forces
F= C x W
where C = coefficient from Table 2
W = dead weight of building plus partitions and walls
F = 0.020 x289504= 5790KN
Distribution of Total Force F
Portion attributed to the roof;
Pg 19
2
𝑓𝑡 = 0.004𝐹
where;
hn = height of uppermost storey above base
Ds = plan dimension of the lateral structural system resisting the
earthquake forces at ground floor level
Ft = 0.004 x 5790 x
2 = 215.45KN
The remaining force is distributed between stories as follows;
𝑓𝑥 =
(𝐹 − 𝑓𝑡)𝑥 𝑤𝑥 𝑥 ℎ𝑥
∑ 𝑤𝑖 𝑥 ℎ𝑖
where;
wx = proportion of load w apportioned to storey x
hx = height of storey x above base
wi = proportion of load w apportioned to storey i
hi = height of storey i above base
UNIVERSITY OF NAIROBI
REFERENCE
DEPARTMENT OF CIVIL &
DESIGNED BY: GROUP 5
STRUCTURAL ENGINEERING
CALCULATIONS
DATE:
30/05/2019
DISTRIBUTION OF LOAD PER FLOOR
Level
wx
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Ground floor
Basement 1
Basement 2
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
15600
16800
14592
15592
hx
58
55
52
49
46
43
40
37
34
31
28
25
22
19
16
13
10
6
3
0
wx*hx
𝐰𝐱 ∗ 𝐡𝐱
∑𝐧𝟏 𝐰𝐢 ∗ 𝐡𝐢
F-ft
Fx
904800
858000
811200
764400
717600
670800
624000
577200
530400
483600
436800
390000
343200
296400
249600
202800
156000
100800
43776
0
0.098762
0.093654
0.088546
0.083437
0.078329
0.07322
0.068112
0.063004
0.057895
0.052787
0.047678
0.04257
0.037462
0.032353
0.027245
0.022136
0.017028
0.011003
0.004778
0
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
5574.55
6321
550.5563
522.0792
493.6022
465.1251
436.6481
408.171
379.694
351.2169
322.7399
294.2628
265.7858
237.3087
208.8317
180.3546
151.8776
123.4005
94.92349
61.33518
26.63699
0
∑𝒏𝟏 𝒘𝒊𝒉𝒊 9161376
0
