Performance Assessment of Some Reinforced Concrete ...cjbas.com/archive/CJBAS-13-01-02-03.pdf · element modeling (FEM) by Yang et al. [5]. In that study Yang et al. [5] basically

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Performance Assessment of Some Reinforced Concrete Buildings under Construction: The

Case of North Cyprus

Hakan Yalciner1,

, Khaled H. Marar2

1 Erzincan University, Department of Civil Engineering, Erzincan, TURKEY

2 European University of Lefke, Department of Civil Engineering, Lefke, Mersin 10, TURKEY

Keywords: Abstract

Construction faults;

linear performance

analyses;

honeycombing;

corrosion

The main objective of this study was to assess and identify general construction faults

and to investigate the effects of construction faults on the linear performance levels of

reinforced concrete buildings. For doing this, observed two common construction faults

(i.e., corrosion and honeycombing) were considered to be used in linear performance

analyses. Finite element method was used to model the honeycombing at the column-

beam joints. The effects of corrosion on the performance levels were ensured by

reducing the cross-sectional area of reinforcement bars and reduced concrete

compressive strength as a function of corrosion rate. Thus, two different construction

faults on the levels of structural performance were discussed and compared. The results

showed that the effects of honeycombing on performance levels of reinforced concrete

building with linear performance analyses was more dramatic when it was compared

with the results of damage building due to corrosion having a moderate to high

corrosion threshold.

1. Introduction

On September 1985, a major earthquake with magnitude 8.1 on the Richter scale occurred along the

Pacific coast of Mexico which caused extensive destruction and over 10,000 deaths in Mexico City

were recorded. Another major earthquake was occurred in Turkey, on August 17th

and the other one

on November 12th

, 1999 with magnitudes of 7.4 and 7.2 on Richter scale, respectively. According

to official reports this earthquake caused deaths of about 15,000 people and collapsed of 133,683

buildings [1]. Each earthquake consequences were due to not considering lessons learned. In this

study thirty existing reinforced concrete (RC) buildings were assessed and common problems

identified from the randomly selected constructions in the city of Gazimagusa in North Cyprus.

Observed two common construction faults (i.e., corrosion and honeycombing) were used to perform

linear performance analyses. Previous study done by Yalciner et al. [2] performed nonlinear time-

history analyses for 20 ground motion records to investigate the three different (the loss of the cross

sectional area of the reinforcement bars, the reduction of the concrete compressive strength and the

bond–slip relationship) effects of corrosion on seismic performance levels. Developed time-

Corresponding Author (Email: [email protected]

CJBAS Vol. (01) - September - Issue 02 (2013) 77-87

Hakan Yalciner and Khaled H. Marar CJBAS Vol. (01)-September – Issue 02 (2013) 77-87

78

dependent corrosion model by Yalciner et al.

[2] showed that there were strong

relationships between the reinforcement slip

due to corrosion in concrete and the roof drift

ratio of the RC buildings. In contrast to

previous study done by Yalciner et al. [2], in

this study particularly two effects of corrosion

(the loss of the cross sectional area of the

reinforcement bars, the reduction of the

concrete compressive strength) were taken

into account to perform linear performance

analyses. The reduction in the concrete

compressive strength due to corrosion was

calculated by using developed expression by

Yalciner et al. [2], as given Eq. 1 below.

ef

2

α)/)(1(

α)//()1(

)(4

bars0E

tbfπ

abcνbacν

tsdπnb

fb

(1)

Where bf is the width increased by corrosion

cracking, b0 is the section width in the virgin

state, nbars is the number of the bars in the top

layer (compressed bars), ft is the tensile

strength of concrete, νc is the Poisson’s ratio

of concrete and Eef is the effective elastic

modulus of concrete. In Equation 1, a and b

were explained by the developed thick wall

model by Bažant [3]. It should be noted, in

this study linear performance analysis was

performed based on the developed model by

Sucuoglu [4], thus slippage of reinforcement

where bond strength is a function of corrosion

rate was not taken into account. The effects of

honeycombing at the column-beam joints

were modeled based on the developed finite

element modeling (FEM) by Yang et al. [5].

In that study Yang et al. [5] basically used the

developed micropolar elasticity theory by

Eringen [6].

2. Assessment of reinforced concrete

buildings under construction

This stage involves the general construction

faults from the selected RC buildings under

construction. The assessed buildings were

located in Gazimagusa city and the distance

of the buildings from the Mediterranean sea

was approximately 1 Km which affects the

level of corrosion potential of the existing

buildings. Figure 1 shows the assessed one of

the RC buildings.

Figure 1. An under construction RC

building

Figure 2. Honeycombing at columns.

The common and observed construction faults

were mainly honeycombing at column-beam

joints. Formation of honeycombing generally

depends on pouring, compacting of concrete

and particularly vibration time. The time of

the vibration plays an important role during


79

placing of concrete. If the time of the

vibration exceeds more than required, the

coarse aggregates settle down and fine

aggregates rise up which affects the mix

design of the concrete. In this study, each

floor of the existing buildings under

construction had honeycombing problems

which reduces the required strength of

column design as it shown in Figure 2. More

than half of the column-beam joint regions

had honeycombing problems which also

decreases the maximum shear force that a

joint can resist. Honeycombing also causes

corrosion of reinforcement as it is shown in

Figure 3. Because of corrosion the

performance level of structures decreases with

time due to different effects. These effects

could be a reduction in the cross sectional

area of the reinforcement bars, internal cracks

in structural members, reduction in the

concrete strength, additional lateral

displacement due to slipping and cracking of

the concrete cover due to the expansion of

corrosion products [2].

Figure 3. Sign of corrosion

Figure 4. An under construction RC

building.

Figure 4 shows the another assessed RC

building from Gazimagusa. For the assessed

building again more than half of the column-

beam joint regions (see Figure 7) had

honeycombing problems. Another mainly

faced construction faults was cold joint

problems (see Figure 6). The general reason

of this problem has been occurred due to the

wrong application and inadequate formworks.

As it can be seen from Figure 6, the upper end

of the column has the same color of the beam

which represents that the concrete was not

placed at the same time for the related

column. These cold joints are the reasons to

decrease the maximum shear force that the

joint can resist during earthquakes.

Figure 5. Sign of honeycombing [7].


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Figure 6. Cold joints at column- beam

regions.

For the assessed building in Figure 4, another

common investigated problem was again

corrosion as shown in Figure 7. The main

reason of corrosion was to not use adequate

cover materials. Beside of buildings which

were under construction, twenty existing RC

buildings were also assessed and common

construction faults were identified. Figures 8-

10 illustrate some cracks that occurred on the

surface of the columns due to corrosion which

might be due to the reason of using

inadequate cover material during the

construction process.

Figure 7. Sign of corrosion.

Figure 8. Inadequate cover materials.

Figure 9. Sign of corrosion.

Figure 10. Cracked concrete due to

corrosion.

As shown in Figure 10, spalling of concrete

occurred due to volumetric expansion by

corrosion. As a consequence of volumetric

expansion, the concrete strength decreases as

a function of crack width, where the loss of

ductility of the columns is inevitable under

seismic loading [2].


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3. Linear performance assessment of a

RC building

In this stage linear performance assessment

was performed based on the described

procedure by Sucuoglu [4]. Sucuoglu [4]

defined the damaged limits of structural

members with their damage states. Sucuoglu

[4] stated that if the demand to capacity ratio

at a potentially yielding frame member end or

a masonry infill strut exceeds the demand to

capacity ratio limit specified for a

performance limit state, then that member

performance is declared unacceptable.

Otherwise it is acceptable [4]. Table 1 below

shows the defined limit states based on the

demand to capacity ratio (r). In Table 1, N is

the axial force calculated under simultaneous

action of vertical loads, Ac is the gross

sectional area of column, fc is the compressive

strength of concrete, fct is the tensile strength

of concrete, Ve is the shear force taken into

account for the calculation of transverse

reinforcement of column, bw is the width of

beam web, and d is the effective beam height.

In the method of Sucuoglu [4], four

performance levels (i.e, immediate

occupancy, life safety, collapse prevention

and collapse) were defined based on their

damage limits. In the study of Sucuoglu [4],

immediate occupancy (IO) performance level

was defined when not more than 10% of

beams are in the significant damage state

whereas all other structural members are in

the minimum damage state. Life safety (LS)

performance level was defined when not more

than 20% of beams and some columns are in

the extreme damage state whereas all other

structural members are in the minimum or

significant damage states. Collapse prevention

(CP) performance level was defined when not

more than 20% of beams and some columns

are in the collapsed state whereas all other

structural members are in the minimum,

significant or extreme damage states.

Collapse performance level was defined when

the building fails to satisfy any performance

levels of IO, LS and CP.

Table 1. Demand/capacity ratios for reinforced concrete columns (r) [4]

Ductile Columns Damage Limit

cfCA

N

Confinement ctw

e

dfb

V

Minimum

damage limit

Safety

damage limit

Collapse

damage limit

≤0.1 Conforming ≤0.65 3 6 8

≤0.1 Conforming ≥1.30 2.5 5 6

≥0.4 Conforming ≤0.65 2 4 6

≥0.4 Conforming ≥1.30 2 3 5

≤0.1 Non Conforming ≤0.65 2 3.5 5

≤0.1 Non Conforming ≥1.30 1.5 2.5 3.5

≥0.4 Non Conforming ≤0.65 1.5 2 3

≥0.4 Non Conforming ≥1.30 1 1.5 2

Brittle Columns 1 1 1

4. Results of modeled RC building under

the effects of corrosion and

honeycombing

In this study an existing RC building was

remodeled. The remodeled RC building is

shown in Figure 11. The remodeled building

was a randomly selected dormitory building

having a four story. Existing static drawings

were used for the remodeling of RC building.

For the structural assessment, building


82

importance factor (I) was taken as 1.4,

building behaviour factor was taken as 7,

effective ground acceleration coefficient was

taken as 0.3g according to the TEQ 2007 [8].

The soil used in this study was sampled from

the existing building from the depth of 4.5 m

under the ground. The physical properties of

this soil were summarized in Table 2. Soil

type was classified as soil D according to the

unified soil classification system (USCS). The

two effects of construction faults,

honeycombing and corrosion of

reinforcement bars were applied and

performed, respectively by using finite

element method. Figure 12 and 13 show the

application of honeycombing at the column-

beam joints, respectively based on the

developed FEM by Yang et al. [5]. The

results of linear performance analyses of an

existing building (undamaged) based on

applied four different earthquake loads from

the selected columns are given in Table 3.

Tables 4 and 5 give the results of linear

performance analyses of damage building due

to honeycombing and corrosion, respectively.

Table 2. Physical properties of soil for existing building

Soil characteristics Soil D

Insitu dry density(gr /cm3) 1.32

Liquid limit, LL (%) 53.22

Insitu water content (%) 22.27

Plastic limit, PL (%) 21.4

Shrinkage limit, SL (%) 14.78

Plasticity index, PI 28.37

Percentage of clay (%) 55

Specific gravity of solids 2.43

Percentage of silt (%) 28

Percentage of sand (%) 3

Optimum water content (%) 26

Maximum dry density(gr/cm3)

1.42

Figure 11. Modelling of a RC building.


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Figure 12. FEM for honeycombing at the middle point of a column.

Table 3. Existing building - Demand/capacity ratios for reinforced concrete columns (r)

Column Load N/Acfc Ve/bwdfct r MN GV GC Damage Damage

reason

S11M

+EX 0.07 0.46 0.45 3 6 8 Minimum -

-EX 0.07 0.46 0.45 3 6 8 Minimum -

+EY 0.06 0.08 0.43 3 6 8 Minimum -

-EY 0.06 0.07 0.43 3 6 8 Minimum -

S11A

+EX 0.09 0.41 0.50 3 6 8 Minimum -

-EX 0.09 0.41 0.50 3 6 8 Minimum -

+EY 0.10 0.04 0.62 2.98 5.98 7.97 Minimum -

-EY 0.10 0.04 0.62 2.98 5.98 7.97 Minimum -

S11E

+EX 0.07 0.47 0.33 3 6 8 Minimum -

-EX 0.07 0.47 0.33 3 6 8 Minimum -

+EY 0.06 0.38 0.98 3 6 8 Minimum -

-EY 0.06 0.38 0.98 3 6 8 Minimum -

S11G

+EX 0.07 0.42 0.30 3 6 8 Minimum -

-EX 0.07 0.42 0.30 3 6 8 Minimum -

+EY 0.04 0.35 1.14 3 6 8 Minimum -

-EY 0.04 0.35 1.15 3 6 8 Minimum -

S11I

+EX 0.04 0.33 0.19 3 6 8 Minimum -

-EX 0.04 0.33 0.19 3 6 8 Minimum -

+EY 0.03 0.33 1.31 3 6 8 Minimum -

-EY 0.03 0.33 1.31 3 6 8 Minimum -

*MN: Minimum damage limit, GV: Safety damage limit, GC: Collapse limit.

Honeycombing Honeycombing


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Figure 13. FEM for honeycombing at the column-beam joints.

Table 4. Damaged building (Honey combing) - Demand/capacity ratios for reinforced

concrete columns (r)

Column Load N/Acfc Ve/bwdfct r MN GV GC Damage Damage

reason

S11M

+EX 1.72 0.37 1.27 1 1 1 Collapse r > 1

-EX 1.72 0.37 1.27 1 1 1 Collapse r > 1

+EY 1.68 0.08 1.01 1 1 1 Collapse r > 1

-EY 1.68 0.10 1.01 1 1 1 Collapse r > 1

S11A

+EX 2.02 0.21 1.52 1 1 1 Collapse r > 1

-EX 1.98 0.21 1.56 1 1 1 Collapse r > 1

+EY 1.83 0.10 2.09 1 1 1 Collapse r > 1

-EY 1.83 0.10 2.04 1 1 1 Collapse r > 1

S11E

+EX 1.75 0.17 1.54 1 1 1 Collapse r > 1

-EX 1.72 0.17 1.58 1 1 1 Collapse r > 1

+EY 1.13 0.20 2.73 1 1 1 Collapse r > 1

-EY 1.13 0.20 2.82 1 1 1 Collapse r > 1

S11G

+EX 1.75 0.15 1.36 1 1 1 Collapse r > 1

-EX 1.70 0.15 1.42 1 1 1 Collapse r > 1

+EY 0.87 0.19 3.11 1 1 1 Collapse r > 1

-EY 0.87 0.19 3.19 1 1 1 Collapse r > 1

S11I

+EX 1.34 0.14 0.66 1 1 1 Minimum r > 1

-EX 1.34 0.14 0.66 1 1 1 Minimum r > 1

+EY 0.76 0.18 3.36 1 1 1 Collapse r > 1

-EY 0.76 0.18 3.40 1 1 1 Collapse r > 1

Honeycombing


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Table 5. Damaged building (Corrosion) - Demand/capacity ratios for reinforced concrete

columns (r)

Column Load N/Acfc Ve/bwdfct r MN GV GC Damage Damage reason

S11M

+EX 0.08 0.51 0.002 27.12 0.46 3 8 Minimum

-EX 0.08 0.51 0.002 0.46 3 8 Minimum

+EY 0.07 0.09 0.006 4.47 0.44 3 8 Minimum

-EY 0.07 0.08 0.006 0.44 3 8 Minimum

S11A

+EX 0.11 0.45 0.003 16.03 0.50 2.97 7.94 Minimum

-EX 0.11 0.45 0.003 0.50 2.97 7.94 Minimum

+EY 0.13 0.04 0.004 1.44 0.62 2.91 7.83 Minimum

-EY 0.13 0.04 0.004 0.62 2.91 7.83 Minimum

S11C

+EX 0.06 0.36 0.004 35.86 0.29 3 8 Minimum

-EX 0.06 0.36 0.004 0.29 3 8 Minimum

+EY 0.04 0.35 0.006 76.76 0.99 3 8 Minimum

-EY 0.04 035 0.006 0.99 3 8 Minimum

S11E

+EX 0.09 0.52 0.003 40.64 0.34 3 8 Minimum

-EX 0.09 0.52 0.003 0.34 3 8 Minimum

+EY 0.07 0.39 0.006 70.42 1.02 3 8 Minimum

-EY 0.07 0.39 0.006 1.03 3 8 Minimum

S11G

+EX 0.09 0.46 0.003 36.01 0.31 3 8 Minimum

-EX 0.09 0.46 0.003 0.31 3 8 Minimum

+EY 0.04 0.37 0.006 65.91 1.19 3 8 Minimum

-EY 0.04 0.37 0.006 1.20 3 8 Minimum

S11I

+EX 0.05 0.37 0.003 29.10 0.19 3 8 Minimum

-EX 0.05 0.38 0.003 0.19 3 8 Minimum

+EY 0.03 0.35 0.006 73.59 1.36 3 8 Minimum

-EY 0.03 0.35 0.006 1.36 3 8 Minimum

S11J

+EX 0.13 0.37 0.003 29.17 0.30 2.90 7.79 Minimum

-EX 0.13 0.37 0.003 0.30 2.90 7.79 Minimum

+EY 0.11 0.29 0.008 22.87 0.31 2.98 7.96 Minimum

-EY 0.11 0.30 0.008 0.31 2.98 7.96 Minimum

S12G

+EX 0.16 0.24 0.003 8.94 0.44 2.80 7.61 Minimum

-EX 0.16 0.23 0.003 0.44 2.80 7.61 Minimum

+EY 0.08 0.08 0.005 2.82 0.82 3 8 Minimum

-EY 0.08 0.07 0.005 0.82 3 8 Minimum

S12I

+EX 0.10 0.01 0.001 0.33 0.34 3 8 Minimum

-EX 0.10 0.01 0.001 0.34 3 8 Minimum

+EY 0.05 0.35 0.006 23.95 1.37 3 8 Minimum

-EY 0.05 0.35 0.006 1.34 3 8 Minimum

S12A

+EX 0.05 0.25 0.003 7.76 0.85 3 8 Minimum

-EX 0.05 0.25 0.003 0.85 3 8 Minimum

+EY 0.06 0.16 0.006 5.03 0.43 3 8 Minimum

-EY 0.06 0.16 0.006 0.43 3 8 Minimum

The result of linear performance analyses

showed that if the assessed building was

constructed based on the expected

construction design standards, the linear

performance analyses of building were

immediate occupancy where the

demand/capacity ratios of reinforced concrete

columns were minimized as given in Table 2.


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However, the performance level of the

assessed building due to honeycombing was

collapse as given in Table 4. As shown in

Table 4, the demand/capacity ratios of

reinforced concrete columns were greater one.

Because of honeycombing where the capacity

of shear force particularly transverse

reinforcement of the column was reduced due

to honeycombing. Developed FEM by Yang

et al. [5] was based on the negative Poisson’s

ratio for the modelling of honeycombing.

Thus, honeycombing directly effected the

capacity of columns gained by the

compressive strength of concrete. The results

of linear performance level of the assessed

building due to corrosion was more optimistic

when it was compared with the damage

building due to honeycombing. It should be

noted that in this study, moderate to high (0.5-

1 µA/cm2) thresholds of corrosion was

assumed based on the given limits by Song

and Saraswathy [9]. The performance level of

damaged building due to corrosion was life

safety based on linear performance analyses.

Of course, different corrosion rates would

give different performance levels, but this was

not a case for the present study. In Table 5,

the damage limits for the selected columns

were minimum. In the case of corroded RC

building, only 6 columns out of 280 columns

have evident damage limits where not more

than 20% of beams and some columns were

in the extreme damage state.

5. Conclusions

In this study main construction faults were

shared from existing RC buildings to be

useful in research literature. General

construction faults were modeled by using

FEM methods. Demand/capacity ratios for

reinforced concrete columns were compared

based on the damage occurred due to

honeycombing and corrosion. The results

clearly indicated that the performance level of

the assessed building was more affected due

to honeycombing when it was compared with

the building damage due to corrosion within

the moderate corrosion level. It should be

noted that this study was based on linear

performance analysis. Therefore, further

studies are also required by considering

plastic hinge deformation by using non-linear

analyses. Thus, modified moment-curvature

relationships might provide to take into

account the slippage of reinforcement bars in

the case of corroded RC structures.

References

[1] GESS Reconnaissance Team 1999, The

November 12, 1999, Turkey, Earthquake,

Preliminary Reports of the Turkey–U.S.

Geotechnical Earthquake Engineering

Reconnaissance Team,

(http://gees.usc.edu/GEES/RecentEQ/Turk

eyDuzce/Reports /Tunnel/tunnel.htm), Jan.

22, (2008).

[2] Yalciner H., Sensoy S., Eren O.: Time-

dependent seismic performance assessment

of a single-degree-of-freedom frame

subject to corrosion. Engineering Failure

Analysis, 19, 109-122 (2012).

DOI: 10.1016/j.engfailanal.2011.09.010

[3] Bazant Z. P.: Physical model for steel

corrosion in concrete sea structures--

application. Journal of the structural

division, 105, (1979).

[4] Sucuoglu H.: The Turkish seismic

rehabilitation code. in Proceeding of the

First European Conference on Earthquake

Engineering and Seismology. Geneva,

Switzerland, Joint Event of the 13th

European Conference on Earthquake

Engineering & the 30th General Assembly

of the European Seismological

Commission, 318 (2006).

http://gees.usc.edu/GEES/RecentEQ/TurkeyDuzce/Reports%20/Tunnel/tunnel.htm

http://gees.usc.edu/GEES/RecentEQ/TurkeyDuzce/Reports%20/Tunnel/tunnel.htm


87

[5] Yang D. U., Lee S., Huang F. Y.:

Geometric effects on micropolar elastic

honeycomb structure with negative

Poisson's ratio using the finite element

method. Finite Elements in Analysis and

Design, 39, 187-205 (2003).

DOI: 10.1016/S0168-874X(02)00066-5

[6] Eringen A. C., Suhubi E. S.: Nonlinear

theory of simple micro-elastic solids—I.

International Journal of Engineering

Science, 2, 189-203 (1964).

DOI: 10.1016/0020-7225(64)90004-7

[7] Yalciner H., Yardimci T., “Jacketing of

column-beam joints: A case study of an

existing RC building in TRNC”, Creating

the furture 5th ARCHENG-2008

international architecture and engineering

symposiums, 27-28 November, 81-86

(2008).

[8] Ministry of Public Works and Settlement,

Government of Republic of Turkey,

Specifications for Structures to be Built in

Disaster Areas – Earthquake Disaster

Prevention, 35-38 (2007).

[9] Song H.-W., Saraswathy V.: Corrosion

Monitoring of Reinforced Concrete

Structures-A Review. International Journal

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Documents

Performance Assessment of Some Reinforced Concrete ...cjbas.com/archive/CJBAS-13-01-02-03.pdf · element modeling (FEM) by Yang et al. [5]. In that study Yang et al. [5] basically