STRUCTURAL BEHAVIOUR OF STEEL FABRIC … · “STRUCTURAL BEHAVIOUR OF STEEL FABRIC REINFORCED CONCRETE WALL PANEL UNDER ECCENTRIC LOADING” ... substitution of normal rebar to steel

International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol:10 No: 04 48

“STRUCTURAL BEHAVIOUR OF STEEL FABRIC REINFORCED CONCRETE WALL PANEL UNDER ECCENTRIC LOADING”

Ir Ruzitah Supinyeh1 Ir Dr Siti Hawa Hamzah2

1M.Sc Civil Engr Student, Faculty of Civil Engineering, Universiti Teknologi MARA, 40450, Shah Alam, Malaysia. ([email protected]) 2 Professor, Faculty of Civil Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Malaysia ([email protected])

ABSTRACT

Recently reinforced concrete walls have gained greater acceptance from many countries in conjunction with the Industrialized Building System (IBS). Essentially, the system gives an advantage in reducing the dependency of foreign labour and a better investment in technologies, techniques and processes of construction. Steel fabric reinforced concrete wall panel has been used in Malaysia in the past few years and can still be considered as a new construction method. This type of wall may require sequential analysis in making an effective product that gives advantages in all aspects and gives better performance. This research involved laboratory experimental work and model by using a finite element computer program as comparison of the results. Laboratory works tested eight wall samples with size of 1.0m x 1.5m and 0.75m thick. (Length:Height:Width). The wall samples reinforced with double layer steel fabric size B7 and concrete Grade 30. The wall panel tested under axial load with the eccentric t/6 or 12.5mm of wall thickness. Variations of support condition include of t/6 with pinned or fixed imposed at the top and bottom of the wall panel. Experimental result shows due to eccentric loading that all of the wall panels failed in compression shear which the wall panels shown a single curvature pattern where it bends towards the rear side. There are no cracks seen on both front and rear surfaces of the wall panel unless it crushed at top and base of the wall. It is observed that the ultimate eccentric loads (Pult) of 991.45 kN and maximum deflection 9.67mm obtained from the experimental works. The computer analysis shows that the wall panel failed by compression. Higher stress concentration appears at the upper and bottom corner of the wall panel. The deflection obtained over by 18.3% compared with the experimental results. Comparison with the experimental and the computer analysis results were found in good agreement. Keyword: concrete wall panel, steel fabric, eccentric

1.0 INTRODUCTION

A changed in structural design from moment-resisting to flexible frames with stiff shear resisting elements has occurred in recent years. In Malaysia the changed starts in late 1990's when the Government Plan For Zero squatters in Kuala


Lumpur. As such steel tunnel formwork system or Tunnel form had been used in replacement of conventional sawn timber formwork. They are a number of generic forms of shear wall structure or Industrial Building System (IBS) named as Steel Tunnel Formwork System, Steel Shear Wall Climbing Formwork System and Steel Wall Panel System [1]. Shear wall offers efficient means of enclosing and utilizing space. Thinner walls reduce the cost of buildings as well as increase the net lettable space of a building. Shear wall did not require column and beam as structural members. It can act as column and could transfer load from roof to foundation. A combination of pile and raft foundation is practically and economical design when the shear wall floor started at ground floor. Shear wall building is commonly built to consist 10 to 35 storey. This is the most suitable construction method to build apartment units in several blocks and within limited time frame. The construction speed of the shear wall is normally controlled by the concreting and subsequent depropping of the floor slabs. Props should be left in place until the slab has achieved adequate strength to resist further propping and construction loads. Practically the thickness of wall is varies from 100mm to 225mm. Loads on wall are usually in plane axial loads and lateral load but often they could become accidental eccentric loads due to constructional imperfections also non uniform distribution of load on wall panel. As the thickness of the wall panel is small and the wall is a slender element thus the analysis of wall panel shall include the considerations of the stability. Steel fabric is widely used in reinforce shear wall. In the specification for steel welded fabric for the reinforcement of concrete according to Malaysia Standard MS 145:2001 (Second Edition), the steel strength is of grade 510 steel [2]. The substitution of normal rebar to steel fabric expedites faster installation and considerable costs saving.

1.1 EXPERIMENTAL PROGRAM

The experimental work involved testing of eight (8) wall panels with the specified material properties. The material used has been confirmed earlier by conducting cube and steel fabric strength tests. The structural performance of the wall panel such as the ultimate strength load, mode of failure and cracking pattern will be determined. Eight wall panels reinforced with double layer of steel fabric type B385 (B7) with a dimension of 75 mm thick (width) x 1000 mm long x 1500 mm high were prepared. For steel fabric type B7 the main and cross wire are 100mm and 200mm centre to centre spacing. The aspect ratio (h/L) is 1.5 and the slenderness ratio (h/t) is 20. The specification and dimension of the wall panel is shown in Figure 1.1 The wall panels were constructed using concrete Grade 30 Normal Ordinary Portland Cement (OPC) with a water cement ratio of 0.58. These wall panels were tested under compressive axial load with 12.5mm eccentricity. Testing were carried out with two main support variations; pinned ends (PPe) and pinned-fixed ends (PFe) also the variations of eccentric for top and bottom support conditions.


Figure 1.1 : Wall Panel and steel fabric reinforcement detail

According to BS 8110: Part 1: 1997 Clause 3.9.3.3 the eccentricity should be taken as not less than h/20 or 20 mm if less where h is the thickness of the wall [3]. In this research the eccentricity of tw/6 (12.5 mm) is used according to American Concrete Institute (ACI 318) [4]. Determination of structural behaviour includes mode of failure either buckling or crushing, deflected shape (curvature), stress-strain and load-displacement relationship. From the experimental work, graph of stress versus strain and load versus displacement are plotted and mode of failure, deflection profile and crack pattern would determine and will shown accordingly. This research is expected to provide clear understanding and knowledge of the structural behavior and carrying strength capacity of such system to both researchers, designers and contractors.

2.0 THEORETICAL ANALYSIS OF WALL PANEL

The maximum stress in the wall can be occurred when both the axial load and the moment are applied. Since the radius of gyration is defined as:

AIr /= (2-1)

where; I = moment of inertia and A = cross section area of wall The maximum stress can be written in a form called the secant formula as,

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛+=

EAP

rL

r

ecAP

2sec21maxσ (2-2)

where; σ max = Maximum elastic stress


e = Eccentricity of the load P c = Distance from neutral axis to the outer fiber

A = Cross-sectional area E = Modulus of elasticity r = Radius of gyration I = Moment of inertia h = Height of wall L = Length of wall 2.1.1 Design wall Panel using British Standard (BS 8110: 97 Part 1)

In British Concrete Standard (BS8110-97), there’s a section that deals with the design of plain concrete walls (Section 3.9.4) [3]. This section recommends that the design ultimate axial force in a plain concrete wall may be calculated on the assumption that the members transmitting forces on the walls are simply supported.

2.1.2 Determination of Design Ultimate Axial Force Using Simplified Method For the determination of design ultimate axial load per unit length, the equations prescribed for different types of concrete walls as follows:

( ) cuww fe2t3.0n −≤ … (2-3)

Where nw is the ultimate axial load per unit length of a wall in compression and fcu is the characteristic compressive cube strength for concrete in Mpa. For slender braced plain concrete walls:

cuaxw feehn )22.1(3.0 −−≤ … (2.4)

where: ex is the resultant eccentricity of load at right angles to the plane of the wall

(with minimum value h/20). ea is the additional eccentricity due to deflections which may be taken

as le2/2500h where le is the effective height of the wall.

or unbraced plain walls: ( ) cu1,xww fe2t3.0n −≤ … (2.5)

and ( ) cu2,xww fe2t3.0n −≤ … (2.6)

Where ex,1 and ex,2 are the resultant eccentricity calculated at the top and bottom of the wall respectively.

2.1.3 Effective Height The effective height of unbraced plain concrete walls is given as follows: a. wall supporting at its top a roof or floor slab spanning at right angles;

le =1.5lo;

b. other walls le=2 lo

lo, may be measured mid-way between eaves and ridge The effective heights of braced plain concrete walls are:


a) where an lateral support resist both rotational and lateral movements at both ends and le = 0.75L; and for any lateral support resists both rotational and lateral movements at one end and the other is free is le = 2.0L.

b) for any lateral support resist only lateral movements at both ends, le = Lo; and for any lateral support resists only lateral movement at one end and the other end is free is le = 2.5Lo.

L is the horizontal distance between centres of lateral restraints and Lo is clear height of wall between lateral supports.

2.1.4 Alternative to Design Equation British Standard outlines an alternative procedure for the design of reinforced concrete walls in Section 3. The code calculates the failure load using the following formula; yscccuw fA67.0Af35.0n +≤ … (2.7)

If the wall is not subjected to a significant moment, due to the nature of the structure and the arrangement of the structural elements, the above equation is increased to: yscccuw fAAfn 75.04.0 +≤ … (2.8)

where; cuf = characteristic strength of concrete cA = gross area of concrete at a cross section scA = area of compression reinforcement, per unit length of wall yf = characteristic strength of compression reinforcement For this alternative design method to be valid, the slenderness ratio of the wall must satisfy: a) for braced walls: le /h ≤ 40, or le /h ≤ 45 if vertical reinforcement exceeds 1% b) for unbraced walls: le /h ≤ 40 The slenderness effects can be ignored for short walls. Reinforcement are defined as short if the height-to-thickness ratios are:

a) le /h ≤ 15 for braced walls b) le /h ≤ 10 for unbraced walls

However, nw is the total design axial load on the wall due to design ultimate loads. The walls are designed for a uniformly distributed imposed load and the span on either side of the wall does not differ by more than 15%.

2.1 GAP OF RESEARCH

The review of literature of the previous researcher gave better understanding about wall panel behaviour and proposed parameter in the study area to be confirmed or revised. The mode of failure for the wall panel were depends on types of material used, structure behaviour and application of loadings. It is important to understanding the behaviour of wall panel reinforced with steel


fabric wire mesh with eccentric loading. The use of steel fabric wire mesh in the wall construction required attention due to misconceptions or cost factor. The strength of wall panel depends on the percentage of steel in concrete and concrete grade used. This study is sought to investigate the performance of wall using double layer of steel fabric as normal practice in Malaysia.

3.0 SPECIFICATION OF WALL PANEL

The experimental work is conducted based on structural behaviour of steel fabric reinforced concrete wall panel under eccentric loading. The loads will be applied at t/6 from the centre of wall panel. A total number of eight (8) samples of steel fabric reinforced concrete wall panel were prepared. The specified characteristic strength of the concrete wall panels is 30 N/mm2 with identical dimension of 75mm thick, 1000mm length and 1500mm height. The aspect ratio (h/L) and slenderness ratio (h/w) of the wall panel are 1.5 and 20 respectively, whereas it is classified as normal wall. This wall panel was subjected to an axial load with an eccentricity of tw/6 on both top and bottom. The eccentricity specified as by code (BS8110 Part 1:, 1997) is not to be less than t/6 or 20mm [3]. The eccentricity for this experiment is 12.5mm from the cross section of the centroidal axis. The wall sample design and used properties as stated in BS 8110 Clause 3.9.3.

Table 3.1: Samples specification

Samples No

Set Up No

Eccentricity Condition

PPe 1 Set up 1 et = t/6

PPe 2 Set up 2 eb=et = t/6 FPe 1&2 Set up 3 et= eb =t/6 PFe 1&2 Set up 4 eb= et =t/6

PP-e Set up 5 eb=-et =t/6 PF-e Set up 6 eb=-et = t/6

Table 3.1 shows the specification of eight wall samples which tested at different end-condition at both end. Samples PPe1 and PPe with end condition pinned on top and bottom. Sample FPe with end condition fixed on top and pinned at the bottom while samples PFe is a reverse of FPe. Samples PP-e with end condition pinned top and bottom but the eccentric load is on top reversed position than at the bottom. Sample PF-e with end condition pinned on top and fixed at bottom and then the eccentric load was imposed at reverse position at the bottom. Figure 3.2 shows six different types of experimental set-up and end condition. Set-up 1 shows the axial load on top with eccentric of 12.5mm from the centre of wall. Set-up 2, 3 and 4 show the axial load on top and bottom with eccentric of 12.mm imposed at the same site position top and bottom. Set up 5 and 6 shows the axial load on top with eccentric 12.5mm and at the bottom the eccentric is at the reverse side.


Figure 3.2: Support set up condition


3.1 CONSTRUCTION OF WALL PANEL

A total of eight (8) samples wire fabric reinforced concrete wall panel of formwork or mould were prepared. The formwork is designed and built accurately to the desired shape, size, verticality and horizontally. Plywood with thickness 10mm and timber 75mm x 50mm were used as formwork. The formwork prepared in horizontal form due to the difficulty in compact the concrete during casting of concrete. The work was fabricated at Fabrication Laboratory of the Civil Engineering Faculty [4]. A total eight numbers of concrete wall panels reinforced with double layer of wire mesh type B 385 (B7) with a dimension of 75x1000x1500mm (Width: Length: Height) were cast at Concrete Laboratory of Civil Engineering Faculty [4,5]. The concrete wall panels were constructed using specified material properties that have been confirmed earlier by conducting cube and fabric test.

3.2 EXPERIMENTAL SET UP

Reaction frame together with double hydraulic actuator were used to test wall panel under eccentricity loading. The wall was anchored to a strong floor and two samples have been tested in vertical position. Figure 3.4 shows the reaction frame together with load cell and double actuator which will imposed vertical loading to wall panel. Figure 3.5 shows the experimental set-up of wall panel clamped to reaction frame.

Figure 3.4: Reaction frame used to test wall panel


Figure 3.5: Experimental Set-up

The concrete wall panel was placed on the center of reaction frame accurately. The wall has been painted in white color to ensure the crack pattern could be observed easily. It was supported by one hydraulic jack with a 2000 kN capacity. The jacks was transmitted a vertical axial load at the top of the wall in order to achieve the pinned support at both ends (top and bottom) of this wall. The boundary condition was set up using circular rod. The circular rod and the steel plate acted in transferring the load to the wall panel. Its have been located with eccentricity of tw/6 on both top and bottom of wall panel. In this experiment, strain gauges placed at steel fabric to measure the strain of the wall panels under axial load. The strain gauges were placed at proper location and mounted on cleaned and smooth surface of the wall panel. For each wall panel, four strain gauges were used two at the front longitudinal bar and two at the rear longitudinal bar as shown in Figure 3.6. When using strain gauge, it is very important to make sure that the bond between the gauge and the reinforcement is tight glue and sealed with electric tape. Beside strain gauge, linear variable differential transformer (LVDT) also were used to measure small movements or deformations of the wall panel. The schematic arrangement of the LVDT is shown in the Figure 3.7. The instruments were calibrated and adjusted properly, before applying the load. Then the load was applied gradually increased until the


wall fail and no more load can be applied. All dimension of width and lengths crack of crack were measured and necessary data were recorded automatically by Data Logger which connected to the computer. The crack pattern was also marked with marker for at each load stage. Cracks were marked on the surface of the sample indicating the corresponding load. At each load increment, deflection has been recorded. Figure 3.8 shows the detail location of wall panel, load cell. LVDT and end condition of the supports. Load cell was attached to 2000kN hydraulic jack for incremental of applied load.

Figure 3.6: Arrangement of strain gauge on reinforcement of steel fabric


T5

T4

T3

T2

T1

Figure 3.7: Arrangement of LVDT

Figure 3.8: Detail test set-up in the laboratory


3.3 TESTING PROCEDURE

The experiment work was to complied with all the specification of material used as stated in the current code of practice. The testing procedure and set up for the material and were also loading followed the procedure used in actual works. The main test set up for the panel testing were the actual experiment with limitation of the reaction frame. The lever arm attach to the machine were not contacted directly to the wall panel. It was acted as a support to prevent the panel from sway and prevent damage the LVDT. The panel were casted in horizontal position because it is difficult to prepare the formwork vertically and compacting of concrete will be very easy. An incremental of applied load of 10% to wall panel under vertical loading could easily measure the crack pattern and lateral displacement. Five LVDT were measured lateral displacement at different height of wall.

4.0 EXPERIMENTAL RESULTS The structural behaviour of the panels was observed during experimental work by measuring the lateral deflections at the location of LVDT and deformation of strain gauges at the reinforcement bars. In order to have better understanding the performance of each panel, the test results were analyzed in the context of eccentric load bearing capacity, profile - displacement, load - displacement profile, stress – strain, cracking pattern and mode of failure. According to American Concrete Institute (ACI 318), the ultimate load obtained from the formula for pinned top and bottom is 528.41 kN. The ACI formula for pinned on top and fixed on the bottom or otherwise is 649.69 kN. Meanwhile, British Standard BS 8110: Part 1: 1997 in Clause 3.9.4.16, the design ultimate load, nw is 324.0 kN for pinned on top and bottom of wall. For the pinned on top and fixed on bottom or otherwise the design ultimate load, nw is 355.05 kN. From these values, it was found out that the ultimate load for PPe1 and PPe2 recorded from experiment is lower than the proposed equation likes in ACI 318 and BS8110 27.28% and 196.59%, respectively. The FPe samples accounted less between 27.28% and above 30.44%, from the theoretical values. Sample PFe1 experienced the higher value between 33.07% and 63.42% but sample PFe2 has lower up to 196.59%. Similarity results obtained for sample PP-e and PPe2 in the range of lower 192.37% and upper 67.32%. Also for sample PF-e shown similarity with sample PFe2 of lower 196.59% and upper 1.75%. According to BS 8110: Part 1: 1997 Clause 3.9.4.16 the value of nw 324.0 and 355.05 kN is the maximum design ultimate axial load for slender braced plain wall, where reinforcement is neglected. An alternative design method is to use Clause 3.8.4.3 value nw 1047.26 kN with limitation of wall assume as column design and without significant moments. In America Standard ACI 318 the empirical design formula allowed for a minimum reinforcement contents. Steel reinforcement improved the strength of the wall 30% higher ultimate load than theoretical value.


Table 4.1 compared the experimental and theoretical results of ultimate load with eccentricity of tw/6. The experimental results have lower value than the theoretical values. It is meaning to say that the codes either ACI or BS 8110 have a upper limit band than the experimental value. Therefore, the strength capacity of shear wall with double layer has lower value than as specified in both standards. Further investigation and improvement should be made to improve their strength so that the actual ultimate value must higher than the codes. Figure 4.1 shows ultimate load for each samples from the experimental, theoretical and maximum deflection. Maximum deflection measured from the experiment have lower value than the theoretical.

Table 4.1: Experimental and theoretical results SAMPLE EXPERIMENTAL

ULTIMATE LOAD (kN)

BASIC REQUIRED BY CODE OF PRACTICE

BS8110 & ACI (kN)

PERCENTAGE%

PPe 1 382.12 ACI 318 = 528.41 BS 8110 Cl. 3.9.4.16 = 324.00 BS 8110 Cl. 3.8.4.3 = 1047.26

-38.28 15.20

-174.07 PPe 2 358.20 ACI 318 = 528.41

BS 8110 Cl. 3.9.4.16 = 324.00 BS 8110 Cl. 3.8.4.3 = 1047.26

-47.52 9.55

-192.37 FPe 1 362.03 ACI 318 = 649.69

BS 8110 Cl. 3.9.4.16 = 355.05 BS 8110 Cl. 3.8.4.3 = 1047.26

-79.46 1.93

-189.27 FPe 2 510.46 ACI 318 = 649.69

BS 8110 Cl. 3.9.4.16 = 355.05 BS 8110 Cl. 3.8.4.3 = 1047.26

-27.28 30.44

-105.16 PFe 1 970.70 ACI 318 = 649.69

BS 8110 Cl. 3.9.4.16 = 355.05 BS 8110 Cl. 3.8.4.3 = 1047.26

33.07 63.42 -7.89

PFe 2 353.10 ACI 318 = 649.69 BS 8110 Cl. 3.9.4.16 = 355.05 BS 8110 Cl. 3.8.4.3 = 1047.26

-84.00 -0.55

-196.59 PP-e 991.45 ACI 318 = 528.41

BS 8110 Cl. 3.9.4.16 = 324.00 BS 8110 Cl. 3.8.4.3 = 1047.26

46.79 67.32 -5.63

PF-e 361.36 ACI 318 = 649.7 BS 8110 Cl. 3.9.4.16 = 355.05 BS 8110 Cl. 3.8.4.3 = 1047.26

-79.79 1.746

-189.81


ULTIMATE LOAD VS DISPLACEMENT

0

100

200

300

400

500

600

700

800

900

1000

1100

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Displacement (mm)

Load

(kN

)

BS8110-1PP

BS8110 -1PF

BS8110-2

PFe1

PFe2

PPe1

PPe2

FPe1

FPe2

PP-e

PF-e

Note: BS8110-1 is BS 8110 Cl. 3.9.4.16 = 324.0kN for pinned-pinned

BS8110-1 is BS 8110 Cl. 3.9.4.16 = 355.05kN for pinned-fixed BS8110 -2 is BS 8110 Cl. 3.8.4.3 = 1047.26kN

Figure 4.1: Experimental and Theoretical

4.1 DEFLECTION PROFILE The measurement of deflection was taken at every 10 kN load increment. The relationships between transducers reading with respect to the applied load were plotted as shown in Figure 4.2. The maximum lateral displacement for PPe samples is located at mid height of wall samples, i.e. 750 mm from the base end. Meanwhile, for PFe samples it occurred at 1050 mm (0.7L) from the base of wall panel. Detailed readings recorded in all samples are shown in Table 4.2.


Table 4.2: Deflection profile summary

Note : Highlighted value is the highest magnitude of displacement

All samples showed a single curvature prevailing buckling behaviour with maximum deflection dominated at positions agreeing with the support conditions as mentioned in Euler buckling theory. The deflection profile and failure pattern for both PPe and PFe is agreeable and supported by Wang et. al. (1997) who indicated that wall tested under action of eccentric load top and bottom of wall deflected with single curvature [6]. Figure 4.4 has shows the deflection profile of wall panel at different height and end conditions of support.

WALL PROFILE VS DEFLECTION for ALL SAMPLES EXPERIMENT

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0 1 2 3 4 5 6 7 8 9 10 11

Displacement (mm)

Hei

ght (

mm

)

PPe1PPe2FPe1FPe2PFe1PFe2PP-ePF-e

Figure 4.2: Deflection profile

Sample PPe1 PPe2 FPe1 FPe2 PFe1 PFe2 PP-e PF-e

Load 382.12kN 358.2kN 362.03kN 510.46kN 970.70kN 353.10kN 991.45kN 361.36kN

P P P P P P P P P P P P P P P P

initial ultimate initial ultimate initial ultimate initial ultimate initial ultimate initial ultimate initial ultimate initial ultimate

Dis

plac

emen

t

T1 0.04 0.57 0.04 1.14 0.07 0.26 0.04 1.75 0.37 0.63 0.04 3.09 0.00 2.12 0.78 0.56

T2 0.29 2.25 0.63 2.35 0.07 0.72 0.07 2.31 0.22 9.67 0.65 2.83 0.11 6.50 0.58 0.33

T3 0.35 2.45 0.75 2.75 0.07 2.02 0.11 3.27 0.22 9.21 0.11 1.77 0.07 5.21 0.33 0.33

T4 0.37 1.47 0.30 1.78 0.04 2.99 0.19 5.39 0.07 7.76 1.35 3.05 0.04 5.39 0.19 0.15

T5 0.11 0.93 0.05 1.23 0.04 1.74 0.04 4.99 0.07 4.86 0.04 1.58 0.22 2.17 0.18 0.98


4.2 CRACK PATTERNS PPe and PFe sampleswere not crack on the surfaces of the wall panels based on visual observations absent. However, the wall panel crushed at the upper and lower ends of the samples (see Figure 4.3 to 4.5) after yielding of the reinforcement had occured. The crushed sections at the base showed complete load distribution took place within the concrete matrix. Even though all samples were designed with capping of the steel fabric layers at both upper and lower ends, the crushed ends showed compression failure of the concrete initiated the failure of the wall panels. The details for crack pattern for all walls are shown in Table 4.3 Based on the visual observation most of spalling of concrete and cracks were occur at bottom and top of wall panel.

Table 4.3: Description of and location of cracks at 8 samples

SAMPLE CRACK LOCATION SIDE CRACK SURFACE CRACK

PPe1 Crush at top and base of the wall None None

PPe2 Crush at top and base of the wall

Crush on left edge at the base of the wall None

FPe1 Crush at bottom of the wall None None

FPe2 Crush at bottom of the wall None None

PFe1 Crush at top of the wall Crush at left and right edges of the wall None

PFe2 Crush at top of the wall Crush at left and right edges of the wall None

PP-e Crush at top and base of the wall None None

PF-e Crush at top and base of the wall None None

Figure 4.3 : PPe1 crushing at both end


(a) (b) (c)

Figure 4.4 : PFe1 crushing at both ends

Figure 4.5 (a) : PFe2 crushing at base end

4.3 STRESS STRAIN RELATIONSHIP Figure 4.6 shows stress-strain relationships for wall panel samples PFe1, PPe1 and FPe1. In the Table 4.4 shows strain gauge reading on the steel fabric and the stress calculation using secant formula. All strain in the longitudinal bars increased linearly with respect to the applied load onto the wall.

Stress vs Strain for PFe1

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

26000

0 200 400 600 800 1000Strain (um/m)

Stre

ss (k

N/m

2 )

F1R1F2R2

Stress vs Strain for PPe1

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

0 50 100 150 200 250 300 350 400Strain (um/m)

Stre

ss (k

N/m

2 )

F1F2R2R1

Stress vs Strain for FPe1

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 50 100 150 200 250 300 350 400

Strain (um/m)

Stre

ss (k

N/m

2 )

F1F2R1R2

Figure 4.8 : Stress and strain relationship


Table 4.4: Measurement on steel fabric

Sample Maximum

Stress (kN/m2)

Strain Longitudinal wire

(µm)

Remark

PPe1 10 189.87

L F 1050 = 0.261 L R 1050 = 0.372 L F 750 = 0.368 LR 750 = 0.313

Maximum stress at middle of

wall height

PPe2 9 553.07

L F 1050 =0.290 L R 1050 =0.273 L F 750 = 0.288

LR 750 = DAMAGE

Maximum stress at middle of

wall height

FPe1 9 654.13

L F 1050 = 0.344 L R 1050 = 0.242 L F 750 = 0.279 LR 750 = 0.201

Maximum stress at

three quarter of wall height

FPe2 13 612.27

L F 1050 = 0.084 L R 1050 = 0.103 L F 750 = 0.130 L R 750 = 0.212

Maximum stress at three quarter bottom of wall

height

PFe1 24 343.73

L F 1050 = 1.240 L R 1050 = 1.280 L F 750 = 0.99 L R 750 = 1.00

Maximum stress at three quarter of wall height

PFe2 9 416.00

L F 1050 = 0.074 L R 1050 = 0.177 L F 750 = 0.013 LR 750 = 0.056

Maximum stress at three quarter of wall height

PP-e 26 438.67

L F 1050 = 0.891 L R 1050 = 0.054 L F 750 = 0.699 LR 750 = 0.924

Maximum stress at three quarter bottom and top of

wall height

PF-e 9 636.27

L F 1050 = 0.145 L R 1050 = 0.034 L F 750 = 0.116 LR 750 = 0.239

Maximum stress at three quarter bottom of wall

height

Samples PPe1 and PPe2 experienced strain of the range between 0.261 to 0.372, whereby the PFe samples experienced in the range of 0.013 to 1.280. Both types of samples shows similarity in which the PPe samples have and average of 5 % different between the front to the rear surface at height of 750 mm and 1050 mm respectively. The maximum stress for PPe1 and PPe2 are 10,189.87 kN/m2 and 9,553.07 kN/m2 respectively. Samples FPe1 and FPe2 show different stress behaviour at the top and bottom in the range of 0.344 and 0.212 respectively with the average 38% different. Sample PP-e experienced maximum stress at rear face on the bottom and front face on top due to symmetrical eccentricity. The maximum stress for sample PP-e is 26,438.67 kN/m2 and the support condition is stable. The same experienced to be shown by sample PF-e but the support


condition not stable compare with sample PP-e the maximum stress is 9 636.27 kN/m2 about the average of the sample PF-e, PPe2, FPe1 and PFe2 is 9564.86 kN/m2. From theoretical analysis the maximum stress value is 14, 437 kN/m2. It is about 33% and 83% difference between average and the higher. Graph of stress versus strain of steel fabric at different location shown for all samples in the Appendix F.

4.4 NUMERICAL ANALYSIS RESULTS

4.4.1 Height versus displacement

The numerical analysis using PROKON software were model for sample with the support condition top pinned and bottom fixed (PFe) subject to eccentricity loading of t/6 [7]. The model was run with 3D linear analysis. The maximum displacement is measured at the centre of wall or middle node as per experiment where the location of LVDT location. The maximum displacement of 11.72mm for load case DL18 or 1000kN were satisfied the code of practice (BS 8110 part 1 1997: Clause 3.9.3.8.2). The maximum displacement sample PFe1 is 14% different. The summary of maximum displacement is shown in Table 4.5 and Figure 4.9 shows the wall profile versus displacement indicated the maximum displacement occurred at 0.7 height of wall. Figure 4.10 show the displacement for load case DL10.

Table 4.5: Displacement summary

Wall LOAD CASE DL1 DL5 DL10 DL12 DL14 DL15 DL17 DL18 DL19

Height LOAD kN 10 50 100 300 500 600 800 900 1000

(mm) Node no. Displacement (mm)

0 10 0 0 0 0 0 0 0 0 0 100 21 0 0.02 0.04 0.11 0.18 0.21 0.28 0.32 0.35 200 32 0.01 0.06 0.13 0.39 0.64 0.77 1.03 1.16 1.26 300 43 0.03 0.13 0.26 0.79 1.32 1.59 2.12 2.38 2.59 400 54 0.04 0.21 0.43 1.29 2.15 2.57 3.43 3.86 4.2 500 65 0.06 0.3 0.61 1.82 3.04 3.64 4.8 5.46 5.95 600 76 0.08 0.39 0.78 2.35 3.92 4.71 6.27 7.06 7.69 700 87 0.09 0.47 0.95 2.84 4.73 5.68 7.57 8.52 9.27 800 98 0.11 0.54 1.08 3.24 5.39 6.47 8.63 9.74 10.57 900 109 0.12 0.58 1.17 3.5 5.8 7 9.33 10.5 11.43

1000 120 0.12 0.6 1.2 3.59 6 7.18 9.57 10.77 11.72 1100 131 0.1 0.58 1.15 3.46 5.79 6.92 9.23 10.32 11.31 1200 142 0.08 0.515 1.03 3.08 5.15 6.15 8.26 9.23 10.05 1300 153 0.05 0.4 0.8 2.39 4 4.78 6.38 7.21 7.81 1400 164 0 0.23 0.46 1.38 2.31 2.75 3.67 4.15 4.5 1500 175 0 0 0 0 0 0 0 0 0


Wall Profile vs Displacement for NUMERICAL ANALYSIS

PFe

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Displacement (mm)

Hei

ght (

mm

) DL1DL5DL10DL12DL14DL15DL17DL19DL18DL19Max

Max deflection at 0.7 w all height or at 1050 mm

Figure 4.9: Plot graph load versus displacement using PROKON load case DL1 to DL19

Figure 4.10: Displacement profile for load case DL10


4.4.2 Stress Versus Load The stress criterion is as Von Misses Stress is concentration at the support and edge of the wall panel. The experiment has shown this criteria whereby the sample crushed at top and bottom support. The maximum stress is much higher than the experiment. Figure 4.11 show the linear relationship between stress and load. Figure 4.12 show maximum stress for load case DL10.

STRESS vs LOAD for NUMERICAL ANALYSIS

PFe

0

15000

30000

45000

60000

75000

90000

105000

120000

135000

150000

0 100 200 300 400 500 600 700 800 900 1000 1100Load (kN)

Stre

ss (k

N/m

2) DL1DL5DL10DL12DL14DL15DL17DL18DL19

Figure 4.11: Graph for numerical analysis on stress and different load cases


Figure 4.12: Stress for load case DL10



5.0 CONCLUSION The experiment results showed that the behaviour of the steel fabric wire mesh reinforced concrete wall panel have similar behaviour and characteristic as specified in BS 8110 and ACI 318. The average ultimate load for eight samples of wall panels are 536.18 kN. By comparing with theoretical results from ACI 318, BS 8110 Cl. 3.8.4.3 and BS 8110 Cl. 3.9.4.16 the ultimate load record from the experimental were less 84%, 192.37% and more 67.32%, respectively. Therefore, the average strength capacity of shear wall is less than what is specified in both of code of practice (ACI and BS 8110). The deflection profile showed a single curvature pattern where it bends at rear side. The maximum lateral displacement ranges is about 9.67 mm and 2.75 mm which occurred at distance 1050 mm (0.7H) and at 750 mm (0.5H) from the base of the wall for sample PFe and PPe respectively. It was proved that the theoretical studies of buckling by Euler with maximum deflection should occur at center of the wall about 750 mm (0.5H) for pinned ends support. Whereby, the maximum stress calculated using secant formula has an average maximum stress record from the experiment is 14105.50 kN/m2 less than theoretical calculation of 2.3%. The strain increased linearly with the stress, the strain recorded found to be very small and below the yield strain. The steel fabric wire mesh B7 with two layers indicated that the reinforcement is more adequate. Beside that, there is no cracking occurrence on surface of wall panel but the wall panel crushed at top and base of the wall. Beayoune et all (2005), showed that when the load reached the ultimate value a violent failure occurred by crushing at either one or both of the panels [8]. Therefore, it can be conclude that, the objective of this study has been achieved where the structural behaviour of wire fabric reinforced concrete wall panel under eccentric loading has been observed such as mode of failure, crack propagation and deflection profiles as discussed. The experimental works have proved the theory with some limitation on the test set up and sample properties. Since the wire fabric reinforced concrete wall panel is a new trend in the construction in our country, this understanding could provide sustainable development in promoting fast and economic construction in the future.

5.1 RECOMMENDATION

There are some recommendations that will be useful to get a better understanding on behaviour of the steel fabric wire mesh reinforced concrete wall panel under eccentric loading. i. The one way action or the direct axial load with eccentric has predicted

average agreement with the theory. ii. For future experiment on the same topic it is recommended to look on

the different percentage of steel fabric in the wall panel and slenderness ratio.

iii. The numerical analysis of different software such as PROKON, ETAB, STAAD PRO and LUSAS can be used as the numerical analysis.


iv. Study on the actual constructed wall panel building could be more

valuable inventory to predict and confirmed the safety of the building. v. It is recommended that higher reinforcement ratio 1.27% or maximum 4%

of the section area as in column design to be used in shear wall. Double layer of steel fabric wire is advisable to use in the construction of multi-storey building.

vi. Lateral cyclic loading test experiment to be conducted for shear wall to

determine the wall strength subjected to horizontal loading such as earthquake and wind loading.

REFERENCES [1] Tunnel Formwork System (2007), Transkon Engineering Sdn Bhd (Brochure).(n.d) Kuala Lumpur. [2] SIRIM, (2001) MS 145 Specification for Steel Fabric for the Reinforcement of Concrete, Shah Alam, SIRIM Berhad. [3] British Standards Association (1997), BS 8110: Part 1. Structural Use of Concrete, British Standard Institution [4] American Concrete Institute (1989), ACI 318 Building Code Requirement for Reinforced Concrete, USA [4] Hamzah, S.H., Saari, N., Hamzah, A.H. and Marwi, M.S., (2005), Understanding Reinforced Concrete Through Experiment, UPENA UiTM, ISBN 967-968-185-3, Shah Alam [5] Hamzah, S.H., Kamarul Zaman, S.B., and Rajin, F., (2007), Wire Fabric Reinforced Concrete Wall Panel, World Housing Congress, Terengganu [6] Wang, R., Elwi A.E, Hatzinikolas, M.A and Warwawuk, J., (1995) Tests on

Tall Cavity Wall Subjected to Eccentric Loading”, the Seventh Canadian Mansory Symposium, June 5-7, 1995 Hamilton Ontario, Proceedings Vol 2, pp. 911-922

[7] PROKON (2008), PROKON Calculation Pad design software Version W2.4.00. [8] Benayoune, A., Samad, A.A.A., Trikha, D.N., Ali, A.A.A. and Ashrabor, A.A., (2005), Structural behaviour of eccentrically loaded precast sandwich panels, Construction and Building Materials, 20, 713-724

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