Description of the specimens
The specimen is described in Section 3.1. During the testing phase a big washer and a nut were added at the outer side of the masonry part of the specimen to prevent pull-out and ensure pure shear loading.
Figure 44 – Dimensions of complete concrete-floor-to-wall connection specimens (concrete blocks connected to CaSi masonry couplets)
Test set-up
The test apparatus is presented in Figure 45Figure 15, and comprehends:
i. Supports for the specimen. The support system consists of four horizontal steel plates (5) and eight steel bolts M24 (6). Each couple of steel plates is placed at the top and bottom of each part of the specimen (one couple for the masonry part and one couple for the concrete part) and with the help of the steel rods the concrete part is fixed and the masonry part is clamped to the load cell. For the masonry part, hardwood bearers are placed at the top and bottom to leave space for the concrete part to move vertically without reaching the steel plates. Teflon sheets are placed between the wooden pieces and the steel plates in order for the couplet to be able to move horizontally and compensate for the reduction of the 22 mm distance between the masonry and the concrete block as the two parts move relatively in the vertical direction. The hardwood bearers do not apply any restraint against splitting of the specimen (apart from the friction generated at the reaction due to the applied load, as suggested by EN 846-5:2012 [4]). A temporary support is placed under the bottom horizontal plate of the couplet to keep the complete specimen aligned until the bottom plate is sufficiently bolted to the top plate. Then the support is removed.
ii. A test machine to apply the vertical load. The shear load acts in a vertical direction using displacement controlled apparatus. The apparatus is composed by a 4.5 tons jack and a double cylindrical joint (between the load cell and the clamp), which reduce possible eccentricities and prevent torsion failures of the threaded bar during loading. The top horizontal plate of the masonry part is screwed to the load-cell to vertically displace the couplet.
Version 01 – Final 30/06/2017 Figure 45 – Set-up for shear testing of complete concrete-floor-to-wall connection specimens (concrete
blocks connected to CaSi masonry couplets)
Loading scheme
There are two directions in which the shear loading can be applied: horizontal (parallel to the mortar) and vertical (perpendicular to the mortar).
Horizontal shear
For horizontal shear, only monotonic tests were performed as the absence of lateral restriction led to separation of the masonry part of the specimen and cyclic loading would not give useful results because of the movement of the threaded bar inside the broken mortar. Note that this configuration may not be completely realistic in a building, where the couplets are subject to confining forces provided by the surrounding structure.
The shear behavior of the specimens is determined by monotonically increasing the displacement with a rate of 0.1 mm/s up to failure.
Vertical shear
When performing tests of vertical shear loading the masonry part of the specimen is not allowed to open as it is restricted between the two horizontal steel plates. Three different loading schemes are followed:
Protocol V0 (monotonic shear protocol): The shear behaviour of the specimens is determined by monotonically increasing the displacement with a rate of 0.1 mm/s up to failure.
Protocol V1 (cyclic shear protocol – small number of cycles for each amplitude): The displacement is cyclically varied by applying both upward and downward (shear) loads on the tie, as depicted in
Figure 46.
Protocol V2 (cyclic shear protocol – large number of cycles for each amplitude): The displacement is cyclically varied by applying both upward and downward (shear) loads on the tie, as depicted in Figure 47.
The last protocol was introduced in order to investigated the influence of the number of cycles on the force-displacement behavior of the specimens.
Version 01 – Final 30/06/2017 Figure 46 – Cyclic protocol V1.
Figure 47 – Cyclic protocol V2.
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Experimental results on TUD_ANC-CHz-i specimens (complete connection – horizontal shear loading)
Monotonic tests (TUD_ANC-CH0)
During the monotonic horizontal shear loading of the complete specimens the masonry part separated due to lack of lateral restriction. Therefore, only two tests were performed. Bending of the threaded bar, cracking of the mortar and separation of the specimens were observed.
Figure 48 – Failure for monotonic horizontal shear loading of concrete-floor-to-wall connections.
Figure 49, Figure 50 and Table 19 report the force-displacement curves for each single performed test and a summary of the results.
Figure 49 – Force displacement curve for monotonic horizontal shear loading of concrete-floor-to-wall connections.
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Figure 50 – Summary of the “Force-Displacement curves” for monotonic horizontal shear loading of concrete-floor-to-wall connections.
Table 19 – Summary of results for monotonic horizontal shear loading of concrete-floor-to-wall connections.
Specimen Peak force [kN] Displacement [mm]
TUD_ANC-CH0-12 1.43 43.64
TUD_ANC-CH0-13 1.32 60.09
Average 1.37 51.87
Standard deviation 0.07 11.63
Coefficient of variation 5.4% 22.4%
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
0 10 20 30 40 50 60 70
Shear force (kN)
Displacement (mm)
TUD_ANC-CH0-12 TUD_ANC-CH0-13 Average
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Experimental results on TUD_ANC-CVz-i specimens (complete connection – vertical shear loading)
Monotonic tests (TUD_ANC-CV0)
When the specimens are loaded in shear perpendicular to the mortar joints, the mortar cracks and fails, and the threaded bar bends. The tests were performed up to the couplet touching the concrete block.
Figure 51 – Failure for monotonic vertical shear loading of concrete-floor-to-wall connections.
Figure 52, Figure 53 and Table 20 report the force-displacement curves for each single performed test and a summary of the results.
0
Version 01 – Final 30/06/2017 Figure 52 – Force displacement curve for monotonic vertical shear loading of concrete-floor-to-wall
connections.
Figure 53 – Summary of the “Force-Displacement curves” for monotonic vertical shear loading of concrete-floor-to-wall connections.
Table 20 – Summary of results for monotonic vertical shear loading of concrete-floor-to-wall connections.
Specimen Peak vertical force [kN] Displacement [mm]
TUD_ANC-CV0-01 5.65 58.53*
TUD_ANC-CV0-06 5.18 60.20*
TUD_ANC-CV0-07 4.69 56.49
TUD_ANC-CV0-08 6.96 60.15*
TUD_ANC-CV0-14 6.37 60.27*
TUD_ANC-CV0-14 5.96 52.27
Average 5.80 57.99
Standard deviation 0.82 3.16
Coefficient of variation 14.1% 5.5%
* no failure of the specimen
0
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When the complete specimens are tested according to Protocol V1, the mortar cracks and the threaded bar yield and break after separation of the couplet in two parts.
It should be noted that with monotonic loading the threaded bar at the same displacement has not failed yet.
This suggested the introduction of Protocol V2.
Figure 55, Figure 56 and Table 21 report the force-displacement curves for each single performed test and a summary of the results.
Figure 54 – Failure for cyclic vertical shear loading of concrete-floor-to-wall connections (Protocol V1).
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Version 01 – Final 30/06/2017 Figure 55 – Force displacement curve for cyclic vertical shear loading of concrete-floor-to-wall connections
(Protocol V1).
Figure 56 – Summary of the envelope curves for cyclic vertical shear loading of concrete-floor-to-wall connections (Protocol V1).
Table 21 – Summary of results for cyclic vertical shear loading of concrete-floor-to-wall connections (Protocol V1).
Specimen Peak vertical force [kN] Displacement [mm]
TUD_ANC-CV1-05 5.57 59.11
TUD_ANC-CV1-10 6.74 59.75
TUD_ANC-CV1-11 5.75 59.81
TUD_ANC-CV1-15 6.21 54.64
TUD_ANC-CV1-16 8.39 57.60
TUD_ANC-CV1-17 7.36 57.38
Average 6.89 57.84
Standard deviation 1.03 2.12
Coefficient of variation 15% 4%
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The testing of the complete specimen according to protocol V2 was interrupted due to technical problems of the setup and only one test was performed. However, the results of that test are consistent with the results of the cyclic tests according to protocol V1 and therefore they are reported below.
At failure, the threaded bar yields and then breaks. The mortar and the couplet remain intact: nor cracks in the mortar joints nor interface detachment between the brick and the mortar were observed (Figure 57).
Figure 58, Figure 59 and Table 22 report the force-displacement curves and a summary of the results.
Figure 57 – Failure for cyclic vertical shear loading of concrete-floor-to-wall connections (Protocol V2).
Figure 58 – Force displacement curve of concrete-floor-to-wall connections (Protocol V2).
-0.5 0 0.5 1 1.5 2
-50 -25 0 25 50
Shear force (kN)
Shear displacement (mm) TUD_ANC-CV2-18
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F
Figure 59 – Summary of the envelope curves for cyclic vertical shear loading of concrete-floor-to-wall connections (Protocol V2).
Table 22 – Summary of results for cyclic vertical shear loading of concrete-floor-to-wall connections (Protocol V2).
Specimen Peak vertical force [kN] Displacement [mm]
TUD_ANC-CV2-18
1.57 29.84
Average - -
Standard deviation - -
Coefficient of variation - -
-0.5 0 0.5 1 1.5 2
-40 -30 -20 -10 0 10 20 30 40
Shear force [kN]
Displacement [mm]
TUD_ANC-CV2-18
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Summary of results
Table 23 reports the results obtained from the vertical shear loading of the complete specimens for different protocols.
Some differences can be noted:
- the peak forces of protocol V0 and protocol V1 are quite close (the cyclic loading leads to a 18.7%
higher peak force at the same displacement), while protocol V3 leads to a peak force 72.9% lower than that of V0.
- The displacement capacity of the specimens is significantly different: the test was stopped for both protocols V0 and V1 at a displacement of about 60 mm when the masonry couplet was about to touch the concrete part. However, at that displacement the threaded bar was yield for monotonic loading, whereas it failed for a lightly smaller displacement (58 mm). Under cyclic protocol V2 the specimens fail at about the half displacement (~30mm).
- The difference between the peak force and the displacement of protocol V1 and protocol V2 is significant. However, the average dissipated energy for each protocol (area of hysteretic loops of specimens tested according to protocol V1 or protocol V2) is roughly the same for both the protocols (about 290 J): in fact the larger number of cycles with smaller amplitude (protocol V2) leads to the same amount of energy being dissipated until the failure of the specimen with that dissipated when smaller number of cycles with larger amplitude is applied (protocol V1).
- In general, the connection is able to transfer significant amount of shear loads (>0.5 kN) only after large displacements (>20 mm), showing an extremely low stiffness for cycles of small amplitude, which are those that usually characterize this typology of connection. This is mainly due to the presence of the polystyrene that allows a long debonded section of the threaded bar.
The performed tests show that the connection is not able to transfer any significant shear load for displacement coherent with the deformation of the structure (<20 mm). The connection can be therefore modelled as truss elements with nonlinear behaviour.
Table 23 – Average results for vertical shear loading of concrete-floor-to-wall connections according to the different protocols.
Protocol Peak vertical force [kN] Displacement [mm]
V0 (monotonic) 5.80 >60
V1 (cyclic – small number of cycles per phase) 6.89 57.8 V2 (cyclic – large number of cycles per phase) 1.57 29.8
(a) (b)
Figure 60 – Indicative hysteretic curves for vertical shear cyclic loading: (a) Protocol V1; (b) Protocol V2
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References
[1] Messali, F. Esposito, R. (2016). Tests on anchorages: background document and testing protocol. Delft University of Technology. Report number C31B67WP6-1, version 03, 08 August 2016
[2] EN, B. (1999). 1015-3: 1999. Methods of test for mortar for masonry part 3: Determination of consistence of fresh mortar (by flow table).
[3] Esposito, R. Messali, F. Rots, J.G. (2016). Material characterization of replicated masonry and wall ties.
Final report 18 April 2016, Delft University of Technology, Delft, the Netherlands.
[4] EN, B. (2012). 846-5: 2012 Methods of test for ancillary components for masonry—Determination of tensile and compressive load capacity and load displacement characteristics of wall ties (couplet test).
[5] EN 1996-1-1+A1 (2013). Eurocode 6 – Design of masonry structures – Part 1-1: General rules for reinforced and unreinforced masonry structures. Nederlands Normalisatie-instituit (NEN).
[6] Graziotti F, Magenes G (2016): Experimental campaign on cavity walls systems representative of the Groningen building stock, EUCENTRE Technical Report, 16 June 2016, Pavia, Italy
[7] Esposito R, Ravenshorst G (2016): Meeting TU Delft & ARUP on timber connection and strengthening methods for cavity walls, Minutes, 30 June 2016, Delft, the Netherlands
Table A.1 – Declaration of performance of calcium silicate bricks (www.calduran.nl/producten/stenen/).