Tests on floor to wall connections for cavity wall systems

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Tests on floor to wall connections for cavity wall systems

Messali, F.; Paletti, E.

Publication date

2017

Document Version

Final published version

Citation (APA)

Messali, F., & Paletti, E. (2017). Tests on floor to wall connections for cavity wall systems. Delft University of

Technology.

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Date 01 August 2017

Corresponding author Francesco Messali (f.messali@tudelft.nl)

TU Delft Large-scale testing campaign 2016

TESTS ON FLOOR-TO-WALL CONNECTIONS

FOR CAVITY WALL SYSTEMS

Authors: Francesco Messali, Elisa Paletti

Cite as: Messali, F. Paletti, E. (2017). Tests floor-to-wall connections for cavity wall systems. Report number

C31B67WP6-5, 05 October 2017. Delft University of Technology.

This document is made available via the website ‘Structural Response to Earthquakes’ and the TU Delft repository. While citing, please verify if there are recent updates of this research in the form of scientific papers.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system of any nature, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of TU Delft.

TU Delft and those who have contributed to this publication did exercise the greatest care in putting together this publication. This report will be available as-is, and TU Delft makes no representations of warranties of any kind concerning this Report. This includes, without limitation, fitness for a particular purpose, non-infringement, absence of latent or other defects, accuracy, or the presence or absence of errors, whether or not discoverable. Except to the extent required by applicable law, in no event will TU Delft be liable for on any legal theory for any special, incidental consequential, punitive or exemplary damages arising out of the use of this report.

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Version 01 - Final 05/10/2017

1 Introduction

The present document comprehends a series of tests performed on new to-wall connections. New floor-to-wall connections are applied to prevent the out-of-plane failure of walls by anchoring the the wall (the outer leaf, when cavity walls are considered) to the structural components of the floor (concrete slabs or timber beams). Also gable walls can be connected to the timber ridge beam.

This document focuses on the case of cavity walls and concrete floors, and it aims to investigate the performance of dissipative anchors, such as Spouwdonuts by Total Wall (Figure 1), or similar products, because they are able not only to retain the out-of-plane movement of walls at the floor level but also to dissipate energy.

The Spouwdonut provides an effective constraint when the veneer approaches the floor, but not for outward movements of the veneer. Therefore, also SockFix (distributed in the Netherlands by Total Wall) or alternative anchors are commonly used. On the floor side, the anchor is anchored in the floor and passes through the centre of the donut. On the veneer side, the anchor is traditionally connected to a steel plate, placed on the outer face of the veneer. This technique is efficient, but it is very invasive aesthetically and localises the stresses on a relatively small surface, so that punching shear failure may occur. Alternatively, the existing technology named ‘seismic connectors’ (by Helifix, Figure 2), developed for wall-to-wall connections, can be adapted to provide an efficient constrain to the anchoring bar; this solution is fully concealed and visually sympathetic, and allows to spread the stresses over a large wall surface. However, since this system was originally developed for the forces generated by wall-to-wall connections (which are limited by the axial strength of wall retrofitting ties, that is smaller than the forces that a sockfix can transfer), its efficiency at anchoring the floor-wall connection must be investigated.

The current campaign focuses on the anchoring of this retrofitting system in the outer leaf of the cavity walls. Consequently, it does not aim at investigating the anchoring of the SockFix bars in the concrete floors, nor the dissipative performance of the Spouwdonuts.

Specific specimens reproducing the anchoring system combining the anchors and the seismic connectors (modified and strengthened to suit for the floor-wall situation) were tested. Since the anchor can be efficiently connected to either the Spouwdonuts or to the Sockfix, the tests are of general validity, independently on the selected anchoring system. A description of the specimens, of the test setup and of the outputs of the tests is provided in the following sections.

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Version 01 - Final 05/10/2017 Figure 2 – Use of ‘seismic connectors’ for wall-to-wall connection.

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2 Nomenclature

Symbols

This report adopts mainly the nomenclature used in Eurocode 6 [1]. In addition, the following symbols are adopted in the tables of the document:

B Length of a wallet / spacing between two adjacent anchors in a wall

Bmax Maximum spacing between two adjacent anchors in a wall for having over-resistant anchors dcr Cracking displacement

dp Displacement at peak du Ultimate displacement Fcr Cracking force

Fp Peak force

Ft Lateral precompression force acting at the level of the connection H Interstorey height (height of a wall)

Kin Initial Stiffness

t Thickness of the wallet/wall

γ Self-weight of the masonry

W Weight of the wall

Abbreviations

Avg. Average

St. dev. Standard deviation C.o.V. Coefficient of variation

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3 Testing procedure

Description of the specimens

The specimens were built in the Stevin II laboratory at the Delft University of Technology. The installation of Helibars and Seismic connectors was completed by Marten de Jong (TotalWall).

The existing technology named ‘Seismic connectors’ couples a wall tie (anchored in the inner leaf of the cavity wall) to a HeliBar 4.5mm diameter stainless steel wire which is embedded into the outer leaf mortar joint [the properties of the mortar can be found in the Appendix A]. For the current campaign, the system was modified to ensure higher performance: M8 anchors are used in place of the wall ties, and two ‘Supersix Helibars’ embedded in the mortar joint replace the single HeliBar.

The dimensions of the specimens are selected to be representative of the distance between two adjacent Spouwdonuts (estimated equal to approximately 60 cm). Hence, given the dimensions of bricks, a width of 65 cm was selected.

Two typologies of specimens were constructed, differeing uniquely for the material where the ‘Supersix Helibars’ are embedded:

 Specimens with ‘Supersix Helibars’ embedded in epoxy resin (CrackBond TE by Helifix [1]). This is a general purpose thixotropic epoxy resin for bonding cracked masonry, metal fixings and anchors. The resin gels rapidly and cures within 24 hours;

 Specimens with ‘Supersix Helibars’ embedded in grout (HeliBond by Helifix [2]). This is a high performance cementitious grout, suitable for bonding brick, stone, pre-cast concrete and blocks. HeliBond takes 4 weeks to full hardening, but it is cheap and easy to be installed.

First, the masonry wallets were built.

The dimensions of the masonry wallets are provided in Figure 3a.

(a) (b)

Figure 3 – Dimensions of the specimen.

After the hardening of the mortar was complete (4 weeks), the anchors are installed. The installation procedure should proceed as follows:

- A slot into which the Helibars will be bonded is cut. Appropriate clearance and adequate depth must be provided to provide good fixing. The slot is created in the middle mortar joint and is 40 mm deep (Figure 4a);

- The slot is cleaned of all loose material and dust, flushed out with water and the brickwork is left damp (Figure 4b);

- A hole in the middle of the specimen is drilled. It is important to make the correct size of the slot and of the hole to ensure a good bond (Figure 4c);

- A M8 connector is placed perpendicular to the wall plane (Figure 4d);

- The seismic connector is connected to the M8 anchor; the two Supersix helibars are inserted in the connector and placed in the slot (Figure 4e);

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Version 01 - Final 05/10/2017 - The slot is completely filled with resin (CrackBond TE by Helifix) or grout (Helibound by Helifix) so that the Helibars are completely embedded. The resin and grout are injected in a continuous operation using a manual pointing gun (Figure 4f).

The connection of the M8 anchor and the helibars may be more complex in a real wall, but it is possible given the high flexibility of the bars.

An overview of the procedure to prepare the specimen is shown in the Figure 4.

(a) (b)

(c) (d)

(e) (f)

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Testing protocol

Test setup

The test apparatus is schematically represented in Figure 5 and comprehends:

 Simple supports for the specimen(1). The supports consist of four steel tubes (5) anchored to the support beam (11) by means of threaded bars and not connected to the lateral vertical steel plates (4) used to provide the lateral pre-compression load (see below). The vertical plates are free to rotate, so that negligible clamping actions are applied to the specimen. Also temporary supports are provided (6) until the beginning of the test.

 An apparatus to apply and maintain constant compressive stresses on the specimen. The force is provided by a hydraulic jack (10) acting in the horizontal direction and perpendicular to the bed joint plane. The system is self-equilibrated by four threaded bars (7) connecting the vertical plates (4).  A test machine to apply the vertical load. The pull-out 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 tie during loading. The machine is provided with a clamp (3) for gripping efficiently the free end of the M8 anchor (2).

Figure 5 – Test setup.

Loading scheme

Since the anchoring system would be mainly solicited when floor and wall are moving away (Figure 6), whereas the spouwdonuts work as contrast when they move closer, only a single protocol with monotonic pull-out loading was applied in order to analyze the out-of-plane failure of walls.

The pull-out load was applied in displacement control with a speed rate of 0.05 mm/s.

Three different pre-compression levels were investigated in order to achieve the following failure modes: 1) Zero precompression: flexural failure of the specimen (the connection is over-resistant); 2) Low precompression level: the connection fails after cracking of the section;

3) High precompression level: the connection fails before cracking of the section.

The values of the low and high pre-compression levels can be properly defined on the base of the strength of the connection. Preliminarily, the values 0.0 MPa – 0.1 MPa – 0.3 MPa were considered.

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Version 01 - Final 05/10/2017 - 2 tests, one with 0.1 MPa and one with 0.3 MPa, for the specimens in which the helibars are

embedded in epoxy-resin;

- 15 tests, 5 at each level of precompression, for the specimens in which the helibars are embedded in grout.

The name and the number of the specimens tested for each loading protocol are listed in Table 1 and in Table 2.

Figure 6 – Schematic representation of floor and wall moving away. Table 1 – Specimens tested with resin for each loading protocol.

Name Lateral Pressure Name specimen

TUD_ANC-104 0.1 MPa TUD_ANC-104-02

TUD_ANC-105 0.3 MPa TUD_ANC-105-01

Table 2 – Specimens tested with grout for each loading protocol.

Name Lateral Pressure Name specimen

TUD_ANC-101 0.0 MPa TUD_ANC-101-06 TUD_ANC-101-07 TUD_ANC-101-08 TUD_ANC-101-09 TUD_ANC-101-15 TUD_ANC-102 0.1 MPa TUD_ANC-102-01 TUD_ANC-102-02 TUD_ANC-102-03 TUD_ANC-102-12 TUD_ANC-102-14 TUD_ANC-103 0.3 MPa TUD_ANC-103-04 TUD_ANC-103-05 TUD_ANC-103-10 TUD_ANC-103-11 TUD_ANC-103-13

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Instrumentation

A couple of linear potentiometers is installed symmetrically on the side opposite to the M8 connector, as shown in Figure 7, in order to identify the opening of the crack in the middle section of the specimen and distinguish between the different failure modes listed in the previous section (Loading scheme). Their measuring range is 10 mm with an accuracy of 0.1%.

(a) (b)

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4 Experimental results

Specimens with resin embedment of the helibars

Precompression level: 0.1 ± 0.01 N/mm2 _{(TUD_ANC-104)} Only one specimen was tested (TUD_ANC-104).

The specimen failed when the middle section cracked, first the mortar and then the epoxy resin. Since the resin-brick bond is very strong, the crack propagated also in the brick. The full layer detached from the bricks and started sliding causing the failure of the specimen for large displacements. The failure mode sequence is depicted in Figure 8.

Figure 9a shows the force-time curve and the stiffness when the crack is opening.

During the whole loading history, the connection between the M8 anchor and the helibars didn’t fail (hence it was over-resistant). In fact, a first peak of resistance of the specimen is achieved when the middle joint cracks, as shown in Figure 9b. The peak strength is then determined by the sliding between the bricks and the cracked joint layer. For this reason, a stable behaviour after the first crak is observed, and the final failure is reached for extremely high displacements (about 80 mm).

(a) (b)

(c) (d)

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(a) (b)

Figure 9 – Force vs. displacement, and force/crack opening vs. time curves for specimen TUD_ANC-105-02. In order to understand the results of the tests and their graphical representation, the following points are noted:

1. The nonlinear behaviour of the first part of the curve is due to the used setup and not to the actual physical behaviour of the specimen. Since the temporary supports (6 in Figure 5) must be removed after the beginning of the test to allow the free rotation of the specimen (Figure 10), a small gap must be left between the bottom steel tubes (5 in Figure 5) and the steel supporting beam (11 in Figure 5). Thus, when the vertical displacement is applied to the connector, the specimen uplifts and touches the top steel tubes. Then, both top and bottom steel tubes (which are connected) are uplifted along with the specimen and touch the steel supporting beam, giving full retain to the specimen vertical movement. Therefore, it is possible to consider the test really starting only when the full constraint is provided. The different phases are shown in Figure 11.

(a) (b)

Figure 10 – View of the set-up before (a) and after (b) removing the temporary supports.

y = 2,6438x - 2,5043 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 V e r ti c al F or c e (kN) Vertical Displacement (mm)

TUD_ANC-104-02

TUD_ANC-104-02 K crack opening 0 0,5 1 1,5 2 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 Crac k Opening Displace me nt (mm) V er tic al F or ce (kN ) Time (s)

Force and Crack Opening vs Time

TUD_ANC-104-02 LVDT 01 LVDT 02

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Version 01 - Final 05/10/2017 2. Is possible to subdivide the initial part of the force-displacement curve (until the crack in the middle joint

opens, or the connection resistance is reached) in three different parts: a. initial lifting of the sample from the temporary supports;

b. the specimen is hanged to the clamp via the anchor but the vertical movement is not contrasted (i.e. the steel tubes still do not touch completely the support beam);

c. the vertical movement of the specimen is fully constrained. Since phases a. and b. still occurs when the specimen still behaves elastically, the stiffness derived in phase c. is considered the initial elastic stiffness of the specimen.

Figure 11 – Initial phases of the loading history for specimen TUD_ANC-104-02.

3. For the reasons mentioned at points 1-2, in the following charts of the report a fictitious linear initial branch was created in substitution of the part of the curve representing phases a. and b. (Figure 12). The same approach was followed for the force-time and crack opening-time curves (Figure 13).

(a) (b)

Figure 12– Analysis of the vertical force-vertical displacement curve.

y = 3,7521x y = 0,5177x + 1,4154 y = 2,6438x - 2,5043 0 1 2 3 4 5 6 7 8 0 1 2 3 4 V erti ca l F o rce (k N ) Vertical Displacement (mm) TUD_ANC-104-02 TUD_ANC-104-02 a b c y = 2,6438x - 2,5043 0 1 2 3 4 5 6 7 8 0 1 2 3 4 V er tic al For ce (kN ) Vertical Displacement (mm)

TUD_ANC-104-02

TUD_ANC-104-02 K crack opening y = 2,6438x + 0,0035 0 1 2 3 4 5 6 7 8 0 1 2 3 4 V er tic al For ce (k N) Vertical Displacement (mm)

TUD_ANC-104-02

TUD_ANC-104-02 K crack opening

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(a) (b)

Figure 13 – Analysis of the force-time and crack opening-time curves.

Precompression level: 0.3 ± 0.01 N/mm2 _{(TUD_ANC-105)}

The failure mechanism observed with this level of precompression was similar to that observed for the smaller pre-compression, but at the end of the test the helibars failed with brittle ruptrure. The failure mode sequence is depicted in Figure 14.

Figure 15 reports the force-displacement and the force/crack opening-time for each single performed test.

(a) (b)

(c) (d)

Figure 14 – Sample at failure of sample TUD_ANC-105-01. 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 Crack Open ing Dis p lac eme n t (mm) V e r ti c al F or c e (kN) Time (s)

Force and Crack Opening vs Time

TUD_ANC-104-02 LVDT 01 LVDT 02 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 Crac k Opening Disp lac em ent (mm) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

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(a) (b)

Figure 15 – Force vs. displacement, and force/crack opening vs. time curves for specimen TUD_ANC-105-01.

Influence of the precompression

The results summarised in Table 3 and shown in Figure 16 indicate the influence of the level of precompression between 0.1 MPa and 0.3 MPa.

Table 3 – Summary of the reults for specimens with helibars embedded in resin.

Specimens Kin

(kN/mm) Fcr[kN] dcr [mm] Fp [kN] dp [mm] du [mm]

TUD_ANC-104-02 2.64 5.98 1.22 6.87 41.0 82.9

TUD_ANC-105-01 1.80 8.88 2.91 11.7 10.8 66.1

Figure 16 – Influence of the level of precompression for specimens with helibars embedded in resin.

y = 1,7993x + 0,0112 0 2 4 6 8 10 12 0 20 40 60 80 100 V er tic al For ce (kN ) Vertical Displacement (mm)

TUD_ANC-105-01

TUD_ANC-105-01 K crack opening 0 0,5 1 1,5 2 0 2 4 6 8 10 12 14 0 40 80 120 160 200 Cr ac k O peni ng Displ ac e me nt (m m) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

TUD_ANC-105-01 LVDT 01 LVDT 02 0 2 4 6 8 10 12 14 0 20 40 60 80 100 V er tic al For ce (kN ) Vertical Displacement (mm)

Summary

0.1 MPa TUD-ANC-104-02 0.3 MPa TUD-ANC-105-01

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Specimens with grout embedment of helibars

Precompression level: 0.01 N/mm2_{(Specimens TUD_ANC-101)}

The observed failure mechanism for no lateral precompression is characterised by the sudden cracking of the less resistant section (usually the middle one, or the one next to that). Flexural failure of the specimen, followed by sliding of the two parts of the wallet, was observed. The combination of this two mechanisms lead to a short stable post-peak branch followed by complete failure of the wallet. The connection was over-resistant. The specimens at failure are shown in Figure 17.

(a) TUD_ANC-101-06 (b) TUD_ANC-101-07

(c) TUD_ANC-101-08 (d) TUD_ANC-101-09

(e) TUD_ANC-101-15

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Version 01 - Final 05/10/2017 The behaviour of the samples TUD_ANC-101-07 and TUD_ANC-101-15 showed lower resistance but higher displacement capacity after cracking. According to the different failure mode, different strength and ductility are measured. Figure 18 reports the force-displacement for each single performed test.

Table 4 and Figure 19 report a summary of the peak force and relative displacements. It was not possible to use the LVDTs data because the cracks did not opened in the central joint (the one where they were placed), except for specimen TUD_ANC-101-08. For this reason, it was not possible to report the crack opening force and the corresponding displacement in Table 4.

Figure 18 – Force vs. displacement, and force/crack opening vs. time curves for specimens TUD_ANC-101. y = 1,7625x + 0,0155 0 0,5 1 1,5 2 2,5 3 3,5 0 5 10 15 20 25 30 35 40 45 V er tic al For ce (kN ) Vertical Displacement (mm)

TUD_ANC-101-06

TUD_ANC-101-06 K crack opening y = 1,5519x + 0,061 0 0,5 1 1,5 2 2,5 3 3,5 0 5 10 15 20 25 30 35 40 45 V er tic al For ce (k N) Vertical Displacement (mm)

TUD_ANC-101-07

TUD_ANC-101-07 K crack opening y = 1,6737x - 0,0118 0 0,5 1 1,5 2 2,5 3 3,5 0 5 10 15 20 25 30 35 40 45 V er tic al For ce (kN ) Vertical Displacement (mm)

TUD_ANC-101-08

TUD_ANC-101-09

TUD_ANC-101-15

TUD_ANC-101-15 K crack opening

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Version 01 - Final 05/10/2017 Table 4 – Summary of the results for specimens TUD_ANC-101.

Specimens _[kN/mm]Kin _[kN]Fp _[mm]dp _[mm]du TUD_ANC-101-06 1.76 3.21 1.83 11.52 TUD_ANC-101-07 1.55 1.84 10.04 28.50 TUD_ANC-101-08 1.67 2.77 1.67 23.26 TUD_ANC-101-09 1.57 2.67 1.73 9.93 TUD_ANC-101-15 0.72 1.90 29.64 32.72 Average 1.46 2.48 8.98 21.19 Deviation 0.42 0.59 12.09 10.14 CoV [%] 28.63 23.93 134.67 47.84

Figure 19 – Summary of the “Force-Displacement curves” at zero lateral precompression. 0 1 2 3 4 0 10 20 30 40 50 V er tic al For ce (kN ) Vertical Displacement (mm)

0.01 MPa

TUD_ANC-101-06 TUD_ANC-101-07 TUD_ANC-101-08 TUD_ANC-101-09 TUD_ANC-101-15 Average - 0.01 MPa

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Precompression level: 0.1 ± 0.01 N/mm2_{(Specimens TUD_ANC-102)} The observed failure mechanism for small precompression is characterised by two different phases: (i) the middle mortar joint cracks; (ii) the helifix bars bend and slides inside the mortar. As a consequence, they push the grout gradually off the bricks, starting at the point where the tie was embedded and propagating to both sides. The first crack is usually followed by a drop of resistance, but it does not always coincide with the peak strength of the specimen. The samples at failure are depicted in Figure 20.

(a) TUD_ANC-102-01 (b) TUD_ANC-102-02

(c) TUD_ANC-102-03 (d) TUD_ANC-102-04

(e) TUD_ANC-102-05

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Version 01 - Final 05/10/2017 Figure 21 reports the force-displacement and the force/crack opening displacement-time for each single performed test. Table 5 and Figure 22 report a summary of the crack opening force, peak force and relative displacements. (a) TUD_ANC-102-01 (b) TUD_ANC-102-02 (c) TUD_ANC-102-03 y = 1,0397x + 0,7252 0 1 2 3 4 5 6 0 40 80 120 160 200 V er tic al For ce (kN ) Vertical displacement (mm)

TUD_ANC-102-01

TUD_ANC-102-01 K crack opening 0 1 2 3 4 0 1 2 3 4 5 6 0 50 100 150 200 250 Crac k Opening Displace me nt (mm) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

TUD_ANC-102-01 LVDT 01 LVDT 02 y = 1,27x - 0,0127 0 1 2 3 4 5 6 0 40 80 120 160 200 V e rti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-102-02

Force and Crack Opening vs Time

TUD_ANC-102-02 LVDT 01 LVDT 02 y = 0,3979x + 0,1741 0 1 2 3 4 5 6 0 40 80 120 160 200 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-102-03

Force and Crack Opening vs Time

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Version 01 - Final 05/10/2017 (d) TUD_ANC-102-12

(e) TUD_ANC-102-14

Figure 21 – Force vs. displacement, and force/crack opening vs. time curves for specimens TUD_ANC-102. Table 5 – Summary of the results for specimens TUD_ANC-102.

Specimens _[kN/mm]Kin _[kN]Fcr _[mm]dcr _[kN]Fp _[mm]dp _[mm]du TUD_ANC-102-01 1.04 5.09 4.20 5.09 4.20 194 TUD_ANC-102-02 1.27 3.78 2.99 4.40 9.84 182 TUD_ANC-102-03 0.40 4.59 11.10 5.44 28.02 181 TUD_ANC-102-12 1.44 4.52 3.13 4.52 3.50 182 TUD_ANC-102-14 1.49 5.17 3.49 5.17 3.49 186 Average 1.13 4.63 4.98 4.93 9.81 185 Deviation 0.44 0.56 3.45 0.44 10.52 5.5 CoV [%] 39.35 12.01 69.25 9.02 107.25 3.0 y = 1,4373x + 0,0173 0 1 2 3 4 5 6 0 40 80 120 160 200 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-102-12

Force and Crack Opening vs Time

TUD_ANC-102-12 LVDT 01 LVDT 02 y = 1,4878x - 0,0196 0 1 2 3 4 5 6 0 40 80 120 160 200 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-102-14

Force and Crack Opening vs Time

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Version 01 - Final 05/10/2017 Figure 22 – Summary of the “Force-Displacement curves” at 0.1 MPa precompression.

0 2 4 6 8 10 0 40 80 120 160 200 V er tic al For ce (kN ) Vertical Displacement (mm)

0.1 MPa

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Precompression level: 0.3 ± 0.01 N/mm2_{(Specimens TUD_ANC-103)} The observed failure mechanism for high precompression was similar to that observed for small precompression (Section 4.2.2).

Figure 23 shows the samples at failures. Figure 24 reports the force-displacement and the force/crack opening displacement-time for each single performed test. Table 6 and Figure 25 report a summary of the crack opening force, peak force, fracture force and relative displacements.

(a) TUD_ANC-103-04 (b) TUD_ANC-103-05

(c) TUD_ANC-103-06 (d) TUD_ANC-103-07

(e) TUD_ANC-103-08

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Version 01 - Final 05/10/2017 (a) TUD_ANC-103-04 (b) TUD_ANC-103-05 (c) TUD_ANC-103-10 y = 1,539x + 0,0065 0 1 2 3 4 5 6 7 8 9 10 0 40 80 120 160 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-103-04

TUD_ANC-103-04 K crack opening 0 1 2 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 Cra ck Openi ng Displac em ent(m m) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

TUD_ANC-103-04 LVDT 01 LVDT 02 y = 0,9357x - 0,0154 0 1 2 3 4 5 6 7 8 9 10 0 40 80 120 160 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-103-05

TUD_ANC-103-05 K crack opening 0 1 2 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 Crac k Opening Displace me nt(mm) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

TUD_ANC-103-05 LVDT 01 LVDT 02 y = 1,0386x - 0,0015 0 1 2 3 4 5 6 7 8 9 10 0 40 80 120 160 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-103-10

0 1 2 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 _Crac k Opening Displace me nt(mm) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

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Version 01 - Final 05/10/2017 (d) TUD_ANC-103-11

(e) TUD_ANC-103-13

Figure 24 – Force vs. displacement, and force/crack opening vs. time curves for specimens TUD_ANC-103. Table 6 – Summary of the results for specimens TUD_ANC-103.

Specimens _[kN/mm]Kin _[kN]Fcr _[mm]dcr _[kN]Fp _[mm]dp _[mm]du TUD_ANC-103-04 1.54 8.63 5.60 8.63 5.60 123.58 TUD_ANC-103-05 0.94 8.53 9.13 8.53 10.05 129.66 TUD_ANC-103-10 1.04 7.35 7.08 7.45 10.44 123.81 TUD_ANC-103-11 1.45 8.44 5.82 8.45 59.88 148.12 TUD_ANC-103-13 1.55 6.70 4.31 7.57 14.07 61.12 Average 1.30 7.93 6.39 8.13 20.01 117.26 Deviation 0.29 0.86 1.82 0.57 22.49 32.94 CoV [%] 22.5 10.8 28.5 7.0 112 28.1 y = 1,4498x + 0,0018 0 1 2 3 4 5 6 7 8 9 10 0 40 80 120 160 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-103-11

0 1 2 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 _Crac k O penin g Disp lac em ent(mm ) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

TUD_ANC-103-11 LVDT 01 LVDT 02 y = 1,5525x + 0,0074 0 1 2 3 4 5 6 7 8 9 10 0 40 80 120 160 V e r ti c a l F or c e (k N ) Vertical Displacement (mm)

TUD_ANC-103-13

0 1 2 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 _Crac k Opening Displace me nt(mm) V er tic al For ce (kN ) Time (s)

Force and Crack Opening vs Time

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Version 01 - Final 05/10/2017 Figure 25 – Summary of the “Force-Displacement curves” at 0.3 MPa precompression.

0 2 4 6 8 10 0 40 80 120 160 200 V er tic al For ce (kN ) Vertical Displacement (mm)

0.3 MPa

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Influence of the precompression

The results of every test performed on specimens whose helibars were embedded in mortar are summarised in Table 7 and shown in Figure 26 and Figure 27, respectively.

Table 7 – Summary of the main results for specimens with helibars embedded in mortar.

Precompression

level [kN/mm] Kin [kN] Fcr [mm] dcr [kN] Fp [mm] dp [mm] du

0.01 MPa 1.46 - - 2.48 8.98 21.19

0.1 MPa 1.13 4.63 4.98 4.93 9.81 184.89

0.3 MPa 1.30 7.93 6.39 8.13 20.01 117.26

Figure 26 – Force-displacement curves for every tested specimen (helibars embedded in mortar).

Figure 27 – Average of the force-displacement curves for every tested specimen (helibars embedded in mortar). 0 2 4 6 8 10 0 40 80 120 160 200 V er tic al For ce (k N) Vertical Displacement (mm)

Summary

0.01 MPa 0.1 MPa 0.3 MPa 0 2 4 6 8 10 0 40 80 120 160 200 V er ti cal F or ce (kN) Vertical Displacement (mm)

Influence of the level of precompression

Average - 0.01 MPa Average - 0.1 MPa Average - 0.3 MPa

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Interpretation of the results: influence of precompression and

grout/resin embedment

Table 8 and Figure 28 summarise the most significant average properties derived for every performed test. Table 8 - Summary of the main results for every tested specimens.

Precompression level Embedment [kN/mm] Kin Fcr [kN] dcr [mm] Fp [kN] dp [mm] du [mm] 0.01 MPa Grout 1.46 - - 2.48 8.98 21.19 0.1 MPa Resin 2.64 5.98 1.22 6.87 41.01 82.90 Grout 1.13 4.63 4.98 4.93 9.81 184.89 0.3 MPa Resin 1.80 8.88 2.91 11.71 10.82 66.12 Grout 1.30 7.93 6.39 8.13 20.01 117.26

Figure 28 - Average of the force-displacement curves for every tested specimen. The following conclusions can be derived:

 The resistance of the specimens is strongly affected by the lateral compressive stresses applied on the wallets. The peak strength increases almost linearly with the precompression.

Similarly to the procedure applied to derive the frictional properties of masonry from triplet tests, the following equation may be derived, based on a linear regression of the measured peak strength values at varying the precompression level:

𝐹𝑃= 2.6 𝑘𝑁 + 0.3 𝐹𝑇 (1)

where FT is the precompressive vertical force acting on the section where the anchor is embedded, considering a spacing between the anchors of 65 cm.

Equation (1) can be applied only to anchors embedded in mortar with spacing of 65 cm (and, in general, is valid only for anchoring systems with geometrical and material properties similar to those of the tested specimens).

0 2 4 6 8 10 12 14 0 40 80 120 160 200 V er tic al For ce (kN ) Vertical Displacement (mm)

Summary

Average Grout - 0.01 MPa Average Grout - 0.1 MPa Average Grout - 0.3 MPa Resin - 0.1 MPa Resin - 0.3 MPa

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Version 01 - Final 05/10/2017  Also the ductility of the specimens is affected by the lateral precompression. Specimens without any precompression show significant smaller ultimate displacements. On the other hand the increase in displacement capacity is not proportional to the applied compressive stresses, but the largest ductility is achieved for a small level of precompression.

 The use of epoxy resin allows for larger resistance of the connection because the helibars do not slide in the embedding material. In a real wall, where the helibars are continue for longer lengths and connect more than a single anchor, the behaviour of the single connection may be closer to that experimentally observed with epoxy resin also when the grout is used.

 For each specimen type (same precompression level and embedment of the helibars) the dispersion of the results is small (e.g. the peak strength has C.o.V. < 10% for 0.1 MPa and 0.3 MPa precompression), except when no lateral precompression is applied (C.o.V. > 20%), as it may be observed in Figure 26. This is the only case for which two different failure modes are observed (either flexural or sliding predominant failure). Therefore, even though a small number of specimens have been tested, the observed results may be considered representative of the connection behaviour.

Figure 29 – Set-up and asymmetric boundary conditions

A

B

A

a

B

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Efficiency of the tested connection typology

In order to evaluate in which conditions the assessed retrofitting anchor technique is efficient, a portion of a simple one-way spanning wall is considered (Figure 30).

Simple kinematic analyses can be performed to estimate the out-of-plane capacity of the wall, accordingly to the approach suggested in major International Standards (NZSEE [4], NTC [5][6]) and in Annex H of the recent Dutch standard (NPR 9998:2017 [7]). A scheme of the expected out-of-plane failure mechanism of the wall is depected in Figure 31.

Figure 30 – Simple wall considered in the model

Three local cracks are identified: at top, bottom and mid-height of the wall. Top and bottom hinges are located on the outer side of the wall (the wall-to-floor connections are assumed to be able to efficiently transfer the load to the outer leaf); the central hinge is on the inner side of the wall (Figure 31a).

The forces acting on the rigid blocks are shown in Figure 31b: Ft is the load acting at the top of the wall, Wt and Wbare the self-weights of the wall and RHt and RHbare the reaction forces.

This model can be applied to compute the factor between the force that are expected to be transferred by the tested anchors and those measured in the experiments. The value of this safety factor provides an indication of the efficiency of the anchors in case of earthquakes.

In fact, the force that the anchors must be able to transfer is equal to the sum of the reaction RHb from the lower portion of the wall above the considered floor level and the reaction RHt from the upper portion of the

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Version 01 - Final 05/10/2017 wall below the floor level. For sake of simplicity, this sum is estimated as the total seismic force acting on the wall below the considered floor level. Hence, the single top load Ft may correspond to the lateral confining force applied on the tested specimens, and a direct comparison may be performed.

(a) (b)

Figure 31 – (a) Scheme of the failure mechanism of the wall, (b) Static scheme of top and bottom wall. Based on the described model, the following equations can be derivated :

Top portion of the wall:

𝑅𝑣𝑖= 𝑊𝑡+ 𝐹𝑡 with 𝑊𝑡= (1 − 𝛼) ∗ 𝑊 where 𝑊 is the overall weight of the wall (2)

𝑅𝐻𝑖= 𝜆 ∗ 𝑊𝑡− 𝑅𝐻𝑡 (3) −𝐹𝑡∗ 𝑡 + 𝑅𝐻𝑡∗ (1 − 𝛼) ∗ 𝐻 − 𝜆 ∗ 𝑊𝑡∗ (1 − 𝛼) ∗ 𝐻 2− 𝑊𝑡∗ 𝑡 2= 0 (4)

Bottom portion of the wall:

𝑅_𝑣 = 𝑅_𝑣𝑖 + 𝑊𝑏 with 𝑊𝑏= 𝛼 ∗ 𝑊 (5) 𝑅𝐻𝑏= 𝑅𝐻𝑖+ 𝜆 ∗ 𝑊𝑏 (6) 𝜆 ∗ 𝑊𝑏∗ 𝛼 ∗ 𝐻 2− 𝑅𝐻𝑏∗ 𝛼 ∗ 𝐻 + 𝑅𝑣∗ 𝑡 − 𝑊𝑏∗ 𝑡 2= 0 (7)

From equations (2)-(7) the following value of λ is computed: 𝜆 = 2 ∗ 𝑡 𝑊 ∗ 𝐻∗ [ 𝐹𝑡 1 − 𝛼+ 𝑊 + 𝐹𝑡 𝛼 ] (8)

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Version 01 - Final 05/10/2017 That is minimized by the following value of α:

𝛼 =𝐹𝑡+ 𝑊 − √𝐹𝑡∗ (𝐹𝑡+ 𝑊)

𝑊 (9)

The data input for each precompression level are shown in Table 9, where B is the distance considered between two consecutive spouwdonuts (Figure 32)..

Table 9 – Data input.

B [mm] 650 Precompression level [MPa] Ft [kN]

t [mm] 100 0.01 MPa 0.65

H [mm] 2700 0.1 MPa 6.5

𝛾 [kN/m3] 16.5 0.3 MPa 19.5

W (=B*t*H*𝛾) [kN] 2.89

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Version 01 - Final 05/10/2017 The evaluation of α, λ, RHt and RHb is performed for each precompression level 0.01 MPa, 0.1 MPa and 0.3 MPa, as shown in Table 10. The maximum spacing (Bmax) between two adjacent anchors in a wall for having over-resistant anchors (i.e. for which the safety factor is 1) is also computed.

Figure 33 shows a comparison between the expected forces on the anchors and their experimentally measured strength. In Figure 34 the linear regression line of the measured strength of the anchors is also plotted and compared to the expected force acting on the anchors.

For the considered spacing (0.65 m), the value of the safety factor is larger than one for every of the three considered precompression levels. However, the safety margin gets smaller and smaller at increasing levels of the vertical load (precompression levels). It should be noted, however, that every single test reached a peak strength larger than the reaction value computed for a distance between the anchors of 0.65 m (i.e the experimental configuration), and the minimum value of Bmax is 0.85 m (for 0.3 MPa of precompression level). Besides, vertical forces acting on veneers are usually small (since the floors are not supported by the outer leaves), and hardly exceed the 0.1 MPa value (weight of 6 m of masonry on top of the considered level). Finally, the linear regression lines in Figure 34 show that the predicted force and the anchor strength (both average and minimum) increase similarly for higher values of precompression, so that a small margin would be maintained also for large values of vertical compressive stresses.

It may be concluded that the tested anchoring system is efficient if the anchors are placed at the originally planned distance of 0.65 m.

Table 10 – Data output.

Forces found with the model

0.01 MPa 0.1 MPa 0.3 MPa

α 0.70 0.55 0.52 λ 0.185 0.806 2.14 RHt[kN] 0.38 1.27 3.21 RHb[kN] 0.16 1.06 2.99 Fs = RHt+ RHb[kN] 0.54 2.34 6.20 Force measured experimentally F[kN] 2.48 4.93 8.13 Safety Factor = 𝑭 𝑭𝒔 4.63 2.11 1.31 Bmax [m] 3.01 1.37 0.85

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Version 01 - Final 05/10/2017 Figure 33. Comparison between the expected forces on the anchors and their experimentally measured

strength.

Figure 34. Comparison between linear regression lines of the expected forces on the anchors and their experimentally measured strength.

0 2 4 6 8 10 12 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 F or ce (kN)

Precompressive stresses (MPa)

Expected force acting on the anchors

Minimum experimental strength of anchors embedded in grout Average experimental strength of anchors embedded in grout Average experimental strength of anchors embedded in resin

y = 0.3x + 0.4 y = 0.3x + 2.0 y = 0.3x + 2.6 0 2 4 6 8 10 12 0 5 10 15 20 25 F or ce (kN) Precompressive load (kN)

Expected force acting on the anchors Linear (Expected force acting on the anchors)

Minimum experimental strength of anchors embedded in grout Average experimental strength of anchors embedded in grout Average experimental strength of anchors embedded in resin

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Aknowledgements

TotalWall and especially Marten de Jong are gratefully acknowledged for providing and installing the Helibars and the Seismic connectors.

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References

[1] 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).

[2] The techinacal sheet of CrackBond – TE can be examine on the site https://www.helifix.co.uk/uploads/pdfs/PS-CrackBond-TE-self-mix.pdf

[3] The techinacal sheet of HeliBond can be examine on the site

http://www.helifix.com/files/2017/08/Helifix-HeliBond-Halfen-USA.pdf

[4] NZSEE, New Zealand Society for Earthquake Engineering. The seismic assessment of existing buildings, Part C8: Seismic assessment of unreinforced masonry buildings. Wellington, New Zealand: MBIE, EQC, SESOC, NZSEE and NZGS; 2017

[5] MIT, Ministry of Infrastructures and Transportations. NTC 2008. Decreto Ministeriale 14/1/2008: Norme tecniche per le costruzioni., G.U.S.O. n.30 on 4/2/2008; 2008. (in Italian)

[6] MIT, Ministry of Infrastructures and Transportation. Circ. C.S.Ll.Pp. No. 617 of 2/2/2009: Istruzioni per l’applicazione delle nuove norme tecniche per le costruzioni di cui al Decreto Ministeriale 14 Gennaio 2008. G.U. S.O. n. 27 of 26/2/2009, No. 47; 2009. (in Italian)

[7] Nederlands Normalisatie Instituut (NEN). NEN NPR 9998:2017. Assessment of structural safety of buildings in case of erection, reconstruction and disapproval - Basic rules for seismic actions: induced earthquakes; 2017. (partially in Dutch)

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Appendix A.

The mortar used to build the specimens is called “BM2 version2” produced by the company: Remix Droge Mortel BV [3].

The materials used to prepare the mixture are shown in the Table 11. Table 11 – Mixture of the mortar BM2 version 2

Type Raw materials Quantity

C CEM1 42.5 R 60.00 kg V V1 Limestone filler 0.09 MM 40.00 kg V V2 Hydrated lime CL80S 90.00 kg T T1 SAND 1 0.00-1.20 630.00 kg T T2 SAND 2 1.20-3.55 180.00 kg H Air intrainer 0.05 kg

Tests on floor to wall connections for cavity wall systems

Tests on floor to wall connections for cavity wall systems

Messali, F.; Paletti, E.

Publication date

2017

Document Version

Final published version

Citation (APA)

Messali, F., & Paletti, E. (2017). Tests on floor to wall connections for cavity wall systems. Delft University of

Technology.

Important note

To cite this publication, please use the final published version (if applicable).

Please check the document version above.

TU Delft Large-scale testing campaign 2016

TESTS ON FLOOR-TO-WALL CONNECTIONS

FOR CAVITY WALL SYSTEMS

Authors: Francesco Messali, Elisa Paletti

Table of Contents

1 Introduction

2 Nomenclature

Symbols

Abbreviations

3 Testing procedure

Description of the specimens

Testing protocol

4 Experimental results

Specimens with resin embedment of the helibars

TUD_ANC-104-02

Force and Crack Opening vs Time

TUD_ANC-104-02

TUD_ANC-104-02

Force and Crack Opening vs Time

Force and Crack Opening vs Time

TUD_ANC-105-01

Force and Crack Opening vs Time

Summary

Specimens with grout embedment of helibars

TUD_ANC-101-06

TUD_ANC-101-07

TUD_ANC-101-08

TUD_ANC-101-09

TUD_ANC-101-15

0.01 MPa

TUD_ANC-102-01

Force and Crack Opening vs Time

TUD_ANC-102-02

Force and Crack Opening vs Time

TUD_ANC-102-03

Force and Crack Opening vs Time

TUD_ANC-102-12

Force and Crack Opening vs Time

TUD_ANC-102-14

Force and Crack Opening vs Time

0.1 MPa

TUD_ANC-103-04

Force and Crack Opening vs Time

TUD_ANC-103-05

Force and Crack Opening vs Time

TUD_ANC-103-10

Force and Crack Opening vs Time

TUD_ANC-103-11

Force and Crack Opening vs Time

TUD_ANC-103-13

Force and Crack Opening vs Time

0.3 MPa

Summary

Influence of the level of precompression

Interpretation of the results: influence of precompression and

grout/resin embedment

Summary

A

B

A

A

A

A

a

B

Efficiency of the tested connection typology

Aknowledgements