Strengthening and Restoration of the Stone Building

5506 words (22 pages) Dissertation

16th Dec 2019 Dissertation Reference this

Tags: Architecture

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    1.  Strengthening and Restoration the Stone Building

(Dakanali et al. 2016) investigated the pull-out of titanium bars phenomenon from marble block and to figure out what is the mechanical behavior before and during pull-out the phenomenon. The author studied this phenomenon by two ways, experimentally work and using the results for analysis of numerical models. Many types of studies focused on this phenomenon and the behavior of pull out the titanium bars by using traditional techniques to get the results from the experimental test. In this study, the big difference from other studied is using the developed techniques to record the displacement, strain load for bars, mortar, and marble blocks. The materials used in this study were threaded titanium bars, Dionysos marble, and cementitious material. The marble blocks used three different dimension specimens (A=100*100*150 mm), (B=200*200*200mm), and (C=200*300*200mm), all these specimens were drilled in central the block marble, and the diameter of the hole is (14mm), and the anchoring length of the bar is (75mm). The diameter of threaded titanium bars used (11mm) by the single bar for each specimen. The cementitious material was a binder and water without any aggregate. The load, the displacement, the axial strain of bar and relative slip concerning marble all these quantities recorded by using experimental techniques during the test.  The author figured out that the weak link between (marble-cement-bar) is marble-cement interface fail and leading to failing the whole structure, but the cement-bar interface does not fail during whole loading.

(Kourkoulis, Mentzini, and Ganniari-Papageorgiou 2010) studied the mechanical behavior of fractured marble architraves for both experimental test and numerical analysis. The purpose of study provided more information and to get a clear idea of a whole system its behavior under bending load, and lead to provide great estimating the location of the failure and the weak place for the whole system (marble, reinforcing bars, cementitious materials). The experimental part included two elements of marble epistyle to the connection by using reinforcing bars with cementitious material and test this model by apply bending load in the top of the model as a uniformly distributed load. The reinforcing bars used titanium bars as three layers (two bars at each layer), the distances between these layers are 7, 20 and 30 cm from the bottom side of the marble block. The size of marble block was (length=1.43 m, height =0.45 m and width =0.18m). The maximum load that causing yielding for the bottom layer of titanium bars is 480 KN, the crack recorded between two parts of marble after applied load 115KN and increasing until 330 KN; the crack was ¾ of the height of marble. For the numerical analysis part, based on the Finite Element Method to study in a parametric manner the factors influencing the behavior of the marble. The most critical part of this study was cementitious materials and marble and should develop this part to avoid any failure.

(Osofero, Corradi, and Borri 2014) compared the treated and untreated surface of the titanium bar for investigation the behavior and increase of bond strength. The experimental tests were used to pull out the titanium bars from prisms of mortar. Different kinds of treated surface of titanium bars used in this study which are (Sandblasting, Knurling, Alkaline Etchant, and Ring application). The goal to use the surface treatments of titanium bars is to increase the bond stress and compare these result with untreated titanium bars. The mechanical properties of titanium bars were (tensile strength (361.1 MPa), yield stress (271.2 MPa), and Young’s modulus (112.7 GPa). The author used the hydraulic lime, sand, and water -reducing admixture for construction the mortar. The dimension of mortar prism was (25x25x30 cm) with a hole in the middle of the prism for groove the embedment of the titanium bars by using epoxy resin and a cement -based mortar. In this research, the author tested 59 test specimens by using variables of length of embedment between (100 and 310 mm), groove size, bar diameter, and the surface of titanium bars. The numbers of specimens were using treated bars 36 specimens and untreated bars 23 specimens. The results of this study were sufficient interest especially for the treatment surface of titanium bars when compared to the untreated bar because the experimental tests showed that the treated bars have higher bond strength especially by using epoxy resin. The high value of bond strength for untreated bars was (0.55 MPa), but form treated bars was(10.5MPa). Two possible modes of failure from untreated bars identified: pull out the failure of the bar and mortar carrot. The knurling type of treatment surface showed high average bond strength was about (1.1 MPa) and for the smooth surface was about (0.41 MPa), These results for 19 mm diameter bar and 300 mm embedment. The ring application with 25 mm diameter of the bar and 300mm embedment length showed the high average bond strength was about (1.3 MPa) and smooth bars was about (0.21 MPa) for same size and length of the bar. All types of treatment surface for titanium bars increase the bond strength regardless any types of groove adhesive, and smooth surface showed low bond strength.

(Zambas, Ioannidou, and Papanikolaou 1986) tested two types of experimental work by using anchor titanium bars joint two part of marble stone, and their investigation was especially on the Acropolis monuments by restoration of marble architectural members. The white Portland cement was used for both tests as grouted the titanium bars into the fragment of marble. The authors used the titanium bars and substituted the stainless steel because of its corrosion resistance is very high and lead this change to prevent any collapse of historical parts of the building that used the stainless steel. The pullout test and bending test have been investigated to figure out the behavior and design the titanium reinforcement bars. For pullout test, the size of titanium bars tested were 10mm and 16mm with a variable length of bonded bar for both sizes (10, 15, 20 cm). Two strain-gauges have been used on each end of the specimens to record the slip and used a load cell to record the applied load on the specimens during the test. The result from the pull-out test of 16 mm size of titanium bars, the failure happened at the marble. For the bending test, the size of titanium bars used in this test 8,10,12, and 16 mm and the hole diameter in marble larger 4 mm from the diameter of bars one layer. Four models used to apply bending load for each model using two bars to join two part of fragment marble (h=20cm, b=15cm, L=50cm) for each part. From this test, there is a relationship between bending moment and vertical deflection for all the specimens, and from the model used bar 10, 12 mm have more resisting for bending load and about 500, 600 km. The result of this experimental investigation for both pull out, and bending test found that the bond strength of reinforcement of titanium bars was noteworthy and the relationship between the force or moment with the deflection kept linear before the failure reached marble parts

  1. Strengthening and Restoration the Masonry Building

(Gigla and Wenzef 1997) studied the reform the historical structural especially the masonry buildings by using the injection anchors to connect two elements of building such use this technique in columns, beams, slab, and foundations. The goal of this study was to figure out the behavior of pull out anchor system from inside masonry or stone block and design the recommendation of injection anchors. The author studied this research by experimental work to investigate the aim of the research. The materials used in the study were natural stones, brick masonry, cement as grout material, steel bars as anchors element. Three different types of stones (Travertine fc min=20 MN/m2, Soft sandstone fc min=30 MN/m2, Hardstone fc min=50 MN/m2, and Granite fc min=120 MN/m2), with differences of dimensions range (width 70-100 cm, height 100-130 cm, and thick 25-50 cm). The grout materials used (trass cement, trass-lime, Portland blast furnace slag cement, and Portland cement, the hole diameter used 20mm. The cold strained stainless reinforcing steel and stainless threaded rods bars used two sizes of diameter 16, 56 mm. There are 25 specimens tested, and pull out force in this research, the length of bond bars was 50-250 mm. After testing all specimens, the most part which measured is the displacements between the steel bar and the mortar, and the model of failure after pulling out the bars. The result showed that the bond length for both 150mm, 250mm identified applied the maximum tensile strength without any failure. The poor bond length was 100mm because the mortar/ stone interface failure occurred. The maximum pullout force was 59.39 KN from bond length 251mm by using water cement ratio (w/c=0.66), the minimum pullout force was 2,88 KN from bond length 51mm and water cement ration w/c=0.66. The result showed that shear strength was a higher value from high bond length before the steel/mortar interface failure model occurred. This study showed that the length of the bond is very important to resist the anchor any pullout force and suggest that the 150-mm bond length more sufficient length of the anchor in a historical building.

(E. Giuriani, G.A. Plizzari 1995) investigated by strengthening the historical building especially masonry by using the technique of anchors to increase the tensile strength of masonry structural. Experimental test evaluated this technique by made smaller masonry wall as used in historical building and pull out the anchors from inside the wall with different types of grout materials. The goal of this research was to figure out the behavior of the pull-out anchor’s system from the historical building and help the experimental results of the test to design recommendations the anchor’s system to increase the strengthening of historical buildings. The materials used in this research were cementitious materials with a different value of the water-cement ratio, steel bars, masonry walls. Mape-Antique is a hydraulic of bonding material used w/c ratio =0.40, Micro-lime 900 is a mixture of bonding material without cement used w/c ratio = 0.30, Grout Flow R is a natural hydraulic lime without soluble salt used w/c ratio = 0.6, and Macflow is an expansive cement with superplasticizer used w/c = 0.32, all these used as grouting materials. All these cementitious materials tested to evaluate the mechanical properties and the compressive strength and flexural strength measured. The mechanical properties of steel bars were C40 and yield strength (630 MPa), the bond length was 500 mm, the total length of the bar used in all specimens was 1000 mm. The specimens of masonry walls used three specimens built in the laboratory place used new bricks and low-strength hydraulic lime mortar. The results of the test showed that all specimens which 11 tested pull-outs from three masonry walls different failures without any failure in the steel bars. The most effective factor to achieve maximum pull-out force was the type of grout material and water cement ratio. The maximum tensile forces were (167.99 KN, 171.87 KN) got from a specimen that used Micro lime 900 grout and Maflow grout. On the other hand, the minimum tensile forces were (37.21 KN, 43.72 KN) got from specimens that used grout flow R. the Maflow grout showed high bond stress before occur any failure which the maximum bond stress was (3.65 MPa), also from Micro Lime 900, which was (3.57 MPa). From these results, the best grout material that has sufficient bond the anchor’s bars with masonry element were Maflow, and Micro Lime 900, the water cement ratio for these cementitious materials were (0.32, 0.3 respectively), which means lower w/c ratio lead to a great bond for anchors system.

(Gigla 1999)  studied the behavior injection anchors inside the historical monuments to developing the strengthening resistance of this structures by increasing the tensile force for masonry or stone element. The goal of the research is investigating the bond stress of the injection anchors to retrofit the historical building. Five pull out tests evaluated experimentally by using stainless reinforcing steel (BSt 500/500 NR) and threaded rods (M12)with 12 mm diameter, the grout material was CEM I 42.5 R-HS/NA with water cement ratio equal (0.8) and the bond length was inside the stone and bed joint was 200 mm, five specimens of stone used from Welleringhausen church. The results of the research were very interesting; the maximum tensile pullout force was 59.4 KN, the high bond stress was 7.9 N/mm2, with displacement design was 0.40. These results showed that all injection anchors inserted into bed joint have lower pullout force with higher displacement. The author evaluated the bond strength by using three different methods, geotechnical standards according to European standard,  a Representative diagram of structural failure, and bond strength at defined displacement. All these methods showed that the most important thing to evaluated the behavior injection anchors is the displacement, without measured the displacement can not good estimate the behavior of the system

(Algeri et al. 2010) worked on figure out the standardized methodology to using the injection anchors in the ancient building especially which built by use masonry blocks. The author suggested to use the experimental results as a guideline for this type of technique to repair the historic building. The injected anchor with sock inserted inside masonry wall which the technique used in this study and apply pull out tensile force, the grout material filled during injection as gradually. Two kinds of grout materials used in this research which cement based BCM Hs, the mechanical properties have been evaluated after 28 days of curing and were (Cement 74%, Additives 5%, Inert material 21%, Water/binder ratio 26%, and Compressive strength 55 MPa), the second material was lime based BCM Ls with mechanical properties (Lime 68%, Additives 5%, Inert material 27%, Water/binder ratio 24%, and Compressive strength 12 MPa). The diameter of drilled hole was 3 times the diameter of bar and bond length was 2/3 thickness of the wall with diameter 20 mm of steel bar. The dimension of masonry wall specimens was (2×1.7×0.75 m) as two masonry walls and using brick masonry and stone masonry and joint mortar to build them in the laboratory. The results showed that four mechanisms of failures occurred for each type of grout material, the failure models (adhesion happened between the injected mortar and borehole surface, steel bar and mortar, surrounding masonry tensile, and the steel failure).

  1. The anchorage system
    1.    Pull-out from Stone

(Marinelli et al. 2009) studied the pull out phenomenon from marble block stone and to design the criterion of pull out bars from stone. In this study, the investigations were based work the experimental tests to pull out the reinforcing steel bars from the element of marble model and using the result of experimental work to design the standard of pull out problem based on the numerical method. The research has been done in two parts, the experimental part, and the numerical part and with depended on previous researches. The most previous researches have been studied the pull out bars from a fragment of marble block, but for design the criterion,  there aren’t studies enough that focus on and cover this part. The materials used in the experimental test were marble, mortar, and reinforcement steel and tested each of them to figure out the properties of materials which are very important to use them in the second part of this research (the numerical method). The marble specimens, designed from Parthenon temple by working with the staff of engineers were working on a restoration project of the Parthenon temple. The mechanical properties of specimens measured in this research (Elasticity modulus, E (Gpa for strong =84.5, weak=50), Poisson’s ratio for strong=0.26, weak=0.11), and Tensile Strength (Mpa) for strong=10.8, weak=5.3). The specimens of marble block dimension which used in this paper were the cross section constant by (80*80 mm), and the length of specimens was various (120, 160, 200, 240 mm). Most of the previous researches used the titanium alloys bars to rejoined two fragments of marble which be such beam, column, or another part of the historic building because it is the very high resistance to corrosion. In this study, the author used the reinforcing bars made from high strength steel. The diameter of the reinforcing bar is 12mm, but there three different values to thread depth 1.75, 1.25 and .75mm. The thread pitch of the reinforcement bars used 2,3, and 4 and the series of test were nine (each value of thread pitch tested three times), and the anchoring length was various between (110 mm and 150mm). The cementitious material used as the mortar and the material properties of the cementitious material was (E~15.5 Gpa, v~0.26, stress ~10MPa, ultimate stress~ 35 Mpa). The most failure which observes after applied loading was the pull out the steel bars-mortar from marble hole with some fracture on the top face of marble. The reason for this failure is because the embedment length used between (110mm to 150mm). The relationship between applied load and the displacement of the system was almost linear at the beginning of loading until reach at the peak load. The author found the thread’s pitch effected on the load applied, which found that by increasing the thread’s pitch, the decrease the applied load. The pullout force decreased from 40 KN for thread pitch p=2mm with thread depth h=1,25mm to 21.5 KN for thread P=2mm, but the deeper threads (h=1.75mm), the pullout force does not affect with change the thread’s pitch, for p=2mm, 3mm, and 4mm, the pullout force was 21.2, 16.5, and 23.0 KN respectively. The second part of this study was designed criterion based on the experimental result in the first part. There are two bilinear behavior models of the description of the behavior of connection between the system (marble-mortar-bar) according to the experimental work: slip increasing with constant the applied load for intense pitches, and linearly increasing load versus slip for jagged pitches. The medium depth of thread’s pitch was found very great to carrying out the load applied.

(Contrafatto and Cosenza 2014) researched by experimental test (laboratory testing) and numerical analysis model (simulations with finite element software) the behavior of chemically bonded anchoring system in three different types of natural stone. The materials used in the experimental work were stones, steel bars, and epoxy resin. Three types of natural stone investigated, the sandstone blocks with size (15 x25 x 45 cm3), the basalt blocks with irregular shape and dimension between (20 x20 x40 cm3 to 30 x 40 x 60 cm3), and limestone blocks with irregular shape and dimension between (20 x 30 x 40 cm3 to 40 x 40 x 60 cm3). The mechanical properties of all these types of stone were evaluated which for Sandstone ( Uniaxial tensile strength= 1.5 N/mm2, Uniaxial compressive strength= 20 N/mm2, Young modulus E= 12,309N/mm2, and Density=14.3 KN/m3 ), Basalt (Uniaxial tensile strength= 50 N/mm2, Uniaxial compressive strength= 500 N/mm2, Young modulus E= 50,000N/mm2, and Density=30 KN/m3 ), and Limestone ( Uniaxial tensile strength= 15 N/mm2, Uniaxial compressive strength= 220 N/mm2, Young modulus E= 19,616/mm2, and Density=26 KN/m3 ). The mechanical properties of the threaded steel bar which used in this study were tensile strength 400 N/mm2 and yield strength 240 N/mm2, by using three diameters (10, 14, 20 mm). The embedment length of the bar was three different depths (3, 5, and 10 times the bar diameter of the steel bar. The author used the epoxy material as adhesion anchor into the stone that is because the epoxy resin characterized by a great strength and adhesion than other material such vinyl ester resin or polyester, the epoxy resin hardening is about ten times greater from other. The Hilti RE-500 epoxy resin type used in this study. The pullout force applied after inserted the bar into the stone, 81 specimens tested by different the stone, diameter of the bar, and embedment depth. The pullout force- displacement curve for different embedment depth, diameter bars (10, 14, 20 mm) evaluated. The results identified that the failure of the mechanism of yielding of the bar for the length of anchor equal to five or ten times the diameter at two types of stone are basalt and limestone. The embedment depth equal three times diameter of bar showed the stone cone failure. For all results of sandstone specimens, showed all failures were stone cone failure, only coupled with sliding at stone/ resin interface. For basalt stone and limestone, the minimum embedment length of anchor should be range 3-5 diameter bar, but for the sandstone, the minimum embedment length of anchor should be ten times the diameter bar. The mechanical behavior was very similar to both basalt and limestone, but the sandstone was very weak pull out strength. The second part of this study is a numerical analysis based on the data from the experimental test; the author used the previous studies which modeling of chemical anchors in concrete for the stone to evaluate the strength prediction for all three types of stone. There are nine models of failure which the author work on them were: –

Model 1 is an elastic bond-stress model.

Model 2 is a uniform bond-stress model.

Model 3 is a uniform bond-stress model with the real resistance of adhesive.

Model 4 is a bond models neglecting the shallow concrete cone.

Models 5 is combined cone-bond models.

Model 6 is combined concrete cone/bond model elastic.

Model 7 is based on the sliding at the adhesive/concrete interface.

Model 8 is based on the sliding at the steel/adhesive interface.

Model 9 is a concrete cone model.

According to these models, calculated the predict the strength of the bonded anchors in the stones. In conclusion, by compared the resistance of anchorage system between concrete and stone, the result of numerical analysis and experimental test of basalt and limestone were higher except the sandstone show opposite result.

  1.    Pull-out from Concrete

(Zamora et al. 2003) studied the behavior of single grouted anchors under a tensile load, and design by developing the rational design procedures. Two types of anchors tested in this study, headed and unheaded anchors by installing into a hole in hardened concrete. The six cementitious materials used as grouted for both unheaded and headed anchors with hole diameter 50% larger than the anchor diameter, and using three types of polymer grouts with unheaded anchors. This study was tested 237 tension tests for both headed and unheaded anchors by using cementitious material and polymers materials for grout. The experimental tests were divided into two parts: a test of headed grouted anchors and unheaded grouted anchors. Each type of anchor has been used six cementitious material of grout and three polymers of grout. For both parts, used the diameter of bars (12.7, 15.9, 19.1, 25.4 mm), the bond lengths were (102, 114, 127,152 178 mm), and the compression strength of concrete (f’c)were between (27.6 to 49.9 MPa). The hardened concrete which used in this research project was 1220 mm width,2440mm length, and 380mm depth with minimum reinforcement to avoid any cracking during the test. The results of test unheaded grouted anchors showed that the bond failure located at steel/grout interface with the shallow concrete cone, this is the most series of test for this type of anchors showed the steel/grout bond failure. The second failure was steel/concrete bond failure identified for large diameter of bars. Lower average bond stress was (7.3 MPa) and the higher average bond stress was(22.8MPa). In general, the group of grouted anchors that used cementitious material showed high bond stress. The grout/concrete interface of bond failure identified from headed grouted anchors which 65 tests from 113 tests (57.5%), another failure was a concrete tensile failure which 48 tests (42.5%). The lower average bond stress was (4.8 MPa) and the higher value was(11.1MPa). The behavior model has been used to develop the grout/concrete of headed anchor and steel/grout bond failure was uniform bond stress model, and for the concrete tensile failure was Concrete Capacity Design (CCD) method. In conclusion, according to these results of experimental tests, there are three equations which authors developed to design bond strength for unheaded anchors (steel/grout and grout/concrete) and headed anchor (concrete breakout strength). This recommendation for bond anchors into Appendix D of ACI318.

(Wang et al. 2016) investigated for the behavior design of post-installed large diameter anchors in concrete. In this research, the materials which used were two types of steel bar treatment surfaces (grooved bars, plain bar), the nominal diameter bars were four sizes (36, 48, 90, 150 mm) and three different of embedment depths (8, 10, 12 times the bar diameter). The block concrete was grade C25 (Compressive Strength 23.5 MPa, Tensile Strength 2.2 MPa, Young’s modulus 28 MPa, Poisson ratio .2, Density 2.5E+03 Kg/m3). Two types of materials of grout used, the flowing grout (Bond Strength 12.3 MPa, Compressive Strength 55 MPa, Water cement ratio 0.25) and Hilti RF-500 epoxy resin (Bond Strength 15.4 MPa, Compressive Strength 120 MPa) as the Anchorage agent and grout the steel bars inside the concrete block. After tested these anchors, the results showed that three types of failure where occurred for both flowing grout and epoxy resin grout were similar, steel pullout failure, concrete damage failure, and combined cone damage failure. The result indicated that the surface type (groove, plain), the Anchorage agent, the embedment depth, and bar diameter were the effect on the deformation capacity of the anchor bars. The grooved bar anchors interduces there was more ductility than plain bars anchors which mean the grooved bar anchors has pulled out load capacity from the plain bar anchors. The bond stress of flowing grout is lower than the bond stress of epoxy resin because this reason the result showed that flowing grout has more slipping between bars and Anchorage agent. Higher deformation capacity which indicated from increasing the embedment depth of the bar anchors with increasing the diameter of bars also. The deformation capacity of the bar anchors is regardless flowing grout, or epoxy resin grout was found between 0.5mm and 2.5 mm. The author used the equation (τ=Nμ/ (πdh_e f)) of average bond stress by assumed the bond stress along the anchorage section is uniformly distributed to calculate the bond stress for both plain and grooved bar. The results of the average bond stress by using the flowing grout both grooved and Plain surface of the bar were 7.54 MPa, 4.12 MPa respectively, which is average bond stress for grooved showed higher that plain bar. The result of the average bond stress by using epoxy resin for both grooved and plain bars were 8.89 MPa, 5.16 MPa respectively, which is average bond stress for grooved showed higher than a plain bar. Overall of these results of the bond stress, the grooved treatment surface bars have high bond stress from plain treatment surface bars both flowing and epoxy resin grout. According to these values, the author designs the modified equation for large diameter bars. The author in this study develop the design concepts for large diameter bar anchors based the previous studies and the results of this test by modified the rational design equation for the post-installed bar, and the models of failure (concrete annulus damage model, combined cone damage model). The conclusions from this research provided four main points; the first point is that the tensile capacity dependent on the bar diameter, the anchorage agent, the bar surface type, and the length of embedment depth. The second point is by using large diameter, and deep embedment depth bar, increasing the fraction area and increasing the pull out the load capacity. The third point is, in general, the epoxy resin grout with higher bond strength showed a great behavior than the flowing grout. the last point is by using epoxy with grooved treatment surface of bar indicate the best behavior and performance for higher tensile capacity and higher deformation capacity.

(Yilmaz, Özen, Yardim, 2013) studied the pullout of behavior post-chemical anchors by using low concrete blocks. The author compared the experimental results with ACI 318 by measured the load capacities of post-anchors. the compressive strength of concrete which used in this study was (C5= 5.9 MPa, C10= 10.9 MPa). Three different sizes of diameter bars were (12, 16, 20 mm), and the bond length of bar and for free-edge distance were chosen according of diameter of bar were (10, 15, 20) time the diameter of bar. the yield strength of steel bars was (457-522 MPa), the tensile strength was (583-626 MPa). In this study, the material used to adhesion the bar with concrete epoxy resin has 16.9 MPa for tensile strength and 69.5 MPa for compressive strength. The results of the experimental tests showed the embedment depth and free edge 10 times the diameter bar not recommend to use because most of cases the brittle failure models have been occurred, on the other hand, the edge distance and embedment depth was 20 times diameter bar inducted steel yielding before pullout. The most recommend in this study was using the edge distance and embedment depth about 20 times diameter bars with develop the steel bar has higher tensile strength, and to obtain ductile behavior for all elements should use the lower diameter of anchors bars.

(Epackachi et al. 2015) studied the behavior of adhesive anchors by apply tension load and shear load and compared the result with the prediction strength of adhesive anchor in ACI 318-14 for both single and group anchors. The experimental work included 42 specimens of the test as single anchors and group of 4, 6, 9 anchors and the bond length 200 mm for all specimens. The adhesive anchor inserted inside concrete reinforcing blocks using epoxy resin and mechanical properties of concrete block was grade C35/45, w/c=.04. The mechanical properties of steel bar anchors were 640 MPa for nominal yield tensile strength and 800 MPa for ultimate tensile strength, the diameter of threaded rod 20 mm. The experimental test was two parts. First one for tension load included a single anchor and three groups of anchors (2×2, 2×3, 3×3) each group used spacing (150, 200 mm), same design group for the shear test. The results of tension test indicated four failure models which concrete cone failure, Bond failure, Steel failure, and Splitting failure. The steel failure model indicated only in one anchor for single anchor test with the maximum tensile capacity (198 KN) when compared with other single anchors, the maximum deformation capacity 5.3 mm for the same anchor. For all groups test of anchor were (4, 6, 9) the models of failure were concrete cone plus splitting failure. The group of anchors (4) showed the concrete failure only. The maximum average tensile capacity indicated from a test of group 9 anchors used 200 mm spacing was (857 KN) with 0.95 mm average deformation capacity and the minimum average tension capacity (185 KN) with average deformation (3.7 mm indicated from a test of the single anchor. For the shear tests, the results indicated three types of failure models, steel fracture at grout-steel plate interface, deformation anchor, and steel fracture at the grout-concrete interface. The maximum average shear strength showed from group(9) anchors with 200 mm spacing which was 1085 KN with average deformation capacity was 12.1 mm. According to ACI 318-14, the author compared the results of the experimental test with predicted tensile equations for three failure models of tension and shear test for both single and group anchors. The result of comparison with ACI 318-14 indicated that the tension and shear strength capacity of group anchors underestimated from ACI 318-14 provision.

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