Parametric study of fully grouted cable bolts subjected to axial loading

2019 ◽  
Vol 56 (10) ◽  
pp. 1514-1525 ◽  
Author(s):  
Danqi Li ◽  
Hossein Masoumi ◽  
Serkan Saydam ◽  
Paul C. Hagan ◽  
Mostafa Asadizadeh
Keyword(s):  
Mechanical Behaviour ◽  
Peak Load ◽  
Axial Loading ◽  
Borehole Diameter ◽  
Initial Stiffness ◽  
Pull Out ◽  
Cable Bolts ◽  
Embedment Length ◽  
Improved Design ◽  
Cable Bolt

The laboratory short encapsulation pull-out test (LSEPT) has been widely accepted as the most efficient method to characterize the mechanical behaviour of cable bolts under axial loading. In this study, a number of LSEPTs was performed on conventional (Plain SuperStrand) and modified (MW9S) cable bolts using the improved pull-out test design. The effects of several parameters including the uniaxial compressive strength (UCS) of the confining medium and grout and the borehole diameter on the mechanical behaviour of MW9S and Plain SuperStrand cable bolts were investigated. Response surface methodology (RSM) was employed to quantify the contribution of these parameters on the responses including peak and residual loads and initial stiffness. RSM revealed that the UCS of the confining medium is a key contributing factor to the mechanical behaviour of both cable bolts. Also, it was demonstrated that the borehole diameter had a negligible impact on the overall behaviour of the MW9S cable bolt while the peak load of the SuperStrand cable bolt was increased due to an increase in the diameter of the borehole. Finally, from a comparative analysis, it was confirmed that the improved design can better represent the field mechanical behaviour of cable bolts through maintenance of the embedment length during large deformation.

Shear strength properties of plain and spirally profiled cable bolts

2015 ◽  
Vol 52 (10) ◽  
pp. 1490-1495 ◽  
Author(s):  
Naj Aziz ◽  
Ali Mirzaghorbanali ◽  
Jan Nemcik ◽  
Kay Heemann ◽  
Stefan Mayer
Keyword(s):  
Shear Strength ◽  
Testing Machine ◽  
Peak Load ◽  
Strength Properties ◽  
Shear Displacement ◽  
Vertical Shear ◽  
Cross Sectional ◽  
Cable Bolts ◽  
Strength Capacity ◽  
Cable Bolt

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The tested cable bolts were (i) Hilti 19 wire HTT-UXG plain strand and (ii) Hilti 19 wire HTT-IXG spirally profiled (smaller cross-sectional area than the plain one) cable bolt, with indentation only on the surface of the outer strands. These cable bolts are of sealed wire construction type, consisting of an outer 5.5 mm diameter wire layer overlying the middle 3 mm diameter wire strands. Both layers are wrapped around a single solid 7 mm diameter strand wire core. The double-shearing test was carried out in 40 MPa concrete blocks, contained in concrete moulds. Cable bolts were encapsulated in concrete using Orica FB400 pumpable grout. Prior to encapsulation, each cable bolt was pre-tensioned initially to 50 kN axial force. A 500 t capacity servocontrolled compression testing machine was used for both tests, and during each test the vertical shear displacement was limited to 70 mm of travel. The rate of vertical shear displacement was maintained constant at 1 mm/min. The maximum shear load achieved for the plain strand cable was 1024 kN, while the spiral cable peak load was 904 kN, before the cable bolt wires began to individually snap, leading to the cable bolt break-up into two sections. It is apparent that spiral profiles of the outer wires weaken both the tensile and shearing strength. Finally, another set of tests was undertaken using the British Standard single-shear approach, producing lower shear strength values.

Experimental Investigation of Adhesive Bonding for Post‐installed Rebars into Concrete at High Temperatures

2019 ◽  
Author(s):  
Thanyawat Pothisiri ◽  
Pitcha Jongvivatsakul ◽  
Vanichapoom Nantavong
Keyword(s):  
Experimental Investigation ◽  
High Temperatures ◽  
Mechanical Behaviour ◽  
Epoxy Resins ◽  
Adhesive Bonding ◽  
Elevated Temperatures ◽  
Adhesive Bond ◽  
Steel Rebar ◽  
Pull Out ◽  
Embedment Length

<p>The use of post‐installed rebars into existing reinforced concrete structures bonded with epoxy resins was constantly increasing due to the advantage of equivalent or even higher bearing capacities at service temperature, compared with conventional cast‐in‐place rebars. Previous studies have examined the effects of different parameters on the mechanical properties of bonded post‐installed rebars at normal temperature. These studies showed that, for rebar diameter equal to 10 mm, the load bearing capacity increases linearly with the embedment length up to 75 mm. However, upon exposure to high temperatures, the glass transition of epoxy resins may occur and affect the mechanical behaviour of the adhesive bond. Studying the mechanical behaviour of an adhesive anchor at high temperatures is therefore necessary. An experimental investigation is conducted herein to examine the characteristics of the adhesive bonding stress between steel rebar and concrete interface at elevated temperatures using a series of pull‐out tests with varying rebar diameters and embedment lengths.</p>

scholarly journals Pull-out and Critical Embedment Length of Grouted Rebar Rock Bolts-Mechanisms When Approaching and Reaching the Ultimate Load

2021 ◽  
Author(s):  
Are Håvard Høien ◽  
Charlie C. Li ◽  
Ning Zhang
Keyword(s):  
Ultimate Load ◽  
Failure Mechanisms ◽  
Concrete Block ◽  
Rock Bolts ◽  
Rock Stratum ◽  
Pull Out ◽  
Deformation Length ◽  
Embedment Length ◽  
Pull Tests ◽  
Grouted Bolts

AbstractRock bolts are one of the main measures used to reinforce unstable blocks in a rock mass. The embedment length of fully grouted bolts in the stable and competent rock stratum behind the unstable rock blocks is an important parameter in determining overall bolt length. It is required that the bolt section in the stable stratum must be longer than the critical embedment length to ensure the bolt will not slip when loaded. Several series of pull tests were carried out on fully grouted rebar bolts to evaluate the pull-out mechanics of the bolts. Bolt specimens with different embedment lengths and water/cement ratios were installed in either a concrete block of one cubic meter or in steel cylinders. Load displacement was recorded during testing. For some of the bolts loaded beyond the yield load, permanent plastic steel deformation was also recorded. Based on the test results, three types of failure mechanisms were identified, corresponding to three loading conditions: (1) pull-out below the yield strength of the bolt steel; (2) pull-out between the yield and ultimate loads, that is, during strain hardening of the steel; and (3) steel failure at the ultimate load. For failure mechanisms 2 and 3, it was found that the critical embedment length of the bolt included three components: an elastic deformation length, a plastic deformation length and a completely debonded length due to the formation of a failure cone at the borehole collar.

scholarly journals Mechanical Behavior of Sandwich Panels with Hybrid PU Foam Core

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Xudong Zhao ◽  
Li Tan ◽  
Fubin Zhang
Keyword(s):  
Failure Modes ◽  
Peak Load ◽  
Hard Core ◽  
Experimental Results ◽  
Control Panel ◽  
Foam Core ◽  
Initial Stiffness ◽  
Composite Sandwich ◽  
Pu Foam ◽  
Compression Area

The traditional composite sandwich structures have disadvantages of low shear modulus and large deformation when used in civil engineering applications. To overcome these problems, this paper proposed a novel composite sandwich panel with upper and lower GFRP skins and a hybrid polyurethane (PU) foam core (GHP panels). The hybrid core is composed of different densities (150, 250, and 350 kg/m3) of the foam core which is divided functionally by horizontal GFRP ribs. The hard core is placed in the compression area to resist compressive strength and improve the stiffness of the composite sandwich structure, while the soft core is placed in the tension area. Six GHP panels were tested loaded in 4-point bending to study the effect of horizontal ribs and hybrid core configurations on the stiffness, strength, and failure modes of GHP panels. Experimental results show that compared to the control panel, a maximum of 54.6% and 50% increase in the strength and bending stiffness can be achieved, respectively. GHP panels with the hybrid PU foam core show obvious secondary stiffness. Finally, analytical methods were proposed to predict the initial stiffness and peak load of the GHP panels, and the results agree well with experimental results.

Experimental and numerical investigation on failure behavior of ring joints in precast concrete shear walls

2019 ◽  
Vol 23 (1) ◽  
pp. 118-131
Author(s):  
Jian Zhou ◽  
Xudong Zhi ◽  
Feng Fan ◽  
Anliang Jiao ◽  
Hongliang Qian
Keyword(s):  
Bearing Capacity ◽  
Precast Concrete ◽  
Critical Role ◽  
Axial Loading ◽  
Shear Walls ◽  
Yield Ratio ◽  
Failure Behavior ◽  
Displacement Ductility ◽  
Failure Patterns ◽  
Pull Out

Precast shear wall structures have been widely used due to their outstanding features, and the joints between precast members play a critical role in complete structures, specifically for vertical joints. The ring joint is a new connection method used for the vertical connection. Few studies and related regulations were traced; therefore more detailed studies are required. In order to study the anchoring performance and failure behavior, an experimental model was designed and tested under monotonic axial loading, taking the composite height of ring rebars, concrete specifications, diameter of the horizontal rebars, relative position of the ring rebars, diameter of the ring rebars, and number of horizontal rebars into consideration. The failure phenomena were observed and the data were collected. The failure pattern, bearing capacity, yield ratio, displacement ductility coefficient, and other performance parameters were analyzed. The study indicated that the failure patterns are divided into ring rebar pull-out and ring rebar fracture. Increasing the composite height of the ring rebar, the concrete specifications and the number of horizontal rebars could improve the bearing performance, and the contribution of the horizontal rebar diameter was limited, and interlocking ring rebars arranged uniformly are not optimal. In the case of joint failure, the yield ratio is relatively small and the displacement ductility coefficient is larger, which shows the bearing capacity reserve is better. A numerical model was established to analyze the internal behavior, and the results were in good agreement with the experimental results, important for us to understand the failure behavior. Design recommendations will promote its application.

Column design methods for timber engineering

1985 ◽  
Vol 12 (4) ◽  
pp. 731-744 ◽  
Author(s):  
Andrew H. Buchanan ◽  
Kenneth C. Johns ◽  
Borg Madsen
Keyword(s):  
Axial Loading ◽  
Design Methods ◽  
Ductile Material ◽  
Experimental Program ◽  
Canadian Universities ◽  
Design Charts ◽  
Column Design ◽  
Improved Design ◽  
Timber Engineering ◽  
Elastic Brittle Material

Combined bending and axial loading is often encountered in lumber and timber members. Existing design methods are based on studies carried out many years ago, and are no longer appropriate because they do not recognize that wood with defects behaves in compression as a nonlinear ductile material and in tension as an elastic brittle material subject to size effects.This paper summarizes the findings of a comprehensive investigation into the behaviour of lumber subjected to eccentric axial loading, which was carried out at two Canadian universities. The study included analytical modelling and an extensive experimental program using full-size lumber.The results of the investigation have been used in this paper to propose improved design methods, using design charts and approximate formulae for in-plane behaviour. The discussion is extended to general loading cases and biaxial behaviour. Input information required for the design process is also discussed.

Pull-out capacity of single batter piles in sand

1986 ◽  
Vol 23 (3) ◽  
pp. 387-392 ◽  
Author(s):  
A. M. Hanna ◽  
A. Afram
Keyword(s):  
Design Method ◽  
Soil Mechanics ◽  
Earth Pressure ◽  
Axial Loading ◽  
Test Results ◽  
Passive Earth Pressure ◽  
Sand Soil ◽  
Pull Out ◽  
Batter Piles ◽  
Good Agreement

The pull-out capacity of single rigid vertical and batter piles in sand and subjected to axial loading has been investigated. Good agreement was found when test results on instrumented model piles were compared with theoretical estimates. The effect of pile inclination on the pull-out capacity has been explained by means of variable mobilized passive earth pressure on the pile's perimeter. A design method and charts are presented. Key words: pile foundation, pull-out capacity, vertical pile, batter pile, sand–soil mechanics.

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