136 results found
Abu-Salma D, Vollum R, Macorini L, 2021, Design of biaxially loaded external slab column connections, Engineering Structures, Vol: 249, Pages: 1-16, ISSN: 0141-0296
The paper investigates the influence of biaxial loading on punching resistance at square and elongated edge columns of flat slabs which is virtually neglected in the literature. In the absence of experimental data, the influence of biaxial loading is determined using nonlinear finite element analysis (NLFEA) with 3D solid elements. The resulting baseline punching resistances are compared with the predictions of various implementations of the Critical Shear Crack Theory (CSCT) including a Joint Shell Punching Model (JSPME) in which punching failure is simulated using nonlinear joint elements inserted between the nodes of nonlinear shell elements located around the punching control perimeter. The failure criterion of the JSPME, which is most suited for structural assessment, implicitly accounts for the effect of biaxial loading unlike the original (classic) and closed form versions of the CSCT. The classic CSCT indirectly accounts for loading eccentricity by reducing the punching control perimeter by a multiple ke which is determined in this paper using shear field analysis. Conversely, the closed form CSCT, which is adopted in the draft for the next generation of Eurocode 2 (EC2), enhances the design shear force by a multiple β. The paper uses experimental data to determine an expression for β for edge column connections subject to inwards eccentricity normal to the slab edge. Subsequently, shear field analysis on representative flat slab to edge column connections is used to extend this expression for β to edge column connections subject to biaxial eccentricity. NLFEA simulations with 3D solid elements are used to validate the predictions of the JSPME, the shear field methodology used to determine ke in the classic CSCT and the proposed expression for β in the closed form CSCT. Reasonable agreement is achieved between all these analysis methods. The main advantage of the JSPME over NLFEA with 3D solid elements is its increased computational effic
Setiawan A, Vollum R, Macorini L, et al., 2021, Numerical modelling of punching shear failure of RC flat slabs with shear reinforcement, Magazine of Concrete Research, Vol: 73, Pages: 1205-1224, ISSN: 0024-9831
This paper utilises non-linear finite-element analysis with three-dimensional (3D) solid elements to gain insight into the role of shear reinforcement in increasing punching shear resistance at internal columns of flat slabs. The solid element analysis correctly captures the experimentally observed gradual decrease in concrete contribution to shear resistance with increasing slab rotation and the failure mode but is very computationally demanding. As an alternative, the paper presents a novel approach, in which 3D joint elements are combined with non-linear shell elements. Punching failure is modelled with joint elements positioned around a control perimeter located at 0.5d from the column face (where d is the slab effective depth). The joint elements connect the nodes of shell elements located to either side of the punching control perimeter. The punching resistance of the joints is related to the slab rotation using the failure criterion of the critical shear crack theory. The joint-shell punching model (JSPM) considers punching failure both within the shear-reinforced region and due to crushing of concrete struts near the support region. The JSPM is shown to accurately predict punching resistance while requiring significantly less computation time than 3D solid element modelling.
Abu-Salma D, Vollum RL, Macorini L, 2021, Modelling punching shear failure at edge slab-column connections by means of nonlinear joint elements, Structures, Vol: 34, Pages: 630-652, ISSN: 2352-0124
This paper is concerned with the modelling of punching shear failure at edge columns of flat slabs without shear reinforcement. Punching failure at edge columns is much less researched than at interior columns despite typical buildings having more edge than interior columns. The paper uses nonlinear finite element analysis (NLFEA) to study the influence on punching resistance of parameters including column aspect ratio and loading eccentricity. The NLFEA is carried out using both 3D solid elements and a Joint Shell Punching Model (JSPM) which combines nonlinear shell elements with nonlinear joint elements that incorporate the failure criterion of the Critical Shear Crack Theory (CSCT). Both constant and varying loading eccentricities are investigated since near failure eccentricity at edge column connections typically reduces below that calculated with elastic analysis due to moment being redistributed from the support to span. This reduction in eccentricity is beneficial since punching resistance is shown to depend on the final loading eccentricity. Consequently, designing for punching on the basis of elastic edge column moments is overly conservative.
Elwakeel A, Vollum R, 2021, Shear enhancement in RC cantilevers with multiple point loads, Magazine of Concrete Research, ISSN: 0024-9831
The shear resistance of reinforced concrete beams is enhanced by arching action when loads are applied to their top face within around twice the beam effective depth (d) of supports. Previous experimental investigations into shear enhancement have almost exclusively considered simply supported beams with single-point loads applied within 2d of supports. Such academic tests are unrepresentative of practice where loading and support conditions are usually more complex. For example, balanced cantilever cross-head girders of bridges and continuous beams can have multiple point loads applied to the flexural tension face within 2d of supports. Such cases have not previously been investigated experimentally. The paper describes an experimental program carried out to investigate shear enhancement in balanced cantilever beams subjected to pairs of concentrated loads within the failing shear span. The shear resistance of the cantilever beams was found to be slightly less than matching simply supported beams, with the difference greatest for beams without shear reinforcement. A strut and tie model is developed for cantilever beams with pairs of concentrated loads applied to the tension face within 2d of the supports. Measured beam strengths are also compared with the predictions of BS 8110, EC2, fib Model Code 2010 and nonlinear finite element analysis.
Elwakeel A, Shehzad M, el khoury K, et al., 2021, Understanding the cracking behaviour of reinforced concrete elements subjected to the restraint of imposed strains, fib Symposium 2021, ISSN: 2617-4820
Riedel K, Rust G, Vella JP, et al., 2021, Laboratory testing of a novel M-Frame precast beam-to-beam moment resisting connection, 2021 fib Symposium, ISSN: 2617-4820
Abu-Salma D, Vollum R, Macorini L, 2021, Punching shear in edge slab-column connections, fib Symposium Lisbon, ISSN: 2617-4820
Oliveira FGBS, Soares LFS, Vollum RL, 2020, Design considerations on the influence of slab continuity on punching resistance of flat slabs, IBRACON Structures and Materials Journal, Vol: 13, Pages: 1-20, ISSN: 1983-4195
This paper assesses the influence of slab continuity on the punching resistance of a realisticallyproportioned flat slab floor plate without shear reinforcement. The edge column punching resistance ofa symmetric flat slab extending bays in each direction was assessed by means of NLFEA with TNODIANA, MC2010 levels II, III, IV, Eurocode 2 and NBR 6118. Both Eurocode 2 and NBR 6118 areseen to give similar predictions for punching resistance, while MC2010, which is based on the CriticalShear Crack Theory and depends on how rotations are calculated and FE modelling assumptions, variessignificantly with its levels of approximation with Level IV agreeing reasonably well with predictionsfrom NLFEA. Direction for the critical rotations is shown to vary and can also be influenced by thereinforcement over the span. For EC2, NBR 6118 and MC2010 LoA II and III punching shear designare independent of span, unlike the results obtained with MC2010 LoA IV.
Setiawan A, Vollum RL, Macorini L, et al., 2020, Punching of RC slabs without transverse reinforcement supported on elongated columns, Structures, Vol: 27, Pages: 2048-2068, ISSN: 2352-0124
The paper investigates the influence of support elongation on punching resistance at internal slab column connections without shear reinforcement. Nonlinear finite element analysis (NLFEA) with 3-D solid elements is used to study the influence of column elongation on stress and strain in the slab around the column. Punching failure is shown to be triggered by localised peaks in shear stress around the corners of the support. Significantly, one-way shear is shown to increase the shear resistance of slabs supported on columns with cross sectional dimensions greater than around six times the slab effective depth (d). The common laboratory practice of supporting slabs in punching tests on elongated plates rather than columns is investigated numerically and is found to be reasonable despite uplift occurring in the central region of elongated plates. NLFEA with solid elements gives useful insights into punching failure but nonlinear shell elements are better suited to the practical assessment of slabs in building structures. The disadvantage of conventional nonlinear shell elements is that shear failure can only be detected through post processing of results. To circumvent this, the authors have previously developed a novel modelling approach in which 3-D joint elements are used to connect shell elements located to either side of a punching control perimeter positioned at 0.5 from the column face. The joint shear resistance is calculated using the Critical Shear Crack Theory (CSCT) in which punching resistance is related to slab rotation. Based on insights gained using the solid element modelling, this paper extends the use of the joint model to the modelling of punching failure at elongated supports by including one-way joints to model linear shear.
Abu-Salma D, Vollum R, Macorini L, 2020, Punching Shear at Slab-Edge Column Connections, 13th fib International PhD-Symposium in Civil Engineering
Setiawan A, Vollum RL, Macorini L, et al., 2020, Punching shear design of RC flat slabs supported on wall corners, Structural Concrete, Vol: 21, Pages: 859-874, ISSN: 1464-4177
Reinforced concrete buildings are typically braced with shear walls positioned around lift shafts and stairs. Vertical transfer of load from slab to walls leads to a concentration of shear stress in the slab at wall ends and corners, which needs to be considered in punching shear design. This issue is not addressed in EN 1992 (2004) and only partially addressed in fib Model Code 2010 leaving engineers to resort to their own judgment. Consequently, consideration of punching shear at wall corners can be overlooked entirely or not properly addressed through lack of knowledge. The paper addresses this issue by proposing a method for calculating the design shear stress at wall corners for use in conjunction with the Critical Shear Crack Theory. The method is initially validated against test results for slabs supported on elongated columns as well as numerical simulations. Subsequently, the method is extended to the punching design of a slab supported by a wall corner. The proposed analysis of the slab‐wall corner junction is validated against the predictions of nonlinear finite element analysis (NLFEA) employing 3‐D solid elements as well as the joint‐shell punching model (JSPM) previously developed by the authors.
Abu-Salma D, Vollum R, Macorini L, et al., 2020, Punching shear at slab-edge column connections, Pages: 622-630
This paper is concerned with punching shear design at edge column connections of flat slabs. Significantly, punching failure is much less researched at edge columns of flat slabs than at interior connections despite typical buildings having more edge than interior columns. In both cases, punching failure is undesirable since it can result in progressive collapse owing to load being redistributed from the failing connection to the surrounding connections. The paper considers the influence of eccentricity of loading and column aspect ratio on punching shear resistance at edge columns. Finite element analysis (FEA) shows that shear stress in the slab is concentrated towards the ends of elongated columns which are commonly found in residential buildings. This problem has not been widely researched either experimentally or numerically. Elastic shear field analysis is used to study the influence of column aspect ratio and loading eccentricity on the shear stress distribution around a punching control perimeter positioned at 0.5d from the column face where d is the slab effective depth. Comparisons are made with shear stress distributions obtained with nonlinear finite element analysis (NLFEA) using 3D-solid elements as well as linear and nonlinear shell elements. The NLFEA with solid elements is initially calibrated using experimental data. Subsequently, it is used to carry out parametric studies which consider the effect of varying: 1) the column cross-section dimensions and 2) loading eccentricity. The results of the NLFEA are used to assess two alternative methods for calculating punching shear resistance at edge columns using the Critical Shear Crack Theory (CSCT). The paper presents a refined method based on shear field analysis for calculating the punching shear resistance of flat slabs supported on elongated edge columns.
Setiawan A, Vollum R, Macorini L, et al., 2019, Efficient 3D modelling of punching shear failure at slab-column connections by means of nonlinear joint elements, Engineering Structures, Vol: 197, Pages: 1-19, ISSN: 0141-0296
Failures of isolated slab-column connections can be classified as either flexural or punching. Flexural failure is typically preceded by large deformation, owing to flexural reinforcement yield, unlike punching failure which occurs suddenly with little if any warning. This paper proposes a novel numerical strategy for modelling punching failure in which nonlinear joint elements are combined with nonlinear reinforced concrete (RC) shell elements. The joint elements are employed to model punching failure which limits force transfer from slabs to supporting columns. The shear resistance of individual joint elements is calculated using the critical shear crack theory (CSCT) which relates shear resistance to slab rotation. Unlike other similar models reported in the literature, the joint strength is continually updated throughout the analysis as the slab rotation changes. The approach is presented for slabs without shear reinforcement but could be easily extended to include shear reinforcement. The adequacy of the proposed methodology is verified using experimental test data from isolated internal RC slab-column connections tested to failure under various loading arrangements and slab edge boundary conditions. Comparisons are also made with the predictions of nonlinear finite element analysis using 3-D solid elements, where the proposed methodology is shown to compare favourably whilst requiring significantly less computation time. Additionally, the proposed methodology enables simple calculation of the relative contributions of flexure, torsion and eccentric shear to moment transfer between slab and column. This information is pertinent to the development of improved codified design methods for calculating the critical design shear stress at eccentrically loaded columns.
Vollum R, Goodchild C, 2019, Proposed EN 1992 tension lap strength equation for good bond, Structures, Vol: 19, Pages: 5-18, ISSN: 2352-0124
The paper is concerned with the design of tension laps in reinforced concrete structures. The most recent codified design recommendations for reinforcement laps and anchorages are found in fib Model Code 2010 (MC2010). These recommendations have heavily influenced the draft revision of EN 1992 which is due for publication in 2023. The draft EN 1992 proposal for tension laps is still under development with the main point of discussion being the basic multiplier required to achieve the level of safety prescribed by EN 1990. This is contentious since laps designed to MC2010 can be significantly longer than laps designed to EN 1992 (2004) which many UK designers consider excessive in comparison with previous UK practice. The paper examines the safety of tension laps and proposes a refined design equation for inclusion in the 2023 revision to EN 1992. The proposed design equation achieves the level of safety required by EN 1990 whilst giving lap and anchorage lengths more consistent with current practice than MC2010.
Filiagi Pastore M, Vollum R, 2019, SHEAR ENHANCEMENT IN RC BEAMS WITH CONCOMITANT LOADS NEAR AND FAR FROM SUPPORTS, INNOVATIONS IN MATERIALS, DESIGN AND STRUCTURES - 16th fib Symposium
Setiawan A, Vollum RL, Macorini L, 2019, Numerical and analytical investigation of internal slab-column connections subject to cyclic loading, Engineering Structures, Vol: 184, Pages: 535-554, ISSN: 0141-0296
Properly designed flat slab to column connections can perform satisfactorily under seismic loading. Satisfactory performance is dependent on slab column connections being able to withstand the imposed drift while continuing to resist the imposed gravity loads. Particularly at risk are pre 1970’s flat slab to column connections without integrity reinforcement passing through the column. Current design provisions for punching shear under seismic loading are largely empirical and based on laboratory tests of thin slabs not representative of practice. This paper uses nonlinear finite element analysis (NLFEA) with ATENA and the Critical Shear Crack Theory (CSCT) to investigate the behaviour of internal slab-column connections without shear reinforcement subject to seismic loading. NLFEA is used to investigate cyclic degradation which reduces connection stiffness, unbalanced moment capacity, and ductility. As observed experimentally, cyclic degradation in the NLFEA is shown to be associated with accumulation of plastic strain in the flexural reinforcement bars which hinders concrete crack closure. Although the NLFEA produces reasonable strength and ductility predictions, it is unable to replicate the pinching effect. It is also too complex and time consuming to serve as a practical design tool. Therefore, a simple analytical design method is proposed which is based on the CSCT. The strength and limiting drift predictions of the proposed method are shown to mainly depend on slab depth (size effect) and flexural reinforcement ratio which is not reflected in available empirically-based models which appear to overestimate the drift capacity of slab-column connections with dimensions representative of practice.
Setiawan A, Vollum R, Macorini L, 2019, Simulating non-axis-symmetrical punching failure of RC slabs using a lumped element approach, Pages: 613-620
Design methods for punching shear typically compare the nominal shear stress calculated on a basic control perimeter around the column with the design shear resistance. The shear stress around the control perimeter is typically non-uniform due to asymmetries in structural arrangement, loading and reinforcement layout. This non-uniformity needs to be accounted for in design. This work proposes a novel numerical technique for modelling punching shear failure at slab-column connections in which lumped 3-D joint elements are combined with RC layered-shell elements. Shell elements are used to simulate the flexural behaviour of the slab while joint elements, positioned around a control perimeter at half of the effective depth from the column face, are used to model out-of-plane shear failure. Failure of each individual joint is controlled by the Critical Shear Crack Theory (CSCT) failure criterion. The capability of the proposed approach to capture punching is verified using experimental data from isolated punching specimens that are non-axis symmetric due to loading, flexural reinforcement arrangement and/or elongated column. Comparisons are also made with the predictions of the CSCT and nonlinear finite element (FE) analysis with solid elements. Based on numerical results from nonlinear simulations using the proposed joint model, a simple modification is proposed to the original CSCT formulation for calculating punching resistance at elongated columns.
Elwakeel A, Vollum R, 2019, Shear strength enhancement of RC beams loaded in the tension face, Pages: 1733-1740
The shear strength of RC beams is significantly enhanced by arching action when loads are applied within twice the beam effective depth (2d) of supports. Many studies have investigated this phenomenon for single span simply supported beams with single point loads applied to their compression face within 2d of supports. However, very little research has been carried out into shear enhancement in beams with several point loads applied within 2d of the support. Previous research into this problem has focussed on situations where pairs of equal point loads are applied to the compressive face of the beam. This research compares the behaviour of beams loaded with pairs of concentrated loads applied, within 2d of the support, to either the tension or compression face. The research was motivated by differences in the geometry of strut and tie models for each case, which does not appear to have been previously investigated. The behaviour of the beams during tests was recorded with Digital Image Correlation (DIC) which captured the full displacement field of the beams. The displacement field was analysed to determine the crack kinematics. This enabled the contributions to shear resistance of aggregate interlock and dowel action to be determined. The paper summarises the results of the experimental program and describes insights into shear resisting mechanisms gained from studying the crack kinematics obtained from the DIC. The influence of the loading face being in tension or compression is also discussed.
Pastore MVF, Vollum RL, 2019, An analysis of the shear transfer actions in RC short span beams using crack kinematics recorded via DIC, Pages: 1755-1762
Shear in reinforced concrete (RC) beams is resisted by a combination of the flexural compression zone, residual tensile stress, aggregate interlock, dowel action and shear reinforcement if present. The proportion of shear force resisted by each shear action is directly related to the kinematics (opening and sliding) of the critical shear crack. In beams loaded within around twice the effective depth (d) of supports, shear resistance is increased by arching action whereby part of the load is transferred to the nearest support through direct strutting action. The paper describes a study which was undertaken to investigate shear transfer mechanisms in beams loaded near their supports. A total of four simply supported RC beams (three short-span and one slender beams) without shear reinforcement were tested to study the influence of loading arrangement on shear enhancement and the kinematics of the critical shear crack. Two of the beams were loaded with two/three concentrated loads applied within 2d and at 3d from the support where shear failure occurred. The crack kinematics were determined during loading using digital image correlation (DIC). For each beam, constitutive models from the literature were used to assess the contribution of each shear resisting mechanism at various loading stages up to failure. The paper presents selected test results and relates the contribution of each shear resisting mechanism to the loading arrangement, shape of the critical shear crack and its kinematics. Finally, general observations are made about shear resisting mechanisms in the tested beams.
Vella JP, Vollum RL, Kotecha R, 2018, Headed bar connections between precast concrete elements: design recommendations and practical applications, Structures, Vol: 15, Pages: 162-173, ISSN: 2352-0124
The paper provides an overview of research into the design and behaviour of joints between precast concrete elements in which continuity of reinforcement is achieved through overlapping headed bars, allowing very short lap lengths. A series of tensile and flexural tests were carried out on joints with lapped headed bars of 25 mm diameter with 70 mm square heads and measured yield strength of 530 MPa. The tests studied the influence on joint behaviour of joint concrete strength, transverse reinforcement, geometry, and out-of-plane tolerances. Observations from tests and numerical analysis were used to develop design procedures for headed bar joints based on strut-and-tie modelling and the upper bound theorem of plasticity respectively. A recently completed project using headed bar joints demonstrates the benefits of using this system in precast concrete construction. The potential for further savings in costs and labour when adopting design recommendations stemming from this research is also discussed.
Micallef M, Vollum RL, 2018, The behaviour of long tension reinforcement laps, Magazine of Concrete Research, Vol: 70, Pages: 739-755, ISSN: 0024-9831
Over time, the length of reinforcement laps required by design standards has increased significantly. By way of illustration, fib Model Code 2010 can require over twice the lap length required by the superseded UK code BS8110:1997. The need for this increase is debatable since, outside the laboratory, there is no evidence that laps designed to BS8110 are unsafe. The paper describes an experimental programme which was undertaken to compare failure modes of beams with laps of varying length loaded in four point bending. Tested laps are classified as “short”, “long” and “very long” with “long” laps just sufficient to develop reinforcement yield. The “very long” laps were between 1.5 and 2.0 times the length of the “long” laps. Tested laps were between bars of equal as well as mixed diameter with diameters ranging between 16 mm and 25 mm. Instrumentation included strain gauges and digital image correlation which was used to record crack development. Bond failure was very sudden and brittle in “short” laps. The failure modes of both “long” and “very long” laps were ductile due to flexural reinforcement yield. However, bond failure occurred subsequent to yield in “long” laps including at least one 25 mm diameter bar.
Setiawan A, Vollum R, Macorini L, 2018, Implementation of the critical shear crack theory to predict punching failure in the analysis of RC layered-shells, 12th fib International PhD Symposium in Civil Engineering
Setiawan A, Vollum R, Macorini L, 2018, NUMERICAL INVESTIGATION ON PUNCHING SHEAR OF SLAB-COLUMN CONNECTIONS SUBJECTED TO SEISMIC LOADING, 16th European Conference on Earthquake Engineering
Vella JP, Vollum RL, Jackson A, 2017, Flexural Behaviour of Headed Bar Connections between Precast Concrete Panels, Construction and Building Materials, Vol: 154, Pages: 236-250, ISSN: 0950-0618
The use of headed bars in joints between precast concrete elements allows continuity of reinforcement to be achieved over very short splice lengths. The paper describes a series of flexural tests carried out on specimens consisting of pairs of precast elements connected by overlapping headed bars of 25 mm diameter. The headed bars overlapped by 100 mm within a 200 mm wide in situ concrete joint in which transverse bars and vertical shear studs were installed to provide confinement. This type of joint facilitates the construction of continuously reinforced slabs from precast elements thereby enabling significant reductions in overall construction time and improvements in construction quality due to off-site fabrication. The tests investigated the influence on joint strength, ductility and crack width of concrete strength, out-of-plane offset of precast planks and confining shear studs. Ductile failure with yield of 25 mm diameter high strength headed bars was achieved with joint concrete having a cylinder compressive strength of 39 MPa. A nonlinear finite element model is presented, which gives good predictions of joint strength as well as providing insight into joint behaviour.
Micallef M, Vollum RL, Izzuddin BA, 2017, Cracking in walls with combined base and end restraint, Magazine of Concrete Research, Vol: 69, Pages: 1170-1188, ISSN: 0024-9831
Restraint of early-age thermal and long-term shrinkage strain can cause cracking in reinforced concrete members. Eurocode 2 provides guidance on the design of crack control reinforcement in reinforced concrete elements with base (edge) and end restraint, but not combined base and end restraint, which commonly occurs. The paper describes an experimental programme, which was conducted to investigate early-age and long-term shrinkage cracking in reinforced concrete walls with combined base and end restraint. The main variables in the test programme were concrete cover and reinforcement ratio. Early-age cracking is simulated with non-linear finite-element analysis, which is shown to capture the observed behaviour adequately. Eurocode 2 gives reasonable estimates of long-term crack widths in the tested walls if edge restraint is assumed, but significantly overestimates crack widths if the worst case of end restraint is assumed.
Micallef M, Vollum RL, 2017, The effect of shear and lap arrangement on reinforcement lap strength, Structures, Vol: 12, Pages: 253-264, ISSN: 2352-0124
The paper is concerned with the design of tension laps in reinforced concrete structures. The most recent design recommendations for laps are found in fib Model Code 2010 which is likely to influence the next revision of EN-1992. This is of concern to UK industry since laps designed to MC2010 can be significantly longer than laps designed to EN-1992 which UK designers already consider excessive compared with previous UK code requirements. Unlike the previous UK code, BS8110, EN-1992 requires adjacent laps to be offset by 0.3 of the lap length which complicates reinforcement detailing. The paper describes an experimental programme which was undertaken to assess the influence on lap performance of increasing lap length beyond that required for bar yield, shear and staggering of laps. The influence of shear was assessed by comparing the performance of laps of the same length positioned in zones of uniform and varying bending moment. Reinforcement strains were monitored and detailed measurements of crack development and crack widths were obtained with digital image correlation. Results show that very long laps are inefficient with the central half contributing little to force transfer between bars. Shear was found to have no significant influence on lap strength while lapping only 50% of bars at a section increased forces in the lapped bars leading to premature bond failure. Test results are compared with EN-1992 predictions, which are shown to be conservative for the tested laps.
The structural testing and finite element (FE) analysis described in this paper were part of a major research project undertaken at Imperial College London to investigate the deformation of bolted segmental grey cast iron (GCI) tunnel linings. A key aim was to quantify how joints influence the behaviour of the lining, through a three-path approach comprising physical experiments, finite element modelling, and field instrumentation. The laboratory results have been used to assess the validity of the tunnel assessment methods used by industry.This study examined joint articulation under the serviceability limit state in the absence of hoop force focussing on factors such as applied bolt preload, the loading direction and the freedom of the circumferential flange to deflect. Two half-scale GCI lining segments were bolted together at the longitudinal flanges to form a bolted arch in a similar fashion to the tests performed by Thomas (1977). Modern instrumentation was implemented to gain detailed measurements quantifying changes in global displacements of the two segments, bolt forces and joint opening under applied loading. For the first time, the physical experiments were conducted contemporaneously with the development of a three-dimensional FE model of the joint. The experimental data and the results from the FE analysis indicate a reduction in joint stiffness as the joint articulates under applied load. It is shown that the presence of a joint has far greater influence on the behaviour of the ‘arch’ than the level of preload applied to the bolts in the joint. The FE analysis allowed the deformation behaviour of the joint under positive and negative bending to be investigated: its response under the two modes differs significantly.
Vella JP, Vollum RL, Jackson A, 2017, Headed Bar Connections between Precast Concrete Panels Loaded in Bending, fib Symposium 2017
Einpaul J, Vollum RL, Ramos AP, 2017, On the distribution of shear forces in non-axisymmetric slab-column connections, fib Symposium 2017
Pamplona MKY, Ferreira MP, Vollum RL, 2017, Bearing Capacity of Partially Loaded Concrete Elements, fib Symposium 2017
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