Effect Of Membrane Action Research Articles

Laboratory investigations of coupled polyethylene–sand–soft soil shallow foundations

This study investigates clayey soil from a road project situated in the district of Lodhran, Punjab, Pakistan. The subgrade prepared with the soil distorted due to heaving after a certain period of its construction. First, laboratory tests were conducted to explore the reason for this problem, examining the fundamental engineering properties of soil. The test results show that the soil acts as a soft material when water content reaches 30%, significantly reducing its strength. The soft soil is generally considered unsuitable for civil work due to its poor performance behaviour. So, the performance of clayey soil was examined in the study at its soft state by coupling it with stronger materials, such as polyethylene polymeric reinforcement and sand, developing laboratory-scale foundation models. Based on the model studies, the study proposes a sustainable polyethylene–sand–soft soil model, which shows 155 and 56% higher ultimate bearing capacity (BC) than soft soil and sand-reinforced soft soil foundations. The changes in BC occur due to the reinforcement action of the polyethylene reinforcement, which is associated with its tensile membrane action effects and interlock bonding at the soil-reinforcement interface. Practically, the study can reduce the dependency of industry practitioners on sand materials. Using polyethylene in civil work is viable for environmental sustainability.

Performance of Concrete Building Structure Exposed to Localized Fire

Concrete structures have a favorable position in the building industry with regard to their performance of fire resistance. The understanding of their behavior is essential for reliable analysis and design. This paper is mainly concerned with concrete building performance subjected to localized fire arrangement. Special attention has been given to the finite element model of a seven-story concrete building representing a typical commercial office building designed to European Standard. Very large displacements happened on horizontal direction of the floor slabs due to thermal expansions. The large displacement induced lateral movement of the floor slabs and created additional moments to external columns. Design engineers should ensure that the external columns have ability to accommodate lateral displacements during fire. Although, the thin external columns of the model can withstand these movements due to beneficial effect of membrane action developed to the floor slabs. Present analysis indicates that the performance of the whole structure is substantially different from the single isolated structural member behavior during fire. Although the current design procedures are conservative, design engineers have to consider the detrimental and beneficial effects of lateral slabs' thermal expansion in complete structure.

Experimental studies on load-carrying capacity of HFR-LWC beams accompanying membrane action

Membrane action has not been quantitatively described in current analyses but is regarded as a “hidden” safety factor in the existing design manuals. The ultimate resistances and failure patterns of beam-like members will be greatly altered by the membrane effects introduced by special constraints. This paper describes the results of an experimental campaign on 10 hybrid fiber reinforced-lightweight aggregate concrete (HFR-LWC) beams, aiming at investigating the effect of membrane action on their bearing capacities. Membrane forces (N and M) are introduced at the element supports through specifically designed clamps formed by two steel plates tensioned with a variable number of tie rods. The influences of the constraint stiffness, reinforcement ratio and fiber content are investigated and discussed. The membrane action effects on the load-carrying capacity are sensitive to both the structural deflections and the constraint stiffness. The ultimate load of the beam would be substantially underestimated if membrane action is neglected. Greater membrane actions are beneficial for the development of the bridging effect of the hybrid fibers and the interlocking effect of the coarse aggregates, thus giving rise to more ductile failure and a higher bearing capacity of HFR-LWC beams.

Comparative experimental study of fire resistance of two-way restrained and unrestrained precast concrete composite slabs

This paper presents the results of tests to investigate fire performance of two-way restrained precast concrete (PC) composite slabs under the standard ISO 834 condition. The fire tests include three specimens with different load levels and boundary conditions – with or without restraints around the edges. Tensile membrane action was observed to a moderate extent in all specimens tested, including the reference test at ambient temperature. No debonding was observed at the interface between the bottom precast slab and the top cast-in-situ composite layer for the restrained PC composite slabs, but cracks formed at the interface in the un-restrained PC composite slab. These results demonstrate much increased fire resistance due to restraint effects (195 min vs. 130 min) if the same load (195 kN) is applied, but similar fire resistance if based on load ratio (131 min and 130 min at the same load ratio of 0.42). A number of existing theoretical methods developed for calculating tensile membrane action effects of two-way concrete slabs, as well as the conventional yield line theory, are employed to calculate the load carrying capacities. They indicate that for the type of slabs investigated in this paper, the improvement due to tensile membrane action is moderate.

Large-scale experiment on the behaviour of concrete flat slabs subjected to standard fire

The use of concrete flat slabs in multi-storey buildings is increasing, and the current fire design guidelines for flat slabs are based on research carried out a few decades ago. Since then, material properties of concrete and construction techniques have changed, which require new experiments to be carried out to assess the fire performance of concrete flat slabs. In this work, the fire resistance of flat slabs was investigated at a large scale (3.78 m × 4.75 m) under structural loading and exposed to ISO 834 fire conditions. The boundary conditions were partially fixed, compared to previous tests where they were free to expand. These modified boundary conditions simulate closer to the actual conditions and capture the effects of membrane action on punching shear behaviour. No spalling occurred during the 3-h duration of the test. The test was also extended to investigate the behaviour during the cooling phase, as it is critical with restrained support conditions. Results show that the duration of fire resistance is significantly higher than that of similar tests with no lateral restraint. Heat propagation and deformation recovery during the cooling phase were also measured. Improved fire resistance duration suggests that the punching shear resistance is enhanced by restrained support conditions.

Distributed strain monitoring of two-way slabs

Two-way slab design and assessment is often based on conservative approaches due to a lack of data regarding slab behaviour. Distributed fibre optic strain sensors have the potential to provide extensive data sets for both lab experiments and field assessments. A proof of concept study was undertaken that involved four two-way slabs, with varying reinforcement ratios and levels of axial restraint, that were instrumented with distributed fibre optic strain sensors and tested under a central point load. The slabs with less reinforcement demonstrated a ductile flexural failure while the more heavily reinforced slabs failed due to punching shear. The axial restraint system developed for this research provided partial restraint and enhanced the capacity of both restrained specimens compared to the control specimens. The strain data enabled differences in support conditions (both vertical and axial) to be identified. Additionally, the data enabled the onset of reinforcement yielding to be captured and thus proved it to be a promising approach for measuring the beneficial of effects of membrane action. The results of the experiments were compared to a yield-line analysis and were found to be within 5% for the unrestrained specimens and within 10% for the axially restrained specimens despite the fact that two specimens failed in punching shear.

Experimental investigation into the effects of membrane action for continuous reinforced glass beam systems

In contemporary architecture, glass is more and more applied not only to make up the cladding of the building, but also for structural members such as beams and facade fins. The trend to increase the scale of these structural entities makes it increasingly structurally efficient to apply statically indeterminate beam systems. For these systems to be approved, contemporary building codes require them to provide structural safety on an element and system level. Therefore, a lot of hybrid glass beam concepts, in which glass is combined with another material that provides post-fracture capacity, were developed and investigated. Among others, reinforced glass beams have experimentally proven their feasibility for statically determinate (element safety) and indeterminate (system safety) support conditions by providing significant post-fracture capacity, ductility, plastic hinge formation and load redistribution capacity. However, system safety can also benefit from the effects of membrane action, which can result in yet higher post-fracture performance. Moreover, the latter can make a significant contribution to the robustness of a beam system when an accidental event occurs such as collapse of one of the supports. This paper presents experimental test results of statically indeterminate five-point bending tests with clamping end-supports on twelve 4.3 m long stainless steel reinforced beam specimens in which the horizontal membrane forces are assessed. Two series of tests were performed, with and without intermediate support, for two types of beams with varying reinforcement percentage (i.e. solid and hollow profile reinforcement). During the tests, significant compressive as well as tensile membrane action was observed. The effects of the latter on the load-carrying behaviour is discussed by comparing the load-deflection diagrams with those of similar reinforced glass beam systems without clamped external supports. From this comparison, it is concluded that membrane action provides significant contribution to the load-carrying behaviour of such beam systems. Significantly higher post-fracture capacities can be achieved for both reinforcement sections and both types of tests. It is concluded that membrane action can be incorporated in design, which will lead to more economical, slender and more transparent reinforced glass beam systems.

A multilevel calculation scheme for risk-based robustness quantification of reinforced concrete frames

Structural robustness has become an important research topic in the engineering community since several large failures in the past decades led to the public awareness and indicated the importance to consider structural robustness during the structural design. So far most research has been focusing on structural measures to improve structural robustness and on theoretical methods to quantify structural robustness. However with respect to the analysis of concrete frames, there are only a limited number of examples which try to quantify the achieved robustness level for the available structural measures, such as the development of alternate load paths by membrane action. In this paper both advanced calculation methods and quantification approaches for robustness are combined by a computational efficient calculation scheme which considers different levels of structural idealisation. The developed approach is able to quantify the reliability and structural robustness of planar reinforced concrete frames in an objective way while using a conditional risk-based robustness index and taking into account the developed membrane action. As an illustration the developed calculation scheme is applied and discussed for two alternative designs of a regular office building. The results show the importance of the uncertainty on membrane action effects on the structure in case of an unforeseeable event leading to a notional column removal.

Compressive Membrane Action Effects on Punching Strength of Flat RC Slabs

The design of reinforced concrete flat slabs in practice can be governed at failure by punching shear close to concentrated loads or columns. Punching shear resistance formulations provided by codes are calibrated on the basis of experimental tests on isolated slabs supported on columns in axisymmetric conditions. Nevertheless, the behavior of flat slabs can be different than isolated specimens due to the potentially beneficial contributions of moment redistributions and compressive membrane actions. Accounting for the significance of these effects, nonlinear finite element analyses are performed with the crack model PARC_CL implemented in Abaqus. This paper aims to investigate a series of punching shear tests on slabs with and without shear reinforcement, different reinforcement ratios and loading conditions accounting for the potential contribution to the enhancement of the punching strength due to compressive membrane action (CMA). The numerical results with a multi – layered shell modeling are then post – processed adopting the failure criterion of the Critical Shear Crack Theory (CSCT). The results pointed out the significant outcomes and differences between standard specimens and actual members showing how the current codes of practice may underestimate the punching capacity.

Fire Test of Timber-fibre Concrete Composite Floor

The subject of this paper is a description of experimental programme of timber-fibre concrete floor in fire. Furnace test was performed on one full-size floor specimen at the Fire testing laboratory PAVUS. Floor specimen was 4, 5 m long and 3 m wide, consisting of 60 mm fibre concrete topping on plywood formwork, connected to GL beams. It was subjected the standard fire for over 150 min. The membrane effect of the floor was progressively activated and the fire performance of timber-fibre concrete floor was better comparing to traditional design method. The project is a part of the experimental research that deals with the effect of membrane action of composite timber fibre reinforced floor slabs exposed to fire which is based on previous research on steel fibre reinforced concrete slabs. The main objective of the project is the preparation of the analytical model which can predict the fire resistance of such floors with dispersed reinforcement.

Evaluation of compressive membrane action effects on punching shear resistance of reinforced concrete slabs

It is widely recognized that Compressive Membrane Action (CMA), also called Arching Action, increases both the bending and punching capacities of reinforced concrete (RC) structures. In this paper a non-linear finite element (NLFE) approach which adopts multi-layered shell modeling of RC slabs is presented. NLFE analyses (NLFEA) were carried out with ABAQUS Code and UMAT.for user subroutine in which the crack model denoted as Physical Approach for Reinforced Concrete for Cyclic Loading (PARC_CL) was implemented. Post-processing of NLFEA results is presented which exploits the Critical Shear Crack Theory (CSCT) to evaluate the punching shear resistance of shell elements. The capability of the proposed numerical procedure, to properly determine the punching shear resistance of RC slabs, is checked by comparing numerical predictions with experimental punching shear capacities obtained on circular slabs tested at the Stevin Laboratory of TU Delft. Subsequently the same numerical procedure was adopted to evaluate CMA effects on the punching shear resistance of the Corick bridge deck in Northern Ireland, UK, subjected to concentrated loads. Finally the design punching shear resistances achieved with the presented procedure are compared with the analytical values obtained using the British Code BD81/02.

Non-linear analysis of membrane action effect in profiled steel sheeting dry board flooring system

This study highlights the effect of membrane action in improving load carrying capacity of Profiled Steel Sheeting Dry Board (PSSDB) floor system. PSSDB system is a lightweight composite structural system composed of profiled steel sheeting and dry board, attached together by self-drilling and self-tapping screws. Many literatures have reported that restricting conventional slabs, such as reinforced concrete slab, at the supports against translation and/or rotation while it is subjected to vertical loading develops the compressive membrane action in the slab. The development of this phenomenon is considered in the PSSDB system with concrete infill for continuous and practical spans, with and without topping concrete. Previous authors’ experimentally verified non-linear finite element model for the PSSDB floor without topping was extended to parametrically predict the effect of different boundary conditions on the performance of the system for practical applications. It was revealed that preventing the in-plane movement of the slab ends improves the flexural rigidities of the slab up to more than three times when considering central deflection of serviceability limit state. This was observed when the deflection limit load of the fixed both end supports model was compared to the pin-roller support model. Moreover, the topping concrete enhances the applicability of the system in longer span and the developed compressive membrane action dramatically boosts the load carrying capacity of the slab with restricted translation and/or rotation of the slab ends.

Modelling approaches for robustness assessment of multi-storey steel-composite buildings

This paper investigates the robustness of multi-storey steel composite buildings under sudden column loss scenarios using a multi-level framework developed at Imperial College London. The framework was previously applied at its lowest level using a grillage idealisation to obtain the floor system response by assuming a linear collapse mechanism, where further simplifying assumptions were made regarding the vertical connection between the different floors. In this paper, the nonlinear dynamic response of the floor system is established from detailed nonlinear static push-down analysis at different levels of structural idealisation, accounting also for the influence of inter storey continuity. At the highest level of idealisation, a detailed composite ribbed slab model is considered to represent more accurately membrane action and load distribution at large deflections. It is shown that the triangular dominant deformation mode, previously used at the individual beam level in grillage models, can affect the robustness prediction for the floor system. However, as the allowable vertical deflection increases with the availability of sufficient ductility supply, this assumption becomes realistic compared to the actual floor system deformed configuration. Furthermore, the effect of membrane action is found to increase structural resistance to column loss by 10% in comparison with the grillage model using EC4 effective width and tributary load distribution concepts. Overall, it is found that grillage models may still provide a good balance between accuracy and computational efficiency for practical robustness assessment, subject to incorporating essential modelling features as presented in this paper.

An experimental investigation on beam supported reinforced concrete skew slabs

An experimental programme has been designed to cast and test 18 beam supported reinforced concrete skew slabs subjected to distributed loading. The variables include edge rigidity, skew angle and coefficient of orthotropy. The load deflection behaviour, ultimate strength and the effect of cracking were studied and the results are presented. The current work highlights the effect of membrane action on skew slabs with lateral restraints and its significance.

Modeling of membrane action in floor slabs subjected to fire

Through observations from experiments and fire-caused damage in real buildings, it is found that membrane action plays an important role in enhancing the fire-resistant capacity of floor slabs. Considering the mechanism of membrane action in slabs subjected to fire, an explicit theoretical model is proposed. Based on the force and moment equilibrium requirement on slabs in fire, formulas for calculating the ultimate load- bearing capacity of floor slabs in fire conditions considering the effects of membrane action are obtained. The effectiveness of the theory for modeling membrane action of floor slabs subjected to fire is validated through satisfactory comparison with results from experiments and different theoretical simulations.

Membrane action in ground-bearing concrete slabs

Loading a ground-bearing slab at a location distant from the slab edge will inevitably incur membrane action. This membrane action can result in considerable enhancement of maximum load-carrying capacities. Although the enhancement may not be as great as for suspended slabs laterally restrained by their supports, it is nevertheless still substantial. Now that slabs are often continuously cast over large areas there may be considerable benefit from taking advantage of this load-carrying enhancement. The present paper presents a theoretical study of the effects of membrane action in these circumstances. It suggests that the inability of previous theoretical models to reproduce the failure loads from tests on slabs or to account for the considerable scatter in results may be the result of ignoring membrane action. An upper-bound plastic analysis is used to shed new light on the evolution of mechanisms and shows that, depending on stiffness, slabs on grade reach collapse loads with one of two modes. Either collapse takes place in flexure at a peak of the non-linear load–deflection behaviour or by punching through provoked by a through-depth crack at the perimeter of the loaded area. With pure flexure plastic methods, past analyses have failed to provide a non-trivial estimate of the size of the failing mechanism. Inclusion of membrane action is shown to predict the radius of the probable preferred collapse mechanism. A parametric study is provided, but further research work providing experimental scrutiny and convenient design routines is needed before this is of immediate benefit to the practitioner.

Numerical and analytical predictions of the limit load of rectangular two way slabs

Equations for predicting the strength of rectangular two-way spanning, reinforced concrete (RC) slabs of different edge conditions and under uniformly distributed loading are developed in this paper from the conventional yield line theory and the finite element method. The common material and geometrical parameters, normally associated with RC slabs, have been adopted as independent variables in the equation development. The yield line equations are further calibrated with experimental data to incorporate the effect of membrane action, thus, increasing their predictive capability. The efficiency of the equations are assessed by their use for predicting known experimental results.

Membrane effect in the reinforced concrete frames—a proposal for change in the design of frames structures

This paper is concerned with the effect of membrane action or arching action on the behaviour of reinforced concrete frames. An experimental programme designed to investigate the behaviour of frames at ultimate conditions was carried out. The results indicated that failure of the frame was either by ductile failure of the beam or brittle failure of the column, depending on the degree of end restraint provided to the beams by the columns. The most significant effect of the membrane forces on the behaviour of the frame was to greatly increase the bending moment imposed on the column. Due to the development of the membrane forces, the distribution and magnitude of the moment in the column and mode of failure of the frame was very different to that predicted using normal analysis methods. Rigid–plastic analysis was used to predict conditions close to failure. This approach, together with a method for estimating the ultimate stiffness of the columns, enables the failure condition to be predicted. On the basis of a combination of experimental and theoretical models, a method for allowing for membrane effects in the design of frames is presented.

Method for Seismic Base Isolation of Liquid-Storage Tanks

A new method for seismic base isolation of ground-supported vertical cylindrical liquid-storage tanks is proposed in which the base plate is supported on a soil bed, and the tank wall is supported on a ring of vertically soft rubber bearings. The isolated system derives its flexibility from rocking and uplifting of the base, and its energy-dissipation capacity derives its flexibility from base-plate yielding, soil damping, and hysteretic rubber damping. In this analysis, the tank-liquid system is represented by a lumped-mass-stick model, and the rubber bearings are represented by a series of nonlinear hysteretic axial springs. The partially uplifted base plate loaded by liquid is analyzed giving due consideration to the effects of membrane action and plastic yielding. Results demonstrate the ability of the isolation method in reducing significantly the overturning base moments and the axial compressive stresses in the tank wall, while still maintaining the values of base uplifts and plastic rotations in the base plate at reasonable levels.

A graphical solution for predicting the increase in strength of concrete slabs due to membrane action

Synopsis A simple graphical procedure for determining the effect of membrane action upon the load capacity of a rigid-perfectly-plastic reinforced concrete slab is presented. The load-enhancement-deflection curve is derived by asimple reflection of the yield criterion curve for the concrete section under axial force and moment. The method provides an immediate understandingof the effect of section design upon the load enhancement to be expected from membrane action.