Two-way Spanning Research Articles

Engineering methodology to assess the seismic out-of-plane response of two-way spanning unreinforced masonry walls with multiple openings

Engineering methodology to assess the seismic out-of-plane response of two-way spanning unreinforced masonry walls with multiple openings

Anti-Impact Performance Enhancement of Two-Way Spanning Slab through the Implementation of Steel Trussed Bars

Reinforced concrete (RC) slabs represent integral structural components extensively employed in architectural and infrastructural frameworks owing to their inherent robustness and longevity. In contemporary times, there has been a pronounced surge in endeavors aimed at comprehensively elucidating the anti-impact properties inherent in RC slabs. This surge is propelled by a compelling necessity to fortify these structures against the deleterious effects of low-velocity impacts, thereby ensuring their steadfastness and resilience. Consider the thorough investigation into the anti-impact characteristics of RC slabs, which has been rigorously pursued through both experimental and computational methodologies. A plethora of scholarly discourse on this topic is readily available, providing invaluable insights into the structural dynamics governing slabs subjected to low-velocity impacts. However, there is a noticeable gap in research concerning the strengthening of slabs through shear reinforcement, particularly through economical, easily fabricated, and efficient systems such as fabricated trussed bars. The primary objective of this study is to explore the structural behavior of RC slabs fortified with custom-designed trussed bars under the influence of low-velocity impacts. To accomplish this, the Abaqus software platform is explicitly employed for analysis. The slab without any shear reinforcement is experimentally tested and serves as a reference model for numerical verification. Its anti-impact performance is compared with numerical findings. Following validation, simulations are conducted for square slabs strengthened by fabricated trussed bars in orthogonal and diagonal layouts. The results demonstrate that employing fabricated truss bars shear reinforcement with a 3 mm diameter in orthogonal and diagonal layouts enhances the resistance of slabs to damage, resulting in a 28.41% and 47.06% decrease in damage, respectively. The utilization of engineered truss bars as shear reinforcement yields significant improvements in strength, rigidity, and ductility when compared to control samples lacking such reinforcement. This enhancement is particularly evident when the engineered truss bars are arranged in orthogonal and diagonal configurations.

Flexural Behaviour of the Two-Way Spanning Reinforced Concrete Slab Using Spherical Plastic Bubble Balls

The use of conventional reinforced concrete in the construction industry increases each year, especially in developing countries. However, the concrete content, particularly cement production contributed to the greenhouse gas emission subsequently increase to climate change. Thus, the reinforced concrete slab containing high-density polyethene (HDPE) hollow spherical plastic bubble balls also known as bubble deck slabs were introduced for sustainable construction. This type of slab forms a slab that has less concrete volume compared to the normal solid reinforced concrete slab. Although this unique system can facilitate up to a 50% longer span compared to the conventional reinforced concrete solid slab, yet, it can cause the performance of the slab structure such as flexural and shear capacity may be affected due to the thirty to forty per cent of fewer concrete volumes. Hence, this paper studies the comparison of the performance of the two-way supported slabs; reinforced bubble deck slab and normal solid reinforced concrete slab after being subjected to the area loading. The square slabs are 1200mm by 1200mm in width and length with a thickness of 235mm. The investigations of the experiments included flexural strength, bending stiffness and load-deflection behaviour due to the impact of the area loading. Also, the crack propagation and crack pattern which differs also was shown for each type of slab system, especially in shear strength.

Simplified methodologies for assessing the out-of-plane two-way bending seismic response of unreinforced brick masonry walls: lessons from recent experimental studies

This paper describes a simplified methodology for the assessment of unreinforced masonry (URM) walls under out-of-plane two-way bending seismic action. The methodology involves a force-based check derived from the principle of virtual work. This check is proposed based on experimental observations of significant cracking resistance associated with two-way spanning URM walls, indicating methodologies considering such walls to be pre-cracked or to be non-laterally supported as overly conservative. The methodology incorporates several findings and developments from recent experimental campaigns: ranging from novel characterization tests on masonry couplets to incremental dynamic tests on full-scale buildings. Such incorporations include new formulation to calculate the torsional shear strength of a bed joint and accounting for possible changes in the boundary conditions of an OOP wall during dynamic loading. Testing standards as well as recommendations in several international guidelines for masonry structures addressing the input properties required to implement the proposed methodology are enlisted and reviewed. The methodology requires the definition of the period of vibration of the assessed URM walls, to calculate which plate theory based formulation is provided. Open research questions and potential avenues for further development of the methodology are ultimately highlighted.

Experimental validation of optimum resistance moment of concrete slabs reinforced with carbon fibre-reinforced plastic

Fibre-Reinforced Plastics (FRPs) have been suggested as suitable reinforcement for concrete structures among other solutions to combat corrosion problems in steel reinforced concrete. This paper presents the experimental validation of optimum resistance moment of concrete slabs reinforced with Carbon-Fibre Reinforced Plastic (CFRP). Eight specimens of two-way spanning slabs reinforced with CFRP bars were used in the experiment. They were designed to achieve two classical failure modes: rupture of the reinforcements (tension failure) and crushing of the concrete while the reinforcement remains elastic (compression failure). This was accomplished by using reinforcement ratios less, and more than the balanced reinforcement ratio, , for the slabs, respectively. All the slabs failed as predicted. The results obtained show that the design formulations for predicting the minimum flexural resistance of an CFRP-reinforced concrete member provided by CSAS806-02(R07) have been underestimated. The design formulations were found to underestimate the resistance moment capacity of CFRP-reinforced concrete slabs by about 33%. Keywords : optimum resistance moment, concrete slabs, CFRP, design formulation.

Out-of-plane load–displacement model for two-way spanning masonry walls

This paper describes a methodology for modelling the nonlinear, inelastic load–displacement behaviour of two-way spanning unreinforced masonry walls subjected to out-of-plane loading. The model utilises a simplified macroblock approach that starts with the assumption of a collapse mechanism based on the wall’s boundary conditions. It then treats the wall as having zero tensile strength and assumes that the resistance comes entirety from two gravity-based resistance components: elastic rigid block rocking, and inelastic friction, with the total load resistance of the wall taken as the sum of these individual components. Analytical expressions for calculating the load and displacement capacities of the elastic rocking component of response are derived from the principles of statics using an integration approach well suited for the treatment of two-way mechanisms. Expressions for the associated frictional capacity component are obtained using the virtual work method. Comparison of the theoretical load–displacement response with experimentally measured data is favourable as demonstrated using data obtained via quasistatic cyclic tests on two-way spanning walls; the model is shown to provide an acceptable lower bound estimate of actual behaviour. The developed approach could be used to construct pushover curves for a range of different collapse mechanisms and therefore has the potential to be assimilated into a simplified displacement-based seismic design/assessment technique for two-way spanning walls against out-of-plane collapse.

Investigation of the free vibration behaviour of an innovative GFRP sandwich floor panel

A new GFRP sandwich floor panel has been developed in the last few years to replace the traditional timber panel. This panel has acceptable structural mechanical properties to be used in civil engineering applications. The present work focuses on the free vibration behaviour of the one-way, two-way, and continuous GFRP sandwich floor panels. Few different variables were considered in this study; span of the panel, single spanning, continuous spanning, panel restrain types at supports, and skin fibre orientations. The restraints types considered are free, screws, and glue. A 3D numerical finite element model was developed to find the mode shape of different panels. It was found that the natural frequency of this panel is non-linear with respect to span variations. The orientation 0°/90° gives higher frequency than ±45° in the case of one-way spanning panel, and the orientation ±45° gives higher frequency than 0°/90° in the case of two-way spanning panel.

Performance of joints in reinforced concrete slabs for two-way spanning action

A series of tests on filigree slab joints was performed with the aim of assessing whether such joints can be reliably used in the construction of two-way spanning reinforced concrete slabs. The test results were compared with code requirements. Adequate joint performance is shown to be achievable when the joints are appropriately detailed. Further research is recommended for the formulation of a more generic understanding when the design parameters are varied from those studied in this work.

Failure Assessment of Lightly Reinforced Floor Slabs. I: Experimental Investigation

This paper is concerned with the ultimate behavior of lightly reinforced concrete floor slabs under extreme loading conditions. Particular emphasis is given to examining the failure conditions of idealized composite slabs which become lightly reinforced in a fire situation as a result of the early loss of the steel deck. An experimental study is described which focuses on the response of two-way spanning floor slabs with various materials and geometric configurations. The tests enable direct assessment of the influence of a number of key parameters such as the reinforcement type, properties, and ratio on the ultimate response. The results also permit the development of simplified expressions that capture the influence of salient factors such as bond characteristics and reinforcement properties for predicting the ductility of lightly reinforced floor slabs. The companion paper complements the experimental observations with detailed numerical assessments of the ultimate response and proposes analytical mode...

Small-scale concrete slab tests at ambient and elevated temperatures

This paper presents test results of forty-eight horizontally unrestrained two-way spanning reinforced concrete slabs at ambient and elevated temperatures. The tests allowed a direct comparison between the modes of failure observed at ambient and elevated temperatures. Both mild steel and stainless-steel welded smooth wire meshes, with varying bar diameters and spacing, were used as reinforcement. The tests at ambient temperature showed that slabs with low reinforcement ratio failed by fracture of reinforcement at the centre of the slab either across the shorter span for the rectangular slabs or across one of the spans for the square slabs. It was found that increasing the reinforcement ratio led to the compressive failure of concrete at the corners of the slabs. Repeating the tests at elevated temperatures showed that all the slabs failed by fracture of reinforcement, with displacements ranging from span/12 to span/6. The results showed clearly that membrane action occurred at both ambient and elevated temperatures, and provides a wealth of data which can be used to further develop simple design methods or validate existing finite-element models.

Dynamic response of walls and slabs by single-degree-of-freedom analysis—a critical review and revision

Single-degree-of-freedom (SDOF) methods for dynamic analysis of reinforced concrete flexural members subjected to blast or ground-shock loading are reviewed. It is concluded that the Equivalent single-degree-of-freedom method is an appropriate approximate method of analysis, but that the widely published parameters in common usage for two-way spanning members such as slabs and walls are inaccurate by up to almost 50% for some coefficients, due to inappropriate assumptions and approximations being used in their original derivation. Revised values of SDOF parameters are presented for two-way spanning members, based on modern finite element and yield-line calculations.

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.

Tensegrity spline beam and grid shell structures

This paper considers a class of tensegrity structures with continuous tubular compression booms forming curved splines, which may be deployed from straight by prestressing a cable bracing system. A free-form arch structure for the support of prestressed membranes is reviewed and the concepts are extended to a two-way spanning system for double layer grid shell structures. A numerical analysis based on the Dynamic Relaxation (DR) method is developed which caters specifically for the form-finding and load analysis of this type of structure; a particular feature of the analysis is that bending components are treated in a finite difference form with three degrees of freedom per node rather than six. This simplifies the treatment of sliding collar nodes which may be used along the continuous compression booms of deployable systems.

Plastic design of two-way structures and elements

This is an introductory paper outlining the background to the plastic design of two-way spanning systems such as (some) space frames, bridge decks and steelwork connection components. The approach draws on the now well-established British (Baker) methods for the plastic design of one-way systems and upon the Scandinavian (Johansen, Hillerborg) proposals for two-way systems. What emerges is a new concept for a stress-resultant to be called a ‘Bimoment’. Bimoments seem to have a significance for some two-way systems comparable to the significance that ordinary bending moments have for one-way systems. Thus they do permit comprehensive direct equilibrium relationship between total loads and stresses for portions of plates or grillages which are large in one or both directions.

Effect of the arrangement of reinforcement on the behaviour of reinforced concrete slabs

Summary Tests on 10 two-way spanning, simply supported, reinforced concrete slabs are reported. The slabs were designed to have similar ultimate loads, but different arrangements of the reinforcement were adopted. The span/depth ratio was also varied. All slabs sustained loads higher than the theoretical collapse load given by the yield-line theory. The increased carrying capacity, due partly to tensile membrane action, ranged from 26 to 80 % depending on the arrangement of the reinforcement.