Effectiveness of two forms of grouted reinforced confinement methods to hollow concrete masonry panels

This paper presents a study on the effectiveness of two forms of reinforced grout confining systems for hollow concrete block masonry. The systems considered are: (1) a layer of grout directly confining the unreinforced masonry, and; (2) a layer of grout indirectly confining the unreinforced masonry through block shells. The study involves experimental testing and finite-element (FE) modeling of six diagonally loaded masonry panels containing the two confining systems. The failure mode, the ultimate load, and the load-deformation behaviors of the diagonally loaded panels were successfully simulated using the finite-element model. In-plane shear strength and stiffness of the masonry thus determined are used to evaluate some selected models of the confined masonry shear including the strut-and-tie model reported in the literature. The evaluated strut width is compared with the prediction of the FE model and then extended for rational prediction of the strength of confined masonry shear walls

Development of a new design expression for the in-plane shear capacity of the partially grouted concrete masonry walls

Partially grouted masonry walls subjected to in-plane shear exhibit a complex behaviour because of the influence of the aspect ratio, the pre-compression, the grouting pattern, the ratios of the horizontal and the vertical reinforcements, the boundary conditions and the characteristics of the constituent materials. The existing in-plane shear expressions for the partially grouted masonry are formulated as sum of strength of three parameters, namely, the masonry, the reinforcement and the axial force. The parameter ‘masonry’ includes the wall aspect ratio and the masonry compressive strength; the aspect ratio of the unreinforced panel inscribed into the grouted cores and bond beams are not considered, although failure is often dominated by these unreinforced masonry panels. This paper describes the dominance of these panels, particularly those that are squat, to the shear capacity of whole of shear walls. Further, the current design formulae are shown highly un-conservative by many researchers; this paper provides a potential reason for this un-conservativeness. It is shown that by including an additional term of the unreinforced panel aspect ratio a rational design formula could be established. This new expression is validated with independent test results reported in the literature – both Australian and overseas; the predictions are shown to be conservative

Studies on the in-plane shear response of confined masonry shear walls

The prime aim of this research project is to evaluate the performance of confined masonry walls under in-plane shear with a view to contributing to the national masonry design standard through a set of design clauses. This aim stems from the criticisms of the current provisions of the in-plane shear capacity equations in the Australian Masonry Standard AS3700 (2011) being highly non-conservative. This PhD thesis is an attempt to address this gap in the knowledge through systematic investigation of the key parameters that affects the in-plane shear strength of the masonry walls through laboratory experiments and extensive finite element analyses

Studies on the existing in-plane shear equations of partially grouted reinforced masonry

This paper provides critical analyses of the presence of the reinforced grout cores within the masonry walls with particular reference to the existing in-plane shear design expressions in several national standards; these expressions comprise terms which define the shear strength of masonry, the vertical load and the area of reinforcement. \ud \ud These expressions treat the wall height to length ratio (termed as wall aspect ratio) as a prime factor in their respective masonry strength terms. The consideration of the wall aspect ratio in these design expressions implies existence of a compression strut along the wall diagonal, although such a phenomenon is not established in the literature. \ud \ud In this paper, through an extensive analyses of partially grouted reinforced masonry shear walls using a validated nonlinear finite element model, it is shown that the aspect ratio of the unreinforced masonry panels inscribed within the vertical and the horizontal reinforced grouted cores has profound effect on the in-plane shear capacity of the walls. \ud \ud It is also shown that the horizontal and the vertical reinforcements do never yield and hence their inclusion in the in-plane shear capacity expressions is not justified. A recently reported expression by the authors is also reviewed and compared with the other international design expressions

Finite element analysis of the in-plane shear behaviour of masonry panels confined with reinforced grouted cores

A combined experimental and numerical program was conducted to study the in-plane shear behaviour of hollow concrete masonry panels containing reinforced grout cores. This paper is focused on the numerical program. A two dimensional macromodelling strategy was used to simulate the behaviour of the confined masonry (CM) shear panels. Both the unreinforced masonry and the confining element were modelled using macromasonry properties and the steel reinforcement was modelled as an embedded truss element located within the grout using perfectly bonded constraint. The FE model reproduced key behaviours observed in the experiments, including the shear strength, the deformation and the crack patterns of the unconfined and confined masonry panels. The predictions of the validated model were used to evaluate the existing in-plane shear expressions available in the national masonry standards and research publications

Review on flexible pavement design guidelines

The primary objective of this research is to identify the proper design guideline in terms of strength of the structure that enable to last longer life span. Field testing was conducted to check performance of selected pavement design using AASHTO and TRL Road Note 31 guidelines. Finite Element Model was developed and validated with field data to analyze the performance of different pavement designs. Validated model was used to evaluate the structural performance of AASHTO and RN 31 Designs for different ESAL and Subgrade support conditions

Comparison of structural capacity of Hot Mix Asphalt(HMA) pavement designs (AASHTO & TRL RN-31)

The primary objective of this research is to identify the proper design guidelines in terms of structural capacity, which enables to last longer life span without-any major failure. Inducing very high stress on pavement is one of the major reasons for structural failure.' American' Association of State Highway and Testing Officials (AASHTO) and the Transport Research Laboratory Road Note 31.(TRL RN~31) ate the widely used pavement design guidelines by many road agencies. Hence, this study intends to compare and contrast AASHTO (1994) and TRL RN-31. AASHTO method involve with the complicated empirical equation 3 jn appendix which has to be solved by iteration method to obtain the required structural capacity for given .conditions, So, computer program was developed using JAVA to solve AASHTO equation. RN-31 and AASHTO methods have been directly compared for a range of subgrade California Bearing Ratio (CBR) and traffic levels. Model pavements were constructed to e~aluate the performance' of the, pavement for static load and field collected data were used' to verify 'the Finite Element Model (FEM).The verified models were used to evaluate the structural performance of pavements. The main advaritag~ of this review on flexible pavement design guidelines.is thatthe pavement which provide higher structural capacity can be simply.identifiedand constructed, so that, it-can reduce the overall cost and provide goodplatform to the users

Wider reinforced masonry shear walls subjected to cyclic lateral loading

Partially grouted wider reinforced masonry wall, built predominantly with the use of face shell bedded hollow concrete blocks, is adopted extensively in the cyclonic areas due to its economy. Its out-of-plane response to lateral pressure loading is well definied; however its in-plane shear behaviour is less well understood, in particular it is unclear how the grouted reinforced cores affect the load paths within the wall. For the rational design of the walls, clarification is sought as to whether the wall acts as a composite of unreinforced panels surrounded by the reinforced cores or simply as a continuum embedded with reinforcement at wider spacing. This paper reports four full scale walls tested under in-place cyclic shear loading to provide some insight into the effect of the grout cores in altering the load paths within the wall. The global lateral load - lateral deflection hysteretic curves as well as the local responses of some critical zones of the shear walls are presented. It is shown that the aspect ratio of the unreinforced masonry panels surrounded by the reinforced grouted cores within the shear walls have profound effect in ascertaining the behaviour of the shear walls

Design expressions for the in-plane shear capacity of confined masonry shear walls containing squat panels

In-plane shear capacity formulation of reinforced masonry is commonly conceived as the sum of the capacities of three parameters, viz, the masonry, the reinforcement, and the precompression. The term “masonry” incorporates the aspect ratio of the wall without any regard to the aspect ratio of the panels inscribed (and hence confined) by the vertical and the horizontal reinforced grout cores. This paper proposes design expressions in which the aspect ratio of such panels is explicitly included. For this purpose, the grouted confining cores are regarded as a grid of confining elements within which the panels are positioned. These confined masonry panels are then considered as building blocks for multi-bay, multi-storied confined masonry shear walls and analyzed using an experimentally validated macroscopic finite-element model. Results of the analyzes of 161 confined masonry walls containing panels of height to length ratio less than 1.0 have been regressed to formulate design expressions. These expressions have been first validated using independent test data sets and then compared with the existing equations in some selected international design standards. The concept of including the unreinforced masonry panel aspect ratio as an additional term in the design expression for partially grouted/confined masonry shear walls is recommended based on the conclusions from this paper

Response of partially grouted wider reinforced masonry walls to inplane cyclic shear

Partially grouted wider reinforced masonry wall, built predominantly using face shell bedded hollow concrete blocks, is an economical structural system and is popularly used in the cyclonic areas; its out-of-plane response to lateral loading is well understood, unfortunately its inplane shear behaviour is less well understood as to the effect of partial gouting in intervening the load paths within the wall. For rational analysis of the wall clarification is sought as to whether the wall acts as a composite of unreinforced panels and reinforced cores or as a continuum of masonry embedded with reinforced at wider spacing. This paper reports the results of four full scale walls tested under inplane cyclic shear loading to provide some insight into the effect of the grout cores in altering the load paths within the wall. The global lateral load - lateral deflection hysteric curves as well as local responses of some critical zones of the shear walls are presented