Seismic performance evaluation of full-scale confined masonry building using light weight cellular panels

Highlights

• Confined masonry building constructed using light weight cellular panels.

• Light weight cellular panels have advantages of ease of installation, light weight, reduction of masonry cross-section, low carbon foot print and facilitating rapid construction.

• Confined masonry building constructed using light weight cellular panels exhibited superior performance in terms of seismic characteristics.

• Proposed construction system can be adopted in moderate to high seismic regions.

• CM buildings upto 2 stories favourable for all seismic zones, while 3 storey upto zone IV.

Abstract

This paper deals with the seismic performance of a confined masonry (CM) building using innovative light weight cellular (LWC) panels, under displacement controlled quasi-static reversed cyclic lateral loading. The LWC panels measured 590 × 270 × 140 mm, with four 60 mm diameter vertical holes and a 35 mm high trough shaped groove for interlocking along the length. A full-scale CM building was constructed having a 2.91 m × 2.91 m plan and 3.01 m height, with 140 mm thick walls and a 100 mm thick reinforced concrete (RC) slab. During construction of the CM building, two vertical holes in panels were provided with an 8 mm diameter vertical reinforcing bar and cast with M20 grade concrete, and the other two were left empty. In addition, 140 × 140 mm RC tie-columns with four 10 mm diameter rebars were provided at the corners. Seismic performance was studied from the standpoint of damage pattern, lateral load carrying capacity, stiffness, deformation characteristics and energy dissipation. A numerical solution based on the finite element method has also been carried out to model the test results. The CM building showed excellent behaviour without any significant damage, hence the system can be adopted for construction of low-to-medium rise buildings, providing speed, sustainability and economy.

Introduction

Masonry construction using burnt solid clay brick units is prevalent for low to medium rise buildings, owing to its properties of durability, thermal insulation, fire resistance etc. However, it suffers from few drawbacks, i.e. tedious and time-consuming construction along with the poor seismic performance. It is well known that past earthquake events have resulted in heavy loss of life and property due to poor seismic performance of masonry. Advancement in masonry construction lead to the development of Confined Masonry (CM), which is a promising structural system due to its confining action, owing to the presence of bond beams and tie-columns at the periphery. Past earthquakes have revealed satisfactory performance of confined masonry as compared to unreinforced masonry buildings. For instance, during Chilean earthquake, 16% of the CM houses were partially collapsed as compared to complete collapse of 57% of unreinforced masonry houses [1]. From the past earthquakes, it has been perceived that, if constructed properly, CM buildings perform significantly well as compared to unreinforced masonry buildings [2]. It was even observed that confined masonry walls performed much better as compared to reinforced concrete (RC) frames with masonry infill due to their structural integrity [3].

Past decades have witnessed significant amount of research on CM using conventional burnt solid clay units. McNary and Abrams [4] examined masonry on a stack-bonded prism so as to access deformational capacity and strength in compression. Kazemi et al. [5]; Bartolome et al. [6]; Alcocer et al. [7]; Tomazevic et al. [8] and Augenti et al. [9] conducted dynamic tests on CM buildings using shake table. Bartolome et al. [6] studied the behaviour of 3-storey half scale CM building model on shake table using solid clay brick units in the direction of motion. Major damage was seen at first storey and no damage on the upper storey. Alcocer et al. [7] found that during large deformations, the damage sequence of masonry units is crushing in the middle of panel followed by concrete crushing and buckling of longitudinal reinforcement bars. Considerable damage was noted in the first storey, wherein the failure pattern was mainly due to shear-sliding mechanism. Yashimura et al. [10] and Tomazevic et al. [8] investigated CM building taking into consideration the confining elements. The interface between confining elements and masonry wall delayed the wall breakdown after the formation of cracks. The rate of strength and stiffness was also degraded significantly. The main limitation of these reduced scale models was noticed when multiple aspects of behaviour were to be studied. Chourasia et al. [11] and Chourasia et al. [12] conducted quasi-static lateral loading tests on full-scale CM building. Superior seismic performance of CM was noted as compared to unreinforced and reinforced masonry buildings.

Limited research has been done worldwide to study the behaviour of different walling units for masonry buildings. Salinas et al. [13] studied the behaviour of CM buildings with cyclic lateral load test on standard (S) and unconventional (U) tubular bricks. Compression and diagonal tension tests were also conducted on the masonry walls. Masonry walls with both standard and tubular bricks showed similar crack propagation. Results showed reduced shear capacity of masonry wall with standard bricks as compared to tubular bricks. Moreover, at ultimate stress, significant cracking with partial destruction of masonry units was observed in standard bricks but uniform cracking was observed in U type bricks. Tomazevic and Gams [14] conducted shake table test on CM building using AAC panels. It was concluded that the seismic resistance of CM using AAC masonry is much dependent on the structural behaviour of tie-columns. Although, the size of tie-columns were not in accordance with the codal provisions, the tie-columns resisted flexure damage and prevented disintegration of CM walls, which lead to satisfactory seismic behaviour of the tested building. Pradeepa et al. [15] studied the performance of masonry using reinforced thermocol panels, which imparted high bending stiffness to the building. Farid et al. [16] studied the performance of masonry building using different AAC sandwich blocks under quasi-static lateral loading. It was found that grooved and wire mesh sandwich panels yielded higher strength as compared to plain sandwich panel. [17] studied the effect on the properties of light weight concrete on adding polypropylene fibers. Literature review reveals research on masonry systems using mainly concrete blocks, precast panels, AAC blocks, reinforced panels etc. However, studies on behaviour of CM using such systems are found to be scarce in literature. Previous studies on seismic behaviour of CM building were mainly focused on CM using conventional burnt solid clay units. Construction using these masonry units is tedious, labour oriented and time consuming. Moreover, burnt solid clay units are brittle in nature, which results in undesirable damage pattern of CM building due to low ductility, low tensile and shear strength along with lack of integral action between masonry units. These limitations call for a need to introduce more robust, efficient and rapid confined masonry construction, which can be achieved by adopting innovative masonry or walling units instead of conventional masonry units in confined masonry.

More than the conception of LWC panel, encompassing the selection of adequate shape, size and raw material, it is essential to define an integrated constructive system with constructive details, mechanical and physical characterization as well as technical, social, environmental and economical sustainability to enable the system in practice. The present study focuses on seismic behaviour of CM using Light Weight Cellular (LWC) panels. A full-scale CM building model was subjected to displacement controlled reversed cyclic quasi-static lateral loading at the roof level. The seismic behaviour pertaining to the buildings was examined in terms of damage pattern, lateral load carrying capacity, stiffness, drift, ductility, structural behaviour factor and energy dissipation. The test results were validated through numerical simulation (finite element analysis in ABAQUS) of CM building using finite element analysis. Single storey, two storey and three storey CM buildings were modeled and analyzed to identify their behaviour under lateral loading. Based on the finite element analysis results, seismic zone factor was computed and recommendations have been made for storey limitation in different seismic zones for the proposed CM building.