FINAL REPORT JOINT RESEARCH (KERJASAMA PENELITIAN ) PT. INDOCEMENT TUNGGAL PRAKARSA Tbk.

Transcription

1 FINAL REPORT JOINT RESEARCH (KERJASAMA PENELITIAN ) PT. INDOCEMENT TUNGGAL PRAKARSA Tbk. PRECAST CONCRETE WALLS USING BAMBOO AS ALTERNATE REINFORCEMENT Ronny Hasudungan Purba, ST., MSCE. (Young Researcher) DEPARTMENT OF CIVIL ENGINEERING UNIVERSITY OF BANDAR LAMPUNG OCTOBER 2007

2 ABSTRACT Experimental and analytical research on Precast Bamboo Walls (DBP), precast concrete walls using bamboo as alternate reinforcement, were performed to investigate flexural behavior, flexural capacity, and crack patterns of the walls loaded by quasi-static one-point loading. The DBP is one of structural components in Precast Bamboo Housing, a new proposed simple housing that are strong, affordable, fast-constructed, decent, and architecturally pleasing. Twelve specimens of 600 mm width, 800 mm length, 50 and 75 mm thicknesses were prepared to study the mechanical behavior of the DBP specimens. Four specimens each are reinforced by bamboo lath of mm thickness, bamboo strips of 25 x 8 mm size arranging somewhat similar to conventional reinforcement on concrete plate, and plaited bamboo strips of 25 x 8 mm size. Bamboo Tali (Gigantochloa apus) was used as the reinforcement with the average value of yield stress, yield strain, tensile strength, and elastic modulus obtained from a preliminary research are kg/cm 2, 2.49%, kg/cm 2, and MPa, respectively. For specimen testing, a quasi-static one point loading was applied in the middle of the specimen. Among the three bamboo configurations used, plaited bamboo strips is concluded the most effective alternate reinforcement. With total cross section area of bamboo (A b = 4800 mm 2 ) used in the specimens, they have been resisted loads more than 2500 kg before failure. In addition, the behavior of the DBP specimen using plaited bamboo strips is considered the most comparable to that of conventional reinforced concrete. Ductile behavior is also observed on the specimen group. Its maximum moment capacity reached times higher than that of the theoretical nominal moment capacity, which is only knmm. Flexural behavior of the specimens reinforced by bamboo strips is considerably different from that of conventional reinforced concrete, sudden and brittle failure on the specimen group caused the highest differences between experimental maximum moment capacity and theoretical cracking moment was only about 15%. The experimental maximum moment in average was only 60% of theoretical nominal moment, which is knmm. A sudden increasing deflection was observed in the moment-displacement relationship curve indicating slip occurred. It is believed due to limited bonding between bamboo reinforcement and concrete. It is concluded that the bamboo strips are not effective to be used as an alternate reinforcement for DBP specimens if special treatments that can increase bonding between bamboo and concrete are not applied. Bamboo lath reinforcement initially expected would significantly simplify and accelerate the application process is concluded not effective to be used as an alternate reinforcement. Bamboo lath has separated the top and bottom part of concrete such that decreasing cross section solidity and capacity. Key words: precast bamboo walls, bamboo reinforcement, Bamboo Tali, cracking moment, flexural moment. i

3 CHAPTER I INTRODUCTION 1.1 General Demand for simple, decent and affordable housing has been increasing in Indonesia. At least one million people are still attempting to afford that need (Indoproperty 2006), and if the demand for simple housing at several reconstruction sites which were previously hit by a devastating natural disaster (i.e., earthquake in Nias and Yogyakarta, tsunami in Aceh, mud-flood in Porong) is counted, that number will significantly increase. Simple housing that commonly found in Indonesia is brick masonry housing. Typically, this one-story building has clay-brick to fill up the walls confined by tie-beams and practical columns, rubble-stones laid as foundation, timber truss, and roof made out of zinc or clay-tiles. Further, Research and Development Department at Ministry of Public Works (Balitbang PU) has published technical guidelines how to construct earthquakeresisting brick masonry housing. However in reality, those guidelines have never been applied properly. Aside from the fact that many constructors are not familiar with those guidelines, the expensive cost spent to build a house following those guidelines is not viable for low-income community. Hence, they frequently neglected the confinement such as the tie-beams and the practical columns on the houses. As a result, these houses which is built without or with very limited confinement are extremely vulnerable to damage and would definitely collapse during a major earthquake shaking such as recently happened at the Yogyakarta earthquake in 2006 (Pariatmono et al. 2006). Another simple housing alternative is bamboo housing. Bamboo is used for the entire structural components such as beams, columns, walls and truss. Compare to brick masonry housing, bamboo housing is relatively cheaper and therefore it is an appropriate option for most of Indonesian who lives at very limited income. Further more, this type of housing, if properly designed and built, can survive during a major earthquake (Marjono 2006). However many people considered, it is inconvenient to inhabit bamboo housing because outdoor weather, especially in the night, can negatively affect the occupant s health. Besides that, if unpreserved bamboos are used for the structural components, they are endangered by beetle infestations that will significantly shorten bamboo housing life cycle. In addition, the stereotype among Indonesian who associated bamboo housing with poverty deteriorates its application (Marjono 2006). The researchers at the Bamboo Center, Center for Technical Study Gadjah Mada University proposed an enhancement design on bamboo housing by introducing horizontal bamboo strips as reinforcement on the walls, afterward plastering the walls with mortar (Marjono 2006). Aligning with the idea of enhancing the quality bamboo housing, a new design of precast concrete house using bamboo as alternate reinforcement and casing is proposed. For simplicity, this new idea is named as Precast Bamboo Housing. The key concept is to combine the advantages of concrete, bamboo, and precast technology developing simple housing that are strong, affordable, fast-constructed, decent, and architecturally 1

4 pleasing. As commonly found in precast concrete structure, the components of Precast Bamboo Housing (beams, columns, and walls) are also first fabricated at one particular side; after concrete reached a certain age, each component is assemble become one complete housing. In this case, beams and columns in Precast Bamboo Housing are composite structure elements with bamboo casing filled with concrete, whereas walls are somewhat similar with conventional concrete plate but with bamboo as the main reinforcement. For simplicity, the three components mentioned are named as Precast Bamboo Beam, Precast Bamboo Column, and Precast Bamboo Walls, respectively. 1.2 Statement of Problem The idea of Precast Bamboo Housing is only an academic concern to propose strong, affordable, and decent simple housing. To this point, no analytical or experimental study is ever conducted to investigate both individual component behavior or structure rigidity of Precast Bamboo Housing that experiencing lateral loads such as earthquake loads. Furthermore, how all components connected to each other as one rigid structure deserves both experimental and analytical study. Particularly in this research that is focused on Precast Bamboo Walls, flexural behavior, flexural capacity, and crack patterns of the walls loaded by quasi-static point loading would be formulated. For this reason, this research is aimed to propose technical recommendations regarding mechanical behavior of Precast Bamboo Walls as a supporting component in a Precast Bamboo Housing. 1.3 Scope and Objectives The research is limited to formulate the mechanical behavior of the Precast Bamboo Walls (DBP: Dinding Bambu Pracetak) through experimental study. The formulated mechanical behavior are flexural behavior, flexural capacity (as structural component somewhat similar to one-way plate), and crack patterns of the walls loaded by quasistatic loads. The experimental results are afterward verified with theoretical analysis. The DBP specimens of 600 mm width, 800 mm length, 50 and 75 mm thicknesses are prepared to study its mechanical behavior. There are three bamboo configurations used as alternate reinforcements, which are bamboo lath, bamboo strips arranging somewhat similar to conventional reinforcement on concrete plate, and plaited bamboo strips (Widyowijatnoko and Mustakim). Concrete compressive strength is designed to achieve 225 kg/cm 2 at 28 day-testing somewhat similar to concrete strength commonly used in practice. Technical data achieved in this research are tensile strength of bamboo reinforcement, maximum point load that the specimens can resist, and specimen crack patterns due to aforementioned loading. 1.4 Advantages of Research Outcomes There are several advantages expected from the research outcomes as described below. 1. Obtaining research data on mechanical behavior of Precast Bamboo Walls which is an useful reference for future research relating to structure rigidity of Precast Bamboo Housing 2

5 2. This research is a key step to accomplish a competitive option of simple housing that are strong, affordable, fast-constructed, decent, and architecturally pleasing. Furthermore, this would also accelerate the fulfillment of community demand for a good quality simple housing. 3. If bamboo can be used as construction materials, bamboo usage therefore would significantly increase. As a result, this would also positively impact micro economic sector among bamboo farmers. 4. One senior college student at Civil Engineering Department, University of Bandar Lampung will get involved in this research. This research can be used as a proposed undergraduate student final project. 3