Scielo RSS <![CDATA[Revista de la construcción]]> vol. 19 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Interface slip model for reinforced concrete columns strengthened with concrete jacketing]]> Abstract Retrofit and strengthening of columns can be an effective solution to improve the capacity of reinforced concrete (RC) structures when the structural details and strength are insufficient to resist extreme loads. When concrete jacketing is used by enlarging the existing RC column cross section, the main concern is the performance loss between new and old concrete due to potential interface slip. There are three major options to improve slip resistance at the interface including surface roughening, dowels, or both. In this study, these methods are evaluated and parameters are proposed to model the load transfer along the interface between the existing and new concrete. The response of reinforced concrete jacketed columns is simulated using the proposed numerical models. The effectiveness and need for surface roughening, dowels, or their combination are investigated. A slip coefficient is proposed to model the friction between new and old concrete materials based on comparison of the experimental data and numerical simulations. <![CDATA[Design of an action protocol for bioconstruction]]> Abstract Numerous elements are to be considered when designing a comfortable and healthy building. We are mainly referring to the site, different construction materials, layout orientation, the presence of power lines and nearby mobile phone antennae, among others. There is an increasingly recognized relationship between where we live or work and our overall health. Along these lines, we have undertaken several studies and measurements of the most influential factors, from the point of view of Geobiology and Bioconstruction. Based on the results obtained and the accumulated multidisciplinary experience, both from the perspective of engineering and architecture, a protocol is proposed to study Biohabitability in differently built containers such as high-rise buildings, houses and inhabited areas in general. <![CDATA[Productivity analysis and efficiency of concrete casting using mini-cranes with a capacity of 200 kg based on appropriate technology]]> Abstract The main objective of this study was to analyze the productivity and efficiency of concrete casting using a mini crane with a capacity of 200 kg as designed by the researcher, compared to using the manual method. The method used in this study is the assembly of mini cranes with a capacity of 200 kg, then field or work tests are carried out and accompanied by observations and subsequent data analysis. The results of the analysis are that using a mini-crane is more profitable compared to the manual method. The authenticity of this research is that mini-cranes are designed and made by researchers with style and models adapted to the conditions of small towns and inland areas in Indonesia, made based on Appropriate Technology not using imported materials and prioritizing scrap metal waste which is the authenticity of this research , thus our research has the principle of producing innovations and works that are useful for human life. <![CDATA[Predicting Marshall stability and flow of bituminous mix containing waste fillers by the adaptive neuro-fuzzy inference system]]> Abstract The practice of using different non-biddable wastes in place of conventional filler is successively extended nowadays, leading it hard to predict the properties of modified bituminous mixes. The present work aims to explore the effect of using rice husk ash (RHA) and fly ash (FA) as an alternative filler in place of conventional filler like hydrated lime (HL) on Marshall stability and flow of bituminous mix by adaptive neuro-fuzzy inference system (ANFIS). This study involves the preparation of samples having seven different bitumen content varying from 3.5% to 6.5% with a 0.5% increment. Mixtures containing 2%, 4%, 6%, and 8% of HL, RHA, and FA separately as filler were fabricated and compared with the control mix (i.e. mix containing 2% hydrated lime as filler). Further, the Marshall mix design procedure was followed to determine the optimum bitumen content (OBC) of each mix. Experimental results showed that the replacement of conventional filler with RHA and FA improved the Marshall properties and decreased the OBC values of the modified mix when added with 4% filler ratio Further, to analyze parameters that are the most influential in the prediction of Marshall stability and flow, a sensitivity analysis using ANFIS network was carried out considering all the input variables. As per the results obtained, the filler types, percentage filler, and percentage bitumen have the most effect on modeling the Marshall stability and flow. Then by utilizing the selected input parameters, the Marshall stability and flow were modeled with Sugeno type ANFIS. In comparison, it is realized that predicted values are closely relevant to the actual one and the prediction ability of the ANFIS is suitable for getting the said values by avoiding the expensive, time consuming, and repetitive laboratory tests. <![CDATA[Delay causes in road infrastructure projects in developing countries]]> Abstract Project delays adversely affect road infrastructure development in developing countries. Unfavorable consequences of project delays involve cost overrun, contractual disputes, arbitration, and quality non-conformities. Despite these risks, literature shows that delays are still a prevalent problem in construction management. Although there is a considerable number of publications on project delays, few studies have compared their causes between developing countries. Therefore, this study aimed to: a) classify and determine the level of influence of the delay causes; b) find the relationship between delay causes and country's development; and c) propose recommendations for mitigating the most critical causes in developing countries. A systematic literature review provided a sample of 14 primary studies from Africa (50%) and Asia (50%). Based on this sample, the study found that developing countries, with a GDP per capita ($US2018) &lt;= $ 2,000, may experience different delay causes depending on the economic and the geographical contexts. In African countries with a Global Competitiveness Index -GCI &lt;= 56, road projects may experience delays due to financial issues of the project owner, as well as delays due to equipment/material issues of the project supplier/subcontractor. On the other hand, in Asian countries with a GCI between 62 and 49, road projects may experience delays due to financial issues of the project contractor, and delays due to planning issues of the project designer/consultant. According to these economic contexts, this study proposes a frame of causes and mitigation actions as a contribution to the risk analysis of road projects in developing countries. <![CDATA[Presenting new models to determine subgrade reaction modulus (Ks) for optimizing foundation calculations in coarse grained soils]]> Abstract Subgrade reaction modulus (Ks) is one of the most important soil parameters to perform structural calculations and analysis. Ks directly affects the determination of dimensions and reinforcement of foundations. Therefore, its exact and accurate determination is of significant importance in terms of economy and safety, especially in large structures. To calculate thecoefficient, it is possible to use either the previously presented experimental relations or directly from field tests such as plate load tests. In the present study, 36 plate load tests (PLTs) were performed on the rigid plates with 20 cm, 30 cm and 45 cm diameters (12 tests on each plate) on coarse-grained sediments of the west of Mashhad, Iran. Then the results were analyzed and a new equation was presented to determine Ks by considering soil and foundation properties no need to costly tests. Then, a new model was presented to generalize the results of plate load tests to actual dimensions of the foundation. Also, the obtained equation and model were validated and results were compared with previous relations and tests outputs. <![CDATA[Optimization of recycled concrete aggregate geopolymer bricks by Taguchi Method]]> Abstract The experimental program was undertaken to investigate the performance of different geopolymer bricks (GB) made with different amounts of industrial waste materials by Taguchi method. Taguchi approach (with L16 orthogonal array) was used to design the experimental plan to reduce the number of experiments as well as to analysis the results. Recycled concrete aggregates (RCA), marble powder (MP) and limestone powder (LP) were considered as the main variables (control factors) to develop the sustainable geopolymeric concrete designated for building bricks. Four responses where density, mechanical properties (compressive and flexural strengths) at 28 days age and the percentage of water absorption were conducted. The test results revealed that combining an eminently RAC, MP and LP can produce GB with 28 days compressive strength of about 36-58 MPa with ambient temperature. The RCA was the most influential factors on the performance of GB due to its performance contribution. Furthermore, the GB containing RCA is suitable for environment friendly construction and is comparable to a normal GB made with natural aggregate. <![CDATA[Effect of tunnel depth on the amplification pattern of environmental vibrations considering the seismic interactions between the tunnel and the surrounding soil: A numerical simulation]]> Abstract The amplitude and frequency of seismic waves caused by an earthquake are modified according to the physical characteristics of the subsurface. Further modification is due to soil - structure kinematic interactions between the subsurface medium and the seismic waves. Analysis of ground motion and subsurface propagation of a seismic wave in the presence of an underground structure needs to include appropriate ground input motion parameters. In order to ensure the protection of important engineering structures, and to prevent environmental damage under earthquake excitation, the dynamic response of the vibrating underground structure needs to be carefully analyzed in terms of wave propagation problems. The aim of this study is to evaluate the effects of the amplification on free field motions, including the underground structure, when considering the tunnel-soil interaction, using numerical tools. The 2-D finite element method was used as a numerical model to determine the magnification effect of seismic excitation with various frequencies, on surface vibration, in the presence of a tunnel structure. Results showed that the presence of underground structure amplified the seismic vibrations on the free field and tunnel, depending on the frequency of the external load and the local soil condition. <![CDATA[Safety in the construction industry: accidents and precursors]]> Abstract Construction sites represent complex environments with particular characteristics and high baseline levels of risk in which accidents are a main point of analysis in much of the studies in the literature. Despite the inertia behind this accident-based focus, though, there is criticism that such a reactive approach often involves unreliable information about the special characteristics of the construction site and that the use of lagging indicators is not appropriate. Current trends have taken proactive approaches and made use of analyses based on precursors or leading indicators, which aim to foresee safety issues before they turn into actual incidents. But these two focuses are not independent, and new proactive measures must be developed and rigorous empirical validation. The objective of the current work is to present a critical review that considers these two approaches based on a meta-classification of studies on health and safety on construction sites. <![CDATA[A comparative study on ASCE 7-16, TBEC-2018 and TEC-2007 for reinforced concrete buildings]]> Abstract Doctrines of earthquakes and also the latest approaches of earthquake resistant building design in standards need to be revised periodically. While the revisions and updates in the American standards occur over periods of three or five years including limited subjects, in Turkey the same revisions are done once over long periods including the whole subjects of the standards. As examples the standards of 1975, 1998, 2007 and finally 2018 could be given. Especially, in 2018 standard (TBEC-2018) many changes were made over concepts and criteria. The procedure of calculating the earthquake loads in 2018 standards is similar to the one in the American standards of (ASCE-7-16), however for the element design the changes are shown as developments over the one of 2007 earthquake standard (TEC-2007). The changes made by 2018 standard for calculations of earthquake loads and their effects on civil engineering are very important factors of new building design. The earthquake load affecting a building which is the first factor of earthquake resistant building design shows important differences according to the condition changes in the standard. Based on this motivation in this study reinforced concrete frame type buildings of different elevations were researched by using ETABS (structural software for building analysis and design) according to linear equivalent seismic load method. According to the analysis results of the chosen buildings, a comparison forthe base shear force, top displacement and relative story displacement between TEC-2007, TBEC-2018 and ASCE 7-16 standards was carried out. From the analysis results, it is found that for most of the soil classes while the maximum base shear forces in 3 and 5- story buildings are achievedat TEC-2007, the maximum base shear forces in 7 and 9- story buildings are achieved at TBEC-2018. Also, it is predicted that the higher increment in the design forces of buildings with higher elevations is obtained at TBEC-2018 for strong soils, and at TEC-2007 for weak soils. By considering cracked sections at TBEC-2018 the calculations displacement and period was affected as periods in TBEC-2018 were increased by almost 34% respected to TEC-2007. The same increment ratio was determined for ASCE 7-16 as 45%. Also, as a response for the increments in period, the spectral acceleration determined from the elastic spectrum diagram was decreased. At the end of the study, nonlinear performance analysis was also performed and performance points were determined according to the demand spectra of the seismic codes. ASCE's demand displacement values are in any case lower than Turkish codes. TBEC-2018 reveals less displacement demands in high-rise buildings than TEC-2007. The closest results for the three regulations occurred on the softest grounds.According to the results obtained from the static pushover analysis, a ductile behavior occurred in all of the structural systems and plastic hinge mechanism started from the beams firstly. <![CDATA[Cold formed steel storage racks subjected to axial, shear and bending interactions]]> Abstract This research article aims to study the behaviour of expansion bolts under axial, shear and bending interaction of base plate connected cold formed steel storage racks. The uniaxial moment of rotation at the base plate connection was adopted to identify the ultimate moment of resistance and stiffness of the base plate connected to a concrete block using M10 grade anchor bolt at different range of axial loads ranging from 25% to 100% there by the design strength of upright profile was studied. The dimension of the upright and the base plate thickness has to be changed so that the extreme stability under various ranges of axial and transverse loads had been studied. Using finite element analysis software (Abaqus), a model has been created and designed to observe moment rotation characteristics, behaviour of base plate under simultaneous axial, shear and bending interactions and compared with experimental analysis. Comparative studies reveal that there was no failure in the concrete block and when the upright thickness increases, the stiffness and moment of the base plate increases despite having a similar cross section. An interaction equation was developed to find the stiffness and ultimate moment of resistance of the base plate connection. <![CDATA[High-temperature effects on white cement-based slurry infiltrated fiber concrete with metakaolin and fly ash additive]]> Abstract In this study, the high flexural parameter properties of Slurry Infiltrated Fiber Concrete (SIFCON) were examined, as was the use of metakaolin and fly ash with PC CEM I 52.5 R (White Cement). 5 series were prepared and metakaolin and fly ash replaced PC CEM I 52.5 R at 25% and 50%. In this study, while researching White Cement in the production of SIFCON samples, metakaolin which is easy to obtain in kaolin-rich soils, and fly ash, which is a waste material, were also evaluated to reduce CO2 emission in cement production. 5% of steel fiber was used in all series and the results of 7 and 28 days flexural and compressive strengths and ultrasonic pulse velocity (UPV) were examined. Given the 28-day test period, a strength increase was observed in metakaolin-added samples, while lower results were obtained in fly ash-added samples since fly ash was not yet completely hydrated. After the 200, 400, and 600 °C high-temperature tests, the results of flexural and compressive strengths, UPV, and weight loss were examined. The increase in strength after 300°C can be caused by drying shrinkage of the matrix, whose C-S-H structure is not yet intact, and compression of the fiber wall. The conversion from Ca(OH)2 to CaO begins at about 400°C, and the C-S-H structure is quickly destroyed as it approaches 600°C. SIFCON samples have the highest mechanical and durability properties by replacing the metakaolin with White Cement by 25%. The lowest results were obtained by replacing the fly ash with White Cement by 50%. <![CDATA[Improving cost performance in design-bid-build road projects by mapping the reasons for cost overruns into the project phases]]> Abstract Design-Build (DB) is an alternative project delivery system that has shown to be better in controlling cost growth than the traditional Design-Bid-Build (DBB) system. However, some road administrations are not legally allowed to implement DB and keep using DBB with consequent disadvantages, such as having high-cost overruns. There is a need, therefore, to provide road administrators delivering DBB projects with research-based mitigation measures that can help them to minimize the main reason for cost overruns. To this end, this study identifies the main reasons for cost overruns in the design, the procurement and the construction phases of DBB road projects and point out to the specific elements of DB project delivery that might help to minimize these reasons. To identify the reasons, an exploratory content analysis was performed on interviews conducted with 41 professionals involved in road project management in Chile. Literature review and document analysis of DB were used to analyze the identified reasons under the framework of the DB practice in the United States. The results showed that four elements based on the DB approach might be used to minimize cost overruns in DBB projects: (1) in the design phase, road administrators should consider the early integration of the constructor’s expertise. In the procurement phase, they should establish (2) instances for effective information exchange and (3) a goal-oriented selection process. Overall, road administrators should consider (4) establishing a one-point of high-level accountability for the design, the procurement, and the construction phases. This study will serve DBB road administrators to start the transition from DBB to more collaborative approaches that will help to minimizer cost overruns and, therefore, to improve the project cost performance. <![CDATA[Modelling of compressive strength of self-compacting concrete containing fly ash by gene expression programming]]> Abstract In the modelling study, two models are presented by gene expression programming (GEP) for estimation of compressive strength (f c ) of self-compacting concrete (SCC) produced with fly ash (FA). The main difference between two models is the number of heads determined in the development of models. Two established models are proposed to predict the f c values by utilizing the amount of cement, water, FA, coarse and fine aggregate, superplasticiser and age of specimen as input values for SCC mixtures. In the establishment of proposed models, 516 f c values are utilized. These values were obtained from 34 different published scientific experimental studies on the SCC produced with FA. The training and testing sets employed in the creation of models consist of 368 f c results of SCC mixtures. The models are validated with the remaining 148 f c results of SCC mixtures, which are not employed in training and testing sets. The estimated f c results attained from established models were compared with f c results of experimental studies, and previously proposed artificial neural network (ANN) model. These comparisons and the results of statistical evaluation have strongly revealed that the results of established models match well with the experimental results, and they are considered very reliable. <![CDATA[Analysis of the fire resistance of normal wooden doors exposed to fire conditions]]> Abstract Meeting passive and active protection requirements in buildings has brought about demands for new systems, materials, equipment, and even design requirements like the access to housing units with doors that have a minimum fire-resistance rating of 30 minutes. For existing buildings, though, it is not always possible to adapt them to current government regulations, and normal low-cost doors usually do not comply with compartmentalization requirements. Therefore, this study aimed to evaluate the fire resistance of normal wooden doors and low-cost compensatory measures to increase the protection of existing building elements. The lab tests were performed on real-scale wooden door prototypes. Moreover, three protective solutions were tested while added to the doors: (a) fire-rated gypsum boards, (b) cement boards, (c) steel sheet with polyethylene terephthalate felt, in addition to the reference door. It was noted that only the prototype with cement boards managed to resist for 30 minutes. This result evidences the existence of alternative low-cost solutions that can be used in simpler buildings, although some of the usual options may not be able to meet the requirement. <![CDATA[Mechanical and flexural performance of self compacting concrete with natural fiber]]> Abstract This paper investigates the effect of sisal fiber addition on fresh ,mechanical properties of self compacting concrete(SCC) and flexural performance of fiber reinforced RC beams made with mineral admixtures like Meta Kaolin (MK) and Fly Ash (FA)which is an industrial waste. The mixes were prepared by varying MK content from 5% to 15% with 5% increment with constant fly ash content of 30%. The results reveal that increasing the content of MK beyond 10% leads to reduction in strength. And also the negative influence of MK and fiber addition on workability performance was overcome by the addition of FA, super plasticizer and viscosity modifying agent (VMA). Based on the test results it is evidenced that FA and MK make use of mineral admixture in the production of SCC. It also clarifies that the addition of sisal fiber improves mechanical properties of concrete. The research work shows that the ultimate load of fiber reinforced RC beams was raised when compared to normal RC beams. The flexural toughness and ductility of concrete was found to increase appreciably when sisal fiber was added.