Iranian Journal of Science and Technology Transactions of Civil Engineering
Volume:37 Issue: 2, 2013

Assessment of the effectiveness of ferrocement strengthening techniques i.e., cast in situ Ferro-mesh layers and precast ferrocement Laminate is the aim of this experimental investigation. To accomplish this objective, ten (10) reinforced concrete beams including one control beam have been intentionally designed and detailed to fail in flexure. Prior to strengthening, beams have been tested under two-point loading till service limit. Beams have been strengthened in the flexural dominant region only and tested to failure under the same loading arrangement. It has been concluded that strengthening through cast in situ Ferro-mesh layer is the most efficient technique, whereas strengthening of the beams by using precast Ferrocement Laminate B is not only easy to implement at household level, but is also promising in terms of enhancing load carrying capacity, stiffness and ductility.

Many reinforced concrete structures are exposed to corrosive environment which can lead to damage of the reinforcing steels. These members include coastal structures subjected to wind-born salt spray and seawater, as well as bridges beams and decks subjected to deicing salt. Design engineers should prevent the deterioration of reinforcing steel, especially transverse stirrups. Using FRP materials in new concrete members has attracted researchers’ interests due to FRP high resistance against corrosion. Distance of FRP stirrups plays a key role in the cyclic behavior of joints and energy absorption magnitude. In this study, experimental and finite element investigations have been studied to assess the effects of stirrup distances on the cyclic behavior of concrete joints. In the experimental study, two half-scale concrete joints with the same beam and column dimensions and longitudinal steel reinforcing characteristics but different distance of transverse FRP stirrups were tested under cyclic loading. Besides presenting and analyzing the main results and photographs of the experimental tests, the made ANSYS finite element models were compared and validated with these tests. Moreover, the distances of FRP stirrups were varied in finite element models. According to experimental and finite element method results, the joints with congested stirrups had not only higher ductility and energy dissipation, but also had additional capacity, as much as 12% relative to the non-ductile joint with wider distance stirrups.

Endurance Time (ET) method is a recently developed response-history based analysis procedure for seismic assessment and structural design in which structures are subjected to a predesigned intensifying excitation function, and their performance is evaluated based on their response at different excitation levels. Generating efficient excitation functions, which is essential for functionality of the method, leads to a complex large-scale optimization problem. In this paper, the Covariance Matrix Adaptation Evolution Strategy (CMA-ES), which has found many applications in solving continuous optimization problems, is employed to produce the excitation functions. The results reveal the good performance of the algorithm in generating ET excitation functions (ETEF) with reasonable accuracy and time efficiency.

In this paper, the influence of increasing the height of building on the seismic behavior of dual structural systems in the form of steel moment resisting frames accompanied with reinforced concrete shear walls has been investigated. Common structures experience inelastic stage of behavior encountering the seismic loads and the applied energy will be dissipated. The nonlinear responses of the structural models have been evaluated in this research. As a result, some parameters such as ductility factor of structure (μ), over-strength factor (Rs) and response modification factor (R) for the mentioned structures have been studied. To achieve these objectives, the buildings have 10 and 20 stories and contain such structural systems used to perform the pushover analyses having different load patterns. Regarding the results, it seems that the response modification factor (R) for the mentioned structural system is assumed to be higher than the value which is used in Iranian Code of Practice for Seismic Resistant Design of Buildings [Standard No.2800]. Analytical results showed that the ductility factor and the response modification factor increased as the structure height increased. In contrast, the over strength factors increased by decreasing the height of the structure.

The complicated problem of truss shape and size optimization with multiple frequency constraints is investigated in this paper. A recently developed metaheuristics called teachinglearning- based optimization (TLBO) algorithm is used for the first time to solve this kind of problem. Contrary to other metaheuristics, the procedure of TLBO is simple to implement since no tuning parameters need to be adjusted. Analyses of structures are performed by a finite element code in MATLAB which is used in conjunction with an optimization code based on TLBO. Various benchmark problems are solved with this technique and the results are compared with those found by other methods including metaheuristics such as PSO, HS and FA. In all test cases, the results show that TLBO leads to very satisfactory results i.e. lighter structures which satisfy all frequency constraints. The results of this study indicate excellent inherent capacity of the approach in dealing with complicated dynamic non-linear optimization problems.

Surveys of the literature indicate that shell foundations are economical structural elements which can be considered as the alternatives of flat foundations. However, the advantage of shell elements in geotechnical engineering has not been explored yet, and these foundations are still being treated as flat footings. The objective of this study is to investigate the geotechnical behavior of two types of shell foundations under axial loading and present a comprehensive formulation for bearing capacity of such foundations. For this purpose, a series of laboratory tests were carried out on six types of shell foundations, namely conical and pyramidal shell foundations. Different shell foundation geometries and Buckingham-Pi theorem were employed to formulate the ultimate load capacity. Experimental results from previous investigations on shell footings were used to verify the proposed formulations. Results of the present laboratory tests have indicated that the pyramidal shell foundations show higher bearing capacities compared to their corresponding conical ones and as the thickness of foundation increases, bearing capacity decreases. Also, load bearing capacity equations of shell foundations determined from dimensional analysis have shown a reasonably good agreement with experimental results.

Chaotic analysis has been performed on the river flow time series before and after applying the wavelet based de-noising techniques in order to investigate the noise content effects on chaotic nature of flow series. In this study, 38 years of monthly runoff data of three gauging stations were used. Gauging stations were located in Ghar-e-Aghaj river basin, Fars province, Iran. Noise level of time series was estimated with the aid of Gaussian kernel algorithm. This step was found to be crucial in preventing removal of the vital data such as memory, correlation and trend from the time series in addition to the noise during de-noising process. A comprehensive chaotic assessment was conducted to study the relationship between the wavelet noise reduction processes and the changes in the chaotic behavior of the river flow time series. To investigate the time series chaotic behavior, some of the most common non-linear criteria are utilized which are distinguished as the chaos indicators. The changes in the signal’s average power, the Lyapunov exponents, the correlation dimension and the reconstructed phase space were estimated. Studying the average signals power analysis’ results presents the evident impression of de-noising procedure on the river flow time series. The variations of the Lyapunov exponents of time series as a consequence of preprocessing indicated a significant influence of the wavelet based de-noising on revealing the time series chaotic behavior. Results depicted that the lesser noise components result in lowering the largest Lyapunov exponents. Besides, fractal dimension and correlation dimension of the denoised series were almost the same while they were totally different before de-noising. This also confirmed the commonly claimed sensitivity of correlation dimension to the existence of noise. The correlation dimension results depicted an obvious difference between the signal’s chaotic behavior before and after the do-noising procedure. Changes in the reconstructed phase spaces were also noticeable after de-noising process by wavelet techniques. Results confirm the importance of de-noising before any chaotic assessment. Also, results show that a chaotic phenomenon such as river flow may depict completely random behavior due to the noise content within it. Therefore, in order to better explore inherent chaotic behavior of natural time series, such pre-processing can accompany common chaotic assessment procedures.

Microtremor data have been carried out for microzonation studies and disaster mitigation in urban areas. Over a period of two decades, the Nakamura’s H/V spectral ratio method was recognized as a simple and cost effective method in seismological geotechnics. In order to identify the soil layers characteristics, microtremor measurements were performed in 6 different regions in Iran. These sites are located in different parts of the south, center and east of Iran. Regarding the study, 471 recorded microtremors on an area about 700 km2 were processed. In addition, the results of 227 refraction tests, 386 electrical resistivity tests and 197 boreholes were evaluated. Based on the analysis results, the resonance frequency of each station was estimated from the peak of the H/V spectral ratio components. Conducting the boreholes or geophysical investigations enabled the thickness of the sedimentary cover to be determined. Different places were selected as study areas namely, Bam, Bushehr, Qeshm Island, Mashhad, South Pars, and Qom. In order to develop the sedimentary thickness, an attempt has been made to derive a formula to correlate the frequency of the horizontal-to-vertical, (H/V) spectral ratio peaks (f0) to the sedimentary cover thickness (h). The obtained equations in the different sites indicate that the relationship between these two parameters has a power form and it is significantly affected by the subsurface topography and material properties. It is also observed that both shape of basin and sedimentary thickness have a significant influence on the relation formula parameters.

Although the collection of a detailed, accurate and sufficient volume of information, and subsequent timely delivery are vital for effective quality control and management in construction, existing methods for material and specimen tests and laboratory activities are manually reliant on the human recourse to paper and pencil. Data collected using manual methods are time and labour-intensive. They are also error-prone due to the reluctance of workers to monitor and record the flow of large quantities of tests. This study investigates an automated approach that deals with a Radio Frequency Identification (RFID) facilitated quality management system. The proposed system focuses on the gathering, monitoring, managing, and sharing of accurate data amongst all participants (i.e. consultants, contractors and owners) and also in the material test laboratory. In this research, the need for a new coding system is highlighted in which RFID tagging has to be taken into consideration. In order to automate the task of specimen identification and quality data collection in any laboratory activity, each RFID tag is equipped with a unique Electronic Specimen and Test Code (ESTCode). An ESTCode is used as a specimen and test identity code, which forms the base of reports and contains related information for a particular specimen and test. In order to form the backbone of technology adoption in real scenarios, and to identify driving factors in this field, this paper also introduces an implementation framework for the selected technology in construction quality management.

Many studies have shown that individuals’ responses to urban traffic congestion, as usually assumed by policymakers, are significantly different from their respected actual behavior. This paper adopts a behavioral approach to examine this difference, using the design of experiment principles and binary logit models. In this approach, five transportation demand management (TDM) measures including three push and two pull measures were investigated. Then, effects and contributions of the measures in diverting car commuters to seven existing non-car modes were taken into account. This study uses the stated preferences of 288 individuals who regularly use their private cars to access their job locations in the central Tehran area, to calibrate seven non-car mode models. The results show that when considering each mode separately, pull measures are necessary to regulate the market share of each non-car mode. Analysis of the effects of the measures in considering non-car modes shows that although their contributions are about 14% for transit accessed by walking and 7% for taxi, they have never contributed more than 5% to other modes.

This research presents an efficient and reliable swarm intelligence-based approach, ant colony optimization and elitist-mutated particle swarm optimization. Methods of particle swarm optimization (PSO) and ant colony optimization (ACO) and elitist mutation particle swarm optimization (EMPSO) are co-operative, population-based global search swarm intelligence metaheuristics. PSO is inspired by social behavior of bird flocking or fish schooling, while ACO imitates foraging behavior of real life ants and Elitist mutation taken from genetic mutation from genetic algorithm techniques. In this study, we explore a simple approach to improve the performance of the PSO method for optimization of multimodal continuous functions. The proposed EMPSACO algorithm is tested on several test functions from the usual literature and compared with PSO, PSACO and GA (Genetic Algorithm). Results showed that the effectiveness and efficiency of the proposed EMPSACO method had suitable accuracy to optimize multimodal functions.

The purpose of this study is to identify the way of dealing with the components of project implementation in civil projects of Shiraz University (SU) and Shiraz University of Medical Sciences (SUMS), to compare the executive indicators in civil projects of both universities. Indeed, results of studies on executive indicators of civil projects at SU and SUMS have been presented as articles at the Second International Conference on Construction and Project Management ICCPM 2011 in Singapore; and the International Conference on Civil Engineering and Transportation ICCET 2011 in Ji Nan, China, respectively. This study, however, focuses on the comparison between the executive indicators of the civil projects at both universities; based on the ideas of the decision-makers and authorities of the projects. In this study it has been found that the difference between some indicators is small. It means that the ideas of both groups in bothuniversities are similar or close to each other; which may show the accuracy in completing the questionnaire and the methodology used. In this paper, the results of this comparative study are presented and discussed.

Research is underway to increase the strength of concrete with the addition of chemical and mineral admixtures. The use of High Range Water Reducers (HRWR) has been increased many times in the last two decades. In this research the effect of two types of commercially available HRWR (Superplasticizers) are studied on the properties of concrete in fresh and hardened state. The strength development characteristics of concrete have been studied with the addition of the HRWR. The research has shown the selection of appropriate HRWR for the desired results of concrete in fresh and hardened state is a critical decision for the performance of the WRWR.