Asian journal of civil engineering
Volume:15 Issue: 3, Jun 2014

This study focuses on the application of interval type-2 FLC (IT2FLC) in active tuned mass damper (ATMD) for the control of a building modeled as a single degree of freedom (SDOF) system. Since taking the first mode of a structure gives a good approximation of the building response, a SDOF system which demonstrates the characteristics of the first structural mode is used. One of the main shortcomings of the type-1 fuzzy systems is their inability to consider uncertainty in fuzzy rules. IT2FLS has the ability to handle this problem. It also takes into account uncertainty in loading and structural behavior. To evaluate the efficiency of the proposed control method, an 11-storey realistic shear building is used. The IT2FLC is designed for the first mode characteristics of the mentioned structure for getting the maximum response reduction under different types of earthquake excitations. The results obtained by proposed control scheme were compared with those of uncontrolled structure, structure with TMD and structure with ATMD through type-1 FLC. Numerical results indicate that IT2FLC is very effective in reducing the structural responses compared with that of the type-1 FLC. It is also found that designing the proposed controller for the first structural mode can significantly reduce the structural response of realistic building.

Self compacting concretes (SCC) containing quartz powder are sensitive to spalling, when exposed to fire. It was attempted to modify the fire resistance of this kind of SCC with use of additives. As a case study, expanded perlite aggregate, zeolite powder and a mix of them was added to the SCC recipes and their fire behaviors were evaluated. The specimens were exposed to high temperatures, up to 1000°C and their residual compressive strengths were measured. The SCC specimen containing zeolite powder additive suffered from explosive spalling. But, the addition of expanded perlite and mix of perlite/zeolite resulted in considerable improvement of fire resistance of samples.

Experimental investigations have been carried out on five specimens, out of which three were of single-draped tendon profile and two were of straight tendon profile. Rectangular RC beams of section size 150 mm X 275 mm with 4 m length were used for investigation. Crack was induced in RC beams to a limit in which strain in reinforcing steel was around 85 % of the yield strain by monotonically increased static two-point load at flexural zone. Strengthening by external prestressing was done while the member was subjected to superimposed dead load of a bridge girder, equivalent to 25 % of the calculated ultimate load of the specimen. Strengthened members were tested by monotonically increased two-point load. Role of the reinforcing steel were observed from electrical strain gauges, which were fixed throughout the length of the beams. It was observed that the ultimate load carrying capacity of strengthened members have increased 48 % and 17 % for single-draped tendon profile and straight tendon profile respectively.

Technological advances have provided new ways of combating corrosion. Corrosion inhibitors are one means of protection for reinforced concrete structures. The effectiveness of commercially available inhibitor for concrete has been investigated. This study focuses on the effects of benzotriazole inhibitor on ordinary concrete and high performance concrete. The strength and durability property of different dosage of specimens without and with inhibitors on ordinary concrete and high performance concrete was compared. Corrosion tests such as Alternative Current (AC) impedance, Open circuit potential, Long term Potential Resistance (LPR) sweep, Custom sweep, and Half-cell potential were also conducted and compared with ordinary and high performance concrete without and with benzotriazole inhibitor. The inhibitor shows better performance strength, durability and good corrosive resistance.

This paper compares the indoor environment of ordinary and container classrooms in a number of schools in Austria. Temperature, relative humidity, and carbon dioxide concentration were measured. Moreover, teachers in each school were handed a questionnaire inquiring about factors such as ventilation practices, air quality, and thermal comfort in their classrooms. The results of the study suggest a slightly inferior indoor environmental performance of the container schools as compared to ordinary schools.

Externally bonding of fiber reinforced (FRP) sheet to reinforced concrete (RC) beams has become a popular flexural strengthening method in recent years. The ultimate flexural strength of those strengthened beams can be improved efficiently, but it is often prevented by premature failure modes, such as sheets end interfacial debonding. This paper proposes an effective method to prevent sheets end interfacial debonding. Hence, an experimental and analytical study conducted to verify the efficiency of the proposed method. Therefore, nine concrete beams with dimensions of 100 mm width, 160 mm height and 1200 mm length were manufactured and tested. Eight specimens were strengthened in flexure with various numbers of CFRP layers and different sheets end strengthening methods. From the test results of this study it is conducted that the design guidance of ACI 440.2R-02 and ISIS Canada overestimates and the developed method by Toutanji et al. underestimates the flexural strength of CFRP strengthened RC beams at yielding. Also, applying the proposed method to sheets end strengthening, prevented sheets end interfacial debonding and increased load carrying capacity of those strengthened beams by 26% and 32%. The ductility (i.e. Δ_u⁄Δ_y) of those strengthened beams increased by 77% and 90%.

The influence of nano-TiO2, nano-Al2O3, nano-Fe2O3 and nano-ZnO2 on durability and mechanical properties of concrete was experimentally investigated. For this purpose, compressive strength tests were conducted in order to investigate the effects of nano particles on mechanical properties of concrete. Moreover water absorption and freeze and thaw tests were conducted to explore the effect of nano particles on durability of concrete.Results of this study showed that all the examined nano particles can improve durability and mechanical properties of concrete. The contribution of nano-TiO2 on improvement of mechanical properties and durability of concrete was more than the other nano particles.

The development of self-compacting concrete marks an important mile stone in improving the product quality and efficiency of building industry. SCC homogeneously spreads due to its own weight, without any additional compaction energy and does not entrap air. The required flowability is achieved by using more fines (cement +filler) and reducing coarse aggregate content. The present research work was aimed to develop SCC by using Lime stone quarry fines and fly ash as filler and to study its effect on abrasion resistance of Self Compacting concrete. The test results indicate that the SCC mixes with lime stone quarry fines and fly ash significantly improved the depth of wear, compressive strength, tensile strength and flexural strength.

This article presents an optimization problem for accomplishing seismic design of Reinforced Concrete (RC) dual systems and RC frames. The charged system search algorithm is chosen for the optimization. An efficient structural modeling is also presented for this purpose. Here, first databases are constructed according to ACI seismic design criteria for beams, columns and shear walls. Formulations for optimum seismic design of dual systems (shear wall-frame) are proposed. With some manipulations on these formulations, optimal seismic design of RC moment resisting frames is also performed. This procedure is together with ordinary design constraints and principal seismic design constraints. These constraints consist of beams, columns, shear wall design criteria, and some seismic design provisions. Cost of the structure is defined as the objective function. Based on the results of the design examples, the proposed methodology can be considered as a suitable practical approach for optimal seismic design of reinforced concrete moment resisting frames and dual structural systems consisting of structural wall.

High performance concrete (HPC) has become more popular in recent years. However, mix proportioning of HPC is a more critical process than normal strength concrete (NSC). Mix design methods of NSC are not directly applicable for designing HPC mixes. Tropical countries usually show substantial variations in temperature and humidity. These variations have profound effect on properties of HPC as mix proportions are usually decided at laboratory conditions. Therefore, mix design of HPC in tropical climate requires special attention to incorporate the variation in its properties. This paper presents a new method for proportioning HPC mixes considering effects of varying humidity and temperatures by exposing them to different artificially created environments. Proposed method is experimentally found to be valid and provides mix proportions giving desired workability and strengths.