Advanced Materials Research Vols. 931-932

Abstract: Shear strength prediction of simple deep reinforced concrete beams by method of strut-and-tie model is presented in this paper. The tested specimens were designed according to Appendix A of ACI 318-11 code with variations of shear span-to-effective depth ratios and ratios of horizontal and vertical crack-controlling reinforcement. Test results revealed that at the same shear span-to-effective depth ratio, the various crack-controlling reinforcements significantly influenced on strength reduction coefficients of strut and failure modes. When the shear span-to-effective depth ratios were increased, failure modes changed from splitting diagonal strut to flexural-shear failure. Based on the test results, the proposed model was compared with Appendix A of ACI 318-11code.

Abstract: This paper presents the test results on the shear behavior of reinforced concrete deep beams with six steel reinforcement configurations. They were designed in accordance with the method given in the ACI 318-11. The specimens were subjected to the single concentrated loading at mid-span. The horizontal to vertical reinforcement ratios and shear span-to-effective depth ratios were the variables studied. The shear span-to-effective depth ratios of the beam specimen were between 1.5 to 2.0. The strut-and-tie model was used for the analysis. The test results indicated that the first diagonal cracking load and the failure mode were controlled by the horizontal to vertical reinforcement ratios and the shear span-to-depth ratios. The tests consistently gave the strength values slightly less than those calculated by using the ACI model. A modified ACI model for strut-and-tie was thus proposed and was found to accurately fit the experimental results.

Abstract: This study presents use of an approach which links the Latin Hypercube technique with Crank-Nicolson based finite difference approach for probabilistic assessment of chloride diffusion through silane-treated concrete. There are six random variables; (1) surface chloride, (2) diffusion coefficient, (3) first application time, (4) subsequent application time, (5) effective duration, and (6) cost of silane treatment. By different application times, three repair strategies are proposed. With silane treatment, the diffusion of chloride ions in silane-treated zone is retarded leading to the extension of the time which the chloride content at a threshold depth reaches the critical value of rebar corrosion and concrete cracking. Based on this extension, the time-dependent risk of rebar corrosion and concrete cracking is defined, and the time-dependent ratio of cumulative cost of silane treatment to benefit (percent reduction of the risk) is calculated. And, the best strategy based on the ratio of cost to benefit is justified.

Abstract: Ground movements triggered by the Bukit Tinggi earthquakes in 2007 to 2009 are believed to be the possible cause of several structural damages on a secondary school building of SMK Bukit Tinggi, in the state of Pahang, Malaysia. This paper describes the ambient noise study conducted on the damaged building (a 4-storey reinforced concrete frame laboratory building) and the adjacent buildings using tri-axial 1 Hz seismometer sensors. Fourier amplitude spectra (FAS) analysis was applied to determine the buildings natural frequencies for vulnerability assessment of the damaged structure in both longitudinal and transverse axes. Significant multiple peaks of FAS curves used for natural frequencies determination of the buildings show values between 4.18 to 4.34 Hz, 5.04 to 5.23 Hz, 6.07 to 6.54 Hz and 8.17 to 8.81 Hz, indicating the existence of translational and torsional vibration modes acting on the buildings. Differences in dynamic behaviour between the laboratory and the adjacent buildings may be responsible for the structural damages due to the independent structural response and excessive torsional effect during the Bukit Tinggi earthquake tremors.

Abstract: The highway live loadings, HS20-44, stipulated by Association of State Highway and Transportation Officials (AASHTO) are different from Thai truck weights according to government gazettes issued by Department of Highways. This article aimed to study the strengthening costs of the bridges due to Thai trucks. The reinforced concrete solid slab bridges with the span length ranging from 5 to 10 meters were selected to study. It was found that the bridge responses due to Thai trucks were greater than those from AASHTO loads. The average strengthening costs were approximately 6,958 Baht/sq.m and highest at 7 m-span length. The results of this study would be a reference data to create an alternative plan for bridge strengthening in Thailand in order to sustain the bridge safety level recommended by AASHTO.

Abstract: New horizontally mounted bender element devices capable of high-quality transmission and reception of horizontally propagated shear waves polarized in orthogonal planes across the mid-height of a sand specimen are described. Mounting of these bender elements is on the membrane, attaching on the side wall of the reactor container. This technique is suitable for use on samples down to 80 mm length. The effective fabrication procedures that have been developed are described. The instrumentation systems used to drive and receive signals are outlined, and estimates of the magnitude of the shear strains developed by the bender elements and the accuracy with which shear wave velocities can be determined are discussed. The sand specimen is treated by the solution then its strength is developed. These new bender elements enable shear modulus to be measured before, during and after the treatment.

Abstract: To investigate the unsaturated soil properties, the measurement of volume change is dealt with both water and air volume changes. It cannot be defined by using only the volume of water flown in out from the specimen as saturated soil. This paper presents the volume change measurement by using image processing (IP) from the series of consolidated undrained (CU) and constant water content (CW) tests for saturated and unsaturated conditions of soil, respectively. The results, obtained between IP and the cell liquid measurement considered movement of piston and the cell expansion effect with pressure including creep, are good corresponding except the specimen has an irregular deformation.

Abstract: A strut-and-tie model (STM) has been used as a rational and simple method for analysis and design of reinforced concrete deep beams. The STM idealizes the discontinuity regions in such members as a truss-like structure consisting of compression struts and tension ties. The strength of a deep beam is usually controlled by the capacity of the diagonal concrete struts which is generally proposed in terms of the concrete strength and the efficiency factor. The efficiency factor accounts for the variation of the concrete material and the compression softening effect. One has been used in many STMs and often exhibit biases and uncertain errors in prediction of the shear strengths of deep beams. This uncertainty is due to the imperfection of formulation, missing parameters, and insufficient experimental data. Based on a database of 406 test results and six state-of-the-art formulations of the efficiency factors found in the international building codes and literature, this paper proposes improved STMs for accurate prediction of shear strength of simply supported reinforced concrete deep beams by correcting the bias and quantifying the scatter using a Bayesian parameter estimation method.

Abstract: This paper presents the limit state shear design formulas for both normal and high-strength reinforced concrete deep beams using strut-and-tie model (STM). The proposed equations are based on the STMs with six state-of-the-art efficiency factors. These STMs were improved by correcting the bias and quantifying the scatter using a Bayesian parameter estimation method. The statistical parameters of material properties, dimensions, and the accuracy of design equations are considered to develop the resistance models obtained by Monte Carlo simulations. The reliability analysis is performed to determine the strength reduction factors. The calculated values of strength reduction factors are proposed for each of the considered efficiency factors.

Abstract: Sample survey has been conducted to evaluate satisfaction of residents living in prefabricated concrete buildings (dormitories, detached houses, and townhouses) in Thailand. Nine criteria have been determined including moisture protection, noise prevention, safety of structures, thermal prevention, air flow, external appearance, interior, facility, and overall satisfaction. The t-test indicates that the satisfaction score mean between males and females for each criterion is not significantly different. The Levenes test shows that our survey data do not follow homogeneity of variance assumption for ANOVA F-test for most criteria, except for airflows and overall satisfaction criteria. Welch and Brown-Forsythe tests are then used under non-homogeneity of variances. The tests reveal that all criteria show a significant difference among habitats groups, but not for the thermal prevention criterion. Some multiple comparisons also show many pairs of significant mean difference among habitat groups.