Twin lintel belt in steel for seismic strengthening of brick masonry buildings

A single-room,single-storey full-scale brick masonry building with precast RC roofing system was tested thrice under displacement controlled lateral cyclic loading,to assess the effectiveness of the basic repair and seismic strengthening techniques.Initially,the virgin building specimen was loaded laterally to f^tilure.In the second stage,the damaged building was repaired by stitching across the cracks,and tested under the same lateral loading.In the third stage,the twice-damaged structure was repaired once more by stitching and strengthened by twin lintel belt in steel and vertical comer reinforcement, and re-tested.The building strengthened by twin lintel belt in steel showed about 28% higher strength under lateral loading than the virgin building.

有机复合客土基材接触面剪切力学特性试验

为研究高分子材料和接触面粗糙度对土-岩接触面剪切力学性能的影响,设计预制混凝土模块作为岩面相似材料,开展一系列改进型直剪试验,分析高分子材料和接触面粗糙度的影响规律,并结合扫描电镜试验深入揭示高分子材料的改良机制。结果表明,高分子材料主要通过提高黏聚力极大地改善基材土和接触面的剪切力学性能,掺量2%的基材试样黏聚力达41.76 kPa,提高了约3倍。掺量2%的不同接触面试样黏聚力提高了2~7倍;增大接触面粗糙度主要通过提高黏聚力增强接触面剪切力学性能,粗糙度为6.5 mm的不同接触面间黏聚力提升幅度为12.27~23.77 kPa,提高了0.4~3.9倍;对于平坦接触面和粗糙接触面,高分子材料对剪切性能的强化表现为两种不同模式;高分子材料与接触面粗糙度对接触面的剪切性能具有协同强化效应。

GIS Based Spatial Data Analysis for Landslide Susceptibility Mapping

Landslide susceptibility map delineates the potential zones for landslides occurrence. The paper presents a statistical approach through spatial data analysis in GIS for landslide susceptibility mapping in parts of Sikkim Himalaya. Six important causative factors for landslide occurrences were selected and corresponding thematic data layers were prepared in GIS. Topographic maps,satellite image,field data and published maps constitute the input data for thematic layer preparation. Numerical weights for different categories of these factors were determined based on a statistical approach and the weighted thematic layers were integrated in GIS environment to generate the landslide susceptibility map of the area. The landslide susceptibility map classifies the area into five different landslide susceptible zones i.e.,very high,high,moderate,low and very low. This map was validated using the existing landslide distribution in the area.

Landslide Hazard Zonation Mapping and Comparative Analysis of Hazard Zonation Maps

Landslide hazard zonation mapping at regional level of a large area provides a broad trend of landslide potential zones. A macro level landslide hazard zonation for a small area may provide a better insight into the landslide hazards. The main objective of the present work was to carry out macro landslide hazard zonation mapping on 1:50,000 scale in an area where regional level zonation mapping was conducted earlier. In the previous work the regional landslide hazard zonation maps of Srinagar-Rudraprayag area of Garhwal Himalaya in the state of Uttarakhand were prepared using subjective and objective approaches. In the present work the landslide hazard zonation mapping at macro level was carried out in a small area using a Landslide Hazard Evaluation Factor rating scheme. The hazard zonation map produced by using this technique classifies the area into relative hazard classes in which the high hazard zones well correspond with high frequency of landslides. The results of this map when compared with the regional zonation maps prepared earlier show that application of the present technique identified more details of the hazard zones, which are broadly shown in the earlier zonation maps.

Environmental protection and ecology-Indian experience

An attempt has been made in this paper to highlight some of environmental problems and suggest possible solutions for planning water resources development projects.

Strengthening of RC T-beams with Shear Deficiencies Using GFRP Strips

The shear performance, modes of failure, and strain analysis of simply supported reinforced concrete （RC） T-beams, externally strengthened in shear using epoxy bonded glass fiber reinforced polymer （GFRP） strips are focused in the present paper. Six RC T-beams of 2.5 m span without shear reinforcement are cast. Three beams are used as control specimens and rest three beams are strengthened in shear with GFRP strips in U-shape, side bonded at 45° and 90° to the longitudinal axis of the beam. All the beams are tested in a Universal Testing Machine. The test results demonstrate the feasibility of using an externally applied, epoxy-bonded GFRP strips to restore or increase the shear strength of RC T-beams. It is also observed that the RC T-beams strengthened by diagonal side strips outperformed those strengthened with vertical side strips.

Artificial Neural Network （ANN） and Regression Tree （CART） applications for the indirect estimation of unsaturated soil shear strength parameters

The shear strength parameters of soil （cohesion and angle of internal friction） are quite essential in solving many civil engineering problems. In order to determine these parameters, laboratory tests are used. The main objective of this work is to evaluate the potential of Artificial Neural Network （ANN） and Regression Tree （CART） techniques for the indirect estimation of these parameters. Four different models, considering different combinations of 6 inputs, such as gravel %, sand %, silt %, clay %, dry density, and plasticity index, were investigated to evaluate the degree of their effects on the prediction of shear parameters. A performance evaluation was carried out using Correlation Coefficient and Root Mean Squared Error measures. It was observed that for the prediction of friction angle, the performance of both the techniques is about the same. However, for the prediction of cohesion, the ANN technique performs better than the CART technique. It was further observed that the model considering all of the 6 input soil parameters is the most appropriate model for the prediction of shear parameters. Also, connection weight and bias analyses of the best neural network （i.e., 6/2/2） were attempted using Connec- tion Weight, Garson, and proposed Weight-bias approaches to characterize the influence of input variables on shear strength parameters. It was observed that the Connection Weight Approach provides the best overall methodology for accurately quantifying variable importance, and should be favored over the other approaches examined in this study.

Quantification of hydration products in cementitious materials incorporating silica nanoparticles

In the present work, silica nanoparticles （30-70nm） were supplemented into cement paste to study their influence on degree of hydration, porosity and formation of different type of calcium-silicate-hydrate （C-S-H） gel. As the hydration time proceeds, the degree of hydration reach to 76% in nano-modified cement paste whereas plain cement achieve up to 63% at 28 days. An influence of degree of hydration on the porosity was also determined. In plain cement paste, the capillary porosity at lhr is ~48%, whereas in silica nanoparticles added cement is -35 % only, it revealed that silica nanoparticles refines the pore structure due to accelerated hydration mechanism leading to denser microstructure. Similarly, increasing gel porosity reveals the formation of more C-S-H gel. Furthermore, C-S-H gel of different CaJSi ratio in hydrated cement paste was quantified using X-ray diffractometer and thermogravimetry. The results show that in presence of silica nanoparticles, -24% C-S-H （Ca/Si 〈 1.0） forms, leading to the formation ofpolymerised and compact C-S-H. In case of plain cement this type of C-S-H was completely absent at 28 days. These studies reveal that the hydration mechanism of the cement can be tuned with the incorporation of silica nanoparticles and thus, producing more durable cementitious materials.

Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane loading

This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls.The tested wall exhibited flexural cracks,owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill.The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift.Numerical analysis was conducted to validate experimental findings,which complied with each other.The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system.The in-plane capacity of walls reduced,while deformation characteristics were unaffected by the increase in backfill density.An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift.Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density,which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear.