ANALYSIS OF LATERITE SOIL WITH PORTLAND CEMENT MIXED VARIATIONS AND THE EFFECT ON THE CBR UNSOAKED

Ketapang and Kayong Utara Regency have road construction that often suffers damage before the planned life age caused by the behavior of expansive clay. The subgrade is a fundamental structure in building road construction because the subgrade will support traffic loads or construction loads. The strength and durability of the pavement structure road will depend on the properties and bearing capacity of the subgrade. Practically soil stabilization is a reinforcement engineering against foundation or subgrade by using mixed materials. Therefore, different soil improvement variations are needed. Based on the test result, the CBR value of Sukadana initially gets a 2.95% point. The CBR value for the 6% and 10 % mixture, respectively, gets 17.14% and 25.02%. The CBR value of Sungai Melayu Rayak originally get 4.65% point. Then, for the 6% and 10% mixture, the CBR values increased by 13.78% and 18%. The value of the bearing capacity of the highway soil construction can be know from the results of CBR testing on each variation. The CBR also can measure the strength of the soil. The addition of cement to the earth tends to increase the bearing capacity of the ground. It is because cement can function as a binder between soil particles with chemical compounds contained in cement.

Evaluating Biosedimentation for Strength Improvement in Acidic Soil

Marine clay soils are problematic soils in the construction industry when they are subjected to construction loads. When these soils are loaded, they lose their structure. This leads to the soil being unable to withstand loads of any magnitude without exhibiting significant, permanent deformations. In order to stabilize the marine soil, new methods for soil improvement were built upon biogrouting by incorporating physical, biological and chemical treatments into the soil. However, the biggest challenge of this method is the bacteria migration through the soil medium. To overcome this issue, the electrokinetic phenomenon can be utilized alongside biogrouting to prevent the bacteria migration. In this regard, the present study applied electrobiogrouting stabilization to investigate the improvement of acidic marine clay soil with a pH of 3.69. To accomplish this, two large-scale physical models with dimensions of 500 × 300 × 1200 mm were fabricated to examine the influence of two different treated distances between the inlet and outlet—450 mm (D45) and 600 mm (D60)—on the stability of the treated soil. It was observed that the shear strength of the treated soil improved significantly. The shear strength at the D45 treated distance increased from 3.65 kPa (untreated soil) to 28.14 kPa (treated soil). However, the strength increased by increasing the treated distance. In addition, compressibility and soil electrical conductivity were reduced significantly, and the Atterberg limits were significantly enhanced from OH to OL. The reasons for the enhancement of treated soil were the formation of CaCO3, which filled the soil voids, and that the water content was reduced. To address issues with marine clay soil, this study aims to minimize the high cost of a special foundation system and the use of non-environmentally friendly materials such as calcium-based binders, aside from the reduction of deformations caused by loading. The findings of this study can be used for acidic soils and the improvement of soil’s geotechnical behavior in general.

Parametric study of curved steel I-girder bridges at construction phase.

The desire to conform to the existing terrain has largely increased the use of curved bridges for complex interchanges. Bridge curvature produces warping moments (lateral bending moments) in girder flanges under truck loading conditions and even during the construction phase. These warping moments increase girder flexural stresses at construction phase in case of un-shored construction. An extensive parametric study was conducted, using the finite-element analysis software "SAP2000", to examine the key parameters affecting warping stresses in curved girder bridges under construction loads. A strengthening technique "torsion box" at the girder supports was proposed and examined with respect to girder warping, flexural stresses and support reactions. The key parameters considered in this study included number of girders, girder spacing, number of cross bracing intervals, degree of curvature and girder span length. Based on this study empirical expressions for moment and shear distribution factors for the curved girder were developed.

Parametric study of curved steel I-girder bridges at construction phase.

The desire to conform to the existing terrain has largely increased the use of curved bridges for complex interchanges. Bridge curvature produces warping moments (lateral bending moments) in girder flanges under truck loading conditions and even during the construction phase. These warping moments increase girder flexural stresses at construction phase in case of un-shored construction. An extensive parametric study was conducted, using the finite-element analysis software "SAP2000", to examine the key parameters affecting warping stresses in curved girder bridges under construction loads. A strengthening technique "torsion box" at the girder supports was proposed and examined with respect to girder warping, flexural stresses and support reactions. The key parameters considered in this study included number of girders, girder spacing, number of cross bracing intervals, degree of curvature and girder span length. Based on this study empirical expressions for moment and shear distribution factors for the curved girder were developed.

EFFECT OF WELDING HEAT INPUT ON THE CORROSION RATE OF CARBON STEEL MMA WELDING

Steel is one of materials which often used on steel construction, bridge construction, and high rise building construction. Construction using welding joint is expected able to withstand construction loads for a long time. After a while weldment will be exposed to corrosion that will be construction failure in turn. One of the most important parameter in welding is heat input, however it hasn’t obtain correlation between heat input and corrosion rate on MMA (Manual Metal Arch) weldment on mild steel. This paper aims to obtain correlation between heat input and corrosion rate of low carbon steel with MMA welding. The result was show that corrosion rate tend to decrease with adding of duration, where higher corrosion rate at heat input 0,8108 kJ/mm was 68,68 gm/m2 hr at duration 5 hour.

Development of Multi-Tee-Type Precast Concrete Slabs with Insulating Materials for Structural Safety at the Construction Stage

Multi-tee-type precast concrete (PC) slab systems are widely used for the construction of modular high-load long-span buildings. However, the structural safety of the dapped end is uncertain, owing to the unanchored shear reinforcement at the construction stage. This study proposes the use of clip-type shear reinforcement at the dapped ends of multi-tee PC slabs to secure their structural performance at the construction stage. To investigate the performance of this approach, a monotonic loading test was performed on simply supported PC slabs, considering structural safety at the construction stage. The reinforcement details of the PC slab’s dapped end (with existing Z-type or proposed clip-type shear reinforcement) and the shear-to-span ratio (12.8 or 6.4) were considered as test parameters. The load–deflection relationship, failure mode, strength ratios to the predicted strength, and shear reinforcement strains were analyzed. The results showed that the tested flexural strength ratio of the PC slabs at the construction stage to the design flexural strength was 1.20–1.40. The enclosed shape and diagonal arrangement of the clip-type shear reinforcement enabled sufficient anchorage performance at the dapped end, indicating that clip-type shear reinforcement can be viable for use at the dapped ends of PC slabs under construction loads.

Analysis of structural masonry buildings taking into account the construction sequence loads and soil-structure interaction

abstract: The present study assesses conventionally used design standards, analyzing the effects caused by the construction loads, that is, a gradual increase in load and stiffness during construction, and soil-structure interaction (SSI), with soil represented by linear springs, in a structural masonry building over a support structure of reinforced concrete. The equivalent frame model, developed by Nascimento Neto, was used to simulate the support structure and the first masonry floor, and a specific three-dimensional frame model to simulate the other floors. Four analysis models were applied to assess stress distribution at the base of the walls, and the stresses and displacements of the support structure. The results show that introducing SSI and the construction loads causes relief or the possible need to reinforce elements designed in Ultimate Limit State (ULS) and Serviceability Limit State (SLS), as well as uniform settlement.