Assessment of Rotational Stiffness for Metallic Hinged Base Plates under Axial Loads and Moments

Pinned base plate connections are the most common base connection used in low-rise steel buildings. In this research, an extensive parametric study is performed using the Finite Element (FE) software Abaqus to determine the elastic rotational stiffness, moment resistance, and energy absorption of the pinned base plate connection connected to a reinforced concrete footing and subjected to an eccentric axial load. The developed FE model is validated using experimental results from the literature. Moreover, an intensive parametric study is conducted to understand the behavior of these connections better. The investigated parameters include the base plate thickness, anchor bolt diameter, and arrangement and number of bolts. The most effective parameters that affect the elastic rotational stiffness and moment resistance of pinned base connections are the anchor bolt arrangement and diameter. The maximum increase in the rotational stiffness was 53% for the anchor bolt diameter of 30 mm when the base plate thickness increased from 12 mm to 30 mm. Based on the base plate thickness, the moment resistance is improved by 150–260% when the bolt diameter increases from 12 mm to 30 mm.

Small-scale testing for feasibility of rubblized concrete foundations

<p>Affordable, sustainable housing plays an essential role in providing equal opportunity for individuals within most communities in the United States, (e.g., in the area of eastern Washington State). In particular, a lack of family residences presents a challenge for the City of Spokane, and low-income residents. Moreover, building materials reuse is an important sustainability issue and concrete waste from demolition of residential buildings presents a challenge. This paper presents preliminary results for development of rubblized concrete foundations. Initial tests were conducted on scaled pseudo-soil/concrete materials to observe the relative stiffness of the proposed system for potential use in planning subsequent phases of testing, including full-scale testing. Initial results of this early testing confirms that a reinforced rubblized footing will likely have an overall stiffness (in terms of response to loading) that is measurably less than that of a conventional reinforced concrete footing.</p><p><br clear="none"/></p>

Improvement of Soft Soil by Stone Column Treated with Bentonite

Soft clayey soils cover wide Iraqi areas specially the regions close to rivers and the southern part of this country Heavy weight structures like: highways, dams, multiple story buildings are suffering unacceptable settlement, when constructing on soft soils. The high contamination of water in such soils decrease the effective stress and reduce bearing capacity. The need was appeared to improve such problematic soil by the use of new technique of stone column treated with different percentages of natural bentonite by a series of field tests using full scale concrete footing constructed on soft soil in addition to a laboratory model to investigate settlement with time at constant stress. The soil that used in this study is natural clayey soil, brought from a location south of Diyala governorate, from a farm area. The study includes also: The effect of stone column diameter treated with bentonite on the behavior of footing constructing on soft clayey soil, The effect of stone column length on the behavior of footing on such soils. Results of field and laboratory model tests reviled that the treated model by stone column mixed with 40% bentonite is the ideal one, which reduces the settlement by 55%. In other hand problems of uneven settlements appear when using 60% bentonite as a mix proportion. The Ideal slenderness ratio (Ds/Ls<25%). The effective depth of stone column treated with bentonite is (1/3H).

Particle Swarm Optimization Based Approach for Estimation of Costs and Duration of Construction Projects

Cost and duration estimation is essential for the success of construction projects. The importance of decision making in cost and duration estimation for building design processes points to a need for an estimation tool for both designers and project managers. Particle swarm optimization (PSO), as the tools of soft computing techniques, offer significant potential in this field. This study presents the proposal of an approach to the estimation of construction costs and duration of construction projects, which is based on PSO approach. The general applicability of PSO in the formulated problem with cost and duration estimation is examined. A series of 60 projects collected from constructed government projects were utilized to build the proposed models. Eight input parameters, such as volume of bricks, the volume of concrete, footing type, elevators number, total floors area, area of the ground floor, floors number, and security status are used in building the proposed model. The results displayed that the PSO models can be an alternative approach to evaluate the cost and-or duration of construction projects. The developed model provides high prediction accuracy, with a low mean (0.97 and 0.99) and CoV (10.87% and 4.94%) values. A comparison of the models’ results indicated that predicting with PSO was importantly more precise.

Deterministic and Probabilistic Approaches in the Analysis of the Bearing Capacity of a Bridge Foundation on Undrained Clay Soil

This study aims at evaluating deterministic and probabilistic approaches for an analysis of the bearing capacity of a highway bridge foundation on undrained clay soil. The analysis of a rectangular concrete footing was presented for the ultimate strength limit state of the bearing resistance according to the formulation in ES EN 1991:2015 and ERA-Bridge Design Manual, which are the Ethiopian design codes for foundation structures. In the deterministic analysis, the traditional total safety factor method recommended by the ES EN 1991:2015, ERA and AASHTO LRFD method was implemented. It was assumed that design variables such as the soil parameters and loads would follow normal and lognormal distribution functions. With regard to the probabilistic methods, NESSUS-9.8 software, a statistical computer program, was used for the analysis. Comparisons were made between the results obtained from the traditional deterministic method and the reliability-based design approach. The evaluation asserts that the probabilistic approach is a better tool than the deterministic one for assessing the safety and reliability of geotechnical structures. The probabilistic design method rationally accounts for uncertainties more than the conventional deterministic method does. Thus, the author recommends that the National Design Codes of Ethiopia need to be revised and calibrated based on a reliability design format.