Sp- Structural Design - 01

The design analysis requirement mentioned in the question refers to the distribution of total lateral forces to the various vertical elements of the lateral force resisting system in proportion to their rigidities. This distribution is based on the rigidity of the horizontal bracing system or diaphragm. Shear and moment diagrams are graphical representations that show the distribution of shear and moment forces along a structural element. Therefore, the shear and moment diagram is the correct answer as it provides the necessary information for designing the structural elements to resist lateral forces.

The weight of 1 cubic meter of concrete is 2400 kg. Concrete is a heavy material, and its weight is commonly measured in kilograms. The other options, N (Newtons), KN (Kilonewtons), and lbs (pounds), are not commonly used units for measuring the weight of concrete.

The correct answer is A. Jacking force. According to the NSCP Sec. 5.2.1, the temporary force exerted by a device that introduces tension into pre-stressing tendons is known as the jacking force. This force is applied to the tendons in order to create the necessary tension for pre-stressing.

The minimum thickness of horizontal members (beams) or ribbed one-way slabs, if they are simply-supported, is given by L/16. This means that the thickness of the members should be equal to the span length divided by 16. This is a standard requirement for ensuring the structural integrity and strength of the members under the given conditions of support.

The correct answer is B. 40 mm. According to NSCP Sec. 6.3.10, the concrete cover of pipes, conduits, and fittings should be at least 40 mm for concrete exposed to earth or weather. For concrete not exposed to weather or in contact with the ground, the minimum concrete cover should be 20 mm.

The maximum spacing of vertical reinforcement (flexural reinforcement) of a wall is determined by the NSCP Sec. 5.7.6.5 and NSCP Sec. 5.14.3.5. According to these sections, the maximum spacing should be 3 times the wall thickness, but it should not exceed 18 inches. This means that the spacing between the vertical reinforcement bars should not be more than 3 times the wall thickness, and it should also not exceed 18 inches in any case. Therefore, option A is the correct answer.

A diaphragm is a horizontal or nearly horizontal system that transmits lateral forces to the vertical resisting elements. It includes horizontal bracing systems and helps to distribute the lateral loads evenly across the structure. This explanation is supported by the reference to NSCP Sec. 2.2.2.

The required strength (U) to resist dead load D and live load L shall be at least equal to 1.4 times the dead load (DL) plus 1.7 times the live load (LL). This is based on the NSCP (National Structural Code of the Philippines) Section 5.9.2. The code specifies the minimum strength requirements for structures to safely withstand the combined effects of dead and live loads. By multiplying the dead load by 1.4 and the live load by 1.7, the resulting strength ensures an adequate safety factor for the structure.

The correct answer is A. Bearing wall system. This is because a bearing wall system refers to a structural system where the vertical load is carried by walls, rather than a complete vertical load carrying space frame. In this system, the walls provide support for gravity loads, while resistance to lateral loads is provided by shear walls or braced frames. This is in accordance with the NSCP Sec. 2.2.2 and NSCP Sec. 2.2.4.6.1.

The correct answer is A. The reduced modulus of elasticity is used in concrete design to account for the effect of creep on deflections due to sustained loadings. Creep is the gradual deformation of concrete under a constant load over time. This deformation can cause additional deflections in the structure, which need to be considered in the design process. By using the reduced modulus of elasticity, engineers can accurately predict and account for these deflections to ensure the safety and stability of the structure.

A wall footing is a type of continuous spread footing that supports the weight of the wall, as well as the weight of the footing itself. It is designed to distribute the vertical load evenly across the foundation, providing stability and preventing settlement. This type of footing is commonly used for load-bearing walls in buildings and structures.

A diaphragm strut is a structural member that takes axial tension or compression in a horizontal bracing system. It is parallel to the applied load and is responsible for collecting and transferring shear to the vertical resisting elements or distributing loads within the horizontal bracing system. This explanation aligns with the definition provided in the NSCP Sec. 2.2.2.

The weight of a steel bar can be calculated using the formula: weight = volume × density. The volume of the steel bar can be calculated using the formula for the volume of a cylinder: volume = πr²h, where r is the radius and h is the height. The given diameter of the steel bar is 38 mm, so the radius is 19 mm. Converting the radius to meters, we get 0.019 m. The height of the steel bar is given as 1 meter. The density of steel is approximately 7850 kg/m³. Plugging in these values into the formula, we get: volume = π × (0.019)² × 1 = 0.001138 m³. Multiplying the volume by the density, we get the weight: weight = 0.001138 m³ × 7850 kg/m³ = 8.9257 kg. Rounding to three decimal places, the weight is approximately 9.564 kilograms.

The correct answer is A. Orthogonal effect. This term refers to the effect on the structure caused by extreme lateral (earthquake) motions acting in directions other than parallel to the direction of resistance being considered. In other words, it describes the impact of seismic forces that act perpendicular or at an angle to the primary direction of resistance in a structure. The term "orthogonal" means perpendicular or at right angles, which accurately describes the effect being discussed.

The slenderness ratio of steel compression members is a measure of their stability under axial compression. It takes into account the effect of the degree of restraint at the top and bottom supports. The K-factors, also known as effective length factors, are used to adjust the effective length of the member based on the end conditions. Different end conditions can result in different buckling behavior, and the K-factors help to account for this. Therefore, the K-factors are the correct answer to this question.

The strength reduction factor for the design strength of a member with axial tension and axial tension with flexure is 0.90. This means that the design strength of the member is reduced by a factor of 0.90 to account for the combined effects of axial tension and flexure. The reduction factor is used to ensure that the member can safely withstand the applied loads and meet the required safety factor.

The correct answer is B. A,B,D. This means that statements A, B, and D are true. Statement A states that the maximum allowable stress in shear for A36 steel is 14.5 ksi, which is true. Statement B states that the maximum allowable stress for bending is 24 ksi, which is also true. Statement D states that the modulus of elasticity for A36 steel is 29,000 ksi, which is true as well. Therefore, the correct answer is B. A,B,D.

The correct answer is C. Post-tensioned concrete. In post-tensioned concrete, the concrete members are loaded with tension after the concrete has been placed and hardened. This is achieved by inserting high-strength steel cables or tendons into the concrete and then applying tension to them. This process helps to counteract the internal stresses caused by live and dead loads, allowing the concrete to be held in compression.

Creep refers to the tendency of materials to move or deform over time under a constant load. The amount of movement can vary depending on the material, with the highly stressed area experiencing the most movement. This movement causes stresses to be redistributed. Therefore, creep is the correct answer to describe this phenomenon.

The strength reduction for shear and torsion is 0.85. This means that the actual strength of a structural member subjected to shear or torsion is reduced by a factor of 0.85 in design calculations. This reduction factor accounts for uncertainties in material properties, construction quality, and loadings, ensuring a safe and reliable design.

The weight of a steel bar can be calculated using the formula: weight = volume x density. The volume of a cylindrical bar can be calculated using the formula: volume = πr^2h, where r is the radius and h is the height. Given that the diameter is 34 mm, the radius is 17 mm (34/2). Converting the radius to meters (0.017 m) and the height to meters (9 m), we can calculate the volume. The density of steel is typically around 7850 kg/m^3. Plugging in the values, we can calculate the weight to be approximately 56.865 kilograms.

The load factor (strength reduction factor) for a structural member subjected to axial compression, axial compression with flexural stress, and lateral ties as reinforcement is 0.70. This means that the ultimate strength of the member is reduced by a factor of 0.70 when determining its design capacity. The load factor takes into account the uncertainties and variabilities in material properties, construction methods, and other factors that can affect the structural performance. A load factor of 0.70 provides a safety margin to ensure that the member can safely resist the applied loads.

The correct answer is C. 54.488 kilograms. This answer is based on the information provided in NSCP Sec. 5.2.1, which states that the type of concrete that weighs 1900 kg/m3 when air-dried is 54.488 kilograms.