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Structural Strength in Construction

Superstructure System

Seismic Hazard Potential

Structural Study

super-structure systems

tolerable vertical angular deflec -tion/ span length ratio: Δ/t


Seismic Hazard Potential shall be defined as High, Moderate, or low based upon the 10/50 SS and the 10/50 S1 spectral response accelerations adjusted to reflect site class effects, and utilizing the following relationships:

The structural construction documents must include the following:


1/600 to 1/1000

precast concrete block, unreinforced brick, masonery or plaster walls; slab ongrade

High Seismic Hazard Potential:

(10/50) SMS >= 0.50g and (10/50) SM1 >= 0.20g

1. Complete dimensional information as required to design the system or component part


1/360 to 1/600

reinforced masonry or brick reinforced with horizontal and vertical tie bars or bands made of steel bars of reinforced concrete beams vertical reinforcement located on sides of doors and windows; slab on grade isolated from wall

Moderate Seismic Hazard Potential:

0.167 <= (10/50) SMS < 0.50g or

0.067 <= (10/50) SM1 < 0.20g

2. The nature, location, and magnitude of all design loads to be imposed on the structure


1/50 to 1/360

steel,wood framing, brick veneer with articulation joints,metal, vinyl, or wood panels, gypsum board on metal or wood studs, vertically oriented construction joints, strip windows or metal panels separating rigid wall sections with 8 meters spacing or less to allow differential movement, all water pipes and drains into structure with flexible joints, suspended floor or slab on grade isolated from walls (heaving and cracking of slab on grade probable and accounted in design)

Low Seismic Hazard Potential:

(10/50) SMS < 0.167g and

(10/50) SM1 < 0.067g

3. All design criteria for both the overall structure and the system or component part to be designed by the delegated engineer


1/150 to 1/360

walls or rectangular sections heave as a unit (modular construction), joints a 8 m spacing or less between units and in walls, suspended floor or slab on grade isolated from walls (probable cracking of slab on grades), all water pipes and drains equipped with flexible joints, construction joints in reinforced and stiffened slabs at 50 m spacing or less and cold joints at 22m spacing or less.

Structural remedies to seismic hazard to consider

a Prefabricated wood components b. Cast-in-place post-tensioned concrete structural systems c.Precast, pre-stressed concrete compo nents d. Open web steel joists and joist girders e.Pre-en gineered metal buildings f. Founda -tion systems g.Structural steel connections h. Cold -formed steel joist /stud/truss framing and pre-fabricated components i. Seis -mic anchorage of equipment j. Pro -prietary track for under-hung cranes and monorails

4. All serviceability limit states that apply to the system or component part to be designed by the delegated engineer.

Any area underlain argillous rocks, sediments or soils will exhibit some degree of expansiveness. - The degree of expansiveness is a function of the amount of expandable clay minerals present. - Generally the mesozoic and cenozoic rocks and sediment and contain significantly more montmorillonite than the paleozoic (or older rocks). - Area underlain by the rocks or sediments of mixed textural compositions (e.g.: sandy shales or sandy clays) or shales or clays inter-bedded woth other rocks or sediments are considered on the basis of geologic age and the amount of argillous material present. Generally, those areas lying north of the glacial boundary are non expansive due to glacial drift cover. - Soils derived from weathering of igneous and metamorphic rocks are generally non expansive. Climate or other environmental aspects are not considered. Argillaceous rocks or sediments originally composed of expandable clay minerals do not exhibit significant volume change when subjected to tectonic folding,deep burial or metamorphism. Volcanic areas consisting mainly of extruded basalts and kindred rocks may also contain tuffs and volcanic ash deposit that have de-vitrified and altered montmorillonite. Areas along the glaciated boundary may have such a thin cover of drift that the expansive character of the material under the drift may predominate. earthwork materials in the tropics are dominated by three major groups: coral and coralline limestone, residual soils, and rock aggregate. Because of the warm climate, high humidity, and frequent rainfall, earthwork materials in the tropics are usually more weathered and weaker. Residual soils in the tropics are predominantly silty clays and clayey silts. To be technically correct, the tropical residual soils can generally be categorized into three major soil classes: oxisols, andisols, and vertisols. Oxisols are by far the most common residual soils in tropical regions. Oxisols are silty clays with high contents of oxides. They are generally reddish brown to gray in color. The soils are relatively stable, with low to medium expansion potential. With proper moisture conditioning and compaction, oxisols are adequate as subgrades below lightly loaded structures. Andisols and vertisols are suitable for agricultural use but do not have sufficient strength and stability for construction use. Most common rocks found in tropical regions are intrusive rocks such as granite, igneous rocks such as andesite and basalt, and sedimentary rocks such as sandstones and siltstones.

The delegated engineering submittal must include the following:

a. Identification of the project

b. A printed title block bearing the printed name, address, license number of the delegated engineer, and the date of the drawing

c. The seal and signature of the delegated engineer

Typical Factors of Safety Construction Constraint Concern

Retaining Walls: 3; Temporary braced excavations: > 2; Bridges Railway: 4; Highway: 3.5, Buildings Silos, tanks: 2.5; Warehouses: 2.5; Apartments, offices: 3; Light industrial, public: 3.5; Footings: 3; Mats: > 3; Deep Foundations with load tests: 2; Driven piles with wave equation analysis: 2.5; Deep Foundations without load tests: 3; Multilayer soils: 4.

d. Installation or erection drawings, showing full details of materials to be used, including necessary accessories and instructions for construction, component details, and connection details

e. Calculations, showing all loads and other design criteria, and the magnitude and location of loads and reactions on other portions of the structural system

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